Ambient light sensor chips used in automotive headlight systems

In order to ensure the safety and convenience of driving lighting and reduce the labor intensity of the driver. In recent years, many new lighting control systems have emerged, such as automatic lighting systems for daytime driving, beam adjustment systems, delay control, etc. Especially the auto adaptive headlight system, which is a headlight system that can automatically change more than two light patterns to adapt to changes in vehicle driving conditions. It is one of the new technologies in the world of car lighting. The research and development of the car has played a great role in the safety of driving at night.

The working principle of the automatic headlight lighting system: when the headlight switch is turned to the AUTO position, the light sensor installed on the upper part of the instrument panel detects the surrounding light intensity and automatically controls the lighting. Here's how it works. When the door is closed and the ignition switch is turned on, the trigger control transistor VT1 is turned on to supply power to the automatic lighting controller.
(1) When the surrounding environment is bright: when the brightness of the surrounding environment is greater than the shut-off illuminance L2 (about 550 Lx) and the shut-off illuminance L4 (about 200 LX) of the night detection circuit, both the night detection circuit and the night detection circuit output low level, transistors VT2 and VT3 are turned off, and all lights do not work.
(2) At dusk and night: When the ambient brightness is darker than the lighting intensity L1 (about 130 L1) of the night detection circuit, the night detection circuit outputs a high level to turn on VT2. At this time, the taillight circuit is turned on, and the taillight lights up. When the night detection circuit is in a dark state and reaches the illuminance L3 (about 50 L x) of the lighting circuit at night, it outputs a high level. At this time, the delay circuit also outputs a high level to turn on the transistor VT3. The job of the relay is to turn on the headlights.
(3) When the ambient brightness changes after starting: when the headlights are turned on, when the surrounding environment suddenly becomes bright due to street lights and other reasons, the output of the night detection circuit becomes low. But under the effect of the delay circuit, in the time T, VT 3 keeps on, so that the headlight will not go out. When the ambient brightness is brighter than the closed lighting L2 of the night/dusk detection circuit (for example, a white car comes out of the tunnel), the low level is output from the night/dusk detection circuit, so that the delay circuit is canceled, and the taillights and headlights immediately off.
AFS is a system composed of sensor group, transmission path, processor and actuator. Due to the need to make comprehensive judgments on various vehicle driving states, AFS is objectively determined to be a complex system with multiple inputs and multiple outputs.
To achieve different functions, AFS must obtain different vehicle driving information from different sensors. For example, in order to realize the function of rotating lighting in curves, in addition to obtaining the vehicle speed from the vehicle speed sensor, the steering wheel angle from the steering wheel angle sensor, and the vehicle body tilt angle from the vehicle height sensor, it is also necessary to obtain information about the actual steering angle of the vehicle through some special sensors. ; Obtain visible light ranging from the ambient light sensor chip to avoid some obstacles.