19.4.4 .Another Example 737

19.5 Exatt Charaeteristits ofthe Series and Parallel Resonant Converters 740

19.5.1 Series Resonant Converter 740

19.5.2 Parallel Re.sonant Converter 748

19.6 Stimmary of Key Points 752 References 752 Problems 755

20 Soft Switching 761

20.1 Soft-Switching Iiechani.sras of Semiconductor Device.4 762

20.1.1 Diode Switching 763

20.1.2 MOSFET Switching 765

20.1.3 IGBT Switching 768

20.2 The Zero-Curreiit-Switching Qiiasi-Resoiiant Switch Cell 768

20.2.1 Waveforms of the Half-Wave ZCS Quasi-Resonant Switch Ceil 770

20.2.2 The Average Terminal Waveforms 774

20.2.3 The Full-Wave ZCS Quasi-Resonant Switch Cell 779

20.3 Resonant Switch Topologies 781

20.3.1 The Zero-Voltage-Switthing Quasi-Resonant Switch 783

20.3.2 TheZero-Voitage-Switthing Multi-Resonant Switch 784

20.3.3 Quasi-Square-Wave Resonant Switches 787

20.4 Soft Switching in PWM Converters 790

20.4.1 TheZero-Voltage Transition Full-Bridge Converter 791

20.4.2 The Auxiliary Switch Approach 794

20.4.3 Auxiliary ResonantCoramutated Pole 796

20.5 Summary of Key Points 797 References 798 Problems 800

Appendices 803

Appendix A RIMS Values of Commonly-Observed Converter Waveforms SOS

A.l Some Common Waveforms 805

A.2 General Kecewise Waveform 809

Appendix В Simulation of Converters 813

B.l Averaged Switch Models for Continuous Conductiot) Mode 815

B.1.1 Basic CCM Averaged Switch Modei 815

B.1.2 CCM Subcircuit Model that Includes Switch Conduction Losses 816

B.1.3 Example: SEPIC DC Conveision Ratio and Efficiency 818

B.1.4 Example: Transient Response of a Buclc-Boost Converter 819

B.2 Combined CCM/DCM Averaged Switch Modei 822

B.2.1 Example: SEPIC Frequency Responses 825 B.2.2 Example: Loop Gain and Closed-Loop Responses

of a Buck Voltage Regulator 827

B.2.3 Example: DCM Boost Rectifier 832

B.3 Cuneut Programmeti Control 834

B.3,1 Current Programmed Mode Model for Simulaiion 834 B.3.2 Exiimple: Frequency Responses of a Buck Converter with

Cunent Programmed Control 837

References 840

Appendix С Middlebrooks Extra Element Theorem 843

C. 1 Basic Result 843 C.2 Derivation 846 C.3 Discussion 849 C.4 Examples 850

C.4.1 A Simple Transfer Fimction 850

C.4.2 An Unmodeled Element 855

C.4.3 Addition of an Input Filter to a Convener 857

C.4.4 Dependence of Transistor Cunent on Load in a Resonant Inverter 859

References 861

Appendix D Magnetics I>esign Tables 863

D. 1 Pot Core Data 864 D.2 EE Core Data 865 D.3 EC Core Data 866 D4 ETD Core Data 866 D.5 PQ Core Data 867 D.6 American Wire Gauge Data 868 References 869

Index 871

Preface

The obj&etive ofthe First Editioti was to serve as a testbtx)k for iiitrotitictory power electronics cotirses where the fiindainentals t)f power electronics are defined, rigorotisiy presented, and treated in siifficien depth so that students acquire the knowledge and skills needed to design practical power electnmic sys tems. The First Edition has indeed been adopted for use in power electronics courses at a nutriber o: schools. An additional goal was to contribute as a reference book for engineers who practice power eiec tronics design, and for students who want to develop their knowledge of the area beyond the level of introductory ctmnies. In the Second Edition, the basic objectives and philosophy ofthe First Edition have not been changed. The modifications include addition of a number of new topics aimed at better serving the expanded audience that includes students of introductory and more advanced courses, as well as practicing engineers looking for a reference book and a sotirce for further professional deveiopinent. Most ofthe chapters have been significantly revised and updated. Major additions include a new Chapter lOtm input filter design, a new Appendix В covering siinulation of converters, and a new Appendix С on Middiebrtxjks Extra Element Theorem. In addition to the introduction of new topics, we have made major revisions of the material to improve the flow and clarity of explanations and to provide additional specific results, in chapters covering averaged switch inodeling, dynamics of converters operating in discontinuous conduction mode, current inode control, magnetics design, pulse-width modulated rectifiers, and resonant and soft-switching converteni.

A completely new Chapter 10 covering input fiiter design has been added to the second addition. The problem of how the input filter affects the dynamics of the converter, often in a manner that degrades stability and performance of the converter system, is explained using Middiebrooks Extra Element Theorem. This design-oriented appn>ach is explained in detail in the new Appendix C. Simple conditions iire derived to allow filter damping so that converter transfer functions are not changed. Complete results for optimum filter damping are presented. The chapter concludes with a discussion about the design of multiple-section filters, illustrated by a design example.

Computer simulation based on the averaged switch modeling approach is presented in Appendix B, including PSpice models for continuous and discontinuous conductitm mode, and current-mode control. Extensive simulation examples include: finding the dc conversion ratio and efficiency of a SEPIC, plotting the transient response of a buck-boost converter, comparing the control-to-output transfer functions of a SEPIC operating in CCM and DCM, determining the loop gain, line-to-output transfer function, and load transient response of a closed-loop buck voltage regulator, finding the input current