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Enhanced LEDs deliver warm white indoor lighting

Posted: 23 Mar 2007 ?? ?Print Version ?Bookmark and Share

Keywords:white LEDs? XLamp XR-E? XLamp XR-C? Cree? LED?

Cree Inc. has increased the brightness and efficiency of its XLamp XR-E and XLamp XR-C white LEDs by more than 20 percent, making them suitable for indoor "warm white" lighting applications.

"This is a performance breakthrough in the warm LED area," said Paul Thieken, director of marketing for solid-state lighting at Cree. "We've overcome some of the challenges to getting white LEDs into general illumination applications. One of them is the ability to drive into the 700mA range. This allows us to produce about 142 lumens of brightness. Another is color point stability, which is critical for lighting designers."

Warm LED
The improvements yield "a new class of warm LED that will enable a number of new applications right away," Thieken claimed.

Production volumes of the brighter white XR-E and XR-C LEDs are available immediately. Cree did not provide pricing information.

The new LEDs deliver 142 lumens at a correlated-color-temperature (CCT) of 4,000K and 124 lumens at a CCT of 3,000K when driven at 700mA. They deliver 73 or 63 lumens per watt at a CCT of 3,000K when driven at 350mA. "The competition and our previous products were producing 50 lumens and below," Thieken said. The brighter LEDs can be applied to general illumination downlighting and undercabinet lighting applications that previously relied on incandescent bulbs, he said.

Cree has steadily improved its white LEDs to broaden their application areas. It announced production availability of white XLamp 7090 LEDs in October 2006 that achieved 160 lumens at 700mA, sufficient for applications such as outdoor street lighting and low bay lighting. Warmer lighting is preferred for indoor applications.

Color point stability has traditionally proved difficult in producing warm white LEDs, but Cree said its newly available white LEDs have minimal CCT shift. "There is a measureable shift in color, but the human eye cannot detect it," said Paul Scheidt, Cree's product marketing manager for solid-state lighting.

In addition to greater brightness and efficiency, the parts are also more efficient in terms of lumens per dollara ratio that is closely watched by industry, Thieken said. Cree did not provide a lumens per dollar ratio for the new LEDs.

Cree said it has also changed the way it sorts its new LEDs, a process known in the semiconductor industry as "binning," Thieken said. "How we characterize and sell the products will be based on some ANSI standards. We produce the semiconductors and we bin in two dimensions: one is color point, the other is how much light they put out. That's a change to make it more applicable to lighting designers," he said.

Cree reported revenue of $88.8 million and net income of $16.5 million for its most recent fiscal quarter ended Dec. 24, 2006, down from $105.6 million in revenue and $17.7 million in net income in the year-ago quarter. The company earlier this month agreed to acquire Cotco Luminant Device Ltd, a Hong Kong-based supplier of high brightness LEDs, for $200 million in cash and stock. Last year the company paid $46 million to acquire Intrinsic Semiconductor Corp., a developer of silicon carbide substrates. That purchase will accelerate Cree's commercialization of 150mm and 200mm substrates, the company said.

- David Roman
EE Times

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