An Automatic IGBT Collector Current Sensing Technique via the Gate Node

In this paper, a novel IGBT collector current sensing technique via the gate current and its physical implementation are presented. The proposed technique utilizes the Miller plateau phenomenon observed in power MOSFETs and IGBTs. A Miller plateau sensing circuit has been designed such that IG can be measured in the plateau region during the turn on and turn of phase of the IGBT. The value of the IG is digitized using an ADC and a distinct relationship with IC can be observed for the IGBT. The proposed current sensing method only monitors IG from the low voltage side of the gate drive circuit and allows a cycle-by-cycle measurement of IC with high accuracy. The maximum deviation is +-0.8A within the range of 0~25A for turn-on and 0~30A for turn-off. This technique is also suitable for integration into a gate driver IC.