As requested, I collected all of my power LED tests in this post in chronological order and linked to it in the first post (link to original post by clicking the date).
Also, I'm repeating a message from the first post regarding LED recommendations as the volume of PMs I've received asking about which LED to use has gotten to be annoying:
Although I have tested many LEDs in this thread, I am not in a position to recommend specific LEDs for use in flashlights or other devices to people. I feel the need to mention this because I have received quite a few PMs asking me which LED would be good for such and such project. I feel it would be best to start a new thread asking for LED recommendations rather than asking me. I just don't have the time or desire or ability to help people determine which LED to use in any given project.
08-09-2005
I made a jig for testing power LEDs. Here are my results for a Q3J Luxeon, a Lamina BL-2000, a Seoul Semiconductor W32182 bin RSX0I star, and a Cree 7090 XR-E bin P4:
Here are the relevant spreadsheets.
I have 5 Q bin Luxeons. Four of them seem about equal in brightness and the fifth is about 10% dimmer. Assuming then that the dim one is at the low end of the Q-bin (say 31 lumens), then the other ones should test in the mid 30s. My results give me 37.1 lumens, a little past the middle of the Q-bin. I think this more or less verifies the accuracy of my methods. At worst my results are less than 10% too high.
12-03-2006
Cree 7090 XR-E bin P4 (purchased November 2006)
I purchased these from CPF member Erasmus. These are tint bin WH and flux bin P4 (80.6 to 87.4 lumens at 350 mA). The color temp of these seems a close match for my 5000K fluorescents which makes the WH bin perfect for interior lighting although perhaps a bit warm for flashlights. I measured the 50% beam angle at 95.3° which is somewhat wider than the 75° given on the spec sheet. Despite the out of spec beam angle, the overall flux at 350 mA is 85.67 lumens which is within the range of the P4 bin (and also a verification of the accuracy of my methodology). Vf at 350 mA is 3.25V and overall efficiency is a very impressive 75.37 lm/W. Even at 700 mA efficiency remains above 60 lm/W. Luminous flux at 500 mA is about equal to the Lamina Ceramics BL-2000 arrays but the power input is only around 1.7 watts instead of the 4.7 or so watts used by the Lamina array. Although these obviously aren’t a 20 mA part if they were they would break previous records by a huge margin, coming in at nearly 112 lm/W. There’s really nothing more to say about these than hasn’t already been said by me and many others. They represent a huge step forwards in LED technology.
Here is the efficiency versus current chart:
02-04-2007
I finally got around to testing the two Cree XR-E emitters 3rd_shift sent me. The purpose of this test was to determine the difference between an emitter with and without the dome. The unmodified Cree XR-E bin P2 emitter tested as follows:
Output was 70.67 lumens at 350 mA. This is right in the middle of the P2 bin (67.2 to 73.9 lumens). The same bin emitter with the dome removed only had an output of 54.35 lumens at 350 mA. The beam angle was wider as well (122° versus 83.3° for the unmodified emitter). The relative intensity versus angle for the two emitters is shown below (domeless emitter in magenta):
Apparently the silicon encapsulant combined with the dome helps to extract a considerable amount of light from the die. The output of the domeless emitter is 24% less than the stock emitter.
02-04-2007
Seoul Semiconductor W42180 bin U (tested February 2007)
I purchased a U bin Seoul Semiconductor emitter from milkyspit recently. The results of the test are shown below:
I believe the results speak for themselves. The efficiency at 350 mA is a very impressive 82.1 lm/W and the output is 96 lumens. This is a new record for power LEDs and also matches my best results for single die 5mm LEDs. Beam angle is close to 130° which means these have a light distribution similar to a Luxeon emitter. Since the emitter is rated for 1000 mA I felt comfortable going to 1500 mA, at which point output more or less leveled off. The output scales with current almost identically to the Cree XR-E bin P4 which I tested in December but this is no surprise since both emitters use the same die. Note that the U bin has a range of 91 to 118.5 lumens so these are at the low end (which I expected). I anticipate that the Cree XR-E Q3 bins will offer similar results. Shown below is a chart of Vf, power, and lumens at various currents.
09-04-2007
Lumileds Rebel White LXML-PWC1-0100 (acquired July 2007)
Note: Earlier results multiplied by correction factor of 1.116 and post edited accordingly (See post #138 for explanation).
