I am analyzing changes in IGBT Vce voltage to determine changes in the junction temperature.
My circuit consists of 6 IGBT's in series where I only switch the first transistor. The other 5 are always in conducting state. Initially I run 450 amps trough the circuit and then switch off the first IGBT. I have another current source for the 5 IGBT's running 1 amp through them constantly.
After I turn off the 450 amps I see a nice Vce curve that can be transformed into junction temperature easily (t1). However there is a dip in Vce around 1ms after the switch off (t2). The voltage stabilizes after ~7ms (t3). Curve in attachment.
What is happening? Could this be due to tail current of the first IGBT?
How could I reduce this?
Hi Aku Forsström ,
could you please provide the schematics as well? I have only a vague idea about how you manage to have less VCE in the off state.
Secondly, do you have access to a current probe which can be attached to a scope? A bandwidth of, say, 100 kHz would be more than enough in this case. It might be enlightening to compare IC with VCE.
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