Common voltage driving circuit and display device

Abstract

The invention provides a common voltage driving circuit and a display device. The common voltage driving circuit comprises a sampling circuit and a common voltage generating circuit, and the common voltage generating circuit is connected with the sampling circuit and a driving circuit of the display panel. The sampling circuit is used for collecting drain voltage of the first thin film transistor when the display panel displays a detection picture, and the first thin film transistor is arranged in a display area of the display panel; the common voltage generation circuit is used for detecting the drain electrode voltage, determining a target common voltage based on the drain electrode voltage and writing the target common voltage into the driving circuit, and the target common voltage is the common voltage enabling the display performance of the display panel to meet the preset requirement. According to the technical scheme provided by the invention, the problem that the image display is influenced by the drift of the target common voltage value can be solved.

Description

Technical Field

[0001] This invention relates to the field of display technology, and more particularly to a common voltage driving circuit and display device. Background Technology

[0002] As the thin-film transistor-liquid crystal display (TFT-LCD) industry matures, users are demanding higher quality and performance from display panels, leading to a wider range of applications. The common voltage (Vcom), a key parameter controlling the deflection of liquid crystal molecules, significantly affects the brightness, contrast, and flicker of the displayed image.

[0003] Currently, before the display panel leaves the factory, the common voltage with the lowest flicker percentage is determined through testing and used as the optimal common voltage. This optimal common voltage value is then programmed into the driver chip via a one-time programmable (OTP) site.

[0004] However, under extreme conditions (such as reliability analysis (RA) conditions) and stringent manufacturing processes, the optimal common voltage value may drift, which can affect the display of the screen. Summary of the Invention

[0005] This application provides a common voltage driving circuit and display device to solve the problem of optimal common voltage value drift, which helps to improve the screen display of the display panel.

[0006] In a first aspect, this application provides a common voltage driving circuit for controlling the common voltage of a display panel. The common voltage driving circuit includes: a sampling circuit and a common voltage generating circuit, wherein the common voltage generating circuit is connected to the sampling circuit and the driving circuit of the display panel; the sampling circuit is used to acquire the drain voltage of a first thin-film transistor when the display panel displays a detection image, and to output the drain voltage to the common voltage generating circuit, wherein the first thin-film transistor is disposed in the display area of ​​the display panel; the common voltage generating circuit is used to detect the drain voltage, determine a target common voltage based on the drain voltage, and write the target common voltage into the driving circuit, wherein the target common voltage is a common voltage that makes the display performance of the display panel meet preset requirements.

[0007] In conjunction with the first aspect, in one possible implementation, the value of the target common voltage is the change in the drain voltage of the first thin-film transistor during the switching from the on state to the off state when the display panel displays the detection screen.

[0008] In conjunction with the first aspect, in one possible implementation, the sampling circuit includes a sampling pixel unit, which includes a second thin-film transistor and a capacitor unit. The drain of the second thin-film transistor is connected to one end of the capacitor unit and the common voltage generation circuit, and the other end of the capacitor unit is connected to the common electrode line of the display panel. The sampling circuit is located outside the display area of ​​the display panel and within the sealing glue area of ​​the display panel. The gate of the second thin-film transistor is used to receive a first voltage signal at a first moment, which is used to turn the second thin-film transistor on or off. The source of the second thin-film transistor is used to receive a second voltage signal at the first moment, which is used to drive the sampling pixel unit to display the detection image. The number of sampling pixel units is one or more. When the number of sampling pixel units is multiple, the second thin-film transistors in the sampling pixel units share a common drain.

[0009] In conjunction with the first aspect, in one possible implementation, the gate and source of the second thin-film transistor are connected to the source driver chip of the display panel.

[0010] In conjunction with the first aspect, in one possible implementation, the first moment includes the start time of each sampling cycle of the sampling circuit.

