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

The LLC resonant converter features its high efficiency and compact design but struggles with achieving a wide voltage gain. To address this challenge, multi-stage circuits, hybrid control strategies, and multi-mode operations are utilized, though these solutions increase the system's complexity. This paper presents an innovative LLC resonant converter with a stacked bridge structure, employing simple PFM and secondary turn-on/off control. By incorporating a stacked half-bridge primary and a reconfigurable multi-voltage rectifier, the proposed design extends the output voltage range within a narrow switching frequency range while reducing voltage stress on both the primary and secondary sides by half. The reconfigurable rectifier operates as a double-voltage rectifier at low output voltages and a quadruple-voltage rectifier at high output voltages. The converter adapts to varying voltage requirements, making it suitable for high voltage applications like on-board charging and DC fast charging. Experimental validation with a prototype operating at 400V input and 200-800V output at 500W demonstrates effective soft-switching across the voltage range and confirms the feasibility of the design.