An LLC-Based Single-Stage Step-Up AC/DC Resonant Converter Without Boost Circuit for EV Charging With High Power Factor

Ac/dc converters are popularly utilized in modern industrial applications, telecom, and electric vehicle (EV) charging applications. Ac/dc converters are usually equipped with power factor correction (PFC) function circuits required by industrial standards. This paper proposes a single-stage step-up ac/dc LLC resonant converter with PFC function. The control of the LLC stage achieves PFC function and the first stage Boost circuits in traditional PFCs are eliminated. As a result, Boost circuit switching loss and related costs can also be eliminated. The resonant tank in the LLC stage achieves soft-switching to maintain high conversion efficiency. A variable frequency control strategy is utilized in the LLC stage to realize the PFC function. To verify the analysis and performance of the proposed converter, a 55/220 V, 400 W experiment and a 110/330 V, 800 W experiment are both carried out, which achieves a peak rated efficiency of 95.1% and a high power factor of 0.99.