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.