GaN and SiC Based 500kHz Resonant Bidirectional DC/DC Design for 800V OBCM Application

A 6.6kW 500kHz bidirectional isolated DC/DC converter based on GaN and SiC wide band gap (WBG) semiconductor devices is developed for 800V electric vehicle (EV) on-board charging, which is simpler and more reliable than the method of 800V output using multilevel topology. Firstly, the working characteristics of resonant DAB topology using phase-shift control are analyzed. Compared with the delay-time control strategy, it has the factures of narrow switching frequency range and small turn-off current, which is very suitable for high frequency applications of SiC devices. Secondly, a magnetic integrated high-frequency transformer was designed, and Maxwell software was adopted for simulation, comparison, and optimization. Compared with the traditional 90kHz transformer design, the volume was reduced by about 50%. Thirdly, based on the specifications of EV on-board charger, the loss breakdown calculation of the worst-case working condition of charging and discharging mode is carried out to verify the rationality of the design. Finally, based on water-cooled heat dissipation, a 500kHz 6.6kW 800V bidirectional DC/DC experimental platform was built. The full power output voltage range is form 550V to 900V, and the peak efficiency more than 98% at normal temperature, which verified the feasibility of the high-frequency hybrid application design of GaN and SiC devices.