Electronics in Motion and Conversion September 2012 SECURING YOUR PROJECTS

ISSN: 1863-5598 ZKZ 64717 09-12

Welcome to the House of Competence.

GvA is your expert in individual problem solutions for all sectors of power electronics – state of the art know how and profound experience as an engineering service provider, manufacturer and distributor. Consulting – Design & Development – Production – Distribution

GvA Leistungselektronik GmbH | Boehringer Straße 10 - 12 | D-68307 Mannheim Tel +49 (0) 621/7 89 92-0 | www.gva-leistungselektronik.de | [email protected] CONTENT

Viewpoint It’s Show Time around the world! ...... 4 Events ...... 6 Superior Solutions for News ...... 6-14 Blue Product of the Month Industrial. Reduction of Extreme High Inrush-Currents Thomatronik ...... 16 Green Product of the Month Power Solutions for More Efficiency Vicor by Marisa Robles Consée, Corresponding Editor; Bodos Power Systems ...... 18-19 Editorial Report Back to Normal Soon, Chipmaker Renesas Electronics By Marisa Robles Consée, Corresponding Editor; BPSystems . . . . 20-21 Market Electronics Industry Digest By Aubrey Dunford, Europartners ...... 22 Market Darnell Report By Jeff Shepard, President Darnell Group ...... 24-25 Automotive Power eCarTec: Join the eMobility Revolution! By Marisa Robles Consée, Corresponding Editor; BPSystems . . . 26-27 Coverstory SKiN Technology for Ultra Compact Power Modules ByThomas Graßhoff, Semikron International GmbH, Nuernberg, Germany ...... 28-31 Automotive Power Solutions for On-Board Chargers, All Charged Up By Cem Som, Development Transformers, EPCOS ...... 32-33 IGBT Modules Low Inductive Inverter Design Using a New Power Module Concept By Xi Zhang, Daniel Domes, Reinhold Bayerer and Alexander Herbrandt, Infineon Technologies AG ...... 34-35 Thermal Management Aluminum electro- Common-mode Energy Efficiency and Design Freedom of Busbars lytic capacitors for chokes for high By Koen Hollevoet, Business Opportunity Analyst, Rogers . . . 36-37 high ripple currents currents DC/DC Converter High Speed, Two Quadrant DC/DC Power Supply PFC products for Varistors and surge By Milan Marjanovic, Texas Instruments ...... 38-41 energy saving and arresters for over- Power Supply power quality voltage protection Total Solution for Energy Efficient Home Appliance Power Supply By Won-Seok Kang, Senior Application Engineer, EMC and sine-wave Power electronic Power Conversion Korea, Fairchild Semiconductor ...... 42-43 filters for currents capacitors with up to 8 kA high reliability Technology eGaN® FET Safe Operating Area By John Worman and Yanping Ma, X and Y capacitors High-current chokes Efficient Power Conversion Corporation ...... 44-46 for EMI suppression for power supplies Transformers Optimizing Three-Phase Planar Transformer Construction By R. Prieto, R. Asensi, O. García, J. A. Cobos, Universidad Politécnica de Madrid, Centro de Electrónica Industrial (CEI), Madrid and F. D. Gerez Premo Group. Barcelona, Spain ...... 48-51 Diodes and Rectifiers High Current Rectifier Diodes for Welding Applications MLCC mega caps SMT power By Björn Backlund ABB Switzerland Ltd, Semiconductors and with high ripple inductors with Ladislav Radvan ABB s.r.o. Semiconductors ...... 52-54 current capability high reliability DC/DC Converter The Half-Bridge Circuit Revealed Rare earth and Large ferrite By Tom Ribarich, International Rectifier, Director, Lighting Systems ferrite magnets cores and Applications ...... 56-58 New Products www.bodospower.com www.tdk.eu · www.epcos.com The Gallery

2 Bodo´s Power Systems® September 2012 www.bodospower.com Taming the Beast

New 3.3kV SCALE-2 IGBT Driver Core Features

The new dual-channel IGBT driver core 2SC0535T for Highly integrated dual channel IGBT driver high voltage IGBT modules eases the design of high 2-level and multilevel topologies power inverters. Using this highly integrated device !!""# Operating temperature -55..+85°C design cycle and reduces the engineering risk. Beside <100ns delay time the cost advantage resulting from the SCALE-2 ASIC ±4ns jitter - ±35A gate current Isolated DC/DC converter interfaces. The driver is equipped with a transformer $%&' technology to operate from -55°..+85°C with its full Regulated gate-emitter voltage performance and no derating. All important traction Supply under-voltage lockout 2SC0535T2A0-33 Short-circuit protection ( Meets EN50124 and IEC60077 UL compliant SAMPLES AVAILABLE! 75 USD @ 1000 pieces

CT-Concept Technologie AG, Renferstrasse 15, CH-2504 Biel, Switzerland, Phone +41-32-344 47 47 www.IGBT-Driver.com VIEWPOINT

It’s Show Time A Media Katzbek 17a D-24235 Laboe, Germany around the world! Phone: +49 4343 42 17 90 Fax: +49 4343 42 17 89 Alas, the strawberry season is over but [email protected] homemade strawberry jam provides a treat www.bodospower.com at breakfast all year long and using a 3:1 Publishing Editor fruit to sugar ratio in the process is good for Bodo Arlt, Dipl.-Ing. any diet – including mine. Soon we will be [email protected] harvesting apples and getting ready for Thanksgiving. Time has flown by and Corresponding Editor Santa’s probably already making his prepa- Marisa Robles Consée, rations. [email protected]

Creative Direction & Production The last quarter of the year will be a busy Repro Studio Peschke time for us all. The most popular electronic [email protected] show this fall will be the Electronica in November. And in advance of the Electroni- ca we have a busy September and October. tors. Finally, Premo together with the Univer- Free Subscription to qualified readers EPE in Novi Sad, Serbia starts the race, fol- sity of Madrid has presented a three-phase lowed by the world’s best wind power event transformer with flat conductor layers for Bodo´s Power Systems HusumWindEnergy in Germany. The next high power. is available for the following subscription charges: leg of events include the Thermal Manage- Annual charge (12 issues) is 150 € ment show in Denver, the LED in Bregenz, Besides the high power elements, we have world wide Austria on the Bodensee Lake and EU more great technical information in this, the Single issue is 18 € PVSEC, the photovoltaic production confer- September issue. Fairchild looks at energy [email protected] ence and show in Frankfurt - and that’s just efficient home appliance power supplies, an circulation print run September - October will continue at the important area of volume applications that 20000 same pace! has a major impact on power consumption. Texas Instruments investigates DC/DC con- My partners have upgraded the Chinese verter efficiency. A lot of great technical con- Printing by: web-site of Bodo’s Power China with tent to digest for experts worldwide. Central-Druck Trost GmbH & Co enhanced capabilities such as a video chan- Heusenstamm, Germany nel, an industry company catalogue and The PowerGuru internet platform is growing enhanced user interaction functionality. Reg- with my past and current articles up for A Media and Bodos Power Systems istered users can also now create their own search and retrieval. Cooperating with Pow- assume and hereby disclaim any blog on the site. Check out what is new in erGuru has been a great step forward - have liability to any person for any loss or China at www.bodospowerchina.com. a look at www.powerguru.org. PowerGuru damage by errors or omissions in the has finalized the conversion of all the maga- material contained herein regardless Technology is moving fast and we always zine articles back to 2006. of whether such errors result from negligence accident or any other look forward to improvements with new cause whatsoever. materials, both in semiconductors and pas- Communication is the only way to progress. sive components, the bread and butter to get We delivered twelve issues last year and will Read online and search for key subjects systems running. This month’s cover story continue each month, on time, every time. from all articles in Bodo’s Power Systems covers improved capability using the “skin So far this year we have published 668 by going to Powerguru: technology” developed by Semikron. This pages and, more importantly, 113 technical technology targets e-mobility and renewable articles. As a media partner, Bodo’s Power energy systems including solar and wind Systems is internationally positioned. If you power. Rogers has contributed an interest- speak the language, or just want to take to ing article to this edition on Busbars and look, don’t miss our Chinese version: their importance in power inverter systems www.bodospowerchina.com. where they are responsible for current distribution and thermal management. Low induc- My Green Power Tip for September: tance is another issue in inverter design and Leave a few apples on the trees and berries is explained in detail in an article provided by on the bushes for the birds to help them sur- Infineon, while EPC (Electronic Power Con- vive the winter. They’ll sing their songs for version) has provided insights to the subject you in your garden to say “thanks!” of GaN and SOA (Safe Operating Area). Here we see that the device temperature is Best regards, always a physical limitation for semiconduc-

4 Bodo´s Power Systems® September 2012 www.bodospower.com Dawn of a new intelligence for current measurement

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www.lem.com At the heart of power electronics. NEWS

Events Appointment of General Manager Semiconductors EPE PEMC, ABB Switzerland as project manager "Europe for Europe" as Novi Sad, Serbia, September 4th-6th Ltd is pleased to part of ABB’s strategy 2015+. http://epe-pemc2012.com/category/news/ announce that Dr. Before joining the Semiconductors unit, Jür- Jürgen Bernauer gen Bernauer was ABB’s General Manager Power Electronics South America, Sao Paulo, Brasilia, September 11-13 was appointed for Gas-Insulated Substations in ABB www.mesago-online.de/de/PESA/home.htm General Manager Switzerland. Semiconductors, ABB would like to thank Mr. Eschermann for Battery Power 2012, Denver Colorado, September 18th -19th effective July 1st, his valuable contribution to ABB’s semicon- www.batterypoweronline.com/ 2012. He succeeds ductor business and wish Jürgen Bernauer a Bernhard Escher- great start and much success in his new job Thermal Management 2012, mann who has been at ABB Semiconductors at ABB Semiconductors. Denver Colorado, September 18th -19th for the past 5 ½ years. www.thermalnews.com/conferences/ www.abb.com/semiconductors Mr. Eschermann has assumed his new role Husum WindEnergy, Husum, Germany, September 18th-22nd www.husumwindenergy.com Innotrans, ECPE Calendar of Events 2012 Berlin, Germany, September 18th-23rd ECPE Workshop www.innotrans.com 'Integrated Power Boards' 21 - 22 November 2012, Rijswijk/Delft, Power Fortronic, Bologna, Italy September 20th Netherlands www.powerfortronic.it Chairmen: Prof. J. A. Ferreira, TU Delft, Dr. J. Popovic-Gerber, TU Delft and Prof. E. EMA Elektromobilausstellung, ECPE Tutorial 'EMC in Power Electronics' Nuremberg Germany, September 21st-22nd Wolfgang, ECPE 27 - 28 November 2012, Aalborg, Denmark www.ema-n.de More upcoming ECPE Events: Chairmen: Dr. E. Hoene (Fraunhofer IZM) LED Professional, ECPE Tutorial 'Power Electronics Packaging' and Prof. J.-L. Schanen (G2ELab) Bregenz Austria, September 25th -27th www.led-professional.com (Programme available soon) ECPE Tutorial 11 - 12 October 2012, Birmingham, UK 'Design of Magnetic Components' EU PVSEC, Chairmen: Dr. U. Scheuermann (Semikron) Frankfurt Germany, September 24th – 28th October 2012, Munich, Germany and Prof. C. M. Johnson (University of www.photovoltaic-conference.com/ Course Instructor: Bruce Carsten Nottingham) Intelec, ECPE Workshop Scotsdale AZ, USA ECPE Tutorial 'Thermal Engineering of 'Power Seminconductor Robustness September 30th – October 4th Power Electronic Systems - Part II – What kills Power Devices?' www.intelec.org (thermal management and reliability)' 12 - 13 December 2012, Munich, Germany Distribution Automation Europe, 18 - 19 October 2012, Nuremberg, Germany Techn. Chairmen: Prof. D. Silber (ECPE) London UK, October 8th -9th Chairmen: Dr. M. Maerz (Fraunhofer IISB) and Prof. L. Lorenz (ECPE) www.smi-online.co.uk and Dr. U. Scheuermann (Semikron) /distributionautomation38.asp ECPE Tutorial The ECPE Calendar of Events 2012 with all SEMICON Europa, 'Reliability of Power Electronic Systems' ECPE Events is available on the ECPE website Dresden Germany, October 9th -11th 7 - 8 November 2012, Graz, Austria www.semiconeuropa.org/ www.ecpe.org Chairmen: Prof. E. Wolfgang (ECPE) Electric Drives E / DPC 2012, Nuremberg, Germany, October 16th-17th www.edpc-expo.com Meeting Point for Science and Industry ESARS 2012, The Power Electronics South America con- mal management and packaging, with a par- Bologna, Italy, October 16th -20th ference and exhibition from 11 - 13 Septem- ticular focus on energy efficient systems. www.esars.org ber 2012 in Sao Paulo, Brazil offer a com- The exhibition and program offer opportuni- e-car-tech, prehensive seminar and conference program ties for networking Munich Germany, October 23 th-25th on the current trends and applications in Many prominent companies will be showcas- www.ecartec.de power electronics. ing their expertise at the accompanying exhi- electronica, As well as three keynote speeches and bition, whilst the conference will bring togeth- Munich Germany, November 13th-16th more than 70 presentations, the program er exhibitors and highly qualified delegates www.electronica.de includes six half-day seminars led by indus- and visitors. Entry to the conference and the SPS/IPC/DRIVES, try experts. As part of the conference pro- poster presentations is free for conference Nuremberg Germany, November 27th-29th gram, speakers from industry and research delegates, visitors and exhibitors. The early www.mesago.de/de/SPS will demonstrate how research results and registration fee is available until 31 July. Power Electronics Moscow, developments can be applied within industry. November 27th to 29th The main themes are power semiconduc- www.mesago.de/en/pesa/htm power.primexpo.com/ tors, power converters, energy storage, ther-

6 Bodo´s Power Systems® September 2012 www.bodospower.com NEWS

Global Distribution Agreement Mouser Electronics, Inc., regarded “Mouser has decades of experience as a trusted, authorized distribu- as a top design engineering resource tor of leading edge components for design engineers,” says David and global distributor for semicon- Loftus, Senior Vice president of Worldwide Sales and Corporate Mar- ductors and electronic components, keting at Intersil. “This global agreement will allow us to expand our today announced a new worldwide customer base with Mouser’s best-in-class service and streamlined distribution agreement with Intersil logistics.” Corporation, a world leader in the design and manufacture of high-per- With its broad product line and unsurpassed customer service, formance analog, mixed signal and Mouser caters to design engineers and buyers by delivering What’s power management semiconductors. Next in advanced technologies. Mouser offers customers 19 global support locations and the latest, most technologically advanced com- For design engineers across the ponents for their newest design projects. Mouser Electronics’ website globe, Mouser’s agreement with is updated daily and searches more than 8.9 million products to Intersil means faster access to Inter- locate over 3 million orderable part numbers available for easy online sil’s newest amplifiers, power modules, analog multiplexers, FET purchase. Mouser.com also houses an industry-first interactive cata- drivers, PWM controllers, interface ICs, switches and video ICs. Inter- log, data sheets, supplier-specific reference designs, application sil's products are known to simplify the design process by integrating notes, technical design information, and engineering tools. functions that design engineers need to make their products the best in their markets in a very efficient way.

