LED is a new type of highly efficient and environmentally friendly semiconductor light source, which has advantages that other light sources cannot match. The future is promising in automotive lighting applications. LEDs can be combined into LED arrays in different ways, such as series and parallel, to meet the requirements of automotive lighting intensity. Aiming at the light-emitting characteristics of LEDs, the design and characteristics of LED drivers are mainly discussed, and the current problems and solutions of LEDs are briefly described.
1 Function and requirements of car lights
At present, cars are becoming more and more civilian and have become the main means of transportation. The safety of driving has attracted widespread social attention. According to incomplete statistics, the mileage of a car driving at night or lack of natural light accounts for 25% of the total mileage, and the traffic accidents during this period account for 40% of the total accidents, and more than half of the casualties occur at night . Therefore, exterior lights and signal lights are the key components for the safe driving of vehicles, and must meet the following conditions:
(1) There is no delay in the lighting of car lights, the response time is faster, and the driver is given more reaction time.
(2) The brightness of the lighting is strong, which improves the driver's field of vision at night or in the absence of natural light, and at the same time makes the indication function of the signal lights outside the vehicle stronger.
(3) High earthquake resistance, high reliability, and avoid accidents caused by lighting failure.
(4) Energy saving, which can effectively reduce the emission of exhaust gas and protect the environment.
(5) Based on the increasingly fierce competition in car sales, the design of car lights should be practical and beautiful.
2 LED has become a new star in the selection of automotive lighting materials
2.1 Working principle of LED
LED is a special diode, which is a semiconductor device that forms a PN junction by means such as doping. When the diode conduction conditions are met, current flows through the LED, releasing energy in the form of light and heat. LED is a current-controlled current-type element. Its luminous intensity mainly depends on the magnitude of the current passing through. When it is in forward conduction, its voltage drop is very high, and it has a certain fluctuation range.
Since the LED does not have infrared and ultraviolet radiation, the energy it consumes is almost all thermal energy except converted into light energy, and can only be transmitted in the form of heat conduction. Therefore, when the LED is working, the junction temperature will gradually increase. LEDs are devices with a negative temperature coefficient. The current flowing through the LED will increase as the temperature rises. This forms positive feedback, resulting in a further increase in junction temperature. If not controlled, the LED will be burned. The thermal parameters of LED have a great relationship with the junction temperature of the PN junction. The relationship between the dominant wavelength and the temperature is as follows:
mp (Tl) = m0 (T0) + 3Tg # 0.1nm / ° C
It can be seen from the above formula that every time the LED junction temperature rises by 10 ° C, the dominant wavelength (which can be observed by the human eye) will drift toward the long wave by 1nm (1nm = 10-9m), causing the LED brightness to decrease and light decay. Therefore, the overheating of individual LEDs will cause the uniformity of the LED array's light emission to deteriorate.
Auto spare lamp kits are extra lamp pieces that can be used to replace a piece that broken. There are many different bulbs and fuses in one spare lamp kits. For example, there are one H4 for headlight, one S25 singe filament for signal light, one dual filament S25 for stop light, one G18.5 for truck light or license plate light, one T10 for interior light or side indicators light and two different types of fuses that can replace the burned fuse. The customers will review what specs their own vehicle have and choose which to buy. Having a spare lamp in the car is like buy a insurance, because every light on the car has its specific purpose, which means any broken bulb might put the driver and others in a very dangerous situation. Highly recommend have one kits in the car.
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Heshan Jianhao Lighting Industrial Co., Ltd. , https://www.sunclubtw.com