A Voltage Balancing Scheme for Series IGBTs to Increase Their Expected Lifetime in Pulsed Load Applications

Clamp mode resistor capacitor diode (CMRCD) snubbers have a simple and easy implementing structure. They have been widely adopted in the pulsed power supplies to provide a safe operating condition for the series insulated gate bipolar transistors (IGBTs). The main problem of the CMRCD snubbers is their poor performance in the voltage balancing of the series IGBTs. They are essentially overvoltage protectors and clamp the voltage of the IGBTs in a probable potentially dangerous condition. This issue diminishes the expected lifetime of the series IGBTs, where a number of them face a higher level of the voltage than that of the others. The unbalanced voltage of the series IGBTs will result in a lower value of the expected lifetime of the series IGBTs. For improving the expected lifetime of the series IGBTs a CMRCD snubber with balanced voltage sharing for the series IGBTs is proposed. Adopting this proposal will lead to the balanced voltage sharing of the series IGBTs, even in the blocking voltage below the nominal designed value. Consequently, the highest value of the lifetime is estimated for the series IGBTs in the stack. The simulation and experimental results truly demonstrate the effectiveness of the proposed structure.