An Online Gate Oxide Degradation Monitoring Method for SiC MOSFETs With Contactless PCB Rogowski Coil Approach

Real-time degradation monitoring (DM) of the gate oxide is an effective method to improve the reliability of SiC mosfet applications . Currently, the existing DM methods generally require direct electrical connection with the device, which undoubtedly reduces the reliability of monitored system. This article proposes a contactless DM method based on the turn- on transient current rate with fixed delay time ( di/dt - _Delay ), which is realized by a printed circuit board (PCB) Rogowski Coil. First, the effectiveness of di/dt - _Delay as a degradation precursor is verified by high temperature gate-bias test. The results show that the maximum di/dt of planar and trench gate devices decreases gradually with the gate oxide degradation and finally decreases by 51.2% and 33.6%, respectively. Secondly, the low-temperature sensitivity of di/dt is verified, and the conclusion that the di/dt under short delay time is independent of drain-source voltage ( V _DS ) and current ( I _DS ) is given. Then, a di/dt- _Delay extraction circuit based on PCB Rogowski Coil is designed, which has a measurement bandwidth of at least 38 MHz. The effectiveness of this real-time DM method is verified in a buck converter. The proposed method can provide a valuable tool for continuous health monitoring in emerging applications of SiC mosfet s to high-reliability applications.