Switching Power Supply Design, Third Edition

250 Pages·2010·2.6 MB·English

by  Abraham I. Pressman

Source : Switching Po wer Supply Design, Third Edition Abraham I. Pressman, Keith cover
Billings, Taylor Morey
Abraham I. Pressman, Keith Billings, Taylor Morey i
Switching Power Supply Design
Third Edition
Abraham I. Pressman
Keith Billings
Taylor Morey

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Abraham I. Pressman, Keith Billings, Taylor Morey ii

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Switching Power Supply Design, Third Edition
Copyright © 2009 by The McGraw-Hill Companies.
All rights reserved. Printed in the United States of America. Except as permitted under the Copyright Act of 1976, no
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ISBN 978-0-07-148272-1
MHID 0-07-148272-5
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Abraham I. Pressman, Keith Billings, Taylor Morey iii
In fond memory of Abraham Pressman, master of the art, 1915(cid:802)2001.
Immortalized by his timeless writings and his legacy(cid:252)a gift
of knowledge for future generations.
To Anne Pressman, for her help and encouragement
on the third edition.
To my wife Diana for feeding the brute and allowing him
to neglect her, yet again!
Abraham I. Pressman, Keith Billings, Taylor Morey iv
Abraham I. Pressman, Keith Billings, Taylor Morey v
About the Authors
Abraham I. Pressman was a nationally known power supply consultant and lecturer. His background
ranged from an Army radar officer to over four decades as an analog-digital design engineer in industry. He
held key design roles in a number of significant (cid:256)firsts(cid:257) in electronics over more than a half century: the
first particle accelerator to achieve an energy over one billion volts, the first high-speed printer in the
computer industry, the first spacecraft to take pictures of the moon(cid:255)s surface, and two of the earliest
textbooks on computer logic circuit design using transistors and switching power supply design, respectively.
Mr. Pressman was the author of the first two editions of Switching Power Supply Design.
Keith Billings is a Chartered Electronic Engineer and author of the Switchmode Power Supply Handbook,
published by McGraw-Hill. Keith spent his early years as an apprentice mechanical instrument maker (at a
wage of four pounds a week) and followed this with a period of regular service in the Royal Air Force,
servicing navigational instruments including automatic pilots and electronic compass equipment. Keith went
into government service in the then Ministry of War and specialized in the design of special test equipment
for military applications, including the UK3 satellite. During this period, he became qualified to degree
standard by an arduous eight-year stint of evening classes (in those days, the only avenue open to the lower
middle-class in England). For the last 44 years, Keith has specialized in switchmode power supply design
and manufacturing. At the age of 75, he still remains active in the industry and owns the consulting company
DKB Power, Inc., in Guelph, Canada. Keith presents the late Abe Pressman(cid:255)s four-day course on power
supply design (now converted to a Power Point presentation) and also a one-day course of his own on
magnetics, which is the design of transformers and inductors. He is now a recognized expert in this field. It is
a sobering thought to realize he now earns more in one day than he did in a whole year as an apprentice.
Abraham I. Pressman, Keith Billings, Taylor Morey vi
Keith was an avid yachtsman for many years, but he now flies gliders as a hobby, having built a high-
performance sailplane in 1993. Keith (cid:256)touched the face of god,(cid:257) achieving an altitude of 22,000 feet in
wave lift at Minden, Nevada, in 1994.
Taylor Morey, currently a professor of electronics at Conestoga College in Kitchener, Ontario, Canada, is
coauthor of an electronics devices textbook and has taught courses at Wilfred Laurier University in Waterloo.
He collaborates with Keith Billings as an independent power supply engineer and consultant and previously
worked in switchmode power supply development at Varian Canada in Georgetown and Hammond
Manufacturing and GFC Power in Guelph, where he first met Keith in 1988. During a five-year sojourn to
Mexico, he became fluent in Spanish and taught electronics engineering courses at the Universidad Católica
de La Paz and English as a second language at CIBNOR biological research institution of La Paz, where he
also worked as an editor of graduate biology students(cid:255) articles for publication in refereed scientific journals.
Earlier in his career, he worked for IBM Canada on mainframe computers and at Global TV(cid:255)s studios in
Toronto.
Abraham I. Pressman, Keith Billings, Taylor Morey vii
Contents

