At present, the car lights are equipped with incandescent lamps, halogen lamps, xenon lamps and the like. In addition to the headlights, other lamps such as small lamps, indicator lights, and interior lighting are mostly incandescent lamps. However, in recent years, LEDs have also become popular indicators, such as brake indicators, turning indicators, and the like. Why do you use LEDs instead of incandescent lamps?
Originally, LEDs have significant advantages over incandescent lamps. First, it has a long life span, usually tens of thousands or even 100,000 hours. Some people think that if the future car lights use LEDs, the entire car life will not need to be replaced. The second is very energy-saving, at least half of the energy saving of incandescent lamps of the same brightness. Third, the light quality is high, basically no radiation, belonging to the "green" light source. Fourth, the structure of the LED is simple, the internal support structure is surrounded by a transparent epoxy resin, and the seismic performance is good. Fifth, there is no need for hot start time, and the light response speed is fast (nanosecond level), which is suitable for objects with fast moving speed. Sixth, the applicable voltage is between 6-12 volts, which can be applied to the car. Seventh, the LEDs occupy a small volume, and the designer can change the lamp mode at will, so that the car shape is diversified. Automotive manufacturers favor LEDs, which are entirely determined by the advantages of LEDs themselves.
LED is an abbreviation for Light Emitting Diode, which was produced as early as the 1960s. It has been widely used in household appliances in the 1980s, such as sound volume indications, switch indications, and the like. In the 1990s, some new domestic car instruments also used LEDs, mainly for charging instructions, and later showed engine speed conditions, such as a combination meter produced by Xiangfan, Hubei, with a row of LEDs next to the odometer. When the driver steps on the gas pedal, the LED row lights will light up from bottom to top. When the throttle is loose, the LED row lights will be extinguished from top to bottom, which is quite eye-catching. In the mid-1990s, China used LEDs to make high-position brake lights and installed them on the car. Because the LEDs were fast, the driver of the car behind the tail could know the driving condition of the vehicle ahead and reduce the collision of the car.
An LED is a solid semiconductor element including a pn junction that can emit light by itself. The chip of the LED is a wafer composed of a p-type semiconductor and an n-type semiconductor, and a transition layer between the p-type semiconductor and the n-type semiconductor is referred to as a pn junction. When semiconductor materials such as gallium arsenide (infrared), arsenic gallium phosphide (red to yellow), and gallium phosphide (green) are used, minority carriers and majority carriers are implanted in the pn junction of these semiconductor materials. When compounded, the excess energy is released as light, which converts the electrical energy directly into light energy. When a forward voltage is applied to the pn junction and current flows from the anode of the LED to the cathode, the semiconductor crystal emits light of different colors from ultraviolet to infrared. The intensity of the light is related to the magnitude of the current. However, since the luminous power of the LED is small, it is generally only an indication and cannot be used as illumination. For lighting purposes, it is a new thing that has only appeared in recent years.
Since the LED light power is small, generally many LEDs are arrayed.
It is a practical indicator light in the form of a small product. However, as a result, the cost will rise rapidly. Because a high-quality LED is about 1.5 yuan, the price of dozens of collections is far more than incandescent. Since the brightness of the LED is proportional to the current, the higher the input current, the higher the brightness of the light. Therefore, increasing the rated current of the LED and increasing the light output power are the focus of the research and development of the factory. Only by increasing the luminous power of a single LED can the array of LEDs be reduced, even with a single LED, to reduce costs. At present, the lighting industry has developed a single white LED with a luminous efficacy of 15 lumens per watt, which is equivalent to the luminous efficacy of incandescent lamps.
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At the 2004 Beijing Auto Show, the French Leo Company demonstrated the high-position brake light technology made of four LEDs, and also used one LED to realize all the tail signal functions, including stop lights, rear small lights, turn lights, fog lights. And reversing lights, etc. This LED technology is suitable for all taillight functions. At the Ford Motor Show, the Focus concept headlights and rear lights for the future Chinese market use LED technology. Some people predict that the two major bottlenecks of LED's luminous power and cost will be solved in the next few years. In this way, not only automotive lighting, but even the entire lighting industry will undergo major changes.
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