flyback

[jin29_neci]

:lol:
hi guys I just to know what is the difference between a flyback and a ordinary transformer's.

thanks guys in adavance

 

[Sawblade]

I always heard it was because they make you "Fly Back" farther when you touch one. Sorry, I couldn't help it. :lol:

 

[Nigel Goodwin]

:lol:
hi guys I just to know what is the difference between a flyback and a ordinary transformer's.

A flyback transformer is used for a very specific purpose, the line output stage of a TV or monitor.

Unlike a conventional transformer it's tuned, and you only supply it a square pulse (not constant AC). Because it's tuned, as the pulse switches OFF, the back EMF generated 'rings' the tuned circuit, producing a high voltage pulse on the primary (usually approaching ten times the supply voltage). This is passed through the transformer in the usual way, producing very high voltages on the secondary - they commonly also have low voltage windings, that supply power to some sections of the TV.

 

[Sawblade]

Cool, so the high voltage is generated by the collapsing magnetic field like when you trick your friends into touching an inductor to a 9v battery with their bare fingers.

 

[eblc1388]

Eblc's understanding of conventional and flyback transformer are:

1. For conventional transformer, energy/power is transfer from primary to secondary via changing magnetic flux linking both primary and secondary windings, with little or no time delay in between.

2. For flyback transformer, this is a two-step process. First magnetic energy is stored(surprisingly almost totally in the air gap) then flyback action occurs and this energy is released to the secondary by collapsing of the magnetic flux in the air gap. So in effect a Store-->Release-->Store-->Release....process and so on.

Unlike a conventional transformer it's tuned, and you only supply it a square pulse (not constant AC).

A flyback by itself, like any high Q inductor, will ring when supplied with a square wave. In fact this is the method used for testing whether there is any shorted turns on the flyback. I have built a tester for such purposes when I was troubleshooting my monitor HV circuit. (see image)

In actual TV circuit, the "excitation" voltage is not a square wave, so the flyback does not ring.

 

[Nigel Goodwin]

In actual TV circuit, the "excitation" voltage is not a square wave, so the flyback does not ring.

The drive waveform to the base IS a squarewave, the pulse you showed on your scope is the ringing waveform produced by the squarewave pulse. The efficiency diode clamps the following negative excursion of the pulse, in a similar way that a diode across a relay coil works - so you only get the first 'ring'.

BTW, nice LOPT tester, is it based on Bob Parkers design?.

 

[eblc1388]

BTW, nice LOPT tester, is it based on Bob Parkers design?.

Yes and I added a good inductor inside the case via a test switch which I can selectively apply a one turn short-circuit to it. All my LEDs light up when I press the test switch in one way and none in other.

Nigel have you got one and do you find it useful?

For users wanting more information, here is the link:

**broken link removed**

 

[Nigel Goodwin]

BTW, nice LOPT tester, is it based on Bob Parkers design?.

Yes and I added a good inductor inside the case via a test switch which I can selectively apply a one turn short-circuit to it. All my LEDs light up when I press the test switch in one way and none in other.

Nigel have you got one and do you find it useful?

For users wanting more information, here is the link:

**broken link removed**

 

[Nigel Goodwin]

BTW, nice LOPT tester, is it based on Bob Parkers design?.

Yes and I added a good inductor inside the case via a test switch which I can selectively apply a one turn short-circuit to it. All my LEDs light up when I press the test switch in one way and none in other.

Nigel have you got one and do you find it useful?

Yes, I've got the kit from Dick Smith in Australia, it's very well made and reasonably priced. It's 'reasonably' useful, but I find a lot of duff transformers that it doesn't test as duff! - bear in mind it only tests one specific function, that of a ringing coil. It tests all sorts of coils, so it comes in useful in suprising ways!.

For users wanting more information, here is the link:

**broken link removed**