Not sure where you heard that. Maybe I misspoke. Using the IGBT as a load follower, power through a light bulb to the IGBT Collector, the Emitter to ground, when I strike the Gate with 12 VDC the light bulb turns on. AS SOON AS I REMOVE THE 12 VOLTS from the gate the light bulb goes out. Rinse and repeat. The IGBT is working. But my guess would have been that once turned on with a gate voltage the IGBT would have remained on until it was grounded. So I'm definitely beyond any experience or understanding of the device.OK, so now I am hearing that the IGBT does not switch off with some level of load.
I read that part, and also the part about it not working with the dimmer control, in that it would not shut off. At that point the whole thing is not clear as to voltages and currents.Not sure where you heard that. Maybe I misspoke. Using the IGBT as a load follower, power through a light bulb to the IGBT Collector, the Emitter to ground, when I strike the Gate with 12 VDC the light bulb turns on. AS SOON AS I REMOVE THE 12 VOLTS from the gate the light bulb goes out. Rinse and repeat. The IGBT is working. But my guess would have been that once turned on with a gate voltage the IGBT would have remained on until it was grounded. So I'm definitely beyond any experience or understanding of the device.
Wired backward. When wired correctly it works. Apparently there must be a fast recovery diode internally.it would not shut off.
I'm not. The way it's wired when the PWM goes to the ground/common part of a pulse, it's not only deleting the gate capacitance but also trying to ground the + voltage of the whole circuit. This is why I keep saying it isn't going to work satisfactorily.I'm surprised to see the gate voltage drop so slowly.
Did you see the latest version of the circuit? (Post #125) I'd be interested to see the scope display of the sinking dimmer output. Maybe a load resistor from the dimmer to + would help the PNP turn off better?I'm not. The way it's wired when the PWM goes to the ground/common part of a pulse, it's not only deleting the gate capacitance but also trying to ground the + voltage of the whole circuit. This is why I keep saying it isn't going to work satisfactorily.
Granted, they are.facts are facts
But yet when I try to tell you something, things that don't go along with the other people here that some admit they have never done this, you only listen to what they say. So I'll ask you what you asked me earlier, what did I do to you???If I learn something along the way then I learn something.
Pin 3 goes high and low. Pin 7 - the "Discharge" leg goes open or to low (ground).Why the connection between the 555 pin #3 and the pot? Not a normal thing, but then again none of this is normal.
Really? I thought with the high from pin 3 the gate of the IGBT would turn on and when pin 3 went low the IGBT would turn off. Hard and sharp transitions with very steep slopes to the on and off wave forms. Again I ask - NO ? ? ?The 555 only sources(though when it is in the output on mode they call it sink?) less than 200mV. Not only that it can't sink and source at the same time, so your IGBT still won't switch.
It's hard to listen to everyone. Like driving a car and one person is telling you to turn left at the light and someone else is telling you to turn right. Who do you listen to? Sometimes it's a crap shoot. Partly because I had a notion that my circuit would work. Given that assumption, the people telling me how to move forward with what I already had sounded to me like the right thing to do. Don't take offense because I followed what ended up being advice for a non-workable solution. To be honest, I have no idea who knows more and who knows less. People talk a good game and those are the ones that are listened to more often than not. And when someone (you) disagree with them (the others), you don't always win.when I try to tell you something, things that don't go along with the other people here that some admit they have never done this, you only listen to what they say. So I'll ask you what you asked me earlier, what did I do to you???
by Aaron Carman
by Robert Keim
by Jake Hertz
by Aaron Carman