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Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
That looks a bit odd, the switching time appears to be a bit slow, particularly for the lower scope trace. I too am curious what the supply voltage is. Also what diodes are you using? They need to be quite fast.
I'll have to scope mine when I get home, I've looked at the outputs but I don't think I ever did look at the gates, it just worked perfectly the first time so I didn't look into it further.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
Oh you used UF4007? Those are fine. Hmm... beats me. Are you sure both resistors are the same value? A small bit of asymmetry is normal, but it should be pretty close.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
The "ZVS" circuit has another oscillating mode where one of the transistors conducts much more than the other, and that is almost certainly destructive. This mode is triggered by excessive load, and can be prevented by larger inductance on the series inductor. Try to increase the inductance, and put something as a suitable resistor or inductor in series with the Jacob´s ladder.
Thanks, Antonio. That seems promising. I'll try it as soon as I can (12 hours :( ). Do you have any link that describes the phenomenon, or does that just come from your experience?
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Getting hot after two minutes doesn't sound bad to me, just slap on a larger heatsink and fan if you want to run it longer. Have you measured the power consumed?
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
Uzzors wrote ...
Getting hot after two minutes doesn't sound bad to me, just slap on a larger heatsink and fan if you want to run it longer. Have you measured the power consumed?
My ZVS circuit with the same mosfets doesn't get hot even with no heatsink at all, unless I push the input much higher, 20-50V. There are times when a bigger heatsink or fan are a good solution, but here I think it would be wise to figure out why it's getting hotter than it should rather than compensating for a fault.
I should have asked about the inductor, what did you use? Are you sure it isn't saturating? It has to be physically quite large to handle the current.
Yes James, I was starting to think the very same thing. I tried to double the inductor (50 uH => 100 uH) but I'm afraid it's simply too small. I'll try to find a bigger one. I do appreciate all the help from the community!
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Very HOT Mosfet in ZVS
