Dead time optimization through loss analysis of an active-clamp flyback converter utilizing GaN devices

This paper presents an analysis of losses that occur during dead time in an active-clamp flyback converter utilizing Gallium Nitride based MOSFETs. This analysis is used to optimize the length of the dead-time period in order to minimize losses in the switching devices. When compared to silicon-based MOSFETs, GaN-based MOSFETs have lower switching losses and much higher reverse conduction losses, so it is not desirable to design for zero-voltage switching (ZVS) over a wide load range. The analysis presented in this paper finds an optimal trade-off between partial ZVS and reverse conduction losses, minimizing overall device switching losses and therefore increasing converter efficiency over the desired load range. A 15-W, four-output active-clamp flyback converter utilizing GaN devices at 1 MHz is designed and implemented using the recommended optimization. The experimental results confirm this analysis and result in a minimization of switching losses and an increase in converter efficiency.