efficacy of LED's
RHRRC
more efficacious than compact flourescents and 30 (yes 30!) times more
efficacious than 'standard' incandescents.
see
http://www.homepower.com/files/ledlight.pdf?search=led%20lighting
How is it that we have gone backwards since then?
I blame the price of oil, global warming, the Iraq war, George Bush,
the price of cheese, my dog Charlie, .......
Victor Roberts
<h.l...@connect-2.co.uk> wrote:
The author states that his meter is only measuring the light
in a small area directly beneath the lamp, and then he adds
that ridiculous headline to the start of the article.
--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.
This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
Don Klipstein
>By 1997 LEDs had already improved to the point of being three times
>more efficacious than compact flourescents and 30 (yes 30!) times more
>efficacious than 'standard' incandescents.
>
>see
>
>http://www.homepower.com/files/ledlight.pdf?search=led%20lighting
>
>How is it that we have gone backwards since then?
The chart in the above makes statements of footcandles (at some
distance) per watt. Luminous efficacy is not just that, but that times
the amount of area covered - with the LEDs having narrower beams than the
other lamps.
I have seen LED hype before. I have seen huge claims before in terms of
lumens per watt.
Sometimes those came from datasheet figures stated in terms of lumens
per watt, but those figures were for conversion between radiometric terms
and photometric terms for the output - meaning lumens out per watt of
measurable radiation out, different from lumens out per watt in.
Sometimes the radiometric-photometric conversion factor was honestly
misunderstood as efficacy of the lamp, since the datasheets mentioning
those did say "luminous efficacy" - meaning the luminous efficacy of the
emitted radiation, not the lamp. But sometimes my "hype detector" just
starts buzzing!
- Don Klipstein (d...@misty.com)
JB
"RHRRC" <h.l...@connect-2.co.uk> wrote in message
news:1150310210....@y41g2000cwy.googlegroups.com...
I blame utterly inappropriate test methods, some 'snake-oil' claims, and
*totally* outrageous conclusions. Nothing new to report then...
JB
Peter Pan
incandescent lamps are 10-20 lm/w
cfl 40-80 lm/w
leds are 15-25 lm/w
you are stating that cfl are 10 times more efficient than incandescent
(guess cfl would love this). 10*10 or 20-10 is not 40-80, first
incongruity
10*30 or 20*30 is even more efficient than LPS lamps
Have seen some cfl, claim to be several times more efficient than HPS!
Maybe if you take into account the scotopic effect. Don't believe
everything you read until you make some simple analysis.
In article <1150310210....@y41g2000cwy.googlegroups.com>,
David Lee
>>By 1997 LEDs had already improved to the point of being three times
>>more efficacious than compact flourescents and 30 (yes 30!) times more
>>efficacious than 'standard' incandescents.
>>
>>see
>>
>>http://www.homepower.com/files/ledlight.pdf?search=led%20lighting
>>
>>How is it that we have gone backwards since then?
>>
>>I blame the price of oil, global warming, the Iraq war, George Bush,
>>the price of cheese, my dog Charlie, .......
>
> The author states that his meter is only measuring the light
> in a small area directly beneath the lamp, and then he adds
> that ridiculous headline to the start of the article.
There is also a common confusion about the meaning of "Efficiency" in LEDs.
The QUANTUM efficiency of an LED is indeed close to 100%. However that
simply means that every electron passing into the junction region will give
rise to the emission of a photon of light - it says nothing about the amount
of power dissipated in moving the electron around the circuit. So efficiency
as optical-power-out divided by electrical-power-in is generally a much
smaller value.
Another problem is getting the light out of a semiconductor die once it has
been emitted - although this was much greater in the mid IR LEDs that we
were developing because of the very high refractive index - resulting in a
big hit in external efficiency. I don't think that it's a serious problem
with optical wavelength materials.
David
RHRRC
Don Klipstein wrote:
> In article <1150310210....@y41g2000cwy.googlegroups.com>, RHRRC wrote:
> >By 1997 LEDs had already improved to the point
> <snip>
> I have seen LED hype before. I have seen huge claims before in terms of
> lumens per watt.
> Sometimes those came from datasheet figures stated in terms of lumens
> per watt, but those figures were for conversion between radiometric terms
> and photometric terms for the output - meaning lumens out per watt of
> measurable radiation out, different from lumens out per watt in.
> Sometimes the radiometric-photometric conversion factor was honestly
> misunderstood as efficacy of the lamp, since the datasheets mentioning
> those did say "luminous efficacy" - meaning the luminous efficacy of the
> emitted radiation, not the lamp. But sometimes my "hype detector" just
> starts buzzing!
>
> - Don Klipstein (d...@misty.com)
Indeed Agilent's persistent inclusion of a figure for the luminous
efficacy of the radiation in their led datasheets has earned them
respect with some users who see that other manufacturers cannot aproach
their figures! - the yellows in particular appear quite outstanding.
You would be surprised by who has been taken in by such bullsh**
because they have almost no comprehension of photometrics.
Asked for assistance by one company I was informed that they needed to
'electronically' change the color of a particular wavelength since they
had determined the optimum nm (nano-meters) from such datasheets but
could not find them in the correct color.
Much work had also been undertaken in waggling the leds on and off at
different frequencies to find the optimum (from memory around a few
hundred Hz!!).
Another once explained that a yellow lumen was the brightest color of
lumen -gleaned from the led datasheets- and long and short wavelength
lumens and millicandela were invisible.
RHRRC
Peter Pan wrote:
> Just some numbers:
> incandescent lamps are 10-20 lm/w
> cfl 40-80 lm/w
> leds are 15-25 lm/w
>
> you are stating that cfl are 10 times more efficient than incandescent
> (guess cfl would love this). 10*10 or 20-10 is not 40-80, first
> incongruity
>
> 10*30 or 20*30 is even more efficient than LPS lamps
>
> Have seen some cfl, claim to be several times more efficient than HPS!
> Maybe if you take into account the scotopic effect. Don't believe
> everything you read until you make some simple analysis.
>
> In article <1150310210....@y41g2000cwy.googlegroups.com>,
> RHRRC <h.l...@connect-2.co.uk> wrote:
>
> > By 1997 LEDs had already improved to the point
>> <snip>
> > I blame the price of oil, global warming, the Iraq war, George Bush,
> > the price of cheese, my dog Charlie, .......
> >
Ah yes but progress is indeed becoming more rapid.
In feb 2006 a Cree press release announced 'the industry's highest
efficacy white leds' at 350ma at 47lm/W. (i.e. leds you can buy rather
than 'laboratory samples have indicated efficacies)
By June 2006 a <nameless to avoid embarassment> lighting company
announced one of their range of luminaires, tested by an independant
laboratory, provides 80 lm/W -using Cree warm white leds - up from its
previous 73 lm/W
The 1000lm/W led is only hours away.
