High-frequency isolated DC-DC converter with GaN HEMTs

Abstract

This paper presents a 325 to 24 V, 1 kW isolated uni-directional DC-DC converter, build with Gallium Nitride (GaN) High-Electron-Mobility Transistors (HEMTs) switching at frequencies of up to 250 kHz. The system is designed by means of LTspice simulations using precise device models. Primarily, a problem of overvoltage across HEMTs is studied, optimal selection of RC snubbers is presented and, finally, verified by a series of experimental tests. Presented waveforms of the drain - source voltage show significant reduction of voltage overshoots and change of resonant frequency values. Paper also presents results of laboratory tests, including specific waveforms and power loss/efficiency measurements for switching frequency range from 100 kHz to 250 kHz.