LED Outlook Brightens

DN Staff

April 18, 2005

6 Min Read
LED Outlook Brightens

Nick Holonyak has predicted nothing short of a transformation in lighting ever since the mid-60s, shortly after he discovered how to get semiconductors to emit light. These days, he still gushes when he's asked about the future of LEDs, which he invented in 1962.

"People have never before had the choices in color variations, where they could do so many things with size, form, and layout to put any color of light anywhere, and do all that more efficiently so they're saving energy and reducing their costs," says Holonyak, now a professor at the University of Illinois in Champaign.

This slow transformation is picking up steam as LEDs improve brightness and come down in price. The emergence of white LEDs is helping the technology displace incandescent bulbs, a shift that's also being driven by pricing declines and higher light output.

Companies such as Color Kinetics Inc. of Boston are working with architects, theater set designers, and many others who are making Holonyak's dream come true. Color Kinetics' hardware illuminates a broad array of building interiors and exteriors, ranging from the Hard Rock Hotel in Las Vegas to Philadelphia's Ben Franklin Bridge to the Overture Center for Arts in Madison, WI. The Rock Styles exhibit in New York's Museum of Modern Art and the Boston Ballet's Nutcracker presentation also rely on solid-state lighting.

Various color LEDs can be placed in hidden locations, letting architects and set designers change moods and appearances easily. "Places that never dreamed of color changing now routinely ask it, in theaters, on bridges, and in government buildings," says Ihor Lys, co-founder and chief technology officer of Color Kinetics.

Simplified color variations are only one reason growth is surging. "They're smaller, have 10 times better life, better performance, and use less energy than incandescents," Holonyak says. They also meet new ecological regulations that ban mercury and lead.

Volume consumer applications go far beyond the simple alarm clock LEDs used for decades. Now, they're being used for backlights in LCD TVs, replacing cold cathode fluorescents. Sony and Samsung are starting to use red, green, and blue LEDs to improve TV color quality and increase brightness. "Using red, green, and blue arrays gives you stunning color with a wider gamut of colors," says Robert Steele, senior analyst at Strategies Unlimited of Mountain View, CA.

While brightness and low power consumption drive many designers, the small size of LEDS is also a factor in their growth. Mitsubishi Digital Electronics America unveiled the PocketProjector, a 14-ounce, handheld unit that uses LEDs to enlarge images stored in computers, cameras or even handheld games. Red, green, and blue LEDs display an SVGA image that can measure 40 inches when the display surface is less than a yard away.

Technical advances

The rapid increase in usage is sparking an increase in R&D around the globe. White LEDs are only a few years old, but they're already reaching brightness and pricing levels needed by the demanding automotive industry. Holonyak notes that over time, white LEDs will be made with simpler processes, bringing pricing down even further.

A recent example of current technical progress comes from Lumileds Lighting of San Jose, CA, a joint venture between Agilent Technologies and Philips Lighting. White versions of its recently upgraded Luxeon technology now emit up to 65 lumens at only 350 mA, or about 60 lumens per watt. That's roughly four times the output per watt of a conventional incandescent bulb.

Increasing brightness is critical for both total effect and for reducing the number of LEDs needed to light a given area. "We've always used the brightest LEDs possible; we want the most efficient lumens per watt we can get," Lys says. That's especially important with white lights, "which pretty much always run at full power," he adds.

The Luxeon line also has a junction temperature of 185C, 50 degrees higher than the previous generation. That is seen by some as a major breakthrough. "There's almost been a law of physics that says you couldn't exceed 125C," Steele says.

It should help white LEDs crack into automotive applications, which have more stringent ruggedness and reliability requirements than many fields. "This eliminates any concerns about temperature," said Jeff Raggio, automotive business development manager at Lumileds.

Another benefit of improvements like these is that when brighter LEDs can be run at full power, fewer are needed. Market watchers generally agree that high brightness LEDs will make up the bulk of future growth. Strategies Unlimited predicts that segment will nearly double last year's $3.7 billion by 2009, when revenues could hit $7.2 billion.

In large applications, the shift to increasingly brighter lights can mean a reduction in overall power and heat budgets. Using fewer high-efficiency LEDs reduces the need for fans, which are noisy and reduce reliability. "We do whatever we can with passive cooling, using thermally conductive epoxies and all sorts of things to get heat out," Lys comments.

Improvements with LEDs sometimes take dramatic leaps, but for the most part, they follow a familiar path, advancing steadily along a course similar to that of conventional semiconductors. "Globally, there's a road map that foresees output of 150 lumens per watt by 2012," says Nadarajah Narendra, solid state research director at the Lighting Research Council at Rensselaer Polytechnic Institute in Troy, NY.

The research endeavors are international, as are efforts to build a manufacturing base for a technology with huge growth potential.

"China is very interested at the highest levels of government," Steele says. LEDS are seen as a partial solution for China's energy problems, he explained.

"Korea, Taiwan, and China are all gearing up LED manufacturing operations," Narendra adds.

Chipmakers are also helping enable the transition. Color Kinetics was recently able to reduce the number of components in a system by using Microchip controllers that add a DSP core to the main processor. "Our older line had about 150 parts. We're able to get that down to 100 and reduce costs a fair amount, since some of those components are pricey," Lys says.

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