Liquid crystal display circuit capable of realizing contrast adjustment of display screen

Abstract

The utility model discloses a liquid crystal display circuit capable of realizing contrast adjustment of a display screen, and belongs to the field of liquid crystal display circuits. Comprising a master control MCU, a power supply voltage stabilization unit, an upper computer interface unit, a display screen interface unit and a sampling voltage division unit. And the power supply voltage stabilizing unit, the upper computer interface unit, the display screen interface unit and the sampling voltage dividing unit are all connected with the main control MCU. An ADC module of the master control MCU can collect contrast regulation voltage ADCV0, the sampling and voltage dividing unit converts the ADCV0 voltage regulation range input by the master control MCU into the range of 0-3.3 through a resistance circuit and then outputs the ADCV0 voltage regulation range to the upper computer interface unit, an MCU program of an upper computer automatically calculates EV, Ratio and other numerical values according to the measured voltage, the numerical values are written into a screen driving chip, and the screen driving chip is used for driving the screen. Therefore, contrast adjustment of the display screen is realized. Through the design, the liquid crystal display module packaged by the COG can realize contrast adjustment on display screen hardware, is more convenient to use, and can be compatible with a liquid crystal module interface packaged by the COB.

Description

Technical Field

[0001] The utility model belongs to the field of liquid crystal display circuits, and in particular relates to a liquid crystal display circuit capable of realizing display screen contrast adjustment. Background Art

[0002] The existing LCD display module adopts the COB method to package the driver chip. For example, a black and white 128X64 LCD display module is usually driven by one AIP31107 and two AIP31108 driver chips. The driver chip is packaged on the gold-immersed PCBA in the COB method, and then the backlight source and electronic components are welded to the COB board to form a whole. Finally, the COB board and LCD (liquid crystal glass) are placed in the iron frame, and the COB gold finger and LCD conductive electrode are connected by conductive adhesive strips. The COB board is assembled into a finished product with 6 to 8 metal twist feet set on the iron frame.

[0003] This type of LCD module usually has a high cost because it uses more chips. The COB packaging process itself has more assembly steps and is complex. In addition, COB packaging must use a gold-plated board, which requires a larger PCB board area. The COB board and the LCD are connected with a conductive rubber strip, which makes the thickness of the entire LCD module larger. At the same time, when the metal twist pin is used to buckle the COB board, the strength of the metal twist pin manually twisted by the assembler is different, resulting in inconsistent compression ratios of the conductive rubber strips. The metal twist pin is very easy to loosen and hang in the air under transportation and vibration conditions. The compression ratio of the conductive rubber strip changes due to aging due to long-term use, which can easily cause poor contact between the COB board and the LCD, resulting in quality failures such as light and dark display and missing pixels. In general, the existing LCD modules based on COB packaging generally have the problem of poor assembly stability. As a mature chip packaging process, the COG chip packaging process can effectively solve the above problems.

[0004] However, since all LCD screens must have VR contrast adjustment, the adjustment methods include hardware adjustment of the display or software adjustment of the host. The COB process originally supports VR contrast hardware adjustment, but the VR contrast hardware adjustment of chips using COG process is generally software. Therefore, when the display driver chip is converted from COB to COG, it is necessary to change the VR contrast adjustment method from software adjustment to hardware adjustment through circuit design. Utility Model Content

[0005] In order to solve the above problems, the purpose of the utility model is to provide a liquid crystal display circuit capable of adjusting the contrast of a display screen, and capable of adjusting the contrast of the display screen hardware.

[0006] To achieve the above purpose, the technical solution of the utility model is as follows:

[0007] The utility model provides a liquid crystal display circuit capable of adjusting the contrast of a display screen, comprising:

[0008] Main control MCU;

[0009] A power supply voltage regulator unit for converting the power supply voltage;

[0010] A host computer interface unit for connecting to a host computer;

[0011] A display screen interface unit for connecting to a display screen;

[0012] Sampling voltage divider unit for display contrast adjustment;

[0013] The power supply voltage stabilization unit, the host computer interface unit, the display interface unit, and the sampling voltage dividing unit are all connected to the main control MCU;

[0014] The sampling voltage divider unit includes a capacitor C9, a capacitor C11, a resistor R3, a resistor R4, and a resistor R5. The capacitor C9 and the resistor R3 form a common end connected to the external input voltage signal VCC_5V; the capacitor C11 and the resistor R5 are connected in parallel, and one of the common ends of the two is grounded, and the other common end forms a common end with one end of the resistor R3 and the resistor R4 and is connected to the main control MCU, and the other end of the resistor R4 is connected to the host computer interface unit.

