LED lighting system design and the breakthrough in the field of automobile

For a long time, the car's brake lights, turn signals, reversing lamp and the rear fog lamps are 21 w to 27 w, brightness is from 280 to 570 lumens of tungsten filament lamp as light source. Car tail lights, parking lights, side lights and turn signals flash adopt 4 w and 10 w tungsten lamps, brightness is 40 to 130 lumens, car headlights, the use of the high brightness xenon fluorescent tube ( 藏) 。 But in automotive lighting, LED as light source are used more and more. The tail of the central high brake lights was among the first to adopt LED car light. In addition, the lights on the market, car lighting and other indicators, such as brake lights, turn signals, and the lights have to switch to LED bulbs. In recent years, car lights, such as daytime running lights ( DRL) Car, as well as the low beam lights to switching the LED bulbs. Car headlights are also expected quickly to switch to high brightness leds. In addition, inside the body, some of the car display backlight are using LED as light source, such as the dashboard and TFT display. The advantages of car LED lighting system of white LED color temperature is about 6000 k, the vision is almost equivalent to natural light. Due to the human eye's ability to distinguish color under the condition of natural background is the best. In the evening, the human eye only under the condition of natural color, the scene has a good ability to distinguish between or the road edges. The average life span for the LED lamp is higher than tungsten filament lamp and fluorescent lamp brightness length, and is more stable and reliable. If can reduce the rate of fail, without frequent replacement bulbs, dispense with a lot of trouble. And using LED can save more energy. Leds appearance is smaller, more easily into the lamp holder, at the same time of take up less space, are more likely to cooperate with fashion lighting design. More importantly, LED brake lights start faster. LED brake lights light up time is only about 50 ms, faster than the start time of tungsten filament bulbs around 250 ms, which reduces the risk of being following vehicle collision. In addition, the LED is a solid-state light source, can withstand greater shock. Driving leds technical requirements because of the brightness of the leds is proportional to the flow of electric current, so I need a constant current source to drive the leds. In any case, to maintain a constant current through the LED, to ensure the consistency of the LED brightness. You also need to in no case can ripple current control at an acceptable level. So the LED driver design belongs to the power conversion circuit design, characterized by a constant current output rather than the constant voltage output. In the design of the LED driver, must increase blocking circuit, in order to prevent the reverse operation of power supply protection. We would face another challenge is to in the case of a power car cold start or load to ensure that the LED can work properly. In the case of normal operation, the car battery power supply voltage between 9 v and 16 v ( The 12 v system bus, for example) , and the big truck battery voltage is between 18 v and 32 v ( 24 v system bus, for example) 。 In case of power load or cold start, battery input voltage range will differ greatly with normal range. During the period of generator running, if the battery power supply is suddenly cut off the electricity opportunities continue to power generation, the use of generators electrical components such as the capacitance voltage will appear the phenomenon of increased suddenly, if do not take protective measures, will be damaged by electrical appliances. If the LED driver is not a constant current driver, the LED current can change, change of the brightness of the LED, which is why the current car lights flicker phenomenon exists. The following is a power load test of a definition, used to imitate the load sudden break some of the situation. Different manufacturers use different standards, so the definition of power load test is also each are not identical,