Design of a 7.5 kW Dual Active Bridge Converter in 650 V GaN Technology for Charging Applications

High-voltage GaN switches offer low conduction and commutation losses compared with their Si counterparts, enabling the development of high-efficiency switching-mode DC-DC converters with increased switching frequency, faster dynamics, and more compact dimensions. Nonetheless, the potential of GaN switches can be fully exploited only by means of accurate simulations, optimal switch driving, suitable converter topology, accurate component selection, PCB layout optimization, and fast digital converter control. This paper describes the detailed design, simulation, and implementation of an air-cooled, 7.5 kW, dual active bridge converter exploiting commercial 650 V GaN switches, a compact planar transformer, and low ESL/ESR metal film capacitors. The isolated bidirectional converter operates at a 200 kHz switching frequency, with an output voltage range of 200-500 V at nominal 400 V input voltage, and a maximum output current of 28 A, with a wide full-power ZVS region. The overall efficiency at full power is 98.2%. This converter was developed in particular for battery charging applications, when bidirectional power flow is required.