Display driving circuit, module and electronic device

Abstract

The application discloses a display driving circuit, a module and an electronic device. The circuit comprises a voltage dividing circuit and an MCU. The voltage dividing circuit comprises a first resistor, a second resistor and a third resistor which are equal in resistance and connected in series. The MCU is provided with a first IO terminal and a second IO terminal, a plurality of COM terminals and a plurality of SEG terminals. The MCU applies positive and negative alternating alternating levels between the SEG terminals and the COM terminals by switching the high / low level output of the first IO terminal and the second IO terminal, and drives the plurality of COM terminals by time-sharing scanning to realize the display driving of the liquid crystal screen. The application can realize the display driving of the liquid crystal screen with one-third bias voltage ratio by using a conventional MCU, and is low in cost and convenient for chip selection and mass production.

Description

Technical Field

[0001] This application relates to the field of liquid crystal displays, and in particular to a display driving circuit, module, and electronic device. Background Technology

[0002] Existing TN LCD screens with a one-third bias ratio require a dedicated MCU capable of outputting 1 / 3VDD LCD driver ports. Such specialized MCUs are expensive and hinder chip selection and mass production. If a MCU with a standard I / O port could be used to simulate a dedicated LCD driver port to drive the LCD screen, it would significantly broaden the range of MCU options and reduce costs.

[0003] In related technologies, LCD screens achieve display by applying alternating positive and negative voltage levels between the SEG and COM pins. Conventional solutions using ordinary I / O ports to simulate LCD driver ports typically use two equal-value upper and lower voltage divider resistors (the upper resistor connected to VDD, the lower resistor grounded, and the series connection of the upper and lower resistors connected to the I / O port) connected externally to the I / O port or built into the MCU chip to simulate each COM port driving the LCD. When the I / O port is set to output high or low, the COM pin of the LCD connected to that I / O port is at a high level (VDD) or low level (ground), and the voltage difference between it and SEG is VDD or 0V, resulting in a display on the LCD. When the I / O port is set to a high-impedance input state, the COM pin of the LCD connected to the I / O port is divided by 1 / 2VDD. The voltage drop between the SEG and COM pins of the LCD is only 1 / 2VDD. For an LCD with a 1 / 2 bias ratio, a voltage drop of 1 / 2VDD between the SEG and COM pins is sufficient to prevent display, thus posing no problem.

[0004] However, for LCD screens with a 1 / 3 bias ratio, the voltage drop between the SEG pin and the COM pin needs to be reduced to 1 / 3 VDD to prevent display. The conventional solution of reducing the voltage drop between the SEG pin and the COM pin to 1 / 2 VDD will cause the LCD screen to fail to completely prevent display and may result in ghosting. This problem needs to be solved. Summary of the Invention

[0005] This application proposes a display driver circuit, module, and electronic device. The display driver for a liquid crystal screen with a one-third bias ratio can be achieved using a conventional MCU with a conventional I / O port. This method is low in cost and facilitates chip selection and mass production material preparation.

[0006] A display driving circuit according to an embodiment of the first aspect of this application is used to drive a liquid crystal screen with a one-third bias ratio, comprising:

[0007] The voltage divider circuit includes three resistors of equal resistance connected in series: a first resistor, a second resistor, and a third resistor.

[0008] The MCU has a first I / O terminal, a second I / O terminal, multiple COM terminals, and multiple SEG terminals. A first resistor is connected to the first I / O terminal, and a third resistor is connected to the second I / O terminal. The common terminal VCOM of the first and second resistors is connected to the multiple COM terminals through a fourth resistor, and the common terminal VSEG of the second and third resistors is connected to the multiple SEG terminals through a fifth resistor. The multiple COM terminals are used to connect to the corresponding COM pins of the LCD screen, and the multiple SEG terminals are used to connect to the corresponding SEG pins of the LCD screen. The voltage difference between the first I / O terminal and the second I / O terminal is VDD.

[0009] The MCU switches the high / low level output of the first IO terminal and the second IO terminal to apply alternating positive and negative levels between the SEG terminal and the COM terminal. It also drives multiple COM terminals to scan sequentially through time-division scanning, so that the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is in display mode is ±VDD, and the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is not in display mode is ±1 / 3VDD, thereby realizing the display driving of the LCD screen.

