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Poorman’s Buck – High Power LED driver


Poorman’s Buck is a simple, constant-current high power LED driver capable of driving 350mA to 1A of output current. It is compact (footprint is 1 x 1.5 inches) and easy to build, yet very versatile.

Input power supply voltage can be anywhere between 5 to 20V (must be higher than the connected LED’s forward voltage drop). Up to 5 LEDs can be connected in series, and by parallel connecting the series connected LEDs, up to 18W total of LEDs can be driven (with 20V power supply).

Output current is configurable; 350mA, 700mA, or 1A using included parts. In board potentiometer can lower the output current down to about 9% level – which can be used as a dimmer. Full dimming control can also be done via the PWM input, making Poorman’s Buck a perfect building block for Arduino or other microcontroller projects.

For technical details please view my instructables.

You can purchase full kits or just the PCBs. Please use the buttons below to purchase.

*** Poorman’s Buck Kits and PCBs are sold out and discontinued. ***

30 Responses

  1. Hahihula

    Hi,
    I really appreciate the led source. I would be glad if you could post equations for calculating the sense resistor value, and inductor value?
    Thanks

    April 24, 2014 at 8:52 am

  2. Greg

    Hi, thanks for publishing this great circuit! In the Instructables you mention that the potentiometer can be replaced with resistors. How would you calculate the required sizes?

    Thanks,

    Greg

    March 2, 2014 at 2:03 pm

  3. electroman

    I believe it will cause losses..and simply won’t work… I wish it was like capacitors..the bigger..the better.. :-D

    January 2, 2014 at 3:51 pm

  4. electroman

    can I use a bigger inductor? Its tough to find inductor in single quantities.
    I have 1000 and 3000uh

    December 20, 2013 at 11:48 am

    • 1000 uH would be too big. I’d only go as high as 100 uH.

      Aki

      December 20, 2013 at 1:08 pm

  5. Mayank

    Hi Aki,

    Would it be possible to remove the second comparator for PWM and use 3 comparators in a LM339 to design a manual RGB driver? What would it take? Should I just remove the circuit that connects to second comparator and the diode at the output?

    Thanks
    Mayank

    December 1, 2013 at 11:48 pm

    • Sorry for super late reply.
      Yes you can just use one comparator to do the job if you don’t need PWM input.
      Be careful however for interference between comparators when you combine more than one driver.

      Aki

      December 13, 2013 at 3:17 am

  6. philip blades

    Are you getting anymore poormans buck led drivers in. Thanks.

    January 6, 2013 at 7:08 am

    • I had been developing the updated version of Poorman’s Buck with higher current capability. However since there are many good buck drivers commercially available (and they are inexpensive) I don’t see the value in creating a kit.

      Aki

      January 6, 2013 at 1:19 pm

      • Richard

        I’ve been trying to find some high power led drivers that are relatively inexpensive. Can you point me too them? I thinking under $10 each as being inexpensive. I was going to try to have some pcb done up of the poormans buck but the gerber files I got from instructables don’t seem to work. with OSH Park. My plan is to use either multiple drivers to strobe a bunch of leds or to have one driver strobing them by switching the load. Any input would be nice as I’m been digging all over about LED drivers and I believe I am just scratching the surface. I was thinking of even just turning on and off the basic LM317 constant current circuit by switching its power.

        Rich

        March 14, 2013 at 10:35 pm

  7. Hi Friend
    What is the input current of poor man buck
    All your joule theiefs are 1.5 v input ?

    November 30, 2012 at 10:43 pm

    • Hello,

      Input current of Poorman’s Buck depends on the load(output) current and voltage. As with any buck converter, input current is always lower than the output. So if you have 1A at the output, the input current is less than 1A.

      My Joule Thief circuits are designed for 1.5V battery.

