An Online Junction Temperature Monitoring Method for SiC MOSFETs Based on a Novel Gate Conduction Model

Junction temperature monitoring is the basis of high reliability for silicon carbide (SiC) devices since thermal stress is the dominating aging factor. Due to the high switching frequency, conventional thermal-sensitive electrical parameter (TSEP) methods have poor monitoring performance for SiC MOSFETs. The gate current I G has been found as an effective TSEP for SiC MOSFETs. However, the exact relationship between the I G and the junction temperature and its fundamental principle has not yet been fully revealed. Moreover, existing monitoring methods based on the I G are limited to specific devices and require a complex measuring system. In order to solve the problems above, this article puts forward a novel junction temperature monitoring method based on the I G. First, a gate model of SiC MOSFET is proposed. Second, based on this model, an I G-based junction temperature estimation technique is presented. Third, an online measuring method for the I G is proposed. Finally, online experiments validate the proposed method. This novel method has three advantages. First, it can be used in various types of power electronics devices. Second, it can provide decent precision in various working conditions. Third, the measurement circuit required by his method is simple, which adds no additional hardware.