From their modest beginnings as dashboard indicator lamps, LEDs have marched through one automotive application after another, replacing incandescent bulbs in the car's interior and exterior. LED market data attests to the current popularity of LEDs in automotive designs.
According to Robert Steele, the director of Optoelectronics at Strategies Unlimited, a firm that tracks LED usage across multiple industries, about $480 million worth of LEDs were sold into automotive applications last year. About three-fourths of the LED sales went to interior applications, mainly in the instrument panel, while the remaining one-fourth went to exterior applications, primarily the center high-mounted stop lamps (CHMSLs). Steele noted that about 40% of the cars produced last year used LEDs in the CHMSL and 4% employed LEDs in the rear lamp assembly.
We can expect that those numbers will only grow over time as LED costs continue to fall year by year. And just as drivers are noticing more and more LEDs in the stop, turn and tail lights, they may also start to see some novel headlamp designs built from LEDs. Although LED headlamps have been shown off in concept cars for several years, recent news indicate that they may finally be ready for production vehicles.
Among the telltale announcements was Visteon's introduction of what it called “the industry's first road-worthy application of LED front lighting” at the SAE World Congress in April. Using unique optics and a new method of light source placement, Visteon's product directs the light from white LEDs into the beam patterns required for high beam, low beam, daytime running lamps or fog lamps.
Various sources predict that white LED headlamps could appear in production vehicles within two years. While there are no fundamental technical hurdles to prevent the commercialization of LED-based front lighting systems, the engineering challenges are not trivial. Thermal management requires careful attention as designers must manage the heat generated by the LEDs in the face of the high ambient temperatures encountered under the hood. LED drive currents must be accurately controlled to control light intensity under different operating conditions.
The benefits of adopting LEDs in front lighting are the familiar ones associated with LED use in general. LEDs last much longer than incandescents, are more rugged, and consume a fraction of the power. With manufacturers of high-brightness LEDs specifying operating life of 50,000 hours or more for their components, an LED headlamp should not normally wear out. But is longevity enough to justify the high cost of LED headlamps, which may initially be on par with HIDs?
Probably not, but automotive styling may warrant the move to LEDs. The physical limitations of halogens and HIDs do not apply when designing LED headlamps, which are fashioned from arrays of low-profile, individually packaged LEDs. These individual LEDs are assembled on substrates that may be curved and formed into interesting geometric patterns, radically altering the look of the vehicle.
LED manufacturers are certainly eager to see their products adopted in automotive front lighting given the huge market potential. Naturally, it will take years of continued LED development before LED front lighting matures enough and is cheap enough to become pervasive in cars and light trucks.
But the long-term trend toward LED usage is hard to deny. In addition to the lighting applications already mentioned, some carmakers are using them in turn signals and turn signal repeaters on mirrors. Interior applications are moving beyond the instrument panel to map lights with dome lights and safety lights as other potential uses in the near future.
“In the next few years, you could see cars with 100% LED lighting inside and out” said Steele. This prospect bodes well for those designing the electrical systems within new vehicles. Unlike many of the electronic and electromechanical subsystems appearing in new vehicles, LEDs will actually lower requirements for electrical power. But as with other benefits, the cost of reduced power consumption may be greater complexity in the lighting control circuitry.