A single-switch single-stage quasi-active PFC converter with bus voltage following peak input voltage

In this paper a new single-switch quasi- active power factor correction (PFC) converter based on two flyback dc/dc modules is proposed. To achieve high efficiency, part of the input power is directly transferred to the load by dc/dc flyback module 1. The rest of the input power is stored in the dc bus capacitor and reprocessed by a smaller dc/dc flyback module 2. The dc bus capacitor and the dc/dc module 2 also serve as a regenerative snubber. Due to the direct power transfer, lower voltage stress on the dc bus capacitor is achieved. A quasi-active PFC circuit is added to improve the power factor. The quasi-active PFC circuit is driven by a magnetic switch using a third winding coupled to the transformer of the dc/dc module 1. The input current harmonics of the proposed converter can easily meet IEC 61000-3-2 Class D requirements. The dc bus capacitor voltage is always equal the peak input voltage regardless of the load condition. Operating principles, analysis, and simulation results are presented to verify the effectiveness of the proposed converter.