I purchased a pair of these from Future Electronics for evaluation. I only tested one of the two samples. Color bin was not specified, but these are similar in color to the WH Crees, so I'd guess that they are V0s. I soldered the Rebel to a small length of brass bar with two holes drilled in the ends. I screwed the bar to my heat sinked power LED test jig with some thermal grease at the interface for better heat transfer. Beam angle measured 100.1°, a bit narrower than Luxeon IIIs, and the beam pattern is close to, but not exactly, lambertian. In the course of testing I learned how important it is to keep the lens of these LEDs clean. My initial test results gave roughly 91 lumens at 350 mA. I tried cleaning the lens with alcohol and then rerunning the tests. The final results were 96.7 lumens at 350 mA, but I later determined that I needed to apply the correction factor for my light meter. This revised the results to 107.9 lumens which is within spec. At 700 mA the Rebel put out 183.1 lumens, just about dead on the specified 180 lumens. Output continued to increase with current, reaching over 290 lumens at 1500 mA, which is as high as my current source goes. Moreover, the output curve wasn't entirely flattened out, even at 1500 mA. I would guess that output would continue to increase to 2 amps, albeit not very much over the output at 1.5 amps. Vf was extremely low and didn't rise very fast with current. It was 3.14V at 350 mA but only 3.43V at 1500 mA. Efficiency at 350 mA was 98.2 lm/W, a new record for power LEDs, and tantalizingly close to the magic 100 lm/W. Interestingly, with the apparent stagnation in small LED efficiency since early 2006, power LEDs are now actually more efficient than indicator-type LEDs. Moreover, efficiency at 1000 mA, the maximum specified operating current, was still a very decent 69.4 lm/W, about on par with CFLs, and stayed above 56 lm/W even at 1500 mA. Maximum efficiency was reached at 20 mA, and it was an incredible 150.7 lm/W. This translates into a conversion efficiency of over 45%. Efficiency remained above 100 lm/W until around 325 mA. Overall the Rebels have broken all previous records, but I suspect their time on top will be short-lived as I have yet to acquire the Cree XR-E Q5s for testing.
Original post:
I purchased a pair of these from Future Electronics for evaluation. I only tested one of the two samples. Color bin was not specified, but these are similar in color to the WH Crees, so I'd guess that they are V0s. I soldered the Rebel to a small length of brass bar with two holes drilled in the ends. I screwed the bar to my heat sinked power LED test jig with some thermal grease at the interface for better heat transfer. Beam angle measured 100.1°, a bit narrower than Luxeon IIIs, and the beam pattern is close to, but not exactly, lambertian. In the course of testing I learned how important it is to keep the lens of these LEDs clean. My initial test results gave roughly 91 lumens at 350 mA. I tried cleaning the lens with alcohol and then rerunning the tests. The final results were 96.7 lumens at 350 mA. Since this is less than Lumiled's tolerance for lumen measurement this is still within spec. More importantly, at 700 mA the Rebel put out 179.63 lumens, just about dead on the specified 180 lumens. Output continued to increase with current, reaching over 260 lumens at 1500 mA, which is as high as my current source goes. Moreover, the output curve wasn't entirely flattened out, even at 1500 mA. I would guess that output would continue to increase to 2 amps, albeit not very much over the output at 1.5 amps. Vf was extremely low and didn't rise very fast with current. It was 3.14V at 350 mA but only 3.43V at 1500 mA. Efficiency at 350 mA was 88.0 lm/W, a new record for power LEDs. Interestingly, with the apparent stagnation in small LED efficiency since early 2006, power LEDs are now actually more efficient than indicator-type LEDs. Moreover, efficiency at 1000 mA, the maximum specified operating current, was still a very decent 62.2 lm/W, about on par with CFLs, and stayed above 50 lm/W even at 1500 mA. Maximum efficiency was reached at 20 mA, and it was an incredible 135 lm/W. This translates into a conversion efficiency of over 40%. Efficiency remained above 100 lm/W until 200 mA. Overall the Rebels have broken all previous records, but I suspect their time on top will be short-lived as I have yet to acquire the Cree XR-E Q5s for testing.
10-01-2007
Relevant description of change in methodology:
I changed my setup somewhat immediately before the tests of the Rebel 100 and the Hebei LEDs. I set up a series of baffles and totally enclosed them to block out any ambient light:
I even put a removeable cover to block ambient light near the light meter:
The purpose of these modifications was to eliminate guestimating the background light which needed to be subtracted from the light meter reading. For 5mm LEDs this was at most about 0.5 lux, but for power LEDs it was considerably more. Prior to this, I would block out the direct portion of the beam with a piece of cardboard, note the reading, then subtract it from the unblocked reading. This method always bothered me because it introduced another variable. While the background reading was fairly steady, it did vary enough depending upon the placement of the cardboard to cause concern. Hence my use of the term guestimating at the start of this paragraph. The modified setup introduces consistency. When I block off the small hole where light enters from the LED, the reading is at most 0.1 lux, even in a undarkened room. I still do my testing in a darkened room, but with the new setup I don't have to!
