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News and links! UPDATE 4/14/2012
General Notes and Disclaimers
Pure Red / Deep Red LEDs
- 14 to 20-22 lumens/watt
Orangish Red LEDs - 46-96
lumens/watt
Red-Orange LEDs - 66-123
lumens/watt
Truly Orange LEDs - 18-22
lumens/watt
Yellow and "amber" LEDs -
34-63 lumens/watt, with a way for 50-100 for less-amberish yellow.
Yellow-Green LEDs - 8
lumens/watt, but there is a way to get 80.
Green LEDs - 61-100
lumens/watt.
Better InGaN green LEDs get 90-120-140 lumens/watt at 1.7-3
milliamps
Blue-Green LEDs - 57-74
lumens/watt
Blue LEDs - 24-33
lumens/watt
White LEDs - 55-170
lumens/watt
Warm White LEDs - up to 150
lumens/watt
Increased Efficiency of InGaN LEDs at lower currents
Important Notes on Gallium Nitride and InGaN LEDs!
LEDs with high candela "beam candlepower" figures
LEDs with high total lumen output
Notes on Where To Get Efficient LEDs
Converting / comparing lumens, candelas, millicandelas
UPDATE 3/18/2012 this 2/27/2012 Cree
press release:
Cree announced 276 lumens/watt at 350 mA. I did not see mention in this
press release of die size, as in whether it was a roughly 1 mm square or
larger. Correlated color temperature was mentioned - 4401 K.
UPDATE 9/15/2010 - Nichia is mentioned by this LEDs Magazine 9/6/2010 news
item to have achieved:
* 135 lumens/watt at 1 amp through an LED lamp having four 1x1 mm dice
in series, 1,913 lumens from approx. 14.2 watts. The color temp. was
mentioned as 4700 K.
* 183 lumens/watt at 350 mA in a lamp with a 1 x 1 mm chip. (added 8/11/2011)
* A 4600 K LED lamp with a .45 x .45 mm die (larger than the usual
generally roughly .3 x .3 mm die in most low power LED lamps) achieving
250 lumens/watt at 20 mA.
The above article mentions that manufacturing techniques necessary to achieve
such efficiency are costly, and that Nichia is not prioritizing getting
such efficient LEDs onto the market if they are dispropotionately
expensive for their light output.
Cree is mentioned in the above link in the "Comments" as providing
production samples of XM LED lamps that achieve 135 lumens/watt at 1 amp,
but I suspect the die size is larger in those.
UPDATE 5/14/2010 - Cree announced in this 5/10/2010
press release a 2 by 4 foot LED light fixture (LED luminaire) that
achieves 100-plus lumen/watt overall luminous efficacy from AC line voltage
electrical input to light exiting the luminaire. Cree's LR24HE achieves this
even with color temperature of 3500 K and color rendering index of 90.
UPDATE 11/28/2009 - 3M achieved a green LED achieving 181 lm/W at
350 mA by combining a green-emitting phosphor with an available blue LED
chip. This is mentioned in
this 11/23/2009 item in LEDs Magazine.
UPDATE 11/2/2004 - WITH THANKS TO FANS OF THIS WEBSITE:
In August 2004, Osram announced a prototype of an orange-red LED that
achieved 108 lumens/watt, producing over 2 lumens at 10 mA with a voltage
drop presumably of about 2 volts.
Look in This Osram
Press Release.
IMPORTANT NOTE Some laboratory prototypes mentioned above are not yet in
production even if years old! Barriers apparently include but may not be limited
to patents held by competitors, also cost of production with materials and
processes used to achieve higher efficiency. Also, gallium nitride based LED
chips just may not be cheap (substrate material is generally about 9 on the
Moh's hardness scale where diamond is 10). Production of chips of size favoring
a more optimum lower current density may price such things out of the market or
increase the size of optics needed to control where the light goes, more than
improve efficiency.
Some brands mentioned here as achieving efficiencies less than those of the
best mentioned here but without recent updates mentioned may have since
improved.
Luminous efficacies were largely determined by one or more of several methods,
mostly almost laughably crude. I give NO warranty as to accuracy. I have at
times slightly changed my estimates for some models. Your mileage may vary.
Red, orange, yellow, and yellow-green models (other than high power /
heatsinkable ones) mentioned here generally have maximum efficiency at
currents around 20-25 milliamps. Efficiency of these is typically less at low
currents of a few milliamps or less. The decrease is not as bad with GaAlAsP
and "T.S." AlGaAs and the most efficient InGaAsP red ones as it is with most
other InGaAsP (orangish red through yellow-green).
