An Asymmetrical Multi-mode Bidirectional PWM DC-DC Converter with High Voltage Gain

Traditional dual active bridge DC-DC converter adopt PWM method, but its voltage gain is less than 1. Traditional LLC resonant DC-DC converter has higher voltage gain than 1, but it adopt PFM method. This paper present a bidirectional PWM DC-DC converter with high voltage gain. The proposed converter has a similar structure with the traditional LLC resonant converter. By adding an auxiliary winding of resonant inductor Lr and a little power MOSFET, combining with some new modulation methods, the proposed converter has five voltage gain modes with PWM method. In forward operation, it has medium and low voltage gain modes. In backward operation, it has high, medium and low voltage gain modes. At high gain mode, the converter operates as an integrated boost + LLC resonant converter. At low gain mode, the converter operates as a simple flyback converter. The operation principle and voltage gain characteristics of each modes are analyzed in detail. Finally, A 100 kHz 450 W DC-DC converter prototype is built to verify the proposed method, experimental results verify the validity of the proposed converter.