Now this is all good and well except that when I tested the Rebel 100 I was getting somewhat less than the minimum of 100 lumens (96.7 lumens @ 350 mA to be exact). However, according to the results of the CPF light meter testing which I had participated in my light meter was reading low for white LED light. The correction factor was 1.116. I applied the correction factor to my Rebel 100 results in post #127 and the numbers are more in line with what I should have gotten.
The only question remaining was whether or not I could reliably compare my earlier results with my new ones. To answer this question I decided to retest the P4 bin Cree XR-E which I had tested last November. The original results were 85.67 lumens at 350 mA. The
uncorrected results using the modified tester were 80.24 lumens at the same 350 mA. This was about 6.4% low. The corrected result was 89.55 lumens, within 4.5% of my original results. I also ended up with a somewhat narrower beam angle (new results in red, old in blue):
It seems then that although I did not apply any correction factors to my earlier results the inherent methodology resulted in slightly wider beam angles which more or less compensated for the lower absolute lux readings. Remember that all of my earlier power LED test results pretty much fell within the ballpark of where they were supposed to for a given bin. The only problem is that LEDs obviously come in different tints, and I suspect I would need different correction factors depending upon the tint. Based on the fact that my light meter was nearly dead-on with incandescent light, the correction factor would increase with increasing color temperature. However, since guestimating correction factors would make this testing more art than science, I'll stick to using the official correction factor of 1.116. The fact that my corrected result for the P4 Cree is a little high probably has to do with that LED being a warmer (WH) tint bin.
10-01-2007
Cree 7090 XR-E Warm White bin P4 (acquired September 2007)
I ordered some Q5 Cree XR-Es from CPF member
Erasmus. Along with the Q5s Erasmus sent me a Cree XR-E warm white bin P4 for testing. The P4 bin is specified at 80.6 to 87.4 lumens at 350 mA. The color temperature looked like roughly 3300K, so I would say the tint bin was 7A. Since the color temperature was in the incandescent range, I didn't need to apply a correction factor. The output of 83.0 lumens at 350 mA is solidly within the P4 flux bin.
Results are shown below:
10-01-2007
Cree 7090 XR-E bin Q5 (acquired September 2007)
I ordered 10 Q5 Cree XR-Es, bin WG, from CPF member
Erasmus. The Q5 bin is specified at 107 to 114 lumens at 350 mA. The color temperature of the WG bin is roughly 6000K. The results are a little low (105 lumens at 350 mA), but remember that this is a cooler bin. My correction factor is probably a little too low for such a cool tint, and this is what accounts for the discrepancy. In any case, the difference between the actual measurement and the manufacturer's specification is less than 2%, and my setup is far from 100% accurate anyway. Even if this difference is real, it is well outside what would be noticeable with the eye.
Vf is 3.20V @ 350 mA, efficiency is a very impressive 93.7 lm/W. Note that this is a little less than the corrected results for the Rebel 100 (98.2 lm/W @ 350 mA). However, the Rebel's higher efficiency is nearly all due to its lower Vf (3.14V @ 350 mA), and the fact that it is a warmer tint (and hence reads a little higher on my light meter). Also note that despite the slightly lower output at 350 mA the Cree bests the Rebel in terms of raw output at higher currents (298.5 versus 290.5 lumens at 1500 mA). The Rebel 100 still has a slight edge in efficiency at 1500 mA (56.5 versus 54.7 lm/W) due to its Vf increasing less with current than the Cree Q5. I took the Cree all the way to 2000 mA and it managed 334 lumens.
Results below:
03-27-2008
Cree 7090 XR-E bin R2 (acquired March 200
I borrowed an R2 Cree XR-E, bin WG, from CPF member
nein166 for testing. The R2 bin is specified at 114 to 122 lumens at 350 mA. The color temperature of the WG bin is roughly 6000K. The results are as show below:
These results are nothing short of amazing! The output at 350 mA is nearly 122 lumens, well above any previous results for power LEDs at that current. Despite the middle of the road Vf of 3.31V, efficiency at 350 mA is still 105.3 lm/W. It remains above 100 lm/W past 400 mA. Even at 1000 mA, efficiency is nearly 75 lm/W. Things get even more interesting at low currents. Under 50 mA, efficiency hovers around 145 lm/W. This represents a wall-plug, or power-to-light conversion efficiency, of around 45%.
