阅读说明：本技术 电子后视镜及其自动调光电路和方法 (Electronic rearview mirror and automatic dimming circuit and method thereof ) 是由 罗小平 成亚平 李云彬 于 2021-09-09 设计创作，主要内容包括：本发明实施例提供一种电子后视镜及其自动调光电路和方法,所述电路与LED显示屏相连,包括：第一亮度检测模块、第二亮度检测模块,第一亮度检测模块和第二亮度检测模块的第一光敏传感器和第二光敏传感器基于电子后视镜周围同一环境亮度同时产生相同值的检测电流；主控模块,分别获得第一采样点和第二采样点处的第一检测电压和第二检测电压,比较第一检测电压与预设电压阈值,在第一检测电压小于或等于预设电压阈值时根据第一检测电压和第一数据表确定并依次输出相应占空比的PWM信号,否则根据第二检测电压和第二数据表确定并依次输出相应占空比的PWM信号；驱动模块,输出驱动电流给LED显示屏。本实施例能根据环境亮度准确的调整LED显示屏的亮度。(The embodiment of the invention provides an electronic rearview mirror and an automatic dimming circuit and method thereof, wherein the circuit is connected with an LED display screen and comprises the following steps: the electronic rearview mirror comprises a first brightness detection module, a second brightness detection module, a first photosensitive sensor and a second photosensitive sensor of the first brightness detection module and the second brightness detection module simultaneously generate detection currents with the same value based on the same ambient brightness around the electronic rearview mirror; the main control module is used for respectively obtaining a first detection voltage and a second detection voltage at a first sampling point and a second sampling point, comparing the first detection voltage with a preset voltage threshold, determining and sequentially outputting PWM signals with corresponding duty ratios according to the first detection voltage and a first data table when the first detection voltage is less than or equal to the preset voltage threshold, and otherwise determining and sequentially outputting the PWM signals with corresponding duty ratios according to the second detection voltage and a second data table; and the driving module outputs driving current to the LED display screen. The embodiment can accurately adjust the brightness of the LED display screen according to the ambient brightness.)

1. An automatic dimming circuit of an electronic rearview mirror is connected with an LED display screen of the electronic rearview mirror, and is characterized in that the circuit comprises:

the first brightness detection module comprises a first power supply, a first photosensitive sensor and a first sampling resistor R1 which are sequentially connected in series, wherein one end, far away from the first photosensitive sensor, of the first sampling resistor R1 is grounded;

the second brightness detection module comprises a second power supply source, a second photosensitive sensor and a second sampling resistor R1 which are sequentially connected in series, one end, far away from the second photosensitive sensor, of the second sampling resistor R2 is grounded, the resistance value of the first sampling resistor R1 is larger than that of the second sampling resistor R2, the circuit parameters of the first power supply source and the second power supply source are the same, and the first photosensitive sensor and the second photosensitive sensor simultaneously generate detection currents with the same value based on the same ambient brightness around the electronic rearview mirror;

the two input ends of the main control module are respectively connected to a first sampling point on a line between the first photosensitive sensor and the first sampling resistor R1 and a second sampling point on a line between the second photosensitive sensor and the second sampling resistor R2 to respectively obtain a first detection voltage and a second detection voltage at the first sampling point and the second sampling point, the main control module is internally provided with a first data table reflecting the corresponding relation between the first detection voltage and the duty ratio of the PWM signal and a second data table reflecting the corresponding relation between the second detection voltage and the duty ratio of the PWM signal, the main control module is used for comparing the first detection voltage with a preset voltage threshold value, and determining and sequentially outputting the PWM signal with the corresponding duty ratio according to the first detection voltage and the first data table when the first detection voltage is less than or equal to the preset voltage threshold value, when the first detection voltage is larger than a preset voltage threshold value, determining and sequentially outputting PWM signals with corresponding duty ratios according to the second detection voltage and a second data table; and

and the driving module is connected with the output end of the main control module and the LED display screen, is internally provided with a third data table reflecting the corresponding relation between the duty ratio of the PWM signal and the driving current, and is used for determining and sequentially outputting the driving current with corresponding preset magnitude to the LED display screen according to the duty ratio of the PWM signal output by the main control module and the third data table.

