Cree claim 160 lumens per what from LED

[JohnR66]

Tooting their own horn, but this is the meat from their press release:

"Cree's tests confirmed that the 1mm x 1mm LED produced 173 lumens of light
output and achieved 161 lumens per watt efficacy at a color temperature of
4689K. The tests were conducted under standard LED test conditions at a
drive current of 350mA, at room temperature."

Eefficiency is interesting, but more so at that color temp. Most effecient
LEDs are cool white.

 

[Andrew Gabriel]

Tooting their own horn, but this is the meat from their press release:

"Cree's tests confirmed that the 1mm x 1mm LED produced 173 lumens of light
output and achieved 161 lumens per watt efficacy at a color temperature of
4689K. The tests were conducted under standard LED test conditions at a
drive current of 350mA, at room temperature."

Eefficiency is interesting, but more so at that color temp. Most effecient
LEDs are cool white.

That's still far too cool to be particularly useful.
They've got to be working at 3500K and 2700K to get
any kind of mass adoption IMO.

 

[Don Klipstein]

Tooting their own horn, but this is the meat from their press release:

"Cree's tests confirmed that the 1mm x 1mm LED produced 173 lumens of light
output and achieved 161 lumens per watt efficacy at a color temperature of
4689K. The tests were conducted under standard LED test conditions at a
drive current of 350mA, at room temperature."

Eefficiency is interesting, but more so at that color temp. Most effecient
LEDs are cool white.

It has generally been the case that cooler white LEDs (CCT 5000-6500 K)
had greatest overall luminous efficacy.

However, that is theoretically increased by adding more phosphor to
convert more of the blue light to yellowish light, despite the Stokes
loss. Why it usually does not?

1. The phosphor may absorb some of the yellowish light, so that may limit
the amount of phosphor that can be added before overall luminous efficacy
starts decreasing.

2. Adding more phosphor can make the overall color more green than
blackbody. Adding a more reddish phosphor will decrease luminous efficacy
compared to a less reddish phosphor.

However, it still appears to me that if the phosphor does not absorb its
own output, overall luminous efficacy should increase as CCT decreases
towards maybe 4,000 K or upper 3900's K or so.

The lower CCT may be a sign that phosphors are being developed that
absorb less of their own output.

Another consideration: When Osram issued a press release on its high
efficiency laboratory prototype power LED, the CCT was 5000 K. Also
notable was that the cromaticity was greenish.

http://www.ledsmagazine.com/news/5/7/22

A combination of red/reddish LEDs and yellowish-whitish ones greener
than blackbody is described in US Patent 7,213,940, owned by what is now
Cree Lighting. My guess is that their LR-4 and LR-6 fixtures use this.

So I wonder if this latest Cree laboratory prototype with lowish CCT is
more green than blackbody? If so, I suspect that more efficient LED
lighting fixtures based on US Patent 7,213,940 will be in the pipeline.

- Don Klipstein ([email protected])

 

[JeffLauderdale]

The real horse race is between mixed primary LEDs and phosphor types.
The race for increasing lumens per watt will continue forever, but will
both approaches to desirable CRI and K values continue that long? Any
odds on mixed vs. phosphor?

 

[TKM]

The real horse race is between mixed primary LEDs and phosphor types. The
race for increasing lumens per watt will continue forever, but will both
approaches to desirable CRI and K values continue that long? Any odds on
mixed vs. phosphor?

Rather than the LED technology itself, I think the mixed vs. phosphor
"winner" will be determined by how the color is measured. The current
measures of chromaticity and color rendering were not built with lighting
designers and users in mind and so they do not do a good job of describing
lighting quality from a color point-of-view. The problems became apparent
when white-light LEDs appeared; so new metrics for solid state light sources
are being developed by NIST and others.

Terry McGowan

 

[Andrew Gabriel]

The real horse race is between mixed primary LEDs and phosphor types.
The race for increasing lumens per watt will continue forever, but will
both approaches to desirable CRI and K values continue that long? Any
odds on mixed vs. phosphor?

Actually, I think the inhibitor to getting this technology widespread
in the marketplace will be price. Commodity pricing almost never
happens until the relevant patents have expired, so the delay will be
waiting for these relevant patents to expire and the resulting
genuine competition between manufacturers uninhibited by patents and
licensing.

