Operation modes of the GaN HEMT in high-frequency half-bridge converter

This paper presents a study of the GaN HEMT switching features conducted with the use of the half-bridge test converter rated at 2,5 kW. Results of simulation performed in LTSpice are verified by a series of experimental tests at the variable input voltage (up to 400 V) and switching frequency (up to 250 kHz). Three switch scenarios were analyzed: HEMT without the anti-parallel diode, HEMT with an anti-parallel SiC Schottky and HEMT with an additional parallel capacitor. Presented waveforms of drain-source voltage and drain current during switching processes and results of power losses measurements show significant reduction of switching power losses when anti-parallel diode or additional capacitor are applied. Furthermore, an impact of the dead-time length on power losses is also discussed and an optimal choice for assumed parameters of the converter is presented.