Application of GaN power transistors in a 2.5 MHz LLC DC/DC converter for compact and efficient power conversion

In this work a demonstrator with a switching frequency up to 2.5 MHz is shown. These comparatively high frequencies reduce the weight and the system costs of the resonant 3-kW-DC-DC-converter. The electrical properties of the implemented Gallium Nitride (GaN) power transistors enable high switching frequencies while maintaining high efficiency. The presented converter has a power density of approximately 3 W/cm³. The total efficiency of the converter is higher than 90 % for all operation points above 1/5 of the nominal load. Exceptionally high efficiency of 94.5 % can be reached at half of the nominal load and a switching frequency of 2 MHz. Possible improvements are defined and could be reached by adding a continuous dead time control as well as adapting the driver circuit of the synchronous rectification.