Anomaly detection for IGBTs using Mahalanobis distance

•Describes the Mahalanobis distance (MD) approach to detect anomalies in IGBTs.•The MD approach can detect anomalies before failure for all NPT and FS devices evaluated.•Shows the advantage of using the MD-based approach over a fixed threshold based approach.

In this study, a Mahalanobis distance (MD)-based anomaly detection approach has been evaluated for non-punch through (NPT) and trench field stop (FS) insulated gate bipolar transistors (IGBTs). The IGBTs were subjected to electrical–thermal stress under a resistive load until their failure. Monitored on-state collector–emitter voltage and collector–emitter currents were used as input parameters to calculate MD. The MD values obtained from the healthy data were transformed using a Box–Cox transform, and three standard deviation limits were obtained from the transformed data. The upper three standard deviation limits of the transformed MD healthy data were used as a threshold for anomaly detection. The anomaly detection times obtained by using the MD approach were compared to the detection times obtained by using a fixed percentage change threshold for the on-state collector–emitter voltage.