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`Power
`Supply
`Cookbook
`Second Edition
`
`Marty Brown
`
`Boston Oxford Johannesburg Melbourne New Delhi
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`Newnes is an imprint of Butterworth–Heinemann.
`Copyright © 2001 by Butterworth–Heinemann
`A member of the Reed Elsevier group
`All rights reserved.
`
`No part of this publication may be reproduced, stored in a retrieval system, or
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`environment.
`
`Library of Congress Cataloging-in-Publication Data
`Brown, Marty.
`Power supply cookbook / Marty Brown.—2nd ed.
`p. cm.
`Includes bibliographical references and index.
`ISBN 0-7506-7329-X
`1. Electric power supplies to apparatus—Design and construction.
`2. Power electronics.
`3. Electronic apparatus and appliances—power
`supply.
`I. Title.
`TK7868.P6 B76 2001
`621.381¢044—dc21
`
`00-050054
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`A catalogue record for this book is available from the British Library.
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`Preface
`
`ix
`
`Introduction xi
`
`1. The Role of the Power Supply within the System and the
`Design Program
`1.1 Getting Started. This Journey Starts with the First Question 1
`1.2 Power System Organization 2
`1.3 Selecting the Appropriate Power Supply Technology 3
`1.4 Developing the Power System Design Specification 5
`1.5 A Generalized Approach to Power Supplies: Introducing the
`Building-block Approach to Power Supply Design 8
`1.6 A Comment about Power Supply Design Software 9
`1.7 Basic Test Equipment Needed 9
`
`2. An Introduction to the Linear Regulator
`2.1 Basic Linear Regulator Operation 11
`2.2 General Linear Regulator Considerations 12
`2.3 Linear Power Supply Design Examples
`14
`2.3.1 Elementary Discrete Linear Regulator Designs 15
`2.3.2 Basic 3-Terminal Regulator Designs 15
`2.3.3 Floating Linear Regulators 18
`
`3. Pulsewidth Modulated Switching Power Supplies
`3.1
`The Fundamentals of PWM Switching Power Supplies 21
`3.1.1 The Forward-mode Converter 22
`3.1.2 The Boost-mode Converter
`24
`3.2
`The Building-block Approach to PWM Switching Power Supply
`Design 26
`3.3 Which Topology of PWM Switching Power Supply to Use? 28
`3.4
`The “Black Box” Considerations for Switching Power Supplies 34
`3.5
`Design of the Magnetic Elements 37
`3.5.1 The Generalized Design Flow of the Magnetic Elements 37
`3.5.2 Determining the Size of the Magnetic Core 38
`3.5.3 Designing the Forward-mode Transformer 40
`3.5.4 Designing the Flyback Transformer 42
`3.5.5 Designing the Forward-mode Filter Choke 46
`3.5.6 Designing the Mutually Coupled, Forward-mode Filter Choke 47
`3.5.7 Designing the dc Filter Choke 48
`3.5.8 Base and Gate Drive Transformers 50
`3.5.9 Winding Techniques for Switchmode Transformers
`3.6
`The Design of the Output Stages 56
`3.6.1 The Passive Output Stage
`58
`
`52
`
`Contents
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`Power Supply Cookbook
`Second Edition
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`vi
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`Contents
`
`60
`
`71
`
`3.6.2 Active Output Stages (Synchronous Rectifiers)
`3.6.3 The Output Filter 61
`3.7
`Designing the Power Switch and Driver Section 63
`3.7.1 The Bipolar Power Transistor Drive Circuit
`63
`3.7.2 The Power MOSFET Power Switch 66
`3.7.3 The IGBT as a Power Switch 69
`3.8
`Selecting the Controller IC 70
`3.8.1 Short Overview of Switching Power Supply Control
`3.8.2 Selecting the Optimum Control Method 72
`3.9
`Designing the Voltage Feedback Circuit.
