Comparison of deadtime effects on the performance of DC-DC converters with GaN FETs and silicon MOSFETs

Switching loss is an important and often the dominant source of converter losses. While soft-switching can greatly reduce the impact of switching loss, hard-switching is often preferred due to the simplicity of design, control, and implementation. Wide bandgap (WBG) semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) have greatly reduced switching losses due to faster transition speeds, reduced output capacitance and reduction or elimination of reverse recovery. However, the high reverse voltage drop during deadtime and resulting conduction loss of WBG devices has led to the belief that deadtime management is more important than for silicon MOSFETs. This paper quantifies the effects of output capacitance, reverse recovery, and deadtime. It highlights the relationship between deadtime and reverse recovery, and provides experimental results showing that silicon MOSFETs can show far greater losses than GaN as a result of poor deadtime management.