The votes are in, and readers have selected Cree’s XR-E series power LEDs as the most significant Leapfrog technology story of the year (see “White Power LED Lights The Way With A 160-Lumen Output,” Nov. 16, 2006, p. 39). And Cree has come a long way in improving the XR-E series since that story broke.
Improvements in the die, packaging, and materials have led to the company’s Cool series. These lights are “a more efficient version of the XLamp series and exhibit good color stability over the LED’s lifetime,” says Deb Lovig, Cree’s Program Manager for the firm’s LED City Initiative.
COOL SPECS
The lamp now produces a cool white light output of up to 250 lumens—a 56% improvement. It’s available in a cool white output (5000K to 10,000K color-corrected temperature, or CCT) with up to 114 lumens at 350 mA with an efficacy of over 90 lumens/W.
Also, Cree developed its Warm series for general use in indoor lighting, though it’s being used overseas for outdoor applications as well. Neutral and warm white versions (3700K to 5000K CCT) with outputs with up to 80.6 lumens at 350 mA feature an efficacy of up to 67 lumens/W, the same efficacy and color temperature of a compact fluorescent lamp (CFL).
“These are the best results reported for packaged, high-power LEDs,” says Paul Scheidt, product manager for Cree’s solid- state lighting products. The National Institute of Standards and Technology (NIST) has verified the results.
The white power LED chip is produced on a silicon-carbide (SiC) substrate that has an indium-galliumnitride (InGaN) epitaxial layer grown on it. The reflow-soldered surfacemount chip features a small footprint of 7 by 9 mm (Fig. 1).
Solid-state light sources are more efficient and have longer lifetimes than conventional light sources. They don’t require much maintenance either, making them a cost-effective alternative for a number of general illumination and back-lighting applications. As a result, applications are spreading quickly in office buildings, parking lots, outdoor and indoor lighting, auto headlights, garage and warehouse low-bay illumination, camera-flash and projection displays, and even flashlights.
In fact, LED lighting has made the parking lot and lobby at Cree’s headquarters in Durham, N.C., a lot brighter (Fig. 2). More and more lighting fixture manufacturers are using Cree LED light sources in their products for use in industry and the home.
ON THE STREETS
According to the U.S. Department of Energy (DOE), 22% of electricity used in the U.S. powers lighting. The DOE claims that in the next 20 years, rapid adoption of LED lighting in the U.S. can reduce electricity demands from lighting by 62%. Also, it could eliminate 258 million metric tons of carbon emissions. It could prevent the building of 133 new power plants. And, it could result in financial savings that could exceed $115 billion.
Proof of this is the LED City initiative. Toronto, Ann Arbor, Mich., and Raleigh, N.C., have joined this expanding organization of government and industry parties working to evaluate, deploy, and promote LED lighting technology across the full range of municipal infrastructures. Its goal is to save energy, protect the environment, reduce maintenance costs, and provide better light quality for improved visibility and safety.
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