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Identifying the pins of a flyback transformer

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LAN_403

lhl_henrylui

Thu Feb 26 2009, 10:56AM

Registered Member #1498 Joined: Thu May 22 2008, 07:08AM
Location: Hong Kong
Posts: 72

I've got a flyback recently.However,I don't know what the pins correspond to and I don't have the original circuit.Also,there is no any part number on it.
What I only know is that the flyback was come from a TV.
Attached are the images of the flyback.Could anyone help how to identify the pins??

Mads Barnkob

Thu Feb 26 2009, 11:19AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

The easiest method is to drive it with some flyback driver and hold the red lead near the pins, then you will find the opposit polarity for the high voltage output.

Thats what I have done with the ones I have used.

Proud Mary

Thu Feb 26 2009, 01:19PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

An even easier way is to consult the HR Diemen data sheet for that particular part!

If you'd like to give us any and all numbers just as they are printed on the case, I'll see what I can do for you.

Dr. Dark Current

Thu Feb 26 2009, 03:46PM

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

Connect the negative of a 24+ V DC supply to your eht lead, and use a multimeter to measure a voltage from the positive of your supply to all of the flyback pins. Which gives the highest voltage is the HV return pin.

For the primary, just wind it around the exposed core, you don't want to use the internal windings anyway for many reasons.

rp181

Thu Feb 26 2009, 04:16PM

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

Those are very hard to put thick enough windings for higher power. I suggest winding your own secondary. If you put the flyback in boiling water, the cores comes out with a little force.

Antonio

Thu Feb 26 2009, 05:45PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

I don't know why these recommendations to not use the primary winding, or worse, to not use the secondary winding (that is very difficult to make). To use the primary winding, just use a higher voltage power supply, as done in any CRT device. This allows operation with quite low primary currents and low dispersion of the magnetic field. it is not without reason that the transformers are built in this way.

Dr. Dark Current

Thu Feb 26 2009, 06:31PM

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

In a TV, the transformer functions as a voltage supply. But for our experiments, we usually want the current to be limited.

When using the built-in primary, the coupling between the windings is very high, this means that the output current gets extremely large when run at rated voltage output, destroying the transformer or the driver. The only way to stop this from happening is to lower the primary voltage, but this results in low output voltage, high output current and high heating of the transformer still.

With the primary winding located on the opposite of the secondary on the core, the coupling becomes quite low which usually allows operating the transformer at or over the rated votage output without destroying it (or the driver) when drawing arcs.

This is mainly true for bridge or push-pul drivers, with flyback drive topology the difference is not so extreme but still the external primary is better.

Another important advantage is that if you burn your primary out, you can just wind a new one. You can't do that with the internal one, and it's quite easy to burn it out, not saying that it's dissipation also contributes to heating of the sec. winding.

I didn't say anything about the secodary, the original diode-split winding can generate MUCH higher voltages (but not output powers) than any home-made winding on the same core.

MRacerxdl

Thu Feb 26 2009, 06:51PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

Lol, that flyback is exact the same flyback that I had use on ZVS Flyback SGTC o.O

lhl_henrylui

Fri Feb 27 2009, 08:58AM

Registered Member #1498 Joined: Thu May 22 2008, 07:08AM
Location: Hong Kong
Posts: 72

Dr. Kilovolt wrote ...

Connect the negative of a 24+ V DC supply to your eht lead, and use a multimeter to measure a voltage from the positive of your supply to all of the flyback pins. Which gives the highest voltage is the HV return pin.

For the primary, just wind it around the exposed core, you don't want to use the internal windings anyway for many reasons.

I think I've found the HV return pin by Dr. Kilovolt's method.Nonetheless,I don't know how to wind the primary,I mean I don't know the rules.

Dr. Dark Current

Fri Feb 27 2009, 10:48AM

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

lhl_henrylui wrote ...

I think I've found the HV return pin by Dr. Kilovolt's method.Nonetheless,I don't know how to wind the primary,I mean I don't know the rules.

This depends on your driver and voltage.
For example, ~10 turns with 24V and single-switch driver, ~5V/turn with bridge driver.

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