[0010] According to some embodiments of this application, the resistance values ​​of the fourth resistor and the fifth resistor are both Ra, and the resistance values ​​of the first resistor, the second resistor, and the third resistor are all Rb. The resistance values ​​of the first resistor, the second resistor, the third resistor, the fourth resistor, and the fifth resistor satisfy the following formula:

[0011] Ra≥Rb*200.

[0012] According to some embodiments of this application, the number of COM terminals is greater than or equal to four.

[0013] According to some embodiments of this application, the number of SEG terminals is greater than or equal to four.

[0014] A display driving module according to a second aspect of this application includes the display driving circuit described in the first aspect embodiment.

[0015] An electronic device according to a third aspect of this application includes the display driver module described in the second aspect embodiment.

[0016] A display driving circuit, module, and electronic device according to an embodiment of this application have at least the following beneficial effects:

[0017] In this embodiment, the first and second I / O terminals of the MCU are connected in series via three resistors of equal value: a first resistor, a second resistor, and a third resistor. By switching the high and low levels of the first and second I / O terminals while maintaining a voltage difference of VDD between them, the MCU can generate a voltage level of 1 / 3VDD or 3 / 2VDD at the COM or SEG terminal. The MCU applies alternating positive and negative voltage levels between the SEG and COM terminals and drives multiple COM terminals to scan sequentially using time-division scanning. This ensures that the voltage difference between the SEG pin and the corresponding COM pin when the LCD is in display mode is ±VDD, and the voltage difference between the SEG pin and the corresponding COM pin when the LCD is not in display mode is ±1 / 3VDD, thus achieving display driving for the LCD. This application eliminates the need for a dedicated LCD driver MCU; a conventional I / O port MCU can achieve display driving for an LCD with a one-third bias ratio, resulting in low cost and facilitating chip selection and mass production.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0020] Figure 1 This is a circuit diagram of the display driving circuit in an embodiment of this application;

[0021] Figure 2 This is a circuit diagram of the display scanning circuit of 2COM×2SEG in the embodiment of this application. Detailed Implementation

[0022] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] In the description of this application, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] In the description of this application, "multiple" refers to two or more. The use of "first" and "second" is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or the order in which the technical features are indicated.

[0025] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0026] Reference Figure 1 As shown, a display driver circuit for driving a liquid crystal display (LCD) with a one-third bias ratio includes a voltage divider circuit and an MCU. Specifically, the voltage divider circuit includes three resistors of equal resistance connected in series: a first resistor, a second resistor, and a third resistor. The MCU has a first I / O terminal IO1, a second I / O terminal IO2, multiple COM terminals, and multiple SEG terminals. The first resistor is connected to the first I / O terminal, and the third resistor is connected to the second I / O terminal. The common terminal VCOM of the first and second resistors is connected to the multiple COM terminals through a fourth resistor, and the common terminal VSEG of the second and third resistors is connected to the multiple SEG terminals through a fifth resistor. The multiple COM terminals are used to connect to the corresponding COM pins of the LCD, and the multiple SEG terminals are used to connect to the corresponding SEG pins of the LCD. The voltage difference between the first I / O terminal and the second I / O terminal is VDD.

[0027] The MCU switches the high / low level output of the first IO terminal and the second IO terminal to apply alternating positive and negative levels between the SEG terminal and the COM terminal. It also drives multiple COM terminals to scan sequentially through time-division scanning, so that the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is in display mode is ±VDD, and the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is not in display mode is ±1 / 3VDD, thereby realizing the display driving of the LCD screen.

[0028] In this embodiment, the first and second I / O terminals of the MCU are connected in series via three resistors of equal value: a first resistor, a second resistor, and a third resistor. By switching the high and low levels of the first and second I / O terminals while maintaining a voltage difference of VDD between them, the MCU can generate a voltage level of 1 / 3VDD or 3 / 2VDD at the COM or SEG terminal. The MCU applies alternating positive and negative voltage levels between the SEG and COM terminals and drives multiple COM terminals to scan sequentially using time-division scanning. This ensures that the voltage difference between the SEG pin and the corresponding COM pin when the LCD is in display mode is ±VDD, and the voltage difference between the SEG pin and the corresponding COM pin when the LCD is not in display mode is ±1 / 3VDD, thus achieving display driving for the LCD. This application eliminates the need for a dedicated LCD driver MCU; a conventional I / O port MCU can achieve display driving for an LCD with a one-third bias ratio, resulting in low cost and facilitating chip selection and mass production.