[0011] In conjunction with the first aspect, in one possible implementation, the common voltage generation circuit includes: a dual-threshold voltage comparator and a control unit. The common voltage generation circuit is disposed in the printed circuit board assembly of the display module, and the display panel is included in the display module. A first input terminal of the dual-threshold voltage comparator is connected to the sampling circuit, a second input terminal of the dual-threshold voltage comparator is connected to a first output terminal of the control unit, and an output terminal of the dual-threshold voltage comparator is connected to an input terminal of the control unit. A second output terminal of the control unit is connected to the driving circuit. The dual-threshold voltage comparator is used to transmit the voltage through the first input terminal. The control unit is configured to: input the drain voltage at the first output terminal; input a third voltage signal at the second input terminal; and output a fourth voltage signal at the output terminal based on the drain voltage and the third voltage signal. The control unit is configured to: output the third voltage signal at the first output terminal; determine a high threshold voltage and a low threshold voltage by monitoring the level changes of the fourth voltage signal input at the second output terminal; determine the drain voltage based on the high threshold voltage and the low threshold voltage; determine the target common voltage based on the drain voltage; and output the target common voltage at the second output terminal. The drain voltage is the sum of the high threshold voltage and the low threshold voltage.

[0012] In conjunction with the first aspect, in one possible implementation, the common voltage generation circuit further includes: a first resistor and a second resistor; a first end of the first resistor is connected to the output terminal of the dual-threshold voltage comparator, a second end of the first resistor is connected to the input terminal of the control unit and the first end of the second resistor, and a second end of the second resistor is grounded; the first resistor and the second resistor are used to divide the voltage output by the dual-threshold voltage comparator; the voltage of the second resistor is the voltage input to the input terminal of the control unit.

[0013] In conjunction with the first aspect, in one possible implementation, the common voltage generation circuit further includes: an input isolation circuit connected to the sampling circuit and the first input terminal of the dual-threshold voltage comparator; the input isolation circuit is used to process and output the drain voltage, and to achieve electrical isolation from the sampling circuit.

[0014] In conjunction with the first aspect, in one possible implementation, the input isolation circuit includes: a voltage follower; the input terminal of the voltage follower is connected to the sampling circuit, and the output terminal of the voltage follower is connected to the first input terminal of the dual-threshold voltage comparator.

[0015] In conjunction with the first aspect, in one possible implementation, the driving circuit includes: a power management integrated circuit or a touch and display driving integrated circuit, wherein the input terminal of the driving circuit is connected to the common voltage generation circuit, and the output terminal of the driving circuit is connected to the common electrode line of the display panel; the driving circuit is configured to input the target common voltage through the input terminal and output the target common voltage to the common electrode line through the output terminal.

[0016] In a second aspect, this application provides a display device that includes a common voltage driving circuit as described in the first aspect or any possible implementation of the first aspect.

[0017] This application provides a common voltage driving circuit and a display device. In the technical solution provided by this application, a sampling circuit acquires the drain voltage of the first thin-film transistor (TFT) when a pixel unit in the display area displays a detection image, and outputs it to a common voltage generation circuit. The common voltage generation circuit detects the drain voltage output by the sampling circuit, determines the value of the target common voltage based on the detected drain voltage, and writes the determined target common voltage value into the driving circuit of the display panel, thereby realizing the detection and online programming of the target common voltage. Compared with the prior art, the technical solution provided by this application can realize the updating of the target common voltage, which helps to improve the problem of poor image display effect caused by target common voltage drift. In addition, the technical solution provided by this application can save the process of programming the target common voltage value through a one-time programmable (OTP) station on the display panel production line. Attached Figure Description

