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 charging applications. AC/DC converters are usually equipped with power factor correction (PFC) function circuits required by industrial standards. This article proposes a single-stage step-up ac/dc
LLC
resonant converter with a 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 a 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.