“We are very pleased to welcome Intersil to our lineup of industry- www.mouser.com leading semiconductor suppliers. Our collaboration with Intersil is great news for design engineers who want to speed their time-to- www.intersil.com market,” says Mike Scott, Mouser’s Vice President of Semiconduc- tors. “We look forward to a long, prosperous business relationship between our two companies.”

www.bodospower.com September 2012 Bodo´s Power Systems® 7 CONTENTS

LED professional is the First Publication to be Awarded Membership with ISA Luger Research / LED professional delighted to be given the opportunity to work with ISA and their mem- announced today that their membership bers to assist the development of LED technologies, influence growth application has been accepted by the Inter- in the Solid State Lighting industry (SSL) and take part in shaping a national SSL Alliance (ISA) making them sustainable society. We already work with many of the ISA members the first publishing house to join this not- through our publications and the LED Symposium and Exhibition and for-profit NGO. They join members from we look forward to forming even closer relationships with them. We industry, academic institutions, professional see our main role in bringing together all technological aspects of societies and associations allowing them to LED and OLED including legislation, standardization, research & work even closer with companies such as development, manufacturing and supply & distribution”. Cree, Philips, GE, Nichia, Everlight, Frauenhofer, Osram and many more. Both ISA and LED professional are already part of international co- operations and are looking to extend global initiatives to accelerate ISA is an international alliance of regional alliances and associations, and foster the development of the international SSL industry and renowned universities and institutions and leading companies in the applications. SSL field. It is an independent legal entity which aims to enhance public-private partnership and intensify global cooperation to accelerate and foster the sustainable development of SSL. www.led-professional.com

Siegfried Luger publisher of LED professional and director of the LED www.lugerresearch.com professional Symposium + Expo commented: “We are absolutely electronica India and productronica India Starts on September 11, in Bangalore

After an overwhelming response at Delhi, electronica India 2012 and The shows will be held at Bangalore International Exhibition Centre productronica India 2012 will be back to Bangalore, and will play host (BIEC) from September 11, to September 13, 2012. Attractions this to over 900 exhibitors, participating companies and country pavilions year include the Special Exhibit Areas like PCB Pavillion, Soldering from China, Germany, Hong Kong, Singapore and Taiwan. The competition & training program conducted by IPC, which will focus on events will also have participation from Italy, Japan, Malaysia, Spain, quality assurance initiatives. This is going to establish electronica Switzerland and USA, all together from 25 countries. India and productronica India as the most influential platforms for the electronics industry in the country. electronica India and productronica India, are one of the best promoted brands in India. In 2011, the shows managed to receive over 10,000 The events will be accompanied by the technical conference visitors and in 2012, the number of visitors is expected to be much SMALED, part is also a symposium on Failure Analysis and Reliabili- higher than last year. Major players exhibiting this year include Agilent ty of Electronics Assemblies (FARE) which will be hold on September Technologies, ASYS Group, Bergen Systems, Infineon, Juki India, 12, 2012. Kaynes Technology, Leaptech Corporation, Maxim SMT Technologies, NMTronics, NXP Semiconductiors, Panasonic Industrial Device, RS Components & Controls, Renesas Electronics, Rohde & Schwarz http://electronica-india.com India, STMicroelectronics and TATA Power SED, to name a few.

Solutions for the Supply of Energy in the Future "Smart energy solutions" is one of the main will present technical solutions for the intelli- be expanded, they must also be controlled themes of electronica 2012, the International gent supply of power in the future. Leading and monitored more intelligently. electronica Trade Fair for Electronic Components, Sys- international executives will also discuss this 2012 will present technical solutions that will tems and Applications. From November 13 – topic at the CEO Roundtable, the motto of secure the supply of energy in the future. 16, 2012, the industry’s leading manufactur- which is "Semiconductor Solutions for Smart Exhibitors will present components, systems ers from around the world will present their Grid Challenges". and applications, from sensor technology, solutions and products in the sectors for Around the world, renewable energies play the latest network control technical, data- energy efficiency, energy storage, LEDs and an increasingly important role in the supply infrastructure solutions and battery-storage smart grids. Above all, the future of power of energy. Given the increased integration of systems to intelligent devices for measuring grids is expected to be the center of atten- solar and wind energy, energy production is consumption on the part of end consumers tion. Against the backdrop of the global tran- becoming increasingly decentralized and (smart meters). sition to alternative energy sources and the subject to greater fluctuations. To deal with expansion of power grids, electronica 2012 the resulting challenges, grids must not only http://electronica.de

8 Bodo´s Power Systems® September 2012 www.bodospower.com Allegro Motion Control

Brush DC Motor Driver IC Solutions

Allegro MicroSystems, Inc. offers a complete lineup of DC motor driver ICs for all markets, including office automation, automotive and industrial. Depending on the needs of a given application, Allegro IC solutions can include features such as:

• Low standby current for • Low standby current energy efficiency • Commercial grade and fully • Internal DMOS outputs or gate automotive qualified drivers controllers to drive external Featured Allegro Brush DC Motor Driver ICs • Small footprint and reduced MOSFETs external components Part Output Output Number • Parallel interfaces with forward, • Strong protection and Number Voltage Current of Range (V) Range Bridges reverse, coast, and brake modes diagnostic features A4950* 8 to 40 3.5 A Single full Internal A4952 8 to 40 2 A Single full Applications include: MOSFET A4953 8 to 40 2 A Single full A4954 8 to 40 2 A Dual full Office Automation Industrial Automotive A3946* 7 to 60 >5 A Typical Half bridge - Inkjet / laser printers - Power tools - HVAC systems MOSFET A3921/41* 7 to 50 >5 A Typical Single full - Copiers - Factory automation - Hydraulic pumps Gate A4940* 5.5 to 50 >5 A Typical Single full - Office equipment - Gaming electronics - Actuators Drivers A4957 4.5 to 50 >5 A Typical Full bridge peripherals - Scanners - Electronic Power * Automotive Grade Available - Vending machines Steering (EPS)

Representatives ALLREM SSG Semiconductor Systems GmbH Consystem S.r.l. MSM Ltd. 94616 Rungis Cedex, FRANCE D79856 Hinterzarten, GERMANY I-20144 Milano, ITALY Weybridge Surrey, KT13 0RZ Tel:+33(0)156700380 Tel: +49 (0) 7652-91060 Tel: +39 02 4241471 United Kingdom E-mail: [email protected] Website: www.ssg-de.com Website: www.consystem.it Tel: +44 (0) 1932 341106 E-mail: [email protected] E-mail: [email protected] E-mail: [email protected]

www.allegromicro.com/camp1136 NEWS

Partner to Deliver Advanced Power Control and Conversion GaN applications GaN Systems Inc, a leading developer of gallium nitride power tems. “Working with the Converter Technology team and directly with switching semiconductors, and Converter Technology Ltd., a U.K.- Dr. Mosely, we are keen to give our customers expert technical sup- based company that provides design consultancy and hardware pro- port and best-in-class system level solutions.” Dr. Mosely’s deep totyping services, announced a joint strategic agreement to advance roots in power system design, his strong customer relationships and adoption of new GaN applications. Under the terms of the agree- the company's excellent test and analysis capabilities make this an ment, the companies will work directly to develop application notes, ideal catalyst to accelerate the adoption of GaN power switches. We reference designs, training material and cutting edge technology expect this relationship to become a model for local customer sup- demonstrators to accelerate the commercialization of GaN Systems’ port for our components across the globe.” Added Dr. Iain Mosely, unique technology. Technical Director of Converter Technology, “We are delighted to be working closely with GaN Systems to provide expert design support Working with customers, new applications will be developed where and cutting edge technology demonstrators. The remarkable perform- the performance of GaN Systems’ switches and solutions will deliver ance level available from GaN Systems’ technology presents an ideal maximum impact. To support the adoption of the new applications, opportunity to push the limits in power conversion and we look for- GaN Systems and Converter Technology will promote industry ward to demonstrating what can be achieved in real world customer engagement, and demonstrate key benefits to GaN Systems’ cus- designs.” tomers. The engagement will further accelerate the adoption of GaN System’s technology into the next generation of power conversion systems in a power devices market worth $14 billion. www.gansystems.com “Converter Technology and GaN Systems share a passion to advance the state of the art in power control and conversion applica- www.convertertechnology.co.uk tions”, said Geoff Haynes, VP Business Development of GaN Sys-

Electric Drives Production Conference and Exhibition Nuremberg, 16–17 October 2012

Scientific Partner: Produce optimized electric drives and meet the requirements of industrial motors and electromobility. Products, ideas, and concepts will be shown in the conference and the exhibition of E|DPC. Don't miss it.

Official Association Partner:

edpc-expo.com

10 Bodo´s Power Systems® September 2012 www.bodospower.com Technology You Can Trust

Avago Technologies Optocouplers Safety Certiﬁed Protection... Worldwide!

Optocouplers are the only isolation devices that meet or exceed the IEC 60747-5-5 International Safety Standard for insulation and isolation. Stringent evaluation tests show Avago’s optocouplers deliver outstanding performance on essential safety and deliver exceptional High Voltage protection for your equipment. Alternative isolation technologies such as ADI’s magnetic or TI’s capacitive isolators do not deliver anywhere near the high voltage insulation protection or noise isolation capabilities that optocouplers deliver. For more details on this subject, read our white paper at: IEC 60747-5-5 Certiﬁed www.avagoresponsecenter.com/672 NEWS

HUSUM WindEnergy 2012 Carries the Official WindMade Label Being awarded the WindMade label emphasises HUSUM WindEner- cate their commitment to renewable energy to the outside world and gy 2012’s commitment to the use of renewable energy. The Wind- stand apart from the competition. The non-profit organisation behind Made label is granted by a nonprofit organisation solely to enterpris- the WindMade label only awards the certificate to events that draw es that draw a share of their power from renewable energy sources – their power exclusively from renewable energy sources. To be able to and in the case of exhibitions and events this share must be 100% in carry the WindMade label, an event must be 100% powered by order to carry the label. As the leading international wind industry renewable electricity, the largest share of which must come from wind trade fair, HUSUM WindEnergy 2012 not only affirms its leading role power. As far as HUSUM WindEnergy is concerned, this includes the in the international exchange of ideas and experiences in the wind preparation of the event by Messe Husum, the power consumption industry, but also its leading role in supporting the direct use of wind by exhibition and congress, but also the receptions and dinners that power. are part of the event. In order to fulfil the high requirements set by WindMade, HUSUM WindEnergy invests in GoldPower certificates from a wind power project in Taiwan, which cover the total power consumption.

HUSUM Wind Energy 2012 is the first German WindMade event Since the first WindMade label was awarded in November 2011, many leading businesses, such as Deutsche Bank, Motorola Mobility, Vestas Wind Systems, Better Place and many others, have undertak- en to be certified as WindMade. HUSUM WindEnergy 2012 is the first German event to bear the label. “We are overjoyed that the 2012 fair has been awarded the WindMade label. The WindMade organisation corresponds excellently with our objective of making the use of wind and other renewable energy sources attractive for everybody. As the world’s most influential trade fair for wind power, HUSUM WindEnergy has such international charisma that it can also use the WindMade label as a message to other enterprises and The biennial HUSUM WindEnergy trade fair has been the manifesta- events in the industry”, emphasises exhibition boss Peter Becker. tion of the pioneering spirit and fascination for wind power since as WindMade’s CEO Henrik Kuffner added, “We are proud for HUSUM far back as 1989. In the meantime the industry has not only come of WindEnergy 2012 to carry the WindMade label and for it to spread age, but all the businesses involved now accept their responsibility in message that wind power has become the technology of choice for ensuring that they use the potential offered by renewable energy for many electricity users. This includes event organisers, but also large maintaining and manufacturing their products. As a platform for the and small companies from a great variety of sectors.” international exchange of ideas and experiences in the wind industry, HUSUM WindEnergy also plays a major role in the constant increase www.windmade.org of wind power across the world. The 2012 show applied for the Wind- Made label so that it can clearly emphasise the fact that it practises www.climatefriendly.com what it preaches when it comes to running the fair itself. The Wind- Made label enables businesses and event organisers to communi- www.husumwindenergy.com Successfully Start of 8-inch GaN-on-Si Development AIXTRON SE today announced that EpiGaN, a new customer and a Si, but we are confident that the combination of our enduring expert- start-up manufacturer of III-Nitrides epitaxial material in Hasselt, Bel- ise and the leading edge equipment and process technology from our gium, has successfully commissioned two new MOCVD systems, partner AIXTRON will deliver all our objectives rapidly and efficiently.” able to operate either in multiple 6” or in 8” configuration. It will use the systems to commercialize 6-inch GaN-on-Silicon wafers for a Dr. Frank Wischmeyer, Vice President and Program Manager Power range of power and RF electronics devices as well as to develop the Electronics at AIXTRON SE, adds: “We are very pleased to next generation of 200 mm GaN-on-Silicon wafers. announce this new order from one of Europe’s newest and most The reactors were installed and commissioned by AIXTRON promising start-ups. AIXTRON is pleased to partner with EpiGaN as Europe’s service support team at the company’s purpose-built, state- they advance equipment, processes and materials for larger area of-the-art facility located in Research Campus Hasselt, Hasselt, Bel- GaN-on-Silicon wafers.” gium. Incorporated in 2010, EpiGaN is providing device manufacturers with Dr. Marianne Germain, CEO of EpiGaN, comments: “EpiGaN is a access to a unique, proven technology addressing market segments spin-off of the world-renowned IMEC. After completing our funding such as power supplies for consumer electronics, hybrid electric vehi- round, we were ready to implement the strategic plan to establish our cles, solar inverters, RF power for base stations, smart grid, etc. The production capacity. After several years of efficient joint collaboration company is also participating in the EU project HiPoSwitch which will with AIXTRON towards GaN-on-Si, it was evident that these CCS develop more compact and more powerful energy converters. systems from AIXTRON perfectly suit our needs. The EpiGaN team has worked with AIXTRON CCS MOCVD systems at IMEC and we www.aixtron.com have jointly published numerous papers on GaN-on-Silicon development. There are challenges ahead for high voltage 200 mm GaN-on- www.epigan.com

12 Bodo´s Power Systems® September 2012 www.bodospower.com Let’s face it – thin is in. Intersil’s ISL8200M, the world’s thinnest 10 Amp power module POWER at just 2.2 mm, is so thin it can be mounted on the backside of most PCBs. That’s one more way we’ve made your design job simpler. MADE Whether you’re looking for analog or digital power solutions, the only name you need to SIMPLE, remember is Intersil. MADE SMALLER

Ultra thin. Yet fully loaded.

Go to intersil.com/powermodules for design resources including videos, samples, eval boards, software, drivers and gerber files.

ɼ67$57'(6,*1,1*12: ,17(56,/&2032:(502'8/(6 NEWS

Radiation Hardened MOS Switching Devices for Space and Avionics Applications Infineon Technologies introduced its first power switching devices requirements of the European Space Agency (ESA). The devices are designed specifically for use in space and avionics applications. The fully qualified according to ESCC5000. Infineon is the only European Radiation Hardened (RH) PowerMOS devices of the BUY25CSXX supplier for 250 V RH PowerMOS devices that fulfill all ESA require- family offer best-in-class performance to support design of energy- ments. efficient power conditioning and power supply systems for space use. Efficiency and reliability are critical parameters in space applications, They combine Infineon’s expertise in high-reliability transistors and in where size and weight restrictions on all system components require high-efficiency MOS switching devices. Infineon is the leading the best possible performance matched with protection against dam- Europe-based supplier of radio frequency diodes and microwave age from space-born radiation transistors for satellite communications systems. The RH PowerMOS technology is hardened against Total Ionizing Dose (TID) and Single Event Effects (SEE) to offer devices that meet www.infineon.com/RadHardMos Success of Technology Strategies in LED Lighting With the arrival of LED technology in the future, the LpS 2012 introduces four central source, electronics, optics, cooling and world of luminaries completely new chal- building blocks at this year’s event which will mechanics. Competent partners from all lenges arose for everyone in the market. The take plce from 25th to 27th September in those fields are needed to design a compre- technological change combined with the Bregenz, Austria. hensive state of the art system. Access to a shifting market led to more or less grave Building Block 1: „Leading-¬-Network“ is crucial to establish uncertainties and questions with regard to Leading background strategies future partnerships. the right orientation in the years ahead. Building Block 2: Patent rights Therefore, the technological roadmap which Building Block 3: Technology Trends www.lps2012.com should be based on a sound technology Building Block 4: Cooperation Partner for strategy is a crucial element to develop a Academia and Industry www.led-professional.com successful company strategy. To enable the Quality LED lighting systems are created industry to plan a successful technological through a balanced combination of light www.lugerresearch.com

Electric Automation Systems and Components International Exhibition and Conference Nuremberg, Germany, 27–29 November 2012

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World'sWorld's MostMost PowerfulPowerful 1700V1700V DualDual IGBTIGBT ModuleModule forfor HighHigh PowerPower EnergyEnergy ConversionConversion

[email protected] · www.mitsubishichips.eu BLUE PRODUCT OF THE MONTH

Reduction of Extreme High Inrush-Currents Power circuits with low input impedance parent as the resistance of the part will be rating up to three times more than a normal stress the main power with extreme high few milliohms. The devices are available in wire contact, where there usually is a single inrush current peaks. The new power-NTC´s 22, 32 and 35mm disc diameter and up to small line of contact with the ceramic disc. of AS-series can solve this problem in easy maximum of 50 ampere continuous current. The other advantage of using AS series ther- and efficient way. mistor lies in the longevity of the product. An experiment has also shown that due to uni- form current density with in each ceramic disc, tremendously reduces failures due to fatigue and aging and reduces the infant mortality rate or premature failures.

For applications on power- capacitors or - transformers, whose activation is mostly fin- ished after about 0.1sec, normally requires only one AS-limiter per each phase.

