Much has changed in the power conversion field since the author’s
previous book on switching power supply design (Switching and Linear
Power Supply, Power Converter Design, 1978).
The main goal of these changes has been to make the power supply
smaller. As integrated circuits packed more features in a smaller
volume, it became essential also to decrease the size of a system’s power
supply. Switching power supply packing density currently ranges from
2 to 6 load watts per cubic inch (W/in3) as compared to about 1 W/in3 a
decade ago. Newer resonant converter techniques offer a possibility of
20 to 40 W/in3.
Higher switching frequencies, made possible by power MOSFET
transistors, newer topologies, and integrated-circuit pulse-width-modulating
chips, which pack more control and supervisory features in
a smaller volume, have contributed to making present-day power
supplies smaller. All these new technologies are covered in this book.
It has been the author’s experience, in teaching a course on modern
switching power supply design to all levels of engineers from most of
the major American electronics companies, that those who have a
good understanding of the fundamental principles can easily solve
their day-to-day design problems as well as assess and adapt to new
technologies.
Thus, this book covers the new technologies in a tutorial way so that
the reader can understand the fundamental reasons for various effects.
Explanations for various significant waveshapes and explanations for
alternative design decisions are given. Care has been taken to avoid
offering “handy-dandy” design equations without showing how they
were derived. All equations that effect a design decision are derived
from fundamental relations.
Magnetics design is emphasized; for, the majority of power supply
designers are primarily circuits-oriented. They appreciate and can
analyze problems when they can see DC voltage levels, voltage spikes,
and waveshapes on an oscilloscope. But the locus of operation on a BH
loop cannot be seen on an oscilloscope. Thus, circuits designers too
often shy away from or do not fully understand magnetics design. They
leave that to a magnetics specialist who may not appreciate how
circuits characteristics effect magnetics design decisions. It is hoped
the emphasis on magnetics herein may help correct that problem.
This second edition of the book also includes chapters on the
currently hottest topics in the field: power factor correction, highfrequency
ballasts for fluorescent lamps, and low-input voltage
supplies for laptop computers.
Throughout this text and throughout the literature, idealized
voltage-current waveforms are often shown. But I feel it is very
valuable from a tutorial viewpoint to view actual Polaroid waveforms
taken at critical points on working circuits. Seeing an actual
photographed waveform with its spikes, rings, and oddities conveys a
great deal more information and confidence about a circuit than does
an idealized, hand-drawn waveform. Such photographed waveforms
are presented at critical points at various frequencies on some of the
most commonly used topologies.
This book is directed primarily to design engineers and engineering
students at the undergraduate and graduate level. It may also be of
significant value to people who are not directly involved in start-fromscratch
designs, and whose main interest is power supply design
analysis, design review, test, and debugging.
The material contained herein is a consolidation and, hopefully, a
simpler, clearer explanation and logical reorganization of the
highpoints of all the proven and practical aspects of modern switching
power supply technology. As such, credit for the material belongs to the
innumerable engineers, designers in industry, and universities that
have brought switching power supply technology to its present
advanced state.
Abraham I. Pressman
