Closed Loop Junction Temperature Control of Power Transistors for Lifetime Extension

The lifetime of power transistors significantly depends on the junction temperature swings. These temperature swings occur, for instance when the load conditions of the power electronic circuit change. In this work, a closed loop junction temperature control system is designed to increase the expected lifetime of power transistors. Therefore, the control system reduces the occurring temperature swings by influencing the power losses of the power transistor. For that, the gate driver’s supply voltage is adjusted, which affects the switching speed and the conduction characteristics. The junction temperature is measured by determination of the temperature sensitive internal gate resistance via the high-frequency gate-signalinjection method and fed back to the junction temperature controller. Both, the junction temperature measurement method and the control system are evaluated with a three-phase two-level voltage-source inverter. It is extended by a control strategy, which calculates a suitable set value for the controller in order to reduce junction temperature swings.