Figure1: Device Samples Figure 2: Thermal image demonstrates con- Unless the energy rating of one AS-limiters formity in power distribution At the turn-on mode the NTC-material is not enough or for special applications like reduce the resistance to significant values by A full faced copper blade contact on the motor starting two or more AS devices can preheating themselves. The compact ceramic disc provides uniformity of tempera- be switched in series or use the AS devices devices can be short circuited with a relay ture across the disc, hence avoiding any with a lot of mass like AS35 6R025. after in rush current duration is over. In temperature gradient with in the disc. This cases where the reset time of the thermistor means there will be no hot spots on the disc. is insignificant the As series thermistors can In addition experiments have shown that this be left in the circuit. They will appear trans- method of manufacture increases the energy www.Thomatronik.de

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16 Bodo´s Power Systems® September 2012 www.bodospower.com Pre-Applied Thermal Interface Material (TIM) The Infineon-qualified solution

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Power Solutions for More Efficiency In a move to boost power density and efficiency, Vicor has launched the Picor PI33XX Cool-Power ZVS buck regulator series for PoL DC/DC regulation. The integration of a ZVS topology is claimed to provide best in class power efficiency up to 98% peak. Despite this, Vicor’s First Direct 48V-to-Processor solution is Intel x86-compliant and addresses datacentre and telecom Applications offering 30% reduction in power conversion loss per processor. By Marisa Robles Consée, Corresponding Editor; Bodo’s Power Systems When is a buck regulator more than ‘standard’? The integration of a eliminating a second stage of conversion necessary with traditional Zero-Voltage Switching topology (ZVS) might give a clue. Vicor buck regulators”, says Claudio Tuozzolo. “Customers are looking for

claims that its PI33xx series using the soft switching ZVS topology higher efficiency, density, power processing with a higher Vin/Vout provides best in class power efficiency up to 98% peak. Products in ratio and faster switching frequency”, he claims. Luckily, the power the PI33XX series are highly integrated with control circuitry, power semiconductor industry has made significant improvements: “Thus, semiconductors and support components in a 10 mm x 14 mm x 2.56 high density regulators have evolved leveraging the latest in IC inte- mm LGA System in Package (SiP). Claudio Tuozzolo, President of gration, MOSFETs, and packaging. These high density regulators still Picor, a subsidiary of Vicor, describes his company as focused on cannot keep pace with the demands put on them by new systems innovative and integrated solutions based on control, power conver- with ever increasing higher density”, explains Tuozzolo. "However, sion and packaging. In his view, this has resulted in products with switching losses are affecting performance. While you can get better high levels of integration, high performance architecture for power efficiency, it's often a trade off against density. ZVS gets around this conversion and high performance packaging. "I'm not aware of many and that's why we deployed the technology at the point of load." companies that can innovate at all three levels," Picor’s President added. The buck regulators can convert input supplies ranging from Soft vs. hard switching 8V to 36V to output voltages from 1V to 16V and output current up to The primary reason for this is the switching losses hindering perform- 10A for power up to 120W. Power delivery can be further increased ance within the regulator MOSFETs. Without addressing these losses by interleaving up to six PI33XX buck regulators using single wire head on, only incremental performance increases can be expected. current sharing without the need of any additional components. Regulator MOSFET switching losses are the losses attributed primarily to: the high side MOSFET during turn-on, Miller gate charge, and body diode conduction losses. High side MOSFET turn-on is when the regulator MOSFET has the highest voltage and current switching and thus the highest power loss attributed to it. These losses further magnify themselves within a design as higher input voltages are converted or regulated.

The higher the input voltage, the higher the voltage across the primary MOSFET and the higher the losses at turn-on. These switching losses prevent dramatic improvements in overall power system solutions. For example, within industrial process control systems a desired regulation of 24V to 3.3V typically is achieved by first regulat- ing from 24V to 12V followed by a second regulator converting 12V to 3.3V. In contrast, a single regulation stage, like the PI33XX, can Figure 1: ZVS Buck-High Efficiency regulate 24V to 3.3V with an efficiency level at or higher than the two stages and dramatically improve cost, board space, and reliability. The use of a ZVS topology enables high-frequency operation that maximizes efficiency by minimizing the significant switching losses Switching losses also limit the switching frequency of the regulator. A associated with conventional buck regulators that use hard-switching higher switching frequency causes a longer MOSFET switching time topologies. The high switching frequency series also reduces the size and in consequence more losses. The inability to switch at a high fre- of the external filtering components, improving power density, while quency limits the use of smaller passive components (R’s, C’s, and enabling fast dynamic response to line and load transients. The L’s), penalizing the density of the regulator. PI33XX series sustains its high switching frequency all the way up to the rated input voltage without sacrificing efficiency and, with its ON- Contrary to this, the ZVS topology is a soft switching topology in con- time of 20ns minimum, supports large step down conversions up to trast to a hard switching topology deployed in conventional regula-

36 VIN. tors. The soft switching technology of the PI33XX provides higher efficiency and higher density than conventional regulators. ZVS topol- “One major advantage of the new buck regulators is the capability to ogy is typically associated with high performance isolated power sup- step down from a higher voltage, such as 24V, directly to the load, plies.

18 Bodo´s Power Systems® September 2012 www.bodospower.com GREEN PRODUCT OF THE MONTH

Simple to use With the introduction of the ZVS Buck Regulators Vicor marks not PI33XX series buck regulators require only an external inductor and only its entry to the Point-of-Load market but also its changing market a few ceramic capacitors for input and output filtering in order to form orientation. For many years the company achieved a big portion of its a complete high performance regulator. No frequency compensation, revenue with power solutions for the military market. “Budgetary cuts parametric settings or incremental external components are required. in recent time lead us to focus on high performance applications with- A wide operating temperature range of -40°C to 125°C allows for use in the telecom and data communication industries”, Tuozzolo admits. in almost any environment. He also sees opportunities in emerging markets like eMobility.

For designers challenged by complex distribution power schemes, Intel x86-compliant solution Picor PI33XX Cool-Power ZVS buck regulators are the only buck At the Techno-Frontier conference in Tokyo the company announced regulators in their class to offer an optional I2C extended fault its direct 48V-to-processor power conversion solution for the datacen- telemetry capability allowing for six distinct types of fault reporting. tre, cloud computing and telecom markets. Vicor’s Factorized Power Additional device-programmable I2C features include margining, solution complies with Intel’s x86 VR12.0 voltage regulation specifica- enable pin logic polarity, and phase delay. The devices are pro- tions. Vicor’s current multiplication from 48V directly to a 1V micro- grammed with the Cool-Power Development Tool. “Integrating a ZVS processor load enables more efficient power distribution and elimi- soft switching topology within a PoL buck regulator creates a new nates duplicate conversion stages found in traditional 48V to 12V to performance standard for the industry”, stated Tuozzolo, who is con- 1V power systems, yielding more than 5% greater overall efficiency vinced that “coupled with Vicor’s broad range of solutions for power in a package size that’s three times smaller than competing offerings. delivery to the board, we are enabling optimal power efficiency throughout the power chain – all the way to the point of load.” With increasing demands on datacentre and cloud computing infrastructure, efficient power management is a growing concern. For example, IBMs third supercomputer design in the Blue Gene series, ‘Blue Gene/Q’ can reach operating speeds in the PFLOPS (petaFLOPS) range, with low power consumption. It is expected to achieve 20 Petaflops at peak performance, marking it as one of the fastest supercomputers in the world. Moreover, Blue Gene/Q is expected to become the world’s most power-efficient computer, churning out 2 Gigaflops/Watt. “These computers are working with 80kW. However, datacentres like Amazon, Cisco, HP or Google are demanding 10kW performance but the trend is clearly going to 20kW. The transfer from 10kW to 20kW can hardly been addressed by conventional intermediate bus architectures. ‘Big Data’ needs efficient 48V power”, Claudio Tuozzolo explains and admits, that “in the past we were focusing on IBM's Power7 processors”. Electricity costs can account for up to 50% of annual datacentre operating expenses. The Figure 2: VR12-Chip 02 5% efficiency gain enabled by Vicor’s Intel compliant power solution can reduce per-processor power loss by 10W – or 30% – which can yield annual datacentre electricity savings of approximately $500,000 across 30,000 onsite processors.

Vicor’s non-isolated VI Chip PRM regulator and VTM current multiplier deliver an efficient 48V direct-to-load power conversion for datacentre and telecom applications. Vicor’s Factorized Power Architec- ture (FPA) separates, or ‘factorizes’, regulation and voltage transformation functions into flexible, high performance building blocks, reducing distribution and interconnect losses and eliminating bulk capacitance with greater than 1MHz response speed. “With direct 48V-to-processor current multiplication, Vicor is enabling datacentre and telecom equipment designers to achieve gains in energy efficiency,” assures Tuozzolo. “For datacentre and telecom facility operators, the cumulative reduction in energy usage, electricity expenses and

CO2 emissions can be significant.” Figure 3: VR12-Performance The high demand on power solutions in datacentres is due to the The Picor Cool-Power portfolio currently consists of the PI31XX increasing ‘triple-play’, i.e. boosting data for voice, video and internet series of isolated converters and now the PI33XX series of ZVS Buck usage on mobile phones and tablets. Powerful services like Apple’s Regulators. Future products in the family will include additional ZVS Siri need powerful datacentres as backbone. Due to this, the Voice- buck regulators with higher voltage and higher current capability, ZVS only ‘telecom’ equipment has become ‘datacom’, where small 30W buck-boost regulators, and ZVS boost regulators, “all expected to set ASICs have been replaced by Intel x86 130W processors like Sandy new industry benchmarks in efficiency and density”, Picor’s President Bridge and Ivy Bridge processor chipsets. states. www.vicorpower.com www.bodospower.com September 2012 Bodo´s Power Systems® 19 GUEST EDITORIAL

Back to Normal Soon Chipmaker Renesas Electronics is looking for a fast way out of the severe situation with an enormous restructuring plan compensating the massive loss in the last financial year By Marisa Robles Consée, Corresponding Editor; Bodo’s Power Systems

As a result of the Great East Japan earthquake, the flooding in Thai- As a result of the “Early Retirement” program, the company expects land as well as the sluggish world economy Renesas is “in urgent a cost reduction of about 43 billion yen (about 400 Mio. Euro) for this need of business recovery”, admits Robert Green, President and fiscal year ending March 31, 2013. About 5000 employees, most of CEO of Renesas Electronics Europe. In these circumstances, Rene- them located in Japan, have the choice to accept this measure by sas is further accelerating its moves to achieve more efficient produc- October 31, 2012. In order to achieve this, Renesas will offer special tion and strengthen its financial basis to enhance its profitable struc- incentives in addition to their retirement payment to employees volun- ture. To face this challenge, the Japanese company is now looking tarily taking early retirement. In addition, outplacement support will be for markets with high growth potential, as the Japanese market is provided through an outside agency for those who request it. saturated and won’t offer rapid growth prospects within the next years. As a consequence, Renesas is focusing on the “overseas Outsourcing leading-edge technology markets”, particularly in emerging countries with robust potential After its merger with NEC Electronics, Renesas continues to be the growth. Brasil is one of the most attractive regions beside China and world’s largest MCU vendor with a global market share of 27% (its India. Also the overseas automotive market is attractive. Electric and share for automotive MCU is 42%), the goal of the company is to cre- hybrid vehicles are demanding more and more semiconductors like ate new MCU customers. However, part of the success is what the MCU and power components. company claims to be the “industry’s first” 40-nm embedded flash memory IP for automotive real-time applications. Renesas assures On the way to a robust and that its 40-nm flash memory IP guarantees 20 years of data retention profitable structure, Renesas and can be read up to a junction temperature of 170°C. Additionally, has targeted the fields relat- the code flash supports a read speed of 120 MHz, and the data flash ed to automobiles and smart achieves an industry-leading long data-retention period of 20 years society. While it plans to even after 125,000 program/erase cycles. The embedded flash strengthen its microcomputer (eFlash) technology, the Japanese MCU giant’s crown jewel, comes business and analog/power with TSMC’s CMOS logic and analog IP. Also Renesas’ SG-MONOS business, it’s going to slim technology holds an unrivalled position in the industry with the launch down its money-losing SoC of 28nm development. business drastically. These are the main measures in Therefore, another step to survive cut-throat global competition is to Figure 1: Rob Green: order to get “back to normal outsource all its output of MCU with circuitry widths of only 40nm or “Back to normal soon” soon”, promises Rob Green. less, taking advantage of TSMC's more advanced production technology. Rob Green pointed out that this is “the first step toward further Reforming domestic production collaboration between TSMC and Renesas.” For Renesas’ part, the "Taking into consideration the current environment, we believe that company is now sending a clear signal that it’s more willing to pursue we need to carry out reforms in a very short period”, is Rob Green an “outsourcing” model – including MCUs for automotive applications. pointing out. As part of the move, Renesas decided to reform domes- Previously, Renesas executives had said that Renesas was commit- tic production sites of Renesas Group, as well as to streamline ted to Japan-based manufacture of the company’s “core products” employees. like automotive MCUs.

Currently, the company has nine manufacturing bases (15 lines) for According to Renesas, the Japanese company outsourced 15% of its front-end processes excluding its Tsugaru Plant, which was transferred semiconductor products in 2011. That ratio is likely to double to 30% to Fuji Electric on July 1, 2012. Trying to optimize production structure, by 2016, says Green. Although, Renesas had previously agreed to the company transferred its power amplifier business to Murata Manu- outsource MCUs to TSMC using 90-nm eFlash process technology. facturing and has withdrawn from the high-volume display driver IC However, that was based on “a straightforward outsourcing model,” business, explains Rob Green. On the front-end site it has transferred explained Green, under which “TSMC simply builds our eFlash based the Roseville 8-inch line to Telefunken and scaled down the Kofu 6- on Renesas’ 90-nm specifications, which the foundry would not be inch line as well as the Takasaki 5-inch line. Also it has closed the able to release to its other customers.” In contrast, the new 40-nm Shiga 5-inch line and the Oume factory (Tokyo Device Division). Rene- agreement will allow TSMC to use Renesas’ MONOS (Metal-Oxide- sas also has nine manufacturing bases for back-end processes in Nitride-Oxide-Silicon) embedded flash technology on TSMC’s own Japan where the production will be tightened accordingly. 40-nm process, and make it available for its customers throughout the world. However, the company plans to complete the reorganization of the domestic manufacturing bases within three years. The number of Looking for power employees working for the manufacturing lines that the company By the year 2025, electric or partially electric vehicles will account for considers transferring or consolidating is 3,000 to 4,000. up to 50% of new vehicle registrations in Europe. The European

20 Bodo´s Power Systems® September 2012 www.bodospower.com GUEST EDITORIAL

Union is setting the pace of change: it has decreed that CO2 emis- improve CO2 or fuel efficiency”, he says. The NP Series are qualified sions must be reduced by 20% between now and 2020. Therefore, according AEC-Q101 automotive standards and they are RoHS com- automotive customers in Germany and France are very interested in pliant. Renesas Electronics developed new PowerMOSFETs which electric vehicles. According to a study of Roland Berger Strategy enable the realization of more compact automobile control units and Consultants 37% of the customers (France: 35%) are considering allow system designers to make efficient use of the limited space buying an electric car. On a worldwide view, eMobility is here to stay. available in automobiles. This is clearly illustrated by the fact that Mr. Obama's stated goal is to have one million electric vehicles on the road in four years' time, Top-level low Vce(sat) and high-speed switching technology for IGBTs while China is running 25 pilot projects and has pledged to invest with low loss, high voltage tolerance and large current capacity is more than 10 billion Euro in vehicle electrification. another topic addressing motor drive in hybrid and electric vehicles for more comfortable drive and longer effective running distance. The Renesas line-up of thermal FETs, which have on-chip overheating protection functionality and can easily substitute for power MOSFETs, and IPDs for body applications, which combine high tolerance, high reliability, and proven load short reliability, will continue to be extended moving forward in response to demand for improved system reliability. “In future we will offer an even broader range of solutions, and products are currently under development for applications such as LED headlight controllers, lithium-ion battery monitors, and three- phase motor pre-drivers”, he states.

