An AC High Frequency Quasi Square Wave Bus Voltage for the Next Generation of Distributed Power Systems

Dr. Angel Gentchev Douglas P. Arduini - Consultant Arduini Design & Development (AD&D) Analog Devices, Inc. 2415 San Ramon Valley Blvd., #4-415 1500 Space Park Drive San Ramon, California 94583-1651 Santa Clara, CA 95052 Phone/FAX 925-804-6063 Phone: 408-562-7334, Fax: 408-562-2603 E-Mail: [email protected] E-mail: [email protected] URL: http://www.AD-and-D.com

(Presented and published in Proceedings of High Frequency Power Conversion HFPC ’98 Conference, November 1998, Revised 10-14-00, Updated October 2009)

Abstract - An advanced Alternating Current Distributed Power System (AC-DPS) is proposed as a new low- price and high-performance alternative to the typical Direct Current Distributed Power System (DC-DPS). A high frequency quasi square wave or trapezoidal AC waveform is distributed on the DPS power bus from the Bulk Power Front-End Rectifier/Inverter Stage, to a variety of AC to DC Secondary Power Converters. Zero-Voltage (ZV) switching is used in the DC/AC inverter, and various types of AC/DC power conversion stages are available at the board level or point-of-use loads, including Zero-Current (ZC) Resonant Switching, for post regulation, if needed. This next generation DPS can provide lower cost, board space, simplicity, improved reliability, and manufacturability. This technology may also be well suited for distributed power in the higher power Personal Computer (PC), with solutions for higher di/dt power demands of the modern microprocessors. A 250W prototype system with 48VAC DPS bus at 250KHz was tested.

INTRODUCTION

The demand for new features and higher performance digital electronics and CPUs in nearly every application in modern electronic industry presents a major challenge to the power supply and power distribution design. The trend to lower the CPU supply voltages with tighter tolerances, higher currents, faster load steps, plus the need for more output voltages to various analog, digital, and optical support chips, creates difficult problems to maintain power quality in a cost-effective manner. Centralized power distribution is no longer capable of providing power quality used in the modern and future digital electronics [1,2], including the new high power personal computer (PC) and workstation, for the following reasons:

1. Additional supply voltages, typically including +12V, +5V, +3.3V, -5.2V, and -2.1V.

2. Very Fast Transient Response (0.1-10A/nS) at low supply voltage (2.0-3.6V), not possible from the bulk power supply as direct power source of the modern CPU electronics. Therefore most systems use low voltage DC/DC Converters, which are required as secondary converters for regulation at the point-of-use,

3. Higher currents for lower CPU supply voltages, up to 50A in some applications. Without a DC or AC power distribution system at higher voltage level and therefore lower current level, the pure resistive losses and heavy wiring become an unacceptable solution,

4. Static and dynamic load regulation with tight tolerances, +/-5% to +/-2% at voltage levels of 3.6V to 2.0V and lower at various critical loads in the system is not practical from a single bulk supply,

5. Cross regulation effects between the outputs of a single bulk converter, add to the problems with the tight regulation requirements of many of the modern digital electronic circuit specifications.

The DC-DPS is a popular solution for high power digital systems, but it requires large quantities of DC/DC

01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 1 of 15 converters on the point-of-use boards and loads, and require distributed input filters for isolation from converter interaction and they are sensitive to impedance instability [1,2,3,4 and 7]. Inrush current control switch circuits on each board for turn-on current limiting are also usually required. The DC-DPS solution is also complex with a large quantity components, filters, and DC/DC power supplies that add a high cost to the system, take up a large amount of board space, lower reliability with high parts count, and require second sources that are form, fit, and function compatible. The DC-DPS is also being considered as the solution for the high power PCs and workstations.

An improved power system would be one that could provide all the advantages of a DC-DPS over the centralized power supply distribution, but at a lower cost, smaller board space, and fewer components. Low voltage 24VAC DPS power systems are used today at 60Hz for security and survival systems, outdoor lighting, and control systems. But, 60Hz is impractical for small size, lightweight, and low cost at high power. Higher frequency AC sine wave systems above 20KHz have been used, but exhibited power factor problems that would be expensive to correct at every board or load [1]. The advantages of an AC-DPS using square or rectangular (trapezoidal) waves are discussed in detail in references [1,4].