Victor Roberts
<davidlee...@dont.use.this.bit.hotmail.com> wrote:
>Victor Roberts wrote...
>>>By 1997 LEDs had already improved to the point of being three times
>>>more efficacious than compact flourescents and 30 (yes 30!) times more
>>>efficacious than 'standard' incandescents.
>>>
>>>see
>>>
>>>http://www.homepower.com/files/ledlight.pdf?search=led%20lighting
>>>
>>>How is it that we have gone backwards since then?
>>>
>>>I blame the price of oil, global warming, the Iraq war, George Bush,
>>>the price of cheese, my dog Charlie, .......
>>
>> The author states that his meter is only measuring the light
>> in a small area directly beneath the lamp, and then he adds
>> that ridiculous headline to the start of the article.
>
>There is also a common confusion about the meaning of "Efficiency" in LEDs.
>The QUANTUM efficiency of an LED is indeed close to 100%. However that
>simply means that every electron passing into the junction region will give
>rise to the emission of a photon of light - it says nothing about the amount
>of power dissipated in moving the electron around the circuit. So efficiency
>as optical-power-out divided by electrical-power-in is generally a much
>smaller value.
I don't think there is as much confusion here as there is
misrepresentation. LED supporters would like to think there
is something magical about LEDs. They don't discuss the
quantum efficiency of fluorescent lamps, which is about 70%,
or the fact that the radiation efficiency of many types of
incandescent lamps is virtually 100%. It just that most of
the radiation they generate is not visible to the human eye.
>Another problem is getting the light out of a semiconductor
die once it has
>been emitted - although this was much greater in the mid IR LEDs that we
>were developing because of the very high refractive index - resulting in a
>big hit in external efficiency. I don't think that it's a serious problem
>with optical wavelength materials.
Discharge lamps also have high "internal " efficiency if we
choose to forget about the problem of getting those darn
photons out of the lamp.
The only fair way to compare visible light sources is to
measure the radiant power that exits the device, weighted
and converted into lumens by the CIE Photopic Eye Response
curve, divided by the line plug power input. All these
other numbers are just smoke and mirrors.
Don Klipstein
It's often a major problem with visible wave length materials. Lumileds
managed a significant gain in "extraction efficiency" from InGaAlP dice
(presumably GaP substrate) by making the shape of the die a truncated
inverted pyramid instead of square.
In addition, I see quantum efficiency of visible LEDs usually varying
significantly with current. With white LEDs, the photon output / electron
throughput in my experience is often about 20% higher at some reduced
current than it is at "characterizing current" in my experience so far.
- Don Klipstein (d...@misty.com)
Peter Pan
However, I don't believe any of these numbers. LCR announced that they
expect 150 lm/W in about six years.
If these numbers were correct we would be seeing a massive move towards
leds in all fields. However, leds just became viable substitutes for
incandescent lamps by breaking the 20-25 lm/W. Guess we will start
seeing more leds being used in las vegas and such.
The IES handbook had a theoretical limit for lamp efficiencies, don't
recall whether 400 or 700 lm/W. Even when it was for discharge lamps,
don't think leds can get much beyond that. Of course unless quantum
physics have a weird way around that :)
In article <1150398403.3...@f6g2000cwb.googlegroups.com>,
David Lee
>>Another problem is getting the light out of a semiconductor die once it
>>has
>>been emitted - although this was much greater in the mid IR LEDs that we
>>were developing because of the very high refractive index - resulting in a
>>big hit in external efficiency. I don't think that it's a serious problem
>>with optical wavelength materials.
> It's often a major problem with visible wave length materials. Lumileds
> managed a significant gain in "extraction efficiency" from InGaAlP dice
> (presumably GaP substrate) by making the shape of the die a truncated
> inverted pyramid instead of square.
I remember another group in our organisation using a similar geometry to
improve light extraction from arrays of devices.
The usual trick with visible wave-length devices is embedding in a domed
refractive-index-matched plastic material to reduce the problems of total
internal reflection. It wasn't so easy to find an easily-handled material
matched to InAs that was transparent at 3.4microns. Suitably formulated
selenide glasses could probably do the trick but we didn't have the
facilities to handle them.
> In addition, I see quantum efficiency of visible LEDs usually varying
> significantly with current. With white LEDs, the photon output / electron
> throughput in my experience is often about 20% higher at some reduced
> current than it is at "characterizing current" in my experience so far.
Isn't this likely to be a heating effect? When optimizing the growth
parameters of LED wafers I used to use very simple "knife & fork"
constructed devices and always had to run them pulsed with low duty cycles
in order to keep the junction cool and prevent saturation of the L/I curve.
David
Victor Roberts
<pR_pMaV...@mac.com> wrote:
>For one I would love to have a led that has a >70 lm/W efficacy.
>However, I don't believe any of these numbers. LCR announced that they
>expect 150 lm/W in about six years.
>
>If these numbers were correct we would be seeing a massive move towards
>leds in all fields. However, leds just became viable substitutes for
>incandescent lamps by breaking the 20-25 lm/W. Guess we will start
>seeing more leds being used in las vegas and such.
>
>The IES handbook had a theoretical limit for lamp efficiencies, don't
>recall whether 400 or 700 lm/W. Even when it was for discharge lamps,
>don't think leds can get much beyond that. Of course unless quantum
>physics have a weird way around that :)
Monochromatic light with a wavelength of 555 nm has an
efficacy of 683 lmW based on the CIE Photopic Luminous
Efficiency Function. Light at all other wavelengths has
lower efficacy. These numbers cannot be changed except by
modifying the human eye or redefining the lumen.
400 lm/W is the efficacy of a hypothetical white light
source that has constant energy output over some wavelength
range which I do not remember exactly - perhaps 380 nm to
760 nm. Since the eye response is very weak at the edges of
this range, the 400 lm/W number can be moved up or down a
considerable amount by redefining the upper and/or lower
limits.
Don Klipstein
I thought this figure would be about half that...
I have handy the 1931 X-bar, Y-bar, and Z-bar functions in 5 nm steps
and their sums. The sum of Y-bar in 5 nm steps is 21.3174. The 1988
photopic function was not much of a change from Y-bar, which was defined
to be the 1924 photopic function. (I hope I got those years right!)
380 to 760 nm is 76 5-nm steps, so the sum over 76 means the photopic
function over that range has an average value of about .2805. Multiply by
683 lumens/watt, and this means 191.6 lumens/watt.
Try again for 400-700 nm, and the result is close to 208 lumens/watt -
slightly less with the "Y-bar sum" being slightly less than 21.3174 due to
Y-bar not being quite zero at 400 and 700 nm. (However, the sum of the
1988 photopic function in 5 nm steps will be slightly more than the same
for Y-bar.)
