In article ,
"Dave Plowman (News)" writes:
In article ,
Richard Porter wrote:
Flourescent tubes generally flicker once or twice on startup if you use
a normal starter switch. You can get instant starting chokes which
don't use switches but they are less efficient.

Electronic ballasts don't flicker - well not in the same way as switch
start - and are at least as efficient.

The tubes themselves also operate more efficiently if driven with
an AC supply of around 5kHz or more (around 5-10% more efficient).
Electronic control gear tends to be in the 20-50kHz range, and
hence well above this 5kHz boundary.

Note that you can still get some 100Hz flicker from some electronic
control gear due to ripple on the internal DC supply rail.
However, with old traditional ballasts, it is the 50Hz flicker which
some people can see either from the tube ends (more so in peripheral
vision than direct on), or from the whole tube if it conducts better
in one direction than the other (common shortly before end-of-life
failure). This 50Hz flicker is not produced by electronic control
gear at all, and 100Hz flicker is not visible by humans unless you
have something creating a stroboscopic effect with it.

--
Andrew Gabriel