LCD screen backlight dimming circuit

Abstract

The backlight dimming circuit is characterized in that one end of a phototriode PD1 is connected with a + 5V power supply through an R73, and the other end of the phototriode PD1 is connected with an R81 and an R88 to form a voltage division circuit; the voltage of the PD1, the voltage of the R81 and the voltage of the R88 are connected with a three-end voltage-regulator tube N1, and the voltage-regulator circuit is composed of the N1, the R82, the R89, the C46 and the C47. The voltage at the B point, namely the upper end voltage of the R88, is the voltage formed by the photosensitive circuit and is input to the positive input end of the U8A through the R86 and the C44, the inverted input end of the U8A forms a follower through the R103, the output end of the U8A is connected with the R80 and the R102, and then a signal is input to a pin of the CPU. The method is convenient to implement and simple to control, each signal is high in anti-interference capability, power consumption can be effectively saved, and defects of a traditional scheme are overcome.

Description

Technical Field

[0001] The utility model relates to an LCD screen, in particular to an LCD screen backlight dimming circuit. Background Art

[0002] With the development and application of artificial intelligence and human-computer interaction, the green intelligent display and control corresponding to LCD screens have been more and more widely used in industries such as aerospace, computer peripherals, communication electronics, automotive electronics, robotics, numerical control, and consumer electronics. Whether it is a detection display or a control display, the screen needs to be able to present the operating status of various equipment or send some control instructions for intelligent, manual, and rational control. Faced with the ever-changing products and increasingly humanized and energy-saving needs, higher requirements are placed on the screen's life, power consumption, thickness, and environmental protection. Backlight dimming technology is the core technology of the LCD display industry, which is crucial to improving image quality, reducing energy consumption, and extending backlight life.

[0003] LCD is a passive light-emitting display that controls the distribution of liquid crystal molecules by voltage. Therefore, the LCD screen itself cannot emit light. It needs a backlight panel to provide it with power and communication control interface to adjust the display brightness and contrast. Currently, there are three types of backlight dimming technologies: one is PWM dimming technology that quickly switches the light source; the other is adaptive backlight dimming technology, which dynamically adjusts the backlight brightness based on the feedback of the light sensor.

[0004] 1. Technical solution of pulse width modulation (PWM):

[0005] Pulse width modulation (PWM) technology is a widely used LCD backlight dimming method. It is a dimming technology that uses simple digital pulses to repeatedly and quickly switch the LCD driver. R&D personnel output digital pulses with different duty cycles according to the current screen brightness and instructions, and then indirectly change the current output to the screen to adjust the brightness of the LCD;

[0006] Disadvantages of Pulse Width Modulation (PWM) technology:

[0007] Visual and auditory fatigue: PWM dimming technology uses fast light source switching to control brightness, which may cause visual fatigue, headaches or eye discomfort to some users. In addition, the LCD driver is equivalent to a switching device. If the PWM signal frequency is between 200Hz and 20KHz, the inductance and capacitance in the drive circuit can generate noise, affecting the customer's senses.

[0008] Color banding effect: Low-frequency PWM has discontinuities at the boundaries of interface refreshes or the edges of color transitions, which may lead to a "color banding effect", that is, visible rainbow stripes may appear at low brightness, affecting the visual experience.

[0009] Electromagnetic interference: PWM may cause electromagnetic interference, resulting in EMC failure and adversely affecting other parts of the electronic equipment.

[0010] 2. Adaptive backlight dimming technology solution

[0011] Adaptive backlight dimming technology is based on the feedback of the ambient light sensor, obtains the current screen backlight parameters, uses a certain dynamic dimming algorithm to calculate the required backlight brightness value, and then determines the output control signal, which can be a pulse signal or a current signal, and finally dynamically adjusts the backlight brightness to ensure the best display effect under different lighting conditions;

[0012] Disadvantages of adaptive control:

[0013] Sensor accuracy: The accuracy of ambient light sensors may be affected by changes in ambient light, resulting in unstable light reception and inaccurate dimming.

[0014] Complexity: Implementing an adaptive backlight dimming system requires complex control and feedback loops, which may cause system instability and increase manufacturing and maintenance costs.

[0015] Cost issue: Low-cost optical sensors may not meet production requirements, while high-performance optical sensors will undoubtedly increase development and production costs.

[0016] In view of this, the present utility model is proposed. Utility Model Content

[0017] The purpose of the utility model is to provide an LCD screen backlight dimming circuit to solve the above technical problems existing in the prior art.

