Electro-thermal modeling of multi-megawatt power electronic applications using PSPICE/sup TM/

For circuits using SCRs and diodes, both the on-state forward voltage drop and transient thermal impedance are complex characteristics, for which adequate mathematical models been developed. The on-state forward voltage drop can be modeled by both the classical ABCD and the new MNOPQ...parameters. The transient thermal impedance can be well represented via four or five exponential terms representing the significant transient thermal time constants of the device. There is, however, one complication which is not represented in the ABCD and MNOPQ...models. This is the dependence of the on-state voltage on the instantaneous junction temperature. This effect, termed COD or VFIT, requires that the model be electro-thermal, meaning that this important dependence must be accounted for in a microsecond by microsecond manner during the simulation. This paper describes the basic device modeling equations and the techniques required to use these models in "analog" simulation programs such as PSPICE/sup TM/. Parameter extraction from empirical test data is described and the electro-thermal model accuracy evaluated. The final and new result is an electro-thermal model for power electronic application using SCRs and diodes which includes the dynamic effect of instantaneous junction temperature on the on-state voltage. The resulting PSPICE/sup TM/ electro-thermal model is expected to be an important design tool in multi-megawatt power electronic applications, providing the detailed analysis the power electronic engineer needs to quickly evaluate an existing or proposed power electronic application.