Switching Power Supplies A–Z 2nd Edition.pdf

发布时间：2022-06-14 发布人：admin 分类：说明书资料大小：24.10M 资料格式：pdf 举报版权申诉

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第1页.png

第1页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第2页.png

第2页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第3页.png

第3页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第4页.png

第4页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第5页.png

第5页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第6页.png

第6页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第7页.png

第7页 / 共769页

3f48455a-ee76-4010-8827-558ad2a95b32.pdf-第8页.png

第8页 / 共769页

Front Cover

Switching Power Supplies A–Z

Contents

Preface

Acknowledgments

1 The Principles of Switching Power Conversion

Introduction

Overview and Basic Terminology

Efficiency

Linear Regulators

Achieving High Efficiency through Switching

Basic Types of Semiconductor Switches

Semiconductor Switches Are Not “Perfect”

Achieving High Efficiency through the Use of Reactive Components

Early RC-Based Switching Regulators

LC-Based Switching Regulators

The Role of Parasitics

Switching at High Frequencies

Reliability, Life, and Thermal Management

Stress Derating

Advances in Technology

Understanding the Inductor

Capacitors/Inductors and Voltage/Current

The Inductor and Capacitor Charging/Discharging Circuits

The Law of Conservation of Energy

The Charging Phase and the Concept of Induced Voltage

The Effect of the Series Resistance on the Time Constant

The Inductor Charging Circuit with R = 0 and the “Inductor Equation”

The Duality Principle

The “Capacitor Equation”

The Inductor Discharge Phase

Flyback Energy and Freewheeling Current

Current Must Be Continuous, Its Slope Need Not Be

The Voltage Reversal Phenomenon

A Steady State in Power Conversion and the Different Operating Modes

The Voltseconds Law, Inductor Reset and Converter Duty Cycle

Using and Protecting Semiconductor Switches

Evolution of Switching Topologies

Controlling the Induced Voltage Spike by Diversion through a Diode

Achieving a Steady State and Deriving Useful Energy

The Buck-Boost Converter

Ground-Referencing Our Circuits

The Buck-Boost Configurations

The Switching Node

Analyzing the Buck-Boost

Properties of the Buck-Boost

Why Three Basic Topologies Only?

The Boost Topology

The Buck Topology

Advanced Converter Design

2 DC–DC Converter Design and Magnetics

DC Transfer Functions

The DC Level and the “Swing” of the Inductor Current Waveform

Defining the AC, DC, and Peak Currents

Understanding the AC, DC, and Peak Currents

Defining the “Worst-Case” Input Voltage

The Current Ripple Ratio “r”

Relating r to the Inductance

The Optimum Value of r

Do We Mean Inductor? or Inductance?

How Inductance and Inductor Size Depend on Frequency

How Inductance and Inductor Size Depend on Load Current

How Vendors Specify the Current Rating of an Off-the-shelf Inductor and How to Select It

What Is the Inductor Current Rating We Need to Consider for a Given Application?

The Spread and Tolerance of the Current Limit

Worked Example (1)

Current Limit Considerations in Setting r

Continuous Conduction Mode Considerations in Fixing r

Setting r to Values Higher than 0.4 when Using Low-ESR Capacitors

Setting r to Avoid Device “Eccentricities”

Setting r to Avoid Subharmonic Oscillations

Quick Selection of Inductors Using “L×I” and “Load Scaling” Rules

Worked Examples (2, 3, and 4)

The Current Ripple Ratio r in Forced Continuous Conduction Mode (“FCCM”)

Basic Magnetic Definitions

Worked Example (5) — When Not to Increase the Number of Turns

The “Field Ripple Ratio”

The Voltage-Dependent Equation in Terms of Voltseconds (MKS Units)

CGS Units

The Voltage-Dependent Equation in Terms of Voltseconds (CGS Units)

Core Loss

Worked Example (6) — Characterizing an Off-the-Shelf Inductor in a Specific Application

Estimating Requirements

Current Ripple Ratio

Peak Current

Flux Density

Copper Loss

Core Loss

DC–DC Converter Design and Magnetics

Temperature Rise

Calculating “Other” Worst-case Stresses and their Selection Criteria

Worst-case Core Loss

Worst-case Diode Dissipation

Note that the General Diode Selection Procedure is as Follows

Worst-case Switch Dissipation

Note that the General Switch Selection Procedure is as Follows

Worst-case Output Capacitor Dissipation

Note that the General Output Capacitor Selection Procedure is as Follows

Worst-case Input Capacitor Dissipation

Note that the General Input Capacitor Selection Procedure is as Follows

3 Off-Line Converter Design and Magnetics

Flyback Converter Magnetics

Polarity of Windings in a Transformer

Transformer Action in a Flyback and Its Duty Cycle

The Equivalent Buck-Boost Models

The Current Ripple Ratio for the Flyback

The Leakage Inductance

Zener Clamp Dissipation

Secondary-Side Leakages also Affect the Primary Side

Measuring the Effective Primary-side Leakage Inductance

Worked Example (7) — Designing the Flyback Transformer

Fixing the VOR and Vz

Turns Ratio

Maximum Duty Cycle (theoretical)

