High power factor forward AC-DC converter with low storage capacitor voltage stress

Dylan Dah-Chuan Lu

Forward converters generally exhibit poor power factor when employing in the AC-DC conversion, due to the presence of zero input current near the zero crossing of line input voltage. In this paper, a single-switch forward converter with high power factor and low storage capacitor voltage stress is proposed. By adding a stack up voltage on top of the reflected input voltage on the forward converter secondary, the dead angle of input current is eliminated. The storage capacitor voltage is also kept smaller than the peak input voltage throughout entire line and load conditions. Power factor correction and fast output regulation are achieved simultaneously by using only a single switch and a single voltage-feedback control loop. Parameters that affect the storage capacitor voltage and input current are examined. Experimental results showed the effectiveness of the proposed converter.