Simplified Daylight Spectrum Approximation by Blending Two Light Emitting Diode Sources
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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Energy-conscious facility designs strive to include natural daylight in workspaces. To improve the efficiency of illumination, significant efforts are underway to adopt more efficient light emitting diode LED lamps and to effectively integrate daylight with active dimming of electric lighting. However, the correlated color temperature CCT and spectral content of daylight varies throughout the day while existing electric light sources produce light with a fixed CCT, resulting in mixed-illumination environments. The color rendering requirements for a lamp that permits the selection of color temperature across a significant portion of the daylight locus is explored. The analysis indicates that it is possible to form a lamp having only two independently controllable groups of narrowband emitters that is capable of producing light that achieves a nearly colorimetric match to daylight from 4000-10,000K. A prototype LED lamp, with a simple control and novel drive scheme, which produces white light over a range of CCTs by blending light from a pair of sources, each with numerous, tuned LED emitters, is demonstrated. The prototype validates the lamp concept -- producing light over a broad range of CCT values 4000-8000K while maintaining a stable color quality rendering score without requiring computations for spectral approximation once employed.
- Electrooptical and Optoelectronic Devices
- Air Conditioning, Heating, Lighting and Ventilating