Re: electronic ballasts

LAM Shing (
Thu, 2 Jun 94 14:00:15 HKT

Hi Barry,

I bought a few electronic ballast to use to build my aquarium hood.
They are inexpensive in Hong Kong, ~USD 5. I've been using them for 2
months and so far they are still running smoothly. Basically they are
some kind of ac-ac converter. The mains input is first rectified and
smooth and then used to power up a high frequency (above 20 kHz)
oscillator. The oscillator is connected to the fluorescent tube via a
transformer which, owing to the high frequency, can be made much
smaller and lighter the the conventional balast. And also the
efficiency is higher as the efficacy of the fluorescent tube is higher
under high frequency. An added bonus is that the lamp will be free
from flickering.

The usual balast acts as a choke (inductor) to limit the current
through the fluorescent tube which shows negative resistance.

The electronic ballast I used have plastic casing and are much much
lighter than the conventional ballast and they have 6 leads. 2 for
mains input and 2 sets of 2 leads for the fluorescent tubes. You don't
need a starter for the electronic ballast too.


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