This post was written by Keith Dawson for UBM Tech’s community Web site All LED Lighting, sponsored by Philips Lumileds. It is archived here because the All LED Lighting site has gone dark. This material is Copyright 2013-2015 by UBM Americas.

2013-06-27

Cree's New High-CRI LEDs

Cree has announced additions to its CXA product line that it claims represent a big jump in efficacy for LED engines with excellent color rendering.

The vertically integrated LED lighting company announced two new LED engines, the XLamp® CXA1304 and CXA1816, that can be ordered in versions with 95-CRI, with an R9 value of 85. The company claims that the high-CRI parts "deliver up to twice the efficacy of equivalent-CRI LED light sources." We'll explore some numbers below.

The CXA1304 is a small emitter with a 6-mm optical-source size, able to deliver 300 to 1,000 lumens. The CXA1816, with a 12-mm source size, can produce from 1,300 to 2,000 lumens and can replace a 70-Watt ceramic-metal-halide spot light, according to the company.

The datasheets for the CXA1304 and the CXA1816 show identical graphs (below) for the relative spectral power distributions for the two parts (for which the high-CRI versions are specced as having a minimum 93 CRI, 95 typical).


According to Cree's datasheets, this graph is "the result of a series of pulsed measurements at 400 mA for the 9-v CXA1304 LeD and 100 mA for the 37-v CXA1304 LeD and TJ = 85 °C" for the CXA1304, which is available in two voltage levels; and at 450 mA and TJ = 85 °C for the CXA1816.

How efficient, exactly?
Wondering how these high-CRI parts' efficacy varies with color temperature, I reached out to Cree, through their PR agency, and asked if they could supply numbers to fill out the following table.

CXA1304: CXA1816:
CCT CRI
(typ.)
Efficacy,
lm/W
CCT CRI
(typ.)
Efficacy,
lm/W
5000K 75 ? 5000K 75 ?
  80 ?   80 ?
  95 ?   95 ?
4000K 75 ? 4000K 75 ?
  80 ?   80 ?
  95 ?   95 ?
3500K 80 ? 3500K 80 ?
  95 ?   95 ?
3000K 80 ? 3000K 80 ?
  95 ?   95 ?
2700K 80 ? 2700K 80 ?
  95 ?   95 ?

The answer: They are not giving out those figures in such detail. Here is what the PR agency staffer told me:

Unfortunately, we don't have this complete list publicly available. The efficacy of Cree's 95 CRI CXA is about 85 lumens-per-watt at 85°C. The efficacy of Cree's high-CRI options are slightly less than that of the CXA typical CRI LEDs (~108 lumens-per-watt) but, higher than competitive equivalent-CRI LED light sources. The 95-CRI CXA LED Arrays deliver up to twice the efficacy of equivalent-CRI LED light sources.

So here is what we have, taking a typical CCT (one wasn't specified) and assuming that the numbers given apply to both new CXA parts:

CXA1304: CXA1816:
CCT CRI
(typ.)
Efficacy,
lm/W
CCT CRI
(typ.)
Efficacy,
lm/W
3000K 80 108 3000K 80 108
  95 85   95 85

An efficacy of 85 lm/W at 95 CRI is better than that specced for the LED Engin high-CRI product we recently discussed, as blogger Ron Amok mentioned in a comment. LED Engin's product claims an efficacy of 60 lm/W, but at a higher CRI of 97.

So it's safe to conclude that Cree has advanced the state of the art in terms of efficacy at high CRI.

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