`75
`3.10
`Start-up and IC Bias Circuit Designs
`80
`3.11 Output Protection Schemes
`82
`3.12 Designing the Input Rectifier/Filter Section 84
`3.13 Additional Functions Normally Associated with Power Supplies
`3.13.1 Synchronization of the Power Supply to an External Source
`90
`3.13.2 Input, Low Voltage Inhibit
`91
`3.13.3 Impending Loss of Power Signal
`3.13.4 Output Voltage Shut-down 93
`3.14 Laying Out the Printed Circuit Board 93
`3.14.1 The Major Current Loops 93
`3.14.2 The Grounds Inside the Switching Power Supply
`3.14.3 The AC Voltage Node
`98
`99
`3.14.4 Paralleling Filter Capacitors
`3.14.5 The Best Method of Creating a PCB for a Switching Power
`Supply 99
`100
`PWM Design Examples
`3.15
`3.15.1 A Board-level 10-Watt Step-down Buck Converter 100
`3.15.2 Low Cost, 28 Watt PWM Flyback Converter 105
`3.15.3 65 Watt, Universal AC Input, Multiple-output Flyback
`Converter
`114
`3.15.4 A 280 Watt, Off-line, Half-bridge Converter 122
`
`92
`
`96
`
`4. Waveshaping Techniques to Improve Switching Power Supply
`Efficiency
`135
`4.1
`Major Losses within the PWM Switching Power Supply
`4.1.1 The Major Parasitic Elements within a Switching Power Supply
`4.2
`Techniques for Reducing the Major Losses
`143
`4.3
`Snubbers 145
`4.3.1 Design of the Traditional Snubber 145
`4.3.2
`The Passive Lossless Snubber 146
`4.4
`The Active Clamp 148
`4.5
`Saturable Inductors to Limit Rectifier Reverse Recovery
`Current 148
`Quasi-resonant Converters 151
`4.6
`151
`4.6.1 Quasi-resonant Converter Fundamentals
`4.6.2 Quasi-resonant Switching Power Supply Topologies
`4.6.3 Designing the Resonant Tank Circuit
`156
`4.6.4
`Phase Modulated PWM Full-bridge Converters
`4.7
`High Efficiency Design Examples
`163
`4.7.1 A 10 Watt Synchronous Buck Converter 163
`
`155
`
`161
`
`90
`
`142
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`Contents
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`vii
`
`4.7.2 A 15 Watt, ZVS, Quasi-resonant, Current-mode Controlled Flyback
`Converter 170
`4.7.3 A Zero-voltage Switched Quasi-resonant Off-line Half-bridge
`Converter 176
`
`Appendix A. Thermal Analysis and Design
`187
`A.1 Developing the Thermal Model
`A.2
`Power Packages on a Heatsink (TO-3, TO-220,
`TO-218, etc.) 189
`Power Packages Not on a Heatsink (Free Standing)
`A.3
`A.4 Radial-leaded Diodes 191
`A.5
`Surface Mount Parts
`192
`A.6 Examples of Some Thermal Applications 193
`A.6.1 Determine the Smallest Heatsink (or Maximum Allowed
`Thermal Resistance) for an Application 193
`A.6.2 Determine the Maximum Power That Can Be Dissipated
`by a Three-Terminal Regulator at the Maximum Specified
`Ambient Temperature without a Heatsink 194
`A.6.3 Determine the Junction Temperature of a Rectifier with a
`Known Lead Temperature
`195
`
`190
`
`Appendix B. Feedback Loop Compensation
`B.1 The Bode Response of Common Circuits Encountered in
`Switching Power Supplies
`196
`B.2 Defining the Open Loop Response of the Switching Power
`Supply—The Control-to-Output Characteristics 201
`B.2.1 The Voltage-mode Controlled, Forward-mode
`Converter 201
`B.2.2 Flyback Converters and Current-mode Forward Converter
`Control-to-Output Characteristics
`203
`B.3 The Stability Criteria Applied to Switching Power
`Supplies 205
`B.4 Common Error Amplifier Compensation Techniques
`B.4.1 Single-pole Compensation 207
`B.4.2 Single-pole Compensation with In-band Gain
`Limiting 211
`B.4.3 Pole-zero Compensation 212
`B.4.4 2-Pole–2-Zero Compensation 216
`
`206
`
`Appendix C. Power Factor Correction
`C.1 A Universal Input, 180 Watt Active Power Factor Correction
`Circuit 225
`
`Appendix D. Magnetism and Magnetic Components
`D.1 Basic Magnetic Theory Applied to Switching Power
`Supplies 232
`D.2 Selecting the Core Material and Style
`
`236
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`viii
`
`Contents
`
`Appendix E. Noise Control and Electromagnetic Interference
`E.1 The Nature and Sources of Electrical Noise 241
`E.2 Typical Sources of Noise
`243
`E.3 Enclosure Design 245
`E.4 Conducted EMI Filters 245
`
`Appendix F. Miscellaneous Information
`F.1 Measurement Unit Conversions 250
`F.2 Wires 251
`
`References 255
`
`Index 257
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`Preface
`
`Power Supply Cookbook was written by a practicing design engineer for practic-
`ing design engineers. Through designing power supplies for many years, along
`with a variety of electronic products ranging from industrial control to satellite
`systems, I have acquired a great appreciation for the “systems-level” develop-
`ment process and the trade-offs associated with them. Many of the approaches
`I use involve issues outside the immediate design of the power supply and their
`impact on the design.