[0029] In this embodiment, the first resistor is resistor R1, the second resistor is resistor R2, and the third resistor is resistor R3. The first IO terminal IO1 is connected to the second IO terminal IO2 through resistors R1, R2, and R3 connected in series. The connection between resistors R1 and R2 is connected to the VCOM terminal, and the connection between resistors R2 and R3 is connected to the VSEG terminal. Each COM terminal of the MCU is connected to the corresponding COM pin of the LCD screen, and each SEG terminal of the MCU is connected to the corresponding SEG pin of the LCD screen. Each COM terminal is connected to the VCOM terminal through a fourth resistor, and each SEG terminal is connected to the VSEG terminal through a fifth resistor. In this embodiment, the MCU has four COM terminals and seven SEG terminals, namely COM0, COM1, COM2, and COM3, and SEG0, SEG1, SEG2, SEG3, SEG4, SEG5, and SEG6; the fourth resistor includes resistors R4, R5, R6, and R7, and the fifth resistor includes resistors R8, R9, R10, R11, R12, R13, R14, and R15. The MCU's COM1, COM2, COM3, and COM4 are connected to the VCOM terminal via R4, R5, R6, and R7, respectively, and the MCU's SEG1, SEG2, SEG3, SEG4, SEG5, SEG6, and SEG7 are connected to the VSEG terminal via R8, R9, R10, R11, R12, R13, R14, and R15, respectively.

[0030] Since LCD screens require an alternating voltage between the COM and SEG pins to display correctly, the MCU in this application can generate 1 / 3VDD or 2 / 3VDD at the VCOM or VSEG pins by applying alternating positive and negative voltage levels between the SEG and COM pins. For example, when the MCU's first IO pin IO1 outputs a high level VDD and the second IO pin IO2 outputs a low level 0V, VCOM = 2 / 3VDD and VSEG = 1 / 3VDD. When the MCU's second IO pin IO2 outputs a high level VDD and the first IO pin IO1 outputs a low level 0V, VCOM = 2 / 3VDD and VSEG = 1 / 3VDD.

[0031] The above-mentioned time-division scanning method drives multiple COM terminals to scan sequentially. This means that the MCU drives the LCD screen display through time-division scanning of COM1, COM2, COM3, and COM4. By utilizing the visual persistence effect of the human eye, the display images scanned in time-division are strung together to form a complete LCD screen display.

[0032] It should be noted that for an LCD screen with a one-third bias ratio, four voltages need to be generated between the COM and SEG pins: 0V, 1 / 3VDD, 2 / 3VDD, and VDD. When the voltage difference between the COM and SEG pins is ±VDD, the corresponding icons will display normally. When the voltage difference is ≤1 / 3VDD, the corresponding icons will not display. When the voltage difference is 2 / 3VDD, the LCD screen will display "ghosting," a visual malfunction characterized by unwanted image residue or blurry, repeating images on the screen. Therefore, to ensure normal display, the voltage difference between the COM and SEG pins of an LCD screen with a one-third bias ratio needs to be controlled to ±VDD. To prevent display, the voltage difference must be ≤±1 / 3VDD. Therefore, in this application, multiple COM pins are scanned sequentially by time-division scanning, so that the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is in display mode is ±VDD, and the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is not in display mode is ±1 / 3VDD, so as to realize the display driving of the LCD screen and avoid ghosting.

[0033] The following is a detailed process of time-sharing scanning. Multiple COM ports are scanned sequentially using time-sharing scanning. Taking the scanning order of COM1-COM4 as an example, the specific process is as follows:

