A novel three-phase soft-switched converter with high power factor using a lossless snubber

Recently, three-phase converters with high power factor, especially using the discontinuous current mode (DCM), have been studied as novel rectifier circuits instead of conventional converters. In this circuit, the current of reactor is zero at turn on because of operating on DCM. Then ZCS (Zero Current Switching) is achieved. However it is necessary to turn off the switch at the maximum current. Then the switching losses increase at higher switching frequency. Therefore, soft-switching method using the lossless snubber is proposed. In this method, ZVS (Zero Voltage Switching) at the turn off can be achieved by a lossless snubber and ZCS at the turn on can be obtained by operating under the DCM. In this paper, the theoretical analysis, numerical analysis using PSPICE, and results of the experiments show the verification of the proposed converter. (C) 1999 Scripta Technica. Electr Eng Jpn, 129(3): 69-76, 1999.