DESCRIPTION OF A PRACTICAL AC-DPS

A basic DC-DPS is shown in Figure1 and compared to basic AC-DPS shown in Figure 2, showing the rectifier and switching stages of each. It is shown that the AC-DPS has one or two less switches (optional inrush control), one less rectifier stage less at the intermediate voltage level, and one less set of filters at the intermediate voltage level. The AC-DPS also has smaller capacitance sizes on the low voltage level because the AC distribution voltage is pre- regulated with little or no need for post regulation. When post regulation is needed for load changes and tighter regulation, power conversion is optimized with high duty cycles and the need for small PWM regulation bandwidth. The component savings improves performance at a reduced cost with simple on-board regulators that eliminate the need for typical DC/DC converter “bricks,” and in some cases need no post regulator. Efficiency savings are obvious due to fewer switches, rectifiers, and filters, as shown in Figures 1 and 2 as a comparison between the typical DC-DPS with 73% efficiency example and an AC-DPS with 81% efficiency example.

As in every distributed power system, the main advantages are flexibility, elimination of distribution losses, improved point-of-load regulation, and fault tolerance. However, the complexity of the system and the multiple power conversion cycles in series, effect the overall price of these systems, thus the DC-DPS is a poor choice in price-sensitive commercial electronic products and systems.

Figure 3 shows the 7 power conversion stages from the input Line 50/60Hz to DC/DC converter output of that DC- DPS. As a logical improvement, as was known in the power utility industry more than a century ago, AC distribution is a better distribution system than DC. Two intermediate AC/DC and DC/AC power conversion cycles can be avoided in the structure of DC-DPS by implementation of an AC-DPS. It is shown in Figure 4 that the “Middle-Man” DC/DC converter is effectively not necessary and can be eliminated, thus cutting the overall power conversion steps from 7 to 5. The direct result from employing “No Middle-Man” in the AC-DPS approach is a significant price reduction and performance enhancement. Therefore one full conversion cycle of DC/AC and AC/DC can be avoided with corresponding improvement of less hardware, less complexity, higher efficiency and price reduction with the AC-DPS. A good example of such an AC-DSP based system is described in reference [4] with some comparisons and practical results.

Due to the novelty of the AC-DPS, including for low power electronic systems like the PC, there are some important questions and considerations regarding an AC-DPS, as follows:

1. What frequency should be used on the AC Bus? The answer can be any frequency in the range of 20KHz to >1MHz, which gives proper fit to the system specification goals. If the highest priority is miniaturization, then higher frequency is better, but if the priority is simplicity at higher efficiency and lower risk, then lower frequency is better for performance of the AC DPS.

2. What should be the Bus Voltage Waveform Shape? There are mainly three choices – sine wave and quasi sine wave, square wave, or quasi square wave (trapezoid shape). The simplest waveform to generate is the square wave, but it is the most difficult one to be EMC managed, due to the high harmonic content of AC Bus voltages and currents. The sine wave bus is the best for very low EMI and RFI, but it is the most difficult one to generate

01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 2 of 15 and regulate efficiently with high power and high frequencies, plus it suffers heavily from power factor or form factor. The square wave is the simplest waveform to generate, but the switching speeds of voltage and current provide high EMI and RFI, plus high switching losses. A good compromise is the quasi square wave or trapezoid wave bus voltage, with controlled rise and fall dead times with transitions times of 5-15% of the AC pulse period, thus greatly reducing the high frequency power harmonic content of the AC distributed bus voltage.

Line Regulation Bulk Front-End: The input line voltage is regulated to a DC bus voltage to the DC/AC inverter as regulated peak-to-peak voltage of the AC-DPS trapezoidal waveform, typically with a PFC AC/DC Converter or a DC/DC converter. This inverter stage requires no isolation because transformer isolation is automatically provided at the DPS load AC/DC converter stages, and transformer isolation is optional at the inverter DC/AC inverter front-end stage. Load regulation can be improved with an additional voltage feedback loop with peak detection of the AC-DPS trapezoidal voltage waveform.

