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BOOKSHELF Simplified Design of Linear Power Supplies Simplified Design of Linear Power Supplies, by John D. Lenk. Published 1994 by ButterworthHeinemann. Hard covers, 246 pages, 241 x 160mm, ISBN 0-75069506-4. Price $62.95. The Author says in his preface that “this book has someth­ing for everyone”. The first six chapters cover the basics for all phases of practical design while the last chapter includes over one hundred worked-out design examples including: (1) an adjustable supply using an LM117 (LM317) regulator; (2) a triple output power supply using an LM117 regulator, two LM107 opera­ tional amplifiers and two transistors; and (3) a computer controlled supply using a 7475 latch and an LM338 adjustable regulator. Chapter 1, which covers linear power supply basics, is not a good beginning. It is obviously written for beginners but has errors which could cause confusion, especially if an oscilloscope was used to compare actual waveforms against those shown for the half-wave and full-wave rectifier circuits on pages 2 and 3. The Author shows the output waveforms at the diodes for half-wave and fullwave rectification assuming there is no capacitor but his circuits include electrolytic filter capacitors, which will dramatically change the viewed waveforms. Page 15 shows a diagram of an adjustable shunt regulator. This has a potentiometer between a 4.7 volt zener to ground and a 15 volt source with the caption “0 - 10V regulated” – again, puzzling for the beginner, while the more experienced will re­alise it should read “4.7 to 15V regulated”. Chapter 2 covers heatsinking in linear power supplies. Among the topics discussed in this chapter are heatsink ratings, power dissipation, mounting of components on heatsinks, mounting surface preparation, thermal compounds and the types of heatsinks available for integrated circuits. The majority, if not all of this information would be familiar to the experienced power supply designer. Chapter 3 is titled an introduction to discrete feedback regulators. The author first discusses shunt voltage regulators, including those with outputs both higher and lower than the reference voltage. He then goes on to detail series voltage and current regulators with a worked example for an 8V 4A unit. Details of adding parallel pass transistors to increase the output current are also discussed. Chapter 4 moves on to modern integrated circuit (IC) based regulators and covers the four basic sections: control, bias, DC level shift and output. The circuits for several commercial ICs are shown, with methods of increasing the output current and limiting the maximum current with excessive loads. The Author also shows how to monitor the heatsink temperature and shut down the regulator if the temperature becomes excessive. Chapter 5 is devoted to the basics of IC operational ampli­fiers in discrete linear voltage regulators. The chapter starts with an explanation of the benefits the operational amplifier brings to the designer. A discussion then follows on suitable reference sources and methods of obtaining output volt­ ages higher than the reference voltage. The chapter ends with details of the methods for remote sensing. Chapter 6 is concerned with linear power supply testing. It deals with measur­ ing output and input-output regulation, internal resistance, ripple, transformer phasing and transformer regulation. It also covers the measurement of transient recovery time, drift and temperature coefficient. The chapter finishes by showing methods for the connection of multiple loads to one power supply and two supplies to multiple loads. Again, we noted errors in the dia­grams on pages 90, 91 & 95. Chapter 7 is headed “Linear Supply Design Examples” and occupies over half the book. Disappointingly, it consists of virtually no original material, only reprints of circuits from the major manufacturers’ application notes. Coincidentally, the three design examples listed at the beginning of this review and quite a few others in this chapter were all taken from the Na­tional Semiconductor Linear Applications Handbook, which would surely be in every design engineer’s library. To sum up, a rather disappointing book. While we did not read it from cover to cover, several errors were noted, which should not have appeared. And while circuits from 16 different sup­pliers are included, the reader may be better off buying the application notes of one of the major manufacturers (eg, Nation­al, Motorola or Harris). Our sample copy came from the publish­ ers, Butterworth Heine­ mann Australia, PO Box 5557, West Chats­ wood, NSW 2057. Phone (02) SC 372 5511. (R.J.W.) July 1995  53