`Power Supply Cookbook, Second Edition has been updated with the latest
`advances in the field of efficient power conversion. Efficiencies of between 80
`to 95 percent are now possible using these new techniques. The major losses
`within the switching power supply and the modern techniques to reduce them
`are discussed at length. These include: synchronous rectification, lossless
`snubbers, and active clamps. The information on methods of control, noise
`control, and optimum printed circuit board layout has also been updated.
`As with the previous edition, the “cookbook” approach taken in Power Supply
`Cookbook, Second Edition facilitates information finding for both the novice and
`seasoned engineer. The information is organized so that the reader need only
`read the material for the degree of in-depth knowledge he or she wishes to
`acquire. Because of the enclosed design flow, the typical power supply can be
`designed schematically in less than 8 hours, which can cut weeks from the
`expected design period.
`The purpose of this book is not to advance the bastions of academia, but to
`offer the tried and true design approaches implemented by many engineers in
`the power field. It offers advice and examples which can be immediately applied
`to the reader’s own designs.
`
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`Introduction
`
`This book is an invaluable adjunct to those engineers wanting to better under-
`stand power supply operation in order to effectively implement the computer-
`aided design (CAD) tools available. The broad implementation and success of
`CAD tools, along with the internationalization of the world’s design resources,
`has led to competition that has shortened the typical product design cycle from
`more than a year to a matter of months. As a result, it is important for design
`engineers to locate and apply just the right amount of information without a
`long learning period.
`Power Supply Cookbook, Second Edition is organized in a rather unique
`manner and, if followed correctly, can greatly shorten the amount of time
`needed to design a power supply. By presenting intuitive descriptions of the
`power supply system’s operation along with commonly used circuit approaches,
`it is designed to help anyone with a working electronics knowledge to design a
`very complex switching power supply quickly.
`I developed the concept for Power Supply Cookbook after having spent many
`hours working with design engineers on their power supply designs and, subse-
`quently, my own designs.
`
`The “Cookbook” Method of Organization
`Power Supply Cookbook, Second Edition follows the same tried and true “cook-
`book” organization as its predecessor. This easy-to-use format helps readers
`quickly locate the power supply design sections they need without reading the
`book from start to finish. Additionally, the text follows the design flow that a
`seasoned power supply designer would follow. Circuit sections are designed in
`a way that provides information needed by subsequent circuit sections. Cover-
`age of more complicated design areas, such as magnetics and feedback loops,
`is presented in a step-by-step format to help designers reduce the opportunity
`for mistakes.
`The results of the calculations in this book lead to a conservative (“middle of
`the road”) design. The results are “calculated estimates” that can be adjusted
`one way or another to enhance a performance or a physical property of the
`power supply. These compromises are discussed in the appropriate sections of
`the text.
`For best results, the new reader should follow this flow:
`A. Read Chapter 1 on the role of the power supply within the system and
`design program. This chapter provides the reader with insight as to the
`role of the power supply within the overall system, and develops the power
`supply design specification.
