Analysis of Surge Voltage during Turn-Off Switching of IGBTs

Abstract

Surge voltage at IGBT turn-off switching was analyzed with dependence on cell design parameters. Although drift layer thinning is effective to improve trade-off characteristics between turn-off loss E_off and on-state voltage V_on, voltage surge is induced due to quick expanding depletion layer. Therefore, the surge voltage V_surge has also trade-off relationship with the V_on at the same E_off condition. The origin of voltage surge was analyzed using TCAD simulation, and total amount of remained hole in the drift layer during turn-off switching is a key factor for the V_surge. Narrow mesa structure and thick buffer layer are effective for improvement of trade-off characteristics between V_surge and V_on.