The cascade buck-boost PFC converter with soft switching

A new cascade buck-boost topology with passive lossless snubber is proposed in this paper,; it has been successfully used in PFC circuit of high voltage system. Switching losses and EMI noises are reduced by restricting di/dt of the diode reverse recovery current and dv/dt of IGBT collector-emitter voltage. The IGBT in the buck circuit operates at ZVS turn-off and ZCS turn-on. The freewheeling diode is also commutated with ZVS. An APFC prototype has been built in the laboratory to demonstrate the effects of the circuit. Power factor of this 380VAC/600W proof-of-prototype is 0.98 and less than 11% THD can be achieved.