A Bidirectional Liquid-Cooled GaN-based AC/DC Flying Capacitor Multi-Level Converter with Integrated Startup and Additively Manufactured Cold-Plate for Electric Vehicle Charging

Level II electric vehicle (EV) on-board chargers provide AC-DC conversion capability in order to charge on-board high-voltage (HV) batteries. Bidirectional EV chargers can allow the EV to also act as an AC source in vehicle-to-grid services. In both charging and inverter applications, it is desirable for chargers to have high power density, high power-handling capability, and low weight. This paper showcases the architecture and control of an optimized bidirectional EV charger system that can convert from both low-line (120 V AC) and high-line (240 V AC) AC voltages to a 400 V DC output. The operation and control of the complete system, thermal management, enhanced power stage design, and start-up procedure are discussed. Experimental results demonstrating DC-AC high power operation and system start-up are reported.