Thermal Stress Reduction of Power MOSFET with Dynamic Gate Voltage Control and Circulation Current Injection in Electric Drive Application

While operating an electric drive under different load conditions, power switch devices experience thermal stress which provokes wear-out failures and compromises lifetime. In this paper, a model-based dynamic gate voltage control strategy is proposed to reduce the thermal stress by shaping the profile of conduction losses. Thermal stability criterions are investigated, which limits the gate voltage operating range thus current focalization and associated local heat up are avoided. After that, simulations and lifetime estimation are conducted for performance evaluation in two different operation scenarios, which shows promising results at high speed operation conditions. Furthermore, a current injection method is applied for low-speed operating conditions to improve the compensation effort. This method is experimentally verified by using a custom proof-of-concept gate driver that supplies an adjustable three-level gate voltage. A three-phase electric drive is prototyped, on which power cycling tests are conducted. The junction temperature is measured and the results confirm the thermal control method.