Reconfigurable LLC Resonant Converter for Wide Voltage Range and Reduced Voltage Stress in DC-Connected EV Charging Stations

Abstract

To meet the charging demands of current electric vehicles (400 V and 800 V) and next generation powertrain architectures (1200 V), this letter introduces a reconfigurable LLC resonant converter connected to dc charging stations, capable of supporting a wide output voltage range for low-, medium-, and high-voltage EV charging by selecting various inverter and rectification methods. Unlike traditional LLC pulse frequency modulation approaches, the proposed converter maintains high efficiency across the entire output range and operates at a narrow switching frequency. The converter design features a stacked structure on both primary and secondary sides, including stacked half-bridges, diodes, and capacitors, which halves the voltage stresses on switches and diodes. This configuration also possesses voltage self-balancing among the stacked capacitors. In addition, soft-switching is achieved throughout the wide voltage range. Finally, experimental results from a prototype with an 8:1 output voltage ratio validate the feasibility of the proposed scheme.