250W+ HW LED Driver need some advice

Discussion in 'The Projects Forum' started by nrannalli, Aug 2, 2010.

  1. nrannalli

    Thread Starter New Member

    Jul 30, 2010
    I have been building an 12"X18" LED array consisting of

    12 - 10W 10,000K 9-11 FV 1000ma (2 X 6 series strings)
    24 - 3W Blue 450-465nm 4FV 750ma (6 X 4 series strings)
    12 - 1w RED 2.2FV 350ma (6 X 2 series strings)
    12 - 1w Violet 405-415nm 3.8FV 350ma (6 X 2 series strings)

    I built a couple of different drivers so far testing for efficiency and this one seems to be the best I can come up with. I am using a 500W power supply SMC500PS24-CI which has about an 80% efficiency rating. I've only tested the 10 watt'rs with this driver because they draw the most power for this array. My power supply draw is around 153W measured on my killowatt meter and I am getting about 9,363 LUX at 16" from the 12"X18" array. The 10 watt'rs are currently at 10.5V 880ma and are looking good. I just think I can get a little more efficiency out of it but I want to keep cost down so I don't want to spend a ton of money just trying to save a couple of watts.

    So far I can build this for under 35$ with the current parts and a 2 layer PCB but if I can spend a little more to make it more efficient that would be great. I was thinking maybe a simple switcher or a buck regulator and I would rather not purchase a chip to do it if I can. If anyone give me advice that would be great.[​IMG]

    Also I currently have the power supply set at 25.4 volts to accommodate all the series strings of LED's.

    Thanks in advance.

  2. Wendy


    Mar 24, 2008
    That schematic looks familar, 317 data sheet?

    It is not how I would do it, but to each his own.

    My approach is to use an emitter follower something like this...


    Each stage is an independent current regulator, voltage regulation on the power supply does not matter with something like this. The transistors will need to be well heat sinked though, since they will take the brunt of the current.
  3. nrannalli

    Thread Starter New Member

    Jul 30, 2010
    No, it is a piece meal of a bunch of different style drivers and power supplies I've come across. The data sheet has some examples like this but with different parts and they could not handle the power I was looking for. I got the concept for the transistor and sense resistor from an article by Mark Scholten @ ONSemi. Also I forgot one requirement these have to dimmable which is controlled by an Arduino mega.

    I will give your example a try and see what kind of results I get. My main concern is power usage vs LUX if I can get 13-15,000 LUX (with all LEDs) using less power I am good.