Talk:Flyback transformer

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Contents 1 How pedantic do we want to be? 2 This article need improvement 3 Not to merge 4 wonder if Historical alternative should be mentioned 5 Question

[edit] How pedantic do we want to be?

Strictly, the flyback transformer converts the deflection power supply voltage, not the "mains" ( input AC) voltage, to high voltage. Is this worth distinguishing in the text, without turning this into an article on TV repair? --Wtshymanski 05:24, 20 Apr 2005 (UTC)

I thought it was desirable for all transformers to have high inductance windings (not just flybacks) in order to extend LF response and cut down the magnetising current. Am I wrong? Does the author intend to say good coupling or low leakage inductance? Light current 16:48, 31 August 2005 (UTC)

I am not sure if the difference is best described in terms of the inductance. A "normal" (non-flyback) transformer is designed with a large magnetizing inductance---larger than a typical flyback transformer, in fact--but that inductance can only store a very small amount of energy. If you try to "charge up" the magnetic circuit in an ungapped ferrite transformer then it will saturate with only a very small amount of energy stored. In normal operation, the secondary sucks energy out nearly as fast as the primary puts it in, so this is not a problem.

A flyback transformer is distinctive not for its inductance, but for its ability to store energy (on the order of P_out/f_switching). The gap decreases the inductance, but it increases the ability of the transformer to store energy.

[edit] This article need improvement

Wtshymanski & Light current have good points. The deflection power supply is typically on the order of 70vdc and it is not correct to claim line voltage (AC) as the input to the LOPT. Additionally the inductance of mains (50/60Hz) transformers must be made high in order to reduce the magnetising current to acceptable levels and also to prevent saturation (applies to audio as well). On leakage inductance, it would be highly undesirable to have high leakage inductance in a LOPT as leakage inductance represents stored energy that has to be adsorbed by snubber circuits. In the case of mains transformers, if the output is driving a capacitive load (eg the voltage multiplier in a microwave oven) a high leakage inductance would be desirable in order to zero the power factor. I am not an audio expert, but I would imagine that the leakage inductance of an audio transformer would be quite low to insure minimal parasitic inductance in the circuit. It should also be made clear that the LOPT and associated circuitry is operated as a switched mode power supply and outputs a square voltage waveform given that the circuit switches between positive, constant di/dt and negative, constant di/dt. Additionally the voltage multiplier is not distinct from the "rectifier" as a CW multiplier intrinsically has a DC output. The author of the claims that the LOPT is responsible for the wine of monitors - this cannot be correct as all monitors operate with horizontal scans in excess of 40kHz - well above the range of human hearing. A much more likely source of audible sound is the mains stepdown transformer which may operate within the range of human hearing.

Many units with CRT's use a degausing coil, which makes a loud HUM sound when they start up.cmacd 19:30, 16 February 2007 (UTC)

[edit] Not to merge

A user placed the floowing in the article, at has been remouved "A better description is on flyback converter. This whole article is merely about the application in the TV, the only place where it is synchronized with the flyback of an electron beam, even computer monitors do not do it this way." Since the Flyback system si specific to televson and related techniques, I don't think the comment is valid, but wanted to perserve it just so it is not acted on. cmacd 19:30, 16 February 2007 (UTC)

[edit] wonder if Historical alternative should be mentioned

Before the flyback (1940s) - Tv sets sometimes used an RF power supply for the High voltage, which could be lethal. The flyback system will be loaded so much that it does not normaly kill.cmacd 19:32, 16 February 2007 (UTC)

[edit] Question

"Flyback transformers are a frequent source of TV tube failure."

I can't imagine how this could occur. CRTs are pretty robust things, like most thermionic devices, and I cant imagine any real world LOPT failure putting damagingly high V or i onto the tube. Tabby (talk) 23:26, 25 November 2007 (UTC)