Analysis and Design of a Single-Stage Bridgeless Isolated AC-DC Resonant Converter for Programmable AC Power Source Applications

This paper proposes a single-stage bridgeless isolated AC-DC power factor correction (PFC) topology, and this topology can realize the function of step-up and the galvanic isolation for the AC input and DC output voltages through single-stage power conversion process. Firstly, the operation principle of the topology is analyzed in details. Then, by reasonably designing the series resonant parameters, the zero-voltage-switching (ZVS) turn-on for the power switches in the primary-side and zero-current-switching (ZCS) turn-off for the output rectifier diodes in the secondary-side of the transformer can also be achieved under wide load range, and the voltage stress of the power switches are also reduced based on the active clamping technology. The design procedure for the key components of the proposed converter is also derived. Finally, a 3 kW experimental prototype based on SiC power devices with 85 kHz switching frequency is built to verify the correctness and feasibility of the proposed topology, and the experimental results show a good performance. It can operates in a wide input grid voltage range, 95.7% of peak conversion efficiency and 3.9% of total harmonic distortion(THD) value for grid current could be obtained.