News Article

Cool-white LED Raises Efficacy Benchmark

Researchers at Cree set a new benchmark for LED efficacy with a cool-white device operating at 20mA and emitting 131 lumens per Watt.

LED manufacturer Cree has announced LED efficacy test results for a cool-white LED of 131 lumens per watt, measured at 20 mA.

The correlated color temperature was 6027 K and the results were confirmed by the US National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland.

This is an R&D result for a prototype device and does not reflect the performance of current production devices, although it certainly points the way to commercial LEDs in the near future with efficacies exceeding 100 lm/W.

Tests were performed using prototype white LEDs fabricated using with Cree EZBright™ LED chips operating at 20 mA. EZBright chips, typically measuring 0.29 x 0.29 mm, are designed to be incorporated into white LEDs which are used in backlighting applications in LCD screens on mobile phones, PDAs, televisions and monitors, as well as for indoor and outdoor LED display, camera flash, gaming and indicator applications.

Cree sells EZBright chips to external customers, and does not use these chips for internal manufacture of white LEDs. Cree s high-power XLamp LED products incorporate larger chips (1 x 1 mm). These devices are designed to operate at a current of 350 mA, and consequently have lower efficacy than the smaller-chip devices.

"This is the highest level of efficacy that has been publicly reported for a white LED and raises the bar for the LED industry," said Scott Schwab, Cree general manager, LED chips. "This result once again demonstrates Cree s leadership in LED technology and provides a glimpse into the future as to why we believe LED-based lighting products could not only save energy, but also change the way people use light."

Fritz Morgan, chief technology officer for Color Kinetics, said "Technical advancements at the component level are critical to growing the emerging white LED lighting space. Cree s results speak to the exciting developments underway that will enable new white light applications and subsequently facilitate market adoption."

Lumens-per-watt is the standard used by the lighting industry to measure the conversion of electrical energy to light. As a reference, conventional incandescent light bulbs are typically in the 10 to 20 lumens per watt range, while compact fluorescent lamps range from 50 to 60 lumens per watt.

Tim Whitaker is editor of LEDs Magazine

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