Effective Load Current on Primary and Secondary Sides

Duty Cycle

Actual Center of Primary and Secondary Current Ramps

Peak Switch Current

Voltseconds

Primary-Side Inductance

Selecting the Core

Number of Turns

Actual B-Field

Air Gap

Selecting the Wire Gauge and Foil Thickness

Forward Converter Magnetics

Duty Cycle

Worst-Case Input Voltage End

Window Utilization

Relating Core Size to Its Power Throughput

Worked Example (8) — Designing the Forward Transformer

Input Power

Selection of Core

Skin Depth

Thermal Resistance

Maximum B-Field

Voltµseconds

Number of Turns

Secondary Foil Thickness and Losses

Primary Winding and Losses

First Iteration

Second Iteration

Third Iteration

Fourth Iteration

Total Transformer Losses

4 The Topology FAQ

Questions and Answers

5 Advanced Magnetics: Optimal Core Selection

Part 1: Energy Transfer Principles

Overview of Topologies

The Energy Transfer Charts

Peak Energy Storage Requirements

Calculating Inductance Based on Desired Current Ripple

Part 2: Energy to Core Sizes

Magnetic Circuits and the Effective Length of Gapped Cores

Stored Energy in Gapped Cores and the z-Factor

Energy of a Gapped Core in Terms of the Volume of the Core

Part 3: Toroids to E-Cores

Part 4: More on AC–DC Flyback Transformer Design

Part 5: More on AC–DC Forward Converter Transformer Design

6 Component Ratings, Stresses, Reliability, and Life

Introduction

Stresses and Derating

Part 1: Ratings and Derating in Power Converter Applications

Operating Environments

Component Ratings and Stress Factors in Power Supplies

Diodes

MOSFETs

Capacitors

PCB

Mechanical Stresses

Part 2: MTBF, Failure Rate, Warranty Costs, and Life

MTBF

Warranty Costs

Life Expectancy and Failure Criteria

Reliability Prediction Methods

Demonstrated Reliability Testing (DRT)

Accelerated Life Testing

Part 3: Life Prediction of Aluminum Electrolytic Capacitors

7 Optimal Power Components Selection

Overview

The Key Stresses in Power Converters

Waveforms and Peak Voltage Stresses for Different Topologies

The Importance of RMS and Average Currents

Calculation of RMS and Average Currents for Diode, FET, and Inductor

Calculation of RMS and Average Currents for Capacitors

The Stress Spiders

Stress Reduction in AC–DC Converters

RCD Clamps versus RCD Snubbers

8 Conduction and Switching Losses

Switching a Resistive Load

Switching an Inductive Load

Switching Losses and Conduction Loss

A Simplified Model of the MOSFET for Studying Inductive Switching Losses

The Parasitic Capacitances Expressed in an Alternate System

Gate Threshold Voltage

The Turn-On Transition

The Turn-Off Transition

Gate Charge Factors

Worked Example

Turn-On

Turn-Off

Applying the Switching Loss Analysis to Switching Topologies

Worst-Case Input Voltage for Switching Losses

How Switching Losses Vary with the Parasitic Capacitances

Optimizing Driver Capability vis-à-vis MOSFET Characteristics

9 Discovering New Topologies

Part 1: Fixed-Frequency Synchronous Buck Topology

Using a FET (Safely) Instead of Diode

Birth of Dead Time

CdV/dt-Induced Turn-On

Counting on the Body-Diode

External (Paralleled) Schottky Diode

Synchronous (Complementary) Drive

Part 2: Fixed-Frequency Synchronous Boost Topology

Part 3: Current-Sensing Categories and General Techniques

DCR Sensing

The Inductorless Buck Cell

Lossless Droop Regulation and Dynamic Voltage Positioning

Part 4: The Four-Switch Buck-Boost

Part 5: Auxiliary Rails and Composite Topologies

Is It a Boost or Is It a Buck-Boost?

