Active Thermal Management for SiC MOSFETs Based on Equivalent Adjustment of Buffer Capacitor

Abstract

Junction temperature fluctuations are the most important factor in accelerating the aging and failure of SiC MOSFETs. An effective way to improve the reliability of SiC MOSFETs is to suppress or even smooth out the junction temperature fluctuation. This letter proposes an active thermal management technique to adjust the turn-off loss in SiC MOSFETs based on adjusting the buffer capacitance, thus smoothing out the junction temperature fluctuation. To realize online continuous capacitor adjustment, this letter further proposes an equivalent adjustment of the buffer capacitor based on the use of a delay switch. Using the SiC MOSFET in a 6 kW high-frequency inverter as an example, experimental results show that the proposed active thermal management technology can be used to completely smooth out the junction temperature fluctuation generated by a rated load fluctuation of 37.5%.