Gate threshold voltage measurement method for sic MOSFET with current-source gate driver

Gate threshold voltage is a classic thermo-sensitive electrical parameter (TSEP) for the junction temperature estimation and the gate oxide degradation, which is considered as a promising precursor for the online condition monitoring of power MOSFET. However, due to the fast switching transient, the gate threshold voltage of SiC MOSFET is much more difficult to measure than its Si counterpart. More specifically, the conventional measurement method mentioned in the datasheet obtains the gate threshold voltage during the turn-on transient, which requires the measurement to be completed within tens of nanoseconds. This paper presents a new approach to evaluate the gate threshold voltage with the assistance of a current-source gate driver. The advantage of the proposed measurement method is its lower requirement for the bandwidth of the measurement circuit, compared with the conventional method. The principle of the proposed method is demonstrated, followed by the simulation validation. A current-source gate driver is designed and constructed to assess the proposed method in experiment which shows that the measurement results can be used to evaluate the junction temperature effectively.