Understanding the Cuk, Sepic, and Zeta Topologies

Generating the Current Waveforms of the Cuk, Sepic, and Zeta Converters

Stresses in the Cuk, Sepic, and Zeta Topologies and Component Selection Criteria

Part 6: Configurations and “Topology Morphology”

Part 7: Other Topologies and Techniques

Hidden Auxiliary Rails and Symmetry

Multiple Outputs and the Floating Buck Regulator

Hysteretic Controllers

Pulse-Skipping Mode

Achieving Transformer Reset in Forward Converters

10 Printed Circuit Board Layout

Introduction

Trace Section Analysis

Some Points to Keep in Mind During Layout

Thermal Management Concerns

11 Thermal Management

Thermal Resistance and Board Construction

Historical Definitions

Empirical Equations for Natural Convection

Comparing the Two Standard Empirical Equations

“h” from Thermodynamic Theory

PCB Copper Area Estimate

Sizing Copper Traces

Natural Convection at an Altitude

Forced Air Cooling

Radiative Heat Transfer

Miscellaneous Issues

12 Feedback Loop Analysis and Stability

Transfer Functions, Time Constant, and the Forcing Function

Understanding “e” and Plotting Curves on Log Scales

Flashback: Complex Representation

Repetitive and Nonrepetitive Stimuli: Time Domain and Frequency Domain Analyses

The s-Plane

Laplace Transform Method

Disturbances and the Role of Feedback

Transfer Function of the RC Filter, Gain, and the Bode Plot

The Integrator Op-amp (“Pole-at-Zero” Filter)

Mathematics in the Log-Plane

Transfer Function of the Post-LC Filter

Summary of Transfer Functions of Passive Filters

Poles and Zeros

“Interactions” of Poles and Zeros

Closed and Open-Loop Gain

The Voltage Divider

Pulse-Width Modulator Transfer Function

Voltage (Line) Feedforward

Power Stage Transfer Function

Plant Transfer Functions of All the Topologies

Feedback-Stage Transfer Functions

Closing the Loop

Criteria and Strategy for Ensuring Loop Stability

Plotting the Open-Loop Gain for the Three Topologies

The ESR-Zero

High-Frequency Pole

Designing a Type 3 Op-Amp Compensation Network

Optimizing the Feedback Loop

Input Ripple Rejection

Load Transients

Type 1 and Type 2 Compensations

Transconductance Op-Amp Compensation

Simpler Transconductance Op-Amp Compensation

Compensating with Current-Mode Control

13 Advanced Topics: Paralleling, Interleaving, and Load Sharing

Part 1: Voltage Ripple of Converters

Buck Converter Input and Output Voltage Ripple

Part 2: Distributing and Reducing Stresses in Power Converters

Overview

Power Scaling Guidelines in Power Converters

Concept behind Paralleling and Interleaving of Buck Converters

Closed-Form Equations for RMS Stresses of Interleaved Buck Converter

Interleaved Boost PFC Converters

Interleaved Multioutput Converters

Part 3: Coupled Inductors in Interleaved Buck Converters

Overview

Part 4: Load Sharing in Paralleled Converters

Passive Sharing

Active Load Sharing

14 The Front End of AC–DC Power Supplies

Overview

Part 1: Low-Power Applications

The Charging and Discharging Phases

Increasing the Capacitance, Thereby Reducing tCOND, Causes High RMS Currents

The Capacitor Voltage Trajectory and the Basic Intervals

Tolerating High Input Voltage Ripple in AC–DC Switching Converters

How the Bulk Capacitor Voltage Ripple Impacts the Switching Converter Design

General Flyback Fault Protection Schemes

The Input Current Shape and the Capacitor Current

How to Interpret μF/W correctly

Worked Example using either Quick Lookup Numbers or the “Arctic Analogy”

Accounting for Capacitor Tolerances and Life

Holdup Time Considerations

Two Different Flyback Design Strategies for Meeting Holdup Requirements

Part 2: High-Power Applications and PFC

Overview

How to get a Boost Topology to exhibit a Sine-wave Input Current?

