CCFL inverters

On 19 Dec 2006 21:41:12 -0800, snipped-for-privacy@gmail.com wrote in Msg.

How did you measure the RMS current and voltage? What does the user's manual of the thing that you used to measure current and voltage have to say about frequencies and waveforms?

robert

You need to look at the bulb specifications, not (just) the inverter.

If run over-current, the bulb lifetime will be much shorter.

Most CCFL backlights operate at about 5-6mA, but there could well be some that operate much higher.

Did you look at the waveform with a scope? Most CCFL devices require a (fairly good) sinusoid, but your measurement may have distorted the waveform (and therefore changed the crest factor so you got an invalid measurement). [I know this was already mentioned :)]

Make sure it's already started before looking with even a HV probe - the startup voltages required for CCFL backlights can be as much as 3x the run voltage.

Cheers

PeteS

Hi,

The sine wave looks fine when measured by the voltage and current probe. I have carried out the measurement using a Tektronix and Agilent scope and both gave similar results. I believe the tube brightness was measured to be 25000 nits but I can verify it when I start work next year. The tubes used were straight and used in a 12 inch LCD panel. I have another inverter which is used to drive another 12 inch panel but when I increase the current by adjusting the PWM, the sine wave becomes jagged instead of curved. Could this be caused by the inductance from the transformer? Can someone direct me to link that describes about this sine wave issue?

Cheers Geoff

PeteS wrote: