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Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Daedronus wrote ...
nice but, 1. you need zenners across the gates, in case there is a voltage spike. 2. you should place a fast diode in parallel with the gate resistors for fast turn off. 3. you also need something like a 100k ohm across the gates to make sure the gates is off when the driver is unpowered, but there is power on the mosfet side. 4. you need a capacitor in series with the flyback primary to make sure you don't walk the core into saturation.
1. I have 15v back to back zeners on the gates to protect them in-case of more than 20v appearing there. 2. I have them too. 3. Fair point actually, never though about this. Luckily I have always shut off the flyback/half-bridge first before I turn the PWM part off. 4. Didn't know that, thanks. Will try it next time I have this circuit out (might be a while yet lol). Does it make that much of a difference in terms of arc length and current draw?
If the volt*second of each half cycle are not exactly the same the core will eventually "walk" into saturation.
As I said, the DC block capacitor is to make sure it doesn't happen. Sometimes you can get away away without it, sometimes you don't.
For average voltage control you definitely need it. In pulse by pulse current limit you definitely DON'T need it, and it will actually do bad things if you use it.
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
Well even though this thread is a bot off track, I got the audio modulation working, and it sound pretty good! on 15watts. I guess I could even use my guitar to produce a singing arc...But when using my computer, it can't produce enough power through the audio....
Just have to get a higher voltage FET, and then stop emf...
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555 flyback fails?
