Online Junction Temperature Estimation Method for SiC MOSFETs Based on the DC Bus Voltage Undershoot

Silicon carbide (SiC) power devices are promising in industrial applications. Junction temperature monitoring is greatly significant for improving the reliability of devices and systems. However, state-of-the-art SiC MOSFET junction temperature estimation methods generally have drawbacks of low resolution, difficult measurement, and complicated installation. In this article, a novel junction temperature estimation for SiC MOSFETs based on the dc bus voltage undershoot is proposed. The correlation between junction temperature and current change rate is analyzed and verified by experiments. The current change rate of each SiC MOSFET can be measured via the dc bus voltage undershoot because of the stray inductance of the bus commutation loop. The undershoot of the dc bus voltage during the turn-
on
transient displays a linear dependence on the junction temperatures of the corresponding SiC MOSFET. Hence, the dc bus voltage undershoot can be utilized for monitoring the junction temperatures of two SiC MOSFETs in the half-bridge. Besides, practical implementation and estimation errors are presented. The method proposed has high accuracy and resolution for junction temperature monitoring. Besides, the method proposed can reduce the complexity, size, and cost of the monitoring circuit. Moreover, the method proposed is noninvasive and easy to install. It is promising for SiC MOSFET junction temperature monitoring in practical applications.