DC/AC Inverter Bulk Front-End with Zero-Voltage switching is an ideal solution for generating controllable Soft Switching bus voltage waveforms. The AC trapezoidal waveform voltage can be generated in the front-end converter by a half (or full) bridge converter where the transitions of the peak voltages from rail-to-rail are set by the Voltage Mode resonant loop formed by the sum of the node capacitance and the inductance of external ZV mode choke. Thus, the slew rate of that voltage does not depend on load changes. The simplified schematic and the corresponding switching node waveforms are shown in Figures 6 and 7. The inverter stage replaces the bulk front- end DC/DC converter and together with the Power Factor Correction in front provides peak-to-peak voltage regulation of the line to provide a minimum need for post regulation at the loads. The trapezoidal wave is an improvement over other square wave distribution systems, with approximately 5-15% transition duty cycle requiring small filter sections, limiting dV/dt for reduced EMI and transient effects. Shielded bus transmissions line techniques or twisted pair technique are appropriate ways to reduce furthermore still radiated EMI fields in the backplane where needed. A design goal of less than +/-2% line/load regulation of the AC Bus including ripple and noise that can be achieved by the PFC line regulator, controlling the DC bus (usually 400V) to maintain the inverter transformer output voltage to +/-48Vpeak triangle wave on the AC-DPS bus system backplane. Additional sensing of the backplane peak voltage can be added to the PFC voltage loop control if required.

EMI Considerations: EMI radiation with square or rectangular wave power distribution is an obvious concern. The use of a trapezoid wave is an improvement over the pure square wave for harmonic content. Noise source energy is minimized with Zero Voltage and Zero Current topologies that are choices at the Bulk Inverter stage and Secondary Converter stages of the proposed AC distribution system. In fact, this AC-DP System is a direct derivative from the innovative designs reported in [5,6,10 and 13]. If is necessary, the transmission line can be additionally shielded from radiation in coaxial or shielded PC power planes or strip transmission line [1, 4].

Load Regulation: Post regulation and filtering complexities are minimized with the regulated AC trapezoid input waveform. Small high frequency transformers isolate the power at each board or load area, with secondary rectifier filters for each voltage requirement. Synchronous rectifiers can also be incorporated to improve efficiency. Load voltage accuracy and regulation can be held within +/-5% with proper design to eliminate post regulation to some loads [1][2]. For other load, requirements a variety of different low-cost post regulator designs could be used [1]. Most applications will favor using low dropout regulators (LDOs), Mag-Amps, and a Zero-Current Fully Regulated (ZC) Resonant Converters, to supplement the Zero Voltage switching of AC/DC Bulk Converter. Another choice good choice is a secondary controlled synchronous rectifier PWM. Typical board or load regulators for the DC-DPS are shown in Figure 3, and a variety of choices are shown for the AC-DPS are shown in Figures 4, 5, 10, 11, and 12.

Simple Transformer Rectifier as Low Cost Secondary Converter: The bipolar trapezoidal wave from a transformer secondary of the AC-DPS bus provides good line regulation of about 3-6% load dependent DC voltage after a rectifier stage. This is accomplished with low copper and core loss transformer designs and robust sizing of rectifiers for low dynamic resistance for small forward voltage changes with load current changes. The cost of this simple transformer/rectifier/filter is 5 to 10 times lower than the price of “bricks” in the DC-DPS counterpart. This design has no stability concerns from a regulator loop control or negative impedance effects on the input filter or distributed filters. Also, the filter size is smaller because of a fixed 85-95% duty cycle, with no ride-through time requirement for PWM step recovery time from load step response.

01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 3 of 15 However, there may be a need for ride-through or holdup time in fault tolerant system designs with energy storage for fuse fault clearing that can drop the bus voltage. This energy storage will be at the lower end-point voltage level versus the at intermediate DC level in a DC-DPS, thereby requiring more capacitance.

The bipolar waveform can use self driven synchronous rectifiers for half-wave (42.5% to 47.5% duty) or full-wave rectification (85% to 95% duty) as shown in Figures 10,11.and 12. The catch or free-wheeling rectifier in the full- wave rectifier circuit can use a standard Schottky diode in place of a FET synchronous rectifier, with little effect on efficiency because of the high duty cycle, therefore the low conduction time.

