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.