Figure 2: Renesas technologies contribute to ‘Green Cars’ Particularly proud is Rob Green about the advanced package technology. According to him, Renesas as a company is developing pack- For Robert Green this means a huge market potential within “power age technology employing thicker aluminium wiring and higher line supplies which combine automotive power devices with energy effi- counts to help reduce on-resistance, alongside efforts to reduce the ciency and compactness”, he remarks while pointing out that Rene- on-resistance of power MOS chips. “We are also developing and sas has four technologies that contribute to ‘Green Cars’: “The num- implementing multi-chip package technology for use with products ber of vehicle electronic control units increases each year, creating a such as IPDs for large-current applications and motor drive ICs”, he need to minimize package size and weight while maximizing perform- says. High-pin-count power packages providing high heat dispersion ance. Renesas' PowerMOSFET NP-Series has been designed to and support for multi-functionality are under development as well. meet strong demand requirements of the automotive fields which www.renesas.eu

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ELECTRONICS INDUSTRY DIGEST By Aubrey Dunford, Europartners

GENERAL company effective July 15. Hans Rijns, sen- PASSIVE COMPONENTS Global technology ior vice president research and develop- Bourns, a supplier of automotive sensors, executives say China ment, will take over as interim CTO reporting circuit protection solutions, magnetic prod- and the US are the to Rick Clemmer. ucts, microelectronic modules, trimming and two countries most Maxim Integrated Products, a supplier of precision potentiometers, panel controls and likely to come up analog and mixed-signal semiconductors, encoders and resistive products, has com- with “disruptive tech- announced a $ 200 M multiyear investment pleted its purchase of substantially all of the nology break- to upgrade its U.S. wafer fabrication facilities assets of Jensen Devices. throughs” that will in Beaverton, Oregon; Dallas and San Anto- have a global impact nio, Texas; and San Jose, California. Maxim OTHER COMPONENTS in the next two to will use the multiyear investment to upgrade Rohde & Schwarz has acquired SwissQual, four years, according to KPMG’s global Tech manufacturing equipment, improve process a provider of systems for measuring and Innovation Survey 2012. technologies, convert to newer technology assessing the quality of service (QoS) in nodes, and assimilate production from wireless networks, with around 100 employ- SEMICONDUCTORS recently acquired companies. Maxim ees. Through this acquisition, founded in Measured in Euro, European semiconductor employs 9,300 employees worldwide, includ- 2000 and based in Zuchwil, Switzerland, sales were € 2.173 billion in May 2012, up ing approximately 1,000 manufacturing Rohde & Schwarz will be in a position to 1.7 percent on the previous month and down cleanroom workers in its four U.S. fabs. even better and more fully address the drive 5.9 percent versus the same month a year Maxim reported revenue of approximately $ test market with a complete technological ago, so the WSTS. On a worldwide basis, 2.5 billion for fiscal 2011. offering. semiconductor sales in May 2012 were $ STMicroelectronics and Harbin Institute of 24.392 billion, up 1.4 percent versus the pre- Technology (HIT), one of China’s most DISTRIBUTION vious month. This results in a decrease of renowned national key universities, To strengthen Avnet Abacus’s position in the 3.4 percent versus the same month in 2012. announced the opening of a joint laboratory German passive components distribution Combined global sales for the March-April- to encourage innovation in electronics. At the market, Avnet has acquired Altron, an inter- May period increased over December-Janu- initial stage, the joint lab in China will focus connect, passive and electromechanical ary-February by the highest rate (6.4 per- on smart-sensor applications. components (IP&E) distributor in Germany, cent) since June 2010. Additionally, May representing over 40 suppliers. marked the third consecutive month that OPTOELECTRONICS Avnet Memec, an Avnet company, has been sales have grown over the previous month – Finisar, a supplier of fiber optic subsystems appointed as the pan-European distributor the longest streak of sequential monthly and components for networking, storage, for Infinite Power Solutions, a US-based growth since September 2010. wireless, and cable TV applications, has manufacturer of solid-state batteries. The In urgent need of business recovery, Rene- entered into an agreement to acquire RED-C new agreement will enable Avnet Memec, a sas Electronics announces the “direction of Optical Networks. The acquisition will broad- specialized semiconductor distributor, to pro- various measures to establish robust and en Finisar’s product lines primarily for tele- vide a broader product offering to the grow- profitable structure”. Renesas will focus on com applications by adding key amplification ing energy harvesting segment. overseas market especially in the automo- technologies, including Erbium Doped Fiber Mouser Electronics has launched a new tive and smart society segments. While it Amplification (EDFA), Raman amplification technology site covering smart grid technolo- plans to strengthen its microcontroller busi- and dynamic Hybrid amplification. Finisar will gy. The new site is designed to help design ness as its core competence and pay in cash $ 23.7 M in initial consideration engineers find the latest smart grid advance- analog/power business by producing syner- for all of RED-C’s outstanding equity. Finisar ments, source product information using gy with MCU business, it will drastically slim will also pay to stockholders and certain block diagram navigation, and access the down its money-losing SoC business. RED-C employees up to an additional aggre- latest technical resources in as few clicks as NXP Semiconductors announced the gate of $ 20 M payable in cash or in shares, possible. The site features new products appointment of Sean Hunkler as executive subject to the achievement of financial per- from manufacturers, such as Texas Instru- vice president and co-general manager of formance targets related to RED-C products ments, STMicroelectronics, Maxim, AVX, operations effective July 16. Along with Chris and technologies during calendar 2013. Murata, Digi International, Epcos, and Laird Belden, Sean Hunkler will be responsible for Marl International has invested £ 150,000 to Technologies. all aspects of the company’s global opera- double its manufacturing output at its site in This is the comprehensive power related tions. Sean Hunkler will be based in Singa- Ulverston Cumbria, UK, putting it in a prime extract from the « Electronics Industry pore, as this will support the company’s ini- position to benefit from the rapid growth of Digest», the successor of The Lennox tiative to further grow its presence in the an emerging ‘green’ lighting technology. Marl Report. For a full subscription of the report Asia Pacific region. NXP also announced International has specialized in the design contact:[email protected] that René Penning de Vries has decided to and manufacture of visible LED indication or by fax 44/1494 563503. step down as member of the NXP manage- and illumination components and systems ment team and as CTO, and will leave the for nearly 40 years. www.europartners.eu.com

22 Bodo´s Power Systems® September 2012 www.bodospower.com

MARKET

Putting GaN to Work in Your Power Supply at Darnell’s Power Forum By Jeff Shepard, President Darnell Group

Gallium-nitride (GaN) is a hot topic. During the ‘quite’ month of The implications of switching with nanosecond rise and fall times are August, there were multiple announcements about GaN and its use discussed, with special attention given to the importance of minimiz- in power converters. Soraa, a developer of GaN on GaN™ (gallium ing the common source inductance is discussed. Some problems nitride on gallium nitride) solid-state lighting technology, announced with making accurate measurements are briefly discussed. that it has been selected by the U.S. Advanced Research Projects Agency-Energy (ARPA-E) to lead a project on the development of The seminar then shows examples of a 48 V to 1.2 V buck converter bulk gallium nitride (GaN) substrates for power devices. Efficient and a dual active bridge isolated dc-dc converter using GaN devices, Power Conversion Corporation (EPC) announced a high efficiency including experimental data. The advantages and disadvantages of wireless power demonstration system utilizing the high frequency GaN devices in each are discussed. The last section of the seminar switching capability of gallium nitride transistors. addresses the application issues of paralleling GaN devices, PCB layout, and thermal management. In addition, GaN Systems, a Canadian developer of gallium nitride power switching semiconductors, and Converter Technology, a U.K.- You can find the complete outline for this in-depth three-and-a-half- based company that provides design consultancy and hardware pro- hour engineering seminar at totyping services, announced a joint strategic agreement to advance adoption of new GaN applications. And it was announced that in Sep- http://dpf.darnell.com/seminar.php tember, the 2012 edition of Darnell’s Power Forum will start with a half-day, pre-conference seminar on “Putting GaN to Work in Your Using GaN as a substrate holds promise for many industries, but has Power Supply.” immediate applications for light-emitting diodes (LEDs), which Soraa manufactures. A major advancement in a commercially viable new Presenting the key benefits of GaN will be a half-day seminar titled, substrate is a promising disruptive technology in the areas of higher “Putting GaN to Work in Your Power Supply” to be presented by efficiency and performance. GaN on GaN LEDs are of particular Robert V. White, Chief Engineer at Embedded Power Labs and a interest because they have demonstrated much higher performance widely recognized expert in power systems architecture and digital than traditional lighting technologies and thus offer the potential for power management. Announced in mid-August, this practical, lead- major energy savings. ing-edge seminar will be presented 18 September, 2012, as a part of the 2012 Darnell Power Forum. This year’s Power Forum will be in According to Soraa Founder Shuji Nakamura, breakthroughs in GaN San Jose California. substrates can have far-reaching implications. "I have spent many decades of my life working on gallium nitride for LEDs because I Gallium nitride (GaN) based power switching devices are now avail- believe this is a very important development and holds great promise able from multiple suppliers. These devices offer much faster and for more energy efficient technology in lighting, power electronics and lower loss switching than today's silicon MOSFETs – and promise more." smaller and more efficient power supplies and dc-dc converters. Just as power supply engineers 30 years ago had to learn new tech- Gallium Nitride is described as a unique semiconductor used in the niques to use the newly introduced MOSFETs, today's engineers will manufacture of all white, blue and green LEDs. Most of these LEDs have to learn some new techniques to put GaN devices to work in today are made by depositing GaN on non-native substrates, typical- their designs. ly sapphire or silicon carbide. By contrast, virtually all other semiconductor technologies are based on "native" substrates, such as silicon This seminar starts with a comparison of the material properties of on silicon or gallium arsenide on gallium arsenide. Soraa is the only silicon, silicon carbide, and gallium nitride. How the material proper- LED manufacturer in the world shipping products based on GaN on ties relate to the electrical device properties is explained. Next is a GaN LEDs. To date, adoption of GaN on GaN technology for large- description of the structure and basic operating principal of GaN scale applications has been inhibited by high costs due in part to the switching devices. Then key specifications of GaN switches and sili- absence of inexpensive native GaN substrates. con MOSFETs with similar voltage and current specifications are compared. ARPA-E, a new agency within the U.S. Department of Energy that invests exclusively in transformational energy technologies, began With an understanding of the GaN switches, the discussion moves on funding Soraa as a consortium member for this project in 2011. to explore the circuit techniques needed to drive the gates of both ARPA-E’s recent decision to make Soraa the lead organization on depletion mode and enhancement mode GaN devices are shown. the project means that Soraa will become the prime contractor work-

24 Bodo´s Power Systems® September 2012 www.bodospower.com MARKET

ing with ARPA-E to commercialize GaN substrate technology. Appli- the new applications, GaN Systems and Converter Technology will cations for GaN substrates have the potential to reduce U.S. energy promote industry engagement, and demonstrate key benefits to GaN consumption by over 30%. Those same applications represent poten- Systems’ customers. tial markets, including laser diodes and power electronics, of over $50 billion annually, according a US Department of Energy study. With all this activity, GaN is gaining traction as a viable alternative to silicon MOSFETs. You can find the complete information on the In the second week of August, EPC and WiTricity™ announced the design seminar “Putting GaN to Work in Your Power Supply” at joint-development of a wireless power demonstration system based on EPC’s eGaN FETs. The system is a class-D power system operating at 6.78 MHz, and capable of delivering up to 15W to a load. The purpose of this demonstration system is to simplify the evaluation http://dpf.darnell.com/seminar.php process of the wireless power technology. The system includes all the critical components in a single system that can be easily connected to demonstrate the powering of a device with wireless energy POWER transfer. Eﬃcient

Highly resonant wireless power transfer was SOLUTIONS invented by the founders of WiTricity, and TM WiTricity licenses its intellectual property to from the wall to the point of load companies seeking to build products based on this exciting new technology. Capable of transferring power over distance, WiTricity technology enables a wide range of consumer, medical, industrial and automotive applications. Products using highly resonant wireless power transfer can meet stringent regulatory guidelines, and is safe for people and animals.

Many wireless charging products now in the market use traditional magnetic induction 10W~400 W coils with operating frequencies between 100- 300 kHz, and Class E, F and S amplifier con- Digital Power Modules verter topologies Recently, organizations such Intermediate Bus l Point of Load as the Consumer Electronics Association and A4WP (Alliance for Wireless Power) have called for a higher frequency standard (6.78 MHz) for wireless charging systems. At higher 0.25 W~600 W frequencies, traditional silicon-based power transistors (MOSFETs) approach the limit of Dc-Dc Converters their switching capability. EPC’s eGaN FETs Board Mount l Chassis Mount offer higher efficiency compared to MOSFETs at these higher frequencies.

Earlier in the month, the international partnership of GaN Systems and Converter Tech- 1W~2400 W nologies announced they will work directly to develop application notes, reference designs, Ac-Dc Power Supplies training material and cutting edge technology Open Frame l Chassis Mount l External demonstrators to accelerate the commercialization of GaN Systems’ unique technology. Working with customers, new applications will be developed where the performance of GaN Systems’ switches and solutions will deliver maximum impact. To support the adoption of With a continuous focus on eﬃ ciency, density, and system optimization, we keep our customers on the leading-edge of the power curve.

www.cui.com/power www.bodospower.com September 2012 Bodo´s Power Systems® 25 AUTOMOTIVE POWER

eCarTec: Join the eMobility Revolution! After more than 150 years of development history of the internal combustion engine, electric mobility is now ushering in a new worldwide traffic era. The electrification of drives is an important prerequisite for future mobility. The 4th International Fair for Electric- and Hybrid-Mobility eCarTec Munich 2012 will take place from October 23 to 25, 2012, showcasing the latest developments. By Marisa Robles Consée, Corresponding Editor; Bodo’s Power Systems

Electric mobility poses many challenges, not only in the vehicles but ent, the trade fair uses 33.000 m², a 50% increase in the amount of also in the infrastructure where new interfaces emerge between the exhibition space compared with 2011. The number of registered automotive industry and energy providers. Interoperability with regard exhibitors is 7% higher than in previous years. Over 550 companies to the infrastructure has been identified as a key issue for the suc- are expected to take part in eCarTec Munich 2012. Including the cess of electric mobility by the German government and others. The exhibitors of the MATERIALICA, the number of exhibitors reaches so-called standardisation roadmap has been drafted in order to about 700 in the two full exhibition halls B1 and B2. A large test realise the required standards for electric mobility quickly and in a course for electric vehicles is provided in hall B3. structured manner. As well as standardisation of the charging plugs, where no consensus has been found throughout Europe yet, data Energy storage at the forefront exchange between the vehicle and charging infrastructure also has to The trade fair’s success is also markedly due to new developments be standardised in order to ensure interoperability and customer while the focus is not only on the car, explains Metzger: “Technology acceptance. is clearly at the forefront. More than 80% of exhibitors are technology providers – whether in the area of energy infrastructure, electric motors, batteries, engineering or electronic control.” However, the success of electric mobility depends in particular on the battery capacity. “The acceptance and, thus, the economic success of electromobility worldwide depend to a very large extent on the development of battery technology.”, the expert states. The most valuable part of an electric car is the battery, allowing car manufacturers to dif- ferentiate their products, and this is where a large part of product innovation and cost reduction has to be realized. About half of the exhibition space in hall B2 is dedicated to battery and energy storage technology.

Another topic are charging stations which have made a huge leap forward, according to Burkhard Rarbach, Manager Marketing-Ser- vices of Mennekes Elektrotechnik. “The topics of high-energy storage devices and power electronics are important not only for mobile but also for stationary use.” As a pioneer for electric mobility solutions and leading supplier of charging systems, Mennekes presents an extensive system program ranging from sets with control panel and charging stations as well as IT for networked charging systems and charging columns for parking grounds, wall-mounted stations for Figure 1: Nissan-Batterie underground parking and parking garages up to home chargers for single and multiple family homes and AMAXX charging stations with According to Robert Metzger, organizer of the trade fair eCarTec, the power and charging receptacles for industry and workshops. This show reflects the actual developments on electric mobility and the allows for solutions with charging outputs from 3.7kW up to 22kW per need for more information and knowledge: “We recognized the needs charging point. of this fast-growing innovative industry for a dedicated trade event, and the potential for such a platform. The continuous growth of The Conference exhibitor and exhibition space reflects the high demand on informa- This year’s conference will provide a wide range of themes in three tion regarding electric and hybrid mobility.” parallel sessions. It focuses on themes like innovations in drives and power units, testing and production, concepts for an extensive charg- A month before eCarTec Munich 2012 opens its doors, the upwards ing infrastructure and the latest developments in energy storage. trend in eMobility is being reflected in the registration figures. At pres- However, the conference, which will take place in the Novotel Hotel

26 Bodo´s Power Systems® September 2012 www.bodospower.com close to the exhibition, is focusing on a completely new concept: The first conference day on 23 October consists of several keynote speeches and a panel discussion. On the second day in three parallel sessions different themes will be covered, and the first E-Bus Conference will take place. eCarLiveDrive – experience emotion Powerful The heart of eCarTec is not only the exhibition area but also its own test track for electric vehicles. More than 1km long, trade fair visitors have the opportunity to experience electric mobility up close. An elec- For DC/DC converters for high current power supplies tric car differs in many important characteristics from a car with a For FPGA, POL, PDA, mainboards combustion engine – differences can be seen in the motor, battery, For battery powered devices range, braking performance and gear change. The most obvious dif- Handles high transient current spikes ference is reflected in the driving experience. “We want to move No acoustic noise and leakage ﬁled away from the mere ecomobil image, let people have fun while driv- Available ex stock ing, evoke emotions and therefore influence purchasing decisions in the future. Last year the test track was a real visitor magnet with more than 3500 test drives.”

