A new method for junction temperature measurement of MOS-gated power semiconductor switches is presented. The measurement method involves detecting the peak voltage over the external gate resistor of an IGBT or MOSFET during turn-on. This voltage is directly proportional to the peak gate current and fluctuates with temperature due to the temperature-dependent resistance of the internal gate resistance. A measurement circuit can be integrated into a gate driver with no disruption to converter operation. The method is immune to dependence on load current, and allows autonomous and high frequency measurements through a measurement circuit directly controlled via the gate signal.