Let me try something else: I have this old BASIC program that tells me
some things of blackbody radiation as a function of color temperature.
One is theoretical lumens per watt, and another is percentage of output in
the 400-700 nm range.
I try a few color temperatures for dividing the first by the second and
get the following results for lumens per 400-700-nm-range watt for
blackbody radiation:
2000 K: 207
3000 K: 256
3400 K: 262
3600 K: 263
3800 K: 263
4100 K: 263
4500 K: 261
5000 K: 258
5500 K: 254
6500 K: 246
- Don Klipstein (d...@misty.com)
Don Klipstein
Not in the cases when the variation is significant over a range of
currents when the high end of the range I tried only warms the junction by
18 degrees C according to the datasheet.
- Don Klipstein (d...@misty.com)
David Lee
>>Isn't this likely to be a heating effect?
> Not in the cases when the variation is significant over a range of
> currents when the high end of the range I tried only warms the junction by
> 18 degrees C according to the datasheet.
"... lies, damned lies and datasheets" perhaps? ;-)
(with apologies to the late sir W S Churchill)
David
David Lee
>>>Isn't this likely to be a heating effect?
>> Not in the cases when the variation is significant over a range of
>> currents when the high end of the range I tried only warms the junction
>> by
>> 18 degrees C according to the datasheet.
> "... lies, damned lies and datasheets" perhaps? ;-)
... or less flippantly - an increase in non-radiative recombination with
increasing electric field. Impact ionization or Auger recombination perhaps
(depending upon material system)?
David
Victor Roberts
Don - I agree. 400 lm/W sounded high but I went ahead and
wrote my note anyway :-(
> I have handy the 1931 X-bar, Y-bar, and Z-bar functions in 5 nm steps
>and their sums. The sum of Y-bar in 5 nm steps is 21.3174. The 1988
>photopic function was not much of a change from Y-bar, which was defined
>to be the 1924 photopic function. (I hope I got those years right!)
>
> 380 to 760 nm is 76 5-nm steps, so the sum over 76 means the photopic
>function over that range has an average value of about .2805. Multiply by
>683 lumens/watt, and this means 191.6 lumens/watt.
I get 189.6 lm/W over the 380 to 760 nm range. It may be 76
steps, but I am summing 77 values so I divided the sum by 77
instead of 76. My data is also in 5 nm steps, but I'm not
sure which revision of the CIE data I have.
> Try again for 400-700 nm, and the result is close to 208 lumens/watt -
>slightly less with the "Y-bar sum" being slightly less than 21.3174 due to
>Y-bar not being quite zero at 400 and 700 nm. (However, the sum of the
>1988 photopic function in 5 nm steps will be slightly more than the same
>for Y-bar.)
I get 239.2 lm/W for 400 to 700 nm. This 60 steps and 61
values.
Boxman
> efficacy white leds' at 350ma at 47lm/W. (i.e. leds you can buy rather
> than 'laboratory samples have indicated efficacies)
>
> By June 2006 a <nameless to avoid embarassment> lighting company
> announced one of their range of luminaires, tested by an independant
> laboratory, provides 80 lm/W -using Cree warm white leds - up from its
> previous 73 lm/W
>
> The 1000lm/W led is only hours away.
Certainly some skepticism is warranted, but you left out relevant
facts. The company name you ommitted is LLF, which happens to be a
group of former high level Cree employees. My understanding is they
are essentially a spin off of Cree. They therefore probably have
access to the highest level of chip/package technology that exists
inside Cree whether Cree has brought it out of the lab or not. So it is
entirely possible that they have put together a luminaire with the
stated performance. They also stated that they don't intend to start
production until the end of this year and didn't make any statements
regarding whether a production version would achieve the 80 lm/W
measurable.
Honestly, if you are going to carp about LED manufacturers and LED
product manufacturers not being forthright in their own statements, you
can at least have the courtesy to do what you are asking them to do in
your own derision of their practices.
Peter Pan
when talking about light). Always thought that a lamp efficacy
considered already the eye's response (as is in the discussion of
scotopic vs photopic lumens). My field is much less theoretical, so
never thought of going deeper, besides most current lamps are about
100-130 lm/W. So that means that at most lamps could only improve by a
factor of 2.
Going back to the thread's theme, guess we will be lucky to see what
the LCR is expecting of 150 lm/W. From the recent discussion there are
many obstacles to be overcome first.
In article <slrne95d3...@manx.misty.com>, Don Klipstein
Victor Roberts
wrote:
I fail to see how RHRRC was any less forthright than LLF has
been. The statements he made are taken right from the LLF
press release of May 30. My understanding of this press
release is that the fixtures that will be available by the
end of this year will have an efficacy of 80 lm/W. See:
http://www.ledlightingfixtures.com/pr_053006.pdf
If LLF doesn't mean to imply that the products they will
have available by year end will have an efficacy of 80 lm/W
or something close to that, then perhaps they should state
that the fixture performance reported in the press release
is based on experimental or laboratory or special or rare or
hard to find or very expensive LEDs and does not represent
the performance of their initial product offerings.
We also have the small problem that Cree doesn't list any
LEDs with an efficacy even close to 80 lm/W. Since a
fixture for any type of lamp cannot reasonably be expected
to have higher efficacy than the source itself, some
explanation from LLF is certainly in order.
My own bias when evaluating new products is to first review
the data sheet and then find out if anyone has independently
validated the claimed performance. In this case LLF hasn't
even posted data sheets on their web site, only a string of
press releases. Makes me wonder if their real goal is to
sell products or to pump up the venture capital market.
RHRRC
Boxman wrote:
> > In feb 2006 a Cree press release announced 'the industry's highest
> > efficacy white leds' at 350ma at 47lm/W. (i.e. leds you can buy rather
> > than 'laboratory samples have indicated efficacies)
> >
> > By June 2006 a <nameless to avoid embarassment> lighting company
> > announced one of their range of luminaires, tested by an independant
> > laboratory, provides 80 lm/W -using Cree warm white leds - up from its
> > previous 73 lm/W
> >
> > The 1000lm/W led is only hours away.
>
> Certainly some skepticism is warranted, but you left out relevant
> facts. The company name you ommitted is LLF, which happens to be a
> group of former high level Cree employees. My understanding is they
> are essentially a spin off of Cree. They therefore probably have
> access to the highest level of chip/package technology that exists
> inside Cree whether Cree has brought it out of the lab or not. So it is
> entirely possible that they have put together a luminaire with the
> stated performance. They also stated that they don't intend to start
> production until the end of this year and didn't make any statements
> regarding whether a production version would achieve the 80 lm/W
> measurable.
>
I see.
These 'high level' ex employees need the services of an indepedant lab
to measure the output of a luminaire that they are not going to
manufacture but which uses sources about which they (presumably)
already have detailed photometric data.
