Electrical-Thermal Coupling Modeling of SiC MOSFETs Based on Field-Circuit Coupling and Its Application in Junction Temperature Calculation during Surges

The chip temperature stands as a pivotal factor in assessing the surge reliability of silicon carbide metal-oxide-semiconductor-field-effect transistors (SiC MOSFETs). Under surge conditions, the temperature distribution across SiC MOSFET chips is not uniform. Consequently, in comparison to the conventional practice of relying on virtual junction temperature, understanding the distribution of chip temperatures assumes greater significance in evaluating the surge reliability of SiC MOSFETs. To obtain the temperature distribution of SiC MOSFET chips under surge conditions, this paper proposes a novel field-circuit coupling model for temperature calculation of SiC MOSFETs. Firstly, a temperature field calculation model for SiC MOSFETs devices is established based on the finite element method, and the proper orthogonal decomposition (POD) algorithm is utilized to reduce the dimensionality of the temperature calculation model. Subsequently, the reduced-order temperature field calculation model is transformed into a thermal network model. Secondly, a circuit model for SiC MOSFETs is constructed. By combining the circuit model of the SiC MOSFETs and the thermal network model, a field-circuit coupling calculation model is established. The validity of this field-circuit coupling calculation model is verified through three different test conditions. Finally, a surge test platform for SiC MOSFETs is set up, and the electrical and thermal characteristics of SiC MOSFETs under three different amplitudes of surge currents are calculated. The calculation results demonstrate that the field-circuit coupling model developed in this study provides voltage drop curves for SiC MOSFETs that are in good agreement with experimental values. Additionally, when the amplitude of the surge current is 120 A, the temperature difference between the center and corner areas of the chip is approximately 284.63°C. The method proposed in this paper extends the traditional field-circuit coupling method, providing a novel perspective for calculating the temperature of power devices under extreme conditions. To enhance understanding, this paper is accompanied by a video demonstrating the computational process of the proposed method.