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Registered Member #139
Joined: Sat Feb 11 2006, 11:01AM
Location: Perth, Western Australia
Posts: 358
Now, I seem to be having a few issues understanding the workings of single IGBT's (40n60's) and my bricks. I seem to be able to turn them on ok, but turning them off appears to be a bit of an issue. I have tried mosfets as drivers, and a GDT, but it doesn't seem to turn it off correctly if at all. am I going to have to use, say 2 n-channels, one to switch it on, and another to switch it off? and one inverting and one noninverting driver chip per IGBT? Or is it something simple like diodes over the GDT input or output? I'm sure it's pretty simple, but I am a IGBT virgin and am just getting more confused as I go on. Any help would be really appreciated.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
They are voltage controlled much like a MOSFET so you need something to pull the voltage both up and down to turn it on and off.
In some simple cases a resistor can pull opposite of the mosfet to turn it off. The best would be a symmetric driver using two MOSFETs. One PNP and one NPN.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
You basically turn IGBT on by setting some voltage on the gate, charging gate capacitance and it stays on while you dont connect the gate again to emitter (sometimes even below 0V) and drain it, just like a mosfet. Obivously its clear to you.
Here you can see one solution of mosfet driving for bricks:
When GDT is used directly on IGBT 33V zeners or TVS are needed to block overvoltage that may blow your IGBT's gate, and few ohm gate resistors may be good idea to prevent ringing and overcurrent. GDT is driven by full/half bridge of gate drive IC's or some other way, do not use flyback circuit here as it may output wierd waveforms.
Depending on what project are you working I think there are people here who can help you far more than me.
Registered Member #139
Joined: Sat Feb 11 2006, 11:01AM
Location: Perth, Western Australia
Posts: 358
Cheers for the help guys. I've only ever run FET's which obviously switch off and on depending on whether you have power to the gates or not. I wasn't aware that you charged up the gates on an IGBT, and was trying to figure out the best way to "snap shut" the gates hard. I kinda had the right idea with the FET's as a driver system, but wanted a bit of clarification in regards to it. I'll grab the parts tomorrow and have a crack at it.
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IGBT's
