: Due to ever increasing demand for processing in smaller space, high frequency power conversion is needed. At high frequency, semiconductor devices are subjected to high switching loss and increased electromagnetic interference (EMI). Soft switching techniques are proper solutions to decrease switching losses and EMI. The simplest method to obtain soft switching is to employ lossy snubbers. However they fail to increase the total efficiency. Resonant and quasi resonant converters are another method but in these converters the switch voltage and current stresses increase and also the control system is complex. Since 1994, ZVT, ZCT and ZCZVT converters are suggested. In these converters, the switch voltage and current stresses do not increase and also the control system is simple. In this thesis, various conventional ZVT, ZCT and ZCZVT converters are discussed and new family of ZVT and ZCT converters are proposed. In addition by combining ZVT and ZCT converters a new family of ZCZVT converters is introduced. Finally, a new method to create a family of isolated ZVT converters is proposed. In each section one of the proposed converters is analyzed and theoretical analysis is justified with experimental results. At the end, conclusions and suggestions are presented.
