Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Why is my homebrew controller blowing mosfets? [Solved]

electrowizard · 07-09-2010, 10:23 PM

Thanks for the reply Mark;

I've read enough about IGBTs to understand what you're talking about, however my controller is using MOSFETs (after three weeks of reading and deciding)

The TVS is a unidirectional 15.2V unit so it should be quite similar to a 15V zener. My max Vgs is 16V so I should be safe there.

I know a lot of people use the 10k pulldown resistors.
Maybe my driver connection came loose and my mosfet went into triode... I don't believe they are as sensitive to that as you say IGBTs are. I suppose I will include it also just to be safe.

Six mosfets down, four to go! Good thing I bought lots of spares :P

Unrelated question: mosfet gate resistors (not pulldown)- absolutely necessary? I have looked high and low; it seems they are chosen empirically rather than actually calculated. My circuit seems to want a very low gate resistance. Maybe I should have chosen a more powerful gate driver? I don't really understand the tradeoffs here.

07-09-2010, 10:23 PM	#13 (permalink)
electrowizard EcoModding Lurker Join Date: Jun 2010 Location: Fort Erie, Canada Posts: 19 Thanks: 1 Thanked 1 Time in 1 Post	Thanks for the reply Mark; I've read enough about IGBTs to understand what you're talking about, however my controller is using MOSFETs (after three weeks of reading and deciding) The TVS is a unidirectional 15.2V unit so it should be quite similar to a 15V zener. My max Vgs is 16V so I should be safe there. I know a lot of people use the 10k pulldown resistors. Maybe my driver connection came loose and my mosfet went into triode... I don't believe they are as sensitive to that as you say IGBTs are. I suppose I will include it also just to be safe. Six mosfets down, four to go! Good thing I bought lots of spares :P Unrelated question: mosfet gate resistors (not pulldown)- absolutely necessary? I have looked high and low; it seems they are chosen empirically rather than actually calculated. My circuit seems to want a very low gate resistance. Maybe I should have chosen a more powerful gate driver? I don't really understand the tradeoffs here.