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radhoo

Tue Jul 26 2011, 01:46PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

hi n0g,

the epoxy you're using seems ok, I didn't use anything extraordinary, just what I found on shelves.

I got some failures for tick disks, but not for the thin 3-4 mm ones, even when I pushed them hard , with no load on output.

What you could do is to decrease the disk size even further: go for 1mm tick disk. It will be more difficult to pour in the epoxy layers, but not impossible.

Newton, I now see what you've asked on PM. The flyback driver schematics can be found here:

nOg

Wed Jul 27 2011, 02:24PM

Registered Member #4011 Joined: Mon Jul 18 2011, 08:14AM
Location:
Posts: 12

Thanks radhoo.
I'm keep trying.

nOg

Thu Jul 28 2011, 12:35PM

Registered Member #4011 Joined: Mon Jul 18 2011, 08:14AM
Location:
Posts: 12

Finally, I did it. The disc flyback.
The core was saturated. My fet was warm even input voltage was very low, 5-6 volts.

Newton Brawn

Sun Jul 31 2011, 08:01PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

nOg:

The core and FETs at Mazzilli drive gets hot because the main transformer ferrite core works in the extreme of saturation. This is the way to make the commutation.

One way of reduce the core heating is increase the value of the 47-200uH choque. Preference for air core choque. The 47-200uH choke may be satutated too, difficultig the commutation.
A simple air core choque about 100uH could be done with 32 turns wire #14 on a 65mm cardboard "pipe". The winding has 4 layers, 8 turn per layer. After finished the winding, the coil will look like a donut 65 internal diameter, 85mm external diameter, 15 high... the wire may be pvc insulated for house wiring.

To eliminate the heating of the FETs and ferrite core, the gates can be driven by a small ferrite core transformer 1:1:1 that will make the coupling of main transformer to the gates. Your sketch shows a the main ferrite core of 16mm diameter(200mm2 cross section), you may use for the coupling transformer a ferrite core of 40mm2 cross section, rectangular or round. The coils are 15 turns each.
In this arrangement, the main core works bellow the saturation (< 0.3T) and the small ferrite core saturate a lower current, providind the required feedback to the gates.

Regards

nOg

Mon Aug 01 2011, 01:45PM

Registered Member #4011 Joined: Mon Jul 18 2011, 08:14AM
Location:
Posts: 12

"make the coupling of main transformer to the gates. Your sketch shows a the main ferrite core of 16mm diameter(200mm2 cross section), you may use for the coupling transformer a ferrite core of 40mm2 cross section, rectangular or round. The coils are 15 turns each. "
I didnot get it. Could you attached drawing, pls.

Thanks

Tony Matt

Tue Aug 02 2011, 03:32AM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107

Hi !

Here the ckt that I have used some years ago.
You can leave the ckt running hours and hours, no heating on trafo or FET with 50W continous load.

If you want run bigger loads make trafo T2 with bigger cross section and win the coils with ticker wire. Also T2 secondary may be 36 turns to get 80 volts output.

T1 stays in the same size.

Cheers

1312255810 3700 FT120471 Electronic Transformer 12v 50w

Newton Brawn

Tue Aug 02 2011, 04:41AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

nOq:

You wrote:

It sounds that push pull converter is not suitable to make good ferrite transformer. Is it better to drive with GDT?
My GDT driver is very simple. Tl494 with 1:1:1 GDT. I ran DC flybacks. It's sitll ok but flybacks was very hot and damage even I put in transformer oil.

I'm still not shore what circuit you are using, please make a sketch of the circuit, include data and details, size of the core(s) number of turns, voltage levels, etc. As soon I can get the sketch, I will clarify how to wire the coupling transformer to your circuit.

Regards

Newton

PS (PLS) - I could not found any info re: TI494. Can you give the parameters of the semiconductor ?

nOg

Tue Aug 02 2011, 01:25PM

Registered Member #4011 Joined: Mon Jul 18 2011, 08:14AM
Location:
Posts: 12

Thanks to Tony Matt, it's very cool. I'll try that.

Hi Newton Brawn,
I use ZVS. Now, fbt wasnot make any argly sound and FET now is OK.

NO...It is TL494, another circuit. Now I'm trying to drive with ZVS.
My core size is the last one that I attached.

Regards,
nOg

Tony Matt

Wed Aug 03 2011, 01:21PM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107

nOq:

You wrote:

NO...It is TL494, another circuit. Now I'm trying to drive with ZVS.
My core size is the last one that I attached.

As far I know TL494 is a Pulse-Width-Modulation (Pwm) Control Circuit, integrate of 16 pins....

If you provide precise information you MAY have the chance of a good and usefull answer.

Take your time, put all schematic in a piece of paper, add all details, list and specify the components, provide info re transformer(s) with the cross section area, number of turns in each coil, add sketch(s) of any significant detail(s), with dimensions. Revise 2,3.... times to make all info consistent. Then you shall read your paper as if you are onother reader to make shore that no doubts about the mater.... and post the info in the Forum. All readers will be happy.

Cheers

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