Synchronous Rectifier PWM Secondary Converter: The bipolar trapezoidal wave from a transformer secondary from the AC-DPS bus can be post regulated with phase modulated synchronous rectifier switches with PWM secondary control. The bipolar waveform precludes a typical synchronous rectifier phase modulation, but can be controlled with MOSFETs switched in pairs as bi-directional switches for blocking and conducting.

Mag-Amp PWM based Secondary Converter: The well known Magnetic Amplifier is perfectly suited for AC- DPS post regulation function. One consideration is in very high current and low voltage applications, where the effects of transmission line and transformer leakage reduce the maximal output power capability to the load. But this solution is one of the simplest and effective to perform the load regulation on a particular DC output, especially when the output voltage needs to be tightly regulated for the modern fast CPUs.

ZC Phase-Modulated Resonant Converter: This is one or the best post regulation choices because it is the only way to eliminate the negative effect of noted distributed line inductance plus the leakage inductance of the transformer(s). Here a controllable series resonant loop is formed by the sum of all and the series resonant capacitor are used. The resonant loop can be controlled by primary side magnetic amplifier or by phase-modulated electronic switch at constant frequency and duty ratio. The Zero Voltage and Zero Current switching and the way to achieve control over the power transfer between input and output of such a resonant system are well described in [5,10,11 and 13]. A magnetic amplifier control can be used as a simple control of the resonant power transfer as shown in [9].

Low Dropout (LDO) Regulator based Secondary Converter: The bipolar trapezoidal waveform from a transformer secondary of the AC-DPS bus provides regulated 3-6% DC voltage after a rectifier stage. It is easy to use the line regulated only bus voltage as a regulated headroom voltage for an LDO. This is an inexpensive regulator, often using a standard 3-terminal regulator. With regulated headroom, efficiency is competitive to DC/DC converters, with up to 84% efficiency at 3.3V output and 70% overall including the rectifiers [3]. This is an attractive solution to critical loads requiring low noise and tight regulation tolerances. The high speed dynamic response, tight regulation accuracy, low ripple and noise of the LDO linear regulator can provide the best power quality with the least filtering requirements at the lowest cost and smallest board space for critical loads as the new CPUs and support chips [3].

Pentium II Synchronous Buck Converter modified for AC-DPS Secondary Converter: A version of a Secondary DC/DC post regulator for an AC-DPS can be build using synchronous switching regulator from the Buck topology. The AC bus voltage of the AC DPS can be transformed and rectified to DC voltage via small HF transformer and simple full-wave rectifier/filter. The output DC voltage is post regulated for load changes, where the AC input line is stabilized at the AC Bus voltage by the PFC/Inverter stage. To achieve a precise stabilized and programmable DC output as is required by the latest generation of Pentium II CPUs and the next generation, is a highly efficient synchronous switching regulator as an appropriate solution.

An example of such a controller is the ADP3152 from Analog Devices, specially optimized to supply Pentium II Processors, having a 5-bit DAC to read a voltage identification code directly from the processor. This controller meets Intel’s stringent transient specifications VRM8.2 and VRM8.3, and possesses the minimum number of output capacitors and the smallest footprint. The application schematic is given in Figure 17. The transient response is shown in Figure 18 for the step 0.8A-19A-0.8A with optimal compensation, reported in the Proceedings of IEEE APEC’98 [12].

01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 4 of 15 AC-DPS PROOF-OF-CONCEPT PROTOTYPE

AC-DPS Prototype: An AC-DPS proof-of-concept and practical implementation prototype was built for the purpose of fine tuning the design procedure and to test and debug the AC solution from both the theoretical and practical point of view. The input voltage is Worldwide 85 to 265 VAC to an active PFC AC/DC converter. The output power is only a demonstration level of 250W, the output DC/AC inverter provides an AC Bus at +/-48VAC peak trapezoidal waveform at 250KHz. Three secondary post regulators were tested, a Mag-Amp PWM, a ZC Resonant Converter, and an LDO.