[0015] In this application, the power supply voltage regulator unit converts the input 5V power supply voltage into a 3.3V output voltage for use by the main control MCU and other modules. The ADC module of the main control MCU will collect the contrast adjustment voltage ADC_V0, and the sampling voltage divider unit converts the input ADC_V0 voltage adjustment range of the main control MCU into the range of 0 to 3.3 through a resistor circuit, and then outputs it to the host computer interface unit. The MCU program of the host computer automatically calculates the EV and Ratio and other values ​​according to the measured voltage, and writes them to the screen driver chip to achieve display contrast adjustment. Through the above design, the COG-packaged LCD display module can adjust the contrast on the display hardware, which is more convenient to use and compatible with the COB package interface.

[0016] Furthermore, the main control MCU includes U2 and resistor R6. The model of U2 is N32G430K8Q7. One end of the resistor R6 is grounded, and the other end is connected to the 31st pin of U2. The 14th pin of U2 is connected to the resistor R4.

[0017] Furthermore, the power supply voltage stabilization unit includes a voltage stabilizer U1, a capacitor C1, a capacitor C2, a capacitor C3, and a capacitor C4. One end of the capacitor C2 and the capacitor C4 form a common end connected to the external input voltage VCC_5V and connected to the third pin of the voltage stabilizer U1. The other end of the capacitor C2 and the capacitor C4 form a common end connected to the first pin of the voltage stabilizer U1. One end of the capacitor C1 and the capacitor C3 form a common end connected to the second pin and the fourth pin of the voltage stabilizer U1. The other end of the capacitor C1 and the capacitor C3 form a common end output voltage signal VCC_3V3. The power supply voltage stabilization unit converts the input 5V power supply voltage into a 3.3V output voltage for use by modules such as the main control MCU.

[0018] Further, the host computer interface unit includes an interface CON1, a capacitor C5, a capacitor C7, and a backlight interface module. The capacitor C5 and the capacitor C7 are connected in parallel, one end of the capacitor C5 and the capacitor C7 form a common end connected to the first pin of the interface CON1, and the other end of the capacitor C5 and the capacitor C7 and the second pin of the interface CON1 form a common end connected to the external input voltage signal VCC_5V; the backlight interface module is connected to the 19th and 20th pins of the interface CON1; the 3rd pin of the interface CON1 is connected to the resistor R4, the 4th pin of the interface CON1 is connected to the 25th pin of U2, the 5th pin of the interface CON1 is connected to the 18th pin of U2, the 6th pin of the interface CON1 is connected to the 19th pin of U2, and the interface CON The 7th pin of the interface CON1 is connected to the 6th pin of U2, the 8th pin of the interface CON1 is connected to the 7th pin of U2, the 9th pin of the interface CON1 is connected to the 8th pin of U2, the 10th pin of the interface CON1 is connected to the 9th pin of U2, the 11th pin of the interface CON1 is connected to the 10th pin of U2, the 12th pin of the interface CON1 is connected to the 11th pin of U2, the 13th pin of the interface CON1 is connected to the 12th pin of U2, the 14th pin of the interface CON1 is connected to the 13th pin of U2, the 15th pin of the interface CON1 is connected to the 20th pin of U2, the 16th pin of the interface CON1 is connected to the 21st pin of U2, and the 17th pin of the interface CON1 is connected to the 22nd pin of U2. The 19th pin of the interface CON1 is the A pin, and the 20th pin is the K pin, so as to realize the positive and negative connection of the backlight source.

