IGBT fault protection based on di/dt feedback control

Customer power modules built with the latest IGBT chips may be operated to their extreme conditions in terms of junction temperature, switching speed and voltage and current ratings. This is of particular advantageous in electric/hybrid vehicle applications where power density is a critical design factor. With IGBTs operated at extreme conditions the fault response time with a traditional IGBT fault protection approach, such as Vce sensing approach, may not be fast enough. This paper presents a circuit configuration to identify an IGBT fault current by means of measuring the induced voltage across the stray inductance between the IGBT Kelvin emitter and power emitter. Upon fault current detection a feedback control is introduced to dynamically control the di/dt of the fault current. Once the fault current is contained at a predetermined level, a slow turn off mechanism is deployed. The effectiveness of the proposed IGBT protection scheme was validated with customer power modules using Infineon 3(rd) generation IGBT chips rated at 600V 1000A for 100kW electric drive systems used in fuel cell powered electric vehicles.