Discussion in 'Electronic Basics' started by Anonymous, Apr 25, 2004.

1. ### AnonymousGuest

Hey all,

I have two Sharkoon CCFLs hooked up to the inverter that came with the
package. Instead of putting that in my computer I want to use it with an
external power adapter. It works great, only the adapter does develop quite
a bit of heat. After 20 minutes it's hot..

The adapter is rated 12V, 400mAmp, 4,8VA

The inverter's info is:

CCFL Voltage: 200~1000V (?!)
CCFL Current/Inverter Output: 5mA
Power: 2,85 / 0,3W
Input voltage of inverter: 12V (DC)

I thought those cold cathode things don't use a lot of juice, I never
learned to do the math..

Can anyone tell me if 400mAmp is too small? If it is, what do I need, a
thousand?

Thanks, Erik

2. ### CFoley1064Guest

Hi, Eric. From the way you describe your problem, it sounds like you're headed
in the right direction. A 12VDC adapter with a higher current rating will
probably do the job. 1000mA sounds good.

Good luck
Chris

3. ### SoerenGuest

Hi Eric,

200V @ 5mA (200 * 0.005) is 1VA
1000V @ 5mA is of course 5 times this - 5VA

The voltage will start high and then drop once the CCFL tube strikes,
but I cannot tell you how much it will drop.

The inverter is not 100% effective, perhaps it is only 70% to 80% (or
even lower). This means that you will have to divide the numbers with
the effiency rating.
It will then need an input power rating of eg.:
1VA/0.7 = 1.4 VA
to
5VA/0.7 = 7.1VA