September 25, 2015: The US Department of Energy’s CALiPER program has released Report 23: Photometric Testing of White-Tunable LED Luminaires, which studies color-tunable LED luminaires. The study tries to understand the amount of testing required to characterize a white-tunable LED lighting product. The report states that determining a sufficient protocol required more extensive testing than would be feasible for widespread use. Eight white-tunable luminaires were tested at dozens of points covering the range of color tuning (CCT) and dimming (luminous intensity).
The report focuses on the full-intensity measurements, which were at 11 color set points covering a range of CCTs, and reveals substantial variation in input power, lumen output, efficacy, and Duv over the color-tuning range for many of the products, which would not be captured with only a few test points. The results show that future test procedures will likely require at least five to seven measurement points to provide a reasonable characterization. The increase in testing burden on manufacturers could potentially be mitigated by specifying a relatively brief measurement stabilization process between readings at different settings, rather than requiring a lengthy warmup period between readings.
Caption: Figure 1. Examples of linear and nonlinear (blackbody) white tuning. The exact curves will vary from product to product, but the key difference is that linear (two-primary) systems can only mix to chromaticities that are directly between the two primaries, whereas products with more than two primaries can be used to create mixes that approximately follow the blackbody locus.