`B. Read the introduction sections for the type of power supply you wish
`to develop (linear, pulsewidth modulated [PWM] switching, or high-
`efficiency).
`C. Follow the order of the design “flowchart” and refer to the appropriate
`section within the book. Within each section, read the basic operation of
`that subcircuit. Then choose a design implementation that would best
`
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`xii
`
`Introduction
`
`fit your requirements from the selection of common industry design
`approaches.
`D. Calculate the component values and ratings from the design equations
`using your particular set of operating conditions.
`E. “Paste” the resulting subcircuit into the main schematic and proceed to
`the next subcircuit to be designed.
`F. At the end of the “paper design” (estimated 8 to 12 hours), read the
`section on PCB layout and begin building the first prototype.
`G. Debug and test the prototype.
`H. Finalize the physical and electrical design in preparation for production
`release.
`The appendices are provided for those technical areas that are common
`among the various power supply technologies. They also present more detail
`for those designers who wish a deeper understanding of the subjects. The mate-
`rial on the design of basic PWM switching power supplies should be followed
`for all switching power supply designs. Chapter 4 describes how one can further
`enhance the overall efficiency of the power supply being designed.
`In short, this book is written for working engineers by a working engineer.
`I hope you find it infinitely useful.
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`1. The Role of the Power Supply within
`the System and Design Program
`
`The power supply assumes a very unique role within a typical system. In
`many respects, it is the mother of the system. It gives the system life by pro-
`viding consistent and repeatable power to its circuits. It defends the system
`against the harsh world outside the confines of the enclosure and protects its
`wards by not letting them do harm to themselves. If the supply experiences a
`failure within itself, it must fail gracefully and not allow the failure to reach the
`system.
`Alas, mothers are taken for granted, and their important functions are not
`appreciated. The power system is routinely left until late in the design program
`for two main reasons. First, nobody wants to touch it because everybody wants
`to design more exciting circuits and rarely do engineers have a background in
`power systems. Secondly, bench supplies provide all the necessary power during
`the system debugging stage and it is not until the product is at the integration
`stage that one says “Oops, we forgot to design the power supply!” All too fre-
`quently, the designer assigned to the power supply has very little experience
`in power supply design and has very little time to learn before the product is
`scheduled to enter production.
`This type of situation can lead to the “millstone effect” which in simple terms
`means “You designed it, you fix it ( forever).” No wonder no one wants to touch
`it and, when asked, disavows any knowledge of having ever designed a power
`supply.
`
`1.1 Getting Started. This Journey Starts with
`the First Question
`
`In order to produce a good design, many questions must be asked prior to the
`beginning of the design process. The earlier they are asked the better off you
`are. These questions also avoid many problems later in the design program due
`to lack of communication and forethought. The basic questions to be asked
`include the following.
`
`From the marketing department
`1. From what power source must the system draw its power? There are
`different design approaches for each power system and one can also get
`information as to what adverse operating conditions are experienced
`for each.
`
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`2
`
`Role of the Power Supply within the System and Design Program
`
`2. What safety and radio frequency interference and electromagnetic inter-
`ference (RFI/EMI) regulations must the system meet to be able to be sold
`into the target market? This would affect not only the electrical design but
`also the physical design.
`3. What is the maintenance philosophy of the system? This dictates what
`sort of protection schemes and physical design would match the
`application.
`4. What are the environmental conditions in which the product must
`operate? These are temperature range, ambient RF levels, dust, dirt,
`shock, vibration, and any other physical considerations.
`5. What type of graceful degradation of product performance is desired when
`portions of the product fail? This would determine the type of power
`busing scheme and power sequencing that may be necessary within the
`system.
`
`From the designers of the other areas of the product
`1. What are the technologies of the integrated circuits that are being used
`within the design of the system? One cannot protect something, if one
`doesn’t know how it breaks.
`2. What are the “best guess” maximum and minimum limits of the load
`current and are there any intermittent characteristics in its current demand
`such as those presented by motors, video monitors, pulsed loads, and so
`forth? Always add 50 percent more to what is told to you since these
`estimates always turn out to be low. Also what are the maximum excur-
`sions in supply voltage that the designer feels that the circuit can with-
`stand. This dictates the design approaches of the cross-regulation of the
`outputs, and feedback compensation in order to provide the needs of the
`loads.
