Soft-Switching PWM Full-Bridge Converters

Xinbo Ruan, Nanjing University of Aeronautics and Astronautics, China.

• About the Author xi Preface xiiiAcknowledgment xviiList of Abbreviations xix1 Topologies and Operating Principles of Basic Full-Bridge Converters 11.1 Introduction 11.1.1 Development Trends in Power Electronics Technology 11.1.2 Classification and Requirements of Power Electronics Converters 21.1.3 Classification and Characterization of dc–dc Converters 31.2 Isolated Buck-Derived Converters 41.2.1 Forward Converter 41.2.2 Push–Pull Converter 71.2.3 Half-Bridge Converter 101.2.4 Full-Bridge Converter 111.2.5 Comparison of Isolated Buck-Derived Converters 121.3 Output Rectifier Circuits 141.3.1 Half-Wave Rectifier Circuit 141.3.2 Full-Wave Rectifier Circuit 151.3.3 Full-Bridge Rectifier Circuit 171.3.4 Current-Doubler Rectifier Circuit 181.4 Basic Operating Principle of Full-Bridge Converters 211.4.1 Topologies of Full-Bridge Converters 211.4.2 Pulse-Width Modulation Strategies for Full-Bridge Converters 211.4.3 Basic Operating Principle of a Full-Bridge Converter with a Full-Wave Rectifier Circuit and a Full-Bridge Rectifier Circuit 211.4.4 Basic Operating Principle of a Full-Bridge Converter with a Current-Doubler Rectifier Circuit 241.5 Summary 32References 322 Theoretical Basis of Soft Switching for PWM Full-Bridge Converters 332.1 PWM Strategies for Full-Bridge Converters 332.1.1 Basic PWM Strategy 332.1.2 Definition of On-Time of Power Switches 362.1.3 A Family of PWM Strategies 362.2 Two Types of PWM Strategy 382.2.1 The Two Diagonal Power Switches Turn Off Simultaneously 392.2.2 The Two Diagonal Power Switches Turn Off in a Staggered Manner 412.3 Classification of Soft-Switching PWM Full-Bridge Converters 432.4 Summary 44Reference 443 Zero-Voltage-Switching PWM Full-Bridge Converters 453.1 Topologies and Modulation Strategies of ZVS PWM Full-Bridge Converters 453.1.1 Modulation of the Lagging Leg 453.1.2 Modulation of the Leading Leg 473.1.3 Modulation Strategies of the ZVS PWM Full-Bridge Converters 473.2 Operating Principle of ZVS PWM Full-Bridge Converter 493.3 ZVS Achievement of Leading and Lagging Legs 543.3.1 Condition for Achieving ZVS 543.3.2 Condition for Achieving ZVS for the Leading Leg 543.3.3 Condition for Achieving ZVS for the Lagging Leg 543.4 Secondary Duty Cycle Loss 553.5 Commutation of the Rectifier Diodes 553.5.1 Full-Bridge Rectifier 563.5.2 Full-Wave Rectifier 573.6 Simplified Design Procedure and Example 593.6.1 Turn Ratio of Transformer 593.6.2 Resonant Inductor 593.6.3 Output Filter Inductor and Capacitor 603.6.4 Power Devices 603.6.5 Load Range of ZVS 613.7 Experimental Verification 623.8 Summary 66References 664 Zero-Voltage-Switching PWM Full-Bridge Converters with Auxiliary-Current-Source Networks 674.1 Current-Enhancement Principle 684.2 Auxiliary Current-Source Network 694.3 Operating Principle of a ZVS PWM Full-Bridge Converter with Auxiliary-Current-Source Network 724.4 Conditions for Achieving ZVS in the Lagging Leg 784.5 Parameter Design 784.5.1 Parameter Selection for the Auxiliary-Current-Source Network 794.5.2 Determination of Lr, Cr, and Ic 794.5.3 Design Example 804.6 Secondary Duty Cycle Loss and Selection of Dead Time for the Drive Signals of the Lagging Leg 814.6.1 Secondary Duty Cycle Loss 814.6.2 Selection of Dead Time between Drive Signals of the Lagging Leg 824.6.3 Comparison with Full-Bridge Converter with Saturable Inductor 824.7 Experimental Verification 854.8 Other Auxiliary Current-Source Networks for ZVS PWM Full-Bridge Converters 874.8.1 Auxiliary Current-Source Networks with Uncontrolled Auxiliary Current Magnitude 874.8.2 Auxiliary Current-Source