Over 100 vehicles are available – from electric-powered pedelecs and electric scooters to small and sports cars and high-tech commercial vehicles. On the trade fairs own indoor and outdoor test track, eCarLiveDrive, visitors have the opportunity to marvel at various innovative electric vehicles and even try them out themselves as drivers. An additional training area where end consumers can test the latest electric vehicles and familiarize themselves with this technolo- electronica Hall B6, Booth 404 gy is also available.

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SKiN Technology for Ultra Compact Power Modules Driven by the need for high power densities, reliability and system cost reductions power module technologies have to find new ways to address market needs. The existing design approaches have to be questioned in order to achieve significant performance improvements. In the markets for e-mobility and renewable energy the connection and assembly technology plays a key role. ByThomas Graßhoff, Semikron International GmbH, Nuernberg, Germany

Introduction The maximum permissible power dissipation of a power semiconduc- The need for compact systems, high reliability and low cost means tor is limited by the maximum permissible junction temperature, the that new technology approaches are needed and the classical mod- temperature of the cooling medium and the thermal resistance ule used in power electronics – with copper base plate, solder joints, between chip and cooling medium. In the thermal model of a power module case and wire bonding - will gradually vanish from the mar- electronic system with a high performance water cooler the thermal ket. In a 6 MW wind turbine today about 3000cm² of silicon area paste is a key influencing variable and makes up for approximately (IGBT´s and diodes) are used. To achieve a high availability of the 30% of the thermal resistance of the overall system. By sintering the power electronics new inverter concepts have to be realized. This DCB to the heat sink, this shortcoming can be eliminated. When means better utilization of silicon, less components and - very impor- bringing base plate materials into a liquid cooling circuit one has to tant - less mechanical and electrical interfaces. Today high power be extremely careful about the long term corrosion effects. The cool- inverters in the MW range are based on parallelization of modules ing media and the base plate material / coating have to match. and/or inverters. This increases the cost and reduces the overall reli- Therefore aluminium is the preferred choice due to its self-passiva- ability. Redundancy concepts are one option to achieve the request- tion (natural aluminium oxide) when liquids contain a small amount of ed high system availability but only with the disadvantage of high ini- oxygen. The dilemma is that Al is not the preferred choice for base tial investments. plates because of its high CTE and its poor compatibility to soldering. However, there are ways to solve these problems: The usage of silver diffusion sintering to attach a pure Al small area pin fin cooler to a DBC substrate. A comparison of the thermal resistances of a layered system with base plate and SKiN technology shows that the thermal resistance between the IGBT junction temperature and the temperature of the cooling liquid falls by 30%. Figure 2 shows that the main terminals are sintered as well to the DCB providing high currents Figure 1: SKiN technolo- contacts to the DC link. A welded joint to the capacitor or the DC link gy is based on an a flex- allows a cost efficient, compact and reliable interface. The high cur- ible foil used in place of rent density can be utilised to make highly compact and reliable sys- wire bonds The driver tems in the MW range. interface uses springs contacting the surface of the flexible foil.

Power module design The packaging technology - SKiN - is based on the use of sinter lay- Figure 2 SkiN based module ers instead of solder joints [1]. In this architecture wire bonds are with sintered main terminals replaced by a flexible board which is sintered onto the chip surface. and auxiliary contacts Unlike systems with bond wires, the chip has identical metallization (e.g. a silver layer) on its upper and base, meaning the highly reliable Inductivity sinter layer on the chip top and bottom is extensively connected to A module suitable for high and medium switching frequencies hast to the current path. Wire bonds can only contact about 20% of the have a low inductive design with a small stray inductance between potential die contact area. Figure 1 shows a SKiN contacted IGBT IGBT and diode. This supports a fast and low loss switching with high and Diode, where a flexible printed circuit board with Cu-layers on di/dt. To prevent high noise levels on the switching signal the cou- both sides is attached to the dies by Ag diffusion sintering. Springs pling of the main current circuit to the auxiliary circuit has to be low. provide the auxiliary electrical contacts end ensure a solder less and The usage of the flexible copper layer allows new design approaches very compact driver interface. to improve and simplify the layout of a half bridge circuit. A symmetric arrangement allows short commutation paths and simplifies the paral-

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Thermal Materials • Thermal Substrates • Fans and Blowers COVER STORY

lel operation thus current sharing between IGBT´s. Based on a simu- thermal resistance between junction and water is less than 20% for lation model of the module with major parasitic inductivities the over- the 4 parallel SKiN modules. Pressure drops of less than 100 mbar all commutation inductance has been calculated. The commutation per building block are achieved. Each building block contains 4 SKiN inductivity of both TOP IGBTs and the freewheeling diodes has been base modules and provides an output power of 700kW. The low calculated with and without terminals. inductive DC and AC link is done via a bus bar structure on opposite sides welded to the SKiN units. The gate drivers are mounted on top w/o terminals with terminals of the SKiN modules allowing a good switching control. The connec- TOP IGBT1 L=4,66nH L=15,0nH tion between the driver board and the power part is done via a spring connection (see Figure 4). The spring interface for the auxiliary con- TOP IGBT2 L=5,08nH L=15,2nH tacts supports a fast and reliable solder less assembly. Due to the IGBT1 II IGBT2 L=4,62nH L=14,8nH superior thermal performance first time ever in power module design the nominal current of 600A is also the available RMS-current at Table 1: Stray inductance with and without terminals 50°C coolant. By arranging 4 of these blocks on a mounting and dis- The simulation result shows that the major part of the stray induc- tribution rail an ultra-compact power module for up to 3 MW can be tance is defined by the main terminals. The parallel operation of two realized. The distribution rail provides the driver interface and the SKiN units increases the commutation inductivity to 25,7nH. Com- water interconnection. This concept doubles the power density of pared to a module with classical wire bonding technology the stray today known power modules and prevents all the difficulties of paral- inductance is reduced by typically 10%. An analysis of the current lelization of single modules. The climate protection has been flow during current commutation revealed, that this improvement is increased to climate class 3K4 with pollution degree 3 and supports not attributed to the elimination of the wire bond loops, but it is rather the installation in harsh environment. Compared to the SKiiP 3 evoked by a smaller enclosed lateral area of the current path on the (launched to the market in 2000) the footprint area has been reduced SKiN flexible circuit layer. The close parallel operation of two mod- by 70% for the same achievable output power and enables a reduc- ules reduces the stray inductance compared to module designs with tion of the inverter size by 35%. bus bars by at least 50% and is a good indication for the expected good current sharing. The main inductance defined by the main terminals can further be improved by a different arrangement. This shows the suitability of the SKiN technology to be the next packaging platform for wide band gap materials.

Figure 4: Detailed view of Assembly concept for Multi MW modules the spring contact to the Based on the thermal performance and the achieved power density a PCB and compact power new design approach has been done to arrange power electronics block with 4 SKiN units and cooler in a different way. The high achievable power density has and driver board the biggest benefit for liquid cooled applications. Today most coolers are arranged on the same level as the main assembly direction of Dynamic performance modules and bus bars. The small SKiN units allow another design In order to verify the dynamic performance switching tests have been approach. The SKiN modules are arranged on the opposite sides of done. Four blocks are mounted on the distribution rail and configured a water cooler forming a power module building block (Figure 3). The as paralleled half bridges. Figure 6 shows the switching behavior of a main water flow is using the third dimension. 1700V unit. With an DC link voltage of 1300V it was possible to switch 2.000A until reaching the blocking voltage limit. In total 16 SKiN units each rated at 150A Icnom are used. The close and low inductive connection between adjacent modules reduces the inductivity and allows a superior current sharing between paralleled units. Each power block has also an excellent overload capability without the need for any snubber capacitors. For one power block a pulse switching of 2400A has been done.

Figure 3: Arrangement of modules in the power building block

The water flows via a water distribution channel to the four pin fin coolers. Multiple building blocks are arranged on a water distribution rail. Compared to the SKiiP 4 design the thermal performance Rth(ja) is decreased from 0.36K/W for 1cm² chip area to 0.26K/W. The pressure drop has been minimized by an optimal pin fin design. The lami- nar water flow ensures a close to perfect cooling performance of the Figure 5: Arrangement of four power building blocks with interface entire heat sink surface. First result show that the difference in the unit (view from AC side)

30 Bodo´s Power Systems® September 2012 www.bodospower.com COVER STORY

Figure 6: Switch-on and Switch-off characteristics of the TOP switch with Rgon = 0,5 Ω and Rgoff = 6,2 Ω

Conclusions The SKiN-technology is a revolutionary progress in technology. It combines a reduction in thermal resistance and an improved internal parasitic inductance with the enhanced reliability of a wire bond free package technology platform. However in order to exploit the advantages emerging from this new technology, the module outline and system configuration are different to this new packaging platform. for low voltage inverter using all the known benefits in terms of less restrictions and lower costs compared to medium voltage systems. Due to the elimination of thermal interface materials and the integra- With SKiN technology, a packaging technology has emerged which tion of a high performance pin fin heat sink it is possible to double embraces the new wide band gap power devices and enables their the power dissipation in comparison to traditional designs. Just the use even in the medium to high power arena. elimination of the thermal grease layer exhibits an improvement of 25% of the total thermal resistance junction to water. The SKiN base References unit is a building block supporting a compact assembly. This is [1] P. Beckedahl et al.: Performance comparison of traditional pack- ensured by a screwless connection of the main terminals and a aging technologies to a novel bond wireless all sintered module; spring contact interface to the driver board. A new design approach PCIM Europe 2011 using a 3 MW water-cooled module for use in wind power converters [2] C. Göbl, P. Beckedahl: A new 3D power module packaging with- shows that twice the current density can be achieved compared to a out bond wires, PCIM Europe 2008 solution based on standard modules. Regulatory requirements in [3] C. Göbl: Low Temperature Sinter Technology Die Attachment for wind inverter applications have demanding requirements for the grid Power Electronic Applications, CIPS 2010 support like voltage and low frequency ride through conditions. The [4] T. Stockmeier, P. Beckedahl, C. Göbl,T. Malzer: SKiN: Double power module has to support these conditions with the ability to work side sintering technology for new packages, ISPSD 2011 in an overload or high voltage situation. With this module concept wind power inverter from 3MW onwards can easily be realized accepting the nacelle space limitations. This opens the 6MW+ market www.semikron.com

www.bodospower.com September 2012 Bodo´s Power Systems® 31 AUTOMOTIVE POWER

Solutions for On-Board Chargers All charged up

EPCOS and TDK components perform key functions in the Finepower’s on-board chargers for electric and hybrid vehicles. They include inductors, transformers, capacitors and protective components. By Cem Som, Development Transformers, EPCOS

Finepower - an engineering specialist for efficiency. In order to maximize the power Finepower uses the synchronous interleaved power electronics - has developed a highly drawn from the line, the charger must PFC process (Figure 1) in order to eliminate compact prototype of an on-board charger include active power factor correction (PFC). these drawbacks as much as possible. This (OBC). This device, based on specifications This rectifies the AC voltage from the power topology operates with two PFC stages con- and technical conditions of the German auto- line and simultaneously generates an inter- nected in parallel to the joint output, thus motive industry, delivers high efficiency at nal DC link circuit of 400 V DC that supplies already reducing by 50 percent the adverse the same time as high power density. Both the charging circuit. PFC circuits based on effect of only a single PFC choke carrying are important factors for incorporating OBCs the principle of the boost converter represent the whole load and thus also the ripple cur- into electric vehicles. The space-saving the state-of-the-art and are widespread. rent. Although the interleaved process design of the charging system was made requires two chokes, each of them can be possible by the development of a range of Sources of losses sustained in converting dimensioned for half the current (8 ARMS or application-specific chokes and transformers the power voltage in the 400 V DC link cir- 22 APK), leading to considerable simplifica- qualified to the AEC-Q200 specifications for cuit are: tion. A highly compact design from the newly reliability tests. • EMI filters (copper losses) developed e-mobility platform series of • Bridge rectifiers EPCOS PFC chokes is used for this purpose Well-protected power input • PFC chokes (Figure 2). An EPCOS B72220F0271K101 type varistor • Power switches (MOSFET) protects the power input of the converter • PFC diodes from overvoltages. A special coating signifi- • Other losses are incurred by components cantly improved the mechanical stability of such as the aluminum electrolytic capaci- the varistor for use in electric vehicles. The tors in the DC link circuit, the shunt etc. EPCOS B57364S1509M ICL is used to limit the high inrush currents. To ensure EMC and The conventional solution produces an effi- provide for EMI filtering, Finepower’s devel- ciency of between 96 and 97 percent at an opers opted for EPCOS standard chokes of input voltage of 230 V AC, depending on the kind also used in industrial power sup- design and optimization. At an input power plies. The B32933C3155M types from the of 3.65 kW, this means that between 110 EPCOS heavy-duty series of X2 capacitors and 146 W of this figure is converted to heat were selected, which are characterized by losses before it is available at the DC link Figure 2: EPCOS PFC choke from the new high reliability and a long service life. circuit. e-mobility platform Despite their compactness, these EPCOS The DC link circuit is stabilized by the chokes are rated for peak currents of up to B43508B5337M and B43504B5337M+ types 22 A. of EPCOS aluminum electrolytic capacitors. The EPCOS PFC chokes are very well suit- They provide a capacitance of 330 μF at a ed for this application, as their low volume, rated voltage of 450 V DC. TDK Mega Caps special core material and use of an RF of the CKG57NX7R2J474MT series are con- stranded wire for the winding produce low nected in parallel to them to reduce the losses. Figure 3 shows the principle of the ESR. This is the only way of keeping the DC superposition of both choke currents. link circuit highly compact despite the high Figure 1: PFC stage in the interleaved power density. process Measurements on the 230 V power line The parallel connection of two PFC branch- show that at 40 to 85 percent of the rated Special PFC concept boosts efficiency es with corresponding EPCOS PFC chokes load (1.3 to 2.8 kW), the efficiency of the In the development process, special atten- splits up the high ripple current load. This PFC stage exceeds 98 percent and reaches tion was paid to achieving maximum charger boosts efficiency and improves EMC. as much as 97.5 percent at full load (3.3

32 Bodo´s Power Systems® September 2012 www.bodospower.com AUTOMOTIVE POWER

kW). Compared with a conventional PFC LLC converters (Figure 4) benefit from the Apart from the load current, a significant part stage, therefore, power losses of between fact that this fully resonant topology always of the resonant current must also be trans- 35 and 70 W are saved in this first stage of permits sufficient energy to be stored in the formed in the LLC process, which leads to the OBC alone. load circuit to assure autonomous switching additional power losses not only in semicon- of the bridge nodes. ductor components but also in copper components (circuit board, resonance inductor, transformer). If a full-bridge circuit doubles the voltage on the primary side of the transformer compared to a half bridge, the current is halved. The increased transfer ratio leads to a higher copper resistance (linear) and the semiconductor sections exhibit double the RDS(on). Because the line losses are a Figure 4: Full-bridge LLC converter quadratic function of the current (PD=I2R), Figure 3: Superposed choke currents Finepower uses inductors from the EPCOS e- unnecessary power losses are avoided. The superposed choke currents produce an mobility platform in the full-bridge approximately sinusoidal current input from converter. This applies both for the resonance The full-bridge LLC concept in rated opera- the power line. inductor (LR) and the transformer (TF). tion (1.2 to 3.3 kW) permits an efficiency exceeding 97 percent to be invariably DC/DC converters with high efficiency Inductors from the EPCOS e-mobility plat- reached despite reliable separation from the Fed with a regulated and stabilized interme- form series are also used in the full-bridge power line. At the same time, the quasi-reso- diate circuit voltage of 400 V DC, the DC/DC LLC converter. The maximum output voltage nant full-bridge principle improves the EMC converter must supply the charging voltage is 420 V DC, i.e. in the same range as the properties. for the battery with reliable electrical separa- input voltage of 400 V DC. The transfer function from the power line. Depending on the tion of an LLC converter permits the voltage www.epcos.com design and charging state of the battery, the to be increased and reduced. A useful option range of possible output voltages of the is to operate with a transfer ratio of 1:1 in the www.tdk.eu OBC is set between 200 and 420 V DC. transformer, thus minimizing its losses. The Both the charging current and the final transformer on the primary side is operated charging voltage have to be programmable by a full bridge at ±400 V, which is converted and controllable via the communications back to 400 V DC after bridge rectification Contact for information on reference designs interface of the device (CAN bus). on the secondary side. or special applications:

In order to minimize the total losses of the [email protected] OBC, the DC/DC converter must also maximize its efficiency. Due to the need for reli- Type Ordering code Varistor EPCOS B72220F0271K101 able electrical separation in this switching ICL EPCOS B57364S1509M stage, however, its efficiency cannot be quite X-capacitors EPCOS B32936C3565M as high as in the PFC stage. At the current X-capacitors EPCOS B32936C3565M state of the art, the highest efficiencies are Y-capacitors EPCOS B81123C1682M attained in insulated DC/DC converters with Aluminum electrolytic capacitors EPCOS B435604B337M resonant bridge topologies. Either phase shifting converters or LLC circuits may be MLCC TDK CKG57NX7R2J474MT used for this purpose. In both of these, the Gate drive transformer EPCOS B82801C2245A200 transistors are always connected in when PFC choke EPCOS B78547P2176A005 Resonance inductor EPCOS B78547P2175A005 the drain-source voltage is zero and the Power transformer EPCOS B78547P2177A005 losses in the semiconductors are consequently very low. Table 1: EPCOS and TDK components in the on-board charger from Finepower

TOSHIBA DTMOS IV SUPER JUNCTION POWER MOSFETS: CHIPS WITH OPTIMISED RDS(on) x Qg AND MORE PACKAGE OPTIONS AVAILABLE The latest generation of Toshiba’s innovative family of DTMOS power MOSFETs is now available with a Vdss rating of 600V. The DTMOS IV makes your solutions more efficient, with easily controlled switching speed, achieved by optimising RDS(on) x Qg performance, enabling a more effective application design.