`3. Are there any circuits that are particularly noise-sensitive? These include
`analog-to-digital and digital-to-analog converters, video monitors, etc.
`This may dictate that the supply has additional filtering or may need to be
`synchronized to the sensitive circuit.
`4. Are there any special requirements of power sequencing that are neces-
`sary for each respective circuit to operate reliably?
`5. How much physical space and what shape is allocated for the power supply
`within the enclosure? It is always too small, so start negotiating for your
`fair share.
`6. Are there any special interfaces required of the power supply? This would
`be any power-down interrupts, etc., that may be required by any of the
`product’s circuits.
`This inquisitiveness also sets the stage for the beginning of the design by defin-
`ing the environment in which the power supply must operate. This then forms
`the basis of the design specification of the power supply.
`
`1.2 Power System Organization
`
`The organization of the power system within the final product should com-
`plement the product philosophy. The goal of the power system is to dis-
`tribute power effectively to each section of the entire product and to do it in a
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`1.3 Selecting the Appropriate Power Supply Technology
`
`3
`
`fashion that meets the needs of each subsection within the product. To accom-
`plish this, one or more power system organization can be used within the
`product.
`For products that are composed of one functional “module” that is insepa-
`rable during the product’s life, such as a cellular telephone, CRT monitor, RF
`receiver, etc., an integrated power system is the traditional system organization.
`Here, the product has one main power supply which is completely self-contained
`and outputs directly to the product’s circuits. An integrated power system may
`actually have more than one power supply within it if one of the load circuits
`has power demand or sequencing requirements which cannot be accommodated
`by the main power supply without compromising its operation.
`For those products that have many diverse modules that can be reconfigured
`over the life of the product, such as PCB card cage systems and cellular tele-
`phone ground stations, etc., then the distributed power system is more appro-
`priate. This type of system typically has one main “bulk” power supply that
`provides power to a bus which is distributed throughout the entire product. The
`power needs of any one module within the system are provided by smaller,
`board-level regulators. Here, voltage drops experienced across connectors and
`wiring within the system do not bother the circuits.
`The integrated power system is inherently more efficient (less losses). The
`distributed system has two or more power supplies in series, where the overall
`power system efficiency is the product of the efficiencies of the two power sup-
`plies. So, for example, two 80 percent efficient power supplies in series produces
`an overall system efficiency of 64 percent.
`The typical power system can usually end up being a combination of the two
`systems and can use switching and linear power supplies.
`The engineer’s motto to life is “Life is a tradeoff” and it comes into play here.
`It is impossible to design a power supply system that meets all the requirements
`that are initially set out by the other engineers and management and keep it
`within cost, space, and weight limits. The typical initial requirement of a power
`supply is to provide infinitely adaptable functions, deliver kilowatts within zero
`space, and cost no money. Obviously, some compromise is in order.
`
`1.3 Selecting the Appropriate Power Supply Technology
`
`Once the power supply system organization has been established, the designer
`then needs to select the technology of each of the power supplies within the
`system. At the early stage of the design program, this process may be iterative
`between reorganizing the system and the choice of power supply technologies.
`The important issues that influence this stage of the design are:
`
`1. Cost.
`2. Weight and space.
`3. How much heat can be generated within the product.
`4. The input power source(s).
`5. The noise tolerance of the load circuits.
`6. Battery life (if the product is to be portable).
`7. The number of output voltages required and their particular characteris-
`tics.
`8. The time to market the product.
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`4
`
`Role of the Power Supply within the System and Design Program
`
`The three major power supply technologies that can be considered within a
`power supply system are:
`
`1. Linear regulators.
`2. Pulsewidth modulated (PWM) switching power supplies.
`3. High efficiency resonant technology switching power supplies.
`
`Each of these technologies excels in one or more of the system considera-
`tions mentioned above and must be weighed against the other considerations
`to determine the optimum mixture of technologies that meet the needs of
`the final product. The power supply industry has chosen to utilize each of the
`technologies within certain areas of product applications as detailed in the
`following.
