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Thread: Maximum possible RGB lm/W?

  1. #1
    Flashaholic LightForce's Avatar
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    Default Maximum possible RGB lm/W?

    Hi,

    Please explain me why RGB LEDs are claimed to have maximum theoretical limit of 400 lm/W?

    I've heard that continuous white light source which emits all the energy between 400 - 700 nm can achieve only 245 lm/W.

    How many theoretical lm/W can RGBA LED have?

    How to calculate it?

    D.
    True Mag T5 45W HID is here

  2. #2

    Default Re: Maximum possible RGB lm/W?

    Please explain me why RGB LEDs are claimed to have maximum theoretical limit of 400 lm/W?

    You'd have to ask whoever came up with the estimate. It's possible that they looked at how many electrons you can move with one watt of electricity and produced a figure for how many photons those electrons could be converted into.

    I've heard that continuous white light source which emits all the energy between 400 - 700 nm can achieve only 245 lm/W.

    This figure ought to vary depending on what technology you use to produce that continuous white light.

    How many theoretical lm/W can RGBA LED have?

    No clue. I understand that inefficient green LEDs are holding back this technology. You'd have separate figures for best we have and best we think possible.

    How to calculate it?

    Don't know how you'd calculate it, but I do know how to measure it. You would look at the total energy going into the unit in watts and the total light coming out in lumens, and you would have a lumens per watt figure, same as any other electric light.

  3. #3
    *Flashaholic*
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    Default Re: Maximum possible RGB lm/W?

    The best explanation of this is here. See pages 9 through 12 (sections R1.6-R1.7). Also, the entire document is a very interesting although lengthy read.

    In short, you can get up to 400 lm/W using three sources by giving up a little color rendering (a CRI of 80). You can get a nearly perfect CRI of 98 using 5 sources with a maximum possible efficacy of about 325 lm/W. Even an expert would be hard-pressed to tell a CRI 98 source from a much less efficient broadband source. In the real world we'll never reach these numbers, but I'd be willing to bet we'll eventually get to at least 75% of them, perhaps even 90% on the outside.

  4. #4

    Default Re: Maximum possible RGB lm/W?

    That's an excellent article jtr. In it, it says "Recently, LumiLeds and Philips announced a 610 nm (orange/red) LED with a luminous efficacy of 100lm/W; and LumiLeds has reported green InGaN-based LEDs having luminous efficacies in the range 50 lm/W." Is that backwards or did Lumileds really achieve 100lm/W in red/orange?


    Quote Originally Posted by jtr1962 View Post
    The best explanation of this is here. See pages 9 through 12 (sections R1.6-R1.7). Also, the entire document is a very interesting although lengthy read.

    In short, you can get up to 400 lm/W using three sources by giving up a little color rendering (a CRI of 80). You can get a nearly perfect CRI of 98 using 5 sources with a maximum possible efficacy of about 325 lm/W. Even an expert would be hard-pressed to tell a CRI 98 source from a much less efficient broadband source. In the real world we'll never reach these numbers, but I'd be willing to bet we'll eventually get to at least 75% of them, perhaps even 90% on the outside.

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