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Now when people choose and buy cars, they will find that more and more models are equipped with LED car headlights. So what exactly is LED smart headlight technology? Let's start with the development of car lights, and then talk about the evolution of active car lights from the current matrix headlights to the future dot matrix headlights and even laser headlights. Let's follow CoolMotor to learn about it.
First, let's use the Audi related car light technology advertisement, which is known as the lighting factory, to introduce the history of car lights.
Audi LED lighting
What is LED
LED (above) and OLED (below) in car lighting technology
Let's first take a look at what LED is and how it works. The full name of LED is Light Emitting Diode. From the name, we can see that LED is also a diode, and it also has the characteristic of unidirectional conduction. Unlike ordinary diodes, traditional diodes only generate current when driven by voltage across the semiconductor PN junction, while LED light-emitting diodes generate both current and light. At the same time, the forward voltage drop of LED is also higher than the 0.7V of ordinary diodes, because light-emitting diodes are different from ordinary diodes, which use silicon semiconductors but wide bandgap semiconductors. The specific materials vary with the color of the light. For example, red light uses gallium arsenide, green light uses gallium phosphide, yellow light uses silicon carbide, and blue light uses gallium nitride materials, and the forward voltage ranges from 1.5V to 3.6V.
OLED is an organic LED, which is characterized by multi-layer organic materials as chemical materials. Unlike the point light source characteristics of traditional LEDs, OLED is a surface light source. Therefore, OLED technology is currently mostly used in mobile phone screens, while automotive applications are mostly used in taillights.
Advantages and application examples of LED technology
New Volkswagen Passat LED headlight assembly
LED technology is widely used in automotive lighting due to the following advantages.
Energy saving, power consumption is only 1/10 of that of traditional bulbs
Long life, more than 10 times longer than that of traditional light sources
Small size, designers can change lamps at will to make the shape diverse
Fast response speed, no hot start time, can emit light within microseconds, no hysteresis, ensuring driving safety
At the same time, the long life of LED requires good constant current control and suitable operating temperature. Excessive current and high temperature may damage the LED. This is why many models on the road in the past had the problem of taillight LED beads not lighting up. A reliable LED headlight requires a good headlight control circuit.
New Volkswagen Passat LED headlight controller
Take the new Volkswagen Passat LED headlight as an example. The entire headlight assembly consists of a main light composed of low beam + high beam, additional low beam, static cornering light, daytime running light chain and turn signal light chain. The corresponding smart headlights are equipped with a large number of controllers behind them, including low beam/high beam LED control module, daytime running light/turn signal LED control module and AFS/MDF adaptive front light/shielded continuous high beam control module.
Details of the smart headlight controller
Specifically, the low beam/high beam LED control module is responsible for controlling the 6 LED beads low beam in the upper half of the main light (total power 22.5W) + 4 LED beads high beam in the lower half (total power 60W) and 6 LED beads in the additional low beam (total power 22.5W). The daytime running light/turn signal LED control module is responsible for driving the 4 LED beads daytime running light chain (total power 9.4W) and the 14 LED beads turn signal chain (total power 11.5W). Each light module monitors the temperature of the light group in real time through thermistors, and controls the cooling fan to cool down and adjust the power to ensure the service life of the LED.
Details of the DLA smart headlight irradiation adjustment auxiliary controller
The DLA smart headlight irradiation adjustment auxiliary is realized by the AFS/MDF adaptive front light/shielded continuous high beam control module. It rotates the irradiation angle by adjusting the horizontal and vertical follow-up steering servo motors of the main light bracket to avoid the view of oncoming vehicles. The cylindrical sunshade is used to actively block the light path of the high beam.
Future Trends
The Audi A8 contains active matrix headlights with 25 independent LEDs
When it comes to the future trend of LED car headlights, one mainstream direction is active matrix headlights. For example, the Audi A8 launched in 2014 was the first to use matrix headlights. The camera-based driving assistance system detects the position of the oncoming vehicle and adjusts the brightness of the corresponding LED inside the corresponding matrix headlight. This allows the high beam to avoid the eyes of the oncoming driver while illuminating the rest of the road. The matrix headlights used by the Audi A8 first contain 25 independent LEDs.
Details of Audi A8 Active Matrix Headlights
The Audi A8 active matrix headlight assembly is composed of matrix high beam, low beam and water turn signal from top to bottom. The matrix high beam is specifically composed of 5 high beam reflectors, and each reflector corresponds to an LED circuit board. Each circuit board contains 5 independently controllable OSRAM LED lamp beads. Thus, the high beam illumination range can be flexibly controlled through the intelligent matrix headlight controller. At the same time, the turn signal controller can control the turn signal light chain to light up in sequence, producing a flowing light effect. In case of an emergency, the turn signal controller can flexibly switch back to the traditional turn signal intermittent lighting mode for warning.
Details of the flowing turn signal of Audi A8
Then with the development of car lighting technology, more and more independent LEDs are integrated into active matrix headlights. For example, the MULTIBEAM active matrix headlights used by Mercedes-Benz contain 84 independent LEDs. The PDLS active matrix headlights equipped with the Porsche Panamera even contain 109 independent LEDs. It can be said that the presentation of future dot matrix headlights will make smart headlights close to the flexibility of projectors.
Audi Q7 laser headlights
Another development trend is laser headlights. The high beam based on laser technology increases the irradiation distance of the previous LED headlights from 150m to 250m. Walking at night will be like daytime, which is more reassuring. Taking the Audi Q7 as an example, its high-tech headlight assembly consists of LED matrix main lights, laser modules, LED low beams and flowing daytime running lights/turn signals, cooling fans and control modules. Laser LEDs are different from traditional LEDs that emit spontaneous radiation. Instead, they are based on the principle of stimulated radiation. Therefore, the spectrum is narrow, the color is pure, and the optical path is straight. For example, the laser scanning sensor of the driving assistance system has accurate distance measurement. Laser headlights are a bit like laser pens. They use 4 blue laser LEDs with a total power of 30W in the 450nm band to emit light beams to the fluorescent reflector to convert them into white light and adjust the optical path to irradiate to a very far distance. In order to consider the safety of human eyes, the laser headlights will only be automatically turned on when the speed is high enough and the driving assistance system confirms that there are no oncoming vehicles.
In summary, today we introduced the principles of LED technology and the application examples of smart car headlights. We also introduced the development trends of future matrix headlights and laser headlights. I hope it will help you understand LED headlight technology.
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