Some of these LEDs radiate light of slightly different colors in different
directions. This is most apparent with many white models and narrow-beam
yellow models, as well as the most efficient yellow-green models.
PLEASE NOTE that the lumen per watt figures in this document are lumens of
light produced per watt of electricity delivered to the LED. Some LED
manufacturers state much higher figures indicating the lumens per watt of
radiated light. The latter, high figure is typically in the ballpark of
60-100 for red, 130-180 for orange-red, 220-265 for red-orange, 440-500 for
yellow, 400-plus to near 660 for green (656 for Avago HLMP-C115), and around
50-90 for blue. The main purpose of this "high" figure is for conversion between
radiometric and photometric units for the emitted light. If the conversion
efficiency and the "high" lumen/watt figures are both known, multiply them to
get the lumens out per watt in.
Beam brightness and width figures below are mostly ones claimed by
manufacturers/distributors and I have NOT confirmed most of these.
UPDATE 5/11/2009: LEDEngin makes some deep red high power LEDs, available
at Mouser Electronics. These LEDs have rated peak wavelength of 655-670 nm,
typically 660 nm. These appear to me to use GaAlAsP chemistry and to be
unusually efficient for GaAlAsP.
The LEDEngin LZ4-00R210, LZ4-20R210 and LZ4-40R210, at 700 mA, are claimed to
have typical voltage drop of 10.5 volts and typical radiant flux of 1.8 watts.
This is typical efficiency of 24.5 percent.
One update of mine is that spectral analysis indicates dominant wavelength of
643-644 nm and luminous efficacy of the emitted light to be about 60
lumens/watt. If radiometric efficiency is indeed 24.5%, then overall
luminous efficacy is 14-15 lumens per watt.
Other LEDEngin high power deep red LEDs achieve efficiency similar to or
slightly lower than that of LZ4-00R210, LZ4-20R210 and LZ4-40R210.
Update 3/22/2011 Osram LH W5AM-1T3T-1-L-Z appears to me to be good for
typically 17-18 lumens/watt at 350-400 mA with very good heatsinking, maybe
22-25 lumens/watt with good heatsinking and a lower current of 100 mA.
Update 7/23/2011 Philips-Lumileds LXM3-PD01 is now available at
Future Electronics. My guess is that it's LXML-PD03-0260, rated to produce
typically 290 mW at 350 mA with a typical voltage drop of 2.2 volts, for
typical radiometric efficiency of 37%, at a junction temperature of 25 C.
This indicates overall luminous efficacy around 20-22 lumens/watt. The
DS68 datasheet indicates achieving around or a little over 92% of this
when the heatsinkable surface is at 50 degrees C. Peak wavelength is
typically 660 nm, dominant wavelength is not specified. The active material
is said to be AlInGaP.
Low power Red LEDs with GaAlAsP and Avago's similar AlGaAs in my experience,
when doing well, tend to achieve 7-8 lumens per watt. But unlike the more
efficient orangish red ones below, they are truly fairly pure red in color,
with dominant wavelength (color specification roughly meaning hue) of 637-648
nm, usually 640-645 nm, and peak wavelength of 654-665 nm, usually 660 nm.
Some favorites of mine are Stanley H-3000L, Lumex SSL-LX5093SRC/E, Lumex
SSL-LX5093XRC/4 and Panasonic LN261CALUR. Two favorites of mine with especially
deep red color and good usefulness as an indicator lamp at low current are
Kingbright WP7104LSRD and WP7113LSRD.
Radio Shack red LEDs of this chemistry include 276-086, 276-087 and 276-307.
These "automotive" red LEDs are orange-red ones even slightly more orangish
than the ones below in this "orange red" category. These have a typical
dominant wavelength of 620 nm, roughly "taillight orange-red".
The following orangish-red LEDs have typical dominant wavelength stated to
be 623 to 627 nm, which often appears to be an orangish red but sometimes
appears "plain red", especially when background is white light with color
temperature at least 4100 K.
UPDATE 4/14/2012 - Cree has XPERED-L1-R250-00701, available at
Digi-Key. According to the Digi-Key, these typically produce 71 lumens at
350 mA with a typical voltage drop of 2.1 volts. This works out to 96.6
lumens/watt. This is when junction temperature iis 25 degrees C. I would
expect 10-15% less with realistic heatsinking.
UPDATE 3/22/2011 - Lumileds LXM2-PD01-0050, according to its DS-68
datasheet, achieves minimum 50, typically 53 lumens at 350 mA when "junction
temperature" is 25 degrees C, with typical voltage drop of 2.1 volts. This
amounts to 68-73 lumens/watt. Expect ~ 10-11% less with continuous operation
while this LED's thermal pad temperature is 35 degrees C, for typically 60-66
lumens per watt.
