Page 281 - Rashid, Power Electronics Handbook

15

Resonant and Soft-Switching

Converters

Prof. S. Y. (Ron) Hui 15.1 Introduction..................................................................................... 271
Dr. Henry S. H. Chung 15.2 Classi®cation.................................................................................... 272
Department of Electronic 15.3 Resonant Switch ............................................................................... 272
Engineering 15.3.1 ZC Resonant Switch 15.3.2 ZV Resonant Switch
City University of Hong
Kong 15.4 Quasi-Resonant Converters................................................................. 273
Tat Chee Avenue, Kowloon, 15.4.1 ZCS-QRCs 15.4.2 ZVS-QRC 15.4.3 Comparisons Between ZCS and ZVS
Hong Kong 15.5 ZVS in High-Frequency Applications ................................................... 275
15.5.1 ZVS with Clamped Voltage 15.5.2 Phase-Shifted Converter with Zero Voltage
Transition
15.6 Multiresonant Converters (MRC) ........................................................ 280
15.7 Zero-Voltage-Transition (ZVT) Converters............................................ 282
15.8 Nondissipative Active Clamp Network.................................................. 283
15.9 Load Resonant Converters.................................................................. 284
15.9.1 Series Resonant Converters 15.9.2 Parallel Resonant Converters 15.9.3 Series-
parallel Resonant Converter
15.10 Control Circuits for Resonant Converters ............................................. 287
15.10.1 QRCs and MRCs 15.10.2 Phase-Shifted, ZVT FB Circuit
15.11 Extended-Period Quasi-Resonant (EP-QR) Converters............................ 289
15.11.1 Circuit Operation 15.11.2 Design Procedure
15.12 Soft-Switching and EMI Suppression.................................................... 293
15.13 Snubbers and Soft-Switching for High Power Devices............................. 293
15.14 Soft-Switching DC-AC Power Inverters................................................. 294
15.14.1 Resonant (Pulsating) dc Link Inverter 15.14.2 Active-Clamped Resonant dc Link
Inverter 15.14.3 Resonant dc Link Inverter with Low Voltage Stress 15.14.4 Quasi-
Resonant Soft-Switched Inverter [47] 15.14.5 Resonant Pole Inverter and Auxiliary
Resonant Commutated Pole Inverter
References ........................................................................................ 304

15.1 Introduction and stress. Dissipative passive snubbers are usually added to
the power circuits so that the dv=dt and di=dt of the power
Advances in power electronics in the last few decades have led devices can be reduced, and the switching loss and stress can
not only to improvements in power devices, but also to new be diverted to the passive snubber circuits. However, switching
concepts in converter topologies and control. In the 1970s, loss is proportional to switching frequency, thus limiting the
conventional pulsewidth modulatioin (PWM) power conver- maximum switching frequency of the power converters. Typi-
ters were operated in switched mode. Power switches have to cal converter switching frequency was limited to a few tens of
cut off the load current within the turn-on and turn-off times kilohertz (typically 20 to 50 kHz) in early 1980s. Stray induc-
under the hard switching conditions. Hard switching refers to tive and capacitive components in the power circuits and
the stressful switching behavior of the power electronic power devices still cause considerable transient effects, which
devices. The switching trajectory of a hard-switched power in turn give rise to electromagnetic interference (EMI)
device is shown in Fig. 15.1. During the turn-on and turn-off problems. Figure 15.2 shows both typical ideal switching
processes, the power device has to withstand high voltage and waveforms and practical switching waveforms of the switch
current simultaneously, which results in high switching losses voltage. Transient ringing effects are the major cause of EMI.

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