Prototype Test Results: Prototype test results from a prototype 250W system with 250kHz AC bus 48V DPS have shown excellent performance, minimum cross regulation and efficiency of 81% from AC bus to multiple +5V, +12V and +24V outputs. Figures 13 to 16 show the performance of the prototype and its switching waveforms to demonstrate the cancellation effect of ZV and ZC switching on transmission line impedances. A power distribution to three remote loads with up to 5 to 7 foot cable lengths was used to demonstrate the proper operation under the worst-case bus parasitics.

Cost Comparisons and AC-DPS Saving: A price comparison of a typical DC-DPS system versus an AC-DPS system at 600W is shown in Table 1, with a 37% overall system cost saving (with a 55% reduction in components cost for the Secondary Modules) for the AC-DPS. The comparison was made as objective as possible, using the standard components and off-the-shelf products of well-known power supply companies. The reduction in complexity and by the conversion to AC distribution reflected the lower component and labor price at both modular and system level.

CONCLUSION

The advantages of an AC-DPS have been shown to include savings and advantages in cost, board space, component parts, complexity, and reliability, plus the use of distributed DC/DC converters bricks can be avoided. Flexible and simple power design changes can be implemented as needed with minimum impact on cost and schedule. The addition of another voltage or increasing the output power for a board upgrade is as simple as adding a new transformer winding and changing the rectifier/filter section.

From the brief description of an advanced AC-Distributed Power System, the authors have shown an improved alternate method to distributed power to different PCB’s, modules, and loads that are used in a variety of modern electronic equipment. A price comparison between two as parameters typical AC and DC based Distributed Power Systems has been shown, giving 37% lower cost in favor to the AC-DPS.

A proof-of-concept 250W prototype was built for 250KHz operation, with good operating results. This fully functional AC-DPS delivered 250W to three remote loads, using three different post regulator secondary converters, with additional features of the Soft Switching AC Power Distribution. The advantages are shown at the boards or point-of-use loads, with the elimination of many DC/DC converters to lower costs, weight, complexity, filters requirements, board space, qualification costs, second source requirements, reliability, design risk, and faster time- to-market schedules.

With the DC-DPS and its variations [1] as the accepted standard replacement to the centralized power distribution systems, the AC-DPS will find the typical resistance to acceptance and change. Replacement of arrays of DC/DC converter “bricks” in systems with simpler and lower cost regulated solutions is a drastic concept. The strong incentive for lower cost, smaller board space, lower parts count, and fast time-to-market with low risk designs should prove as an incentive to consider the AC-DPS for new designs.

REFERENCES

01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 5 of 15 [1] D. Arduini, “Distributed Power System using AC to solve DC Distributed Power Problems,” HPFC 1995.

[2] D. Arduini, ”A Distributed Power System with a Low-Cost Universal DC/DC Converters”, Power Conversion Electronics 1995 Conference.

[3] D. Arduini, “A DC/DC Converter Using a PWM/LDO “Hybrid” for Low Voltage Power Solutions,” Power Co nversion Electronics 1995 Conference.

[4] R.Watson, W.Chen, G.Hua and F.C.Lee, ”Component Development for a High-Frequency AC Distributed Pow er System,” Proceedings of IEEE 1996, pp.657-663.

[5] Angel Gentchev, ”A New Low Noise Multiresonant Converter,” Proceedings of PCIM’92 Conference in Nurnb erg, Germany, pp.419-427.

[6] M. Jovanovic, R. Farrington and F. C. Lee, ”Comparison of Half-Bridge, ZCS-QRC and ZVS-MRC,” IEEE Tra nsactions on Aerospace and Electronic Systems, Vol. 26, No.2. pp.326-336, March 1990.

[7] Per Lindman and Lars Thorsell, ”Applying Distributed Power Modules in Telecom Systems,” Proceedings of IE EE-PESC’94, pp.777-785.

[8] Barry Arbetter and Dragan Maksimovic, ”DC-DC Converter with Fast Transient Response and High Efficiency for Low-Voltage Microprocessor Loads,” Proceedings of IEEE-APEC’98.

[9] A.S.Kislovski, ”Linear Variable Inductor in power processing,” Proceedings of APEC’87, pp.87-92.

[10] Kosuoke Harada and Katsuaki Murata, ”Controlled Resonant Converters with Switching Frequency Fixed,” Pr oceedings of IEEE-PESC’87, pp.431-438.

