Indirect IGBT Over-Current Detection Technique Via Gate Voltage Monitoring and Analysis

This paper presents a new insulated gate bipolar transistor (IGBT) over-current detection method based on the analysis of the gate voltage waveform. The IGBT's gate voltage turn-ON transient pattern is analyzed for the detection of IGBT hard switching fault (HSF). The ON-state gate voltage is monitored to detect IGBT fault under load (FUL). The IGBT's turn-OFF Miller plateau voltage is extracted and measured to sense the IGBT collector current in case of an over-load condition. Compared to the commonly used IGBT short-circuit detection methods or collector current sensing methods, this method can provide indirect fast detection of IGBT short circuit and accurate measurement of overload within one switching period. The feasibility and effectiveness of the proposed approach are validated both by simulation and experimental results. Measurement results show that HSF and FUL can be detected within 0.6 and 0.5 mu s, respectively. By comparing the extracted plateau voltage (V-PL) with a preset reference voltage (V-OCx), the IGBT over-load can be detected with a maximum deviation of +/- 1.2 A when I-C ranges from 3 to 110 A.