Dual-Mode LLC Converter With Wide Voltage Gain in Narrow Switching Frequency Range

In this letter, a dual-mode LLC converter is proposed with a wide voltage gain in a narrow switching frequency range, which has the same semiconductor count with a traditional LLC converter and adopts split capacitors as the input and output filters. Both the primary and secondary windings of the transformer are center tapped, and the resonant tank is also split on both the ends of the primary winding. The proposed converter can operate in the full-bridge buck mode or the half-bridge boost mode by applying different driver patterns. The normalized resonant frequency is different in two modes. Hence, the wide voltage gain in a narrow switching frequency range can be achieved. Moreover, zero-voltage switching can be realized for switches in two modes. A 1-kW prototype is built to verify the effectiveness of the proposed converter.