WOW the results show a 10% increase over their 'record' set merely six
weeks previously.
They obviously cannot guarantee to keep their efficacies down to 80lm/W
by the end of the year (when production starts) with their current
exponential efficacy rate of rise.
> Honestly, if you are going to carp about LED manufacturers and LED
> product manufacturers not being forthright in their own statements, you
> can at least have the courtesy to do what you are asking them to do in
> your own derision of their practices.
I do not carp about the majority of the major LED maufacturers. Indeed
Cree (the led manufacturers) have been markedly responsible with their
claims and notably differentiate performance anouncements between
available product and laboratory.
Carefully worded press releases (including the inevitable reference
links to respected authorities) are purposefully placed to take
advantage of those with limited understading of the subject.
That I do carp about.
Boxman
> I see.
> These 'high level' ex employees need the services of an indepedant lab
The positions of the persons involved in Cree are referred to in this
particular newspost.
http://www.compoundsemiconductor.net/articles/news/10/5/8/1
I was simply pointing out that these aren't fly by night hucksters as
you seem to imply, or at the very least, I read into your post, who
know nothing about LEDs and their performance.
Secondly, measuring the output of a Luminaire is significantly
different than measuring the performance of a single LED. The optical
system of the luminaire would significantly impact the performance of
the LED system as a whole with regards to a specific function. Nearly
every LED manufacturer I've dealt with doesn't maintain the type C
goniometer equipment in their labs that would be required to test
physical luminaires.
I'm not saying whether their claims are true or not, but you used
tongue in cheek language in you original post, implying that they were
making embarassing claims, and subsequently chose to omit other
information about them that might refute your position. If they made
claims to independent data, and if you want to refute that claim you
should provide either evidence to the contrary or at least try to
obtain the data and indicate that it was refused to you to provide some
credence to your implications.
I'm sure I'm coming across as a a jerk, but I don't intend to. Just
trying to get all the facts into the discussion. Thanks anyway.
Boxman
> If LLF doesn't mean to imply that the products they will
> have available by year end will have an efficacy of 80 lm/W
> or something close to that, then perhaps they should state
> that the fixture performance reported in the press release
> is based on experimental or laboratory or special or rare or
> hard to find or very expensive LEDs and does not represent
> the performance of their initial product offerings.
>
> We also have the small problem that Cree doesn't list any
> LEDs with an efficacy even close to 80 lm/W. Since a
> fixture for any type of lamp cannot reasonably be expected
> to have higher efficacy than the source itself, some
> explanation from LLF is certainly in order.
>
appropriate to explicitly call the fixture out as a prototype or
laboratory mockup. I was just objecting to the pre-filtering done in
the previous post where the poster omitted relevant details and drew
the conclusion for the newsgroup on his own, essentially telling people
they were an embarassment without having even tried to obtain the data
or information.
Victor Roberts
wrote:
>
>> I see.
>> These 'high level' ex employees need the services of an indepedant lab
>
>The positions of the persons involved in Cree are referred to in this
>particular newspost.
>http://www.compoundsemiconductor.net/articles/news/10/5/8/1
>
>I was simply pointing out that these aren't fly by night hucksters as
>you seem to imply, or at the very least, I read into your post, who
>know nothing about LEDs and their performance.
I don't believe that the OP implied that LLF knew nothing
about LEDs. In fact, their press releases indicate that they
are highly skilled in the art of selling LEDs.
>Secondly, measuring the output of a Luminaire is significantly
>different than measuring the performance of a single LED. The optical
>system of the luminaire would significantly impact the performance of
>the LED system as a whole with regards to a specific function. Nearly
>every LED manufacturer I've dealt with doesn't maintain the type C
>goniometer equipment in their labs that would be required to test
>physical luminaires.
The LLF press release states fixture performance only in
lumens, watts and then lm/W. They do not provide any data
that would need a goniometer. As I stated before it is
virtually impossible for a fixture to have higher overall
efficacy that the light sources used in that fixture. The
only exception I can think of would be some strange
application where the environment of the fixture might be
better than the standard test conditions for the source. For
example, if the fixture operated LEDs at the temperature of
liquid nitrogen, while the standard catalog data was
generated for a junction temperature of 25 C.
Don't you think its a bit strange that Cree, who has
apparently gone to great pains to distinguish between the
performance of LEDs that are available for sale and some LED
that might have demonstrated great performance in the their
laboratory, now gives these rare laboratory-grade LEDs to
another company - even if staffed by former employees of
Cree - and lets THEM misrepresent the data to the public?
If and when we do get a fixture that delivers 80 lm/W, it
will be a testament to the people who developed the LEDs,
not those who mounted them in a metal box and attached a
power supply.
Now - to be fair to LLF - there is one way in which they
could build a "white" LED fixture that has higher efficacy
than the best available while LEDs. That would be by
combining high performance monochromatic LEDs to produce
white light and avoiding the Stokes Shift energy loss of the
phosphor used on white LEDs. Since they are selling a group
of LEDs mounted in a fixture they could indeed make a white
light fixture that has higher efficacy than the best single
white LED. I will need to look again at the Cree data for
their monochromatic LEDs and see if some combination would
produce white light with an efficacy even near 80 lm/W.
>I'm not saying whether their claims are true or not, but you used
>tongue in cheek language in you original post, implying that they were
>making embarassing claims, and subsequently chose to omit other
>information about them that might refute your position.
What information did he omit????
>If they made
>claims to independent data, and if you want to refute that claim you
>should provide either evidence to the contrary or at least try to
>obtain the data and indicate that it was refused to you to provide some
>credence to your implications.
Their claims of independent data are also a bit strange. The
press release states that the fixture efficacy was measured
by a laboratory accredited by OSHA. Please show me any OSHA
regulation that deals with the lumen output of lamps. How
does OSHA accreditation give this lab any credibility for
measuring light sources? The lab mentioned in the press
release may be a high quality organization and they may
indeed know how to measure lumens, but I doubt it is because
they have OSHA accreditation.
Don Klipstein
having to do with lumens in 1 watt of "white" light:
> 380 to 760 nm <SNIP my methodology> 191.6 lumens/watt.
>
> Try again for 400-700 nm, and the result is close to 208 lumens/watt
I found error implementing my methodology - make that 242.7
These are for "equal energy white", or equal power per unit wavelength,
CCT approx. 5400K and slightly purpler than blackbody.
>results for lumens per 400-700-nm-range watt for blackbody radiation:
>
>2000 K: 207
>3000 K: 256
>3400 K: 262
>3600 K: 263
>3800 K: 263
>4100 K: 263
>4500 K: 261
>5000 K: 258
>5500 K: 254
>6500 K: 246
While I am at it, I am in a good mood to calculate theoretical
lumens/watt for "trichromatic white" of a couple favorable CCTs
(4100 and 3500 Kelvin).