[0018] Figure 1 A schematic diagram illustrating a common voltage driving circuit provided in this application; Figure 1a A schematic diagram illustrating the determination of a target common voltage provided in this application; Figure 2a A schematic diagram illustrating the location of a sampling circuit provided in this application; Figure 2b A schematic diagram illustrating the location of another sampling circuit provided in this application; Figure 3 A schematic diagram illustrating a common voltage driving circuit provided in this application; Figure 4 A schematic diagram of the transfer characteristic curve of a dual-threshold voltage comparator provided in this application; Figure 5 The present application provides a voltage signal output by a control unit. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] A pixel unit in a thin-film transistor-liquid crystal display (TFT-LCD) panel includes a TFT and a capacitor unit. The capacitor unit includes a liquid crystal capacitor and a storage capacitor, which are connected in parallel. A TFT includes a source, a gate, and a drain. The source of the TFT is connected to the data line, the gate is connected to the scan line, the drain is connected to one end of the capacitor unit, and the other end of the capacitor unit is connected to a common electrode. The voltage on the common electrode can be called the common voltage (Vcom).

[0021] The pixel electrode receives data voltage from the driving circuit via a TFT, creating a stable electric field between the common voltage and the pixel electrode. The strength of this electric field is determined by the difference between the pixel electrode voltage and the common voltage. Adjusting this difference allows for adjustment of the electric field strength, thereby controlling the deflection angle of the liquid crystal molecules. For example, a stronger electric field increases the deflection angle of the liquid crystal molecules, increasing light transmittance and display brightness; conversely, a weaker electric field decreases the deflection angle, reducing light transmittance and display brightness. The accuracy of the common voltage, serving as a reference voltage, affects the brightness, contrast, and flicker of the displayed image. For instance, when the common voltage is higher than the optimal value, the effective electric field strength at low grayscale levels may be insufficient, leading to excessive brightness in dark states and reduced contrast; conversely, when the common voltage is lower than the optimal value, the electric field strength at high grayscale levels may be excessive, causing excessive deflection of the liquid crystal molecules, resulting in abnormal brightness in bright states or localized flicker.

[0022] Currently, before the display panel leaves the factory, the common voltage with the lowest flicker percentage is determined through testing and used as the optimal common voltage value. This optimal common voltage value is then programmed into the driver chip via a one-time programmable (OTP) site.

[0023] However, when the display panel encounters extreme conditions (such as reliability analysis (RA) conditions) and strict manufacturing processes, the optimal common voltage value will drift. The optimal common voltage value already burned into the driver chip cannot be updated. In this case, the deflection of liquid crystal molecules will still be controlled by the already burned optimal common voltage value, which will result in a poor display effect of the display panel.

[0024] In view of this, this application provides a common voltage driving circuit and a display device. The common voltage driving circuit provided by this application can detect the optimal common voltage value and automatically program the optimal common voltage value online, thereby solving the problem of optimal common voltage value drift. The technical solution provided by this application improves the display effect by adding an optimal common voltage value update function.

[0025] The following is in conjunction with the appendix Figures 1 to 5 This application provides a detailed description of the technical solution provided.

[0026] Figure 1 A schematic diagram illustrating a common voltage driving circuit provided in this application. Figure 1 The common voltage drive circuit shown is used to control the common voltage of the display panel.

[0027] like Figure 1 As shown, the common voltage driving circuit 100 includes a sampling circuit 110 and a common voltage generation circuit 120. The common voltage generation circuit 120 is connected to the sampling circuit 110 and the driving circuit in the display panel.

[0028] The sampling circuit 110 can be used to acquire the drain voltage of the first TFT when the display panel displays the detection screen, and to output the acquired drain voltage to the common voltage generation circuit 120. The first TFT is disposed in the display area (active area, AA) of the display panel, or in other words, the pixel unit corresponding to the first TFT is used to realize the display of the screen. In this application, the detection screen can be understood as a standard screen with a specific pattern, color, and grayscale displayed on the display panel for realizing the detection of the target common voltage. Optionally, the detection screen can be a white screen.