2. The automatic dimming circuit of an electronic rearview mirror as claimed in claim 1, wherein the main control module comprises:

the sampling unit is used for obtaining the first detection voltage and the second detection voltage by respectively connecting the two input ends with the first sampling point and the second sampling point;

the storage unit is used for storing the first data table, the second data table and a preset voltage threshold;

the comparison unit is connected with the sampling unit and the storage unit and is used for comparing the first detection voltage with the preset voltage threshold value, outputting a low-brightness signal when the first detection voltage is smaller than or equal to the preset voltage threshold value and outputting a high-brightness signal when the first detection voltage is larger than the preset voltage threshold value; and

and the PWM output unit is connected with the sampling unit, the comparison unit and the storage unit and is externally connected with the driving module, and is used for determining and sequentially generating and outputting a first PWM signal with a corresponding duty ratio according to the first detection voltage and the first data table when receiving the low-brightness signal, and determining and sequentially generating and outputting a second PWM signal with a corresponding duty ratio according to the second detection voltage and the second data table when receiving the high-brightness signal.

3. The automatic dimming circuit of an electronic rearview mirror as claimed in claim 1, wherein:

the first brightness detection module further comprises a first capacitor C1 connected in parallel with the first sampling resistor R1;

the second brightness detection module further includes a second capacitor C2 connected in parallel with the second sampling resistor R2 and having the same capacitance value as the first capacitor C1.

4. An electronic rearview mirror comprising an LED display screen and an automatic dimming circuit connected with the LED display screen, wherein the automatic dimming circuit is the automatic dimming circuit as claimed in any one of claims 1 to 4.

5. A method for automatically dimming an automatic dimming circuit based on an electronic rearview mirror according to any one of claims 1 to 3, wherein the method comprises the steps of:

a first power supply source of a first brightness detection module supplies power to a first photosensitive sensor and a first sampling resistor R1, a second power supply source of a second brightness detection module supplies power to a second photosensitive sensor and a second sampling resistor R2, the resistance value of the first sampling resistor R1 is larger than that of the second sampling resistor R2, and the circuit parameters of the first power supply source and the second power supply source are the same;

simultaneously generating detection currents with the same value based on the same ambient brightness around the electronic rearview mirror through the first photosensitive sensor and the second photosensitive sensor respectively;

obtaining a first sampling point on a line between the first photosensitive sensor and a first sampling resistor R1 and a first detection voltage and a second detection voltage at a second sampling point on a line between the second photosensitive sensor and a second sampling resistor R2 through a main control module, comparing the first detection voltage with a preset voltage threshold, determining and sequentially outputting PWM signals with corresponding duty ratios according to the first detection voltage and a first data table when the first detection voltage is less than or equal to the preset voltage threshold, and determining and sequentially outputting the PWM signals with corresponding duty ratios according to the second detection voltage and a second data table when the first detection voltage is greater than the preset voltage threshold; and

and determining and sequentially outputting the driving current with the corresponding preset size to the LED display screen through the driving module according to the duty ratio of the PWM signal and a third data table reflecting the corresponding relation between the duty ratio of the PWM signal and the driving current.

6. The method for automatically dimming an electronic rearview mirror according to claim 5, wherein the obtaining, by the main control module, a first sampling point on a line between the first photosensor and the first sampling resistor R1 and a first detection voltage and a second detection voltage at a second sampling point on a line between the second photosensor and the second sampling resistor R2, comparing the first detection voltage with a preset voltage threshold, determining and sequentially outputting PWM signals of corresponding duty ratios according to the first detection voltage and a first data table when the first detection voltage is less than or equal to the preset voltage threshold, and determining and sequentially outputting PWM signals of corresponding duty ratios according to the second detection voltage and a second data table when the first detection voltage is greater than the preset voltage threshold specifically comprises:

obtaining the first detection voltage and the second detection voltage through a sampling unit;

comparing the first detection voltage with a preset voltage threshold value prestored in a storage unit through a comparison unit, and outputting a low-brightness signal when the first detection voltage is smaller than or equal to the preset voltage threshold value and outputting a high-brightness signal when the first detection voltage is larger than the preset voltage threshold value; and

and determining and sequentially generating and outputting a first PWM signal with a corresponding duty ratio according to the first detection voltage and a first data table prestored in the storage unit through a PWM output unit when receiving the low-brightness signal, and determining and sequentially generating and outputting a second PWM signal with a corresponding duty ratio according to the second detection voltage and a second data table prestored in the storage unit when receiving the high-brightness signal.

