Analysis of CIC NPT IGBT's turn-off operations for high switching current level

For a high switching current level during IGBT's turn-off process, the simultaneous presence of high current density and high voltage can lead to avalanche generation. A one-dimensional (1-D) analytical model describing the voltage reapplication phase is presented for snubberless turn-off operations with CIC NPT IGBT's. Without avalanche generation, voltage rate of rise dV/sub AK//dt at turn-off remains constant. Avalanche generation is investigated on the basis of experimental measurements in combination with numerical simulations. The avalanche mechanism generates electrons in the space charge region delaying the sweeping-out process and increasing the turn-off losses. The avalanche generation can be avoided when the gate drive is slowed even though turn-off losses increase.