LED automotive lighting technology and current situation analysis
As the fourth generation of automotive light sources, LEDs have many features superior to other traditional light sources. This paper analyzes the feasibility and advancement of automotive LED lighting, introduces its typical driving circuit, and focuses on the application status of LED and AFS in automotive headlamps. The problems and countermeasures of LED lighting for vehicles are introduced, and their future development is prospected.
1 Feasibility and advancement of automotive LED lighting
The use of illumination sources in cars began around the beginning of the 20th century. The first to use kerosene lamps and acetylene lamps, the use of electric light sources began in 1910, has experienced incandescent lamps, tungsten halogen lamps and high-intensity discharge gas lamps HID (Intensity Discharge Lamp), since 1985 began to enter the LED vehicle The era of lights. At the same time, the technology of LED lamps applied to the adaptive front lighting system AFS (Adaptive Front Lighting System) has emerged.
At present, LED has been used by many car manufacturers to create a variety of lamp styles. In order to improve their overall competitiveness, famous brand cars such as BMW, Ford, Honda, Toyota, Mercedes-Benz, Audi, etc. have launched new cars with a variety of LED lights to attract customers. LEDs have many advantages that other light sources do not have: (1) long life and good shock resistance. The service life of LEDs can theoretically reach 50,000 hours, and the actual life expectancy can reach 20,000 hours (common halogen bulbs are only about 150 to 500 hours), which generally exceeds the life of the car itself. In addition, there is no fragile movable part in the basic structure of the LED, so the seismic performance is very good. (2) Energy saving and environmental protection. The LED can obtain sufficient brightness under the condition of low voltage and small current, and its power consumption is only 10%-20% of the same brightness incandescent lamp; the LED light source does not contain mercury harmful to human health, and the production process and waste will not Cause environmental pollution. (3) Fast response. Compared with incandescent lamps, the response time of LED lamps has reached tens of nanoseconds. Thus, when LEDs are used as taillights for vehicles, subsequent car drivers can react earlier to reduce traffic accidents. (4) Small size. The compact LED makes the car-style design more free and versatile, making the model more fashionable. Compared with the traditional light source, the installation depth of the LED signal light system can be reduced by 80 mm, which is of great significance for the car shape and internal parts layout. .
At present, the automobile industry is still a pillar industry in the global economy, and is in a critical period of rapid development. It will certainly drive the development of automotive lamps and provide a broad market space for LED applications in automobiles.
2 car LED lighting drive circuit
LEDs are current-controlled semiconductor devices, and Figure 1 shows the volt-ampere characteristics of LEDs. It can be seen from Fig. 1 that the curve is steep, and there is almost no current flowing through the LED before the forward conduction; when the forward voltage exceeds the turn-on voltage, the current rises sharply, and the luminance L is approximately proportional to the forward current IF: L= KIF, where K is the scaling factor, so you can control the brightness of the LED by controlling the IF of the LED. Therefore, in order to ensure the uniformity of its brightness, a constant current source driving circuit is usually employed.
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