Technical Field

The embodiment of the invention relates to the technical field of electronic rearview mirrors, in particular to an electronic rearview mirror and an automatic dimming circuit and method thereof.

Background

At present, most of the existing electronic rearview mirrors are provided with an automatic dimming circuit so as to automatically adjust the backlight brightness of an LED display screen according to the ambient brightness around the electronic rearview mirrors, so that a user can have the best visual sense when observing the display screen of the electronic rearview mirror.

The existing automatic dimming circuit of the electronic rearview mirror mainly comprises a brightness detection module, an MCU chip and a driving module, wherein the brightness detection module is composed of a photosensitive sensor and a voltage detection circuit based on ohm's law, the output current of the photosensitive sensor is gradually increased along with the increase of the ambient brightness by utilizing the characteristic that the output current of the photosensitive sensor is gradually increased, the voltage detection circuit is connected with the photosensitive sensor to convert the output current of the photosensitive sensor into detection voltage, then the MCU chip detects the detection voltage through a voltage sampling port (ADC port) of the MCU chip and outputs PWM (pulse-width modulation) waveforms with corresponding duty ratios according to the detection voltage, and finally the driving module outputs corresponding driving current to an LED display screen according to the PWM waveforms to realize backlight adjustment of the LED display screen.

However, in a vehicle-mounted environment, the variation range of the ambient brightness of the electronic rearview mirror is large (for example, 1 lux-1000 lux), and when a brightness detection module composed of a photosensitive sensor and a voltage detection circuit is used for detecting and outputting a detection voltage, the variation range of the detection voltage is also relatively large, however, voltage sampling ports of the MCU chip all have corresponding voltage sampling peak values (for example, the theoretical value is 5V), and when the detection voltage exceeds the voltage sampling peak values, the MCU chip cannot effectively detect; due to the limitation of the voltage sampling peak value of the MCU chip, the existing dimming circuit has a relatively narrow detection range for the ambient brightness, so that the dimming circuit cannot effectively adjust the LED display screen to the proper backlight brightness according to the ambient brightness.

Disclosure of Invention

The technical problem to be solved by the embodiments of the present invention is to provide an automatic dimming circuit for an electronic rearview mirror, which can effectively adjust an LED display screen to an appropriate backlight brightness according to an ambient brightness.

A further technical problem to be solved in the embodiments of the present invention is to provide an electronic rearview mirror, which can effectively adjust an LED display screen to an appropriate backlight brightness according to an ambient brightness.

A further technical problem to be solved in the embodiments of the present invention is to provide an automatic dimming method for an electronic rearview mirror, which can effectively adjust an LED display screen to an appropriate backlight brightness according to an ambient brightness.

In order to solve the above technical problem, an embodiment of the present invention first provides the following technical solutions: an automatic dimming circuit of an electronic rearview mirror is connected with an LED display screen of the electronic rearview mirror, and comprises:

the first brightness detection module comprises a first power supply, a first photosensitive sensor and a first sampling resistor R1 which are sequentially connected in series, wherein one end, far away from the first photosensitive sensor, of the first sampling resistor R1 is grounded;

the second brightness detection module comprises a second power supply source, a second photosensitive sensor and a second sampling resistor R1 which are sequentially connected in series, one end, far away from the second photosensitive sensor, of the second sampling resistor R2 is grounded, the resistance value of the first sampling resistor R1 is larger than that of the second sampling resistor R2, the circuit parameters of the first power supply source and the second power supply source are the same, and the first photosensitive sensor and the second photosensitive sensor simultaneously generate detection currents with the same value based on the same ambient brightness around the electronic rearview mirror;

the two input ends of the main control module are respectively connected to a first sampling point on a line between the first photosensitive sensor and the first sampling resistor R1 and a second sampling point on a line between the second photosensitive sensor and the second sampling resistor R2 to respectively obtain a first detection voltage and a second detection voltage at the first sampling point and the second sampling point, the main control module is internally provided with a first data table reflecting the corresponding relation between the first detection voltage and the duty ratio of the PWM signal and a second data table reflecting the corresponding relation between the second detection voltage and the duty ratio of the PWM signal, the main control module is used for comparing the first detection voltage with a preset voltage threshold value, and determining and sequentially outputting the PWM signal with the corresponding duty ratio according to the first detection voltage and the first data table when the first detection voltage is less than or equal to the preset voltage threshold value, when the first detection voltage is larger than a preset voltage threshold value, determining and sequentially outputting PWM signals with corresponding duty ratios according to the second detection voltage and a second data table; and

and the driving module is connected with the output end of the main control module and the LED display screen, is internally provided with a third data table reflecting the corresponding relation between the duty ratio of the PWM signal and the driving current, and is used for determining and sequentially outputting the driving current with corresponding preset magnitude to the LED display screen according to the duty ratio of the PWM signal output by the main control module and the third data table.

