PFC THD Reduction and Efficiency Improvement by ZVS or Valley Switching

When a PFC is in discontinuous conduction mode the inductor current will resonant between the boost inductor and MOSFET parasite capacitance. The resonant current can be big enough to distort the PFC current significantly. This application note introduces a digital control scheme based on UCD3XXX to predict the position at which the resonant current first time rises back from negative to zero a