Output scales with current in pretty much the same manner as other XR-Es I've tested. At 1000 mA output is over 270 lumens. It approaches 400 lumens at 2000 mA. Cree has continued to raise the bar for LED performance. While we won't see as dramatic improvements as in the past, Cree has continued to squeeze every last ounce of perfomance from its XR-E line of LEDs. I expect we'll have R4 bins and beyond by this time next year.
07-06-2008
This was a test of a Cree XR-E R2
saabluster sent me mounted on a heat pipe attached to a copper plate:
I finally finished the testing. First order of business after drilling the holes and attaching the LED to my heat sink was to determine the nominal output the usual way. My results were 122.97 lumens at 350 mA, slightly above spec actually, but then again the margin of error for my testing is probably a few percent either way. Vf was a somewhat high 3.37V. Efficiency was 104.3 lm/W.
Next order of business was to begin increasing current until either the LED blew, or it didn't get any brighter. For this round of tests I used passive cooling. The heat pipe and copper plate spread the heat to the heat sink, which in turn dissipated it. The results were a little better than my usual setup. Apparently the heat pipe, or perhaps the combination of heat pipe and copper plate, did
something. At 2 amps the output was 3.35 times the output at 350 mA, compared to 3.21 for the stock setup. The heatpipe provided a small (about 4%) advantage here. As I increased the current past 2 amps I was crossing my fingers for the LED to hold together. Finally at 2.5 amps the output stopped increasing. At 2.6 amps it was a little lower. Peak output was passive cooling was
436.7 lumens. Vf at 2.5 amps was 4.22V, and total power input was 10.55 watts.
Obviously in the case of passive cooling you'll eventually reach a point of diminishing returns. However, it's a good indication of what a reasonably-sized flashlight body can do if you pump enough current into the LED. The next order of business was the ultimate output which the LED was capable of. To that end I set a large fan to actively cool the heat sink. Throughout the tests the temperature of the copper plate the LED was mounted on remained very close to room temperature. Once the temperature rise of the heat sink was factored out of the equation, I was able to get increasing output past 2.5 amps. The peak output was reached at 2.7 amps. At 2.8 amps it was a little less. The results at 2.7 amps were
453.9 lumens, Vf was 4.32V, and a power input was 11.664 watts. This is the absolute maximum which this Cree R2 emitter can give under ideal cooling conditions.
Wanting to continue this "insanity", I bolted the copper plate and LED to the cold plate of one of my thermoelectric assemblies. By the time ice was starting to form on the plate, the LED was giving me
502 lumens at 2.5 amps. Even though below ambient cooling was required, the 500 lumen barrier for a single emitter was finally broken. Even better, the emitter is none the worse for all the abuse it's been through. It didn't have to die in the name of science.
Here are some charts of the final results:
Lumen output using fan-cooled heatsink
Comparison of passive versus fan-cooled output
10-20-2008
Seoul Semiconductor P7 Bin C (tested October 200
I obtained a Seoul P7 of the highest brightness bin this week. The C bin is rated at between 740 and 900 lumens. For this test I epoxied the P7 to a 60mm heat sink. I tested the output with and without a fan cooling the heat sink. Here are the results:
At the nominal current of 2800 mA the fan makes only a small difference. Output is 731 lumens without the fan, and 742 lumens with fan cooling. This is barely but still within ratings. Efficiency at nominal current is 70.7 lm/W, good but certainly not in the same league as the latest single-die Cree or Seoul LEDs running at a comparable current of 700 mA. However, that's to be expected since the thermal path per die for the P7 isn't as good as for the Seoul P4 or Cree XR-E. If you underdrive the P7 then you can get significantly greater efficiency. For example, at 1000 mA the efficiency is 97.9 lm/W, way better than even an R2 bin XR-E at that current, and output is 329 lumens, about 20% greater than the Cree at that current. At 350 mA the P7 can manage 115 lm/W and 125 lumens, both figures somewhat greater than the best single die LEDs. Efficiency peaks in the 125 lm/W area at currents under 100 mA. Output versus current actually remains linear to well under 10 mA, but with the slight drop in Vf you're only gaining a few percent efficiency compared to 100 mA.