`
`Linear
`Linear regulators are used predominantly in ground-based equipments where
`the generation of heat and low efficiency are not of major concern and also where
`low cost and a short design period are desired. They are very popular as board-
`level regulators in distributed power systems where the distributed voltage is less
`than 40 VDC. For off-line (plug into the wall) products, a power supply stage
`ahead of the linear regulator must be provided for safety in order to produce
`dielectric isolation from the ac power line. Linear regulators can only produce
`output voltages lower than their input voltages and each linear regulator can
`produce only one output voltage. Each linear regulator has an average efficiency
`of between 35 and 50 percent. The losses are dissipated as heat.
`
`PWM switching power supplies
`PWM switching power supplies are much more efficient and flexible in their
`use than linear regulators. One commonly finds them used within port-
`able products, aircraft and automotive products, small instruments, off-line
`applications, and generally those applications where high efficiency and
`multiple output voltages are required. Their weight is much less than that of
`linear regulators since they require less heatsinking for the same output ratings.
`They do, however, cost more to produce and require more engineering
`development time.
`
`High efficiency resonant technology switching power supplies
`This variation on the basic PWM switching power supply finds its place in appli-
`cations where still lighter weight and smaller size are desired, and most impor-
`tantly, where a reduced amount of radiated noise (interference) is desired. The
`common products where these power supplies are utilized are aircraft avionics,
`spacecraft electronics, and lightweight portable equipment and modules. The
`drawbacks are that this power supply technology requires the greatest
`amount of engineering design time and usually costs more than the other two
`technologies.
`
`The trends within the industry are away from linear regulators (except for
`board-level regulators) towards PWM switching power supplies. Resonant
`and quasi-resonant switching power supplies are emerging slowly as the
`technology matures and their designs are made easier. To help in the selec-
`tion, Table 1–1 summarizes some of the trade-offs made during the selection
`process.
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`1.4 Developing the Power System Design Specification
`
`5
`
`Table 1–1 Comparison of the Four Power Supply Technologies
`Resonant
`Transition
`Switching
`Regulator
`
`PWM Switching
`Regulator
`
`Linear
`Regulator
`
`Cost
`Mass
`RF Noise
`Efficiency
`Multiple outputs
`Development time
`to production
`
`Low
`High
`None
`35–50%
`No
`1 week
`
`High
`Low-medium
`High
`70–85%
`Yes
`8 person-monthsa
`
`5 person-monthsb
`
`High
`Low-medium
`Medium
`78–92%
`Yes
`10 person-
`monthsa
`8 person-
`months
`
`a Based upon a reasonable level of experience and facilities.
`b With the use of this book.
`
`Quasi-Resonant
`Switching
`Regulator
`
`Highest
`Low-medium
`Medium
`78–92%
`Yes
`10 person-monthsa
`
`8 person-monthsb
`
`1.4 Developing the Power System Design Specification
`
`Before actually designing the power system, the designer should develop the
`power system design specification. The design specification acts as the perfor-
`mance goal that the ultimate power supply must meet in order for the entire
`product to meet its overall performance specification. Once developed, it should
`be viewed as a semi-firm document and should only be changed after the needs
`of the product formally change.
`When developing the design specification, the power supply designer must
`keep in mind what is a reasonable requirement and what is an idealistic require-
`ment. Engineers not experienced in power supply design often will produce
`requirements on the power supply that either will cost an unnecessary fortune
`and take up too much space or will be impossible to meet with the present state
`of the technology. Here the power supply designer should press the other engi-
`neers, managers, and marketers for compromises that will prompt them to
`review their requirements to decide what they can actually live with.
`The power system specification will be based upon the questions that should
`previously have been asked of the other departments involved in defining and
`designing the product. Some of the requirements can be anticipated to grow,
`such as the current needed by various subsystems within the product. Always
`add 25 to 50 percent to the output current capabilities of the power supply
`during the design process to accommodate this inevitable event. Also, the space
`allocated to the power system and its cost will almost always be less than what
`will be finally required. Some negotiations will be in order. Since the power
`system is a support function within the product, its design will always be modi-
`fied in reaction to design issues within the other sections of the product. This
`will always make the power supply design the last circuit to be released for pro-
`duction. Recognizing and addressing these potential trouble areas early in the
`design period will help avoid delays later in the program.