[0034] When it's COM1's turn to scan, the MCU's COM1 pin first outputs a high level (VDD). All other COM pins of the MCU are set to a high-impedance input state. At this time, the SEG pins of MCUs that don't display are set to a high-impedance input state, while the SEG pins of MCUs that need to display output a low level (0V). Because the voltage difference between the corresponding SEG pin on the LCD and the COM1 pin is VDD, a display occurs. The MCU's first I / O pin (IO1) outputs a low level (0V), and the MCU's second I / O pin (IO2) outputs a high level (VDD). The voltages of the other COM pins on the LCD are equal to the VCOM pin voltage (1 / 3 VDD). The voltages of the SEG pins on the LCD that don't need to display are equal to the VSEG pin voltage (2 / 3 VDD). Since the voltage difference between these pins and all COM pins remains at 1 / 3 VDD, no display occurs. Because the LCD screen requires an alternating voltage between the COM and SEG pins to display correctly, the MCU's COM1 pin switches to a low output level (0V), while the remaining COM pins of the MCU remain in a high-impedance input state. The SEG pins of the MCUs that are not displaying also remain in a high-impedance input state, while the SEG pins of the MCUs that need to display switch to a high output level (VDD), maintaining the voltage difference between the SEG pins and COM1. The MCU's first I / O pin (IO1) switches to a high output level (VDD), and the MCU's second I / O pin (IO2) switches to a low output level (0V). The voltages of the other COM pins of the LCD screen equal the VCOM pin voltage (2 / 3 VDD), and the voltages of the SEG pins that are not displaying equal the VSEG pin voltage (1 / 3 VDD). Maintaining the original voltage difference of 1 / 3 VDD between the SEG pins and all COM pins, there will be no display.

[0035] Next, COM2 is scanned. The MCU's COM2 pin first outputs a high level VDD. The remaining COM pins of the MCU (including COM1) are set to a high-impedance input state. At this time, the SEG pins of the MCUs that do not need to display are set to a high-impedance input state, while the SEG pins of the MCUs that need to display output a low level 0V. The voltage difference between these SEG pins and the COM2 pin is VDD, resulting in a display. The MCU's first IO pin IO1 outputs a low level 0V, and the MCU's second IO pin IO2 outputs a high level VDD. The voltage of the other COM pins of the LCD screen (including COM1) = VCOM pin voltage = 1 / 3 VDD. The voltage of the SEG pins of the LCD screen that do not need to display = VSEG pin voltage = 2 / 3 VDD. The voltage difference between the SEG pins that do not need to display and all COM pins remains at 1 / 3 VDD, therefore there is no display.

[0036] Similarly, since the LCD screen requires an alternating voltage between the COM and SEG pins to display correctly, the MCU's COM2 pin switches to a low output level of 0V, while the remaining COM pins of the MCU remain in a high-impedance input state. At this time, the SEG pins of the MCUs that do not require display remain in a high-impedance input state, while the SEG pins of the MCUs that require display switch to a high output level of VDD, maintaining the voltage difference of VDD between them and COM2. The MCU's first IO pin IO1 switches to a high output level of VDD, and the MCU's second IO pin IO2 switches to a low output level of 0V. The voltages of the other COM pins of the LCD screen equal the VCOM pin voltage (2 / 3 VDD), and the voltages of the SEG pins that do not require display equal VSEG (1 / 3 VDD). Maintaining the original voltage difference of 1 / 3 VDD between these pins and all COM pins, there is no display.

[0037] Similarly, the scanning process for COM3 and COM4 follows the same logic.

[0038] Because a fourth resistor is connected in series between each COM terminal and the VCOM terminal of the MCU, and a fifth resistor is connected in series between each SEG terminal and the VSEG terminal, the possibility of affecting the existing VCOM and VSEG terminal voltages is reduced when a certain COM or SEG terminal of the MCU outputs a high level (VDD) or a low level (0V). Due to the presence of resistors R4 to R15, when the COM or SEG terminal of the MCU is set to a high-impedance input state, the SEG pin of the LCD screen corresponds to the VSEG terminal voltage. Through the above circuitry and MCU program control, normal display driving can be achieved using an MCU with ordinary I / O ports for an LCD screen with a one-third bias ratio, saving costs.

[0039] In some implementations, the resistance values ​​of the fourth and fifth resistors are both Ra, and the resistance values ​​of the first, second, and third resistors are all Rb. The resistance values ​​of the first, second, third, fourth, and fifth resistors satisfy the following formula:

[0040] Ra≥Rb*200.

[0041] In this embodiment, by making the resistance values ​​of the fourth and fifth resistors much greater than or equal to the resistance values ​​of the first, second, and third resistors, it is possible to avoid the low-level output of the MCU's COM and SEG terminals affecting the voltage values ​​of the VCOM and VSEG terminals, thereby improving the reliability of the display driver.

[0042] The above Ra≥Rb*200 means that the resistance value of resistors R4 to R15 should be 200 times or more greater than the resistance values ​​of resistors R1, R2 and R3.