The results when cranking up the current are interesting. Without the fan cooling the heat sink, the output levels off at 6 amps and 998 lumens. With the fan I was able to go to 7 amps and 1114 lumens, although the increase in output was flat from 6.8 to 7.0 amps. The increase from 6.5 to 6.8 amps barely registered on my light meter. Therefore, even with very good forced-air cooling there is no point taking the P7 past about 6.5 amps, and only then if you want to squeeze out every last lumen. In fact, if you consider that the eye can't detect brightness differences of 10%, then the absolute maximum current of the P7 should be no more than around 4.5 amps, even less with the heat sinking typically available in flashlight bodies. At 4.5 amps you will get about 1000 lumens with very good cooling. Note however that 1000 lumens is only 35% more than what the P7 will give you at its nominal current of 2.8 amps. The lumen increases from overdriving the P7 just aren't as dramatic as with single die LEDs. In a typical situation with less than stellar heat-sinking I doubt it even pays to go above the nominal 2.8 amp current.
01-13-2009
Gryloc sent me a pair of DSW0J Seoul Semiconductor P7s and one each of U2SW0H and U2SV0H P4s. One of the P7s appeared defective (it didn't light up until driven at around 1 amp, and output was reduced compared to the good one). Here are the results of the good P7:
Output at 2800 mA is only a little lower than the speced value of 800 to 900 lumens. Note that I was able to reach nearly 1200 lumens at 7 amps. Unlike the last P7 test, this time around I always had a fan cooling the heat sink in order to maximize output.
Here are the results of the U2SW0H:
Here are the results of the U2SV0H:
The U2 bin is speced for 100 to 118.5 lumens. Both samples met this spec, although on the low side. Although not quite in the same league as Cree's best XR-E bins, these are close enough that most couldn't tell the difference by eye. Note that the efficiency of these really falls off above 1500 mA, and not much past 1500 mA the output levels off. At 2000 mA the output is quite a bit less, and the LEDs also turn an angry blue color. Hence, I only drove them a few seconds at that level.
07-21-2009
Cree 7090 XP-E bin R2 (acquired May 2009)
I borrowed an R2 Cree XP-E, from CPF member
nein166 for testing. The R2 bin is specified at 114 to 122 lumens at 350 mA. The color temperature of this sample was roughly 6500K. The results are as show below:
These results are excellent! The output at 350 mA is nearly 114.6 lumens, meeting spec. Vf is a very low 3.13V and efficiency at 350 mA is 104.6 lm/W. It remains above 100 lm/W past 400 mA. At 1000 mA, efficiency is nearly 75 lm/W. Efficiency at very low currents peaks at around 133 lm/W around 40 mA. This isn't quite as good as the R2 XR-E samples I've testing. Also note that I've added a new test point at 10 mA for power LEDs so that the inflection point where efficiency drops shows up more clearly in my graphs. More interesting than the results at low current is the high current performance. Despite the tiny package, the XP-E does quite well at higher currents. At 1000 mA output is 252 lumens. At 2000 mA it reaches 330 lumens. While these figures aren't quite as good as the XR-E's ~270 and ~400 lumens, respectively, they are more than I expected given the XP-E's package size and thermal path. I'll also note that my mounting method was less than optimal. I attached the LED with Arctic Alumina thermal epoxy. Had it been soldered to the heat sink, I think my results would have been somewhat higher.
07-21-2009
CPF member
HarryN arranged for several LEDs to be sent to me for testing. One was the LEDEngin LZ4-40NW10 10 watt neutral white star. The others were the K2 TFFC cool white -220 and the K2 neutral white -180. Here are the results:
LEDEngin LZ4-40NW10 10 watt neutral white (acquired July 2009)
The 10 watt LEDEngin is a 4-die series connnected LED designed for the general lighting market. The dome is about the same size as that of the SSC P7 and is translucent rather than clear. The output is speced at 400 lumens at 700 mA. Here are the test results:
Color temperature looks to be around 4000K and beam angle is 90°, somewhat narrower than on most power LEDs but still fairly wide. Output at 700 mA meets spec almost exactly at 399.9 lumens. Vf is 13.96 V, or 3.49 volts per die, power input is 9.77 watts, and efficiency is only 40.9 lm/W. Keep in mind however that warm and neutral white LEDs generally don't perform as well as their cool white counterparts. Output doesn't scale much with current, leveling off at a bit over 500 lumens at 1300 mA. Overall the LEDEngin appears to be well made. It would be nice to see this product made with higher performing dice.
