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IGBT full bridge issues

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moffy:
I agree with T3sl4co1l. The only point I would make is that the driver chips need to be right next to the IGBT's. Also the drive waveform shows quite a slow RC component. Maybe dropping the value of the 33 Ohm gate resistor, and checking that the drivers have enough current output to drive the IGBTs quickly. What does the power supply waveform to the drivers look like?

moffy:
Just one last point, with the gate resistors so far from the IGBTs, would they be prone to parasitic VHF oscillations like MOSFETs are? I know this can be destructive of the MOSFETs.

T3sl4co1l:
Probably not; the resistance of the cable, and the 33 ohms terminating it (not exactly matched, but a far sight better than a completely open stub), should suppress that mode alright.

I've not seen IGBTs oscillate quite that fast, though I also haven't gone out of my way to try.  I would guess it's safe to assume the MOS contribution to current flow can change as quickly as in any other MOSFET of similar generation, so the potential is the same.

Tim

moffy:
I looked a little online and they appear to have both a low frequency and higher frequency mode of oscillation, perhaps a contribution from the Bipolar and MOSFET components. It didn't appear as bad though as with just MOSFETs.

TmaxElectronics:
Thanks for the help guys, I will redo the design once I am done with my exams :D

I also realised I kind of forgot about dead time  :palm:  :palm:  :palm:
In the small coil that the primary driver design came from I kept reducing the dead time further and further to increase the maximum drive frequency. At some point I switched to an isolator which had no dead time at all, which was kind of ok for the small-ish currents I guess, but obviously the larger IGBTs didn't like it and just shot through.
I do feel kind of stupid for forgetting about that

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