Further, the main control module includes:

the sampling unit is used for obtaining the first detection voltage and the second detection voltage by respectively connecting the two input ends with the first sampling point and the second sampling point;

the storage unit is used for storing the first data table, the second data table and a preset voltage threshold;

the comparison unit is connected with the sampling unit and the storage unit and is used for comparing the first detection voltage with the preset voltage threshold value, outputting a low-brightness signal when the first detection voltage is smaller than or equal to the preset voltage threshold value and outputting a high-brightness signal when the first detection voltage is larger than the preset voltage threshold value; and

and the PWM output unit is connected with the sampling unit, the comparison unit and the storage unit and is externally connected with the driving module, and is used for determining and sequentially generating and outputting a first PWM signal with a corresponding duty ratio according to the first detection voltage and the first data table when receiving the low-brightness signal, and determining and sequentially generating and outputting a second PWM signal with a corresponding duty ratio according to the second detection voltage and the second data table when receiving the high-brightness signal.

Further, the first brightness detection module further includes a first capacitor C1 connected in parallel with the first sampling resistor R1;

the second brightness detection module further includes a second capacitor C2 connected in parallel with the second sampling resistor R2 and having the same capacitance value as the first capacitor C1.

On the other hand, in order to solve the further technical problem, the embodiment of the present invention further provides the following technical solutions: an electronic rearview mirror comprises an LED display screen and an automatic dimming circuit connected with the LED display screen, wherein the automatic dimming circuit is any one of the automatic dimming circuits.

On the other hand, in order to solve the further technical problem, the embodiment of the present invention further provides the following technical solutions: an automatic dimming method of an automatic dimming circuit of an electronic rearview mirror based on any one of the above methods comprises the following steps: a first power supply source of a first brightness detection module supplies power to a first photosensitive sensor and a first sampling resistor R1, a second power supply source of a second brightness detection module supplies power to a second photosensitive sensor and a second sampling resistor R2, the resistance value of the first sampling resistor R1 is larger than that of the second sampling resistor R2, and the circuit parameters of the first power supply source and the second power supply source are the same;

simultaneously generating detection currents with the same value based on the same ambient brightness around the electronic rearview mirror through the first photosensitive sensor and the second photosensitive sensor respectively;

obtaining a first sampling point on a line between the first photosensitive sensor and a first sampling resistor R1 and a first detection voltage and a second detection voltage at a second sampling point on a line between the second photosensitive sensor and a second sampling resistor R2 through a main control module, comparing the first detection voltage with a preset voltage threshold, determining and sequentially outputting PWM signals with corresponding duty ratios according to the first detection voltage and a first data table when the first detection voltage is less than or equal to the preset voltage threshold, and determining and sequentially outputting the PWM signals with corresponding duty ratios according to the second detection voltage and a second data table when the first detection voltage is greater than the preset voltage threshold; and

and determining and sequentially outputting the driving current with the corresponding preset size to the LED display screen through the driving module according to the duty ratio of the PWM signal and a third data table reflecting the corresponding relation between the duty ratio of the PWM signal and the driving current.

Further, the obtaining, by the main control module, a first sampling point on a line between the first photosensitive sensor and the first sampling resistor R1 and a first detection voltage and a second detection voltage at a second sampling point on a line between the second photosensitive sensor and the second sampling resistor R2, comparing the first detection voltage with a preset voltage threshold, determining and sequentially outputting PWM signals of corresponding duty ratios according to the first detection voltage and the first data table when the first detection voltage is less than or equal to the preset voltage threshold, and determining and sequentially outputting the PWM signals of corresponding duty ratios according to the second detection voltage and the second data table when the first detection voltage is greater than the preset voltage threshold specifically includes:

obtaining the first detection voltage and the second detection voltage through a sampling unit;

