Power electronic device temperature estimation and control in pulsed power and converter applications

Reliable functioning of a power electronic switching device is limited not only by the instantaneous device junction temperature but also by its variation. A technique for reducing the device temperature variation is described. A simplified mathematical model of the thermal process in the device is evaluated in real time to estimate the instantaneous device temperature. A temperature control loop adjusts the device switching losses to compensate changes in conduction loss, thus keeping the total losses, and hence the temperature, substantially constant. This principle is applied to a pulsed power supply and to a PWM converter operating at a very-low-frequency (0.1 Hz) output power modulation. The amplitude of device temperature variations is reduced by at least 50%.