Hi,
Looking at waveforms of a drsstc we're doing with HGTG20N60A4 IGBTs. We're observing some very high on-state voltages that descend linearly as shown in the photo here (Vce-blue, Ic-yellow):
http://s13.postimg.org/7dippsw07/photo.jpg
The gate voltage is near perfect and switches between +16 and -16 volts with no ringing.
There's a scale of 10 involved in the oscilloscope reading, so with barely 40VDC the on-state voltage is as high as 8 volts.It's all the more strange as we're nearly soft-switching and the current is rather small at transitions. Vce actually gets lower when the current peaks through the igbt. Has anyone come across this before? Many thanks.
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