LM338K or Mean Well LDD-H for flicker free 3W LED driver?

Discussion in 'General Electronics Chat' started by smilem, Aug 5, 2014.

  1. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Hello, I know for a fact that LM338 as constant current source is flicker free as LED driver, but it heats up and is not power efficient. Size is another problem.

    The Mean Well LDD-H is a box about 2 x 3 cm in size
    http://www.meanwell.com/search/LDD-H/LDD-H-spec.pdf

    The dimming is done by separate power source of >2.5 ~ 6VDC if I read data sheet correctly. But does it flicker?
    So far the controllers I got from ebay do flicker (no you can't see it by eye) but a camera can see it.
    As my project needs flicker free camera light source I would like to ask for help.
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    I would start by identifying the root cause of the problem. DC-DC converters are notorious for being unable to handle load transients. What is a load transient you ask? Glad you asked. If the current demand of the load changes suddenly, the voltage will drop, and the the DC-DC converter must adjust the duty cycle to adjust the average current output. This causes the output light to "flicker", or change in intensity.

    Step one would be to establish why you have load transients at all. Step two would be to find a DC-DC converter with better transient response. Step 3 would be to design your own, if a suitable unit cannot be purchased. Last time I looked this kind of design expertise did not come cheap.
     
  3. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Thank you for quick response, as the load is LED the load is stable it does not change. I think I'm having bad luck with made in china led drivers.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,173
    397
    If the LED driver output is unfiltered PWM, then adding a filter might help.
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    Something is causing the poor regulation. You need to investigate more thoroughly to locate the root cause.
     
Loading...