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LAN_403

Erlend^SE

Sat Dec 13 2008, 09:01PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

For Dr. Kilovolt: I am not the one that asked how to start, but I am interested in seeing your SMPS IC driver, and I think others may too be interested.

Got some flybacks on orginal board driven by SMPS controller here, maybe I try to reverse enginer it more and post scematics sometime if anyone ask for it?

Cwiber92

Mon Dec 15 2008, 10:43PM

Registered Member #1858 Joined: Fri Dec 12 2008, 05:17AM
Location:
Posts: 9

Would this transformer work for a ZVS power supply? (it's 24VCT @ 12A) Do I only need to add a big filter cap (what value?) and a rectifier to make this into a ZVS power supply? What fuse should I use? Do I need to add any more primary coils? Any components that I would need to change?

Arcstarter

Tue Dec 16 2008, 01:33AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Cwiber92 wrote ...

Would this transformer work for a ZVS power supply? (it's 24VCT @ 12A) Do I only need to add a big filter cap (what value?) and a rectifier to make this into a ZVS power supply? What fuse should I use? Do I need to add any more primary coils? Any components that I would need to change?

Yea sure, that would work fine. The ZVS may try to pull more current, but i wouldn't think so. The fuse can be something like 5 amps, or as low as three. At full power it is 288 watts, which divide that by 120 is 2.4 amps. It would be a little more, so 3 amps is just about perfect. Yes, all you would need is a fullwave rectifier and smoothing cap. The smoothing cap can be something like 10000uf or even more if possible. As long as the arcs are nearly silent and there is no hum, it is good.

You ask would it need more primary turns. What are you asking about? The ZVS needs 5+5 turns, which in other words is 10 turns tapped in the very center.

If you can, get a transformer from a microwave, and saw or chisel the secondary(the thin windings with much more turns) windings off, without hurting the primary. Then just wind about the same amount of turns as the voltage you want, and add or subtract until you get it. The MOT depending on the voltage and wire can supply like 20 amps for hours with a fan or some form of adequate cooling. But mots to tend to pull quite a bit of no-load current. Also heat up quite a bit. If yours pulls too much or the primary gets too hot, wind about 10-20 turns of wire for the primary, going the same direction and wire about the same gauge.

Cwiber92

Tue Dec 16 2008, 02:19AM

Registered Member #1858 Joined: Fri Dec 12 2008, 05:17AM
Location:
Posts: 9

Thanks for the info! I will definately look around for some salvageable transformers. Yeah, I asked about adding more turns to the primary because this website about flybacks says, "Primary should be between 5 + 5 and 20 + 20 turns, with a center tap, all wound in the same direction. The amount of turns depends on supply voltage. 5+5 for 12V, and work up from there." I guess I'll just disregard that statement. Just quick would an inductor such as this suffice?

Thanks again

rp181

Tue Dec 16 2008, 02:24AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

Transformer output voltage is proportional to the winding ratio. If one where to use a 10 turn primary at 10v primary and got 10kV out, then if input voltage is doubled, the output voltage doubles. Buy doubling the primary turns, you make it so the output voltage is the same.

Arcstarter

Tue Dec 16 2008, 02:53AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

The inductor should be able to handle very high currents. Not VERY high, but depending on what you want to run it on, the current can be as much as 20 amps or more. Mine pulls 18.5 amps at about 30-40 volts(somewhere in there). 100uh is not hard to get with homemade inductors. Just get a good ferrite toroid made of the correct material, and wind perhaps something like 50-100 turns(?) with some wire that can handle the current.

So, even when pulling 18 amps for minutes, my inductor doesn't even heat at all. Well, it will become somewhat warm, but nothing to concern me. The wire is only maybe 16 gauge or something. It was a ferrite toroid from the junk box from ... AKA Peter Krogen. He wound it, so i don't know the inductance or wire gauge.

Oh, and don't forget to get a very good capacitor. My capacitor does not warm, but it is pulse rated, and 1600 volts and .68uf. It is a Cornell Dubilier 942C16P68K-F capacitor, and i am sure it will never fail, especially because it is self healing :).

Sulaiman

Tue Dec 16 2008, 01:55PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

For the transformer mentioned above, to power a zvs,
if you put 1uF or more (film capacitor) across the bridge rectifier output
- the circuit should work ok
- you'll save the cost of large electrolytic capacitors
- the output will have a very large 120Hz ripple/buzz.
- not great for a lab supply...nice mad-scientist sound

Dr. Dark Current

Tue Dec 16 2008, 04:20PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Sulaiman wrote ...

For the transformer mentioned above, to power a zvs,
if you put 1uF or more (film capacitor) across the bridge rectifier output
- the circuit should work ok
- you'll save the cost of large electrolytic capacitors
- the output will have a very large 120Hz ripple/buzz.
- not great for a lab supply...nice mad-scientist sound

...or don't use any capacitor at all, you can then even leave out the inductor as the transformer secondary winding will provide enough inductance. The only problem is that the xfmr might get hot with all that HF on it...

Cwiber92

Sat Dec 20 2008, 05:44AM

Registered Member #1858 Joined: Fri Dec 12 2008, 05:17AM
Location:
Posts: 9

Some quick questions:
Does it matter how high above 250V the .68uf cap is rated at? Should it be any specific kind? I'm trying to decide between this higher rated cap and this cheaper cap. Will 2 of these heatsinks dissipate enough heat? Here are the mosfets I'm looking at.

Thanks for your time

Arcstarter

Sat Dec 20 2008, 06:07AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Those mosfets seem to be good judging by the current/voltage rating, and the first CDE cap mentioned would work very well. I have the same kind but 1600 volts and it is wonderful. Does not heat up a bit. And the slight decrease in voltage will not hurt it, especially since the mosfets would die way sooner and short out any high voltage if there was a spike.

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