      Aki

      December 1, 2012 at 12:28 pm

  8. cozzz

    Aki,
    I bought several of the Poorman’s Buck from you and have only assembled one. I’m pretty sure I assembled it right. I’m using an old laptop power supply rated at 19.5v DC. When I connect it to the Buck I’m still getting 19.5v on the LED output. What did I do wrong?
    cozzz

    October 17, 2012 at 12:21 am

    • Do you have any LEDs connected to the output? As Poorman’s Buck is a constant current driver, if the output is open, you will get the supply voltage at the output. Constant current driver means that the circuit adjusts the output voltage to get the desired current – if there are no LEDs connected, or too many LEDs connected in series, the output current won’t reach the set current, so the circuit tries to give more current by outputting the maximum voltage it can give.
      If you want to test the circuit without connecting a LED, you can use an ammeter (or multimater set to 1 A DC or higher current mode) and connect to the output. Even though this seems like a short circuit, Poorman’s Buck will regulate the output current. If you move the potentiometer, you will see the current change.

      October 17, 2012 at 1:17 am

      • cozzz

        Sorry, I’m a rookie at electronics. I did not have any LED’s connected to the output. I will give that a try.
        Thanks for your reply.
        Cozzz

        October 18, 2012 at 12:13 pm

  9. DesignByMarc

    Hi

    I was wondering if this driver could be used for powering 12x 1W 350mA Osram dragon leds. I want to put 4 sets of (3 pieces in series) parallel?

    grtz Marc

    October 9, 2012 at 10:48 am

    • I think you’d want to connect 4 in series, and 3 of them in parallel. This way each LED will get roughly 333 mA while Poorman’s Buck supplies 1 A. The power supply needs to be about 16 V.

      October 9, 2012 at 10:55 am

  10. Paul

    Can this unit be tweaked to deliver 3 amps max at 30Volts?
    Then it would be a very nice tool make a HUGE flashlight :-) with 9 or 10 times a XM-L U2 led

    October 2, 2012 at 8:04 am

    • You can change some parts to get higher output current, but the voltage can’t exceed 20V.
      I get this question a lot, so you can find detailed answers in the comment section of my instructables page. ( http://www.instructables.com/id/Poormans-Buck/ )

      October 2, 2012 at 10:52 am

      • Paul

        Thank’s for your reaction and apologies for posting twice.
        Will the boost method generate enough voltageto operate say 4 leds on an input voltage of say 5 volts?

        October 2, 2012 at 5:16 pm

        • Poorman’s Buck is a buck converter – which is only capable of lowering the voltage. If you need to boost voltage, you might want to check out my Universal LED Driver. This one can boost 5V to 12V or higher.
          Aki

          October 2, 2012 at 5:20 pm

  11. sourov chall

    i like this project ,i created this project please saw this ckt diagram,and other information.
    thank you.

    June 24, 2012 at 4:07 am

  12. Will

    Hi Aki,

    Awesome! Thanks for the quick reply.

    Will

    June 9, 2012 at 10:49 pm

  13. Will

    Hi,

    I’m not too clued up when it comes to DC so what I wanted to know is, if I were to use 6-7 of these drivers, would I be able to use 1 power supply?
    I don’t mean a wall wart. Something like a 10amp 24v DC regulated psu.

    Thanks

    Will

    June 9, 2012 at 10:37 am

    • Hello Will,

      Yes you can parallel connect Poorman’s Bucks as long as the power supply can support the current draw. 24V 10A supply can possibly drive 10 of Poorman’s Bucks.

      Thanks,
      Aki

      June 9, 2012 at 12:10 pm

  14. Phil

    Hello
    I would like to use this to power a 20w high power LED. I need 12v @ 1800mA. is it possible to change this circuit to achieve the higher current?

    Thanks,
    Phil

    May 30, 2012 at 2:39 pm

    • Hello Phil,

      It’s not impossible to do 1800mA output, but the inductor and the Schottky diode need to be beefed up. The problem is that the next size up Schottky diode (5A) is too large to fit on my PCB. Inductors that can handle 2A are not too hard to find. So if you are making your own PCB, adjust the hole size for the Schottky and the spacing around it.
      The current sense resistor (R10 and 11) will have to be about 0.6 ohm each.
      Aki

      May 31, 2012 at 7:13 pm

  15. Thank you for the quick reply!

    May 22, 2012 at 1:52 pm

  16. What type of resistors did you use for these LED lights?

    May 22, 2012 at 1:15 pm

    • For current sensing, I use 1 ohm 1W metal film resistors.

      May 22, 2012 at 1:18 pm

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