[0018] The purpose of this utility model is achieved through the following technical solutions:

[0019] The LCD screen backlight dimming circuit of the utility model comprises:

[0020] One end of the phototransistor PD1 is connected to the +5V power supply through R73, and the other end is connected to R81 and R88 to form a voltage divider circuit;

[0021] The voltage of PD1, R81 and R88 is connected to the three-terminal voltage regulator N1, and the voltage regulator circuit is composed of N1, R82, R89, C46 and C47;

[0022] Point B, i.e., the voltage at the upper end of R88, is the voltage formed by the photosensitive circuit and is input to the positive input end of U8A through R86 and C44. The inverting input end of U8A forms a follower through R103. The output end of U8A is connected to R80 and R102, and then the signal is input to the pin of the CPU.

[0023] Compared with the prior art, the LCD screen backlight dimming circuit provided by the utility model can work in fixed backlight mode, manual dimming mode and automatic dimming mode. The fixed backlight and manual dimming modes only need to set relevant parameters. The automatic dimming mode is a process of automatically and real-time adjusting the backlight parameters according to the sensitivity of the phototransistor. This solution is convenient to implement and simple to control, and each signal has strong anti-interference ability, which can effectively save power consumption and make up for the disadvantages and defects of traditional solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of a circuit for converting the light sensitivity of a phototransistor into a voltage according to an embodiment of the utility model;

[0025] Figure 2 A schematic diagram of a circuit for real-time adjustment of the algorithm correction compensation of an embodiment of the utility model;

[0026] Figure 3 The present invention is a schematic diagram of a circuit for adjusting the backlight output signal of the current screen according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the utility model in conjunction with the drawings in the embodiments of the utility model; it is obvious that the described embodiments are only part of the embodiments of the utility model, not all of the embodiments, which does not constitute a limitation of the utility model. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

[0028] First, the terms that may be used in this article are explained as follows:

[0029] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0030] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0031] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0032] The contents not described in detail in the examples of the present utility model belong to the prior art known to professionals in the field. If no specific conditions are specified in the examples of the present utility model, the conditions are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used in the examples of the present utility model are not specified, they are all conventional products that can be purchased commercially.

[0033] The LCD screen backlight dimming circuit of the utility model comprises:

[0034] One end of the phototransistor PD1 is connected to the +5V power supply through R73, and the other end is connected to R81 and R88 to form a voltage divider circuit;

[0035] The voltage of PD1, R81 and R88 is connected to the three-terminal voltage regulator N1, and the voltage regulator circuit is composed of N1, R82, R89, C46 and C47;

[0036] Point B, i.e., the voltage at the upper end of R88, is the voltage formed by the photosensitive circuit and is input to the positive input end of U8A through R86 and C44. The inverting input end of U8A forms a follower through R103. The output end of U8A is connected to R80 and R102, and then the signal is input to the pin of the CPU.

[0037] The signal input to the CPU pin is collected, corrected and compensated by the CPU to form a level corresponding to the actual brightness, and is output to the BL_DA terminal through the pin. The BL_DA terminal is connected to R97 and C65 for filtering and then given to the positive input terminal 5 pin of U8B. The reverse input terminal 6 pin of U8B is connected to the output terminal 7 pin of U8B to form a follower, and its output terminal is connected through R71, C41 and R72, C38 to form a signal NL1.

[0038] Pin 3 of U7A is connected to the signal NL1 through R75;

[0039] Pin 2 of U7A is connected to the collected signal from the circuit itself, i.e., the signal at point C. After the signal is formed, it is input to pin 5 of U7B through R109 and R110. Pin 6 of U7B is connected to GND through R106 and R107. Pin 6 of U7B is also connected to pin 7 of the output terminal through R105. Pin 7 of the output terminal is connected to R92. R92 is connected to R108 and C62, and then filtered and input to pin 2 of U7A through R91.

[0040] Pin 4 of U7A is connected to GND, pin 8 is connected to the power supply +5V through R79 and C43, pin 2 is connected to the output end through C37, C42 and R74, the output end is connected to the b pole of transistor VT5 through R87 and C49, the b pole of VT5 is connected to GND through R94, the e pole of VT5 is connected to GND through the R93 resistor, and the c pole of VT5 is connected to the CPU control level through R78.

[0041] The above-mentioned LCD screen backlight dimming circuit realizes the method of LCD screen backlight dimming, comprising the steps of:

[0042] First, the phototransistor provides different impedances to the circuit according to the light sensitivity, and then inputs the voltage to the AD sampling module of the CPU after filtering. The relationship is that the more fully the light-sensitive transistor is, the smaller its internal resistance is, the less the transistor voltage is divided, the greater the voltage drop at point B, and the corresponding BL_DA setting value is also greater;

[0043] Secondly, according to the value obtained by converting the light sensitivity of the phototransistor into voltage and sampling, the algorithm correction compensation is adjusted in real time, and the DA module of the embedded chip outputs the level BL_DA, which is filtered, followed and filtered to obtain a clean and stable signal NL1;

[0044] Then, the two signals input to the error amplifier are signal NL1 and the screen dimming voltage value fed back from the circuit itself. The positive input terminal is signal NL1, which is given by the program and forms a relatively stable level after following filtering; the value of the negative input terminal is the voltage value obtained by sampling the current screen brightness at point C and amplified by 100 times. These two signals are output by the error amplifier to adjust the backlight of the current screen.

