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Flyback Driver inside a PC PSU box

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Dr. Dark Current

Wed Jan 31 2007, 12:06PM

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

Hi all, I want to make a flyback driver that will fit incl. the flyback in a PC PSU box. Now I'm wondering if it is a bad thing that the flyback will be inside a metal box, will the metal "steal" power from the flyback? (I don't know much about magnetics

)

J. Aaron Holmes

Wed Jan 31 2007, 12:35PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Transformers and CRTs (generally implies flybacks) are found in metal enclosures all the time. I wouldn't think it would be a problem; the vast majority of the flux you care about is going to be in the flyback's metal core. Now, if you were talking big air-core reactors, then you might have to start worrying about induction-heating your PC case.

Of course, putting anything HV in a metal box means there are a lot more places the HV *could* go besides where you intended

Regards,
Aaron, N7OE

TheMerovingian

Wed Jan 31 2007, 12:53PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

I have done this. Housed a royer flyback driver in a metal psu casing (separate ground of course)

RoyerFlyback

Some static is possible, if you don't ground the casing.

Dr. Dark Current

Wed Jan 31 2007, 01:29PM

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

J. Aaron Holmes wrote ...

Transformers and CRTs (generally implies flybacks) are found in metal enclosures all the time. I wouldn't think it would be a problem; the vast majority of the flux you care about is going to be in the flyback's metal core. Now, if you were talking big air-core reactors, then you might have to start worrying about induction-heating your PC case.

Of course, putting anything HV in a metal box means there are a lot more places the HV *could* go besides where you intended

Regards,
Aaron, N7OE

Insulation is not a big problem, output voltage is only about 15kv. I will remove the 230V output plug, cover the hole with some plastic, dig a hole in the centre of the plastic and thread the HV wire through it.
Yes, some flybacks in crt's are in metal enclosure, but there they do not work at too high powers, I guess around 50w for a standard flyback. My flyback is going to operate over 300w so I was wondering that if I screw it to the metal case (so the core will be really close to the case), the flyback could inductive heat the case and decrease performance.

Steve Ward

Wed Jan 31 2007, 05:25PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

My flyback is going to operate over 300w so I was wondering that if I screw it to the metal case (so the core will be really close to the case), the flyback could inductive heat the case and decrease performance.

The only possible location for induction to surrounding materials is at the gap in the core. But, the gap is usually so tiny, that the flux doesnt extend out from the core much at all. Otherwise, 99% of the magnetic flux is going to be contained within the ferrite, no worries about induction heating the case.

I dont suspect your flyback will last long at 300W, though.

Dr. Dark Current

Wed Jan 31 2007, 06:12PM

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

Steve Ward wrote ...

My flyback is going to operate over 300w so I was wondering that if I screw it to the metal case (so the core will be really close to the case), the flyback could inductive heat the case and decrease performance.

In my design the core does not use a gap, so I guess it is fine then ;)

I was very lucky to get such a "killer" flyback, it gets just little warm after operating a Jacob's ladder for few minutes at full power

(300w is only at max. arc lenght, so I guess the average power is more like 200w)

Of course when I get it finished, I'll post some scary arc pictures

Dr. Dark Current

Sun Feb 04 2007, 12:41PM

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

Oh well, my flyback is now ruined

. A nice yellow light is shining from the inside of the secondary. I had the driver nearly finished, built into the pc psu case, when the flyback arced inside the secondary. I have one (different) secondary left that I will try, but I think it will make nowhere as nice arcs as the one that just burned.

edit> the new secondary is not as bad as I expected, the arcs are a little shorter, but "idle" current was decreased as well as driver heating. I will post pics after the driver is finished.

Dr. Dark Current

Mon Feb 05 2007, 04:22PM

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

It is done

the flyback is really AMAZING find, puts out scary flaming arcs, almost like a small mot

,but it gets just little warm after minutes of abuse.
pics
the box of death

inside

mot-like arcs:

that arc is like 12cm long

...

Tue Feb 06 2007, 02:16AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Meh, you need to switch over to a mazzilli driver and my homewound flyback...

I just need to solve that little problem that the fets release their m4g1c 5m0k3 at 120v instead of at 200v (so I can run it off fullwave rectified mains)

It would fit in a computer psu case, but I would have to use oil arround the flyback/doubler since sparks can start at ~2" (tracking)

But making it small and self conatined like that is pretty sweet!

ragnar

Tue Feb 06 2007, 04:26AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

That's the way! =-D

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