Our compact smart isolation TO-220SIS package with copper connector instead of standard wire bonds, along with the high-performance TO-3P(N) package, form the basis for the devices available, followed by TO-220 and the compact SMD DPAK package. Other compact package options will be available in the future. SCAN ME Visit us today at www.toshiba-components.com/power IGBT MODULES

Low Inductive Inverter Design Using a new power module concept

Increasing efficiency and lowering EMI are important goals for designing power electronic systems. To obtain this, the parasitic inductance of the current commutation loops is under focus. In this paper an overall low inductance module is shown which provides not only low inductance within the half bridge but also low inductance among half bridges itself, e.g. in a three phase inverter. The new module concept enables not only optimized 3 phase systems but also optimum performance of three level NPC (Neutral Point Clamped) inverters. By Xi Zhang, Daniel Domes, Reinhold Bayerer and Alexander Herbrandt, Infineon Technologies AG In power electronic systems fast transient in Three phase topology switches are turned on, respectively. Then, a voltage and current is the consequence of The low inductance half bridge module from freewheeling loop appears and the load cur- the basic functionality. High di/dt value at [1] seems to be an ideal candidate for realiz- rent is running free through transistors and current commutation in conjunction with par- ing a 3-phase inverter system. The superior diodes of either the top or bottom side. No asitic inductance induces voltage Vind switching behavior is the result of not only current goes into DC capacitors anymore across the parasitic inductance Lσ: optimizing the module but also the bus bar and all load branches are connected to the and the capacitor. Such an optimized half same potential (DC+ or DC-). After this zero (1) bridge system is shown in Figure 2 left, state, the modulator continues with non-zero schematically. As demonstrated in Figure 2 switching states and currents commutate Another disadvantage coming along with Lσ is right, the parallel arrangement of three of the from freewheeling paths into capacitors. the low resonance frequency of the resonant half bridge systems leads to a three phase circuit formed by the parasitic chip capacitance inverter. Often the interconnection between In Figure 3 an example for inter-half-bridge Cchip and the stray inductance Lσ: half bridges is not optimized for low parasitic commutation is shown in a simplified way. inductance. The target of the work in this Assuming that the DC-connection to the (2) paper is to eliminate the inter-half-bridge mains is not applied for the moment of com- inductance, as well. This requires an overall mutation, in the left picture a zero state is In Figure 1 a 1200V/400A low inductance strip line design for the whole inverter (3 half shown, whereas all top IGBTs are turned on. half bridge module shows of having only bridges) including DC-capacitor. Assuming further that the load current in the 5nH internal stray inductance, first presented middle and right half bridge is flowing into in [1]. Such low inductance value is realized the phase connection, the top diodes of the by strictly ensuring strip line design and cur- mentioned half bridges are conducting. The rent flows only in one vector plane. The con- sum of these currents is flowing out of the sequences is dramatically reduced over volt- phase terminal of the left half bridge, where- age peak and no ringing. as its upper IGBT is conducting. If the modulator continues with a non-zero state, the upper IGBT of the left half bridge can be turned off, for instance. Figure 3 right shows the situation directly after the IGBT turn-off. The stray inductance forces current flow Figure 2: Inductance-optimized half bridge although the IGBT is already turned off. In system (left) and conventional arrangement this example the consequence is that the of these half bridge systems for obtaining a energy stored in the stray inductance goes three phase inverter (right); from one half into the DC cap of the left half bridge. This bridge with DC-capacitor to the others stray effect is causing an overall higher RMS cur- inductance still exists rent of the DC caps compared to low stray Low inductance connection between half inductance design. Figure 1: Low inductance half bridge module bridges is relevant for commutation among enabling lowest parasitic inductance by hav- half bridges. This happens when the so Three-level-approaches ing line-wise DC-connectors enabling the called zero-state is set by means of the con- Three level NPC inverters are usually built continuation of busbar strip line even in the trol system of the inverter, for example. out of standard modules. Depending on the module Zero-state means that all top and bottom power factor of load different commutation

34 Bodo´s Power Systems® September 2012 www.bodospower.com IGBT MODULES

loops exist where two (short commutation) and even three (long commutation) half bridge modules are involved [2]. Therefore the low inductive connection from half bridge to half bridge is quite of interest, especially in 3 level application.

Figure 4: Three-phase concept module for lowest overall inductance

Figure 3: Simplified example for inter-half-bridge commutation in a 3- along the y-axis. The individual half bridges are carried by a second phase inverter with stray inductance in the half bridge to half bridge layer of DCB, which connects down to the first layer at each DC- connection and a pure inductive load; Left: inverter in zero state (all side. DC+ and Phase (Ph1 to Ph3) are brought up by means of a line upper IGBT gates are turned on, therefore marked as bold), current wise connector for each individual half bridge. Strip lines in the multi- coming from middle and right half bridges is going through upper layer DCB and above the chip layer result in an overall low induc- IGBT in the left half bridge; Right: upper IGBT of left half bridge is tance inverter. turned off because modulator continues with non-zero-state, energy stored in parasitic load inductors is going into left DC-link capacitor Conclusion For three phase systems and three level NPC topology the low Proposed Solution inductive connection of individual half bridge circuit is important. A Low inductance commutation loops between half bridge systems can new module concept is demonstrated which combines properties, be arranged by strictly following the principles mentioned in [1]. reducing the stray inductance while fulfilling the need of current flow- These are ing in the y-z-plane of Fig. 4. Following this design leads to an overall reduced inductance, excellent current sharing and lowered RMS cur- Consequent realization of strip line conductors without interrup- rent at the DC capacitors. tions in geometry Arranging the commutation current flow always in y-z-plane (see References example in Figure 1) [1] Reinhold Bayerer, Daniel Domes: Power Circuit design for clean switching. CIPS 2010, Nuremberg, Germany. The outcome of that is a module concept as shown in Figure 4. This [2] Zhang Xi, Uwe Jansen, Holger Rüthing: IGBT power modules uti- approach combines three half bridges, within each half bridge the lizing new 650V IGBT3 and Emitter Controlled Diode3 chips for chips are paralleled along the x-axis. Three half bridges are arranged three level converter. PCIM Nuremberg 2009, Germany. behind each other along the y-axis. To achieve lowest inductance throughout the whole arrangement of 3 half bridges a multilayer DCB is used. It allows a DC- layer over the whole length of the module, www.infineon.com/high-power THERMAL MANAGEMENT

Energy Efficiency and Design Freedom of Busbars Improvement of thermal optimization and increase reliability

Busbars are energy highways that can be customized to ensure the current energy flow between the power source and the capacitors, resistors, integrated circuits, IGBT’s or complete modules. Recently, however, busbars have been faced with increasing performance requirements, such as constant demand for higher ampacity which may cause increased strain on the circuits resulting in increased heat generation. By Koen Hollevoet, Business Opportunity Analyst, Rogers

In typical PCBs, the heat is virtually enclosed by multiple layers and Where three-dimensional compatibility is needed, PCBs also have conductors that may result in damage to the material. To enable the limits. Due to their flat design, it is costly and complex to mount addi- heat caused by the electric load to be dispersed quickly and easily, tional components. The new busbar circuit from Rogers, however, is Rogers Corporation (Rogers) has developed RO-LINX® PowerCir- designed specifically for 3D compatibility: cuit™ Busbar. This new offering in the RO-LINX® Busbars series of copper conductors laminated with a thin insulation layer provides a new level of thermal management for PowerCircuits that can double their life-span.

As the maximum thickness of copper for PCBs is merely 400 ìm, they can only be used for amperage up to 100 A. Standard busbars, on the other hand, have a copper thickness of at least 800 ìm and are effective from amperage of 500 A upwards. Consequently, a gap between 100 and 500 A exists that cannot be served by either standard PCBs or busbar circuits. The same applies for copper thickness between 400 and 800 ìm. In order to fill this gap, Rogers developed the RO-LINX® PowerCircuit™ Busbar that spans these ranges and provides a solution for the increased demand for higher ampacity and energy efficiency. RO-LINX® PowerCircuit™ Busbars are already solving these challenges in electric and hybrid cars for electricity Figure: RO-LINX® PowerCircuit™ busbars are 3D-compatible and transformation, in solar inverters and in variable frequency motor can be wave soldered. drives. Source: Rogers Corporation

3D-compatible busbars allow integration of planar transformers The RO-LINX® PowerCircuit™ Busbar is an all-in-one circuit that eliminates the need to mount additional pieces of conductor. The Company’s new busbar avoids additional connections that can result in interconnection losses, additional assembly time, potential risks of production errors and failures in the field.

Commensurate to the number of connections, the number of hotspots and the costs of assembly can be reduced. The same applies to the connection of busbars to high-power components.

High-power components mounted on busbars are typically bolted in place, which is a time consuming connection method. In wave soldering, multiple connections are made in one process with little if any intervention of an operator. It is easy to calculate the positive impact on your assembly cost if you need to assemble many thousands of units. Figure 1: The integration of high power planar transformers in RO- LINX® PowerCircuit™ Busbars enables compactness and improves In addition, the 3D-compatibility of the new busbars allows the inte- electric efficiency. Source: Rogers Corporation gration of further functionalities within one circuit. Here, one often

36 Bodo´s Power Systems® September 2012 www.bodospower.com THERMAL MANAGEMENT

faces challenges like hot spots due to contact resistance and The integration of the transformer into the RO-LINX® PowerCircuit™ extreme power densities or the limited mechanical space. These Busbar also positively affects the compactness and the thermal occur where the secondary circuit of the transformer has to be con- behavior of the transformer. Thanks to the connection with the circuit nected to a circuit with amperages between 100 and 300 A, as is and the larger surface area resulting from it, the heat from the trans- often the case with DC-DC-transformers in electric vehicles. With the former can easily be removed and extracted through convection or possibility to integrate the planar transformer into the PowerCircuit, conductive cooling of the circuit. Consequently, the transformers, as most mechanical problems can be solved. Since the transformer well as the RO-LINX® PowerCircuit™ Busbars, provide an ideal heat does not need to be bolted or soldered, contact losses are avoided management solution that enhances the life-span of busbars and and energy efficiency increases. ensures that they run as energy efficiently as possible.

Rogers Corporation (NYSE:ROG) is a global technology leader in specialty materials and components that enable high performance and reliability of consumer electronics, power electronics, mass tran- sit, clean technology, and telecommunications infrastructure. With more than 180 years of materials science and process engineering knowledge, Rogers provides product designers with solutions to their most demanding challenges. Rogers’ products include advanced circuit materials for wireless infrastructure, power amplifiers, radar systems, high speed digital; power electronics for high-voltage rail traction, hybrid electric vehicles, wind and solar power conversion; and high performance foams for sealing and energy management in smartphones, aircraft and rail interiors, automobiles and apparel; and other advanced materials for diverse markets including defense and consumer products. Headquartered in Connecticut (USA), Rogers operates manufacturing facilities in the United States, Belgium, Figure: RO-LINX® PowerCircuit™ Busbars are a solution for the China, Germany, and South Korea, with joint ventures and sales growing demand for higher ampacity while addressing energy effi- offices worldwide. ciency at the same time. Among other applications, these new busbars are used for electric and hybrid cars, solar inverters and variable www.rogerscorp.com frequency drives. Source: Kurt F. Domnik, pixelio.de (public domain) www.ro-linx.com Press-Pack IGBTs - where MegaWatts matter Multiple power options

Features Applications Type VCES IC sFully hermetic compression bonded encapsulation s MV Drives Part No. V A - Ø47mm to Ø125mm pole face industry standard outlines - Marine drives T0160NB45A 4500 160 - Increased power density - Traction T0340VB45G 4500 340 T0360NB25A 2500 360 - Double side cooling - Wind power converters T0570VB25G 2500 570 - High thermal cycling capability - Industrial T0600TB45A 4500 600 T0800EB45G 4500 800 - Simple series connection T0900EB45A 4500 900 - Enhanced rupture rating s EnergyE Utilities T1200TB25A 2500 1200 T1600GB45G 4500 1600 packages available - STATCOM T1800GB45A 4500 1800 - FACTS

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- Renewable generation Part No. V A T0240NB45E 4500 240 T0500NB25E 2500 500 T0510VB45E 4500 510 T0800TB45E 4500 800 For full productproduct information please visit; T0850VB25E 2500 850 http://www.ixysuk.com/prodpf.htmhttp:///www.i T1200EB45E 4500 1200 andand download Press-Pack IGBT brochure. T1500TB25E 2500 1500 T2250AB25E 2500 2250 T2400GB45E 4500 2400 www.ixys.com www.ixysuk.com Efficiency For small volume enquiries, use the extensive IXYS Distribution Network, details via our websites: Through USA: FAR EAST: EUROPE: IXYS Long Beach IXYS Taiwan IXYS UK Westcode Ltd Technology Tel: +1 (562) 296 6584 Tel: +886 2 2523 6368 Tel: +44 (0)1249 444524 e-Mail: [email protected] e-Mail: [email protected] e-Mail: [email protected] DC/DC CONVERTER

High Speed, Two Quadrant DC/DC Power Supply The main function and benefit of synchronous rectification

To enable a converter that modulates output voltage and that generates voltage according to some predefined wave form, whilst keeping the efficiency high, is only possible using a high speed two quadrant DC/DC power supply. By Milan Marjanovic, Texas Instruments

A two quadrant DC/DC power supply has bi-directional power flow- This third capability is also very important. A system with synchro- forward, where the power flows from source to load - and reverse, nous rectification does not need the minimum load to work in continu- where the power flows from load to source. This article describes ous conduction mode (continuous current flow in the storage choke). how to make such a power supply using simple techniques. Because of the ability to pull the current back, the duty cycle remains constant for the entire load range. While always working in continu- One or Two Quadrant Power Supply? ous conduction mode, we can make a converter with a very good As shown by the blue line in Figure 1, a single standard power sup- huge load step transient response. The worst case scenario for each ply is able to deliver only positive voltage and positive current in a power supply is load transition from no load to maximum load and forward direction. We call this kind of power supply a one quadrant from maximum load to no load; as shown in the figure 2: power supply. If there is the possibility for reverse power flow – as indicated by the red line, then we are talking about bi-directional or, two quadrant power supplies. In this case the voltage is again only positive, but the current can be positive and negative.

Figure 1: One or Two Quad- rant Power Figure 2 – Example of the huge load step (0A->10A->0A) Supply As can be seen, the system is pushing more current to the output to From this point we will talk only about Two Quadrant Power recover the voltage drop (marker M1), but it is pulling the same Supplies - TQPS. amount of energy back (marker M2) to block and reduce the voltage The basic and best example for TQPS is the synchronous buck con- overshoot. verter. Many power engineers make the big mistake of not properly understanding synchronous rectification. They regard synchronous Full bridge phase shift topology and synchronous rectification rectification as high efficiency. The biggest advantage, however, is Full bridge phase shift topology - zero voltage transition - is becom- pure bi-directional power flow; capability both to push the current to ing more and more popular. The main competitor is a full bridge hard output and to pull the current back. We will see that this capability is switching topology. There are a few main differences between the directly reflected in a much better load step response - better dynam- two listed in Table 2. ics on the output. This kind of dynamic would never be possible with a standard buck converter – buck with a diode rectifier (free wheeling diode). To summarize, the table 1 shows the three important advantages of the buck converter using synchronous rectifier technique versus a diode rectifier approach.

