Series IGBT Graceful Degradation Fault Detection Circuit

This paper discusses a circuit that uses Rejustors to measure the change in summed insulated-gate bipolar transistor (IGBT) gate-drive current in a series stack. By monitoring this current, graceful degradation and failure of the IGBT stack can be detected. The Rejustors allow the monitoring circuit to accommodate manufacturing variations in the transformers used in the gate-drive circuit, as well as other component tolerances.