Novel Wide Voltage Range Multi-Resonant Bidirectional DC-DC Converter

A high conversion ratio bidirectional multi-mode DC-DC resonant converter for electric vehicle onboard charger with a notch filter function has been proposed. Due to different resonant modes (LLC and LLC-C) and gain characteristics of the proposed converter can provide a wide voltage gain range. Firstly, when operating at the higher voltage gain, it operates in LLC mode taking advantage of zero voltage switching (ZVS) on the converter and zero current switching (ZCS) on the output rectifier. Secondly, over the low voltage gain, the circuit operates automatically in LLC-C mode. This exhibits notch filter function providing infinite impedance (resonant zero point (RZP)), fast wide voltage gain regulation over a limited frequency range with good over-current protection. The proposed bidirectional converter is operating in both LLC and LLC-C modes. The analysis and design of the proposed converter are included in the paper. Additionally, closed-loop frequency modulation control simulation has been carried for charging during regeneration and discharging during motoring mode, which provides constant output voltage even if the input voltage and load are varying over a wide range. Thus, the proposed 1kW converter can inhibit the high conversion efficiency along with wide voltage gain, making the converter suitable for electric vehicle applications.