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Registered Member #503
Joined: Sun Nov 19 2006, 06:37PM
Location:
Posts: 59
Hi ,
Is it ok to drive the gate of a IRF540 or IRFP250 directly with TL494 ? Or is it necessary to use a MOSFET driver ?I am running at about 40kHz and switching 12V.
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
what you mean with "driving it directly"? THe TL494 has open collector and open emitter outputs. You want to use a load resistor? Remember that depending on your output configuration you will have slow turn on or turn off times or excessive standby power dissipation in TL494. I suggest you to use a driver or to use a complementary totem-pole driven buy the TL494
Mosfets should only be driven by a totem pole. You can use both of the outputs of the tl494 to form a totem pole but you can only drive 1 mosfet, and I don't think it will be able to source or sink too much current, so you get slow turn on and off. The same happens if you use a resistor for pull up or down of the gate.
All this happens because the gate looks like a capacitor to the driver. Basically you need to charge and discharge a capacitor.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
After blowing too many ICs when mosfets failed, I've gone to using gate drive transformers. You can make an H-bridge out of some NPN and PNP transistors, use that to drive the transformer and the transformer to drive the mosfet(s). Once you get the hang of winding the transformers they are cheap and effective, and if you blow a mosfet it won't destroy every component in your circuit.
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TL494 and IRF540