Red primary - 611 nm, the wavelength of the main red-orange/orange-red
emission from triphosphor fluorescent lamps.
Green primary - 544 nm, approx. dominant wavelength of composite of
green mercury line and emission of a common green phosphor in triphosphor
fluorescent lamps.
Blue primary - 450 nm, the multiple of 10 nm that has highest response
of human blue receptors.
To get 1 watt of 4100K from this:
.3711 watt 611 nm - 114.92 lumens
.4136 watt 544 nm - 275.71 lumens
.2153 watt 450 nm - 6.88 lumens
Total 1 watt = 397.5 lumens
To get 1 watt of 3500K from this:
.4155 watt 611 nm - 128.67 lumens
.4003 watt 544 nm - 266.84 lumens
.1842 watt 450 nm - 5.89 lumens
Total 1 watt = 401.4 lumens
Dichromatic whites made by mixing 450 nm with a yellow wavelength can
achieve a little more still, although color rendering index would be worse
than the 20 of an unphosphored high pressure mercury lamp:
4100K:
To nearest 1 nm, use 573 nm as choice to mix with 450 nm.
.739 watt 573 nm (470 lumens) plus .261 watt 450 nm (8.34 lumens)
totals 1 watt with 478 lumens.
3500 K:
To nearest 1 nm, use 576 nm as choice to mix with 450 nm.
.788 watt 576 nm (488 lumens) plus .212 watt 450 nm (6.8 lumens)
totals 1 watt with nearly 495 lumens.
- Don Klipstein (d...@misty.com)
RHRRC
Boxman wrote:
We all have plenty to learn.
Two pieces of advice for you
1. keep errors to those of emission
2. when stuck in the bottom of a hole stop digging
Good luck with your venture.
redbelly
Victor Roberts wrote:
> I get 189.6 lm/W over the 380 to 760 nm range. It may be 76
> steps, but I am summing 77 values so I divided the sum by 77
> instead of 76. My data is also in 5 nm steps, but I'm not
> sure which revision of the CIE data I have.
Victor,
If you're going for a proper account of things, why not weight the end
values (at 380 and 760) by half as much? Then divide the sum by 76.
Regards,
Mark
redbelly
Peter Pan wrote:
> Just some numbers:
> incandescent lamps are 10-20 lm/w
> cfl 40-80 lm/w
> leds are 15-25 lm/w
Just some thoughts on those numbers:
You need current regulation for an LED, which brings down the overall
efficacy. Not required for incandescents or cfl+ballast.
If, for example, a 20 lm/W LED becomes 15 lm/W after adding a current
regulator, then it doesn't beat a household incandescent bulb (15
lm/W).
The LED does beat a few-Volt flashlight incandescent (around 10 lm/W),
with fewer/zero bulb changes thrown in as a bonus.
Mark
Victor Roberts
<redbe...@yahoo.com> wrote:
First, I don't see why this is more correct. If a sum
includes 77 values then the average is the sum divided by
77. In addition, there are so few lumens per watt at 380
and 760 nm that the results using your method would be
equivalent to dividing the full sum by 76.
Using your method I get 192.059 lm/W.
Using the 380 to 760 divided by 76 I get 192.060 lm/W.
Victor Roberts
<redbe...@yahoo.com> wrote:
>
>Peter Pan wrote:
>> Just some numbers:
>> incandescent lamps are 10-20 lm/w
>> cfl 40-80 lm/w
>> leds are 15-25 lm/w
>
>Just some thoughts on those numbers:
>
>You need current regulation for an LED, which brings down the overall
>efficacy. Not required for incandescents or cfl+ballast.
>
>If, for example, a 20 lm/W LED becomes 15 lm/W after adding a current
>regulator, then it doesn't beat a household incandescent bulb (15
>lm/W).
You're assuming a current regulator with an efficiency of
only 75%. There is no reason why a good LED current
regulator cannot have an efficiency of 90% or more, which is
similar to that of high quality electronic ballasts.
redbelly
Victor Roberts wrote:
> On 17 Jun 2006 08:22:21 -0700, "redbelly"
> <redbe...@yahoo.com> wrote:
>
> >
> >Peter Pan wrote:
> >> Just some numbers:
> >> incandescent lamps are 10-20 lm/w
> >> cfl 40-80 lm/w
> >> leds are 15-25 lm/w
> >
> >Just some thoughts on those numbers:
> >
> >You need current regulation for an LED, which brings down the overall
> >efficacy. Not required for incandescents or cfl+ballast.
> >
> >If, for example, a 20 lm/W LED becomes 15 lm/W after adding a current
> >regulator, then it doesn't beat a household incandescent bulb (15
> >lm/W).
>
> You're assuming a current regulator with an efficiency of
> only 75%. There is no reason why a good LED current
> regulator cannot have an efficiency of 90% or more, which is
> similar to that of high quality electronic ballasts.
Vic,
The ones I've seen have roughly a 1V drop. If you run a single white
LED (3.5 V) with that, that gives a 78% efficiency. Do you know of
regulators with smaller voltage drops, or are you thinking in terms of
running strings of LED's on a single regulator?
Regards,
Mark
redbelly
Victor Roberts wrote:
> On 17 Jun 2006 08:08:25 -0700, "redbelly"
> <redbe...@yahoo.com> wrote:
>
> >
> >Victor Roberts wrote:
> >
> >> I get 189.6 lm/W over the 380 to 760 nm range. It may be 76
> >> steps, but I am summing 77 values so I divided the sum by 77
> >> instead of 76. My data is also in 5 nm steps, but I'm not
> >> sure which revision of the CIE data I have.
> >
> >Victor,
> >
> >If you're going for a proper account of things, why not weight the end
> >values (at 380 and 760) by half as much? Then divide the sum by 76.
> >
> >Regards,
> >
> >Mark
>
> First, I don't see why this is more correct. If a sum
> includes 77 values then the average is the sum divided by
> 77. In addition, there are so few lumens per watt at 380
> and 760 nm that the results using your method would be
> equivalent to dividing the full sum by 76.
>
> Using your method I get 192.059 lm/W.
>
> Using the 380 to 760 divided by 76 I get 192.060 lm/W.
>
Well, like you said, it's not a big difference in this case. But using
1/2-weighting at the endpoints is equivalent to approximating an
integral with the trapezoid rule. See the last equation at this
(short) URL:
http://en.wikipedia.org/wiki/Trapezoidal_rule
Divide the integral by the wavelength range of that integral, and you
have the average.
Mark
Peter Pan
where these show higher efficiency than the actual fixture CU. Guess
some of the led's crazy values might go with a similar logic.