[0043] For example, in this embodiment, resistors R1, R2, and R3 are selected as identical resistors with a resistance value of 3.3K to 4.7K, and resistors R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, and R15 are selected as identical resistors with a resistance value of 680K to 1M.

[0044] Since the resistance values ​​of R4 to R15, which are connected in series between each COM port and VCOM terminal of the MCU, and between each SEG port and VSEG terminal, are much larger than the resistance values ​​of R1, R2, and R3, when a certain COM port or SEG port of the MCU outputs a high level VDD or a low level 0V, the possibility of affecting the existing VCOM terminal voltage and VSEG terminal voltage is further reduced, ensuring the normal display effect.

[0045] In some implementations, the number of COM terminals is greater than or equal to four, and the number of SEG terminals is greater than or equal to four.

[0046] In this embodiment, the MCU is provided with at least four COM ports and at least four SEG ports, which can accommodate more types of displays. For example, this embodiment has four COM ports and seven SEG ports on the MCU.

[0047] refer to Figure 2 As shown, the working process of this application for a liquid crystal screen with a one-third bias ratio is explained in detail using a 2COM×2SEG display scanning circuit as an example. Specifically, the 2COM×2SEG display scanning circuit includes four pins: COM1, COM2, SEG1, and SEG2. Let A, B, C, and D be the four icons on the liquid crystal screen. Referring to Table 1, the specific display driving process is as follows:

[0048] Table 1 Truth Table for LCD Display Driver

[0049]

[0050] At time T1, the MCU's COM1 pin is scanned, while the COM2 pin is not scanned and is set to a high-impedance input state. The MCU's first I / O pin IO1 outputs a low level (0V), and the MCU's second I / O pin IO2 outputs a high level (VDD), where VCOM = 1 / 3VDD and VSEG = 2 / 3VDD. When the MCU's COM1 pin outputs a high level (VDD), if the "A" icon corresponding to COM1 and SEG1 on the LCD screen is to be displayed, the MCU's SEG1 pin outputs a low level (0V), and the voltage difference between the COM1 and SEG1 pins on the LCD screen is VDD, thus displaying the "A" icon. If the "A" icon is not needed, the MCU's SEG1 pin is set to a high-impedance input state. In this case, the voltage at the SEG1 pin of the LCD screen = VSEG = 2 / 3VDD, and the voltage difference between the COM1 and SEG1 pins is 1 / 3VDD, so no display occurs. If the "C" icon corresponding to COM1 and SEG2 on the LCD screen is to be displayed, the MCU's SEG2 pin outputs a low level (0V), and the voltage difference between COM1 and SEG2 on the LCD screen is VDD, thus displaying the "C" icon. If the C icon is not needed, the MCU's SEG2 pin is set to a high-impedance input state. At this time, the voltage at the SEG2 pin of the LCD screen is VSEG = 2 / 3 VDD, and the voltage difference between the COM1 and SEG2 pins of the LCD screen is 1 / 3 VDD, so no display is possible. Since the MCU's COM2 pin is set to a high-impedance input state, the LCD screen's COM2 pin voltage is VCOM = 1 / 3 VDD. Whether the LCD screen needs the A or C icon to be displayed (making the MCU's SEG1 or SEG2 pins output a low level of 0V), or it doesn't need to display the A or C icon (making the MCU's SEG1 or SEG2 pins set to a high-impedance input state, where the SEG pin voltage is VSEG = 2 / 3 VDD), the voltage difference between the SEG1 and COM2 pins, and between the SEG2 and COM2 pins of the LCD screen, is only 1 / 3 VDD. Therefore, during the COM1 scan and high-level VDD output period, the B and D icons corresponding to COM2 do not need to be displayed.

