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the ultimate LED regulator or close enough

Discussion in 'Electronic Design' started by [email protected], Dec 1, 2012.

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  1. Guest

    I live on a boat and an always delt with electrical efficiancy. And its time to upgrade from my super bright LED to some of these new 3 and 5 watt leds.
    The ulimate dc dc buck bost swiching regulator
    input 3 to 18 vdc
    output regulated 2.3 vdc to 13.8 vdc
    regulated current 3A
    regulated 10% duty @ 10khz 10A
    both pwm and 100%duty
    I would like to be able to Run the light with as little energy as possible. I'm thinking 4 leds, 2 parralel and 2 serries.
    When I start looking for possible reglators I am overwhelmed.
    Any helping ideas. I have basic soldering and electronic skills.
    Thank you Wiley
  2. miso

    miso Guest

    I'd search for a dedicated chip for the task.

    That said, you really don't want to parallel LEDs. Only the cheap ass
    Chinese designs do that. Every diode is a little different, and you will
    get current hogging if you parallel them.

    I would avoid the buck-boost. Pick a scheme and live with it. My
    preference would be a discontinuous conduction boost. Keep it simple. A
    LED can deal with ripple fine since the eye will average out anything
    over a few hundred Hertz.

    If you put enough LEDs in series so that you always need a boost
    converter, the design becomes very easy with off the shelf chips. What
    is normally done to make a LED driver is to send the boost inductor
    output (via blocking diode) to the string of LEDs, and then put a
    resistor from the LED string to ground. Then set up the voltage sense
    pin of the boost chip so that it senses the voltage across this
    resistor. By regulating the voltage across the resistor, you have
    effectively regulated the current in the LED string. The inductor flies
    back to whatever voltage is appropriate.

    I recall Micrel made some cheap chip to do this, and LTC made a better
    though more expensive one. If for some reason the diode string is
    broken, the inductor voltage will fly high enough to damage the driver
    transistor. Some chips protect for this, and some don't.

    But any basic boost converter circuit can be made to do this. The longer
    the string of LEDs, the less you have to worry about the loss of power
    in the sense resistor.
  3. Guest

  4. Guest

    This is to Miso
    Miso thank you very much. I'll look up the info you gave me. I've been driving fork lift for the last 6 years and lost touch with my hoby of electronics. I was rased in Yokohama Japan from 1965 to 1973, 10 years old to 18. Love the sushi. Achihbara (Spelling) in Tokyo is incredible for electronis of all types.
    Thanks again Wiley
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