A led puts out all its flux in a limited solid angle, Then to achieve a
similar illumination in the same angle by an incandescent lamp, you
need an equivalent incandescent lamp of so many lumens (of course
ignoring all the light that doesn't go in the cone of light put out by
the led). Therefor those lumens divided by the led power could give
those crazy numbers.
The other option is as several have been mentioning, that those led
makers are considering all the energy the naked led might be producing
throughout its spectrum (with no correction for the eye sensitivity).
Guess that if you follow this logic, and incandescent lamp could
achieve impressive numbers (though most output is IR!).
In article <nk96929fibrns4hbi...@4ax.com>, Victor Roberts
Boxman
> apparently gone to great pains to distinguish between the
> performance of LEDs that are available for sale and some LED
> that might have demonstrated great performance in the their
> laboratory, now gives these rare laboratory-grade LEDs to
> another company - even if staffed by former employees of
> Cree - and lets THEM misrepresent the data to the public?
No I don't find it strange. Several times when developing LED lamps
for automotive exterior lighting applications, I have had access to
physical samples from the LED manufacturer that were 2 or 3 times the
output of the currently available LEDS that were currently released and
documented. They gave them to us to help is in our product development
cycle knowing that there would be a several month lag between getting
first prototypes and actually going into full production. And yes, we
would be at the automotive OEMs showing them higher output LEDs than
what they could buy on the market. If you have read the papers
published in some of the societies such as SPIE, then you've seen
published performance of LED headlamp designs using LEDs at levels that
were not "documented and released" at the time, so I don't see it as
being that uncommon to have someone showing performance for an LED to
the public that isn't currently available for purchase from the LED
supplier. I don't live around the Detroit area anymore, but I believe
the last I heard Visteon was aggressively marketing their LED headlamp
capability around the Detroit area using billboards, and my
understanding is that some of their performance data was with
"non-commercially" available LEDs at the time as well.
It seemed to me that it is a good way for the LED manufacturers to plan
their reactor capacity and help move their efficacy along based on a
known financial return for making the higher outputs available rather
than continuing to try and sell at the current outputs and tying up
their reactors at the lower level formulations if there are ready
markets for higher outputs.
That's also been one of the issues with using LEDs in automotive is
that the 10 year (I think it's 10 years) service cycle required for
providing service lamps poses an issue for the LEDs if they obsolete
lower output models during that cycle that are needed to keep the lamp
legal (lamp has to meet both minimums and maximum specifications).
Boxman
Peter Pan wrote:
> One of thosevalue that sound fishy, though correct are the ZCR tables
> where these show higher efficiency than the actual fixture CU. Guess
> some of the led's crazy values might go with a similar logic.
>
> A led puts out all its flux in a limited solid angle, Then to achieve a
> similar illumination in the same angle by an incandescent lamp, you
> need an equivalent incandescent lamp of so many lumens (of course
> ignoring all the light that doesn't go in the cone of light put out by
> the led). Therefor those lumens divided by the led power could give
> those crazy numbers.
>
claim even with the lower output. The specific application here was a
downlight, where the LEDs have the advantage of only emitting in the
downard direction, and so if you compare to a bulb that could send half
of it's flux upward to either be lost, diffusely reflected in no
particular direction, or reflected by a designed reflector that absorbs
some light with the reflection, then you could get the same output in
the downlight application region from the LEDs as a higher output
incandescent and make the lumen/watt claim on the equivalent
incandescent bulb needed to get the same ouptut pattern. Sneaky....
mrob...@worldnet.att.net
>That's also been one of the issues with using LEDs in automotive is
>that the 10 year (I think it's 10 years) service cycle required for
>providing service lamps poses an issue for the LEDs if they obsolete
>lower output models during that cycle that are needed to keep the lamp
>legal (lamp has to meet both minimums and maximum specifications).
Would it be possible to stay legal by offering as a service part a newer,
higher output LED with integral resistor/regulator to reduce its output?
Or would that require an expensive recertification of the entire LED-
reflector-lens assembly?
Matt Roberds
Victor Roberts
wrote:
Since an LED is inherently directional I agree that the
efficacy of an LED in a fixture can be equal to the efficacy
of the "bare" LED - while the efficacy of a fixture using
incandescent, fluorescent or HID sources will always be
lower than the efficacy of the bare lamp due to fixture
losses.
However, this argument does not explain how an LED in a
fixture can have higher efficacy than that same LED when
measured without the fixture - unless of course the fixture
manufacturer is making up his own definitions of efficacy.
Boxman
> higher output LED with integral resistor/regulator to reduce its output?
> Or would that require an expensive recertification of the entire LED-
> reflector-lens assembly?
>
> Matt Roberds
It's primarily left to the lamp manufacturer, but if they are a
supplier to just about any automobile manufacturer then their quality
system requirements would require them to test and recertify the whole
lamp if they changed the design. It's a trade off, in some cases a
mid stream retrofit that you describe might be cheaper over the long
run even if you add in the cost of extra testing as opposed to paying
more up front on every part for a supply design that can be tweaked
later without a design change.
Victor Roberts
<redbe...@yahoo.com> wrote:
Mark - I agree that many current LED systems use terrible
current regulators. I also agree that providing a high
efficacy driver for a single LED is a challenge due to the
low voltage drop. However, I expect that any commercial LED
system would use multiple LEDs wired at least partially in
series to increase the load voltage and the driver used
would have an efficacy at least as good as current
electronic fluorescent lamp ballasts. Large-scale systems
can't afford to throw away 25% of the power if they hope to
compete as energy efficient light sources.
Boxman
> However, this argument does not explain how an LED in a
> fixture can have higher efficacy than that same LED when
> measured without the fixture - unless of course the fixture
> manufacturer is making up his own definitions of efficacy.
The only other thing I can think of besides them having higher output
dies than commercially avialable is if they are using only the raw chip
and using their own extractor designs to get better performance for a
specific task. Cree publishes the performance of a full LED package
(chip, optical components, and mechanical package), not the stand alone
die chip performance.
Some companies specialize in developing non imaging optical devices
directly coupled to the chip that can give higher efficacies for
specific tasks than the fully packaged LED efficiency because they can
use a better matched index gels with the chip and advanced optical
design techniques to optimize the efficiency of light extraction and
transfer to the usable output field. If I am remebering correctly,
this has been discussed in published papers regarding automotive
headlamp design concepts with LEDS and showed real improvements over
using the LED manufacturers stock package design.
The most succesful implementers of LED technology will not just be
buying stock LEDs and throwing them in a box. They'll need to
implement the LED technology with well designed thermal management
techniques, and well engineered optics to optimize the light extraction
and distribution. In my opinion, they are the ones who will eventually
lead the field. The exterior automotive lighting equipment field has
been doing this for over 15 years with high brightness LEDs, and LEDs
are beginning to get bright enough now for people to consider general
lighting applications as well. I'm guessing the same cycle of
development will need to occur in the general lighting field as well.