Lumileds K2 TFFC neutral white -180 (acquired July 2009)
This is the highest available bin of Lumiled's neutral white K2 presently available. The spec sheet does list a 200 lumen bin, but Future so far doesn't carry it. The 180 lumen spec is at a drive current of 1000 mA. Here are the results:
Color temperature looks to be in the high 3000s. As can be seen, the K2 TFFC neutral white 180 exceeds the spec at 1000 mA with nearly 193 lumens. Lumileds also specifies typical figures of 85, 150, and 250 lumens at 350 mA, 700 mA, and 1500 mA, respectively. The test results at these respective currents were 86.8, 151.4, and 243.6 lumens, all either exceeding or very close to specification. Vf at 350 mA is 3.29 volts, and only rises to 4.03 volts at 2500 mA. This brings me to the area where I was most impressed with the K2. Its output scaled very well with current. While the scaling with current up to about 1500 mA was about the same as similar products from Cree, above 1500 mA was where the K2 shined (pun intended). Cree XR-Es typically level off in output once current gets slightly above 2000 mA. The K2 neutral white increased in output up to 2600 mA. It may have done even better if I had soldered it to the heat sink instead of using Arctic Alumina thermal epoxy. Peak output at 2600 mA was close to 285 lumens. Granted, this is only 14% more than the 1500 mA output, but it nevertheless indicates superior ability to deal with the thermal effects of higher current.
Lumileds K2 TFFC cool white -220 (acquired July 2009)
This is the highest available bin of Lumiled's cool white K2 presently available. The 220 lumen spec is at a drive current of 1000 mA. Here are the results:
Color temperature is around 6000K and appears snow white, with no discernable tint. The K2 TFFC cool white 220 exceeds the spec at 1000 mA with over 227 lumens. Lumileds specifies typical figures of 105, 185, and 300 lumens at 350 mA, 700 mA, and 1500 mA, respectively. The test results at these respective currents were 101.8, 175.8, and 292.8 lumens, all less than but still within a few percent of specification. Vf at 350 mA is 3.28 volts, and only rises to 4.18 volts at 3100 mA. This again brings me to how well the output scales with current. The K2 cool white kept right on rising in output all the way to 3100 mA! It may have done even better if I had soldered it to the heat sink instead of using Arctic Alumina thermal epoxy. Peak output at 3100 mA was 390 lumens. This was over 33% more than the 1500 mA output. Good things are definitely occurring with the K2 TFFC's thermal management. Also interesting to note was that 350 mA efficiency was 88.6 lm/W. If Lumileds comes out with a -250 bin, then it should equal the Cree R2 at lower currents, and have dramatically better output at higher ones. Also noteworthy is that I accidentally spiked the current to about 3.6 amps with no ill effects on the emitter. The K2s are evidently quite robust.
Here is a chart of lumens versus current for the two K2s:
I also ran some tests under typical flashlight conditions. I decided to go with a 60°C constant baseplate temperature for these tests to simulate conditions in a typical flashlight. I used one of my thermoelectric cold plates in heat mode for my testing. Here are the results:
K2 Cool White -220
K2 Neutral White -180
LEDEngin LZ4-40NW10
The results are pretty much what I thought they would be except for the K2 neutral white. The K2 cool white lumens output more or less tracked the output at room temperature across the entire range, except scaled by a factor of roughly 92% to 94%. Same thing for the LEDEngin except the scale factor was closer to 90% over most of the range (although it did rise to 96% by 1300 mA which I thought was strange).
The K2 neutral white started out like the other two, holding at roughly 94% to 95% of room temperature output until maybe 1.7 amps. Above that the output dropped like a rock as seen in the chart. Yet at room temperature output continued to rise until about 2.6 amps (although this was still less than the 3.1 amps managed by the K2 cool white). Only thing I can think of here, since the dice are likely the same, is the phosphor. Perhaps the neutral white phosphor is a lot more temperature sensitive. That would explain my results here, and also to a lesser degree the results at room temperature where the neutral white maxed out at a lower current than the cool white.
Just for kicks after I finished these tests I put the thermoelectric back into cooling mode. I managed to get
463.7 lumens out of the K2 cool white at a plate temperature of 0° C and a drive current of 3100 mA. I was even able to get
328.6 lumens at the maximum rated current of 1500 mA by cooling the base plate down to -12.5°C ( 9.5°F).