[11] A.H.Weinberg and L.Ghislanzoni, ”A new Zero Voltage and Zero Current Power Switching Technique,” Proce edings of IEEE-PESC’89, pp.909-919.

[12] Richard Redl, Brian Erisman and Zoltan Zansky, “Optimizing the Load Transient Response of the Buck Converter”, IEEE APEC’98, p.170-p.177.

[13] Angel Gentchev, “A Novel Fully Stabilized Multiresonant Converter”, Proceedings of PCIM’93, Nuerberg, Germany, p. – p.

01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 6 of 15 Figure 1. Typical DC-DPS with efficiencies.

Figure 2. Typical AC-DPS with efficiencies.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 7 of 15 15 LOW SIDE TIPICAL PCB BOARD WITH TWO VOLTAGE OUTPUTS INTERMEDIATE FILTER INRUSH CONTROL SWITCH FIXED LOAD VOLTAGE HIGH SIDE BULK FRONT- END CONVERTER dI/dT LOAD

LARGE VALUE CAP

AC POWER

ISOLATION TRANSFORMERS FIXED LOAD

dI/dT LOAD

LARGE VALUE AC/DC RECTIFIER PFC DC/DC CONVERTER CAP ~/= =/= =/=

FILTER DC/DC CONVERTERS OUTPUT FILTER

Figure 3. Basic conversion stages of a typical DC-DPS.

FIXED LOAD

dI/dT LOAD

LOW VALUE AC CAP

ISOLATION TRANSFORMERS

FIXED LOAD

dI/dT LOAD

AC/DC RECTIFIER PFC DC/AC CONVERTER

~/= =/= =/ LOW VALUE CAP

AC/DC CONVERTER OUTPUT FILTERS

Figure 4. Basic conversion stages of a typical AC-DPS.

Table 1. Price comparisons for typical 600W DC-DPS and AC-DPS.

DC Distributed Power AC Distributed Power System Absolute % Price System 600W 600W Price Difference Difference Front-End $214.88 $193.98 $20.90 less 9.73% less PS (-$11.802 component cost) Transfer (-$9.099 labor cost,2.585h x 3.52/h) Price, Six 100W $52.63 x 6 = $315.78 $23.63 x 6 = $141.78 $174.00 less 55.10% less DC/DC or (-$17.21 component cost per unit) AC/DC PS (-$11.79 labor cost, 3.35h x 3.52/h) Transfer Price Total Price $530.66 $335.76 $194.90 less for 36.73% less for an AC DSP an AC DPS

File: 01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 8 of 15 15 BASIC POINT OF USE REGULATION DESIGN CHOICES

DC - DPS

INRUSH CONTROL EMI FILTER DC/DC PEM CONVERTER i Vi Vin

48V DC

Vin

DC/DC PEM CONVERTER n Vn

AC - DPS

V1 LINE REGULATION ONLY 5% LINE-LOAD REGULATION Vin 48V AC

Vin

V2

LINE REGULATION ONLY 5% LINE-LOAD REGULATION

QUASI-SINUS WAVE

V2

V3 .1%

MAG. AMP

V4 .1% SYNCHRONOUS RECTIFIER

V5 STABILISED SYNCHRONOUS 5V .1% CONVERTER

V6 .1% STABILISED

RECTIFIER

V7

LDO V8

Figure.7

Figure 5. DPS conversion stage comparisons choices for typical DC-DPS and AC-DPS.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.doc Page 9 of 15 15 Vin 400 VDC Q1

C1

Lext L O R T N

O TR1 C

Q2 C2

AC BUS

Figure.5

Figure 6. Bulk DC/AC Inverter section.

Figure 7. DC/AC Inverter loaded with 50 watts ZC to AC/DC Secondary Converter, CH1 is AC BUS Voltage, CH2 is a Switching Node Voltage of the DC/AC Converter, CH4 is the AC BUS Current supplying Zero Current AC/DC Secondary Converter.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.docPage 10 of 15 15 Stabilized AC/DC Converter

R1

Q

R2

T1 R6

D1

C1 R3

T2 C2 R5 C3 INPUT 48VAC/250kHz

C5 DC OUTPUT

F1 VR1

C4

R4 D2

Figure 8. Prototype ZC AC/DC converter.

