Soft-switched Single-stage Isolated AC-DC Converter for High Power Applications

This paper proposes a soft-switched single-stage isolated AC-DC converter with a regenerative clamp circuit for high power applications. The proposed converter consists of a front-end diode bridge rectifier followed by an isolated DC-DC converter. The regenerative clamp circuit is connected across the primary winding of the high frequency transformer. It provides seamless commutation for the current flowing through the AC side filter inductor and the leakage inductor of the isolating transformer. Additionally, it recycles the energy stored in the clamp capacitor back to the DC bus capacitor twice in a switching cycle. All the devices present in the converter and the clamp circuit experience soft-switching during both turn-on and turnoff switching transients. The combination of the soft-switching and regeneration operation provides very high power conversion efficiency. The operation of the proposed single-stage isolated AC-DC converter is demonstrated in a SiC MOSFET based 1.5 kW laboratory prototype.