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Flyback driver...need help

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xandros01

Tue Nov 20 2007, 04:45AM

Registered Member #1128 Joined: Mon Nov 19 2007, 09:50AM
Location:
Posts: 3

Hi guys!, iÂ´m a new member and i need help because i have look in a lot of pages for a flyback driver that be able to work with a flyback (one of the newest, not the oldies) and i found this driver from the tesla boys page.

http://www.teslaboys.com/Plasma/PlasmaPower/PlasmaGlobeDriver2.gif
http://www.teslaboys.com/Plasma/PlasmaPower/

The question that i have: wold you guys recommend that i use this driver? or should i change any of them? and can i use another transisitor otherwise the MJ15003?

I actually have a
-lead acid battery 12V 4A
-transistor 2N3055A rated for 100V
-DC flyback from a compaq computer monitor

Myke

Tue Nov 20 2007, 06:16AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

From what I heard the newer ones don't work so well with that driver. Also the driver is pretty inefficient. Maybe a 555 and a transistor/MOSFET driver would work better.

Firnagzen

Tue Nov 20 2007, 01:38PM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

Don't use a 2n3055 for that circuit...

At least use a 2n3773 for that circuit. This website here has tested some transistors.

Gavin

Tue Nov 20 2007, 03:48PM

Registered Member #478 Joined: Tue Jun 20 2006, 11:57PM
Location: Shrivenham, United Kingdom
Posts: 8

I have had a play with fly-back transformers, and they are quite difficult to drive. I think the key may be to ensure they have some load when powered-up, like a TV tube

I have tried using MOSFETs, but this did not work, they just blew after a short time. I was actually using the old kind of fly-back as well, but not using any feedback, but instead built a 555 based PWM circuit to drive the MOSFET gate.

- good luck though

Mates

Tue Nov 20 2007, 05:28PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

You can try my circuit. It works well and you can change the power by adding or removing motor caps (using a switch). The circuit has changed litle bit since my first posting - at the moment I am not using that crazy diode setting but 1600V bridge instead (but connected as two diodes). Also I am using an IGBT transistor (BUP314) and ucc3721 in series with the TL494 to drive it (but it is not necessary). I played with the maximum power and regular 17" fly-back diped in oil can stand 80uF cap at 22KHz (approx 150W) and the voltage is over 50KV. It needs some experimenting which contacts on the fly-back works the best and it also very depends on the polarity of the contacts. But it is question of few minutes to find out (usally there are two contacts on one side litle bit separted from the rest which are the right but as I said it is very important to try swith the polartity on these contacts to get the proper performance). Alway use lower freq for finding the best performance (5KHz) and then dipp the whole fly-back in the cooking-oil (this is realy important) and go to freq between 20-25KHz...

The old scheme

Picture of IGBT setting running

And here the same circuit but powering an autocoil

cheers

Dr. Dark Current

Tue Nov 20 2007, 07:20PM

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

If you want an easy&cheap&powerful flyback driver (by powerful I mean it has the potential to melt your flyback) try this driver.
The only tricky part is the high current capacitor but the "X2" types you can salvage from old power supplies work well.

Shaun

Wed Nov 21 2007, 03:27AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

I agree, the ZVS driver has a lot of potential and works very well with modern flybacks. I don't really know why people say new flybacks are bad; I've always just wound a new primary on the exposed core and had them work fine (plus I could never find and AC flyback).

The only disadvantage I can see of DC flybacks is there is very little room for winding a new primary; only enough for 20ga mag wire or so. With the ZVS, you need as thick a primary as possible...

Mates

Wed Nov 21 2007, 10:29AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Shaun wrote ...

The only disadvantage I can see of DC flybacks is there is very little room for winding a new primary; only enough for 20ga mag wire or so. With the ZVS, you need as thick a primary as possible...

I realy do not see a single reason why to wind a new primary. The Fly-back has primary already inside. Just use an ohm meter find the one with lowest resistance and use it...

Dr. Dark Current

Wed Nov 21 2007, 03:03PM

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

Mates wrote ...

I realy do not see a single reason why to wind a new primary. The Fly-back has primary already inside. Just use an ohm meter find the one with lowest resistance and use it...

The internal primary is way too thin for the ZVS, it has a lot of turns plus its not center-tapped. Not useful for ZVS at all.

Shaun

Wed Nov 21 2007, 05:45PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

That was exactly my reasoning. I mean, the internal primary will work fine with a higher feed voltage, or if you only want the high voltage out and not the high current to go with it. I had specifically set out to make a ZVS driver I could pump a few hundred watts through (which I did, its arcs still scare me).

I used to have an older DC flyback that could fit a 10 gauge insulated primary. Sadly, that one burned up.

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