Advancements in technology have seen them move from stop lamps, to interior, to side marker lighting and onto the rear of the vehicle in tail light applications. They not only offer flexibility in design, but a vehicle with full LED lighting offers a potential 80-watt energy savings over one equipped with conventional bulbs. To engineers searching for power to run all of those new telematics features, that's a big energy savings.
LEDs are a perfect lighting source for rear combination tail lamps because the red and amber lights don't need to be filtered through colored plastic. A red LED offers a 10 to 15 percent energy saving over a red-filtered incandescent bulb. And LED manufacturers are developing ways to make them brighter.
With LED tail lamps becoming more prevalent, how long before we see LED-powered forward lighting?
Most experts agree they are in the near future.
"I think that you could make a legal lamp now," says Michael Godwin, product marketing manager for Osram Opto Semiconductors. 'The technology is there in terms of lumen output and brightness."
"It's not far away at all," adds Jim Loeffler, automotive sales manager for Lumileds, an LED manufacturer. "By 2007" the technical and commercial feasibility will be there to get it done."
Ron Steen, director of lighting R&D for Schefenecker sees production LED head lamps available by 2006 as standard equipment on premium segment vehicles.
"I see this as the opportunity to do something really unique on the front end," Steen says.
Jason Bonin, vice president for business development lighting technology, Hella North America, agrees, saying the industry may see a couple of cars coming into the market with LED headlamps by 2005 or 2006. But he says that the technology could show up in forward signal and auxiliary lighting applications within the next 18 months. "It's already been established and proven as concepts," Bonin says.
Guide Corp. and Lumileds showed a concept LED headlamp at SAE this year and DMB Refelx, a Quebec, Canada-based automotive lighting manufacturer has built prototypes for both Visteon and Valeo.
The Cadillac 16 concept, shown at this year's Detroit auto show was equipped with LED head lamps that Steen says are very similar to the prototypes that his company is working on with General Motors.
Theoretically you could make an LED today that's as bright as a halogen bulb. But the conditions to do that would require the LED to be driven at a very high power level. The kind of heat generated at that power level would be fatal to an LED, so the heat needs to be dissipated. The answer is to create an LED package and implement that package into a lamp system that's very thermally efficient. The more heat you draw away, the higher you can drive the power.
There is also the issue of optical performance--creating LED lighting that meets the SAE and ECE standards for beam patterns.
"You can't just flood light like a spotlight," Godwin says. "You have to be able to cut the light off to meet the beam pattern."
The only way to get an LED headlamp on the car is by having really high-efficient optics. Steen says that a traditional HID source is about 30 percent efficient, producing 3,000 lumens at the source but only putting about 800 on the road. A halogen bulb has about 1,000 lumens available, and can effectively put 300 on the road.
"We're trying to get about 70 percent efficient optics," Steen says. "The only way that you do that is by having extremely tight tolerance on the LED. The tolerance issue is going to be a significant one for the auto industry."
LED lighting is unique because the performance of the technology is being driven by the LED suppliers, not by the auto industry.
"HID and halogen lighting are principle automotive applications," Bonin adds. "LEDs are being born out of other applications, be it medical, commercial or residential. The environmental requirements of a typical automotive headlamp are so significantly different than any industrial, residential or general lighting application. And that's why it's a strategic issue to establish a supply chain for automotive lighting"
But the rapid growth of commodity lighting will help lower the cost of the technology--a fundamental issue that Bonin says is the only thing hindering the implementation of LEDs in forward signal and auxiliary lighting applications.
Author: John Peter
Previous article: 31 October 2007
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