Switching Power Supplies A - Z

Preface

Acknowledgments

Chapter 1. The Principles of Switching Power Conversion

Introduction

Overview and Basic Terminology

Understanding the Inductor

Evolution of Switching Topologies

Chapter 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 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)

Worked Examples (2, 3, and 4)

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

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

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

Chapter 3. Off-Line Converter Design and Magnetics

Flyback Converter Magnetics

Chapter 4. The Topology FAQ

Questions and Answers

Chapter 5. Advanced Magnetics

Part 1: Energy Transfer Principles

Part 2: Energy to Core Sizes

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

Chapter 6. Component Ratings, Stresses, Reliability, and Life

Introduction

Stresses and Derating

Part 1: Ratings and Derating in Power Converter Applications

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

Part 3: Life Prediction of Aluminum Electrolytic Capacitors

Chapter 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

Chapter 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

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

Chapter 9. Discovering New Topologies

Part 1: Fixed-Frequency Synchronous Buck Topology

Part 2: Fixed-Frequency Synchronous Boost Topology

Part 3: Current-Sensing Categories and General Techniques

Part 4: The Four-Switch Buck-Boost

Part 5: Auxiliary Rails and Composite Topologies

Part 6: Configurations and “Topology Morphology”

Part 7: Other Topologies and Techniques

Chapter 10. Printed Circuit Board Layout

Introduction

Trace Section Analysis

Some Points to Keep in Mind During Layout

Thermal Management Concerns

Chapter 11. Thermal Management

Thermal Resistance and Board Construction

Historical Definitions

Empirical Equations for Natural Convection

Comparing the Two Standard Empirical Equations

Sizing Copper Traces

Natural Convection at an Altitude

Forced Air Cooling

Radiative Heat Transfer

Miscellaneous Issues

Chapter 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

Chapter 13. Advanced Topics

Part 1: Voltage Ripple of Converters

Part 2: Distributing and Reducing Stresses in Power Converters

Part 3: Coupled Inductors in Interleaved Buck Converters

Part 4: Load Sharing in Paralleled Converters

Chapter 14. The Front End of AC–DC Power Supplies

Overview

Part 1: Low-Power Applications

Part 2: High-Power Applications and PFC

Chapter 15. EMI Standards and Measurements

Part 1: Overview and Limits

Part 2: Measurements of Conducted EMI

Chapter 16. Practical EMI Line Filters and Noise Sources in Power Supplies

Part 1: Practical Line Filters

Part 2: DM and CM Noise in Switching Power Supplies

Chapter 17. Fixing EMI Across the Board and Input Filter Instability

Part 1: Practical Techniques for EMI Mitigation

Part 2: Modules and Input Instability

Chapter 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

DM Calculations at High Line

Practical CM Filter Design

Chapter 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

Index