Networks with Controlled Auxiliary Current Magnitude 894.8.3 Auxiliary Current-Source Network with Auxiliary Current Magnitude Proportional to Primary Duty Cycle 894.8.4 Auxiliary Current-Source Network with Auxiliary Current Magnitude Adaptive to Load Current 914.8.5 Auxiliary Current-Source Networks with Adaptive Resonant Inductor Current 974.9 Summary 98References 985 Zero-Voltage-and-Zero-Current-Switching PWM Full-Bridge Converters 1015.1 Modulation Strategies and Topologies of a ZVZCS PWM Full-Bridge Converter 1015.1.1 Modulation of the Leading Leg 1015.1.2 Modulation of the Lagging Leg 1035.1.3 Modulation Strategies of ZVZCS PWM Full-Bridge Converters 1035.1.4 Method for Resetting the Primary Current at Zero State 1035.2 Operating Principle of a ZVZCS PWM Full-Bridge Converter 1105.3 Theoretical Analysis 1135.3.1 Peak Voltage of the Block Capacitor 1135.3.2 Achieving ZVS for the Leading Leg 1135.3.3 Maximum Effective Duty Cycle Deff max 1145.3.4 Achieving ZCS for the Lagging Leg 1145.3.5 Voltage Stress of the Lagging Leg 1145.3.6 Blocking Capacitor 1155.4 Simplified Design Procedure and Example 1155.4.1 Transformer Winding-Turns Ratio 1155.4.2 Calculation of Blocking Capacitance 1155.4.3 Verification of the Transformer Turns Ratio and Blocking Capacitance 1165.4.4 Dead Time between the Gate Drive Signals of the Leading Leg 1175.5 Experimental Verification 1175.6 Summary 119References 1206 Zero-Voltage-Switching PWM Full-Bridge Converters with Clamping Diodes 1216.1 Introduction 1216.2 Causes of Voltage Oscillation in the Output Rectifier Diode in ZVS PWM Full-Bridge Converters 1226.3 Voltage Oscillation Suppression Approach 1256.3.1 RC Snubber 1256.3.2 RCD Snubber 1256.3.3 Active Clamp Circuit 1266.3.4 Auxiliary Winding of Transformer and Clamping Diode Circuit 1266.3.5 Clamping Diode Circuit 1276.4 Operating Principle of the Tr-Lead-Type ZVS PWM Full-Bridge Converter 1286.5 Operating Principle of the Tr-Lag-Type ZVS PWM Full-Bridge Converter 1336.6 Comparisons of Tr-Lead-Type and Tr-Lag-Type ZVS PWM Full-Bridge Converters 1386.6.1 Clamping Diode Conduction Times 1386.6.2 Achievement of ZVS 1396.6.3 Conduction Loss in Zero State 1406.6.4 Duty Cycle Loss 1406.6.5 Effect of the Blocking Capacitor 1406.7 Experimental Verification 1436.8 Summary 146References 1477 Zero-Voltage-Switching PWM Full-Bridge Converters with Current Transformers to Reset the Clamping Diode Currents 1497.1 Introduction 1497.2 Operating Principle of the ZVS PWM Full-Bridge Converter with Clamping Diodes under Light Load Conditions 1507.2.1 Case I: 0.5Vin¨MZr1 < ILf (t1)¨MK < Vin¨MZr1 (Referring to Figure 7.2a) 1567.2.2 Case II: ILf (t1)¨MK < 0.5Vin¨MZr1 (Referring to Figure 7.2b) 1567.3 Clamping Diode Current-Reset Scheme 1587.3.1 Reset Voltage Source 1587.3.2 Implementation of the Reset Voltage Source 1607.4 Operating Principle of the ZVS PWM Full-Bridge Converter with Current Transformer 1627.4.1 Operating Principle under Heavy Load Conditions 1627.4.2 Operating Principle under Light Load Conditions 1677.5 Choice of Current Transformer Winding Turns Ratio 1737.5.1 Clamping Diode Current-Reset Time 1737.5.2 Output Rectifier Diode Voltage Stress 1747.5.3 Current Transformer Winding Turns Ratio 1747.6 Experimental Verification 1757.7 Summary 179References 1808 Zero-Voltage-Switching PWM Full-Bridge Converters with Current-Doubler Rectifiers 1818.1 Operating Principle 1828.2 Realization of ZVS for the Switches 1878.3 Design Considerations 1888.3.1 Transformer Winding Turns Ratio 1898.3.2 Output Filter Inductance 1898.3.3 Blocking Capacitor 1928.4 Experimental Results 1938.5 Summary 197References 198Appendix 199Bibliography 203Index 207