UPDATE 1/26/2009 - TT Electronics / Optek Technology now makes red LEDs
typically producing 45 lumens from 350 mA with a typical voltage drop of 2.3
volts, when junction temperature is 25 degrees C, according to their datasheets.
This works out to 55.9 lumens/watt. My interpretation of the datasheet is to
expect usually at least 10% less with realistic heatsinking. Part numbers
include OVTL01LGAR and OVTL01LGARS, which are available at Digi-Key.
UPDATE 1/1/2008: The most efficient "low power" red LEDs I tested
so far are a batch of Nichia NSPR510CS ones I just got. Most units in this
batch achieve about 46 lumens/watt at 20 mA according to my tests. Forward
voltage drop averages 1.95 volts and light output averages 1.8 lumens
according to my testing.
UPDATE 10/30-2005 - I recently purchased some Avago HLMP-ED33-SVOOO LEDs
from Digi-Key. These achieved a good 28 lumens per watt, possibly 30. With this
efficiency advancing so slowly in recent years and tight competition between at
least some brands in achieving this efficiency in recent years, I do expect
some LEDs of some other brands to achieve similar efficiency.
Avago HLMP-E*** types mostly come in 2-3 brightness-sorted subtypes.
UPDATE 4/14/2012 - Philips-Lumileds LXM2-PH01-0070 produces minimum
of 70 lumens, typically 72 lumens at 350 mA with voltage drop of typically
2.1 volts, maximum of 2.8 volts. This works out to typically 97.9 lumens/watt,
minimum of 71.4 lumens/watt. This is with junction temperature of 25 C.
Expect about 13% less typically when the thermal pad temperature is at
35 degrees C in continuous operation, which means about 62 lumens/watt
minimum, 85 lumens/watt typical.
As for low power ones:
UPDATE 10/31/2009: Nichia NSPRR70AS, version with nominally 615 nm
dominant wavelength (NSPRR70AS is nominally red): Dominant wavelength of 615
nm has a color that sometimes appears orangish red and usually appears reddish
orange. At 50 mA, typical voltage drop is supposed to be 2.4 volts and typical
light output is supposed to be 9 lumens. This works out to 75 lumens/watt.
UPDATE 10/12/2009: Osram LA E65F-CBEA-24-1-Z, in stock at Digi-Key,
typically achieves 66.7 lumens/watt according to its datasheet. The
datasheet states that typical performance at 50 mA is 7.17 lumens and a
typical forward voltage drop of 2.15 volts.
Avago has the HLMP-DJ** LEDs, which are truly orange. The dominant
wavelength is supposedly 605 nm, which is about that of an NE-2H neon
lamp, and less red than the color of most other orange LEDs. The HLMP-DJ08
supposedly has a 9.5 candela 6 degree main beam.
UPDATE 5/27/2000 - HLMP-DJ24, 18-21 lumens/watt! The HLMP-DJ24 is a 23
degree model with a typical beam intensity of 2 candela.
Also note that these HLMP-D*** part numbers are obsoleted and the current
ones have HLMP-E*** part numbers.
Light output is said to be 3200 lumens, which I figure to be around 56-76%
of that of most 2-lamp 4-foot fluorescent fixtures.
Cree mentions this LED light fixture being shown at their booth at
Lightfair 2010.General Notes and Disclaimers:
I don't know everything, and I only mention LED brands and models I know of.
Unless otherwise noted, luminous efficacy is stated for a 25 degree Celsius
(77 degree F.) ambient with a current of 20 milliamps (350 mA for heatsinkable
models) in an environment that does not build up heat around the LED.
Heatsinkable models are generally stated to achieve their claimed performance
when cooling is sufficient to cool either the heatsinkable surface or the
junction temperature to 25 degrees C.
Indium gallium nitride types (most ultrabright blue, blue-green,
non-yellowish green, and white types) usually have efficiency that increases
with decreasing current, although the increase will reverse as current
decreases below something like 2 mA or a fraction of rated current.
Please beware that performance of many LED models at currents below a few tenths
of a milliamp or a percent or so of maximum rated current may be unreliable.
There may be significant tolerance in light output. Your mileage may vary.Most Efficient Deep Red / Pure Red LEDs - 14-20-22
lumens/watt
InGaAlP LEDs with dominant wavelength at least 631 nm are sometimes called
"royal red". These deep red InGaAlP LEDs often achieve 12-15 lumens/watt.Most Efficient Orangish Red LEDs - 46-96 lumens/watt
UPDATE 5/11/2009: Nichia NSPRR10AW, NSPRR20AW, and NSPRR70AW are claimed
to typically produce 6 lumens at 50 mA with a typical voltage drop of 2.4 volts.