Table 1: Three important advantages of the buck converter using Table 2: Full bridge phase shift topology versus synchronous rectifi- synchronous rectifier technique versus a diode rectifier approach cation

38 Bodo´s Power Systems® September 2012 www.bodospower.com

DC/DC CONVERTER

From this point of view, we can say that for low voltage applications bridge driver with a boot strap diode. For the full bridge topology we (<100V, e.g. telecoms) there is no benefit on the power stage using already need two such symmetrical circuits. If we have a synchro- phase shift topology. The main reason for using it is much simpler nous rectification on the secondary side we need to transfer addition- and more optimized gate driving; also no high frequency ringing on al PWM signals across the isolation barrier. This can be achieved the switch node, which can indicate better EMI performance. Talking again using a transformer or, digital isolators (ISO7920) or, an high about high voltage design (400V range), performance is more effi- speed optocoupler. We also need to close the feedback loop across cient, which is a good enough reason to go straight forward with this the isolation barrier, usually again with an optocoupler. The optocou- topology. The picture 3 demystify the full bridge phase shift principle. pler has a low pass behaviour, very long turn on and turn off delay times, huge CTR tolerance, aging issues and for some applications (e.g. automotive and military) is not even allowed.

To increase the frequency band width of the feedback loop, to increase the reliability and save the costs of the system we can set up as shown in Figure 4.

Figure 3: The drawings demystify the full bridge phase shift principle

The gate signals for phase A and B are inverted to each other; they have the same duty cycle of 50% and the same period. Therefore the leg (A, B) is either connected to VIN or to ground. The same holds for phase C and D as well as for leg (C, D).

The picture bottom left shows the voltage across the primary, marked Figure 4: Set up to increase the frequency band width of the feed- red, when the phase shift between leg (A, B) and (C, D) is zero back loop, to increase the reliability and save the costs of the system degrees. In this case, both sides of the transformer are connected, either to VIN or GND. As no voltage is applied to the transformer, the The controller is placed on the secondary side providing the possibili- output voltage of the transformer is also zero and therefore no cur- ty of closing the feedback loop without need for an optocoupler. The rent flows. signals for synchronous rectification are now on the same ground potential as referenced by the controller itself (no need for expensive On the top right side the waveforms for a 90 degree phase shift are digital isolators). The signals which now cross the barrier are bridge shown. The waveform for leg (A, B) remains the same, but the wave- PWMs and current sensing. As stated, we can use the gate trans- form of leg (C, D) is shifted for 90 degrees,. Now, for the first quarter formers for gate driving. When they are used, galvanic isolation is of the period a positive voltage is applied to the transformer. This free. Designers have to take care with the isolation voltage needed. generates a voltage on the secondary side and causes a current. The same is true for the current sense transformer. This kind of setup During the second quarter, VIN is applied to the transformer on both has, unfortunately, one drawback: it needs a galvanic isolated auxil- taps, so the primary is now shorted and there is no voltage on the iary power supply providing voltage to the secondary side. Without secondary side. At the third quarter, a negative voltage is applied to this voltage the converter could never start. The synchronous rectifi- the transformer, which again generates a negative voltage on the secondary side. On the secondary side the voltage is rectified as shown by the hatched rectangles. At 90 degree phase shift the total duty cycle is thus 50%.

If the phase shift is increased further, the duty cycle on the secondary side is increasing therefore output voltage rises. The maximum output voltage is achieved at a phase shift of 180 degree and results in a duty cycle of 100% on the output, as shown on the picture in the bottom right corner.

Further improvements of the loop bandwidth on galvanic isolated systems Normally the controller sits on the primary side, generating PWM signals for the switching elements. Having already started with a half bridge topology, we need a special drive for a high side switch. Because of a floating switch node point the gate drive is floating as well; accordingly, for low and mid power range power supplies we Figure 5: No load conditions have the possibility of either a gate transformer or integrated half

40 Bodo´s Power Systems® September 2012 www.bodospower.com cation that we can see here makes this converter bi-directional (two quadrant power supply). In picture 5 we can see the right and left leg of the full bridge rectifier at the secondary side. The green wave shows the storage choke current. As can be seen, the current remains continuous as does the duty cycle.

Applying the load at the output shifts this green line over the y axis. This can be not only in a highly positive direction, but also as stated, in a highly negative direction. The duty cycle changes only during the load transitions. In steady state condition the duty cycle remains constant for the entire load range.

Summary We discussed bi-directional power supply definition, synchronous buck converter and the basics of full bridge phase shift topology. We have seen in a practical way what the main function and benefit of synchronous rectification is and how to use it in isolated systems. The layout and the position of the controller in the system play a big role as well. This all opens the door to making high speed power supplies. In the following article “Using bidirectional power supply to modulate voltage on the output” we talk further about power stage; sensing techniques and choosing the right regulation methods for bi- directional power supplies.

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ss www.bodospower.com September 2012 Bodo´s Power Systems® 41 POWER SUPPLY

Total Solution for Energy Efficient Home Appliance Power Supply Energy efficiency is crucial to both consumers and environment

As much as half of the energy used in home goes to heating and cooling. So making smart decisions about heating, ventilating, and air conditioning system can have a big effect on utility bills. Saving energy at home also can help to protect the environment. It is at this critical moment that semiconductor suppliers are playing an important role in developing technologies that improve energy efficiency. By Won-Seok Kang, Senior Application Engineer; Fairchild Semiconductor

Introduction over-current protection, internal thermal shutdown with hysteresis, Most industry experts agree that motor control, lighting, computing, pulse-by-pulse current limit, and output short protection. These and power supplies are areas where new power technologies can advanced protection functions ensure reliable operation of the con- have a significant impact on energy consumption. The combination of verter. It also offers random frequency fluctuation for low EMI as improved products with an in-depth understanding of systems and shown in Figure 1. The amount of EMI noise is directly related to the applications can result in solutions that maximize efficiency. By switching frequency. In the FSL176MRT, the operating frequency is reducing wasted energy, tremendous energy savings can be realized determined randomly by external feedback voltage and internal free- without sacrificing consumer choice. In this article, total solution for running oscillator at every switching instance. Therefore, EMI noise is home appliance power is proposed. By combining the state-of-the-art spread around typical switching frequency and can be reduced. It is technologies, best-in-class switched-mode power supply is designed also possible to reduce the cost of the input filter required to meet the and it gained huge interest from system designers. This article EMI regulations such as EN55022. describes the features and benefits of each product and shows board level evaluation results. Synchronous Rectifier Controller FAN6204 is a secondary-side synchronous rectification controller to Flyback Converter I.C drive synchronous rectification MOSFET for improved efficiency. It The FSL176MRT is an integrated pulse width modulation (PWM) utilizes an innovative linear-predict timing control to determine the controller and SenseFET specially designed for offline switched- turn-on and turn-off instances of synchronous rectification MOSFET. mode power supplies with minimal external components. The PWM This control technique detects the voltage of the transformer winding controller includes an integrated fixed frequency oscillator, under-volt- and output voltage instead of current flowing through the MOSFET. age lockout, leading edge blanking, optimized gate driver, internal Therefore, better noise immunity can be guaranteed. In addition, this soft start, temperature-compensated precise current sources for loop compensation, and self protection circuitry. The protection functions it provides are over-load protection, over-voltage protection, abnormal

Figure 1: Random frequency fluctuation to reduce EMI Figure 2: Trench MOSFET with added shielded electrode

42 Bodo´s Power Systems® September 2012 www.bodospower.com POWER SUPPLY

technique does not require a communication signal from the primary System Performance side so can reduce external components and simplify board layout. It The Fairchild solution is evaluated in a 40W rated multi-output also provides various protection functions for abnormal conditions. switched-mode power supply. It has 4 outputs and main output is Fault causal timing protection, gate expand limit protection, and RES 13.2VDC, 2.8A. Others are two 5V and 15V outputs rated at 0.1A dropping protection are used for load change. LPC and RES pins’ each. This is typical configuration for mainstream refrigerator power. open/short protection is provided to prevent fault operation of the Fig. 3 shows system efficiency of two solutions. The proposed solu- controller when resistors connected to LPC or RES pins are dam- tion shows better efficiency over entire load range compared to exist- aged. Internal over temperature protection and Vdd over voltage pro- ing competitor solution at 220VAC input. It provides similar efficiency tection are also included. It is also equipped with mWSaverTM tech- at 115VAC input. It should be noted that the proposed solution offers nology that stops switching in green mode to improve no load or light very good light load efficiency that is becoming great concern in the load efficiency. Power consumption is kept minimum level in this con- industry. Fig. 4 shows peak voltage across the primary switching dition. device. The proposed solution shows much lower voltage spike that is related to both system reliability and power loss in the snubber. PowerTrench® MOSFET The test also verified operating temperature of major components The trench gate MOSFETs are the most preferred power devices for can be lowered with the proposed solution. medium to low voltage applications. The new mid-voltage power MOSFET, PowerTrench®MOSFET is highly optimized for synchronous rectification. It employs a shielded-gate structure, where the shield electrode is connected to the source as shown in Figure 2. The shield electrode, along with the thicker oxide between electrode and drift region, provides charge balance for drift region. This enables the use of higher doping in the drift region, resulting in reduced drift resistance. The specific resistance of MOSFET has been significantly improved compared to the previous generation.

This very low RDS(ON) directly reduces conduction loss of synchronous rectification MOSFET. During light load conditions, conduction losses are minimal, and the driving losses are even more important. A gate charge parameter is the most important factor for the driving loss in power MOSFET point of view. The MOSFET has less than half of gate charge value compared to conventional trench MOSFET and can dramatically reduce driving loss at light load condition. Apart from RDS(ON) and gate charge, other parameter, such as like the body Figure 4: Voltage spike at 265VAC input, full load condition diode reverse recovery charge (Qrr), internal gate resistance and the output charge of the MOSFET (QOSS) are now becoming more relevant in synchronous rectification. The importance of these loss com- Conclusions ponents rises at higher switching frequencies. The switching loss in The refrigerator is powered up 24 hours, 7 days and therefore energy the synchronous rectification MOSFET is defined as below equation. efficiency of the appliance is crucial to both consumers and environment. Fairchild provides leading technologies for primary switch, sec-

Psw= (Qrr-Qoss)*Vds*fsw ondary controller, and power device. The combined solution demonstrated superior system efficiency. It is clear that smaller reverse recovery charge of body diode is really important to better efficiency. The MOSFETs are now being optimized to minimize the reverse recovery charge of body diode. www.fairchildsemi.com

Figure 3: System efficiency test results

www.bodospower.com September 2012 Bodo´s Power Systems® 43 TECHNOLOGY

eGaN® FET Safe Operating Area Rugged eGan FETs demonstrate superior save operating area

A basic limitation of a power transistor is temperature. Calculations of device temperature during operation assume that power dissipation is spread evenly over the entire active area of the device, which is not always true. Because of negative temperature coefficients in certain parameters of some technologies, current may crowd into a small area, pushing up the localized temperature until failure. By John Worman and Yanping Ma, Efficient Power Conversion Corporation

Safe Operating Area (SOA) curves describe FETs showed the theoretical SOA, which EPC’s Gallium Nitride Solution to the range of voltage and current and the was okay since the small area of negative Improved SOA Performance: length of time under which a device may temperature coefficient did not present an Figure 1 represents the transfer characteris- operate without failure. The SOA is an indi- additional limitation to voltage, current and tics of the EPC2001 eGaN FET, a 100 V, 7 cator of the device’s ability to transfer heat temperature. The modern MOSFET, howev- milliohm device, compared with the away from a resistive junction and, thus, is er, has a significant area of negative temper- BSB056N10NN34 power MOSFET from Infi- directly dependent on a device’s Thermal ature coefficient in its transfer characteristics neon. What is immediately obvious is that

Resistance (RθJC). The more efficient a curve with a high zero-tempco point. If this the temperature coefficient of the eGaN FET device is at getting rid of generated heat, the point is higher than the device’s operating is positive throughout its range of operation.

lower RθJC and the better the SOA perform- current, the device will tend to “run-away” This means that when the temperature of a ance. thermally at the higher SOA power condi- localized region of the device increases, its tions1,2. This thermal run-away condition is current carrying capability is reduced caus- eGaN FETs from Efficient Power Conversion due to what has previously been labeled ing the current to be dispersed to other (EPC) exhibit a positive temperature coeffi- thermal focusing3. Therefore, the solution to areas of the die. This dispersion of the cur- cient across their entire operating range and improving SOA performance is operating the rent equalizes the temperature of the die, can therefore be expected to operate with MOSFET above the zero-tempco point. and is known as “self-ballasting.” The power only voltage, current, and temperature limita- While many manufacturers still show theo- MOSFET, on the other hand, has a signifi- tions. This article will describe the theoretical retical SOA, some are now quantifying their cant region of negative temperature coeffi- SOA of power eGaN FETs which demon- results with empirical data and displaying the cient operation (below 5.0 V on the gate) strate very good SOA characteristics while limitations that this operating condition pro- where there is no self-ballasting. Operation

maintaining superior RDS(ON). The article will duces. within this region creates localized hot spots then compare theoretical calculations with within the die and, thus, limits the SOA capa- measured results. bility of the die.

History: The Safe Operating Area of a power device describes its ability to handle voltage and current simultaneously while the gate voltage is at or just above threshold. Limits on SOA are typically due to a negative temperature coefficient which causes current crowding. An example of this crowding is sometimes seen in the base emitter junction in bipolar junction transistors (known as second breakdown).

Early power MOSFETs had significantly lower current where the transfer characteristics’ temperature coefficient transitioned from negative to positive (zero-tempco point). Cell densities in today’s devices have increased which improve the device’s on-resistance

(RDS(ON)). Most datasheets for early MOS- Figure 1: EPC2001 (left) and BSB056N10NN3 (right) transfer characteristics

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Figure 2 shows the safe operating area of the EPC2001 eGaN FET Referring to figure 2: compared with the same MOSFET from Infineon (BSB056N10NN3). 1. The RED line shows failure data when the device was linearly The EPC2001 eGaN FET boundaries of the SOA curve are 100 V biased under DC conditions. (the absolute maximum drain to source voltage), and 100 A (the 2. The BLUE line shows failure data when the device was linearly absolute maximum pulse current). Within these boundaries, the tran- biased for 100 milliseconds. sistor can operate for a limited amount of time before its thermal limit 3. The GREEN line shows failure data when the device was linearly is reached. biased for 10 milliseconds.

Figure 2: EPC2001 (left) and BSB056N10NN3 (right) Safe Operating Area

The top left portion of the graph cannot be reached because the As shown, the 10 millisecond, 100 millisecond and DC failures all

RDS(ON) is too low to generate the voltage at the given current. occur at higher power levels than the published SOA conditions. Between the two boundary conditions exists a set of sloping lines that show SOA limitations as a function of a timed rectangular power Conclusion pulse. The black lines are calculated constant power lines represent- High electron densities and very low temperature coefficients give the ing the energy it takes to raise the device junction temperature to the eGaN FET major advantages over the power MOSFET needed for maximum rated junction temperature while maintaining a constant today’s high performance applications. High electron density yields

25°C case temperature. These black lines typically have a slope of superior RDS(ON), while positive temperature coefficients inhibit hot minus 1 (constant power: log(IDS) = log(PD)-log(VDS)) at VDS = spot generation within the die, resulting in superior Safe Operating (IDScontinuous)(RDS(ON)). Area capabilities. An additional benefit for eGaN FETs emerges when parallel devices are mounted onto a common heat sink. Due to their While the positive temperature coefficient over the entire operating areas of positive temperature coefficient above the zero-tempco, they range of the EPC2001 eGaN FET leads us to believe that the theo- tend to current share, thus reducing the requirement for ballasting retical thermal limits bound safe operation, due diligence for a young resistors. technology drives us to verify this condition empirically to ensure that other failure modes are not overlooked. Twenty-five units of References: EPC2001 were taken to catastrophic failure where each device was [1] Worman, J., "New Generation Power MOSFETs and Safe Oper- clamped to a water-cooled heat sink; the case temperature was ating Area" PCIM proceedings, Chicago, 2002. maintained at +25°C, ±2.5°C. [2] Schoiswohi, J., "Linear Mode Operation and Safe Operating Area of Power-MOSFETs," Applications Note, AP99007, Infineon, V0.92, 2010. [3] Ronan, H. R., Jr., "Thermal Current Focusing in Power MOS- FETs" PCIM, Aug. 1998. [4] http://www.infineon.com/dgdl/BSB056N10NN3+G_Rev+2.5.pdf? folderId=db3a304313b8b5a60113cee8763b02d7&fileId=db3a304 42e152e91012e390b9a631459

www.epc-co.com

46 www.bodospower.comBodo´s Power Systems® SeptemberSeptember 2012 2012 Bodo´s www.bodospower.com Power Systems® SCOTTSDALEOTT INTELEC® 2012 Conference and Exhibition

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Optimizing Three-Phase Planar Transformer Construction Production costs are reduced as well as transformer efficiency is increased

A three-phase transformer with flat conductor layers is proposed in this article. This arrangement is used for high current density transformers. Cost effectiveness in planar magnetic are related with the optimization in the number of layers in each winding. This fact takes more relevance for the medium and high power three-phase transformers where the number of parallels to achieve the required DCR is increased. The proposed method allows the use of off-the-shell core shapes that are used for single phase transformers. Cost impact is significant and design implications become more flexible. The proposed solution has been validated and compared using the conventional and the proposed methodologies to design a high power (20 kW) transformer.

