IGBT cross conduction phenomenon — Origin and simple protection gate driving technique

In this paper, a problem of isolated gate bipolar transistor (IGBT) cross-conduction caused by re-applied collector emitter voltage is discussed and a simple gate driver that eliminates this issue is proposed. Variation of the collector emitter voltage of the IGBT that is switched off causes the collector gate displacement current that pumps the gate emitter capacitance and elevates the gate emitter voltage. If the gate emitter voltage reaches the threshold voltage the cross-conduction happens. Then the collector current and turn on losses increase significantly. Some measures to prevent such a critical malfunctioning are discussed in this paper. The most effective solution is the use of negative gate emitter voltage. In design of low cost power converters, the bootstrap power supply is the most cost effective solution. However, a limiting factor for the application of the bootstrap topology in higher voltage power converters is the fact that bootstrap supply does not provide negative gate voltage. An improvement of bootstrap power supply, which provides negative gate voltage is analyzed and proposed in this paper. The solution is experimentally verified and results are discussed.