A New Single-Stage Single-Switch AC-DC PFC Topology

In this paper, a new single-stage single-switch, flyback-forward based and isolated power factor correction (PFC) converter is proposed. The proposed converter provides high power factor (PF), low current stress, high efficiency, low cost, and tight output voltage regulation. Flyback and forward converters operate in discontinuous current mode (DCM) simultaneously. The flyback converter operates at full power, uses the leakage inductance and provides high PF, transfers most of the power to the output storage capacitor, and transfers the remaining power to the input storage capacitor. The forward converter is supplied by the input storage capacitor, operates with low power, transfers all power to the output, and also provides output regulation. Thus, high PF, near direct power transfer (NDPT), low current stress on the power switch, high efficiency and low cost are achieved. A detailed theoretical analysis of the proposed converter is carried out and is verified with an experimental prototype with 220V(AC) input voltage, 120V(DC) output voltage, 120 W output power, and 100 kHz switching frequency. In the converter, the peak current of the switch is decreased from 8.75 A to 5.5 A and the total efficiency is increased from 74 to 85% compared to the equivalent converter without NDPT at full power.