Optical design and Thermal management are key technologies that aren't
necessarily available to everyone manufacturing luminaires, so the
larger manufacturers may have some advantage in this respect. But who
knows maybe somebody like LLF is putting it all together and getting it
right.
Paul Hovnanian P.E.
First, run series strings of LEDs with one regulator. Second, use a
switch mode regulation topology. Unlike a resistive or linear regulators
(which incurs an energy loss in the series element), these can operate
above 90% efficiency easily.
--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
Opinions stated herein are the sole property of the author. Standard
disclaimers apply. Celebrity voice impersonated. Batteries not included.
Limit one to a customer. Best if used by April 1, 2006. Refrigerate
after opening. Void if removed.
Don Klipstein
>On 17 Jun 2006 08:08:25 -0700, "redbelly"
><redbe...@yahoo.com> wrote:
>
>>Victor Roberts wrote:
>>
>>> I get 189.6 lm/W over the 380 to 760 nm range. It may be 76
>>> steps, but I am summing 77 values so I divided the sum by 77
>>> instead of 76. My data is also in 5 nm steps, but I'm not
>>> sure which revision of the CIE data I have.
>>
>>values (at 380 and 760) by half as much? Then divide the sum by 76.
>
>includes 77 values then the average is the sum divided by 77.
If dividing by 77, then I would consider that (189.6 lm/W) to be the
value represented by 77 5-nm wide bands - which would be for the 377.5 to
762.5 nm stretch.
> In addition, there are so few lumens per watt at 380
>and 760 nm that the results using your method would be
>equivalent to dividing the full sum by 76.
>
>Using your method I get 192.059 lm/W.
>
>Using the 380 to 760 divided by 76 I get 192.060 lm/W.
I agree with these - both reasonably valid and apparently to me
adequately obvious to be approximations and agreeing well with each
other.
If you want fun with some hard-to-achieve ideal, how about a radiator
that is 100% efficient and equal-energy-per-unit-bandwidth from 422.5 nm
to 692.5 nm and radiating nothing outside that range?
I get 1931 chromaticity coordinates from that x=.3381, y=.3426, which is
maybe 1/8-1/4 of a fine red hair purpler than roughly 5270 Kelvin but to a
much greater extent (still very slight) yellow-greenish compared to "equal
energy white". And I would guess the CRI of this "ideal" of mine to be
about 99.
And Y-bar sum (using 5 nm steps) is 21.2889, divide by 55 for average
value of .387071, multiply by 683 to get 264.4 lumens/watt by the 1924
photopic function, and I would guess probably between 264.5 and 265
lumens/watt by the 1988 photopic function.
- Don Klipstein (d...@misty.com)
Don Klipstein
>
>Peter Pan wrote:
>> Just some numbers:
>> incandescent lamps are 10-20 lm/w
>> cfl 40-80 lm/w
>> leds are 15-25 lm/w
>
>Just some thoughts on those numbers:
>
>You need current regulation for an LED, which brings down the overall
>efficacy. Not required for incandescents or cfl+ballast.
There are inductive switching current regulators that have losses
comparable to that of other "ballasts".
>If, for example, a 20 lm/W LED becomes 15 lm/W after adding a current
>regulator, then it doesn't beat a household incandescent bulb (15
>lm/W).
I would say derate 20 to 18, 25 to 22.5, and keep in mind that LEDs with
overall luminous efficacy in the mid-upper 30's (typically, with minimum
at least mid-20's) are now reasonably available and better than this is
soon to come or maybe already landing.
>The LED does beat a few-Volt flashlight incandescent (around 10 lm/W),
>with fewer/zero bulb changes thrown in as a bonus.
Along with efficacy not decreasing significantly as the battery weakens,
compared to incandescent flashlight lamps having luminous efficacy roughly
proportional to battery voltage raised to a power of at least 1.5, maybe
closer to 2.
- Don Klipstein (d...@misty.com)
Don Klipstein
>
>Victor Roberts wrote:
>> On 17 Jun 2006 08:22:21 -0700, "redbelly"
>> <redbe...@yahoo.com> wrote:
>>
>> >You need current regulation for an LED, which brings down the overall
>> >efficacy. Not required for incandescents or cfl+ballast.
>> >
>> >If, for example, a 20 lm/W LED becomes 15 lm/W after adding a current
>> >regulator, then it doesn't beat a household incandescent bulb (15
>> >lm/W).
>>
>> You're assuming a current regulator with an efficiency of
>> only 75%. There is no reason why a good LED current
>> regulator cannot have an efficiency of 90% or more, which is
>> similar to that of high quality electronic ballasts.
>
>LED (3.5 V) with that, that gives a 78% efficiency. Do you know of
>regulators with smaller voltage drops, or are you thinking in terms of
>running strings of LED's on a single regulator?
I know of such circuits having voltage drop more like half a volt.
Consider inductive switching ones using power MOSFETs and "catch diodes"
being Schottky diodes. Along with the obvious design parameter of higher
battery voltages.
I would say that 85% efficiency of "an LED ballast" is low end of
someone trying to work at that and shaving costs by so severely as 1/10ths
of a cent, and 90% is fairly easily achievable without great cost.
- Don Klipstein (d...@misty.com)
Don Klipstein
As efficient as they make downlight optics designed for incandescents
(whether in the fixture or in the lamp [bulb]), the really outrageous LED
efficacy claims in comparison to incandescents are ignoring highly
commonly available incandescent downlights that are reasonably designed
for such duty!
- Don Klipstein (d...@misty.com)
Don Klipstein
>
>> However, this argument does not explain how an LED in a
>> fixture can have higher efficacy than that same LED when
>> measured without the fixture - unless of course the fixture
>> manufacturer is making up his own definitions of efficacy.
>
>The only other thing I can think of besides them having higher output
>dies than commercially avialable is if they are using only the raw chip
>and using their own extractor designs to get better performance for a
>specific task. Cree publishes the performance of a full LED package
>(chip, optical components, and mechanical package), not the stand alone
>die chip performance.
Please tell us where I can see this!
- Don Klipstein (d...@misty.com)
Boxman
> (whether in the fixture or in the lamp [bulb]), the really outrageous LED
> efficacy claims in comparison to incandescents are ignoring highly
> commonly available incandescent downlights that are reasonably designed
> for such duty!
