Turn-OFF Delay Time Based Online Junction Temperature Monitoring for SiC MOSFETs Over Aging

Junction temperature (T_j) is a crucial quantity for monitoring the working condition of semiconductors in power converter operation. Online T_j measurement can be achieved by the thermo-sensitive electrical parameters (TSEPs), which should have an appropriate correspondence between itself and T_j. Among various TSEPs, the turn-OFF delay time (t_d_off) shows good performance of sensitivity and linearity for online T_j measurement. However, parameter offset may occur in TSEPs during the aging process of devices, which causes errors in temperature measurement. This paper proposes an online condition monitoring method to achieve junction temperature assessment for SiC MOSFETs over aging. The error caused by aging can be eliminated by updating t_d_off versus T_j relationship with the proposed aging compensation method. Moreover, an auxiliary circuit is proposed for accurate and fast detection of t_d_off. Experimental results have been given to verify that the proposed condition monitoring method can achieve accurate temperature detection under both healthy conditions and aging conditions of SiC MOSFETs.