[0045] In summary, the LCD screen backlight dimming circuit of the embodiment of the utility model is a new backlight dimming control technology, that is, a multi-mode backlight dimming technology. It can work in fixed backlight mode, manual dimming mode and automatic dimming mode. The fixed backlight and manual dimming modes only need to set relevant parameters. The automatic dimming mode is a process of automatically adjusting the backlight parameters in real time according to the sensitivity of the phototransistor. This solution is easy to implement and simple to control, and each signal has strong anti-interference ability, which can effectively save power consumption and make up for the disadvantages and defects of traditional solutions;

[0046] It solves the problems of poor perception and interference in traditional control methods; solves the problems of high cost, low precision and complex circuits in traditional control methods; eliminates screen operation risks and improves system reliability.

[0047] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the embodiments of the present invention are described in detail with specific embodiments below.

[0048] Example 1

[0049] like Figures 1 to 3 As shown, the specific implementation scheme of the utility model is as follows:

[0050] Fixed mode, that is, BL_ON is set to a low level. At this time, the backlight dimming circuit is not controlled and the default factory backlight mode is used.

[0051] Manual mode, that is, BL_ON is set to a high level, at this time the backlight circuit is enabled, and the human-computer interaction interface gives a certain ratio, and the interface adjusts the backlight brightness according to this ratio.

[0052] Automatic mode, that is, BL_ON is given a high level, and the backlight circuit is enabled.

[0053] The hardware circuit of this solution is described as follows:

[0054] like Figure 1 As shown, one end of the phototransistor PD1 SPT-313T1CT is connected to the +5V power supply through R73, and the other end is connected to R81 and R88 to form a voltage divider circuit. The voltages of PD1, R81 and R88 are connected to the three-terminal voltage regulator N1 TL431, and the voltage regulator circuit is composed of N1, R82, R89, C46 and C47. Point B, i.e., the voltage on the upper end of R88, is the voltage formed by the photosensitive circuit, which is input to the positive input end of U8A SGM8582 through R86 and C44. The inverting input end of U8A forms a follower through R103, and the output end of U8A is connected to R80 and R102, after which the signal is input to the pin of the CPU.

[0055] like Figure 2 As shown, the signal input to the CPU pin is collected, corrected and compensated by the CPU to form a level corresponding to the actual brightness, and then output to the BL_DA terminal through the pin. BL_DA is connected to R97 and C65 for filtering and then given to the positive input terminal 5 of U8B SGM8582. The reverse input terminal 6 of U8B SGM8582 is connected to the output terminal 7 of U8B to form a follower. Its output terminal is connected through R71 C41 and R72C38 to form a signal NL1.

[0056] like Figure 3 As shown, the description is as follows:

[0057] Pin 3 of U7A is connected to the NL1 signal through R75.

[0058] Pin 2 of U7A is connected to the collected signal from the circuit itself, that is, the point C signal. After this signal is formed, it is input to pin 5 of U7B through R109R110. Pin 6 of U7B is connected to GND through R106 R107, and pin 6 is also connected to the output terminal pin 7 through R105. The output terminal pin 7 is connected to R92, and R92 is connected to R108 and C62 for filtering, and then input to pin 2 of U7A through R91.

[0059] Pin 4 of U7A is connected to GND, pin 8 is connected to the power supply +5V through R79 and C43, pin 2 is connected to the output end through C37, C42 and R74, the output end is connected to the b pole of transistor VT5 through R87 and C49, the b pole of VT5 is connected to GND through R94, the e pole of VT5 is connected to GND through the R93 resistor, and the c pole of VT5 is connected to the CPU control level through R78.

[0060] The example principle is as follows:

[0061] First, the phototransistor provides different impedances to the circuit according to the light sensitivity, and then inputs the voltage to the AD sampling module of the CPU after filtering. The relationship is that the more fully the light sensitive the phototransistor is, the smaller its internal resistance is, the less the voltage division of the transistor is, the greater the voltage drop at point B is, and the corresponding BL_DA setting value is also greater. The circuit schematic diagram is as follows Figure 1 As shown:

[0062] Secondly, according to the value obtained by converting the light sensitivity of the phototransistor into voltage and sampling, the algorithm correction compensation is adjusted in real time, and the output level BL_DA is output through the DA module of the embedded chip. BL_DA is filtered, followed and filtered to obtain a clean and stable signal NL1. The circuit schematic diagram is as follows Figure 2 As shown:

[0063] Then, the two signals input to the error amplifier are signal NL1 and the screen dimming voltage value fed back from the circuit itself. The positive input terminal is signal NL1, which is given by the program and forms a relatively stable level after following the filter; the value of the negative input terminal is the voltage value obtained by sampling the current screen brightness at point C and amplified by 100 times. These two signals are output by the error amplifier to adjust the backlight of the current screen. The circuit schematic diagram is as follows Figure 3 shown.