[0051] At time T2, the MCU's COM1 output changes to a low level (0V), COM2 is not scanned, and COM2 remains in a high-impedance input state. The MCU's first I / O pin (IO1) switches to a high level (VDD), and the MCU's second I / O pin (IO2) switches to a low level (0V). VCOM = 2 / 3 VDD, VSEG = 1 / 3 VDD. To keep the "A" icon corresponding to COM1 and SEG1 on the LCD screen displayed, the MCU's SEG1 pin switches to a high level (VDD), and the voltage difference between COM1 and SEG1 on the LCD screen remains VDD. If the "A" icon is not displayed, the MCU's SEG1 pin remains in a high-impedance input state. In this case, the voltage at the SEG1 pin of the LCD screen = VSEG = 1 / 3 VDD, and the voltage difference between COM1 and SEG1 on the LCD screen is 1 / 3 VDD, so no display occurs. If the "C" icon corresponding to COM1 and SEG2 on the LCD screen is to be displayed, the MCU's SEG2 pin outputs a low level (VDD), and the voltage difference between COM1 and SEG2 on the LCD screen is VDD, thus the "C" icon is displayed. If the C icon is not needed, the MCU's SEG2 pin is set to a high-impedance input state. In this case, the voltage at the SEG2 pin of the LCD screen is VSEG = 1 / 3 VDD, and the voltage difference between the COM1 and SEG2 pins is 1 / 3 VDD, so no display is possible. Since the MCU's COM2 pin remains in a high-impedance input state, the COM2 pin voltage at the LCD screen is VCOM = 2 / 3 VDD. Whether the LCD screen needs the A or C icon to be displayed (making the MCU's SEG1 or SEG2 pins output a high level VDD), or it doesn't need to display the A or C icon and the MCU's SEG1 or SEG2 pins are set to a high-impedance input state (in this case, the SEG pin voltage = VSEG = 1 / 3 VDD), the voltage difference between the SEG1 and COM2 pins, and between the SEG2 and COM2 pins, is only 1 / 3 VDD. Therefore, during the COM1 scan and low-level 0V output period, the B and D icons corresponding to COM2 do not need to be displayed.

[0052] At time T3, the MCU's COM1 pin is not scanned, while the COM2 pin is scanned. COM1 is set to a high-impedance input state. The MCU's first I / O pin IO1 outputs a low level (0V), and the MCU's second I / O pin IO2 outputs a high level (VDD). VCOM = 1 / 3 VDD, VSEG = 2 / 3 VDD. When the MCU's COM2 pin outputs a high level (VDD), if the B icon corresponding to COM2 and SEG1 on the LCD screen is to be displayed, the MCU's SEG1 pin outputs a low level (0V), making the voltage difference between COM2 and SEG1 on the LCD screen VDD. If the B icon is not to be displayed, the MCU's SEG2 pin is set to a high-impedance input state. In this case, the voltage at the SEG1 pin of the LCD screen = VSEG = 2 / 3 VDD, and the voltage difference between COM2 and SEG1 on the LCD screen is 1 / 3 VDD, so no display is possible. If the D icon corresponding to COM2 and SEG2 on the LCD screen is to be displayed, the MCU's SEG2 pin outputs a low level (0V), making the voltage difference between COM2 and SEG2 on the LCD screen VDD. If the D icon is not needed, the MCU's SEG2 pin is set to a high-impedance input state. At this time, the voltage at the SEG2 pin of the LCD screen is VSEG = 2 / 3 VDD, and the voltage difference between COM2 and SEG2 is 1 / 3 VDD, so it cannot be displayed. Since the MCU's COM1 pin is set to a high-impedance input state, the voltage at the COM1 pin of the LCD screen is VCOM = 1 / 3 VDD. Whether the LCD screen needs the B or D icon to be displayed (making the MCU's SEG1 or SEG2 output a low level of 0V), or it doesn't need to display the B or D icon and the MCU's SEG1 or SEG2 pin is set to a high-impedance input state (at this time, the SEG pin voltage = VSEG = 2 / 3 VDD), the voltage difference between the SEG1 pin and the COM1 pin, and between the SEG2 pin and the COM1 pin, is only 1 / 3 VDD. Therefore, during the COM2 scan and high-level VDD output period, the A and C icons corresponding to COM1 do not need to be displayed.

