Resonant converter with flying capacitors — Analysis and experiments

This paper presents a new resonant converter to achieve soft switching on power devices. Two full-bridge converters are connected in series to clamp the voltage stress of power switches at V_in/2. Thus, power MOSFETs with 650V voltage rating can be used for 1300V input voltage applications. Two flying capacitors are connected on the AC side of two full-bridge converters to automatically balance two split input capacitor voltages in every switching cycle. Two resonant tanks are used in the proposed converter to share load current and reduce the current stress of passive and active components. If the switching frequency is less than the series resonant frequency of the resonant tanks, power MOSFETs can be turned on under zero voltage switching and rectifier diodes can be turned off under zero current switching. The switching losses on power MOSFETs are reduced and the reverse recovery loss is improved. Experiments with a 1.5kW prototype are provided to demonstrate the performance of the proposed converter.