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White-LED chips lit for efficiency race

Posted: 17 Apr 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Yoshiko Hara? Nichia? white LED? LED?

Nichia Corp. has developed a white-LED chip with 100lumen/watt efficiency, with volume production expected this year. The move comes amid an intensifying race to boost the efficiency of white light-emitting diodes so the parts can compete against conventional lighting devices.

Nichia, a leading supplier of blue and white LED chips, has developed prototypes of a pendant light and a spotlight using the white LED.

In order to compete with fluorescent lights, white LEDs must have an efficiency of between 70lumens/W and 100lumens/W. Indeed, 100lumens/W is a milestone for white-LED players. That level had not been expected until 2008 to 2010.

While high-output white-LED chips are available, they consume more power, lowering efficiency.

One way to boost efficiency in a module or lighting apparatus is to use multiple chips. In this case, each white-LED chip does not have a large luminous-flux (lumens) output, but needs low power dissipation to realize the efficiency. Nichia developed a chip with 6lumens with an input of 20mA at 3V, achieving an efficiency of 100lumens/W.

The white-LED chip in the prototype pendant light delivers 4,536lumens with a 45W input. The spotlight consists of 80 chips, delivering 480lumens with a 4.8W input. As a lighting apparatus, each of them also had approximately 100lumen/W efficiency.

Nichia intends to start sampling the chip in June and to start volume production by year's end. The first product will come in the form of a 5mm-diameter lamp package.

White LEDs generate white light by combining red, green and blue LEDs, or by using a blue LED and yellow phosphor. Nichia is pursuing the combination of a blue LED and yellow phosphor because of a superiority in color rendering.

At this point, white LEDs are technically comparable to fluorescent lights. "The biggest bottleneck is cost," said Gen-inch Shinomiya, managing director in charge of the R&D engineering division at Nichia. If simply compared in price, a white LED costs nearly 10x more than a comparable fluorescent light. Even considering LEDs' advantagesa low operating cost and no need for additional circuitrythe cost is still several times higher than for conventional lamps.

The company estimates that 13 billion to 15 billion units of GaN-based LEDs were produced globally last year; a large percentage were low-end products.

Sharp price erosion in LEDs, especially for backlighting LCD panels, dragged down Nichia's sales by about 5 percent in 2005 from the year before. Both the Nintendo DS and Sony PSP game players use Nichia's white LED for their backlight.

- Yoshiko Hara
EE Times

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