comparing the first detection voltage with a preset voltage threshold value prestored in a storage unit through a comparison unit, and outputting a low-brightness signal when the first detection voltage is smaller than or equal to the preset voltage threshold value and outputting a high-brightness signal when the first detection voltage is larger than the preset voltage threshold value; and

and determining and sequentially generating and outputting a first PWM signal with a corresponding duty ratio according to the first detection voltage and a first data table prestored in the storage unit through a PWM output unit when receiving the low-brightness signal, and determining and sequentially generating and outputting a second PWM signal with a corresponding duty ratio according to the second detection voltage and a second data table prestored in the storage unit when receiving the high-brightness signal.

After the technical scheme is adopted, the embodiment of the invention at least has the following beneficial effects: in the embodiment of the invention, a first photosensitive sensor and a first sampling resistor R1 are powered by a first power supply of a first brightness detection module, a second photosensitive sensor and a second sampling resistor R2 are powered by a second power supply of a second brightness detection module, and detection currents with the same value are simultaneously generated by the first photosensitive sensor and the second photosensitive sensor based on the same ambient brightness around the electronic rearview mirror respectively, according to ohm's law, because the resistance value of the first sampling resistor R1 is greater than that of the second sampling resistor R2 and the circuit parameters of the first power supply and the second power supply are the same, the first detection voltage is greater than the second detection voltage, after the main control module further obtains the first detection voltage and the second detection voltage, the first detection voltage is compared with a preset voltage threshold, on the one hand, when the ambient brightness is relatively low and the first detection voltage is less than or equal to the preset voltage threshold of the main control module, at the moment, PWM signals with corresponding duty ratios are determined and sequentially output according to the first detection voltage and the first data table, and output of PWM dimming signals is achieved; on the other hand, when the ambient brightness is relatively high and the first detection voltage is greater than the preset voltage threshold of the main control module, at this time, because the first detection voltage is greater than the second detection voltage under the condition of the same ambient brightness, through reasonable design, the second detection voltage does not reach the preset voltage threshold of the main control module at this time, therefore, the PWM signals with corresponding duty ratios can be determined and sequentially output according to the second detection voltage and the second data table, and the output of the PWM dimming signals can also be realized; finally, the driving module outputs driving current according to the duty ratio of the PWM signal to realize dimming control of the LED display screen, the applicable ambient brightness change range is wide, and the LED display screen can be effectively adjusted to proper backlight brightness according to the ambient brightness.

Drawings

Fig. 1 is a schematic block diagram of an electronic rearview mirror according to an alternative embodiment of the present invention.

Fig. 2 is a schematic block diagram of a specific structure of a main control module of an alternative embodiment of the automatic dimming circuit of the electronic rearview mirror of the present invention.

Fig. 3 is a flowchart illustrating steps of an alternative embodiment of the automatic dimming method for an electronic rearview mirror according to the present invention.

Fig. 4 is a detailed flowchart of step S3 according to an alternative embodiment of the automatic dimming method of the electronic rearview mirror of the present invention.

Detailed Description

The present application will now be described in further detail with reference to the accompanying drawings and specific examples. It should be understood that the following illustrative embodiments and description are only intended to explain the present invention, and are not intended to limit the present invention, and features of the embodiments and examples in the present application may be combined with each other without conflict.

As shown in fig. 1, an alternative embodiment of the present invention provides an automatic dimming circuit 1 for an electronic rearview mirror, connected to an LED display screen 3 of the electronic rearview mirror, including:

the first brightness detection module 10 comprises a first power supply 101, a first photosensitive sensor 103 and a first sampling resistor R1 which are sequentially connected in series, wherein one end of the first sampling resistor R1, which is far away from the first photosensitive sensor 103, is grounded;

the second brightness detection module 12 includes a second power supply 121, a second photosensor 123 and a second sampling resistor R1 connected in series in sequence, one end of the second sampling resistor R2, which is far away from the second photosensor 123, is grounded, a resistance value of the first sampling resistor R1 is greater than a resistance value of the second sampling resistor R2, circuit parameters of the first power supply 101 and the second power supply 121 are the same, and the first photosensor 103 and the second photosensor 123 generate detection currents of the same value simultaneously based on the same ambient brightness around the electronic rearview mirror;