[0019] Further, the backlight interface module includes a backlight interface BL, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, and a resistor R13, one end of the resistor R7, the resistor R8, and the resistor R9 forms a common end connected to the first pin of the backlight interface BL, and the other end forms a common end connected to the common end formed by the resistor R10 and the resistor R11; one end of the resistor R10 away from the resistor R7, the resistor R8, and the resistor R9 is connected to the 19th pin of CON1, and one end of the resistor R11 away from the resistor R7, the resistor R8, and the resistor R9 is connected to the external input voltage signal VCC_5V; one end of the resistor 12 and the resistor R13 forms a common end connected to the second pin of the backlight interface BL, the other end of the resistor R12 is grounded, and the other end of the resistor R13 is connected to the 20th pin of CON1.

[0020] Furthermore, the display screen interface unit includes an interface CON2 and a capacitor C10, the first pin of the interface CON2 is connected to the 15th pin of U2, the second pin is connected to the 30th pin of U2, and the third pin is connected to the 29th pin of U2, the fourth pin and the fifth pin form a common end to connect to the voltage signal VCC_3V3, the tenth, 11th, 12th, 13th, and 14th pins form a common end to connect to the voltage signal VCC_3V3, one end of the capacitor C10 is grounded, and the other end is connected to the 18th pin of the interface CON2.

[0021] Furthermore, the liquid crystal display circuit also includes an MCU clock crystal oscillator unit, which includes a crystal oscillator U3, a capacitor C13, and a capacitor C14. One end of the capacitor C13 is grounded, and the other end is connected to the second pin of the crystal oscillator U3 to form a common end connected to the third pin of U2. One end of the capacitor C14 is grounded, and the other end is connected to the first pin of the crystal oscillator U3 to form a common end connected to the second pin of U2, thereby realizing the MCU clock crystal oscillator function.

[0022] Furthermore, the liquid crystal display circuit also includes a reset unit, which includes a resistor R2 and a capacitor C6. One end of the capacitor C6 is grounded, and the other end forms a common end with the resistor R2 and is connected to the 4th pin of U2. The other end of the resistor R2 is connected to the voltage signal VCC_3V3.

[0023] Furthermore, the liquid crystal display circuit also includes an indication unit, which includes a resistor R1 and a light-emitting diode LED1. The resistor R1 and the light-emitting diode LED1 are connected in series, and the end of the resistor R1 away from the light-emitting diode LED1 is connected to the voltage signal VCC_3V3, and the end of the light-emitting diode LED1 away from the resistor R1 is grounded.

[0024] Furthermore, the liquid crystal display circuit also includes an MCU debugging unit, the MCU debugging unit includes a debugging interface P1, the first pin of the debugging interface P1 is connected to the voltage signal VCC_3V3, the second pin is connected to the 23rd pin of U2, the third pin is connected to the 24th pin of U2, and the fourth pin is grounded.

[0025] Furthermore, the liquid crystal display circuit also includes a first filtering unit, a second filtering unit, and a third filtering unit. The first filtering unit includes capacitor C15, capacitor C16, capacitor C17, capacitor C18, and capacitor C19. A common end formed by connecting the capacitors C15, capacitor C16, capacitor C17, capacitor C18, and capacitor C19 in parallel is connected to a voltage signal VCC_3V3, and the other common end is grounded. The second filtering unit includes capacitor C8, one end of the capacitor C8 is connected to a voltage signal VCC_3V3, and the other end is grounded. The third filtering unit includes capacitor C12, one end of the capacitor C12 is connected to a voltage signal VCC_3V3, and the other end is grounded.

[0026] Compared with the prior art, the beneficial effects of the utility model are: a sampling voltage divider unit is provided, the ADC module of the main control MCU will collect the contrast adjustment voltage ADC_V0, and the sampling voltage divider unit converts the ADC_V0 voltage adjustment range of the input of the main control MCU into the range of 0 to 3.3 through a resistor circuit, and then outputs it to the host computer interface unit. The MCU program of the host computer automatically calculates the values ​​such as EV and Ratio according to the measured voltage, and writes them into the screen driver chip, thereby realizing the contrast adjustment of the display screen. Through the above design, the COG-packaged liquid crystal display module can realize the contrast adjustment on the display screen hardware, which is more convenient to use and can also be compatible with the COB-packaged liquid crystal module interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the structural block diagram of the liquid crystal display circuit.

