Turn-off voltage sharing of field stop IGBTs in series connection

Insulated Gate Bipolar Transistors (IGBTs) have become increasingly important in modern high power systems. Due to limits in silicon properties and processing technologies, the blocking voltage of a single power device is usually limited compared to the typical grid systems operating voltage. To support a higher DC link voltage, power devices such as IGBTs can be connected in series. However, because of inevitable parameter variations and random systemic errors in the power semiconductor devices and the control system, a balanced voltage sharing between devices is often difficult to achieve. In this paper, the voltage sharing of Field Stop (FS) IGBTs connected in series during turn-off is analysed. Parameter variations are categorised and simplified for an easier understanding and for clarification, and are simulated in Silvaco ATLAS. Methods to improve the voltage sharing for FS IGBTs in series connection are discussed.