Stabilized AC/DC Converter

R1 R2

Q

R7

D1 D2 L3

L1 R4

T R6 CR1 INPUT 48VAC/250kHz C2 C3 DC OUTPUT C4

F1 L2 VR1

CR2 R5

C1

R3

Figure 9. Prototype Mag-Amp AC/DC converter.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.docPage 11 of 15 15 Figure 10. Self-driven half-wave synchronous rectifier/filter secondary power supply.

Figure 11. Self-driven full-wave synchronous rectifier/filter secondary power supply, with standard catch diode rectifier, as a good solution for high duty cycles.

Figure 12. Self-driven full-wave synchronous rectifier/filter secondary power supply, with synchronous rectifier catch diode.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.docPage 12 of 15 15 Figure13. AC DPS, AC/DC MagAmp Converter, 40 watts output power and AC/DC Zero Current Converter, 35 watts output power, CH1 is AC BUS Voltage, CH2 is a Switching Node Voltage of the DC/AC Converter, CH4 is the AC BUS Current supplying the Zero Current AC/DC Secondary Converter, CH3 is the AC BUS Current supplying the MagAmp AC/DC Secondary Converter.

Figure 14. AC DPS, AC/DC MagAmp Converter at 40 watts output power and AC/DC Zero Current Converter at zero watts output power, CH1 is AC BUS Voltage at the Secondary Converter Input, CH2 is a Switching Node Voltage of the DC/AC Converter, CH4 is the AC BUS Current supplying the Zero Current AC/DC Secondary Converter, CH3 is the AC BUS Current supplying the MagAmp AC/DC Secondary Converter.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.docPage 13 of 15 15 Figure 15. AC DPS, AC/DC MagAmp Converter at zero watts output power and AC/DC Zero Current Converter at 35 watts output power, CH1 is AC BUS Voltage, CH2 is a Switching Node Voltage of the DC/AC Converter, CH3 is the AC BUS Current supplying the Zero Current AC/DC Secondary Converter, CH4 is the AC BUS Current supplying the MagAmp AC/DC Secondary Converter.

Figure16. AC DPS, both AC/DC MagAmp Converter and AC/DC Zero Current Converter are at zero watts output power, CH1 is AC BUS Voltage, CH2 is a Switching Node Voltage of the DC/AC Converter, CH3 is the AC BUS Current supplying the Zero Current AC/DC Secondary Converter, CH4 is the AC BUS Current supplying the MagAmp AC/DC Secondary Converter.

File: 01d6fc1ee6ab980250053c29ae9c9ef5.docPage 14 of 15 15 1 2 3 4

D D R14 10 JP1

1 L2 1uH 1 12Vin 2 2 5Vin 6

R 3 C7 C12 3 5VRTN

k 100uF/6.3v 4 7 4x1500uF/6.3V 4

4 12VRTN C1 Q5

S1 K 7

0 IRL3803

R 22uF 1 10 U1 ADP3152 0 2 9 1 16 1 VID1 VID0 PGOOD 3 8 4 7 2 15 VID2 P-GND C 5 6 C 3 14 VID3 DRIVE1 4 13 VID4 DRIVE2 5 12 AGND Vin L1 3.3uH 6 11 R12 2.5mOm, 1W SD SD PWRGD 7 10 FBEAD SENSE- CMP 2643000101 JP2 8 9 SENSE+ Ct 1 1 VccP C2 2 2 VccP 6.2nF D1 C8 3 Vss 1N5822 8x1500uF/6.3V 3 B B 4 Q6 4 Vss R5 IRL3803 220

R4 C10 C3 220 C11 1nF 200pF R1 1nF 10k

Title A Enhanced power option 2.0V/0-19A A Size Num ber Revision C ADP3152 Date: 2-Apr-1998 Sheet of File: C:\ADP315~1\ADP3152R.SCH Drawn By : 1 2 3 4

Figure17. ADP3152 Application Schematic covering VRM8.2 and VRM8.3 Intel Specification

Figure 18. Transient Response of output voltage 2.00V,Current Step 0.8A-19A-0.8A

File: 01d6fc1ee6ab980250053c29ae9c9ef5.docPage 15 of 15 15