Is There a Formula?

Discussion in 'General Electronics Chat' started by GreenasGrass, May 18, 2014.

  1. GreenasGrass

    Thread Starter New Member

    Aug 10, 2013
    13
    0
    Is there a formula that matches the proper driver to a existing COB LED, if so could someone please explain it in simple terms?

    What I asking is how do I identify the proper driver for the following LED?
    http://www.digikey.com/product-search/en?v=90&mpart=CXA3050-0000-000N00V427F
    I'm looking for maximum brightness with regards towards the longevity of the chip, rated at 50k hour lifetime.

    I know that some of you here snap these type of problems out in your head, I don't mind using a calculator but I don't the know formula.

    Thank you.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,281
    1,230
    It is not as simple with high power LEDs as it is with the little ones because the high power ones need a heat sink to run near full power. So sorry to say you need to pick a heat sink first. Heat sinks are generally spec'ed in their temperature rise in degrees C per watt. So if you look at page 17 of the LED data sheet it will tell you how much current you can run thru the LED at various temperatures depending on the size of the heat sink. So bottom line if you have a heat sink of 5C/watt you can run at about 650 ma. If it is 2C/watt about 1300ma.
     
  3. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
  4. GreenasGrass

    Thread Starter New Member

    Aug 10, 2013
    13
    0
    I'm thinking this sink with fan, one chip per sink, the fan is to be powered by a separate remote supply.
    http://www.rapidled.com/as-is-6-x-20-black-anodized-aluminum-heat-sink/
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,281
    1,230
    That will do it for sure.
    This one would get you about 75 watts. You can google around for an even larger one if you like, but for long life 1.75 amps might be enough.
    If you want to look for others the driver needs to be capable of at least 42 volts - usually they will spec a range like 35 to 42, and a current up to about 2 amps. The current is what is controlled on LED drivers.
    http://ecatalog.astrodyne.com/usa/led-power-supply/DR075-042S175
     
Loading...