In article c5a6b018-cbd7-4b06-a418-cf1d3086a848
@a39g2000pre.googlegroups.com, says...
I have a more than one tft screen where the backlight shuts off after
~2 seconds. By turning the monitor off and on again I get the
backlight to work for another 2s.

CCFL backlight driver IC's are usually configured to allow an
initial surge of current to get things started, then current
limiting kicks in via a capacitor charging up. The symptom
you describe is usually caused by worn-out tubes that will no
longer stay lit at the current limit levels designed into the
circuit.