[0029] A common voltage generation circuit 120 is used to detect the drain voltage collected by the sampling circuit 110, determine the target common voltage based on the detected drain voltage, and write the target common voltage into the driving circuit of the display panel, thereby realizing the online programming of the target common voltage value. The target common voltage is the common voltage that makes the display performance of the display panel meet preset requirements. The display performance can be related to at least one of the following: flicker percentage, brightness deviation value, or grayscale linearity deviation. Flicker percentage is used to evaluate the visibility of screen flicker and is an indicator that measures the relative degree of brightness fluctuation over time during the periodic refresh of the display panel. Brightness deviation value is used to evaluate brightness uniformity and is an indicator that measures the degree of deviation between the actual brightness of different areas or different pixels at the same grayscale in the display panel and the target brightness. Grayscale linearity deviation is used to evaluate the accuracy of grayscale performance and is an indicator that measures the degree of deviation between the actual output brightness of the display panel and the linear brightness curve corresponding to the ideal grayscale. The target common voltage can also be called the optimal common voltage or others, and this application does not limit this.

[0030] It should be noted that the display panel displays the detection screen in two parts: when the first TFT is turned on, it receives the detection data voltage output by the source driver chip and transmits the detection data voltage to the pixel electrode. The detection data voltage is used to drive the pixel unit corresponding to the first TFT to display the detection screen; when the first TFT is turned off, the pixel electrode maintains the display of the detection screen based on the detection data voltage. Correspondingly, the drain voltage collected by the sampling circuit includes two parts: the drain voltage when the first TFT is in the on state, and the drain voltage when the first TFT is in the off state. In this application, the target common voltage can be determined based on the change in drain voltage during the transition of the first TFT from the on state to the off state. The change is the difference between the drain voltage after the first TFT state switch and before the state switch.

[0031] In one feasible approach, the change in drain voltage can be determined as the target common voltage.

[0032] Figure 1a This is a schematic diagram illustrating the determination of a target common voltage, as provided in this application. Figure 1aAs shown, when the gate voltage of the first TFT is at gate high voltage (VGH), the first TFT is turned on, and its source receives the detection data voltage Us output by the source driver chip. At this time, the drain voltage Ud of the first TFT is the same as the source voltage Us. When the gate voltage of the first TFT switches to gate low voltage (VGL), the first TFT switches to the off state, and its drain voltage Ud changes from Us to Uref. The change in drain voltage is the difference between Uref and Us. In this implementation, the difference between Uref and Us can be determined as the target common voltage.

[0033] In one feasible approach, the feedthrough voltage can be determined based on the change in drain voltage, and the target common voltage can be further determined based on the feedthrough voltage.

[0034] In this application, the target common voltage is detected and programmed online by adding a common voltage driving circuit. This allows the target common voltage to be updated when its value drifts, thereby improving the display effect of the screen.

[0035] In one possible implementation, the sampling circuit 110 may include a sampling pixel unit, which includes a second TFT and a capacitor unit. The drain of the second TFT is connected to one end of the capacitor unit and the common voltage generation circuit 120, and the other end of the capacitor unit is connected to the common electrode line of the display panel.

[0036] The gate of the second TFT is used to receive a first voltage signal at a first moment. The first voltage signal is used to turn the second TFT on or off. For example, the first voltage signal can be a pulse signal, with a high level of VGH and a low level of VGL.

[0037] The source of the second TFT is used to receive the second voltage signal at the first moment, and the second voltage signal is used to drive the sampling pixel unit to display the detection screen.

[0038] In this application, the number of second sampling pixel units can be one or more. When there are multiple sampling pixel units, the second TFTs in the sampling pixel units are common drains. A common drain can be understood as the drains being short-circuited to each other and electrically connected to the same node.

[0039] In one possible implementation, both the gate and source of the second TFT can be connected to the source driver chip of the display panel. In this implementation, the first voltage signal is output to the gate of the second TFT from an idle general-purpose input / output (GPIO) port in the existing source driver chip of the display panel, thereby reducing the implementation difficulty and cost of the technical solution of this application.

[0040] In one possible implementation, the first moment may include the start time of each sampling cycle of the sampling circuit. The start time of the first sampling cycle may be the power-on time of the display module. The sampling cycle can be set according to actual needs, and this application does not impose any restrictions on it.

