26 January 2004 Quadrichromatic white solid state lamp with digital feedback
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Abstract
White light with high color rendering indices can be produced by additive color mixing of emissions from several light-emitting diodes (LEDs) having different primary colors. White Versatile Solid-State Lamps (VSSLs) with variable color temperature, constant-chromaticity dimming, and efficiency/color-rendering trade-off can be developed using pulse-width modulation (PWM) driving technique. However, such lamps exhibit chromaticity shifts caused by different temperature and aging coefficients of the optical output for primary LEDs of different colors. To overcome this drawback, we developed a polychromatic white solid-state lamp with an internal digital feedback. The lamp features a quadrichromatic (red-amber-green-blue) design based on commercially available high-power LEDs. The design is optimized to achieve high values of the general color rendering index (69 to 79 points) in the color-temperature range of 2856 to 6504 K. A computer-controlled driving circuit contains a pulse-width modulator and a photodiode-based meter. The software performs periodical measurement of the radiant flux from primary LEDs of each color and adjusts the widths of the driving pulses. These VSSLs with feedback found application in phototherapy of seasonal affective disorder (SAD).
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Arturas Zukauskas, Rimantas Vaicekauskas, Felikas Ivanauskas, Genadij Kurilcik, Zenius Bliznikas, Kestutis Breive, Jevgenij Krupic, Andrius Rupsys, Algirdas Novickovas, Pranciskus Vitta, Alvydas Navickas, Vytautas Raskauskas, Michael S. Shur, Remis Gaska, "Quadrichromatic white solid state lamp with digital feedback", Proc. SPIE 5187, Third International Conference on Solid State Lighting, (26 January 2004); doi: 10.1117/12.514079; https://doi.org/10.1117/12.514079
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