Re: High Efficiency White LEDs

"Victor Roberts" <xxx@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:0v4s53deinc711amgcbj25rc5f0c91n73j@xxxxxxxxxx
On Tue, 29 May 2007 15:43:58 GMT, "JohnR66" <nospam@xxxxxxx>
wrote:

After trying a couple Cree XR-E based flashlights, I must say I'm
impressed.
I've heard way over 100 lumens per watt designs operating in the labs
several months ago by various manufacturers, but nothing of late. Anyone
got
the inside scoop?

Cree was bragging about 131 lm/W from a low power LED, and
last week at LS:11 Nichia was bragging about one over 150
lm/W. However, these are all at a junction temp of 25C
which cannot be achieved without a refrigerated heat sink,
and they are not power devices, which are less efficient.

As for the XR-E LEDs, I'm aware the efficiency drops due to operating die
temps, but even so, the l/w figures seem to remain in the upper range of
CFLs (50-70 range).

In my mind, the more important question is what is the
minimum guaranteed efficacy of a LED that a person can
actually buy, measured at a junction temperature that can be
achieved in a real application. Last time I checked, about
6 months ago, the answer was "about 40 lm/W" and at a cost
per lumen that was at least 10 times that of a CFL.

BTW- I learned at LS:11 that the LED manufacturers are well
aware that they could solve white LED color issues by using
UV instead of blue LEDs as the pump, but they don't want to
take the Stokes Shift hit to the efficacy.

--
Vic Roberts
http://www.RobertsResearchInc.com
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The next few years should prove interesting. The current most efficient LEDs
are ideal for portable lighting. They do have a ways to go for general
lighting where price, CRIs and color temp are more of importance.
John


.

Relevant Pages

  • Re: High Efficiency White LEDs
    ... I've heard way over 100 lumens per watt designs operating in the labs ... several months ago by various manufacturers, ... Cree was bragging about 131 lm/W from a low power LED, ... UV instead of blue LEDs as the pump, ...
    (sci.engr.lighting)
  • Re: Two questions - LED Lighting and archive for this group.
    ... I bet the intensity of white LEDs doesn't drop at the same ... I cannot find any additional LED lumen maintenance data, ... lets take a look at some CFL data. ... Lumens has been defined as the output at 40% of rated life. ...
    (sci.engr.lighting)
  • Re: High Efficiency White LEDs
    ... I've heard way over 100 lumens per watt designs operating in the labs ... The current most efficient LEDs ... are an ideal light source. ... such as flashlights and task lamps. ...
    (sci.engr.lighting)
  • Re: High Efficiency White LEDs
    ... I've heard way over 100 lumens per watt designs operating in the labs ... UV instead of blue LEDs as the pump, ... lighting where price, CRIs and color temp are more of importance. ... My primary interest is in energy ...
    (sci.engr.lighting)
  • Re: High Efficiency White LEDs
    ... I've heard way over 100 lumens per watt designs operating in the labs ... UV instead of blue LEDs as the pump, ... lighting where price, CRIs and color temp are more of importance. ... I agree that there are a number of applications where LEDs ...
    (sci.engr.lighting)
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