>
> - Don Klipstein (d...@misty.com)
I'm not sure what you meant on your other reply to my other post. If
you wanted to see papers on using extractors to increase the efficiency
of a chip on board design as opposed to using the standard LED
packaging, there is one in the SPIE proceedings on Illumination design
from last August if I remember correctly. I beleive it is this one but
I could be wrong:
http://bookstore.spie.org/index.cfm?fuseaction=detailpaper&cachedsearch=1
&productid=624658&producttype=pdf&CFID=1537183&CFTOKEN=55541604
In the paper they were developing an LED headlamp optic and the
effciency of the light extractor (not the whole system) relative to
the published LED performance was over 100% because they put the optic
and index matching gel directly to the chip and improved the extraction
for the beam pattern they were attempting to form as opposed to putting
optics onto the standard package which already has a pre-formed lens on
it. Whether it's practical in mass production, I don't know.
The reason LEDs might offer an advantage over standard incandescent's
in terms of an optical efficiency in a downlighting situation is if you
consider downlights that have spot angles in the range of 10 degrees to
say 60 degrees wide. Then the souce size of the LED provides a
significant advantage in terms of being able to transfer the flux into
a usable beam. The law of conservation of etendue describes the
fundament limit on how much flux you can transfer when you have a given
source size and a given solid angle that you are projecting into. The
LED source size for a single chip approaches a 1 mm square in some
cases. Most standard incandescent filaments are very large compared to
that. In some cases the incandescent filament is so large that even at
reasonable lamp openings the etendue condition restricts the transfer
efficiency into the beam spot.
The reason you see most narrow angle T-5 LEDs having a beam angle of
around 4 degrees is that etendue doesn't allow it to be any smaller
than that. If you run the etendue calculations with the lens size of
the T-5 package and the chip size in the package, you'll find this
limit. When you have an extended source and a specific lens size, you
can't do anything to the shape that will get you anything better than
what the conservation of etendue specifies.
Secondly, the LED can use direct coupling and total internal reflection
devices to avoid the reflectivity losses that the incandescent sources
will undergo when they use reflectors. A typical metallized glass bulb
reflector loses around 15% at the reflection interface. A TIR device
has 100% reflectivity because total internal reflection is 100%
efficient.
Thus it is conceivable that an LED downlight will use less lumens to
get the same resulting output in the beam when compared to an
incandescent.
Peter Pan
difficult to obtain high efficiencies for small power designs.
It is true that working at low voltages cause added complications.
However, most of the circuit could be working at a much higher voltage,
and the output be at the required voltage (remember 5V computer ps).
Depending on the topology they could have a flyback or buck design.
Nonetheless, it wouldn't be uncommon for efficiencies greater than 90%.
In article <slrne99mg...@manx.misty.com>, Don Klipstein
Victor Roberts
wrote:
>Thus it is conceivable that an LED downlight will use less lumens to
>get the same resulting output in the beam when compared to an
>incandescent.
This last part is correct (if you mean "source" lumens) for
any small source and will certainly be true for LEDs, but it
does not explain how the total lumen output of an LED-based
fixture can be higher than the output of the LEDs
themselves, measured in lumens.
Adam Aglionby
Could it be that LLF are looking to corner the market for downlights in
domestic freezers? ;-)
Adam
Victor Roberts
wrote:
>
If LLF has developed new technology to extract light from
LED chips, and if they are already showing products to
selected customers and plan to offer them for sale by the
end of the year I would think they would want to protect
their technology with one or more US patents. I therefore
ran a quick search this morning at www.uspto.gov. I could
not find any issued US patents or published applications
assigned to "LED Lighting Fixtures". I also searched under
"Morrisville" as the city of the assignee. That search
produced over 149 issued patents and 28 published
applications (not all the all from Morrisville, NC). Based
on a quick scan of the tiles only one patent was related to
LEDs and that one related to circuitry and is assigned to
Semtech. None of the published applications were
LED-related. There may still be some applications in the
pipeline since they can take some time to show up. (One of
my own filed about 6 weeks ago is not yet listed.)
I have a professional interest in determining whether or not
the claims made by LLF are real and more importantly, if
they are real how was this performance achieved. Even so, I
think I have discussed this subject to death, and will try
to move on to other matters :-)
RHRRC
> One of thosevalue that sound fishy, though correct are the ZCR tables
> where these show higher efficiency than the actual fixture CU. Guess
> some of the led's crazy values might go with a similar logic.
>
> A led puts out all its flux in a limited solid angle, Then to achieve a
> similar illumination in the same angle by an incandescent lamp, you
> need an equivalent incandescent lamp of so many lumens (of course
> ignoring all the light that doesn't go in the cone of light put out by
> the led). Therefor those lumens divided by the led power could give
> those crazy numbers.
I think there is a misundrestanding here of what a lumen is.
An efficacy of X lm/W (lumen per watt) has nothing to do with the polar
response of the source. No matter how much you play around with the
optics the efficacy with a given source remains the same
Moreover the most popular leds for lighting purposes (typically upwards
of 1W) do not have a particularly small theta's and require optical
management to match, for example, the polar respose of the more common
MR16 downlighters.
Boxman
> If LLF has developed new technology to extract light from
> LED chips
I'm not certain that that was what LLF was using I was only
speculating. And I doubt LLF has any of those patents as you have
confirmed by your search so if they were using it they would be
partnering with somebody who has done it before. Most of the optical
extraction techniques I've been referring to have been patented by a
company called LPI,
http://www.lpi-llc.com/company/company.html
which consists of the recognized experts in non imaging optics. If
you do a patent search and patent application search on Minano, Benitez
or Falicoff for patent author you should find several LED optic related
patents which describe various techniques for high efficiency transfer
including the possibility to get higher extraction from the chip for a
specific purpose using index gels and free-form optical shapes.
>
> I have a professional interest in determining whether or not
> the claims made by LLF are real and more importantly, if
> they are real how was this performance achieved. Even so, I
> think I have discussed this subject to death, and will try
> to move on to other matters :-)
I found this in the CREE press room from septemeber of last year
(thanks to the link on Don Klipstein's site)
DURHAM, NC, SEPTEMBER 2, 2005 - Cree, Inc. (NASDAQ: CREE), a leader
in high brightness LED solid-state lighting components, today announced
breakthrough performance results achieved in development of Cree
Lighting's standard white XLamp™ 7090 Power LED. XLamp 7090 LEDs in
development have demonstrated maximum luminous flux of 86 lumens and 70
lumens per watt at 350 mA. This represents a 43 percent increase in
brightness compared with the maximum luminous flux of white XLamp 7090
power LEDs currently in production.
Maybe it doesn't seem all that inconceivable that they are up to more
than 80 lumens/watt by this point in time.
I also saw in an earlier press release that the lumen output
measurement from LLF is from a 6" luminaire measured inside an
integrating sphere at thermal equilibrium.
redbelly
learn new stuff.
Regards,
Mark
Peter Pan
redbelly <redbe...@yahoo.com> wrote:
> Thank you for the replies Victor, Paul, Don and Peter (not me, otherwise strike it out). Always happy to
> learn new stuff.
>
Ibid, thanks guys