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Thread: Anyone know how to dim an TFT LCD backlight?

  1. #1
    Constant Bitrate
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    Nov 2001
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    Post Anyone know how to dim an TFT LCD backlight?

    Just wondering if a resistor network or something might work. I dont want to have to put tinted perspex over the screen to dull it at night.

    [ 02-01-2002: Message edited by: Genesis ]

  2. #2
    FLAC LESLIEx317537's Avatar
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    Arrow

    Search around, basically what you do is put a potentiomenter before the inverter.

    So the less power you give the inverter, the less bright it gets.
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  3. #3
    Constant Bitrate lifeboat's Avatar
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    Post

    It is more complicated than that, not all inverters can use a simple pot, some require a PWM voltage signal to run the dimming function, some (i.e. Taiyo Yuden LS520) require a voltage divider circuit to provide bias voltage to the dimmer circuit on the inverter. In the case of the LS520 there is an internal circuit that compensates for resistive load and would defeat a potentiometer. I was at the electronics store buying parts for this voltage divider circuit just an hour ago. Basically it depends on the brand and model of the inverter as to what method will work.

    CCFL Overview: http://power.tdk.com/pdf/dcac/applic...on_Note_97.PDF

    Example of TDK inverter w/ dimming circuit: http://power.tdk.com/pdf/dcac/brochu...612_Series.PDF

    Example of ERG inverter PWM dimming: http://www.ergpower.com/pdf30/8m121665.pdf

    Example of dual backlight LS520 w/ voltage divider dimmer: http://www.t-yuden.com/pdfs/ccflinve...ccfl-ls520.pdf

    Disclaimer: I am not an EE and am still learning this stuff, I still let the smoke out of things from time to time.
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