[0028] Figure 2 It is the circuit schematic diagram of the main control MCU.

[0029] Figure 3 It is the circuit schematic diagram of the sampling voltage divider unit.

[0030] Figure 4 This is the circuit diagram of the power supply voltage regulator unit

[0031] Figure 5 It is the circuit schematic diagram of the host computer interface unit.

[0032] Figure 6 This is the circuit schematic diagram of the display interface unit.

[0033] Figure 7This is the circuit schematic of the MCU clock crystal unit.

[0034] Figure 8 This is the circuit schematic of the MCU debugging unit.

[0035] Fig. 9 This is the circuit diagram of the reset unit

[0036] Fig.10 It is the circuit schematic diagram of the indicating unit.

[0037] Fig.11 Schematic diagram of the circuit of the first filtering unit.

[0038] Fig.12 It is the circuit schematic diagram of the second filtering unit.

[0039] Fig.13 It is a circuit schematic diagram of the third filtering unit. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0041] To achieve the above purpose, the technical solution of the utility model is as follows:

[0042] See also Figure 1-13 As shown, this embodiment provides a liquid crystal display circuit capable of adjusting the contrast of a display screen, including:

[0043] Main control MCU;

[0044] A power supply voltage regulator unit for converting the power supply voltage;

[0045] A host computer interface unit for connecting to a host computer;

[0046] A display screen interface unit for connecting to a display screen;

[0047] Sampling voltage divider unit for display contrast adjustment;

[0048] The power supply voltage stabilization unit, the host computer interface unit, the display interface unit, and the sampling voltage division unit are all connected to the main control MCU;

[0049] The sampling voltage divider unit includes capacitor C9, capacitor C11, resistor R3, resistor R4, and resistor R5. Capacitor C9 and resistor R3 form a common end to connect to the external input voltage signal VCC_5V; capacitor C11 and resistor R5 are connected in parallel, and one of the common ends of the two is grounded, and the other common end forms a common end with one end of resistor R3 and resistor R4 and is connected to the main control MCU, and the other end of resistor R4 is connected to the upper computer interface unit.

[0050] In this embodiment, the power supply voltage stabilization unit converts the input 5V power supply voltage into a 3.3V output voltage for use by the main control MCU and other modules. The ADC module of the main control MCU will collect the contrast adjustment voltage ADC_V0, and the sampling voltage divider unit converts the input ADC_V0 voltage adjustment range of the main control MCU into the range of 0 to 3.3 through a resistor circuit, and then outputs it to the host computer interface unit. The MCU program of the host computer automatically calculates the values ​​such as EV and Ratio according to the measured voltage, and writes it to the screen driver chip, thereby realizing the contrast adjustment of the display screen. Through the above design, the COG-packaged liquid crystal display module can realize the contrast adjustment on the display screen hardware, which is more convenient to use and can also be compatible with the COB package interface.

[0051] Furthermore, the main control MCU includes U2 and resistor R6. The model of U2 is N32G430K8Q7. One end of the resistor R6 is grounded, and the other end is connected to the 31st pin of U2. The 14th pin of U2 is connected to the resistor R4.

[0052] Furthermore, the power supply voltage stabilization unit includes a voltage stabilizer U1, a capacitor C1, a capacitor C2, a capacitor C3, and a capacitor C4. One end of the capacitor C2 and the capacitor C4 forms a common end connected to the external input voltage VCC_5V and connected to the third pin of the voltage stabilizer U1. The other end of the capacitor C2 and the capacitor C4 forms a common end connected to the first pin of the voltage stabilizer U1. One end of the capacitor C1 and the capacitor C3 forms a common end connected to the second pin and the fourth pin of the voltage stabilizer U1. The other end of the capacitor C1 and the capacitor C3 forms a common end output voltage signal VCC_3V3. The power supply voltage stabilization unit converts the input 5V power supply voltage into a 3.3V output voltage for use by modules such as the main control MCU.

