A Mode‐Reconfigurable Dual‐Resonant‐Tank LLC Resonant Converter With Wide Gain Range and Its Control Strategy

ABSTRACT To address the limited gain range of conventional LLC resonant converters and the efficiency degradation under wide‐range regulation, a wide‐gain LLC resonant converter with a mode‐reconfigurable dual‐resonant‐tank structure is proposed. The proposed topology features two resonant tanks with identical resonant network parameters and transformers with different turns ratios. By reconfiguring the primary‐side bridge legs, the converter can switch among half‐bridge, full‐bridge, and hybrid full‐bridge/half‐bridge modes, thereby achieving enhanced gain regulation capability. Furthermore, an improved secondary‐side series rectification scheme is adopted to reduce the number of diodes, thereby lowering the cost as well as the conduction loss on the rectifier side and improving the overall efficiency. To avoid the frequency out‐of‐range issue that may occur with fixed voltage‐threshold mode switching, an adaptive mode‐switching method based on switching‐frequency margin is proposed, thereby enabling smooth mode transitions. Simulation and experimental results verify that the proposed converter achieves favorable gain regulation capability and high conversion efficiency over a wide output range.