a main control module 14, two input terminals of the main control module 14 are respectively connected to a first sampling point a on a line between the first photosensor 103 and the first sampling resistor R1 and a second sampling point B on a line between the second photosensor 123 and the second sampling resistor R2 to obtain a first detection voltage U1 and a second detection voltage U2 at the first sampling point a and the second sampling point B, respectively, the main control module 14 is provided with a first data table reflecting a corresponding relationship between the first detection voltage U1 and a PWM signal duty ratio and a second data table reflecting a corresponding relationship between the second detection voltage U2 and a PWM signal duty ratio, the main control module 14 is configured to compare the first detection voltage U1 with a preset voltage threshold, and determine and sequentially output PWM signals of corresponding duty ratios according to the first detection voltage U1 and the first data table when the first detection voltage U1 is less than or equal to the preset voltage threshold, when the first detection voltage U1 is larger than a preset voltage threshold, determining and sequentially outputting PWM signals with corresponding duty ratios according to the second detection voltage U2 and a second data table; and

and the driving module 16 is connected with the output end of the main control module 14 and the LED display screen 3, is internally provided with a third data table reflecting the corresponding relation between the duty ratio of the PWM signal and the driving current, and is used for determining and sequentially outputting the driving current with the corresponding preset size to the LED display screen 3 according to the duty ratio of the PWM signal output by the main control module 14 and the third data table.

In the embodiment of the present invention, the first power supply 101 of the first brightness detecting module 10 supplies power to the first photosensor 103 and the first sampling resistor R1, the second power supply 121 of the second brightness detecting module 12 supplies power to the second photosensor 123 and the second sampling resistor R2, and the first photosensor 103 and the second photosensor 123 simultaneously generate the same detection current based on the same ambient brightness around the electronic rearview mirror, respectively, according to the ohm's law, since the resistance value of the first sampling resistor R1 is greater than the resistance value of the second sampling resistor R2 and the circuit parameters of the first power supply 101 and the second power supply 121 are the same, the first detection voltage U1 is greater than the second detection voltage U2, and after the main control module 14 further obtains the first detection voltage and the second detection voltage, the first detection voltage U1 is compared with the preset voltage threshold, on one hand, when the ambient brightness is relatively low and the first detection voltage U1 is less than or equal to the preset voltage threshold of the main control module 14, determining and sequentially outputting PWM signals with corresponding duty ratios according to the first detection voltage U1 and the first data table, so as to output the PWM dimming signals; on the other hand, when the ambient brightness is relatively high and the first detection voltage U1 is greater than the preset voltage threshold of the main control module 14, at this time, because the first detection voltage U1 is greater than the second detection voltage U2 under the condition of the same ambient brightness, through reasonable design, the second detection voltage U2 does not reach the preset voltage threshold of the main control module 14, therefore, the PWM signals with corresponding duty ratios can be determined and sequentially output according to the second detection voltage U2 and the second data table, and the output of the PWM dimming signal can also be realized; finally, the driving module 16 outputs the driving current according to the duty ratio of the PWM signal to realize dimming control of the LED display screen 3, and the LED display screen 3 can be effectively adjusted to a proper backlight brightness according to the ambient brightness with a wide range of variation of the ambient brightness.

In practical implementation, it is understood that the circuit parameters of the first power supply 101 and the second power supply 121 are the same, which means that the output voltages of the two power supplies are the same; the characteristics of the output current of the first photosensitive sensor 103 and the output current of the second photosensitive sensor 123 are the same with the change of the ambient brightness.

As shown in the following table, the table is a corresponding relationship table of the ambient brightness, the first detection voltage U1, the second detection voltage U2 and the positive duty ratio of the PWM signal in the first data table according to an alternative embodiment of the present invention.

As shown in the following table, the table is a corresponding relationship table of the ambient brightness, the first detection voltage U1, the second detection voltage U2 and the positive duty ratio of the PWM signal in the second data table according to an alternative embodiment of the present invention.

When a circuit is designed specifically, the resistance value of the first sampling resistor R1 is 100 kilo-ohms; the resistance value of the second resistor is 1 kilo-ohm, the main control module 14 is composed of an MCU chip and a peripheral circuit thereof, the driving module 16 adopts a backlight driving power supply of the LED display screen 3, the MCU chip is respectively connected with the first brightness detection module 10 and the second brightness detection module 12 through two voltage sampling ports (ADC1 and ADC2), and the MCU chip also outputs PWM signals through an IO port thereof and is connected with a PWM input port of the backlight driving power supply; in addition, because the peak value of the theoretical voltage of the voltage sampling port of the MCU chip is 5V, in the embodiment of the invention, the preset voltage threshold value is set to 4.5V, so that the change of the ambient brightness can be effectively reflected, and the phenomenon that the voltage detection cannot be realized due to the deviation generated by the peak value of the theoretical voltage is avoided.