Acknowledgments xxxiii
Preface xxxv

Part I Topologies

1 Basic Topologies 3
1.1 Introduction to Linear Regulators and Switching Regulators of the Buck 3

Boost and Inverting Types
1.2 Linear Regulator(cid:252)the Dissipative Regulator 4
1.2.1 Basic Operation 4
1.2.2 Some Limitations of the Linear Regulator 6
1.2.3 Power Dissipation in the Series-Pass Transistor 6
1.2.4 Linear Regulator Efficiency vs. Output Voltage 7
1.2.5 Linear Regulators with PNP Series-Pass Transistors for Reduced 9

Dissipation
1.3 Switching Regulator Topologies 10
1.3.1 The Buck Switching Regulator 10
1.3.1.1 Basic Elements and Waveforms of a Typical Buck Regulator 11
1.3.1.2 Buck Regulator Basic Operation 13
1.3.2 Typical Waveforms in the Buck Regulator 14
1.3.3 Buck Regulator Efficiency 15
1.3.3.1 Calculating Conduction Loss and Conduction-Related Efficiency 16
1.3.4 Buck Regulator Efficiency Including AC Switching Losses 16
1.3.5 Selecting the Optimum Switching Frequency 20
1.3.6 Design Examples 21
1.3.6.1 Buck Regulator Output Filter Inductor (Choke) Design 21
1.3.6.2 Designing the Inductor to Maintain Continuous Mode Operation 25
1.3.6.3 Inductor (Choke) Design 26
Abraham I. Pressman, Keith Billings, Taylor Morey viii

1.3.7 Output Capacitor 27
1.3.8 Obtaining Isolated Semi-Regulated Outputs from a Buck Regulator 30
1.4 The Boost Switching Regulator Topology 31
1.4.1 Basic Operation 31
1.4.2 The Discontinuous Mode Action in the Boost Regulator 33
1.4.3 The Continuous Mode Action in the Boost Regulator 35
1.4.4 Designing to Ensure Discontinuous Operation in the Boost Regulator 37
1.4.5 The Link Between the Boost Regulator and the Flyback Converter 40
1.5 The Polarity Inverting Boost Regulator 40
1.5.1 Basic Operation 40
1.5.2 Design Relations in the Polarity Inverting Boost Regulator 42
References 43
2 Push-Pull and Forward Converter Topologies 45
2.1 Introduction 45
2.2 The Push-Pull Topology 45
2.2.1 Basic Operation (With Master/Slave Outputs) 45
2.2.2 Slave Line-Load Regulation 48
2.2.3 Slave Output Voltage Tolerance 49
2.2.4 Master Output Inductor Minimum Current Limitations 49
2.2.5 Flux Imbalance in the Push-Pull Topology (Staircase Saturation Effects) 50
2.2.6 Indications of Flux Imbalance 52
2.2.7 Testing for Flux Imbalance 55
2.2.8 Coping with Flux Imbalance 56
2.2.8.1 Gapping the Core 56
2.2.8.2 Adding Primary Resistance 57
2.2.8.3 Matching Power Transistors 57
2.2.8.4 Using MOSFET Power Transistors 58
2.2.8.5 Using Current-Mode Topology 58
2.2.9 Power Transformer Design Relationships 59
2.2.9.1 Core Selection 59
2.2.9.2 Maximum Power Transistor On-Time Selection 60
2.2.9.3 Primary Turns Selection 61
2.2.9.4 Maximum Flux Change (Flux Density Swing) Selection 61
2.2.9.5 Secondary Turns Selection 63