On 30 Sep 2006 08:29:07 GMT,
[email protected] wrote:
Have you tried googling about it or using Wiki? My recollection is
that the compact fluorescents operate in the 20kHz area and operate at
a low power factor, but I did what you should have done, I think. I
went to wiki and google and quickly identified this page:
That probably provides as much detail as you may need.
But please try spending a little of _your_ time searching _and_
informing us first about the scope and limitations of what you found,
next time. You may have done some searches already, but you said
nothing about that.
I have been searching on google/wiki a lot but I didn't find anything
useful.[/QUOTE]
Well, I had no way of knowing any of that. It would help a lot to
know what you didn't find useful and where you had looked, already.
It's better to write more, than less -- up to a point. You respect
the time of others, that way.
I figured if I know the voltage on the tube I can approximate the
transformer ratio in the ballast.
You haven't mentioned whether or not the article I pointed out was any
use. It's quite possible it isn't.
I don't imagine a "voltage," here. There is a necessary cold starting
voltage and perhaps some other steps early on, but once ionized, isn't
it the case that current control is the important issue?
I need the transformer for an PoE project. But I also figured CFL ballasts can
be used for cheap dc/dc (48->12V) converters. Another source for cheap dc/dc
can be those mobile phone chargers. But I suspect they have too high ratio on
input/output (230->4V) voltage. And they are harder to get by in large amounts.
I remember from doing a flash lamp many years ago (30) that the
voltage supply is something like 300V or thereabouts. My guess is
that compact fluorescents with tube lengths somewhere in the
neighborhood of a similar length will need roughly similar voltages,
with starting voltages much higher (I had to use about 4kV to trigger
the lamp, memory serving, supplied by a trigger transformer driven off
of the 300V on its primary winding.) What's actually required to
start these lamps, I don't know.
If my memory serves on another score, to avoid depositing needed gas
atoms on the tube surfaces, it's important to use AC and, if possible,
fairly high frequency AC is better than low frequency (up to a point,
which seems to be about in the area of the 10-30kHz.) The better
frequency to keep the atoms from depositing is a matter for physicists
to discuss, but I think that frequency is a typical area.
So these do NOT seem appropriate for dc to dc converters. The parts
may be useful, such as the current limiting inductor, for example. But
the design topology seems all wrong to use in its entirety.
I don't know what a "PoE project" is, but I do know what a 48V to 12V
dc/dc converter is, generally anyway. Since you are into adaptations
of one kind or another, why not just design and build one and scavage
parts from where you can?
Jon
