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From: "R. Lewis"
Subject: Re: 12V Fluorescent lamp driver
Date: Wed, 30 Oct 2002 19:28:49 -0000
Organization: Nextra UK
NNTP-Posting-Date: Wed, 30 Oct 2002 19:28:22 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"N. Thornton" wrote in message
> email@example.com (Dave H) wrote in message
> > I'm planning to build a circuit to drive a Compact fluorescent lamp
> > from a 12v car battery for use in a garden shed. The circuit wants to
> > be as cheap/reliable as poss and preferably use off the shelf
> > components.
> > I was thinking along the lines of a simple oscillator (running at
> > roughly 50hz) driving something like a 2N3055 connected to the
> > secondary of a mains transformer.
> > Is there a better way?
> Sounds perfectly effective. Yes there are ways better in some
> respects, but what is wanted is simplicity, ease of building and low
> cost. Your solution fits the bill.
> I would be temted to use a higher frequency, maybe a few hundred Hz.
> And your invertor will have no regulation, and a 12v batt swings ovre
> a wide V range. So I would add tap switching to select the nearrest
> voltage - otherwise your V will be miles out at times.
If you use 'a few hundred Hz' what ballast can be used?
Discharge tubes, such as fluorescent tubes, have a negative resistance and
must be 'ballasted' in some way.
Typically from low voltage DC, fluo' tubes are powered by a Hartley or Royer
type inverter at frequencies in the tens of kHz.
The output of the inverter (transformer) , although it has a high(ish)
impedance, generally requires ballasting - which is normally achieved with a
Unless you are familiar with such things they can be tricky.
If you go down the mains frequency/volts route be aware that some, but not
all, mains ballasts ('chokes') are far from happy with square waves.
In the interest of efficiency you may want to power factor correct your
mains ballast set-up.
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