By R. Prieto, R. Asensi, O. García, J. A. Cobos, Universidad Politécnica de Madrid, Centro de Electrónica Industrial (CEI). Madrid and F. D. Gerez Premo Group. Barcelona, Spain Planar transformers for three-phase applications are mainly used to Method is explained in two sections described as follows: handle medium to high current levels. If current value is high then a • Section II includes the description of a conventional winding layout. number of parallel windings must be added to reduce resistance, A particular transformer is designed in order to be used as refer- consequently losses and temperature rise in windings are minimized. ence for comparison. Planar transformers have been conceived as a ordered stacking of • Section III describes the proposed alternative. The transformer copper frames. Sometimes these frames are embedded in a fiber included in Section II is modified in order to obtain a design with glass laminate that provides mechanical stability and allows through lower number of conductor layers for each block. the printed circuit technology to connect them. Sometimes these frames are separated by a polyimide layer and connection is done by Conventional Winding Setup adding a solder alloy material. Manufacturing process might become A conventional approach to build a three-phase transformer is based not feasible due the board size and conductor copper thickness. Not on the placement of each of the single-phase windings at each core feasible in terms of prices or due to metallurgical issues that avoid a leg. The same idea can be followed to build a planar component. The reliable joint in the connections. This feasibility is conditioned to the only difference is that conductor layers are used instead of rounded number of conductor layers. The problem to be solved is related to wires. the manufacturing process of three-phase planar transformers. In particular, it is oriented to reduce the number of conductor layers in A simplified representation of a conventional three-phase transformer this kind of transformers. Additionally proposed alternative improve is shown in Figure 1. Each white box (A-A’, B-B’, C-C’) is a single- the electrical performance of the final component. This work presents phase transformer and therefore includes a primary and a secondary an alternative method to design the three-phase planar transformer winding. Using this configuration, each column of the transformer with the same electrical features than the conventional ones but behaves as a single-phase transformer. reducing the number of conductor layers for each block.

A A’ B B’ C C’

Figure 1: Conventional three-phase transformer with planar windings Figure 0: Planar Transformer

48 Bodo´s Power Systems® September 2012 www.bodospower.com

TRANSFORMERS

The configuration shown in Figure 1 allows the use of low-profile The advantage of this construction is that transformers with a very cores. If a conventional core is used instead of a planar core due to large number of conductor layers, which could not be built using the low-profile version availability or to the required power drive then it is conventional method, can be fabricated using this modified structure. appreciated that transformer windings do not fill the whole window height since the high number of layers needed might make difficult, If electrical requirement are preserved then conductor layer section is expensive, and even not feasible the fabrication of that conductor obtained and as a result number of parallel windings might be layers stacking. reduced approximately two times because of the available section of the tracks in the proposed alternative is approximately twice the one Since each winding is placed at each leg of the core, one of the limi- of the conventional one. tations of this configuration is that the maximum track width (see Fig- ure 1) is approximately half the window width. As this fact fixes the Another characteristic of the proposed alternative is the possibility of maximum conductor section for each winding number of parallel using standard commercial cores that are commonly used for single- windings must be increased to achieve the required resistance value. phase transformers. Since the input voltages are equal but shifted 1/3 of the period, the fluxes are also equal and shifted 1/3 of the peri- Printed Wiring Boards (PWB) manufacturers provide technical limita- od. As a consequence of that, the secondary voltages are equal and tions of their capabilities for manufacturing the multi-layer stacks. sifted 1/3 of the period. Since the central and lateral legs of standard Additionally, PWB blocks cost increases drastically with the number EE and EI cores have different sections, flux densities differ. Howev- of the layers and the copper thickness. It is a common practice to er, there is no need to use custom-made core shapes because the create stacks of multi-layer PWB blocks in order to reduce the cost output voltages are balanced. and make cost-efficient and feasible the manufacturing process. But even applying this practice, there is a limit of layers that make feasi- The high power transformer presented in Section II has also been ble the manufacturing process for each specification. designed using the proposed layout to illustrate the advantages of this solution. Again, it is assumed that the maximum number of layers For a 20kW, 820V/300V 40kHz transformer with planar windings a is limited to 96 per single-phase transformer. The simulation with the PWB structure of 96 layers was necessary to achieve the electrical FEA tool has also been performed for this configuration in order to constraints and considering that copper conductor thickness were compare the results with the conventional structure. The conductor 70μm. In terms of dimensions this implies that a 17mm thickness power loss at each core leg (PC, PL, and Ptotal) and temperatures multi-layer PWB might be processed one per each single-phase. (TC, TL) obtained for this configuration are shown in Table 2.

PC (W) TC (ºC) PL (W) TL (ºC) Ptotal (W) The designed transformer was simulated using a Finite Element 38 48 49 55 136 (FEA) tool in order to obtain the loss and the temperature values. The goal of the simulation is to have available parameters for com- Table 2: Results for the proposed solution parison between the conventional winding setup and the proposed Comparing tables 1 and 2, it can be seen that an important 35% loss one in terms of electrical performance. Table 1 shows the conductor reduction and associated temperature rise. This is a specific advan- loss of the central (C) and lateral (L) windings (PC, PL) and their tage of this particular case because the room availability of the con- temperatures rise (TC, TL), obtained with FEA tool. Total losses Pto- ventional design. tal are calculated as 2 PL + PC. However, the main benefit of the proposed alternative is the possibili- PC (W) TC (ºC) PL (W) TL (ºC) Ptotal (W) 64 64 73 70 210 ty of reducing the number of conductor layers. In other words, for same power loss model obtained in Table 1 (conventional design), Table 1: Results for the conventional solution the proposed alternative could be designed with approximately half of Proposed Winding Setup the layers for each winding. An alternative for the winding setup is shown in Figure 2, where each winding occupies the whole window width. This makes possible to In order to illustrate this advantage, a “non feasible” design using the increase of the track section, reducing the resistance, the power loss conventional winding setup (presented in Section II) was calculated and the temperature using the same limitation for the maximum num- using a number of layers above the maximum feasible one, filling ber of layers of each single-phase transformer. most of the window height. In particular, a design with two times the number of conductor layers per winding (192 layers) was considered. The whole window height is filled because the central leg single- This design was calculated assuming that the non low-profile core phase transformer is placed above the lateral ones. It is assumed was used and therefore there is room enough in the window to place that the maximum number of layers for each single-phase trans- this number of layers. Using the FEA tool, table 3 shows the results former is the same than in the conventional case (96 for this particu- obtained in this case. lar example). PC (W) TC (ºC) PL (W) TL (ºC) Ptotal (W) 33 45 43 52 119 Table 3: Results for the conventional solution with double number of B B’ layers “Non-feasible design” It can be seen that the proposed solution presents power losses of A A’ C C’ 136W instead of 119W of this “non feasible” conventional design, but using half number of layers (96 instead of 192 layers). As mentioned before, this high number of layers makes not feasible the fabrication of the 192 layers solution because of interconnections between lay- Figure 2: Proposed three-phase transformer with planar windings ers.

50 Bodo´s Power Systems® September 2012 www.bodospower.com In an industrial perspective, PREMO, that has been developing planar transformers in two main technologies: Multilayer PWB and multi- stack of copper frames of different thickness according the constraints that frequency and proximity effects allow.

The first type is solved for the high frequency range using copper laminations from 2oz. to 6oz. and with a maximum PWB thickness of 3.7mm in order to allow automatic selective soldering in a wave solder machine process or a paste in pin technology. Depending on the copper thickness, number of layers is varying from ten to sixteen. If needed more layers a multilayer stack of two or more multilayer PWBs should be placed. This kind of stacking carries out a complex engineering process for automatic soldering that includes tin alloy selection (normally a lead free tin with some additives like Ni or Ge to allow a reliable soldering according IPC A-610 E standard) and a complex system of tooling and jigs for automatic connector insertion. An additional constraint for this part is size. A big part will need a high temperature exposure to ensure good thermal behavior during soldering and a thermal protection to the soldering heat while it is being mounted.

The second type is solved up to the limit of 125 kHz applications using copper frames from 0.25mm to 0.60mm separated by polyimide isolation frames and connected among them through a manual selective soldering process. There is a wide range of options that Premo has been using: selective soldering that uses a robot arm that dispenses the tin wire while pressing the copper stacking, ultrasonic soldering process that do a direct joint between two copper frames, step by step or induction soldering that heats tin balls in the joint to the melting temperature allowing a simultaneous soldering. Limit for this kind of structure is the number of turns per layer because it is a challenge to preserve the distance between tracks if they are reduced so much even that technique has been refined like a register process in PWB manufacturing.

Conclusions This work presents an alternative to reduce the number of layers for each winding in planar three-phase transformers. An industrial partner that manufactures planar transformers has participated in the val- idation of this work, experiencing the benefits that the proposed solution provides. In particular, the cost reduction, simplicity of fabrication or even the possibility of manufacturing designs identifying those non feasible with conventional setups. Comparing to conventional designs, the number of layers for each single-phase transformer can be divided by two, obtaining approximately the same conductor loss. In addition, commercial single-phase EE or EI cores can be used in the designs, avoiding the need of a custom-made magnetic core. As a future study it is required to analyze the impact of an interleaving phase windings to reduce leakage effect. Planar windings allow this arrangement. At the end of the day, if production costs of three-phase transformers are reduced as well as transformer efficiency is also increased then it is possible to go through lower profile parts for higher powers.

References [1] R.W. De Doncker, D.M. Divan, and M.H. Kheraluwala, "A Three-Phase Soft-Switched High-Power-Density DC/DC Converter for High-Power Applications," IEEE Transactions on Industry Applications, Vol. 27, No. 1, pp. 63 73, Jan./Feb. 1991. [2] R. Asensi, R. Prieto, J.A. Cobos, and J. Uceda, “Modeling High-Frequency Multiwind- ing Magnetic Components Using Finite-Element Analysis,” IEEE Transactions on Mag- netics, Vol. 43, No. 10, pp. 3840 3850, Oct. 2007. www.premo.com www.bodospower.com September 2012 Bodo´s Power Systems® 51 DIODES AND RECTIFIERS

High Current Rectifier Diodes for Welding Applications The trend is to increase frequency from 1 kHz today to 10 kHz or even 20 kHz

Resistance welding, although not a high profile power electronics application, has specific requirements which have lead to the development of a family of application specific devices. The ever increasing demands are pushing the limits for new developments, both in terms of electrical parameters as well as reliability. By Björn Backlund ABB Switzerland Ltd, Semiconductors and Ladislav Radvan ABB s.r.o. Semiconductors

In this article, we’ll take a look at the application itself, the require- • A diode rectifier to convert the quasi-square wave current to DC- ments the power semiconductors must meet and the components current. This is done since the welding quality is better when using which have been developed to meet these demands. Finally, we’ll DC instead of AC. The connection of choice is type M2 to reduce take a look at the trends in new product releases in the near future. the number of diodes required for the rectification. When higher currents are needed, the capability is increased by having two or Resistance welding more diodes connected in parallel. Resistance welding is a technique used mainly for joining sheets of • A welding gun with water-cooled electrodes between which the metal. It involves the generation of heat by passing a current through metal sheets to join are pressed. the resistance caused by the contact between the metal surfaces. Small pools of the molten metal are formed at the weld area when the high current is passed through and after the area cools, a solid joint is established. In comparison with other welding methods, resistance welding is very efficient, as it causes little pollution and limited work piece deformation. It has high production rates, can easily be automated and requires no filler materials. It is used extensively in the automotive industry, since most cars have several thousand spot welds made by industrial robots. Figure 2: A typical welding circuit

The welding cycle and diode load In the automotive industry, a typical welding cycle consists of 5 phases with a total cycle time usually in the range 4 – 8 s. The 5 phases are: • Welding time: when the welding current flows through the system causing the metal at the joint to partially melt. • Holding time: when the metal, still under pressure from the welding gun, cools down to a temperature where the joint is established. • Gun opening time: when the pressure is released and the gun pre- pares to move to the next welding spot. Figure 1: Resistance • Gun moving time: when the gun moves to the next welding spot welding of a car body • Gun closing time: when the parts to be joined are pressed togeth- Welding circuit principle er. The electrical circuit of the resistance welding system consists of 4 parts: The duty cycle, often referred to as ED from the German word “Ein- • A frequency converter generates a single phase 560V square schaltdauer”, is defined as the ratio between welding time and total wave current with the desired frequency from the standard 400V cycle time, consisting of the sum of the welding time and the time 3 phase AC input. between the welding intervals. For the welding sequence described • A transformer with a secondary voltage in the range of 6.3 – 20 V, earlier, the definition of duty cycle is as per Figure 3. with 10 V being the most common. The secondary current is often in the range of 10 – 15 kA and even higher for Aluminium welding.

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The current through the diodes during the welding time is shown in In the automotive industry, the transformer, the rectifier and the weld-

figure 4. The output current IOUT is the sum of currents ID1 and ID2 ing gun are often placed on a robot arm. Thus, size and weight is of and, in the example, is 20 kA. The current waveforms of both diodes, great importance. Since increased frequency reduces the size of the

ID1 and ID2, are rectangular pulses with the magnitude 20 kA, 10 kA transformer at equal power, the trend is to increase the frequency and 0 with an average current of 10 kA per diode. T is the operation from the 1 kHz used today to about 10 kHz or possibly even 20 kHz. period. ABB welding diodes ABB has developed a comprehensive welding diode range that is shown in Table 1. Due to the low voltage, it is possible to use thin silicon to reduce conduction losses. Since the requirements for air strike and creepage distance are low, thin housings with low thermal resistance are used, see Figure 5. An added advantage is the small size and low weight of the diodes, a welcome feature for equipment mounted on a robot arm.

Figure 3: Typical welding cycle

Required performance of diodes for welding applications For each car model, a customised welding system is designed with the requirement that it should run without failure as long as the given car model is produced. Each welding cycle represents a load cycle for the diodes and the expected lifetime is generally more then 10 million cycles. This means that the load cycling capability of the diode Figure 5: Welding diodes from ABB is crucial for the choice of component and this capability is determined by the temperature swing the diode undergoes during the Standard High frequency cycle. To keep the temperature swing as low as possible during the (NEW, in development) cycle, the diodes must be designed for lowest possible losses and (up to 2 kHz) (up to 10 kHz) Standard hermetically 5SDD 71X0400 5SDF 63X0400 thermal impedance. sealed housing 5SDD 71B0400 5SDF 63B0400 5SDD 0120C0400 5SDF 0102C0400 Housingless version 5SDD 92Z0400 5SDF 90Z0400 (HLWD) 5SDD 0105Z0400 5SDF 0103Z0400 5SDD 0135Z0400 5SDF 0131Z0400 Table 1: ABB’s Welding Diodes portfolio

The quest for lower thermal impedance lead to the introduction of the housing-less welding diode (HLWD) some years ago. Although more susceptible to environmental conditions, the HLWD has found its place in the welding industry due to improved thermal performance.

To meet the demands of higher frequencies, a new group of high frequency welding diodes with high current capability combined with excellent reverse recovery characteristics is currently in development. These new features will enable operation with high efficiency at frequencies around 10 kHz. ABB’s new high frequency welding diodes will be available in sealed and HLWD versions.

www.abb.com/semiconductors

Figure 4: The current flowing through the diodes during welding

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