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Compact fluorescent - voltage

Discussion in 'Electronic Basics' started by [email protected], Sep 30, 2006.

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  1. Guest

    What voltage do all these compact fluorescent "lamps" use ..?
    And what waveform/frequency is required (used) ..?
  2. Ken

    Ken Guest

    On 30 Sep 2006 08:29:07 GMT,
    They are current dependent.
  3. Eeyore

    Eeyore Guest

    They run off standard 50/60Hz A.C. line voltage/current e.g. 120V or
    220-2440V. The internal electronics sorts out what's required.

    What did you *really* want to know ?

  4. Aly

    Aly Guest

    You can run them off a small 220v/12v mains transformer in reverse, wired in
    a flyback configuration. That means, a transistor, and letting the thing
    self oscillate through one of the windings. The frequency all depends on
    how the transformer is built and will vary from manufacturer to
    manufacturer. But you can run a small tube off of a 9v radio battery.

    The terminology is roughly right there and someone will offer a better
    explanation. All I know is that from tinkering that it works. These
    handheld flashlights will have a small specially built transfromer meeting
    the specifications of the the tube the manufacturer chose.


    There's a bit on this on the DIY hobby sites somewhere. Google it.
  5. Guest

    I want to know what is applied to the *tube*, because I want to possible use
    the ballast for other purposes. Like 48V dc -> 12V dc, after all they seem to
    have all the stuff for a dc/dc converter.
  6. Eeyore

    Eeyore Guest

    An LCD backlight is essentially the same thing AIUI. You'll find plenty of info
    on drivers for them. IR have some dedicated CFL drivers too.

  7. PeteS

    PeteS Guest

    CCFL backlights typically run at 400 - 700Vac (depends on the
    backlight) and the start voltage is usually about twice the run voltage
    give or take a handful.

    Normal run currents vary - a very common run current is 5mA.

    I have one I am using (although I won't be soon - going to white LED)
    that has a nominal run spec of 680Vac with a start voltage guaranteed
    at 1500Vac (typical 1250 Vac)


  8. On 30 Sep 2006 08:29:07 GMT,
    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.

  9. JeffM

    JeffM Guest

    His ridiculously long username, his sloth, and posting to s.e.d
    all may make him look like a n00b--but he ain't.

    ....and you're right: He should know better.
  10. default

    default Guest

    On 30 Sep 2006 11:04:28 GMT,
    I ain't no ex spurt but I took one of them suckers apart.

    The one I played with. Had no isolation! first off - you'd need a lot
    of experimenting to make a DC converter out of it. What they did was
    rectify the line in and then chop it (on and off real quick with
    discrete semiconductors) then routed the chopped DC through a
    capacitor to the tube. and had another circuit to work the heaters
    from the line (yes, it wasn't cold cathode)..

    That was my first (or second) thought when I had one burn out. How do
    I make a 12 PS out of this? Conclusion: ain't too likely.

    Now those little 5.7 volt isolated 800 madc converters they make for
    Nokia phones? The local store sells them for $5 and when I get the
    time . . . .
  11. Guest

    I have been searching on google/wiki a lot but I didn't find anything
    useful. I figured if I know the voltage on the tube I can approximate
    the transformer ratio in the ballast.
    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.
  12. Guest

    LCD drivers have some nice big transformers on their pcb. However they are
    harder than CFL ballasts to come by, and are more cumbersome to handle. As
    there usually is a whole laptop included ;)
  13. Eeyore

    Eeyore Guest

  14. I have been searching on google/wiki a lot but I didn't find anything

    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.
    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 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?

  15. scavenge. Sorry about the typo.

  16. Guest

    I have been searching on google/wiki a lot but I didn't find anything
    I tried for some time to find the answer so to say. But I figured I had
    reached something not well documented. And it was proberlbly a better idea to
    just ask then to search in absurdum.
    I tried to limit the requested data instead. A quick way to find out is with
    a scope across the cfl tube. But high voltages >1kV makes it risky.
    It's proberbly useful. I haven't yet read it in depth yet thoe.
    Yep, in many places it says have current limiting or else *P0FF*
    So far my guess is fire voltage ~800-1500V, and run voltage ~300-600V.
    The useful threshold seems to be 20kHz. But due audioable noise higher
    frequency is proberbly prefered.
    My thought was to reverse the transformer and put the rectifier + capacitor on
    the output. Guess that idea is toast thoe ;)
    There are designs for dc/dc but they still require an inductor.. thus looking
    into cfl ballasts.
    The PoE project is about power over ethernet. You send some sense signals and
    then apply 25-60V dc max 400mA over cat.5. But one need a 3:1 isolated
    transformer. I just want to make a quick bench test of the schematic before
    ordering the real stuff.

    While looking into this I figured a 48V dc distribution network would be useful
    for power distribution to computer equipment in the building useing thicker
    cables than cat.5. And cheap sources for 48V -> 12 or 5V dc conversion would
    be nice. So I thought maybe the cfl ballast could be modded into this.
    However it seems this was not the case ;)
  17. Nope. There was a model that used an incadescent lamp as a ballast for a 4
    foor fluorecent lamp. Ran off 230 VAC - no igniter IIRC.

    If they ran off about 50 or 60 VAC I wouldn't be surprised.
  18. Hmm. I just went over to that PDF file I'd mentioned and they seem to
    talk about 300V there. So perhaps I'm not far off base.
    Well, I'm almost dead certain that compact fluorescent (at least,
    those in the US) run at high frequency. The long ceiling tubes _do_
    run off of 50-60Hz, as you say. But not the compacts, as I understand

  19. Sure. Even the 4 footers can come with electronic ballasts now - less
    flicker and buzz. But there's no sign of an igniter system so they strike
    off 110 VAC.
  20. Wouldn't bet my life on it but it seems so. Still, it's hard to figure what
    is happening at that frequency.
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