Dynamic Thermal Simulation of Power Devices Operating with PWM Signals

Abstract

Fast power devices thermal simulation method based on averaging power losses over each cycle of PWM switching frequency is presented in this paper. For implementing a long real time dynamic thermal simulation of power devices, device power losses during transient process and static characteristics are defined as a function of device conduction current and junction temperature, and are represented by a lookup table. By carrying out the circuit electrical simulation, the device conduction current can be obtained. By combining the device conduction currents, global device temperature (GDT) and the data from the lookup table, the average power loss over each cycle of PWM switching frequency is then calculated for carrying out the thermal simulation. With the proposed method, a relative large simulation time step can be employed and simulation speed can be increased dramatically. The method is suitable for a long real time thermal simulation for complex power electronics systems.