[0041] In this application, the sampling circuit 110 can be disposed outside the display area of ​​the display panel and within the seal area of ​​the display panel. By disposing the sampling circuit in the liquid crystal area, the sampling pixel unit can simulate the process of the pixel unit displaying the detection image in the display area, thereby achieving the acquisition of the drain voltage of the first TFT when the pixel unit in the display area displays the detection image without affecting the normal display of the display panel. It should be understood that the drain voltage of the first TFT when the pixel unit in the display area displays the detection image is the same as the drain voltage of the second TFT when the sampling pixel unit displays the detection image. It should be noted that the display panel includes a color filter (CF), a TFT array substrate, and a liquid crystal layer disposed between the CF substrate and the TFT array substrate. The liquid crystal layer includes two parts: the display area and the seal area.

[0042] In one possible implementation, the sampling circuit 110 can be positioned around the display area. The following section discusses... Figure 2a and Figure 2b The location of the sampling circuit in the display panel is explained. Figure 2a This is a schematic diagram illustrating the location of a sampling circuit provided in this application. Figure 2b A schematic diagram illustrating the location of another sampling circuit provided in this application.

[0043] Figure 2a The sampling circuit shown includes eight sampling pixel units, which are located below the display area, and the second TFT in each sampling pixel unit has a common drain. It should be noted that the sampling circuit can also be located above, to the left, or to the right of the display area, depending on actual needs, and is not limited here. It can be seen that the gate and source of the second TFT are connected to the source driver chip, and the drain is connected to the common voltage generation circuit.

[0044] like Figure 2bAs shown, the sampling circuit includes a sampling pixel unit, which is located at the lower right corner of the sealing adhesive area. It should be understood that the sampling pixel unit can also be located at the lower left, upper left, or upper right corner of the sealing adhesive area; the specific location can be determined according to actual needs and is not limited here.

[0045] Figure 3 A schematic diagram illustrating a common voltage driving circuit provided in this application. Figure 3 right Figure 1 Detailed description of the common voltage generation circuit. For example... Figure 3 As shown, the common voltage generation circuit 120 includes a dual-threshold voltage comparator and a control unit. The common voltage generation circuit 120 can be disposed within the printed circuit board assembly (PCBA) of the liquid crystal module (LCM). It should be understood that the display panel is included within the display module.

[0046] The first input terminal of the dual-threshold voltage comparator is connected to the sampling circuit 110. Figure 3 The first input terminal of the dual-threshold voltage comparator is connected to the drain of the second TFT in the sampling circuit 110. The second input terminal of the dual-threshold voltage comparator is connected to the first output terminal of the control unit, the output terminal of the dual-threshold voltage comparator is connected to the input terminal of the control unit, and the second output terminal of the control unit is connected to the driving circuit of the display panel.

[0047] A dual-threshold voltage comparator is used to input the drain voltage from sampling circuit 110 through its first input terminal. This drain voltage can be understood as the reference voltage of the dual-threshold voltage comparator. Figure 3 Ud; the third voltage signal is input through the second input terminal, the third voltage signal is as follows: Figure 3 Ui in the output; and a fourth voltage signal output through the output terminal based on the drain voltage and the third voltage signal, such as Figure 3 Uo in the diagram. It should be noted that resistors R1 and R2 in the dual-threshold voltage comparator are feedback resistors; adjusting the values ​​of R1 and R2 adjusts the dual-threshold values ​​of the comparator. Voltage VCC is the positive power supply terminal, used to determine the high-level voltage output of the dual-threshold voltage comparator; voltage -VCC is the negative power supply terminal, used to determine the low-level voltage output of the dual-threshold voltage comparator. In this application, the third voltage signal is a positive voltage signal; therefore, the dual-threshold voltage comparator operates in the first quadrant of the coordinate system.

[0048] Figure 4This is a schematic diagram of the transfer characteristic curve of a dual-threshold voltage comparator provided in this application. It can be seen that the high-level voltage of the dual-threshold voltage comparator is VCC, and the low-level voltage is -VCC. The high-threshold voltage is Vh, and the low-threshold voltage is Vl.

