Temperature estimation of MOSFET is crucial, for failure of semiconductors is closely related to the junction temperature. In order to improve the reliability of semiconductor devices, it is necessary to realize on-line temperature monitoring. However, it remains a challenge to measure the junction temperature fast and precisely, especially for high-switching-frequency devices, such as silicon carbide (SiC) MOSFET devices. To realize on-line junction temperature monitoring of SiC MOSFETs, this paper proposes a new method based on the on-state resistance. Firstly, on-state resistance is proven theoretically to be an available thermo-sensitive electrical parameter (TSEP). Then, a circuit with an auxiliary MOSFET is proposed to measure the on-state voltage drop online. It can provide accurate on-state voltage measurement, while working at higher frequencies with lower power consumption. Finally, the off-line and on-line experiment results demonstrate that the proposed method has a relatively satisfactory performance of monitoring the junction temperature of SiC MOSFETs online.

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