In an optional embodiment of the present invention, as shown in fig. 2, the main control module 14 includes:

the sampling unit 141 is connected with the first sampling point a and the second sampling point B through two input ends to obtain the first detection voltage U1 and the second detection voltage U2;

a storage unit 143, configured to store the first data table, the second data table, and a preset voltage threshold;

a comparing unit 145, connected to the sampling unit 141 and the storage unit 143, for comparing the first detection voltage U1 with the preset voltage threshold, outputting a low luminance signal when the first detection voltage U1 is less than or equal to the preset voltage threshold, and outputting a high luminance signal when the first detection voltage U1 is greater than the preset voltage threshold;

and a PWM output unit 147, connected to the sampling unit 141, the comparing unit 145 and the storing unit 143 and externally connected to the driving module 16, for determining and sequentially generating and outputting a first PWM signal with a corresponding duty ratio according to the first detection voltage U1 and the first data table when receiving the low luminance signal, and determining and sequentially generating and outputting a second PWM signal with a corresponding duty ratio according to the second detection voltage U2 and the second data table when receiving the high luminance signal.

In this embodiment, the sampling unit 141 obtains the first detection voltage U1 and the second detection voltage U2, the comparison unit 145 determines a magnitude relationship between the first detection voltage U1 and a preset voltage threshold stored in the storage unit 143, and then outputs a low brightness signal and a high brightness signal according to a comparison result, and determines that the ambient brightness is in a preset high brightness interval or a preset low brightness interval, and finally the PWM output unit 147 outputs different PWM signals according to the low brightness signal and the high brightness signal, so as to output the PWM dimming signal.

In yet another alternative embodiment of the present invention, as shown in fig. 3, the first luminance detecting module 10 further includes a first capacitor C1 connected in parallel with the first sampling resistor R1; the second brightness detecting module 12 further includes a second capacitor C2 connected in parallel with the second sampling resistor R2 and having the same capacitance value as the first capacitor C1.

In this embodiment, the first capacitor C1 and the second capacitor C2 are further disposed to respectively correspond to the first sampling resistor R1 and the second sampling resistor R2, so that noise in the voltage output to the control module 14 can be effectively filtered, and the stability of the circuit can be effectively enhanced.

On the other hand, as shown in fig. 1, the embodiment of the present invention further provides the following technical solutions: an electronic rearview mirror comprises an LED display screen 3 and an automatic dimming circuit 1 connected with the LED display screen 3, wherein the automatic dimming circuit 1 is the automatic dimming circuit described in any one of the above items. The electronic rearview mirror provided by the embodiment of the invention adopts the automatic dimming circuit 1, and can effectively and accurately adjust the backlight brightness of the LED display screen 3 according to the ambient brightness.

On the other hand, as shown in fig. 3, the embodiment of the present invention further provides the following technical solutions: an automatic dimming method of an automatic dimming circuit of an electronic rearview mirror based on any one of the above methods comprises the following steps:

s1: the first photosensitive sensor 103 and the first sampling resistor R1 are powered by the first power supply 101 of the first brightness detection module 10, the second photosensitive sensor 123 and the second sampling resistor R2 are powered by the second power supply 121 of the second brightness detection module 12, the resistance value of the first sampling resistor R1 is greater than that of the second sampling resistor R2, and the circuit parameters of the first power supply 101 and the second power supply 121 are the same;

s2: simultaneously generating the same value of detection current based on the same ambient brightness around the electronic rearview mirror through the first photosensitive sensor 103 and the second photosensitive sensor 123 respectively;

s3: obtaining a first sampling point A on a line between the first photosensitive sensor 103 and a first sampling resistor R1 and a first detection voltage U1 and a second detection voltage U2 on a second sampling point B on a line between the second photosensitive sensor 123 and a second sampling resistor R2 through a main control module 14, comparing the first detection voltage U1 with a preset voltage threshold, determining and sequentially outputting PWM signals with corresponding duty ratios according to the first detection voltage U1 and a first data table when the first detection voltage U1 is smaller than or equal to the preset voltage threshold, and determining and sequentially outputting the PWM signals with corresponding duty ratios according to the second detection voltage U2 and a second data table when the first detection voltage U1 is larger than the preset voltage threshold; and

s4: and determining and sequentially outputting the driving current with the corresponding preset magnitude to the LED display screen 3 through the driving module 16 according to the duty ratio of the PWM signal and a third data table reflecting the corresponding relation between the duty ratio of the PWM signal and the driving current.

