PCB Coil Based Turn-On Delay Measurement For Junction Temperature Estimation of SiC MOSFETs

Monitoring junction temperature facilitates over-temperature protection as well as condition monitoring techniques for power semiconductor devices. The junction temperature is generally monitored either by utilizing temperature sensors placed inside power modules or estimated indirectly through temperature-sensitive electrical parameters (TSEPs). Turn-on delay time is one such parameter that possesses good sensitivity to device junction temperature. For reliable measurement of turn-on delay time, it is crucial to determine the instant at which the device starts conducting current after application of the turn-on gate voltage. Consequently, device current needs to be sensed with high bandwidth. In this letter, a PCB coil-based current sensor is presented for turn-on delay time measurement of a SiC MOSFET. Compared to the stray inductance-based current sensing technique, the PCB coil removes the dependence of the estimation scheme on the device packaging features. Analytical formulation of the delay time is presented, followed by experimental results to validate the measurement principle.