This works out to 50 lumens/watt.Most Efficient Red-Orange LEDs - 66-123 lumens/watt
UPDATE 4/14/2012 - Cree XPERDO-L1-R250-00A01, available at Digi-Key,
was said by Digi-Key to typically produce 91 lumens at 350 mA with a typical
voltage drop of 2.1 volts. This works out to 123 lumens/watt. I expect
10-15% less with even rather favorable real-world heatsinking.Most Efficient Truly Orange LEDs - 18-22 lumens/watt by
Toshiba, 18-21 lumens/watt by Avago.
UPDATE 5/27/2001 - TESTED Toshiba TLOE20T, Hosfelt Electronics 25-407,
$1.45 as of the 2003 catalog, two pieces tested at 18 and 22 lumens/watt!
Dominant wavelength 605-608 nm slightly reddish orange. Claimed brigtness
10 candela.Most Efficient Yellow / Amber LEDs - 34-63-100
lumens/watt
UPDATE 7/13/2009 - Philips Lumileds announced in this July
1 2009 press release "PC Amber" (phosphor converted) Luxeon Rebel LEDs
that typically produce 70 lumens at 350 mA.
UPDATE 9/12/2012: As of this date, the most efficient one of these available at Future Electronics was rated to produce minimum of 50 lumens. The Philips-Lumileds "DS68" datasheet does not mention this brightness version; only higher ones whose lowest is rated to produce minimum of 60, typical of 69 lumens at 350 mA with a typical voltage drop of 3.05 volts.
UPDATE 7/13/2009 - Nichia NS6A083B is an amber-yellow LED whose datasheet shows a spectrum indicating that it is a phosphored LED. It typically produces 55 lumens at 300 mA with a typical voltage drop of 3.3 volts, working out to typically 55 lumens/watt.
UPDATE 1/2/2007 and 7/13/2009 - White LEDs can be filtered to yellow with yellow filters or "lenses". Typically 60-75% of the luminous/photometric output of a white LED gets through as reasonably yellow light. 40-70 lumens/watt (100 lumens/watt as of mid 2009) is possible by filtering the most efficient white LEDs. The downside is that white LEDs usually have worse aging characteristics than yellow LEDs.
The loss is greater if filtering to an orangish or "amber" shade of yellow suitable for traffic signals.
UPDATE 9/12/2012 - Philips Lumileds LXML-PL01-0050, produces minimum of 50 lumens, typically 54 lumens at 350 mA with a typical voltage drop of 2.90, maximum 3.51 volts. This works out to minimum of 40.7, typically 53 lumens per watt. This is with junction temperature of 25 C. Expect about 20% less with thermal pad temperature of 35 C, meaning about 32 lumens/watt minimum, 35 lumens/watt typical.
As for low power yellow LEDs:
UPDATE 10/12/2009 - Osram LY E65F-CADA-46-1-Z, in stock at Digi-Key, typically achieves 44.6 lumens/watt according to its datasheet. Typical performance at 50 mA is output of 4.8 lumens and forward voltage drop of 2.15 volts.
As for low power yellow LEDs in my testing: UPDATE 4/3/2010 Cree C503B-ABN-CW0Z0251, one sample tested so far, produces 1.36 lumens at 20 mA with a voltage drop of 1.99 volts, meaning 34 lumens per watt. Digikey has these LEDs. Their website says 2.5 lumens, but I suspect they botched an oversimplified formula and meant to say .63 lumen based on 5 candela and 23 degree beam angle, by using 23 degrees as half-angle.
I do expect that Osram, Toshiba, Avago and others have fair chance of achieving similar luminous efficacy with low power non-phosphor yellow / amber LEDs.
Some Toshiba LEDs and AND ones that look like Toshibas have an overall luminous efficacy around 3-4 lumens per watt. These are very yellowish green LEDs with a dominant wavelength around 570-573 nm:
Toshiba TLGA183P, Hosfelt Electronics catalog number of 25-341, US$ .99 according to their 99-B catalog, beam approx. 7-8 degrees, claimed brightness 3 candela.
AND's AND183HGP, Newark Electronics catalog number 92f2644.
Toshiba TLGE185EP, Hosfelt Electronics 25-366 has a better defined beam of supposedly 3.5 candela (I think 2-2.5) and maybe about 15 degrees but no higher efficiency. $.99 from Hosfelt according to their 2003 catalog.
