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LEDs Gaining Ground in Automotive Applications
Efficiency and brightness are keys to rising popularity
Charles J. Murray, Senior Technical Editor -- Design News, June 25, 2009
The light-emitting diode (LED), a relative newcomer to the century-old automotive lighting market, may finally be gaining ground on the venerable incandescent bulb.
A new breed of brighter, less costly, more efficient LEDs are making their way into a wide variety of automotive applications, ranging from center high-mount stop lamps (CHMSLs) and turn signals to vehicle cockpits and headlights. Moreover, applications for the technology are growing in unexpected ways. The 2010 Ford Mustang, for example, will use an LED-based feature called MyColor, which allows drivers to customize the interior lighting of the Mustang to suit their moods. Similarly, Kia Motors' Soul has employed LEDs in its sound-reflecting speaker lamp (watch a video of it), which responds with variable light to the beat of the music that's playing on the stereo.
"More and more automotive functions are using LEDs," says Viren Merchant, engineering manager for exterior electronics at Visteon Corp., a tier-one automotive electronics supplier. "In the beginning, its was just CHMSLs. Now it's everything from backup lights to rear fogs to daytime running lights."
Engineers say the growing popularity of these electronic lights, which are based on the semiconductor diode, is the result of several trends. Newer, brighter designs are said to be about 10-20 times more powerful than the products of five years ago. A few LED products now offer in excess of 50 lumens/W – in some cases as much as 100 – whereas many products a few years ago offered less than five. Meanwhile, electric vehicles and hybrids need power-efficient lighting, which boosts the appeal of LEDs. At the same time, the cost of LEDs has gradually dropped over the last five years.
"Five years ago, there were no LED headlights," says Richard Vaughan, design manager in the Innovation Group for Visteon. "Today, LED headlights are optional on some high-end cars. And as the cost continues to come down, we'll see the proliferation of the technology in less expensive models."
To be sure, less than 2 percent of headlights are estimated to use LED technology today. But suppliers say that more than 80 percent of Asian cars use LED-based CHMSLs. Similarly, more than 70 percent of European cars and about half of North American cars are employing LED-based CHMSLs. On the exterior of the vehicle, automakers are also using LEDs in daytime running lamps and parking lights, as well as the high- and low-beam headlights.
In anticipation of increased use of LEDs in headlights, Osram Opto Semiconductors rolled out the Ostar Headlamp LED in November. The product is equipped with one to five semiconductor chips, in an effort to make it usable in a variety of different headlamp sizes and shapes. Depending upon the number of chips used, the unit produces from 1 to 25 lumens at 700 mA (one chip) to 1,000 lumens at 1 A (five chips).
Tier-one suppliers say the design flexibility of the LED is a key to its growing popularity. LED packages can be altered to incorporate different numbers of chips, as well as different shapes and sizes. Automakers such as Cadillac, for example, have used that flexibility to create unusually shaped CHMSLs and tail lamps.
"It's a way to communicate to the consumer," Vaughan says. "Designers can achieve the shapes and length patterns that consumers can see and identify."
In that sense, LEDs are helping automakers create greater brand awareness, in the interior, as well as the car's exterior. Osram, for example, has rolled out LEDs of various colors – including ice blue, blue lagoon, sky blue and blue green – which enable automakers to tune the interior color to match their brand. In an even bolder step, Ford is employing the technology in MyColor, a system that allows drivers to change the interior colors to match their moods.
"It tunes, not only the instrument cluster, but the whole ambience of car," says Mike Godwin, director of visible LED products for Osram Opto Semiconductors.
The idea, Godwin says, is to use LED technology to enhance a car model's image. "They use the idea of color-on-demand to create a brand color," he says. "Their cockpit or their cupholder can illuminate in whatever way they want."
Tier-one suppliers and LED makers alike say that LED adoption in automotive interiors is growing fastest of all. "Every interior request for a quote we've received from every manufacturer around the world the last two years has had some aspect of LED ambient lighting to it," Vaughan says.
With the expected proliferation of hybrids and electric vehicles, LED use is expected to grow faster still over the next decade. On those vehicles, where power is at a premium, engineers are more likely to disregard cost differences and reach for LED technology. "It saves about 400-430 Watts of power across the interior of the vehicle, and about 20 Watts on the interior," Godwin says.
At the same time, engineers who want more brightness per W are getting that, too. In April, Philips Lumileds rolled out the Luxeon Rebel ES, said to be the world's first high-efficacy power LED specified to deliver a minimum of 100 Lumens per W. The new product joins earlier Lumileds entries that offered 30, 42 and 50 lumens. The new breed of brighter products is expected to take LEDs into exterior applications, such as red stop lamps, where they've been used sparingly before.
"Five years ago, a red LED was one to five lumens," Merchant says. "Today, you can easily get mid-20s in a red LED."
For now, most of the success of LEDs is being realized in luxury- and mid-level vehicles, engineers say. Cadillac's Escalade, as well as selected Lexus and Audi vehicles, are employing LEDs across the board in high-beam, low-beam, daytime running lamps and parking lights. But as prices continue to drop and automakers move to more energy-efficient vehicles, LEDs are expected to migrate toward entry-level cars.
"Incandescent bulbs aren't going away in the foreseeable future," says Merchant of Visteon. "But we do know that LEDs are here to stay."
