Research on a High Gain Ratio Dual LLC Resonant Converter
Conventional LLC resonant converters achieve wide voltage gain by substantially widening the switching frequency range, which causes a marked reduction in overall system efficiency. This paper proposes a high gain ratio dual LLC resonant converter (HGRD-LLC) that employs dual resonant tanks and distinct switch drive signal modulations. Through independent or combined operation of half-bridge and full-bridge LLC resonant converters, five operating modes with different gains are obtained. The converter retains the advantages of LLC resonant topologies across all modes while achieving a wide output voltage gain and improving efficiency. Voltage gain is derived using the fundamental harmonic approximation method, and zero-voltage switching (ZVS) constraints are explicitly defined. A 960 W experimental prototype with an output voltage range of 60–480 V was constructed to verify the feasibility of the proposed topology. Experimental results demonstrate that the converter achieves a wide gain range within a switching frequency range of 90–190 kHz, with gain ratios of 1:2:4:6:8 at the resonant frequency. The peak efficiency reaches 97.2%, and the maximum gain is 8.0, outperforming conventional solutions in terms of gain and efficiency. The proposed topology shows strong engineering application value for wide voltage gain requirements in renewable energy storage charging systems.