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Robustness improvement of high-voltage IGBT by gate control

This paper considers the turn-off robustness (the maximal current being able to be turned off) of high power IGBTs under over current condition. The analysis of turn-off curves shows that the turn-off robustness of the investigated devices is not really limited by the rate of voltage rise on collector-emitter (dVCE / dt ). The main reason of the robustness limitation is found out to be the rate of the MOS channel turn-off and impact ionization rate. The control method of dynamic active clamping was developed to delay the MOS channel turn-off und thus to improve the turn-off robustness without elevating more turn-off energy compared to the standard turn-off. Turn-off robustness is always an important parameter for high-voltage IGBTs. Simulation studies show that a series of adverse processes such as dynamic avalanche, current localization and current filaments can be observed during high current turn-off. Together with the thermal effect such processes can lead to turn-off destruction. On the one hand the turn-off robustness can be improved by proper design of IGBT cells. On the other hand it is reasonable to enhance the robustness by the use of appropriate gate control method.

1.55 MB
06/06/2008