LEDs of similar color but with overall luminous efficacy similar to, maybe slightly higher than that of white ones can be made by suitably adding a suitable fluorescent dye to white or blue ones. That means about 40-80 lumens/watt! If you put a white or blue LED into a piece of green-fluorescing yellow acrylic this will probably work! Go Here for LED Hacking for Fun and Danger.
UPDATE 4/14/2012 - Lumileds Luxeon "Rebel" LXML-PM01-0100 is a top brightness rank green one with worst case performance of 100 lumens at 350 mA and worst case forward voltage drop of 3.51 volts. This works out to 81.4 lumens/watt worst case minimum. According to the "DS68" datasheet, typical overall luminous efficacy at junction temperature of 25 degrees C is 100 lumens/watt at 350 mA (102 lumens, 2.9 volt voltage drop). I expect significantly higher figures at reduced current of 50-100 mA.
Now for "low power" green LEDs:
CORRECTION 9/15/2012 Cree CP41B-GFS-CM0N0674 and CP41B-GFS-CM0N0784 are 4-lead "high flux" / "spider" / "piranha" LED lamps available at Digi-Key. The middle of the flux range on log scale is 6.93 lumens and typical voltage drop is 3.6 volts. This works out to 64.1 lumens/watt.
The datasheet for these says that the minimum and maximum luminous flux is 5.5 and 8.73 lumens respectively. Assuming 3.6 volt voltage drop, this works out to 50.9 - 80.8 lumens/watt.
UPDATE 9/15-16/2012 Cree CP41B-GFS-CN0P0674 and CP41B-GFS-CN0P0784 are brighter but otherwise identical LEDs listed at Digi-Key, but not in stock as of 9/16/2012. The middle of the flux range on log scale is 8.52 lumens and typical voltage drop is 3.6 volts. This works out to 78.8 lumens/watt.
The datasheet for these says that the minimum and maximum luminous flux is 6.6 and 11 lumens respectively. Assuming 3.6 volt voltage drop, this works out to 61 - 101.8 lumens/watt.
The -674 units have dominant wavelength 515 to 525 nm, and the -784 units have dominant wavelength 520-530 nm.
UPDATE 1/1/2008 - I tested several units of Nichia NSPG510AS and NSPG520AS. My tests indicate at 20 mA average forward voltage drop of 3.05 volts and light output ranging from 3.9 to 4.4 lumens. The datasheet says typical forward voltage drop is 3.2 volts. This indicates 61 to 72 lumens per watt overall luminous efficacy.
UPDATE 12/25/2007 - I just got a batch of NSPG510AS units that average 72 lumens/watt at 20 mA. At 3 mA, they had a forward voltage drop averaging 2.6 volts and produced on average .94 lumen according to my testing, for an overall luminous efficacy of 120 lumens/watt.
UPDATE 7/28/2009 - I tested a NSPG520AS at 1.69 milliamps, and found forward voltage drop of 2.45 volts and quantum efficiency of 29.5%. The color matched that of a Nichia green LED whose spectrum was analyzed with results indicating average photon energy of 2.339 eV and luminous efficacy of the emitted light being 512 lumens/watt. This indicates conversion efficiency of 28% and overall luminous efficacy being about 140 lumens/watt.
Now for "low power" LEDs:
UPDATE 7/30/2000 - TESTED BG Micro LED-1052 narrowbeam bluish green Nichia NSPE590S - preliminary figure 24-26 lumens/watt on the single sample ordered. This model has an irregular beam with a small central bright pattern (roughly 7 by 4 degrees) with a claimed typical brightness of 20,800 mcd at 20 mA.
TESTED Hosfelt Electronics 25-376, apparently a Nichia model. Tentative figure for overall luminous efficacy 24-27 lumens/watt. Optical power output 7 mW at 20 ma with a 3.75 volt voltage drop - 9.3 percent conversion efficiency! Expect even better efficiency in the future since the voltage drop will usually be 3.3-3.6 volts.
Cree and Avago also make bluish green LEDs suitable for traffic signals.
UPDATE 4/14/2012 - Cree XPEBLU-L1-0000-00201 produces typically 38 lumens at 350 mA with a voltage drop of typically 3.2 volts. This works out to typically 33.9 lumens per watt at 25 C junction temperature.
Now for "low power" blue LEDs:
UPDATE 1/3/2008 - UNTESTED, SIGHT UNSEEN: Nichia has new blue LEDs recently becoming available. They mostly have a revision letter 1 beyond that of their long-standing blue ones. An example is NSPB500AS, which is the improvement of NSPB500S and is claimed to have a beam intensity of 11 candela at 20 mA.
