2013年7月30日 星期二

Differing requirements

The basic function and interchangeability of filament and discharge lamps for road vehicles differ from those of LED light sources. The former types must comply with the IEC 60809 International Standard that defines the dimensional, electrical, and luminous requirements of lamps for road vehicles. In particular, this standard defines the markings, bulbs, dimensions, colors, caps, and bases.

LED light sources, which are based on modules (LED components used by the industry), are not covered by IEC 60809 but by other IEC standards specific to LED modules. However, another International Standard, IEC 60810, which sets out the performance requirements of lamps for road vehicles, applies to the three types of lamps.

LED light sources must meet conditions that do not necessarily apply to filament and discharge lamps, in regard to UV radiation, color maintenance, and electromagnetic compatibility. As LED light sources have a longer rated lifetime than filament or discharge lamps, their lumen maintenance is assessed differently.

Another issue that manufacturers have had to deal with is thermal management, and LED modules and light sources often come with integrated heat sinks. Unlike their filament and discharge counterparts, LED light sources are mainly of the non-replaceable type and are usually intended as components for integration into the luminaire or lighting device by manufacturers. They are designed and meant to be indivisible parts of a lighting or light signaling device, or to be elements of a module or light engine. The auto industry has developed replaceable LED modular sources, usually intended for sale to the general public as a replacement part.

LED light sources can replace all other types of automotive lamps

. They are available for headlamps (high and low beam), brake lights, rear combination lamps, center high-mount stop lamps, daytime running lamps (DRLs), turn signals, interior reading lights (map lights), dome lights, accent lights, fog lamps, and position and marker lamps. Moreover, LEDs are being used for ambient lighting and in dashboard and instrument lighting.

In addition to enhanced driving safety and comfort, LED light sources offer many other benefits:

Lighting flexibility: Lighting requirements and limitations vary greatly according to traffic conditions. LED lighting solutions allow the optimal use of environmental and traffic-related dynamically controllable light distribution patterns such as dynamic bending of light or adaptive front lighting systems (AFSs), already used for other types of automotive lamps. Such adaptive lighting is particularly important to avoid blinding other drivers when crossing or following other vehicles, especially in curves, or to better see fixed or moving obstacles on road sides. LED lighting sources are also dimmable.

Durability and efficiency: LEDs for automotive lighting have a much longer rated lifetime and use less energy than filament or discharge lamps. LEDs are up to 40% more energy efficient than the former sources. Since less energy for lighting translates into lower fuel consumption, this is a significant feature at a time when tighter consumption and emission rules are introduced in all countries even though road vehicles are required now to use DRLs.

Design flexibility: A very important benefit of LED lighting solutions for car manufacturers is the design flexibility they offer. Car design bureaus have much greater freedom to come up with innovative designs using lighting to accentuate or attenuate certain shapes and give cars a common brand signature. LEDs were first fitted to vehicles from the exclusive segment of the market, but they are found now in all classes of cars.

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