Research On Mechanism And Characteristics Of IGBT Short-circuit

High voltage IGBTs have been widely used in the field of power electronics technology.In practical operation,IGBT occurs various faulures.One of the most common faulures is the shorted load,which will cause serious damage to the device itself and even the entire system.With the continuous development of IGBT devices,the thickness of the chip is thinned,the heat capacity is reduced,and the short-circuit ruggedness decrease.Therefore,it is very important to study the short-circuit ruggedness of the high-voltage IGBT.Taking 3.3kV/50A IGBT as an example,this paper compares and analyzes two short circuit characteristics of IGBT,studies the short circuit failure mechanism and the dynamic avalanche and latch-up effect during short circuit,and analyze the influences of external circuit parameters,structure parameters and low temperature on short-circuit characteristics,dynamic avalanche and latch-up effects during shorct circuit.There are main contents:Firstly,the two short-circuit characteristics of IGBT are corImpared and analyzed.The influence of external circuit parameters and structural parameters on short-circuit characteristics is discussed.The mechanism of short-circuit induced dynamic avalanche and latch-up effect is theoretically analyzed.This paper establishes the 3.3kV/50A IGBT structure model by professional simulation software and analyzes the influence of external circuit parameters,device structural parameters and low temperature on the two short-circuit characteristics using the electrothermal coupling simulation.Finally,measures to increase the short circuit withstand time are proposed.Secondly,the electrothermal coupling simulation with 4-cell device model is used to simulate the current density,electric field strength,holes density,temperature distribution and impact ionization rate of the device during dynamic avalanche in IGBT SCII.The mechanism of induced dynamic avalanche during SCII is studied,and the effect of different structural parameters on dynamic avalanche during SCII are compared and analyzed.The results show that dynamic avalanche occurs in the process of voltage rise when short circuit occurs and when short circuit current is turned off.The dynamic avalanche is stronger during the short circuit turn off.Lastly,the electrothermal coupling simulation with single cell device model is used to simulate the mechanism of the latch-up effect during short circuit.The results show that the latch-up is induced by excessive peak current when short circuit occurs,and it is also induced by large leakage current flow caused by temperature rise after short circuit turned off.The correlation between short circuit,dynamic avalanche and latch-up effect is discussed.Finally,measures to improve the short circuit capability are proposed.