A method of junction temperature estimation for SiC power MOSFETs via turn-on saturation current measurement

Abstract

Maintaining the operating junction temperature of a SiC Power MOSFET within a safe and tolerable range is crucial not only for safety reasons, but also for reliable operation, as thermal transient is one of the major stressors that threaten a device’s life span. Conventional methods use thermal sensors for temperature monitoring. However, these sensors require extra space, and the measurement accuracy is affected by their position. Besides, they are unable to track the transient temperature variation owing to relatively slow response time. This paper proposes a new temperature sensor-less method to estimate the junction temperature of SiC power MOSFETs by measuring the device’s turn-on saturation current (ID,sat). The device’s square root of the saturation current (ID,sat) and threshold voltage (Vth) can be extracted and adopted as junction temperature estimators. Compared to the threshold voltage, the square root of the saturation current has the advantage of a shorter test time. The feasibility of this temperature estimation method has been experimentally verified. The results suggest that the proposed method can be used as an alternative for effective online junction temperature monitoring.