[0064] The beneficial effects brought by the technical solution of the utility model are:

[0065] Since this solution uses phototransistors with a large impedance variation range and a small size, the backlight adjustment range is large, which improves the sense of perception. In addition, there is no circuit noise, which does not affect the EMC evaluation of the machine. The traditional PWM pulse control method requires strict control of the operating frequency to avoid interference.

[0066] Since the circuit of this scheme uses the most basic components such as resistors, transistors, capacitors and op amps, the circuit is simple, stable, intuitive, easy to debug and maintain, and has low cost. Traditional photoresistors have a small adjustment range and large size, limited light control range, and low accuracy.

[0067] The transmission of key signals is processed through circuit filtering to reduce signal interference or signal attenuation and distortion, making the entire system more stable and reliable and reducing the potential risk of system collapse.

[0068] In a specific implementation, the signal amplifier can be replaced by a single-ended proportional amplifier, or it can be implemented by building a differential amplifier or a single-ended amplifier using discrete devices such as transistors and MOS field effect transistors.

[0069] The error amplifier in this control method can also be replaced by a more complex type II or type III error amplifier solution, or it can be implemented by building a differential amplifier or a single-ended amplifier using discrete devices such as transistors and MOS field effect transistors.

[0070] The embedded chip in this solution can be ARM, DSP or FPGA.

[0071] The technical key points of the utility model are as follows:

[0072] The backlight dimming solution jointly controlled by the analog circuit and embedded chip in this solution saves power consumption, improves anti-interference ability and system stability. It can also support three modes of operation, meeting the requirements of a multi-mode working environment;

[0073] By using the voltage stabilization and voltage division circuit of the phototransistor, a stable and sufficient dimming range is provided for the system;

[0074] The microsystem provides a reliable control system by collecting the backlight voltage in real time and feeding it back to the error amplifier and controlling the backlight brightness together with the program.

[0075] The above is only a preferred specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the utility model should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the utility model, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. An LCD screen backlight dimming circuit, characterized in that: include: One end of the phototransistor PD1 is connected to the +5V power supply through R73, and the other end is connected to R81 and R88 to form a voltage divider circuit; The voltage of PD1, R81 and R88 is connected to the three-terminal voltage regulator N1, and the voltage regulator circuit is composed of N1, R82, R89, C46 and C47; Point B, i.e., the voltage at the upper end of R88, is the voltage formed by the photosensitive circuit and is input to the positive input end of U8A through R86 and C44. The inverting input end of U8A forms a follower through R103. The output end of U8A is connected to R80 and R102, and then the signal is input to the pin of the CPU.

2. The LCD screen backlight dimming circuit according to claim 1, characterized in that: The signal input to the CPU pin is collected, corrected and compensated by the CPU to form a level corresponding to the actual brightness, and is output to the BL_DA terminal through the pin. The BL_DA terminal is connected to R97 and C65 for filtering and then given to the positive input terminal 5 pin of U8B. The reverse input terminal 6 pin of U8B is connected to the output terminal 7 pin of U8B to form a follower, and its output terminal is connected through R71, C41 and R72, C38 to form a signal NL1.

3. The LCD screen backlight dimming circuit according to claim 2, characterized in that: Pin 3 of U7A is connected to the signal NL1 through R75; Pin 2 of U7A is connected to the collected signal from the circuit itself, i.e., the signal at point C. After the signal is formed, it is input to pin 5 of U7B through R109 and R110. Pin 6 of U7B is connected to GND through R106 and R107. Pin 6 of U7B is also connected to pin 7 of the output terminal through R105. Pin 7 of the output terminal is connected to R92. R92 is connected to R108 and C62, and then filtered and input to pin 2 of U7A through R91. Pin 4 of U7A is connected to GND, pin 8 is connected to the power supply +5V through R79 and C43, pin 2 is connected to the output end through C37, C42 and R74, the output end is connected to the b pole of transistor VT5 through R87 and C49, the b pole of VT5 is connected to GND through R94, the e pole of VT5 is connected to GND through the R93 resistor, and the c pole of VT5 is connected to the CPU control level through R78.

Images