[0049] The control unit is configured to output a third voltage signal via a first output terminal, determine a high threshold voltage and a low threshold voltage by monitoring the voltage level changes at the input terminals, determine the drain voltage based on the high and low threshold voltages, determine a target common voltage based on the drain voltage, and output the target common voltage via a second output terminal. The drain voltage is the sum of the high and low threshold voltages. The input terminals of the control unit are as follows: Figure 3 H / L IO port in the middle.

[0050] The voltage level changes include switching from high to low and switching from low to high. The rules for determining high and low voltage levels can be set according to actual needs, and this application does not impose any restrictions on this. For example, a voltage greater than or equal to 1.2 volts can be defined as a high level, and a voltage less than 1.2 volts can be defined as a low level.

[0051] In this application, the control unit can record the Ui of the voltage level input at the input terminal changing from high level to low level as Vh, and record the Ui of the voltage level input at the input terminal changing from low level to high level as Vl.

[0052] Optionally, a voltage comparator can be added to the control unit. This voltage comparator is connected to the input terminal so that the control unit can monitor the level changes of the voltage input to the input terminal.

[0053] Optionally, the control unit can be a microcontroller unit (MCU).

[0054] Optionally, a digital-to-analog converter (DAC) can be set in the control unit to achieve the output of a third voltage signal.

[0055] It should be noted that, in combination Figure 3 and Figure 4 As can be seen from the working principle of the dual-threshold voltage comparator, the high-threshold voltage Vh and the low-threshold voltage Vl satisfy the following relationship: ;

[0056] When R1=R2, we can obtain Ud=Vh+Vl based on the above relationship. Therefore, the control unit can determine the drain voltage based on the high threshold voltage and the low threshold voltage, thereby further determining the target common voltage.

[0057] Optionally, the common voltage generation circuit also includes: a first resistor and a second resistor. The first resistor is as follows: Figure 3 The resistor R3 in the middle, the second resistor is as follows Figure 3 The resistor R4 in the middle. For example... Figure 3 As shown, the first end of resistor R3 is connected to the output of the dual-threshold voltage comparator, the second end of resistor R3 is connected to the input of the control unit and the first end of resistor R4, and the second end of resistor R4 is grounded.

[0058] Resistors R3 and R4 are used to divide the voltage output of the dual-threshold voltage comparator. It can be seen that the voltage across resistor R4 is the voltage input to the control unit. The control unit can determine Vh and Vl based on the level change of the voltage across resistor R4.

[0059] Optionally, the common voltage generation circuit also includes an input isolation circuit. The input isolation circuit can be connected to the sampling circuit 110 and the first input terminal of the dual-threshold voltage comparator, such as... Figure 3 As shown.

[0060] The input isolation circuit is used to process and output the drain voltage from the sampling circuit 110, and to achieve electrical isolation from the sampling circuit 110, so as to improve the stability of the entire system.

[0061] In one possible implementation, the input isolation circuit may include: a voltage follower, such as... Figure 3 As shown, the input terminal of the voltage follower is connected to the sampling circuit 110, and the output terminal of the voltage follower is connected to the first input terminal of the dual-threshold voltage comparator.

[0062] The voltage follower can latch the drain voltage from the sampling circuit 110 to improve the stability of the drain voltage and facilitate subsequent processing of the drain voltage. The voltage follower can also achieve electrical isolation from the sampling circuit 110.

[0063] Optionally, the driving circuit may include a power management integrated circuit (PMIC) or a touch and display driver integration (TDDI). It can be seen that the input terminal of the driving circuit is connected to the control unit in the common voltage generation circuit 120, and the output terminal of the driving circuit is connected to the common electrode line of the display panel.

[0064] The drive circuit is used to input the target common voltage from the control unit through the input terminal and output the target common voltage to the common electrode line through the output terminal, so as to adjust the target common voltage.

[0065] The following is about Figure 3 The working principle of the common voltage drive circuit in the circuit is explained.

