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lcd beat-noise (kind of flickering?)

Emanuele Montanari
Prodigy 10 points

Hi,

does anyone know something about 'beat-noise' on CCFL backlighted LCD displays?

Almost every datasheet says not to choose horizontal frequency (FH, and harmonics) equal to CCFL inverter frequency (FO).

Do you exactly know why?

Some ideas:

- is it that lamp current disturbs voltages applied to pixels?

- is it that if light 1/FO cycle profile is locked to line update frequency some columns are not illuminated and appear dark?

Thank you,

 

Emanuele

  • 0
    TI__Mastermind 36110 points

    I think the answer is that you don't want any fluxuations in lamp intensity to line up with the refresh rate.  If this happened, you would have a darker spot on the screen.  If they are close but not exact, you would see a darker spot moving across the screen.