Loss analysis during dead time and thermal study of gallium nitride devices

By virtue of the advantages in breakdown field strength and saturated electron speed, gallium nitride field-effect transistors (GaN FETs) have been attracting attentions as next generation power devices in recent years. Compared with silicon-based metal-oxidesemiconductor field-effect transistors (MOSFETs), GaN FETs have no intrinsic anti-parallel body diodes and exhibit poor reverse conduction characteristics. Thus it is necessary to optimize the dead time to not only avoid shoot-through current during the transient period in the single phase leg structure, but also to minimize reverse conduction power losses. Another characteristic of GaN FETs is their relatively low thermal conductivity. To satisfy the demands of higher power density, the thermal performance and cooling requirements of GaN FETs should be evaluated. In this paper, loss analysis during dead time and the thermal study of GaN FETs are presented. As a case study, a 200W GaN FETs based resonant converter is considered. The simulation and experimental results verify the validity of the theoretical analysis.