[0053] Furthermore, the upper computer interface unit includes an interface CON1, a capacitor C5, a capacitor C7, and a backlight interface module. The capacitor C5 and the capacitor C7 are connected in parallel, one end of the capacitor C5 and the capacitor C7 form a common end connected to the first pin of the interface CON1, and the other end of the capacitor C5 and the capacitor C7 and the second pin of the interface CON1 form a common end connected to the external input voltage signal VCC_5V; the backlight interface module is connected to the 19th and 20th pins of the interface CON1; the 3rd pin of the interface CON1 is connected to the resistor R4, the 4th pin of the interface CON1 is connected to the 25th pin of U2, the 5th pin of the interface CON1 is connected to the 18th pin of U2, the 6th pin of the interface CON1 is connected to the 19th pin of U2, and the interface CON The 7th pin of interface CON1 is connected to the 6th pin of U2, the 8th pin of interface CON1 is connected to the 7th pin of U2, the 9th pin of interface CON1 is connected to the 8th pin of U2, the 10th pin of interface CON1 is connected to the 9th pin of U2, the 11th pin of interface CON1 is connected to the 10th pin of U2, the 12th pin of interface CON1 is connected to the 11th pin of U2, the 13th pin of interface CON1 is connected to the 12th pin of U2, the 14th pin of interface CON1 is connected to the 13th pin of U2, the 15th pin of interface CON1 is connected to the 20th pin of U2, the 16th pin of interface CON1 is connected to the 21st pin of U2, and the 17th pin of interface CON1 is connected to the 22nd pin of U2. The 19th pin of interface CON1 is the A pin, and the 20th pin is the K pin, which realizes the positive and negative connection of the backlight source.

[0054] Further, the backlight interface module includes a backlight interface BL, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, and a resistor R13. One end of the resistor R7, the resistor R8, and the resistor R9 forms a common end connected to the first pin of the backlight interface BL, and the other end forms a common end connected to the common end formed by the resistor R10 and the resistor R11; one end of the resistor R10 away from the resistor R7, the resistor R8, and the resistor R9 is connected to the 19th pin of CON1, and one end of the resistor R11 away from the resistor R7, the resistor R8, and the resistor R9 is connected to the external input voltage signal VCC_5V; one end of the resistor 12 and the resistor R13 forms a common end connected to the second pin of the backlight interface BL, the other end of the resistor R12 is grounded, and the other end of the resistor R13 is connected to the 20th pin of CON1.

[0055] Furthermore, the display screen interface unit includes an interface CON2 and a capacitor C10. The first pin of the interface CON2 is connected to the 15th pin of U2, the second pin is connected to the 30th pin of U2, the third pin is connected to the 29th pin of U2, the fourth pin and the fifth pin form a common end to connect to the voltage signal VCC_3V3, the 10th, 11th, 12th, 13th and 14th pins form a common end to connect to the voltage signal VCC_3V3, one end of the capacitor C10 is grounded, and the other end is connected to the 18th pin of the interface CON2.

[0056] Furthermore, the liquid crystal display circuit also includes an MCU clock crystal oscillator unit, which includes a crystal oscillator U3, a capacitor C13, and a capacitor C14. One end of the capacitor C13 is grounded, and the other end is connected to the second pin of the crystal oscillator U3 to form a common end connected to the third pin of U2. One end of the capacitor C14 is grounded, and the other end is connected to the first pin of the crystal oscillator U3 to form a common end connected to the second pin of U2, thereby realizing the MCU clock crystal oscillator function.

[0057] Furthermore, the liquid crystal display circuit also includes a reset unit, which includes a resistor R2 and a capacitor C6. One end of the capacitor C6 is grounded, and the other end forms a common end with the resistor R2 and is connected to the fourth pin of U2. The other end of the resistor R2 is connected to the voltage signal VCC_3V3.

[0058] Furthermore, the liquid crystal display circuit also includes an indication unit, which includes a resistor R1 and a light-emitting diode LED1. The resistor R1 and the light-emitting diode LED1 are connected in series, and the end of the resistor R1 away from the light-emitting diode LED1 is connected to the voltage signal VCC_3V3, and the end of the light-emitting diode LED1 away from the resistor R1 is grounded.

