do parallel connected leds consume more power?

Discussion in 'LEDs and Optoelectronics' started by rahulb, Nov 8, 2018.

  1. rahulb


    Mar 14, 2018
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    I wanted to know if leds which are connected in parallel to power source consumes more power than leds connected in series?

    I read somewhere that leds in series consume less power.

    rahulb, Nov 8, 2018
  2. rahulb

    hevans1944 Hop - AC8NS

    Jun 21, 2012
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    Venice, Florida, USA
    Each LED will consume an amount of power equal to its forward voltage drop at whatever current is passing through the LED. If you connect LEDs in parallel, there is no way to guarantee that each will have the same forward voltage drop, nor that the current will distribute equally across all the LEDs connected in parallel.

    If you want to connect LEDs "in parallel" place a current-limiting resistor in series with each LED, then wire as many of these resistor/LED series combinations in parallel with each other as desired. Again, the power dissipated will be the forward voltage drop across a given LED multiplied by the current through that LED.

    You do the math. Relying on "glittering generalizations" such as "leds in series consume less power" will only mislead you, and such statements serve no useful purpose. Learn about electricity, Ohm's Law, Kirchoff's Current and Voltage Laws so you can participate meaningfully on this forum.
    hevans1944, Nov 9, 2018
    (*steve*) likes this.
  3. rahulb

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
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    Mid way between Beijing and the Ronne Ice Shelf
    I agree. The LEDs (properly driven) will consume the same amount of power no matter how you connect them.

    It's the rest of the circuit that you need to look closely at.

    For a given voltage power supply, and if you use only linear elements to set the current through the LEDs, then a series connection is more efficient. However, there may be other considerations, and other forms of driving the LEDs that may change things.
    Last edited: Nov 9, 2018
    (*steve*), Nov 9, 2018
  4. rahulb


    Jan 5, 2010
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    Worcester, MA
    To be more specific, if you need to run 3 LEDs, each with a forward voltage of 3V off a 12V supply, then putting them in series is more efficient then putting them in parallel. If you had a 3.7V supply, you could not run them in series but running them in parallel would actually be more efficient then running 3 in series off the 12V supply.

    BobK, Nov 10, 2018
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