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Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next PageABE FMaGSluminaires | COLOR CONTROLmatched to the values achieved by incandescentor halogen lighting. However, in mostcases the low color-binning yield leads to alarge percentage of LED modules with undesirablecolor chromaticity.In order to improve colorbinning yield, some manufacturerssuch as Osram andCree employ in situ sorting ofLED die for wavelength andflux during fabrication, followedby chip-level depositionof conformal layers ofphosphors to improve coloruniformity, while others suchas Philips Lumileds employmatched phosphor plateletspositioned on the surface ofthe LED die.In the case of multiplechipLED modules (examplesinclude PerkinElmer’s Aculedand Osram’s Ostar), the lightfrom red, green and blueLEDs is mixed to provide thedesired white light emissionor other color schemes. Theseare typically only employedfor projection, and architectural,decorative and mood lighting,rather than general lighting. They sufferfrom poor color fidelity and chromatic discrimination(typical Ra values are 70–80),due to the non-continuous superpositionof narrow band RGB spectra forming thewhite spectrum, as well as poor overallsystem efficiency. More recent colorchangingmodules, such as those fromPerkinElmer and Enfis, have increased thenumber of different primary colors by theaddition of amber LEDs while also mixingwhite LEDs to improve CRI, chromaticity,color gamut and overall efficiency, and toenable the modules to function for bothdecorative as well as general lighting.The primary drawback of these LEDmodules is that each LED semiconductorages differently and hence tends toshift the color temperature with lifetimeas well as temperature. In order to alleviatesome of these problems, luminairemanufacturers such as Cree LightingSolutions (formerly LLF Inc) and Philips(with its Lexel and Color Kinetics Intelliwhiteproducts) have adopted system-levelsolutions combining both white LED modulesand/or single color LEDs as well as feedbacksystems that continually monitor and adjustthe CCT and color chromaticity.PhotonStar LED Ltd has adopted a novel systemlevel approach to solve some of the issues,Warm white Neutral white Cool whiteFIG. 2. Color-changing capabilities of the ChromaWhite LEDmodule embedded in a standard PhotonStar CeilingStar5recessed downlighter with a CCT and intensity controller box.The luminaire is running off two 9V batteries.RGB LED 6000K CRI 70 Fluorescent - 2700K CRI 80PhotonStar module - 3500K CRI 95 Incandescent - 2700K CRI 100FIG. 3. Demonstrating the importance of CRI through the irradianceof colored objects using a variety of light sources.and has implemented this at the LED modulelevel, enabling a unified single-LED modulefor use in general lighting applications aswell as color-changing applications. The multichipLED module employs system and dielevel corrective and preventative mechanismsto enable high efficiency (currently exceeding80 lm/W at 4000 K and reaching over 100 lm/Wfor higher CCT) and excellent color fidelity (Ra>95) as well as ability to shift the chromaticityto suit the lighting application. It is importantto note that there are no limitations in theunderlying efficiency of the LED module technologyand this will continue to match stateof-the-artcommercial fixed wavelength whiteLED module efficiencies.The ultra-low thermal resistance of the PhotonStarLED ChromaWhite LED module (
Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next PageABE FMaGSHIGH BRIGHTNESSHIGH EFFICACYHIGH RELIABILITYCOLOR POINT STABILITY50,000-HOUR LUMENMAINTENANCELighting-Class LEDs.Cree XLamp ® LEDs.Bright + EfficientLuminous flux up to:251 lumens at 1A114 lumens at 350mAEfficacy up to99 lumens per watt50,000 hours at >70%lumen maintenance2,600K to 10,000K CCTLeading the lighting revolution. Cree XLamp LEDs deliver lightingclassperformance that transforms ordinary light into bright, energy efficientlight. Available in warm to cool temperature ranges, Cree XLamp LEDs arepowering general illumination applications offering significant energy andmaintenance cost savings.Contact a Cree Solutions Provider or authorized distributor about yourlighting-class application at www.cree.com/xlamp or call +49 89 5484 2200.Cree XLamp LEDPrevious Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next PageABE FMaGS
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