Anti-Synchronization Technique for PFC and PWM Stages

Capacitor RMS Current Calculations With and Without Anti-Synchronization

Interleaved Boost PFC Stages

Practical Issues in Designing PFC Stages

PFC Choke Design Guidelines

Core Losses in PFC Choke

Borderline Active PFC using Boost

15 EMI Standards and Measurements

Part 1: Overview and Limits

The Standards

EMI Limits

Some Cost-Related Rules-of-Thumb

EMI for Subassemblies

Electromagnetic Waves and Fields

Extrapolation

Quasi-Peak, Average, and Peak Measurements

Part 2: Measurements of Conducted EMI

Differential Mode and Common Mode Noise

Measuring Conducted EMI with a LISN

Simple Math for Estimating Maximum Conducted Noise Currents

Separating CM and DM Components for Conducted EMI Diagnostics

Near-Field Sniffers for Radiated EMI Diagnostics

16 Practical EMI Line Filters and Noise Sources in Power Supplies

Part 1: Practical Line Filters

Basic Safety Issues in EMI Filter Design

Safety Restrictions on the Total Y-Capacitance

Practical Line Filters

Examining the Equivalent DM and CM Circuits and Filter Design Hints

The Ground Choke

Some Notable Industry Experiences in EMI Filter Design

Part 2: DM and CM Noise in Switching Power Supplies

Main Source of DM Noise

The Main Source of CM Noise

Chassis-Mounting of Semiconductors

The CM Noise Source

The Road to Cost-Effective Filter Design

17 Fixing EMI Across the Board and Input Filter Instability

Part 1: Practical Techniques for EMI Mitigation

The Ground Plane

The Role of the Transformer in EMI

EMI from Diodes

Are We Going to Fail the Radiation Test?

Part 2: Modules and Input Instability

Practical Line Filters in DC–DC Converter Modules

18 The Math Behind the Electromagnetic Puzzle

Fourier Series in Power Supplies

The Rectangular Wave

The Sinc Function

The Envelope of the Fourier Amplitudes

Practical DM Filter Design

ESR Estimate

DM Calculations at High Line

DM Calculations at Low Line

Filter Safety Margin

Practical CM Filter Design

CM Calculations at High Line

19 Solved Examples

Part 1: FET Selection

Part 2: Conduction Losses in the FETs

Part 3: FET Switching Losses

Part 4: Inductor Loss

Part 5: Input Capacitor Selection and Loss

Part 6: Output Capacitor Selection and Loss

Part 7: Total Losses and Efficiency Estimate

Part 8: Junction Temperature Estimates

Part 9: Control Loop Design

Appendix

Further Reading

Index

Switching Power Supplies A–Z

This page intentionally left blank

Switching Power Supplies A–Z Sanjaya Maniktala AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO Newnes is an imprint of Elsevier

Newnes is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK 225 Wyman Street, Waltham, MA 02451, USA Copyright r 2012 Elsevier Ltd. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. Permissions may be sought directly from Elsevier's Science & Technology Rights Department in Oxford, UK: phone (144) (0) 1865 843830; fax (144) (0) 1865 853333; email: permissions@elsevier.com. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-12-386533-5 For information on all Newnes publications visit our web site at www.newnespress.com Typeset by MPS Limited, a Macmillan Company, Chennai, India www.macmillansolutions.com Printed in Great Britain 11 12 13 14 15 10 9 8 7 6 5 4

Contents Preface................................................................................................................. xv Acknowledgments ..................................................................................................xix Chapter 1: The Principles of Switching Power Conversion....................................... 1 Introduction .................................................................................................................. 1 Overview and Basic Terminology ............................................................................... 4 Efficiency......................................................................................................... 4 Linear Regulators ............................................................................................ 5 Achieving High Efficiency through Switching .............................................. 7 Basic Types of Semiconductor Switches........................................................ 8 Semiconductor Switches Are Not “Perfect” ................................................. 10 Achieving High Efficiency through the Use of Reactive Components ....... 11 Early RC-Based Switching Regulators ......................................................... 12 LC-Based Switching Regulators ................................................................... 13 The Role of Parasitics ................................................................................... 14 Switching at High Frequencies ..................................................................... 16 Reliability, Life, and Thermal Management................................................. 17 Stress Derating............................................................................................... 19 Advances in Technology ............................................................................... 20 Understanding the Inductor........................................................................................ 21 Capacitors/Inductors and Voltage/Current.................................................... 21 The Inductor and Capacitor Charging/Discharging Circuits........................ 22 The Law of Conservation of Energy ............................................................ 24 The Charging Phase and the Concept of Induced Voltage .......................... 24 The Effect of the Series Resistance on the Time Constant.......................... 26 The Inductor Charging Circuit with R 5 0 and the “Inductor Equation” .... 28 The Duality Principle .................................................................................... 29 The “Capacitor Equation” ............................................................................. 30 The Inductor Discharge Phase ...................................................................... 31 Flyback Energy and Freewheeling Current .................................................. 32 Current Must Be Continuous, Its Slope Need Not Be ................................. 32 The Voltage Reversal Phenomenon.............................................................. 34 v

