A New PSPWM Converter for High Performance Welding Machines

Abstract

In the Full Bridge (FB) Phase Shifted (PS) PWM converter, external snubber capacitors are connected in parallel to IGBTs in order to decrease turn off losses. The ZVT condition is not provided at light loads, thus the parallel capacitors discharge through IGBT at turn on and this causes switching losses and failure risk of the IGBT. Capacitor discharge through IGBT restricts the use of high valued snubber capacitor, and turn off behavior of the IGBT cannot be improved at high currents. This problematic condition occurs at especially the lagging leg. In this study, a new method enabling the use of high-valued snubber capacitors with the lagging leg of the PSPWM converter is developed. Thanks to this new method, the turn off switching losses are decreased, and the performance of the converter is developed at high currents. The proposed converter is particularly suitable for high current applications such as welding machines.