Power dissipation

Discussion in 'The Projects Forum' started by r_subbiah, Oct 18, 2008.

  1. r_subbiah

    Thread Starter New Member

    Jan 28, 2008
    5
    0
    Hi,

    Could some one help me..

    I am considering the various option to power the 8 white leds in series for the LCD back light.
    When I use 42 VDC the power dissipation would be 42 VDC – 32 VDC = 10 VDC x 20 mA = 200 mW right?

    Now suppose if I use Boost converter from 5 V in put to 32 V what would be the power disipation?
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    What does '32 VDC' represents?

    What is the rated voltage of each diode?
     
  3. raybo

    Member

    Oct 18, 2008
    22
    0
    WHY USE 42V for 8 leds IS THAT WHAT YOU HAVE? 8 leds are probably 2-3v forward drop @10-15ma so now 42-[8x[2.5]?]=20-42- 22v * .015a=330mw you need a resistor of 1.5k 1/2w. that is the most efficient way adding of 5 v PWM is lame. just tie all those LED in series.
     
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