Controllable LED Driver Design

Discussion in 'General Electronics Chat' started by arman74, Jun 14, 2019.

  1. arman74

    Thread Starter New Member

    Jul 1, 2017
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    Hey guys.
    I need to control about 50 Cree LEDs lights with my microcontroller. As you know for better results we control the current of the LEDs instead of their voltage.
    So I would be thankful if you introduce me any ICs generated for this or any schematic diagram or any help.
    Thanks.
     
  2. Dodgydave

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    Jun 22, 2012
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    What current range are you wanting to use,? then we can tell you which regulator to use.
     
  3. mvas

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    Jun 19, 2017
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  4. danadak

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    Mar 10, 2018
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    Are these all in a series string, series/parallel, parallel (all individual) ?

    Fixed current or variable ? Range of current ?


    Regards, Dana.
     
  5. arman74

    Thread Starter New Member

    Jul 1, 2017
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    It varies between 0 to 350 mA per LED.
     
  6. arman74

    Thread Starter New Member

    Jul 1, 2017
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    I use different LED colors and for each color I need to have control.Every same LED colors are in series.
    As I said the current varies between 0 to 350 mA.
     
  7. Dodgydave

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    Jun 22, 2012
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    If they're all in series, then the psu Voltage is going to be very high, how are you going to wire them, 5 rows of 10 in series??

    This can be done with ready made modules or you can do it with a regulator and Mosfets.

    Can you post the Cree led details please.
     
  8. arman74

    Thread Starter New Member

    Jul 1, 2017
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    Im not putting al of them in series.Every color has 10 LEDs and I need 5 colors.So I have to implement 5 different control circuits for each color column that each column has 10 series LEDs.

    My application is that the user must be able to control the intensity of each color individually.

    These are the LEDs information.
    https://www.cree.com/led-components/products/xlamp-leds-discrete/xlamp-xp-e2
     
  9. danadak

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  10. Dodgydave

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    Jun 22, 2012
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    Each led takes 3V drop, 10 leds in series is 30V, so your psu needs to be approx 35V or higher, @1amp min Constant Current control,.

    Do you want to get ready made current modules or are you going to make your own circuits using Mosfets and Linear regulators?
     
  11. Sensacell

    Moderator

    Jun 19, 2012
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    Use an LED driver chip for each one.

    Each one can be controlled by a PWM input to control brightness.
     
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  12. danadak

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  13. arman74

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    Jul 1, 2017
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    Im going to make my own circuits using Mosfets and Linear regulators.
     
  14. arman74

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    Jul 1, 2017
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  15. Dodgydave

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    Jun 22, 2012
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    You can use the LM338 5Amp regulator it will will run on 40V,so you can put 10 leds in series and control the current, it will need an Heatsink, if you use the module they need a Pwm signal as well..
     
  16. danadak

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    arman74 likes this.
  17. MisterBill2

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    Jan 23, 2018
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    You can use Pulse Width Modulation and suitable power FET devices and a single current sense resistor for each of the series strings, and then you are not going to need to design any analog control circuits. Just set the voltage for each string at a level that gives about 90% of max output at 100% on time. Then you can do it all in software.Just use a high enough PWM frequency to avoid visible flicker. AND heat-sink those series switch transistors. Probably the cheapest, easiest, most compact way of doing it.
     
  18. danadak

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    Mar 10, 2018
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    Actually because Vled highly T sensitive you want to drive with current.
    And fact from one LED to another significant variance of Vthreshold.
    Driving with current also helps in uniform brightness LED to LED. Not a
    guarantee but helps. So a PWM driven current regulator is desired approach.

    Plus PWM driver chips typically have well controlled MOSFET internal driver
    interface.


    Regards, Dana.
     
  19. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    The link in post #8 is for red LEDs only. Do you have links for the specs of the other four colours?
     
  20. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    I neglected to mention the "single current sense resistor"should be connected to an analog input so that the current could be set. And setting the high current limit with a resistor may be a bit less efficient but it is very simple and quite reliable. And also it is cheap and easy.
     
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