According to published millicandela figures and my extrapolation from my testing of related white Nichia LEDs, it appears to me that output is roughly tripled. With a voltage drop of typically 3.2 volts instead of 3.5 volts, efficiency is increased by a factor of *very roughly* 3.3 (and this is an extrapolation of mine, not an actual test result). With NSPB500S achieving probably about 8 lumens per watt, I expect the new models to achieve about 25 lumens per watt. I expect optical output at 20 mA to be about 22 mW, for a conversion efficiency around 34 percent.
UPDATE 5/11/2009: Digi-Key has in stock Cree CP41B-BFS-CG0H0454, which is mentioned by Digi-Key to produce typically 3.13 lumens at 30 mA with a voltage drop of typically 3.6 volts. This works out to 29 lumens/watt.
UPDATE 3/18/2011 - Cree XMLBWT-00-0000-0000U20E1 (available at Digi-Key) "cool white" LED typically produces 310 lumens at 700 mA with a typical voltage drop of 2.9 volts. This works out to typically 153 lumens/watt.
This is with junction temperature of 25 degrees C, as opposed to heatsinkable surface being at 25 degrees C.
This is a very high power LED, comfortably producing 750 or more lumens at 2 amps, and its absolute maximum current rating is 3 amps.
The datasheet for Cree XM-L2 LEDs is here.
UPDATE 8/11/2011, 3/20/2013 - Philips-Lumileds "Luxeon Rebel" of top lumen bin (LXML-PWC2-0200) has rated minimum luminous output of 200 lumens at 700 mA, and typical output of 135 lumens and typical luminous efficiency of 135 lumens/watt at 350 mA. With typical voltage drop of 2.9 volts at 700 mA, low side luminous efficacy is 98.5 lumens/watt. Since this is measured witha 20 millisecond pulse rather than continuous operation, the junction temperature rise of continuous operation is likely to reduce this by about 2% to 96.5 lumens/watt even if the theraml pad temperature is cooled to 25 C.
I would reduce this to 91 lumens/watt when the thermal pad temperature is a realistic 60 degrees C.
For a worst case, consider the voltage drop to be the 3.25V maximum rather than the 2.9V typical, and extra heating as a result. This makes the overall luminous efficiacy at 700 mA 81 lumens/watt.
UPDATE 7/4/2010 - Nichia NVSW119A with 350 mA current typically produces 140 lumens with a typical voltage drop of 3.0 volts. This works out to typically 133 lumens/watt. This LED is a version with a less-bluish but still "cool" shade of white, with a claimed typical chromaticity that is close to that of 5,000 Kelvin.
NOTE - All high power white LED data above is from datasheets and datasheet interpretations and not personally experienced actual test results.
UPDATE 5/11/2009 Cecol / Citizen Electronics produces their CL-L233-C13N with nominal light output of 1335 lumens at 720 milliamps with a typical voltage drop of 18.6 volts, which works out to 100 lumens/watt.
UPDATE 1/26/2009 - Citizen Electronics AKA "Cecol" has an 8-chip white LED lamp (CL-654-C1N) rated to typically produce 96 lumens from 1.21 watts. That works out to 79.5 lumens/watt. My tests on samples that I have obtained indicate about 92-plus lumens from 1.21 watts (76-plus lumens/watt).
Now for "low power" white LEDs:
UPDATE 6/30/2012 - Nichia announced on 5/10/2012 their NSPW510HS-K1, which has a claimed typical luminous efficacy of 170 lumens per watt at 20 mA. Typical light output is 10 lumens and typical voltage drop is 2.8 volts at 20 mA. Nominal beam width is 30 degrees. This LED may have a chip similar to that of NSPWR70CS-K1, which is larger than usual for low power LEDs. The beam may have different characteristics from those other Nichia NSPW-510 series LEDs.
UPDATE 4/10/2010 - Nichia has a 5 mm white LED lamp, NSPW500DS, that is similar to NSPW500S except with higher output and a nominally narrower beam - and a beam intensity of typically 27 cendela at 20 mA. Preliminary testing of related units with "D" revision letter (NSPW510DS) indicate 55-65 lumens/watt. I just tested a 2008-vintage NSPW510DS and found it to achieve 68 lumens/watt, which may be a little on the high side for that vintage.
Update 3/20/2013: Nichia has their NSPW510GS-K1, which has a nominally 30 degree beam. Based on its datasheet and my tests on related Nichia LEDs, I extrapolate its typical overall luminous efficacy to be about 75 lumens/watt.
