Parallel Resonant Converter with Flying Capacitor

This paper presents a parallel resonant converter for high input voltage applications. In order to reduce the voltage stress of active switches, two half-bridge converters are connected in series at high voltage side. Flying capacitor is adopted between two series half-bridge converters to automatically balance two input capacitor voltages. Pulse frequency modulation scheme is adopted to regulate the output voltage at the desired voltage level. Since the resonant circuit at the switching frequency is operated at the inductive load, the input current of the resonant circuit is lagging to the fundamental input voltage. Active switches can be easier to turn on at zero voltage switching. Two resonant circuits connected in parallel are adopted to reduce the current stress of transformer windings and rectifier diodes at low voltage side. Interleaved pulse-width modulation is used to control two resonant circuits and to reduce the current ripple at the output side. Finally, experiments based on a laboratory prototype are presented to verify the effectiveness of the proposed converter.