In the embodiment of the present invention, by the above method, the first power supply 101 of the first brightness detecting module 10 is used to supply power to the first photosensitive sensor 103 and the first sampling resistor R1, the second power supply 121 of the second brightness detecting module 12 is used to supply power to the second photosensitive sensor 123 and the second sampling resistor R2, and the first photosensitive sensor 103 and the second photosensitive sensor 123 respectively generate the detection current with the same value based on the same ambient brightness around the electronic rearview mirror, according to the ohm law, since the resistance value of the first sampling resistor R1 is greater than the resistance value of the second sampling resistor R2 and the circuit parameters of the first power supply 101 and the second power supply 121 are the same, the first detection voltage U1 is greater than the second detection voltage U2, and after the main control module 14 obtains the first detection voltage and the second detection voltage, the first detection voltage U1 is compared with the preset voltage threshold, on one hand, when the ambient brightness is relatively low and the first detection voltage U1 is less than or equal to the preset voltage threshold of the main control module 14, determining and sequentially outputting PWM signals with corresponding duty ratios according to the first detection voltage U1 and the first data table, so as to output the PWM dimming signals; on the other hand, when the ambient brightness is relatively high and the first detection voltage U1 is greater than the preset voltage threshold of the main control module 14, at this time, because the first detection voltage U1 is greater than the second detection voltage U2 under the condition of the same ambient brightness, through reasonable design, the second detection voltage U2 does not reach the preset voltage threshold of the main control module, therefore, the PWM signals with corresponding duty ratios can be determined and sequentially output according to the second detection voltage U2 and the second data table, and the output of the PWM dimming signal can also be realized; finally, the driving module 16 outputs the driving current according to the duty ratio of the PWM signal to realize dimming control of the LED display screen 3, and the LED display screen 3 can be effectively adjusted to a proper backlight brightness according to the ambient brightness with a wide range of variation of the ambient brightness.

In another alternative embodiment of the present invention, as shown in fig. 4, the step S3 specifically includes:

s31: the first detection voltage U1 and the second detection voltage U2 are obtained through a sampling unit 141;

s32: comparing the first detection voltage U1 with a preset voltage threshold pre-stored in the storage unit 143 by the comparing unit 145, outputting a low luminance signal when the first detection voltage U1 is less than or equal to the preset voltage threshold and outputting a high luminance signal when the first detection voltage U1 is greater than the preset voltage threshold; and

s33: the PWM output unit 147 determines and sequentially generates and outputs a first PWM signal of a corresponding duty ratio according to the first detection voltage U1 and a first data table pre-stored in the storage unit 143 when receiving the low luminance signal, and determines and sequentially generates and outputs a second PWM signal of a corresponding duty ratio according to the second detection voltage U2 and a second data table pre-stored in the storage unit 143 when receiving the high luminance signal.

According to the embodiment, by the method, after the first detection voltage U1 and the second detection voltage U2 are obtained, the size relationship between the first detection voltage U1 and the preset voltage threshold is further determined, then the low-brightness signal and the high-brightness signal are correspondingly output according to the comparison result, it is determined that the ambient brightness is in the preset high-brightness interval or the preset low-brightness interval, and finally different PWM signals are correspondingly output according to the low-brightness signal and the high-brightness signal, so that the output of the PWM dimming signal is realized, the data processing process is simpler, and the processing efficiency is relatively higher.

The functions described in the embodiments of the present invention may be stored in a storage medium readable by a computing device if they are implemented in the form of software functional modules or units and sold or used as independent products. Based on such understanding, part of the contribution of the embodiments of the present invention to the prior art or part of the technical solution may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computing device (which may be a personal computer, a server, a mobile computing device, a network device, or the like) to execute all or part of the steps of the method described in the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes. The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.