SST90 Driver

Discussion in 'The Projects Forum' started by trader007, Aug 26, 2014.

  1. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
    19
    I want to make a guide on how to do this. I have an authentic SST-90 LED diode that I want to drive at full power. The only drivers I can find are ones for flashlights, which won't work for my landscape lighting because of the multi-mode "features". I simply cannot find a simple direct driver to buy, so I must make one.

    Input source voltage- 6vdc
    Diode forward voltage- 2.8-3.2v
    current- 10a max

    So I found this neat little driver-

    LDO10C-005W05-SJ
    http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=156141267&uq=635446457054251336


    Datasheet- http://www.artesyn.com/power/assets/ldo10c_1191530952.pdf


    and it seems perfect for my application. However, I need help on what capacitors and adjusting resistors to use. The datasheet is too vague and I am not a good enough engineer to know these things.

    Here is a pic from the datasheet-

    [​IMG]

    If you guys help me get a working module going, I want to create a full how-to guide for various voltages (6v, 12v, 24v) and post it here. I think it will draw a lot of attention for the simple fact that there isn't a guide like this on the web, that I can find anyway....
     
  2. embpic

    Member

    May 29, 2013
    187
    3
    you have to check for buck converter. BTW what is your application. so i can suggest right driver.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    This is a voltage regulator. For LED driving, you need a constant-current regulator; different animal.
     
  4. trader007

    Thread Starter Active Member

    Feb 27, 2010
    222
    19
    Well I actually found this thing off a picture from some older website (through google searching) and someone was using it to drive an SST90.

    The problem was the additional components he was using was not listed- as the website was gone and google's cache didnt save everything.

    I suspect it was working for him because he was relying on the device's 10a maximum output as its current limiter.

    I just want to drive an SST90 off a 6v source for my landscape lighting. I can do other LED's just fine, but getting 3v@10a current limited is not an easy task.... :/
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I did a quick search for suitable 6VDC input LED drivers and didn't find anything.

    Here is a simple linear adjustable constant-current driver. Disadvantage is that it will make a bit of heat. Advantage is that is simple.

    I would recommend that you start by driving your LED with 1A or less. You will have to heatsink the backside of the LED and the FET.

    If you drive the LED with 10A you will burn it up (instantly). The data sheet shows that the normal driving current is 3.3A or less.

    The first plot shows the LED current as a function of input voltage and Pot wiper position. The second plot shows that the output current (at one wiper position) decreases at progressively higher temperatures (a good thing).
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    You cant put 10A through that LED without blowing it up...
     
  7. xxjomamaxx44

    New Member

    Sep 20, 2014
    4
    0
    Yes he can! You ppl need to kniw what your talking about b4 you open your mouths.

    A Luminous phlatlight sst-90 can handle as much as 13amps with proper heatsinking. Max data sheet rated @ 9 amps. @ 13 amps you can expect 1800-2100 lumen

    A pt-121 can take 19amps constant and like 30 amps pulsed.

    Op- please describe more about how u an on using the phlatlight, power source? Size and type of host?
     
  8. #12

    Expert

    Nov 30, 2010
    16,343
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    Datasheet here says 9 amps, but the sticking point seems to be the idea that you need to limit the current, not the voltage. A simple resistor of 3V/9A = .33 ohms, 26.73 watts (buy a 50 watt resistor) will control a 6 volt source from smoking that SST-90 LED. That's an awfully large resistor, but any linear regulator is going to waste that much power.

    What you have in your LDO-10C is a switching regulator with 91% efficiency. Excellent choice, but it's a voltage regulator. You still need to add a current limiter. Perhaps adjust the LDO-10C to 4.08 volts and add a resistor of 1.08V/9A = .12 ohms rated for 20 watts.

    Let's massage the numbers a little bit. My rule of thumb is to waste 15% of the voltage in the current limiter. That means to adjust the voltage regulator to 3.45 volts and use a resistor to waste .45 volts at 9 amps. That's .05 ohms at 4 watts (buy a 10 watt resistor). Here's a nice one for $1.62

    http://www.mouser.com/Passive-Compo...Z1z0wo4tZ1z0wn1gZ1z0wlcvZ1z0wn9m&Ns=Pricing|0

    I can not find the math for Rtrim on the datasheet so I can't say how to adjust the voltage correctly!
     
    Last edited: Sep 20, 2014
  9. xxjomamaxx44

    New Member

    Sep 20, 2014
    4
    0
    #12 is right on,
    The only thing I would add is that in terms of battery use vs whats available as current limiting devices, a resistor is not very efficient, as per any liner device when your input voltage is alot higher than your working voltage, not so bad when supply is close to Vf, but in your sst-90 setup 6 volt supply - 3.8 working voltage = 2.8 volts of battery power/life that will be dissipated as heat.
    If you could lower your supply then a resistor would be fine. if you cant, I would try to use a buck driver, @ 10 amps you will encounter a good amount of voltage sag and a good buck driver should get you close to 90-95% efficiency.

    Now all this is pointless if your 6 vdc is coming from a wall plug and not battery power.

    Really need more info from the OP.

    And for you guys saying 3 amps is the max, thats just the current level used for official binning and output numbers.
    I have a sst-90 directly mounted to a copper slug that runs @ 12.5 amps and never comes close to exceeding the maximum junction temp.
     
    Last edited: Sep 20, 2014
  10. #12

    Expert

    Nov 30, 2010
    16,343
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    The LDO-10C is a buck driver @ 10 amps with 91% to 95% efficiency.
    Problem solved. :)
     
  11. xxjomamaxx44

    New Member

    Sep 20, 2014
    4
    0
    Word. Must have glossed over your recommendation for the ldo-10c.
    But yea, done and done.
     
  12. xxjomamaxx44

    New Member

    Sep 20, 2014
    4
    0
    Ive been thinking about thus a little more and I even revived an old sst-90 build thats been sitting in a drawer.

    OP- you could use a newer version of the east-92 driver, its basically a direct drive setup that uses a 30amp (70n02) mosfet for high speed switching, you also have the choice of using or not using a Tiny13a processor for modes ir no modes.

    I think this would be perfect for you because they offer a zener diode mod version for inputs higher than 5v that can be modded to work for your setup

    http://www.mtnelectronics.com/opencart/index.php?route=product/product&path=67&product_id=228
     
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