[0059] Furthermore, the liquid crystal display circuit also includes an MCU debugging unit, which includes a debugging interface P1, wherein the first pin of the debugging interface P1 is connected to the voltage signal VCC_3V3, the second pin is connected to the 23rd pin of U2, the third pin is connected to the 24th pin of U2, and the fourth pin is grounded.

[0060] Furthermore, the liquid crystal display circuit also includes a first filtering unit, a second filtering unit, and a third filtering unit. The first filtering unit includes capacitor C15, capacitor C16, capacitor C17, capacitor C18, and capacitor C19. A common end formed by connecting capacitors C15, capacitor C16, capacitor C17, capacitor C18, and capacitor C19 in parallel is connected to a voltage signal VCC_3V3, and the other common end is grounded; the second filtering unit includes capacitor C8, one end of capacitor C8 is connected to a voltage signal VCC_3V3, and the other end is grounded; the third filtering unit includes capacitor C12, one end of capacitor C12 is connected to a voltage signal VCC_3V3, and the other end is grounded.

[0061] Compared with the prior art, the beneficial effects of this embodiment are: a sampling voltage divider unit is provided, the ADC module of the main control MCU will collect the contrast adjustment voltage ADC_V0, and the sampling voltage divider unit converts the ADC_V0 voltage adjustment range of the input of the main control MCU into the range of 0 to 3.3 through a resistor circuit, and then outputs it to the host computer interface unit. The MCU program of the host computer automatically calculates the values ​​such as EV and Ratio according to the measured voltage, and writes them into the screen driver chip, thereby realizing the contrast adjustment of the display screen. Through the above design, the COG-packaged liquid crystal display module can realize the contrast adjustment on the display screen hardware, which is more convenient to use and can also be compatible with the COB-packaged liquid crystal module interface.

[0062] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid crystal display circuit capable of adjusting the contrast of a display screen, characterized in that: include: Main control MCU; A power supply voltage regulator unit for converting the power supply voltage; A host computer interface unit for connecting to a host computer; A display screen interface unit for connecting to a display screen; Sampling voltage divider unit for display contrast adjustment; The power supply voltage stabilization unit, the host computer interface unit, the display interface unit, and the sampling voltage dividing unit are all connected to the main control MCU; The sampling voltage divider unit includes a capacitor C9, a capacitor C11, a resistor R3, a resistor R4, and a resistor R5. The capacitor C9 and the resistor R3 form a common end connected to the external input voltage signal VCC_5V; the capacitor C11 and the resistor R5 are connected in parallel, and one of the common ends of the two is grounded, and the other common end forms a common end with one end of the resistor R3 and the resistor R4 and is connected to the main control MCU, and the other end of the resistor R4 is connected to the host computer interface unit.

2. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 1, characterized in that: The main control MCU includes U2 and resistor R6. The model of U2 is N32G430K8Q7. One end of the resistor R6 is grounded, and the other end is connected to the 31st pin of U2. The 14th pin of U2 is connected to the resistor R4.

3. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 2, characterized in that: The power supply voltage stabilization unit includes a voltage stabilizer U1, a capacitor C1, a capacitor C2, a capacitor C3, and a capacitor C4. One end of the capacitor C2 and the capacitor C4 form a common end connected to the external input voltage VCC_5V and connected to the third pin of the voltage stabilizer U1. The other end of the capacitor C2 and the capacitor C4 form a common end connected to the first pin of the voltage stabilizer U1; one end of the capacitor C1 and the capacitor C3 form a common end connected to the second pin and the fourth pin of the voltage stabilizer U1, and the other end of the capacitor C1 and the capacitor C3 form a common end output voltage signal VCC_3V3.

4. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 3, characterized in that: The host computer interface unit includes an interface CON1, a capacitor C5, a capacitor C7, and a backlight interface module. The capacitor C5 and the capacitor C7 are connected in parallel, one end of the capacitor C5 and the capacitor C7 form a common end connected to the first pin of the interface CON1, and the other end of the capacitor C5 and the capacitor C7 and the second pin of the interface CON1 form a common end connected to the external input voltage signal VCC_5V; the backlight interface module is connected to the 19th and 20th pins of the interface CON1; the 3rd pin of the interface CON1 is connected to the resistor R4, the 4th pin of the interface CON1 is connected to the 25th pin of U2, the 5th pin of the interface CON1 is connected to the 18th pin of U2, the 6th pin of the interface CON1 is connected to the 19th pin of U2, and the 10th pin of the interface CON1 is connected to the 11th pin of U2. The 7th pin of the interface CON1 is connected to the 6th pin of U2, the 8th pin of the interface CON1 is connected to the 7th pin of U2, the 9th pin of the interface CON1 is connected to the 8th pin of U2, the 10th pin of the interface CON1 is connected to the 9th pin of U2, the 11th pin of the interface CON1 is connected to the 10th pin of U2, the 12th pin of the interface CON1 is connected to the 11th pin of U2, the 13th pin of the interface CON1 is connected to the 12th pin of U2, the 14th pin of the interface CON1 is connected to the 13th pin of U2, the 15th pin of the interface CON1 is connected to the 20th pin of U2, the 16th pin of the interface CON1 is connected to the 21st pin of U2, and the 17th pin of the interface CON1 is connected to the 22nd pin of U2.

5. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 4, characterized in that: The backlight interface module includes a backlight interface BL, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, and a resistor R13. One end of the resistor R7, the resistor R8, and the resistor R9 forms a common end connected to the first pin of the backlight interface BL, and the other end forms a common end connected to the common end formed by the resistor R10 and the resistor R11; one end of the resistor R10 away from the resistor R7, the resistor R8, and the resistor R9 is connected to the 19th pin of CON1, and one end of the resistor R11 away from the resistor R7, the resistor R8, and the resistor R9 is connected to the external input voltage signal VCC_5V; one end of the resistor 12 and the resistor R13 forms a common end connected to the second pin of the backlight interface BL, the other end of the resistor R12 is grounded, and the other end of the resistor R13 is connected to the 20th pin of CON1.

6. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 5, characterized in that: The display screen interface unit includes an interface CON2 and a capacitor C10. The first pin of the interface CON2 is connected to the 15th pin of U2, the second pin is connected to the 30th pin of U2, and the third pin is connected to the 29th pin of U2. The fourth pin and the fifth pin form a common end to connect to the voltage signal VCC_3V3. The tenth, 11th, 12th, 13th, and 14th pins form a common end to connect to the voltage signal VCC_3V3. One end of the capacitor C10 is grounded, and the other end is connected to the 18th pin of the interface CON2.

7. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 3, characterized in that: The liquid crystal display circuit also includes an MCU clock crystal oscillator unit, which includes a crystal oscillator U3, a capacitor C13, and a capacitor C14. One end of the capacitor C13 is grounded, and the other end is connected to the second pin of the crystal oscillator U3 to form a common end and a connection with the third pin of U2. One end of the capacitor C14 is grounded, and the other end is connected to the first pin of the crystal oscillator U3 to form a common end and a connection with the second pin of U2.

8. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 3, characterized in that: The liquid crystal display circuit also includes a reset unit, which includes a resistor R2 and a capacitor C6. One end of the capacitor C6 is grounded, and the other end forms a common end with the resistor R2 and is connected to the fourth pin of U2. The other end of the resistor R2 is connected to the voltage signal VCC_3V3.

9. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 3, characterized in that: The liquid crystal display circuit also includes an indication unit, which includes a resistor R1 and a light emitting diode LED1. The resistor R1 and the light emitting diode LED1 are connected in series, and one end of the resistor R1 away from the light emitting diode LED1 is connected to a voltage signal VCC_3V3, and one end of the light emitting diode LED1 away from the resistor R1 is grounded.

10. A liquid crystal display circuit capable of adjusting the contrast of a display screen as claimed in claim 3, characterized in that: The liquid crystal display circuit also includes an MCU debugging unit, which includes a debugging interface P1. The first pin of the debugging interface P1 is connected to the voltage signal VCC_3V3, the second pin is connected to the 23rd pin of U2, the third pin is connected to the 24th pin of U2, and the fourth pin is grounded.

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