The conventional bidirectional LLC resonant converter is difficult to obtain the required wide-voltage gain range in discharging mode because it operates as a series-resonant converter. In order to solve this problem, this paper proposes a design methodology of a bidirectional LLC resonant converter, which can achieve the monotonous voltage gain curve of the unidirectional LLC resonant converter in both charging and discharging modes by designing the resonant inductors using a coupled inductor and designing the winding structure of the transformer. To validate the proposed converter, a 3.6-kW experimental prototype is configured. Results showed that it achieved maximum efficiencies of 96.86% and 95.95% in the charging and discharging modes, respectively.
