LED HEADLAMPS

Automotive headlamp applications using light-emitting diodes (LEDs) have been undergoing very active development since 2004.

 Low beam, front position light and sidemarker functions are performed by LEDs; high beam and turn signal functions use filament bulbs. 

As LED technology continues to evolve, the performance of LED headlamps is predicted to improve to approach, meet, and perhaps one day surpass that of HID headlamps.^[48]

The limiting factors with LED headlamps presently include high system expense, regulatory delays and uncertainty, and logistical issues created by LED operating characteristics. 

LEDs are commonly considered to be low-heat devices due to the public's familiarity with small, low-output LEDs used for electronic control panels and other applications requiring only small amounts of light.

 However, LEDs actually produce a significant amount of heat per unit of light output. 

Rather than being emitted together with the light as is the case with conventional light sources, an LED's heat is produced at the rear of the emitters. 

Unlike incandescent and HID bulbs, LEDs are damaged by high temperatures; prolonged operation above the maximum junction temperature will permanently degrade the LEDs and ultimately shorten the device's life. 

The need to keep LED junction temperatures low at high power levels requires thermal management measures such as heatsinks and/or cooling fans which are typically quite expensive.^[49]

SNOW CONDITIONS

Not only must heat be removed from the rear of the headlamp so that the housing does not deform or melt, but heat must in addition be effectively applied to thaw snow and ice from the front lenses, which are not heated by the comparatively small amount of infrared radiation emitted forward with the light from LEDs.^[50]

LEDs are increasingly being adopted for signal functions such as parking lamps, brake lamps and turn signals as well as daytime running lamps, as in those applications they offer significant advantages over filament bulbs with fewer engineering challenges than headlamps pose.