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.

Charge-trapping mechanisms observed in high-voltage GaN switches are responsible for the degradation of power converter efficiency due to modulation of the effective dynamic ON-resistance (RON) with respect to its static value. Dynamic RON degradation is typically dependent on the blocking voltage and the commutation frequency and is particularly significant in new technologies under development. The possibility to characterize this phenomenon on GaN switch samples directly on-wafer, under controlled operating conditions that resemble real operations of the DUT in a switching mode power converter is extremely valuable in the development phase of new technologies or for quality verification of production wafers. In this paper, we describe a setup that allows this characterization: dynamic RON degradation of on-wafer 600 V GaN switches is characterized as a function of the VDS blocking voltage, the VGS driving voltage, and at different temperatures. The dependency on the switching frequency is identified by measuring the current recovery of the switch after the application of blocking voltages of different durations.