09-26-2009
Here are the results of my most recent round of testing:
Seoul Semiconductor N42182L bin S2SL0H warm white high CRI star (acquired September 2009)
This is the first high-CRI LED I've tested. The S2 flux bin is speced at 60 to 70 lumens at 350 mA, and the SL0 tint bin is between 3250K and 3500K. Here are the results:
The N42182L slightly missed the S2 bin at 58.5 lumens at 350 mA. However, this is only marginally low, and likely within the margin of error of my tests. Vf is a low 3.08 volts at 350 mA, rising to 3.35 volts at 1000 mA. Efficiency at 350 mA is a pretty decent 54.2 lm/W given the nature of this LED (lower CCTs and high CRI both significantly reduce luminous flux). CCT did indeed appear to be in the low-middle 3000s as per the spec. Color rendering, especially with warmer colors, was much better than that of cooler LEDs. The N42182L didn't do particularly well at higher currents. Output peaked at 111.3 lumens at 1000 mA, only 1.9 times the value at 350 mA. This seems to be part of a general trend I'm noticing where warmer-tinted LEDs don't scale as well with current as their cooler cousins. It may have to do with the phosphor used perhaps being more sensitive to heat. There are certainly greater Stokes losses, which in turn translates into heat, in a phosphor outputting more longer wavelengths.
Lumileds Rebel neutral white -100 (acquired September 2009)
This is the highest available bin of Lumiled's neutral white Rebel presently available. Here are the results:
Color temperature looks to be around 4500K. This is no surprise. Due to nature of LED manufacture at present cooler bins tend to emit more output, and therefore the cooler binned neutral whites will be most likely to hit the -100 spec. The -100 neutral white actually falls a little short of the spec, coming in at 98.6 lumens at 350 mA. However, the margin of error in my testing likely exceeds the amount that the spec was missed. Vf at 350 mA is a very low 2.97 volts, and rises to a mere 3.30 volts at 2000 mA. Output with current scales even better than the cool white Rebel -100 I tested last year, and maxed out at 288.3 lumens at 2000 mA. Despite marginally missing the spec, efficiency at 350 mA is 94.9 lm/W (compared to 98.2 for the Rebel -100 cool white) due to the very low Vf. Overall the Rebel is slowly but steadily improving.
Cree MC-E bin K tint 4A (acquired September 2009)
I finally received an MC-E to test courtesy of
saabluster! The K flux bin is 370 to 430 lumens at 350 mA per die, and the 4A tint bin is 4500K to 4750K. Here are the results:
I connected the dies in series as it was the easiest way for me given my power supply. As can be seen, the MC-E falls right in the middle of the K bin with 403.7 lumens at 350 mA. Efficiency at that current is an excellent 93.6 lm/W. Vf at 350 mA is a low 12.32 volts, or 3.08 volts per die. Output peaks at 915.2 lumens at 1200 mA. Vf at 1200 mA is 13.37 volts ( 3.3425 volts per die), and efficiency is a pretty decent 57 lm/W. CCT does indeed appear to fall into the 4500K to 4750K range. Overall, this is a very nice LED which handily meets specs, and provides an output sufficient for general lighting.
Luminus Phlatlight SST-90 (acquired September 2009)
Along with the MC-E,
saabluster sent me a Phlatlight SST-90 mounted on a copper slug for testing. The SST-90 is a single die LED using a huge die of roughly 3mm x 3mm. Multiple bond wires and photonic lattice technology enable even surface current distribution. The die is bonded to the thermal pad with a resistance of only 0.64°C/W. The SST-90 is speced at 3.2 amps. After using my usual test apparatus to plot the radiation pattern I mounted the SST-90 on a fan-cooled Pentium 4 heatsink. It was obvious given the specs of this LED that the smaller extruded heat sink on my test apparatus would not be up to the task. I had installed a temperature sensor in the P4 heatsink for testing thermoelectric modules. This would come in handy and allow me to determine the LED's slug temperature. The thermal resistance of this heat sink is about 0.24°C/W. Therefore, the total thermal resistance between the die and ambient should be around 0.24 + 0.64, or 0.88°C/W. Without any further ado, here are the results:
As can readily be seen, the SST-90 is impressive. Output at the rated current of 3200 mA is 925.4 lumens, Vf is 3.48 volts, and efficiency is 83.1 lm/W. To put things into perspective, the closest competitor to the SST-90 which I tested was the Seoul Semiconductor P7. At the same current the P7 only managed 842.6 lumens and 72.3 lm/W. As current rose, the SST-90 only increased its lead. The P7 ran out of steam at 7 amps and 1195.8 lumens. The SST-90 managed 1782.9 lumens, or 49% more, at the same current. By that time, I was muttering Will Smith's line from "Men in Black" when he fired off the big laser gun: "Now that's what I'm talking about". On the other end of the current scale, behavoir at low currents was very interesting. The die doesn't even emit light until drive current reaches 13 mA. Efficiency starts out low, and doesn't peak until 500 mA. It remains above 100 lm/W in the 350 to 700 mA range. And it falls very slowly, remaining above 60 lm/W even at the maximum rated current of 9 amps.