[0066] At the moment the display module is powered on, the source driver chip can output a first voltage signal to the gate of the second TFT in the sampling circuit and a second voltage signal to the source of the second TFT through the GPIO port, so that the sampling pixel unit can display the detection image.

[0067] To prevent image retention caused by DC bias from affecting the display effect, the display panel can display two frames of detection images. Taking a white image as an example, and the detection data voltage corresponding to the white image being 5 volts, the source driver chip can output a 5-volt voltage to the source of the second TFT in the first frame, and output a (-5)-volt voltage to the source of the second TFT in the second frame.

[0068] When the display panel shows the detection screen, the control unit can output Ui to the dual-threshold voltage comparator. Ui is as follows: Figure 5 The voltage signal in the image, Ui, has a period of 1 frame. For example... Figure 5 As shown, Ui represents a voltage range of 0 to 5 volts during frames 0 to 0.5, and a voltage range of 5 to 0 volts during frames 0.5 to 1. It should be noted that during frames 1 to 2, the source voltage of the second TFT is (-5) volts, and the control unit outputs the Ui signal for the second cycle. At this time, the voltage output by the dual-threshold voltage comparator does not change its level, or in other words, the voltage input to the control unit is always low and does not change its level. Therefore, the control unit can ignore the data in this frame.

[0069] During the two frames mentioned above, the control unit can determine Vh and Vl by monitoring the voltage level changes of resistor R4, thereby determining the drain voltage Ud, and further determining the target common voltage. The target common voltage value can be the change in drain voltage during the transition of the second TFT from the on state to the off state.

[0070] After determining the target common voltage, the control unit can write it into the drive circuit. Since the data stored in the drive circuit is hexadecimal, while the target common voltage determined by the control unit is decimal, the control unit can convert the target common voltage to hexadecimal before writing it into the drive circuit. The drive circuit can then output the written target common voltage to the common voltage line of the display panel to drive the common voltage. Furthermore, after the target common voltage is successfully programmed online, the display panel can display the image normally.

[0071] The technical solution provided in this application simulates the process of a pixel unit displaying a detection image within the display area using a sampling circuit. The drain voltage of the second TFT when the sampled pixel unit displays the detection image is replaced by the drain voltage of the first TFT when the pixel unit displays the detection image within the display area. This allows for the acquisition of the drain voltage of the first TFT when the pixel unit displays the detection image within the display area without affecting the normal display of the display panel. A common voltage generation circuit detects the drain voltage of the second TFT output by the sampling circuit and determines the value of the target common voltage based on the detected change in drain voltage. The determined value of the target common voltage is then written into the driving circuit of the display panel, thus realizing the detection and online programming of the target common voltage. The detection and online programming of the target common voltage can be performed when the display module is powered on, ensuring that the target common voltage is updated every time the display module is powered on. This helps to improve the problem of poor image display caused by target common voltage drift. For example, it can improve problems such as screen flicker, horizontal or vertical lines in the display image, and image sticking (IS) caused by target common voltage drift. The detection and online programming of the target common voltage can also be performed according to a certain cycle, and this application does not impose any restrictions on this. Compared with the prior art, the technical solution provided by this application can realize the updating of the target common voltage, saving the process of programming the target common voltage value via OTP on the display panel production line.

[0072] The present invention also provides a display device including a common voltage driving circuit as shown in the foregoing embodiments.

[0073] In the description of this invention, it should be noted that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limiting this invention.

[0074] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0075] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described above can be combined with each other as long as they do not conflict with each other.

[0076] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A common voltage driving circuit for controlling the common voltage of a display panel, characterized in that, include: A sampling circuit and a common voltage generation circuit, wherein the common voltage generation circuit is connected to the sampling circuit and the driving circuit of the display panel; The sampling circuit is used to collect the drain voltage of the first thin-film transistor when the display panel displays the detection screen, and to output the drain voltage to the common voltage generation circuit. The first thin-film transistor is disposed in the display area of ​​the display panel. The common voltage generation circuit is used to detect the drain voltage, determine the target common voltage based on the drain voltage, and write the target common voltage into the driving circuit. The target common voltage is a common voltage that makes the display performance of the display panel meet the preset requirements.

