Optimal Design of a GaN-based high-efficiency Dual Active Bridge Converter

Dual active bridge (DAB) based DC-DC converters are attractive choices over LLC-based resonant converters for EV charging applications due to their constant frequency operation and full bidirectional power flow capability. GaN HEMTs are available commercially in the voltage range of 650V and it superior to state-of-the-art Si Super-junction MOSFET (Si SJMOS) due to their better conduction and switching performances. In this context, the paper provides an optimal design approach for GaN HEMT-based high-frequency DAB converter for EV charging applications. Single phase shift (SPS) modulation along with frequency variation is used to achieve wider zero voltage switching (ZVS) range. The specification of the converter assumes the input voltage is fixed to 400V and the output voltage varies in the range of 200-460V. The maximum output power is 6.6kW and the frequency is varied in the range of 400kHz to 600kHz. A hardware prototype is implemented to validate the design with 650V, 60A GaN HEMT. The designed converter can operate over a wide range of output voltage while maintaining the ZVS.