A Novel Current-Fed Dual-Active-Bridge DC–DC Converter for Ultra-Wide Output Voltage Range Electric Vehicle Battery Charger

Universal dc fast chargers must accommodate a wide output voltage range to support various electric vehicle (EV) battery voltages. This article introduces a novel current-fed dual-active-bridge (CFDAB) converter for universal EV charging applications. The proposed converter enables single-stage, fixed-frequency power conversion while ensuring zero-voltage switching (ZVS) at turn-on for all the switches. Conventional CFDAB topologies employing phase-shift plus duty-ratio control experience significant variations in the pulsewidth of the transformer winding voltage when operating across a wide range of port voltages, resulting in increased high-frequency-link (HFL) conduction losses and limited soft-switching range. In contrast, the proposed topology decouples the pulsewidth of the transformer winding voltage from the duty ratio, allowing for reduced HFL conduction losses and full-range ZVS-on for all switches. Two modules of the proposed converter connected in input-parallel-output-parallel or input-parallel-output-series configuration enable the system to support a wide range of EV battery voltages. The operation of the proposed converter is analyzed in detail, and a closed-loop control scheme is developed to regulate the converter outputs during transients. A 7.7-kW prototype with a 150–920 V output voltage range validates the theoretical analyses, achieving 98.16% peak efficiency with $\approx \,5\%$ improvement in light-load efficiency compared to similar designs reported in the literature.