What exactly does an LED driver do...?

Discussion in 'General Electronics Chat' started by cgc210, Sep 4, 2012.

  1. cgc210

    Thread Starter New Member

    Aug 18, 2008
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    I am looking for a driver that keeps/holds the forward voltage to no more than 6 volts. Does an LED driver rated @ 6volts-12 volts limit the the vf to 6volts, or does it just function between the 6v-12v range. .

    A supplier that I posed this ? to did not know. Others seem to think the voltage works within the 6v-12v range, none seem to know exactly what the drivers, they sold, did. Can anyone provide a detailed answer. Thanks much
     
  2. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    http://forum.allaboutcircuits.com/showthread.php?t=19075

    Yeah, I know. The title looks wrong. You will find the start of your answer in the second paragraph.

    Excerpt from another article:

    LEDs aren't resistors. They don't work like Ohm's Law. An LED that is barely on at three volts will be completely smoked if you apply four volts to it. It has this “breakover” characteristic like a rectifier diode, because it IS a diode. Once you get to the breakover voltage it starts letting current through in an almost unlimited manner. That is why you must use some way to limit the current through an LED. The easiest way is to use a resistor. Say you have a 9 volt battery and an LED that needs about 3 volts to start up. You use Ohm's Law to calculate a resistance that will keep the current under the usual .02 amp limit. Calculating from the fact that you have 6 leftover volts that the LED doesn't need, the math goes like this:

    R = V/I
    R = 6 volts/.02 amps
    R = 300 ohms.

    Any resistor more than 300 ohms will protect that LED from smoking.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    As has been mentioned, think current, not voltage. Once you have enough voltage the LED responds to current, not voltage. A resistor is usually all you need, but if you want something a bit fancier a simple current regulator will work well. 20ma (0.02A) is the normal current.

    [​IMG]

    In this case you would want a 62Ω for R1. You could use 2 120Ω resistors in parallel.

    My main article is LEDs, 555s, Flashers, and Light Chasers

    The other shown is my working area for modifications.

    My blog - Bill's Index
     
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    In simplest terms an LED driver is a current regulator that monitors it's output current and constantly adjusts it's output voltage to maintain a specified output current as load conditions change. I don't know if the particular device you're looking at is specifying a range of input voltages or output voltages.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Another equally valid definition is a simple on/off switch, something that would turn a LED on or off.
     
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