Update 5/11/2009: Nichia has an extremely efficient 4-lead LED, NSPWR70CS-K1, A.K.A. NSPWR70CSS-K1. At 20 mA, it is said to typically produce 8.7 lumens at with a typical voltage drop of 2.9 volts, which works out to 150 lumens per watt. At 50 mA, typical luminous flux is stated to be 20 lumens and typical voltage drop is stated to be 3.1 volts, which works out to 129 lumens/watt.
I have tested this LED. My testing indicates 140-145 lumens/watt at 20 mA for a few that I have tested.
UPDATE 4/10/2010: As for a 2-lead through-hole "5 mm" non-Nichia DigiKey- available LED, there is the Cree C535A-WJN-CU0V0231. My composite result from 2 different testing methods is 81 lumens/watt at 20 mA, 97 lumens/watt at 8 mA, and peaking at 102 lumens/watt at 2.2-3 mA.
This LED appears to me to be one where the light-emitting surface is a convex surface that most rays of outgoing light are largely close to perpendicular to both before and after exiting the forward surface of the LED. It appears to me that this reduces internal reflection losses, but also results in a wider beam angle. This LED has a nominal beam width of 110 degrees.
The above white LED lamps have blue chips plus a phosphor to convert some of the blue light to yellowish light of broadband spectral content from mid-green to mid-red. The color is usually a cool white to "daylight" slightly bluish or sometimes violetish-bluish white, usually of about 5000-6500 K. Color rendering index of the most efficient ones as well as most other white LEDs is usually stated to be 65 or 70 when stated. There are white LEDs with improved color rendering index, but their overall luminous efficacy is compromised.
Overall luminous efficacy typically peaks at 1.5 to 3.5 mA and remains above that at 20mA usually at least down to .5-1 mA. Efficiency and light output become less predictable below .4-.5 mA.
White LEDs have most of their photometric output from a phosphor, and so the luminous efficacy of emitted light does not improve with decreasing current as much as with colored InGaN LEDs. In fact, spectral shifting of the LED chip's output away from wavelengths best-utilized by the phosphor can impair overall luminous efficacy at low currents. However, photometric output per milliamp seems to usually improve with decreasing current down to about 6 milliamps, sometimes as low as 2.5-3 milliamps. I have tested one low power white LED (Cree C535A-WJN-CU0V0231) at various currents, and found ratio of photometric output to current to be maximized at 4-5 mA, achieving about 1.135 times that achieved at 20 mA. This LED had efficiency maximized at 2.2-3 mA, with efficiency about 1.26 times that at 20 mA.
Important Note on Gallium-Nitride LEDs!
Gallium nitride and indium gallium nitride LEDs are fussy, and do not
like their ratings to be exceeded. Exceeding 5 volts reverse voltage even with
low current is supposedly damaging to them. I suspect that destructive
electrolysis is what goes wrong. Peak forward currents in excess of 100 mA
may also be bad for low power ones. Many of these LEDs are also supposed to
be considered static sensitive.
UPDATE 5/14/2012 - Cree C503B-GAS-CB0F0791 and C503B-GAN-CB0F0791 typically produce 53.6 candela at 20 mA.
Brightest white 5 mm LED lamp at 20 mA that I am aware of as of 5/11/2009 - 3/20/2013: Nichia NSPW500DS (15 degree beamwidth, 27 candela) and Nichia NSPW500GS-K1 (same beam angle, 30-33 candela, but has compromised life expectancy).
UPDATE 8/8/2009: Luminus CSM-360-W is a very high power LED with 4 large dice (chips) in series and a maximum current of 6.3 amps. Luminous flux (output), depending on bin/rank, is in the ballpark of 3,000 lumens at 3.2 amps, with a typical voltage drop of 12.8 volts, working out to 41 watts and 73 lumens per watt. Output and efficiency are 20% greater at the borderline between the highest two binning ranks.
Philips Lumileds makes high power heatsinkable "Luxeon" LEDs, some of which produce over 200 lumens.
Cree and Nichia are in this game.
Nichia has a link here.
Cree has high power LEDs up to about 10 watts for single chip ones at Digi-Key, some of which are rated to produce over 1,000 lumens.
Lamina Ceramics produces heatsinkable high power LED arrays. Some of their arrays take over 100 watts and are of size 1.06 by 1.25 inches (31.75 by 26.67 mm) - and this obviously needs major heat sinking. Please consider thermal resistance of the device and light output as a function of junction (LED "die" or "chip") temperature!
Cecol / Citizen Electronics produces an LED with nominal light output of 1335 lumens at 720 milliamps with a typical voltage drop 0f 18.6 volts (100 lumens/watt).