2. The common voltage driving circuit according to claim 1, characterized in that, The value of the target common voltage is the change in the drain voltage of the first thin-film transistor during the process of switching from the on state to the off state when the display panel displays the detection screen.

3. The common voltage driving circuit according to claim 1, characterized in that, The sampling circuit includes a sampling pixel unit, which includes a second thin-film transistor and a capacitor unit. The drain of the second thin-film transistor is connected to one end of the capacitor unit and the common voltage generation circuit. The other end of the capacitor unit is connected to the common electrode line of the display panel. The sampling circuit is located outside the display area of ​​the display panel and inside the sealing glue area of ​​the display panel. The gate of the second thin-film transistor is used to receive a first voltage signal at a first moment, and the first voltage signal is used to turn the second thin-film transistor on or off. The source of the second thin-film transistor is used to receive a second voltage signal at the first moment, and the second voltage signal is used to drive the sampling pixel unit to display the detection image; The number of sampling pixel units is one or more. When the number of sampling pixel units is multiple, the second thin-film transistor in the sampling pixel unit is a common drain.

4. The common voltage driving circuit according to claim 3, characterized in that, The gate and source of the second thin-film transistor are connected to the source driver chip of the display panel.

5. The common voltage driving circuit according to claim 3 or 4, characterized in that, The first moment includes the start time of each sampling cycle of the sampling circuit.

6. The common voltage driving circuit according to claim 1, characterized in that, The common voltage generation circuit includes a dual-threshold voltage comparator and a control unit. The common voltage generation circuit is disposed in the printed circuit board assembly of the display module, and the display panel is included in the display module. The first input terminal of the dual-threshold voltage comparator is connected to the sampling circuit, the second input terminal of the dual-threshold voltage comparator is connected to the first output terminal of the control unit, the output terminal of the dual-threshold voltage comparator is connected to the input terminal of the control unit, and the second output terminal of the control unit is connected to the drive circuit. The dual-threshold voltage comparator is used to input the drain voltage through a first input terminal, input a third voltage signal through a second input terminal, and output a fourth voltage signal through an output terminal based on the drain voltage and the third voltage signal. The control unit is configured to output the third voltage signal through a first output terminal, determine a high threshold voltage and a low threshold voltage by monitoring the level change state of the fourth voltage signal input through an input terminal, determine the drain voltage based on the high threshold voltage and the low threshold voltage, determine the target common voltage based on the drain voltage, and output the target common voltage through a second output terminal, wherein the drain voltage is the sum of the high threshold voltage and the low threshold voltage.

7. The common voltage driving circuit according to claim 6, characterized in that, The common voltage generation circuit further includes: a first resistor and a second resistor; The first end of the first resistor is connected to the output of the dual-threshold voltage comparator, the second end of the first resistor is connected to the input of the control unit and the first end of the second resistor, and the second end of the second resistor is grounded. The first resistor and the second resistor are used to divide the voltage output by the dual-threshold voltage comparator; The voltage across the second resistor is the voltage input to the input terminal of the control unit.

8. The common voltage driving circuit according to claim 6 or 7, characterized in that, The common voltage generation circuit further includes an input isolation circuit, which is connected to the sampling circuit and the first input terminal of the dual-threshold voltage comparator. The input isolation circuit is used to process and output the drain voltage, and to achieve electrical isolation from the sampling circuit.

9. The common voltage driving circuit according to claim 8, characterized in that, The input isolation circuit includes: a voltage follower; The input terminal of the voltage follower is connected to the sampling circuit, and the output terminal of the voltage follower is connected to the first input terminal of the dual-threshold voltage comparator.

10. A display device, characterized in that, Includes a common voltage drive circuit as described in any one of claims 1 to 9.

Images