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Voltage Regulator for TFT LEDs instead of CCFL.

Discussion in 'LEDs and Optoelectronics' started by CidiRome, Aug 9, 2012.

  1. CidiRome

    CidiRome

    2
    0
    Aug 9, 2012
    Hi.

    What I have:
    15V DC source
    Variable DC source from 1.80V to 3.33V

    What I need:
    A basic circuit based on Trasistors/mosFETs to drive the Dimmer of the Monitor LEDs with
    Variable DC Output from around 5V to 12V based on the variable DC source.

    I've replaced the CCFL lamps of a monitor with led stripes, it is working pretty good, but now I'm trying to use the dimmer signal to regulate the LED intensity.

    My electronic skills are not enough to accomplish this only by myself, I was able to dimm the screen using a mosFET or a trasistor and a potentiometer to drive them, but I'm not being able to successfully drive them with the dimmer source.

    Any ideas are appreciated.

    Best Regards.
     
  2. BobK

    BobK

    7,599
    1,641
    Jan 5, 2010
    You cannot effectively dim LEDs by varying the voltage because the current varies wildly over a very small voltage range. Dimming of LEDs is best done by PWM (Pulse Width Modulation), which turns the LED on and off rapidly. The dimming is achieved by controlling the percentage of time the LED is on.

    Bob
     
  3. CidiRome

    CidiRome

    2
    0
    Aug 9, 2012
    In the meantime, I changed the circuit configuration based on the same NPN transistor and managed to put it working.

    It is working very nice, I only need some adjustments for it to be perfect.
    The first working result is even more perfect than I would ever expect, the brightness amplitude is almost perfect.

    Best Regards.
     
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