Re: Origin of "Flyback"

John Mehrtens wrote:

> It's definitely a Raster-originated definition, though the "Line Output
> Transformer" makes more sense by definition.
>
> Samuel M. Goldwasser's PHENOMINAL sci.electronics.repair FAQ site
> (http://www.repairfaq.org and, more specifically,
> http://fribble.cie.rpi.edu/~repairfaq/REPAIR/F_flytest.html) has this to
> say:
>
> -----
>
> "In the U.S. (possibly all of North America), the transformer that generates
> the high voltage in a TV, monitor, or other CRT based equipment, is called
> the 'flyback' or 'flyback transformer'. Most everywhere else in the world,
> it is either LOPT (Line OutPut Transformer) or simply LOT.
>
> The term 'flyback' probably originated because the high voltage pulse that
> charges the CRT capacitance is generated by the collapse of the magnetic
> field in the core of the transformer during the short retrace period - when
> the electron beam in the CRT 'flies back' to the start of a new scan line.
> The flux in the core changes slowly during scan and is abruptly switched in
> polarity by the HOT turning off and damper diode turning on during this
> flyback or retrace period.
>

WRONG! The damper diode doesn't turn on until AFTER retrace.

>
> Many off-line switchmode power supplies and DC-DC converters are also of the
> 'flyback' type with energy transferred to their output circuits mainly
> during the same time in the cycle - but there is no CRT involved and their
> high frequency transformers are not generally called flyback transformers.
>

Once again wrong. A transformer used in a flyback power supply is indeed called
a flyback transformer. One of the main differences in a coil or transformer
used in a flyback regulator circuit is a larger core. This is because the core
has to be able to store the TOTAL output power of the circuit. A forward
switching power supply only has to store part of the power. And the core in a
non-flyback transformer really doesn't have to store any of the power.

>
> LOPT and LOT derive from the fact that it is the line scan circuit that is
> involved and the transformer is in the output stage.
>
> I still think flyback is much more quaint! :-).
>
> Of course, others have their own definition:
>
> (From: Sam Riner (riner@inet2000.com)).
>
> When I was about 12 I touched the wire coming from the FBT on the picture
> tube, this was a BIG floor model TV, and I flew about five feet backwards. I
> know this isn't the real history for the name but for many years I believed
> it was."
>
> -----
>
> This is a site I highly recommend to those who are beginners, all the way up
> to those who are experts. Simply amazing.
>
> I hope Samuel doesn't mind me posting this snippet!
>
> Cheers,
>
> John
>
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