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 paper 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{7.7}\,\text{kW}$</tex-math></inline-formula> prototype with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{150}\,\text{V}\cdots \text{920}\,\text{V}$</tex-math></inline-formula> output voltage range validates the theoretical analyses, achieving 98.16% peak efficiency with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx \,5\%$</tex-math></inline-formula> improvement in light-load efficiency compared to similar designs reported in the literature.