LB-28 General Purpose Power Supply

LB-28

Literature Number: SNOA692 eea ups oe upyLB-28 Supply Power Purpose General

National Semiconductor General Purpose Power Linear Brief 28 Supply June 1974

INTRODUCTION A general purpose lab type constant voltage/constant cur- ply is used as a constant voltage source.) The circuit shown rent power supply is easily made using standard integrated has good response both as a constant voltage or constant circuits. The circuit shown will provide up to 25V at up to current source. 10A output with both the output voltage and current adjusta- The use of the LM395 monolithic power transistor as the ble down to zero. Although relatively simple, very high per- pass element considerably simplifies the design power. The formance is obtained. LM395 acts as a 2A current limited, thermally limited, high Lab supplies must withstand considerable abuse. Good gain power transistor. Since only a maximum of 10 mAis control of maximum output current is mandatory both to pro- needed to drive the pass elements and complete overload tect the supply and the powered circuitry. One of the short- protection is included on the chip, external biasing and pro- comings of many commercial supplies is the use of a large tection circuitry is minimized. Only two control op amps are output capacitor to help frequency compensate the regula- needed–one for voltage control and one for current control. tor loop. This output capacitor can discharge many times In constant voltage operation, a reference voltage is fed the peak output current of the supply into the load as well as from voltage control pot, R1, through a high frequency filter degrade the ac output impedance when the supply is used into the non-inverting input of an LM308 op amp. The output as a constant current source. (Of course, the output capaci- of the LM308 drives seven paralleled LM395’s as emitter tor helps keep the ac output impedance low when the sup- followers to obtain a 10A capability.

*Solid Tantalum. **Lights during current limit.

TL/H/8477–1

C1995 National Semiconductor Corporation TL/H/8477 RRD-B30M115/Printed in U. S. A. LB-28 General Purpose Power Supply upt uptcreti esdi 9adcmae with compared and R9 V in between voltage sensed the the is mode, the current control current Output to constant loop output. voltage the constant in the overcomes used LM101A is circuit the is R15–C9 When network oscillations. and frequency compensation loop. high C6 overall parasitic and the suppress C5 for Frequency C4 capacitors and R11, with LM308 Resistor the even loads. for programmed C3 with quickly achieved capacitive be can capability supply large sink addi- current the An output lead so some R7. supply (2A) provide to power to R10 negative LM308 of the the ratio from of the driven by is 5 LM395 at with tional set output the gain from overall directly the R10 through taken is Feedback Vt .Vrfrnefr0 o1Aotu.We the When is output. output LM101A 12A the to level, 0A set the for below reference is current 1.2V provide output to to diode reference 0V voltage a low LM113 an across ed ainlde o sueayrsosblt o s faycrutydsrbd ocrutptn iessaeipidadNtoa eevstergta n iewtotntc ocag adcrutyadspecifications. and circuitry said change to notice without time any at right the reserves National and implied are licenses patent circuit no described, circuitry any of use for responsibility any assume not does National .Lf upr eie rssesaedvcso .Aciia opnn saycmoeto life a of component any is component critical A 2. or devices are systems NATIONAL or OF SUPPORT PRESIDENT devices LIFE THE support IN OF COMPONENTS APPROVAL Life WRITTEN CRITICAL 1. EXPRESS AS herein: used THE USE As WITHOUT FOR CORPORATION. SEMICONDUCTOR SYSTEMS AUTHORIZED OR NOT DEVICES ARE PRODUCTS NATIONAL’S POLICY SUPPORT LIFE alr oprom hnpoel sdi codnespotdvc rsse,o oafc t aeyor safety its affect to life or the of system, effectiveness. failure or can the perform cause device to to failure support expected whose reasonably injury system be significant or can a device labeling, in support user. result the the to to in accordance expected provided in reasonably use whose be used for and properly life, instructions implant when sustain with or surgical perform, support to for (b) failure or intended body, are the into (a) which, systems e:180 7-99DushTl ( Tel: Deutsch 272-9959 1(800) Tel: a:180 3-08EgihTl ( Tel: English 737-7018 1(800) Fax: oprto uoeHn ogLd aa Ltd. Japan Ltd. Kong Hong Semiconductor National Semiconductor National cnjwge Email: ( Fax: Europe Semiconductor National 76017 TX Arlington, Road Bardin West 1111 Corporation Semiconductor National a n h r fR.R sconnect- is R2 R2. of arm the and tlaoTl ( Tel: Italiano Fran 3 i e:( Tel: ais a a a a a 9 -8-3 68 a:(5)2736-9960 (852) Fax: Kong Hong 80 16 0-180-534 49) 32 78 0-180-532 49) 9 -8-3 58 3hFor tagtBok e:81-043-299-2309 Tel: 2737-1600 (852) Tel: Kowloon Tsimshatsui, Block, Straight Floor, 13th 58 93 0-180-532 49) 85 85 0-180-530 49) 86 85 0-180-530 49) @ em.s.o ca ete atnR.Fx 81-043-299-2408 Fax: Rd. Canton 5 Centre, Ocean tevm2.nsc.com h upybpse hudb ertepwrtransistors. power the near be devices, should high bypasses are under supply LM395’s dissipated the the be Since will conditions. large 300W case a since the worst Also, necessary sharing. on is current sink mounted good for heat insure be to construction should sink in heat LM395’s same needed All are the operation. precautions decreasing proper special operation. regulating, mode few not current A to is voltage it output from the time when clamps switchover LM101A D2, Diode, is the LM101A supply.) of needed the positive of is the the range to supply limiting operative equal positive mode D3, common separate through the no since devices that the pass (Note decreases output current. and the the negative to swings control the drive LM101A point LM308 the control the of the to output increases and current the D3 When outpput. biasing reverse positive, IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Communications and Telecom www.ti.com/communications Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps DLP® Products www.dlp.com Energy and Lighting www.ti.com/energy DSP dsp.ti.com Industrial www.ti.com/industrial Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical Interface interface.ti.com Security www.ti.com/security Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page e2e.ti.com