Optimization Design Method for Full-Bridge LLC Resonant Converter Based on Fractional-Order Characteristics of Resonant Tank

The full-bridge LLC resonant converter is one of the most suitable converters for high-power, high-efficiency applications. Although the design methodologies for full-bridge LLC resonant converters are already well-established, the development of the fractional-order domain has brought new flexibility to converter design. Based on the fact that inductors and capacitors have fractional-order characteristics, this paper presents a de-normalized fractional-order FHA gain model, which reveals the impact of fractional-order characteristics of practical inductors and capacitors on the converter gain. By maintaining the convenience of the FHA design method, this work identifies the fractional orders of a resonant tank inductor and capacitor and incorporates them into the parameter design as part of the design requirements, making the design results more accurate than the conventional FHA design method. Specifically, compared with the conventional FHA-based design, the proposed approach improves the DC voltage gain margin of the full-bridge LLC converter by 26% and expands the ZVS operating range margin by 23.3%.