Actual design question.

"Homer J Simpson"

** Your heading is BOLLOCKS !

** With most CFLs there is no need to do anything. ** Depends on the CFL of course - d*****ad.

Ones I have here ( rated for 220 - 240 volt AC operation) light up at anywhere from 70 to 200 volts DC and reach full brightness at about 300.

The light up voltage depends greatly on the temperature with many CFLs while brightness is roughly proportional to the voltage - ie half rated voltage = half max light output in lux.

YOU will just have to try some out.

........ Phil

I suppose it depends on the CFL ballast design. I cut one open once. The

120 Vac line input drives a rectifier and a filtering cap. I'd guess that one could feed 170 Vdc in at this point.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Diplomacy is the art of saying "nice doggy" while looking for a rock.

"Homer J Simpson"

** Did you want 12 volt DC operation ??

Then bloody say so - you pathetic jerk

....... Phil

Please remember to take your psychosis medications before you post anything, Phil.

Bob

12v CFL Light Bulbs Price Ex VAT = £ 10.50

As compared to 99 cents for 120 VAC.

He's a sad case, no? And he can't read : "Can CFLs be reconfigured to run off a DC supply? Minimum voltage?"

So the other way is to dump the electronics and add a fluo inverter / driver I guess.

*Any* fluorexcent lamp can run off of DC; the problem is to first strike that arc, which takes high voltage. When the arc is present, then it is wise to use current limiting so as to not overheat the poor lamp; typical voltage drop is the first ionizationpotential of mercury ~32V.

ISTR some fairly compact designs to run the tube off a low voltage supply.

I recall reading something about premature blackening at one end of the "tube" and early failure if dc is used with fluoro's????

"Robbo"

** All modern CFLs use electronic ballasts - ie high frequency inverters - to drive the tube.

The AC supply is rectified and used as a source of DC voltage for that inverter !!!!!

Eg:

...... Phil

I just picked up eight 18-watt spiral-tube cfl's at Cole Hardware, 50 cents each, subsidized by PG&E. They're guaranteed for 12 years. I don't believe that. My experience with cfl's is that they blow up fairly often, especially if started/stopped a lot.

John

And they don't much like outside light fittings.

It seems to shorten their life considerably. I've heard the main filter cap (electro) dies.

I suppose you're glad you don't have to subsidize purchases for your customers that would guarantee they buy less of your prouduct...

No one would run them off DC - very inefficient. I guess I'm looking for a nice 12 VDC driver design.

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The one on my deck, usually cold, takes minutes to make useful light. I'm practically done barbequing by the time it helps. Back to incandescents!

John

Very slow warmup if cold.

John

"Homer J Simpson"

** God, this fool is thick.

The inverter you need is one that converts 12 volts DC to either 120 AC or

170 DC.

Run any 100 to 120 volt CFL you like then.

....... Phil

"John Larkin"

** Better read this web page.

Everything you ever wanted to know about CFLs but were afraid to ask !!

BTW

The EU is about to ban incandescent bulbs for domestic use.

........ Phil