 

[Andrew Gabriel]

Rather than the LED technology itself, I think the mixed vs. phosphor
"winner" will be determined by how the color is measured. The current
measures of chromaticity and color rendering were not built with lighting
designers and users in mind and so they do not do a good job of describing
lighting quality from a color point-of-view. The problems became apparent
when white-light LEDs appeared; so new metrics for solid state light sources
are being developed by NIST and others.

Consumers don't know or care about the measures.
They do however notice that the light looks blue,
and/or colours look wrong under it. The
manufacturers have to work out how to make them
look like filament lamps, just as they did with
retrofit CFLs.

 

[JohnR66]

Rather than the LED technology itself, I think the mixed vs. phosphor
"winner" will be determined by how the color is measured. The current
measures of chromaticity and color rendering were not built with lighting
designers and users in mind and so they do not do a good job of describing
lighting quality from a color point-of-view. The problems became apparent
when white-light LEDs appeared; so new metrics for solid state light
sources are being developed by NIST and others.

Terry McGowan

What are these *quantum dot* LEDs I'm hearing about? They are supposed to
be able to produce new colors not common in LEDs now, such as pastels and
true purple. Not sure about white. They are supposed to start showing in
some next year's holiday lighting products. Should be interesting.

 

[Don Klipstein]

Victor Roberts wrote:
[snip]

Hopefully, any new standard will be applicable to all light
sources, irrespective of their technology.

I am far from an expert on LEDs, but considering some of the relevant issues,
imo, the only "standard" which matters is wall-plug efficiency. I think the rest
is aesthetics, which can be argued ad infinitum by either party.

I can't quite see how any new standard will help LEDs beat the Na 210 lm/w
limit, but you never know what technology will bring one day.

I have heard of a supposed theoretical limit for overall luminous
efficacy of a white light source, close to that figure, but I thought it
was not related to the maximum achieved in a practical LPS lamp.

I remember previous discussions on this maximum theoretical luminous
efficacy, as in being the number of lumens in 1 watt of white light. This
figure varies accordingly to how one comes up with or decides what is
"white light". I mention 16 different figures for lumens in 1 watt of
"white light" in:

http://members.misty.com/don/lfunfac2.html#ole

That includes equal energy per unit wavelength over 4 different
wavelength ranges, 7 figures for 400-700 nm portion of blackbody
radiation for 7 different temperatures, 1 figure for one laboratory
prototype white LED mentioned in a press release (linked), and 2
hypothetical trichromatic and 2 hypothetical dichromatic white/"white"
light sources.

- Don Klipstein ([email protected])

 

[Don Klipstein]

Don Klipstein wrote:

(in part)

Quoting from your above webpage for 400-700 nm portions of blackbody
radiation at a few color temperatures:

5500 K: 254 lumens/watt

Quoting from Wiki's Sun article (section Luminosity):
http://en.wikipedia.org/wiki/Sun

5778 K: 98 lumens/watt (efficiency)

Someone is wrong here. I don't know who, so can you explain the difference?

The Wiki figure for the sun is lumens per total watt of radiation, and
is the luminous efficacy of the Sun.

My higher figure is lumens per watt of only the 400-700 nm portion of
5500 K blackbody radiation.
If I don't exclude UV or IR, I come up with 89 lumens per watt of 5500 K
blackbody radiation. For a 5778 K blackbody, I come up with 92
lumens/watt.

- Don Klipstein ([email protected])

 

[TKM]

I believe at some point, some very lucky engineer/researcher will produce
a TRUE white LED... rather than a doctored (phosphor) product, , , and
all existing issues will quietly go away.

Wes

Maybe. But there is that nasty thing called lighting quality as interpreted
by the human visual system to contend with.

Humans are used to continuous spectra sources with lots of deep red (outdoor
daylight, incandescent lamps) and so the colors of people and things "look
funny" when the light is spectrally distorted. As we've learned, light can
look white, but have terrible color rending. LEDs with their narrow band
output have inherently poor color rendering compared to white phosphors
which emit much more broadly. Sure, mixing the light of a thousand LEDs
each emitting a slightly different wavelength would result in white light
with good color rendering, but can that be made to work?

Terry McGowan