`To develop a good design specification, the designer should understand the
`meaning of the terms used within the power supply field. These are measurable
`
`Netlist Ex 2020
`Samsung v Netlist
`IPR2022-00996
`
`

`

`6
`
`Role of the Power Supply within the System and Design Program
`
`power supply parameters with a common set of test conditions that the actual
`design affects. These parameters are the following.
`
`Input voltage
`Vin(nom)
`
`Vin(low)
`
`Vin(hi)
`
`input voltage
`
`The input voltage at which the product expects to
`operate for >99 percent of its life.
`The
`lowest anticipated operational
`(brown-out).
`The highest anticipated operational average input
`voltage.
`Line Frequency(s) dc, 50, 60, or 400 Hz, etc.
`Include any adverse operating conditions that may require the supply to operate
`outside the conventional specifications such as:
`Dropout
`A period of time over which the input line voltage
`completely disappears (the specification is typically
`8 mS for 60 Hz ac off-line applications).
`A defined period of time where the input voltage will
`exceed the Vin(hi) specification that the unit must
`survive and during which it may need to operate.
`These are very high voltage “spikes” (+/-) that are
`characteristic of the input power system.
`Emergency operation Any operation required of the product during any
`adverse operating periods. This may be because the
`product’s function is so critical for the survival of the
`operator of the unit, that it must operate to just short
`of its own destruction.
`
`Surge
`
`Transients
`
`Input current
`Iin(max) This is the maximum average input current. Its maximum limit may
`be specified by a safety regulatory agency.
`
`Output voltage(s)
`Vout(rated) The nominal output voltage (ideal).
`The output voltage below which the load should be inhibited or
`Vout(min)
`turned off.
`Vout(max) The maximum output voltage under which normal operation of the
`load circuits can operate.
`The voltage at which the loads reach their destructive limits.
`Vout(abs)
`Ripple voltage (switching power supplies) This is measured in peak-to-peak
`volts, and its frequency and level should be acceptable to the load circuits.
`
`Output current
`Iout(rated) The maximum average current that will be drawn from an
`output.
`The minimum current that will be drawn from the output during
`normal operation.
`The maximum current limit that should be delivered into a short-
`circuited load.
`
`Iout(min)
`
`Isc
`
`Netlist Ex 2020
`Samsung v Netlist
`IPR2022-00996
`
`

`

`1.4 Developing the Power System Design Specification
`
`7
`
`Describe any unusual load demand characteristics related to any output. These
`consist of intermittent loads such as motors, CRTs, etc., and also any loads
`that may be removed from or added to the system as part of an overall system
`architecture, such as probes, handsets, and the like.
`Dynamic load response time: This is the amount of time it requires the power
`supply to recover to within load regulation limits in response to a step
`change in the load.
`Line regulation: Percentage change in the output voltage(s) in response to a
`change in the input voltage.
`
`V
`(
`o hi-in
`Line Reg.
`V
`(
`)
`
`o nom-in
`Load regulation: Percentage change in the output voltage(s) in response to a
`change in load current from one-half rated to rated load current.
`
`=
`
`-
`
`V
`(
`o lo-in
`
`)
`
`)
`
`(
`)
`100 %
`
`◊
`
`(1.0)
`
`=
`
`-
`
`V
`(
`o half-load
`
`)
`
`)
`
`◊
`
`(
`)
`100 %
`
`V
`(
`o full-load
`Load Reg.
`V
`(
`)
`
`o rated-load
`Overall efficiency: This will determine how much heat will be generated within
`the product and whether any heatsinking will be needed in the physical
`design.
`
`(1.1)
`
`(
`)
`100 %
`
`◊
`
`(1.3)
`
`P P
`
`in
`
`out
`
`Effic.
`
`=
`
`Protections
`䊉 Input fusing limits.
`䊉