Help increase the frequency of a LED driver

Discussion in 'The Projects Forum' started by Derek Speegle, Nov 24, 2015.

  1. Derek Speegle

    Thread Starter New Member

    Nov 24, 2015
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    Hello!
    I am working on a project that has the goal of increasing the output frequency of an LED driver from 600hz to about 10khz. It would be simple to increase the frequency in the code, as I've done it before and had the desired effect. However, I need to be able to take the output of this driver and increase its frequency while keeping the signal. This is because out cameras can pickup flicker from LEDs at an extremely high rate and I need to get up to 10khz to be safe. I think I'm kind of in the right zone as I've been trying to work with Phase-Locked Loops but have yet to create a working prototype. Heres a link to the circuit I was trying to work with, http://www.eetimes.com/document.asp?doc_id=1230513. Does anyone have any ideas on how to increase the frequency while keeping the signal? Keep in mind that it's an LED driver so this signal will be on the other end of a MOSFET.
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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  3. Derek Speegle

    Thread Starter New Member

    Nov 24, 2015
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    Wow thanks, that does seem pretty easy to get going. Do you think that this would work on the output of the driver? I worry that the current coming through it might be too much. Should I use this and put it through a driver after the signal is enhanced? If so, how can I drop the current coming out of the driver but keep the signal?
     
  4. Derek Speegle

    Thread Starter New Member

    Nov 24, 2015
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    So I did some tests and the max amp draw through the line is 250 mA. If I put a MOSFET on the output of the PLL to drive the LEDs will that essentially divert the current and keep the PLL safe?
     
  5. Derek Speegle

    Thread Starter New Member

    Nov 24, 2015
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    Two more questions, can that PLL handle frequencies as low as 600 hz and output as low as 10khz? ALL of the newer PLL chips are restricted to the Mhz range and wont allow that low of a frequency. The one you posted doesnt seem to have a listed minimum value so it should work for me? It's from 1984 but I found some on ebay haha. Second question, is there any reason i cant just take a microcontroller and just have it output the same signal that it receives but at a higher frequency? If I do that, would I need to do anything to the signal before it reaches the MCU?
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    If you can use a microcontroller its better, choose one that you know how to programme,
     
  7. Derek Speegle

    Thread Starter New Member

    Nov 24, 2015
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    Ok I'll go with that, I've been working on adding MCUs to my projects and have been learning the programming. Any hints for not frying the MCU when I connect the output of the driver to an input of my MCU? Also, the output is a bit of a strange sawtooth waveform. How should I hook it up? On an analog input or digital output? Should I run it through a circuitry that would output square waves before it gets to the MCU or will the digital input kinda convert it for me?
     
  8. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need to post your circuit that you intend to use, so we can help you further.
     
  9. Derek Speegle

    Thread Starter New Member

    Nov 24, 2015
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    Here is a blunt representation of my current design. I dont really have a good circuit design program so I just threw something together on partsim so that you got the basic idea. The Microcontroller for the new signal is the MSP430FR4133. I can see it being confusing so please ask any questions you might have.
     
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