Connect with us

Need advice for 100 watt led power supply

Discussion in 'Power Electronics' started by j.walter.miller, Dec 7, 2012.

Scroll to continue with content
  1. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    I've been reading about how to determine what type (constant current vs constant voltage) of led power supply a given led will require to operate safely.

    I've found a lot of information about driving small LEDs in series and parallel, using resistors, etc.

    The more I read the more I'm convinced I need some help.

    I've got two different 100 watt leds:

    #1: 100 watt, 20 - 22v maximum forward voltage, 3500mA maximum forward current

    #2: 100 watt, 34v maximum forward voltage, 3500mA maximum forward current

    I'd like to get some advice on buying a couple of MeanWell power supplies.

    There are several types offered:

    Type A: Operates in constant voltage or constant current mode. A-type also has potentiometer for output voltage and output current adjustment.

    Type B: Dimmer version.

    My goal is to operate these LEDs at about 80% of their maximum threshold. My plan is to buy two power supplies, one for each led.

    Can you help me pick out a power supply for each of these leds? I'm learning but want to make sure the choices I make won't burn up the leds.

    Type A: http://www.trcelectronics.com/Meanwell/power-supply-hlg-h.shtml#100w

    Type B: http://www.trcelectronics.com/Meanwell/power-supply-hlg-b.shtml#100w

    I'd like to be able to dim these leds using a potentiometer.
     
  2. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    After doing some more reading, I believe I need a constant current driver. There is no resister build into these LEDs. It's just the module itself.

    At least that is the best guess I can make right now given my understanding.

    [​IMG]
     
  3. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    Have a read up on Flyback Converters. This type of converter is fairly simple to impliment, gives isolation and if fairly easy to control. Constant voltage can be achieved by using a voltage divider directly to your control circuit (through an opto isolator to keep the isolation)and constant current can be achieved using a current sense resistor to measure the current and relay information back to your control circuit (again through an opto).

    I would suggest using PWM to dim the LED's as they are not vary linear and it is easier to achieve a linear dimming using PWM.

    If you do not require isolation between the primary and secondary then it may be simpler to impliment a simple unisolated driver. However with a flyback you will not require more than one power supply as various auxillary and secondary windings can be used to provide all maner of power levels at the output.

    Have a read and if you think it will work for your solution come back here with any questions :)

    Otherwise you will need to chose one of two fo the suppluies you have provided above. They should be capable of diming using standard 1-10V and PWM as most LED solutions offer this these days. However if you are simply trying to drive your LED's without blowing them up it may be a lot cheaper to develop a solution yourself.

    either way, the world is your oyster!
     
    Last edited: Dec 7, 2012
  4. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    Thanks for the information, Rob. I guess I should have been clear that I want to buy as opposed to build. These leds will run in my home for a long period of time so I think buying a solution to power them is safer given my relative ignorance.
     
  5. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    Ah OK well pick a driver with the same power output as you require.

    The site you linked to mentions that there are 0-10V dimming options avaliable. This can be achieved as you mentioned with a potentionmeter. With the wiper connected to the dimmind input of the drive and 0-10 volts accross the pot.

    You will likely need some heat sinking on the LED's. How far you are willing to go with thermal management will decide on how elegant the solution is. For isntance the most elegant would be a purpuse built heatsink that fits within the constraints of your LED housing. An un-elegant solution could be a chunk of aluminum thermally attached to the LED.

    I imagine your design to fit somewhere in between this as purpose built thermal solutions can be very expensive. However the LED manufacture may offer solutions for those LED's so it may be worth checking them out.

    Other than thay you should be good to go.
     
  6. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    That's the magic of my solution. I am using water blocks normally employed to cool computer CPUs. Works great.
     
  7. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    Even better!

    Rob
     
  8. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    That's the thing. I know that they can handle a maximum of 3500mA. I am thinking I would want to control that current output, right?

    The only other thing I need to watch out for is to make sure the power supply puts out enough voltage, right? Am I worried about too much voltage?
     
  9. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    The drivers will have control actions that sort all this out for you. They are generally quite wide input ranges (from 90-265VAC) and will ensure that the output always stays at the right level.

    You must choose a driver that matches the driving characteristics of your LED's. Some drivers will even have controlable parameters that let you chose from a range of output powers.

    With LED's voltage can vary a little (and i mean a little) but current must be strictly controlled. This is because unline most devices LED's will draw more current that they need until they fry. This is kind of like a zero resistance effect where the current will just rise indefinatly until the device is destroyed.
     
  10. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    This makes sense and is getting to the root of my concern. I would assume if I want to drive these leds at some threshold below their maximum rated forward current I should choose a driver that outputs currently below 3500mA? Is that the right way to interpret maximum forward current?
     
  11. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    Yes exactly. The current is what illuminates the LED and therefore lowering the current will lower the brightness of the LED's.

    All LED drivers can be thought of as constant current supplies as this is the most important controllable parameter. Therefore they are designed to ensure the LED's operate correctly and buying one off the shelf should require no external circuitry for operation other than the wireing to and from power supplies and LED's.

    Rob
     
  12. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    Rob, I can't thank you enough for taking the time to teach me some things. I am a software developer by trade. I'm trying to break out of the confines of the machine so Ic an "control" the physical world. I really wish I had some lottery winnings so I could go back to school as a mature adult to buckle down through an EE program just for fun.
     
  13. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    No Problem at all im glad i could be of help.

    Theres is always time to tinker!!! and trust me thats how you learn. Providing you tinker at low voltage and current of course!

    Rob
     
  14. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    That is really what I need to do. I have some small leds. I need to get a small dimmable driver and play around. Much safer than do that with these huge leds and all of this current.
     
  15. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    You just need to choose a supply that can supply a little more than the forward voltage and the current desired. Operating them in constant current mode is the right way to go.

    By the way, how many lumens do these put out? At 100W they ought to be seriously bright!
    Let me guess, grow lights?

    Bob
     
  16. j.walter.miller

    j.walter.miller

    9
    0
    Dec 7, 2012
    They put out about 2000 lumens give or take largely based on their color.
     
  17. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Hmm. That is barely better than a 100W incandescent (1700 lumens.)

    Bob
     
    Last edited: Dec 7, 2012
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-