Investigation of Transient Thermal Behavior in Thyristors Under Pulse Conditions.

Under pulsed discharge conditions, high-power thyristors face challenges such as an excessively high current rise rate (di/dt) and the issue of triggering front expansion, which are difficult to accurately simulate. Traditional modeling approaches often neglect the non-uniform distribution and expansion process of the internal current within the silicon wafer. In this study, we address these limitations by incorporating these critical factors into our analysis. Using a two-dimensional device-circuit co-simulation approach, we investigate the current, temperature, and thermal power distribution within the thyristor during the turn-on process under pulsed discharge conditions. Based on the simulation results, we derive the velocity equation governing the transverse expansion of the thyristor current. Furthermore, we establish a three-dimensional finite element model of the thyristor and develop a generalized extended model for complex gate structures. These models enable us to obtain the transient temperature distribution during the thyristor turn-on process under pulsed conditions. Finally, we conduct cycle surge life tests on various types of thyristors, providing valuable insights for the selection and optimization of thyristors designed for pulsed applications.