[0053] At time T4, the MCU's COM2 output changes to a low level (0V), COM1 is not scanned, and COM1 remains in a high-impedance input state. The MCU's first I / O pin (IO1) switches to a high level (VDD), and the MCU's second I / O pin (IO2) switches to a low level (0V). VCOM = 2 / 3VDD, VSEG = 1 / 3VDD. To keep the B icon corresponding to COM2 and SEG1 on the LCD screen displayed, the MCU's SEG1 pin switches to a high level (VDD), and the voltage difference between COM2 and SEG1 on the LCD screen remains VDD. If the B icon is not to be displayed, the MCU's SEG1 pin remains in a high-impedance input state. In this case, the voltage at the SEG1 pin of the LCD screen = VSEG = 1 / 3VDD, and the voltage difference between COM2 and SEG1 on the LCD screen is 1 / 3VDD, so no display occurs. If the D icon corresponding to COM2 and SEG2 on the LCD screen is to be displayed, the MCU's SEG2 pin outputs a low level (VDD), making the voltage difference between COM2 and SEG2 on the LCD screen VDD. If the D icon is not needed, the MCU's SEG2 pin is set to a high-impedance input state. In this case, the voltage at the SEG2 pin of the LCD screen is VSEG = 1 / 3 VDD, and the voltage difference between COM2 and SEG2 is 1 / 3 VDD, so no display is possible. Since the MCU's COM1 pin remains in a high-impedance input state, the voltage at the COM1 pin of the LCD screen is VCOM = 2 / 3 VDD. Whether the LCD screen needs the B or D icon to be displayed (making the MCU's SEG1 or SEG2 pins output a high level VDD), or it doesn't need to display the B or D icon and the MCU's SEG1 or SEG2 pins are set to a high-impedance input state (in this case, the SEG pin voltage = VSEG = 1 / 3 VDD), the voltage difference between the SEG1 pin and the COM1 pin, and between the SEG2 pin and the COM1 pin, is only 1 / 3 VDD. Therefore, during the COM2 scan and low-level 0V output period, the A and C icons corresponding to COM1 do not need to be displayed. As long as the MCU performs a rapid, dynamic, time-division multiplexing scan at a frequency faster than 50Hz, following the cyclical sequence T1-->T2-->T3-->T4-->T1, the residual effect of human vision can be used to string together the LCD screen display content scanned by COM1 and COM2 at each moment of T1, T2, T3, and T4 into a complete LCD screen display in the human eye, thus completing the display driving of the LCD screen.

[0054] It should be understood that the above explanation only refers to the time-sharing scanning of COM1 and COM2 as an example. The driver scanning principle for COM3, COM4 or more COM terminals is the same as the above process, and so on.

[0055] This application also relates to a display driver module, including the display driver circuit of the above embodiments.

[0056] The display driver module can be a standalone module or integrated into the LCD screen as an internal module component.

[0057] This application also relates to an electronic device, including the display driver module of the above embodiments.

[0058] Electronic devices can be any electronic device with an LCD screen, such as terminals or home appliances.

[0059] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A display driving circuit for driving a liquid crystal screen with a one-third bias ratio, characterized in that, include: The voltage divider circuit includes three resistors of equal resistance connected in series: a first resistor, a second resistor, and a third resistor. The MCU has a first I / O terminal, a second I / O terminal, multiple COM terminals, and multiple SEG terminals. A first resistor is connected to the first I / O terminal, and a third resistor is connected to the second I / O terminal. The common terminal VCOM of the first and second resistors is connected to the multiple COM terminals through a fourth resistor, and the common terminal VSEG of the second and third resistors is connected to the multiple SEG terminals through a fifth resistor. The multiple COM terminals are used to connect to the corresponding COM pins of the LCD screen, and the multiple SEG terminals are used to connect to the corresponding SEG pins of the LCD screen. The voltage difference between the first I / O terminal and the second I / O terminal is VDD. The MCU switches the high / low level output of the first IO terminal and the second IO terminal to apply alternating positive and negative levels between the SEG terminal and the COM terminal, and drives multiple COM terminals to scan sequentially through time-division scanning. This makes the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is in display mode ±VDD, and the voltage difference between the SEG pin and the corresponding COM pin when the LCD screen is not in display mode ±1 / 3VDD, so as to realize the display driving of the LCD screen. The resistance values ​​of the fourth and fifth resistors are both Ra, and the resistance values ​​of the first, second, and third resistors are all Rb. The resistance values ​​of the first, second, third, fourth, and fifth resistors satisfy the following formula: 。 2. The display driving circuit according to claim 1, characterized in that, The number of COM terminals is greater than or equal to four.

3. The display driving circuit according to claim 1, characterized in that, The number of SEG terminals is greater than or equal to four.

4. A display driver module, characterized in that, Includes the display driving circuit as described in any one of claims 1 to 3.

5. An electronic device, characterized in that, Includes the display driver module as described in claim 4.

Images