LEDEngin is a maker of 1-chip high power LEDs and 4-chip ones with nominal wattage as high as 15 watts.
Some Avago, Chicago Miniature, and most AND (apparently Toshiba) LEDs are available from Newark Electronics. Call 800-4NEWARK or visit http:/www.newark.com. They are in a position to collect sales tax if you live in or order from any U.S. state with a sales tax. Minimum order is US$ 25. Shipping is extra and duplicate shipping charges apply if you order more than one type of item not all in stock in the same warehouse. Higher minimums may apply to non-stock merchandise - often 500-1000 pieces of any non-stocked Avago LED lamp and maybe even for some stocked ones, and this applies with some other Avago distributors as well.
Future Electronics is the main distributor of Lumileds products and is a distributor of other LEDs.
Hosfelt Electronicssells some bright Toshiba LEDs and some other interesting LEDs.
Hosfelt has some typo errors - some blue LEDs have lowish supposed voltage
drop figures like 2.5-3 volts, but expect about 3.4-3.5 volts for older models
at 20 mA, about 3.1-3.2 volts for newer models. Some strange beam angle figures
have appeared in their web site and some of their catalogs - 29.5 and 28.5
degrees. Possibly someone saw the "two-theta-half" symbol which resembles
28 1/2 as the actual number of degrees. These look like typos, and are not
attempts on Hosfelt's part to give falsely optimistic specifications.
Hosfelt lists some strangely high brightness figures for supposedly UV LEDs.
I suspect those were measured with a meter whose spectral response differs
from that of human vision, or were obtained by converting radiant output to
luminous intensity with a wrong conversion factor.
Nichia LEDs are best obtained from their sales offices. In North America, check out Nichia America.
Toyoda Gosei makes bright green and blue LEDs.
Toyoda Gosei LED info is now on the web at http://www.toyoda-gosei.co.jp/led/e-index.html.
A lumen is defined as the "luminous flux" of 1/683 of a watt of monochromatic
light that has a frequency of 540 terahertz, or a wavelength of approx. 555.5
nm.
One thing worth noting is that a lumen is defined secondarily, in terms of
the candela (which is 1 lumen per steradian), and the candela is defined
primarily (it's the "beam candlepower" of 1/683 watt per steradian of 540 THz
monochromatic light.)
Light of wavelengths other than 555.5 nm have a different amount of lumens
per watt of radiation. The number of lumens in a watt of wavelength other
than 555.5 nm is 683 times the photopic function of
the wavelength in question, divided by the photopic function of 555.5 nm
(which I believe is very close to but not exactly 1).
A "USA-usual" 100 watt, 120 volt, 750 hour "regular" (A19) lightbulb usually produces 1710 lumens.
Lumens per watt is a measure of efficiency in converting electrical energy to light. Multiply this by the watts dissipated in the LED to get lumens. A typical red, orange, or yellow or yellow-green LED has a voltage drop around 2 volts and is getting around .04 watt at the typical "standard" current of 20 milliamps. A blue, white, or non-yellowish-green one typically has a voltage drop of 3.5 volts at 20 mA and gets .07 watt at 20 mA.
A candela is a lumen per steradian, or "beam candlepower". (Actualy, as
mentioned above, the candela is a primarily defined metric unit, while the
lumen is defined in terms of the candela.)
So lumens are candelas times the beam coverage in steradians. Candelas are
lumens divided by the beam coverage in steradians. Ideally, that is -
assuming that all light is within the beam and the "candlepower" is
constant within this beam.
So you may now be wondering what a steradian is. It is 1 / (4 * pi) of a whole sphere or 1 / (2 * pi) of a hemisphere or about 3283 "square degrees", to the extent there is such a thing as a "square degree". To get steradians from the beam angle:
Steradians = 2 * pi * (1 - cos (.5 * (beam angle)))
(NOTE: There are a few other expressions equal to this. Proving that is homework for 12th graders taking trig / "elementary functions".)
So if you determine the steradian beam coverage and multiply that by the candela figure (or 1/1000 of the millicandela figure), you get the lumen light output - very roughly! The beam is not uniform and it does not contain all of the light. Obtaining lumens from beam angle and candela can easily be in the +100 / - 50 percent range. Actual lumens are generally higher than predicted by this formula with smaller beam angles of 8 degrees or less since the nominal beam does not include a secondary "ring-shaped" "beam" that usually surrounds the main one. Also note that some beam angle figures are optimistic and could lead one to expect a lot more lumen light output than actually occurs.
Please read my disclaimer.