The SST-90 bought me into uncharted territory in terms of output and drive current. I continued to ramp up the current, expecting that eventually it would run out of steam and output would level off, but output kept increasing. I started telling my power supply in Star Trek fashion "Can you give us any more?" (anyone remember that line from the first Star Trek pilot?). By the time drive current hit 11.75 amps the answer was no, but the SST-90 would gladly have taken more if the power supply could have given it. Vf at 11.75 amps was still only 3.95 volts while output was 2530 lumens! And as can be seen in the lumens versus current chart, output wasn't even close to leveling off. I think the SST-90 could have exceeded 3000 lumens at perhaps 15-16 amps, assuming the bond wires were up to the task. However, since this SST-90 was a loaner, I wasn't about to try to parallel supplies to get more current into it. 2500+ lumens was impressive enough, as was 2136.3 lumens at the maximum rated current of 9 amps! And for good measure, intensity at 1 meter exceed 1000 lux. I dread to think about the intensity the SST-90 can put out with a suitable aspheric.
10-10-2009
Cree XP-G bin R5 (acquired October 2009)
A package containing my XP-Gs arrived from Cutter today. I had ordered R4 bins but Cutter substituted R5s. Naturally, the first thing I did after opening the package was to set up my test jig. The R5 bin is specified as 139 to 148 lumens. Color temperature of my sample appeared to be roughly 6500K. The XP-G was rather difficult to set up for testing due to its form factor. I mounted it on a PCB I had made for Rebels. It was necessary to modify the board a bit due to the different pad layout. I then thermal epoxied this on to a brass tab which was bolted onto my test jig. I'll admit the thermal path could have been a little better, but it didn't appear to affect test results very much. Here are those results:
Beam angle is 125.4°, Vf at 350 mA was only 3.01 volts, output was 145.4 lumens (well within the R5 bin), and efficiency was an amazing 137.8 lm/W! Owing to the larger die size, output and Vf scaled very well. Vf at 700 mA was 3.17 volts, output was 265.3 lumens. The corresponding numbers at 1000 mA were 3.26 volts and 351.1 lumens. Output at 1000 mA relative to 350 mA was 2.415, a bit short of the roughly 2.48 in the spec sheet. However, I'll attribute this small difference to my fairly lousy thermal path. Despite this, output continued to rise with current well past 2 amps, peaking at 546.6 lumens at 2500 mA! My previous highest result for a single die normal-sized emitter was 436.7 lumens, also at 2500 mA, for a Cree XR-E R2 mounted on a heat pipe and copper block. I've little doubt the XP-G could break 600 lumens on a similar setup. Another amazing thing was that efficiency remained above 100 lm/W until 1200 mA. Even at 2000 mA it was 77 lm/W.
It has been mentioned that the XP-G's superior performance can be attributed solely to a larger die size, as opposed to a better die. My test results also indicate a superior die. This is evidenced by the higher peak efficiency of the XP-G, as opposed to the best-binned XR-Es. My best result for an XR-E was 148.3 lm/W at 20 mA. The XP-G peaked at 157.6 lm/W between 60 and 80 mA. The chart below is further evidence of this. The red line is a plot of lumens versus current for the XP-G. The white line is a plot of lumens versus current for two XR-E R2s in parallel. Two XR-Es in parallel roughly simulates the die size of the XP-G. Note that the XR-E R2s I tested mostly likely have the larger die size Cree was using, prior to switching over to a slightly smaller size, due to the fact that I tested them in June 2008. This makes the comparison valid. Note how the XP-G outperforms two XR-E R2s in parallel up to roughly 1700 mA. Above that the XR-Es have an edge owing to their superior thermal path (heat pipe and copper block as opposed to brass tab and thermal epoxy).
Also interesting to note is that the XP-G outperforms 4-die emitters such as the MC-E up to roughly 1500 mA. Even at 2000 mA the XP-G managed 528.7 lumens, while a K bin MC-E I tested only managed slightly more, 538.5 lumens, at 500 mA per die. Granted, an M-bin MC-E would do somewhat better, but even there the difference wouldn't be huge.
Overall, the XP-G is another quantum leap in performance from Cree.
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27.07.2010, 17:46
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), при разной подводимой мощности.