vi Contents A Steady State in Power Conversion and the Different Operating Modes........................................................................................ 35 The Voltseconds Law, Inductor Reset and Converter Duty Cycle .............. 39 Using and Protecting Semiconductor Switches ............................................ 41 Evolution of Switching Topologies ........................................................................... 43 Controlling the Induced Voltage Spike by Diversion through a Diode ......................................................................................... 43 Achieving a Steady State and Deriving Useful Energy ............................... 45 The Buck-Boost Converter............................................................................ 46 Ground-Referencing Our Circuits ................................................................. 48 The Buck-Boost Configurations.................................................................... 48 The Switching Node...................................................................................... 49 Analyzing the Buck-Boost ............................................................................ 50 Properties of the Buck-Boost ........................................................................ 50 Why Three Basic Topologies Only?............................................................. 52 The Boost Topology...................................................................................... 53 The Buck Topology....................................................................................... 57 Advanced Converter Design ......................................................................... 59 Chapter 2: DCDC Converter Design and Magnetics.......................................... 61 DC Transfer Functions ............................................................................................... 62 The DC Level and the “Swing” of the Inductor Current Waveform........................ 63 Defining the AC, DC, and Peak Currents ................................................................. 66 Understanding the AC, DC, and Peak Currents ........................................................ 68 Defining the “Worst-Case” Input Voltage................................................................. 70 The Current Ripple Ratio “r” .................................................................................... 72 Relating r to the Inductance....................................................................................... 73 The Optimum Value of r ........................................................................................... 74 Do We Mean Inductor? or Inductance?..................................................................... 76 How Inductance and Inductor Size Depend on Frequency .......................... 77 How Inductance and Inductor Size Depend on Load Current .................................. 77 How Vendors Specify the Current Rating of an Off-the-shelf Inductor and How to Select It .............................................................................................. 78 What Is the Inductor Current Rating We Need to Consider for a Given Application?........................................................................................ 79 The Spread and Tolerance of the Current Limit ....................................................... 83 Worked Example (1) .................................................................................................. 86 Current Limit Considerations in Setting r .................................................... 87 Continuous Conduction Mode Considerations in Fixing r........................... 88 Setting r to Values Higher than 0.4 when Using Low-ESR Capacitors.................................................................................. 91 Setting r to Avoid Device “Eccentricities” .................................................. 91 Setting r to Avoid Subharmonic Oscillations............................................... 93

Contents vii Quick Selection of Inductors Using “L 3 I” and “Load Scaling” Rules................................................................................. 96 Worked Examples (2, 3, and 4) ................................................................................. 97 The Current Ripple Ratio r in Forced Continuous Conduction Mode (“FCCM”) ........................................................................................ 99 Basic Magnetic Definitions ......................................................................... 100 Worked Example (5) — When Not to Increase the Number of Turns .................. 103 The “Field Ripple Ratio” ............................................................................ 104 The Voltage-Dependent Equation in Terms of Voltseconds (MKS Units) ................................................................... 104 CGS Units.................................................................................................... 105 The Voltage-Dependent Equation in Terms of Voltseconds (CGS Units) .................................................................... 105 Core Loss ..................................................................................................... 105 Worked Example (6) — Characterizing an Off-the-Shelf Inductor in a Specific Application...................................................................................... 106 Estimating Requirements ............................................................................ 107 Current Ripple Ratio ................................................................................... 109 Peak Current ................................................................................................ 110 Flux Density ................................................................................................ 110 Copper Loss................................................................................................. 111 Core Loss ..................................................................................................... 112 DCDC Converter Design and Magnetics................................................. 113 Temperature Rise......................................................................................... 113 Calculating “Other” Worst-case Stresses and their Selection Criteria ................... 114 Worst-case Core Loss.................................................................................. 114 Worst-case Diode Dissipation ..................................................................... 115 Note that the General Diode Selection Procedure is as Follows ............... 116 Worst-case Switch Dissipation.................................................................... 116 Note that the General Switch Selection Procedure is as Follows .............. 118 Worst-case Output Capacitor Dissipation................................................... 118 Note that the General Output Capacitor Selection Procedure is as Follows............................................................................................. 118 Worst-case Input Capacitor Dissipation ..................................................... 119 Note that the General Input Capacitor Selection Procedure is as Follows............................................................................................. 120 Chapter 3: Off-Line Converter Design and Magnetics ........................................ 123 Flyback Converter Magnetics .................................................................................. 124 Polarity of Windings in a Transformer....................................................... 124 Transformer Action in a Flyback and Its Duty Cycle................................ 126 The Equivalent Buck-Boost Models ........................................................... 129 The Current Ripple Ratio for the Flyback.................................................. 131 The Leakage Inductance ............................................................................. 132

分享到：

赞收藏

资料库

Switching Power Supplies A–Z 2nd Edition.pdf

相关推荐

开发技术

热门标签

最新资料