METHOD AND DEVICE FOR DECREASING LEAKAGE CURRENT OF IN-CELL TOUCH LIQUID CRYSTAL PANEL

Abstract

The disclosure provides a method and a device for decreasing a leakage current of an in-cell touch liquid crystal panel. The method includes: outputting a signal after adjusting a voltage by the data line during a time period of scanning a touch signal according to a voltage on the data line connected to the pixel and a signal inputted to a common electrode of the pixel for scanning the touch signal, so as to decrease a drain source voltage of a thin film transistor in the pixel. According the method and the device, it is capable of decreasing the leakage current of the in-cell touch liquid crystal panel effectively.

Claims

1. A method for decreasing a leakage current of an in-cell touch liquid crystal panel, wherein the panel comprises a pixel array and a scan line and a data line connected to each pixel in the pixel array, the method comprising: outputting a signal after adjusting a voltage by the data line during a time period of scanning a touch signal according to a voltage on the data line connected to the pixel and a signal inputted to a common electrode of the pixel for scanning the touch signal, so as to decrease a drain source voltage of a thin film transistor in the pixel.

2. The method according to claim 1, wherein the thin film transistor is a P type transistor, wherein, when the voltage on the data line connected to the pixel is in a positive half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a low level to a high level, outputting a signal after increasing a voltage by the data line during the time period of scanning the touch signal.

3. The method according to claim 2, wherein a voltage region of the signal after increasing the voltage is: [V.sub.data(min)+(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [V.sub.data(max)+(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein, V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

4. The method according to claim 1, wherein thin film transistor is a N type transistor, wherein, when the voltage on the data line connected to the pixel is in a negative half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a high level to a low level, outputting a signal after decreasing a voltage by the data line during the time period of scanning the touch signal.

5. The method according to claim 4, wherein a voltage region of the signal after decreasing the voltage is: [−V.sub.data(min)−(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [−V.sub.data(max)−(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein, V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

6. A device for decreasing a leakage current of an in-cell touch liquid crystal panel, wherein the panel comprises a pixel array and a scan line and a data line connected to each pixel in the pixel array, the device comprising: a voltage control unit, for outputting a signal after adjusting a voltage through the data line during a time period of scanning a touch signal according to a voltage on the data line connected to the pixel and a signal inputted to a common electrode of the pixel for scanning the touch signal, so as to decrease a drain source voltage of a thin film transistor in the pixel.

7. The device according to claim 6, wherein the thin film transistor is a P type transistor, wherein, when the voltage on the data line connected to the pixel is in a positive half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a low level to a high level, the voltage control unit outputs a signal after increasing a voltage by the data line during the time period of scanning the touch signal.

8. The device according to claim 7, wherein a voltage region of the signal after increasing the voltage is: [V.sub.data(min)+(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [V.sub.data(max)+(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein, V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

9. The device according to claim 6, wherein the thin film transistor is a N type transistor, wherein, when the voltage on the data line connected to the pixel is in a negative half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a high level to a low level, the voltage control unit outputs a signal after decreasing a voltage through the data line during the time period of scanning the touch signal.

10. The device according to claim 9, wherein a voltage region of the signal of after decreasing the voltage is: [V.sub.data(min)−(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [−V.sub.data(max)−(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein, V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a schematic view of a pixel array of an in-cell touch liquid crystal panel;

[0022] FIG. 2 is a schematic view of a pixel circuit;

[0023] FIG. 3 is a flowchart of a method for decreasing a leakage current of an in-cell touch liquid crystal panel according to an exemplary embodiment of the disclosure;

[0024] FIG. 4 is a schematic view of the leakage current for a P-type thin film transistor according to an exemplary embodiment of the disclosure;

[0025] FIG. 5 is a correlogram before and after increasing a voltage for the P-type thin film transistor according to an exemplary embodiment of the disclosure;

[0026] FIG. 6 is a schematic view of the leakage current for a N-type thin film transistor according to an exemplary embodiment of the disclosure;

[0027] FIG. 7 is a correlogram before and after decreasing a voltage for the P-type thin film transistor according to an exemplary embodiment of the disclosure;

[0028] FIG. 8 is a diagram of a device for decreasing a leakage current of an in-cell touch liquid crystal panel according to an exemplary embodiment of the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] It will now be detailed with reference to embodiments of the disclosure, and an example of the embodiment is shown in the accompanying drawings, wherein the like reference numeral refers to the same component. The embodiments are described with reference to the drawings as follows, so as to explain the disclosure.

[0030] FIG. 3 is a flowchart of a method for decreasing a leakage current of an in-cell touch liquid crystal panel according to an exemplary embodiment of the disclosure. Here, the in-cell touch liquid crystal panel includes a pixel array and a scan line and a data line connected to each pixel in the pixel array. The method may be achieved by the in-cell liquid crystal panel, and may also be achieved by a computer program, thereby achieving the above method when the program is executed.

[0031] Refer to FIG. 3. In the step S10, outputting a signal after adjusting a voltage by the data line during a time period of scanning a touch signal according to a voltage on the data line connected to the pixel and a signal inputted to a common electrode of the pixel for scanning the touch signal, so as to decrease a drain source voltage of a thin film transistor in the pixel.

[0032] Since the capacitor formed by the pixel electrode and the common electrode accounts a large portion of the whole for the pixel capacitor; therefore, during the time period of scanning the touch signal, the pixel voltage may generate strong coupling effect following the signal inputted to the common electrode for scanning the touch signal and a larger leakage occurs. Thus according to an exemplary embodiment of the disclosure, a drain source voltage is decreased by adjusting a voltage on the data line, thereby generating a lower leakage current.

[0033] As an example, in a case of the thin film transistor in the pixel is a P-type transistor (e.g., PMOS transistor), and when the voltage on the data line connected to the pixel is in a positive half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a low level to a high level, a signal after increasing a voltage is outputted by the data line during the time period of scanning the touch signal.

[0034] Here, the voltage in the positive half period is that a voltage is greater than or equals to 0, and the pulse signal transformed from the low level to the high level is that a pulse signal transformed from a negative voltage or a ground voltage to a positive voltage.

[0035] As an example, a voltage region of the signal after increasing the voltage may be: [V.sub.data(min)+(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [V.sub.data(max)+(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

[0036] FIG. 4 is a schematic view of the leakage current for a P-type thin film transistor according to an exemplary embodiment of the disclosure. Here, the abscissa indicates a gate source voltage (Vgs) of the thin film transistor, the ordinate indicates a drain source current (Ids) of the thin film transistor, L.sub.1 indicates a IV curve when the drain source voltage of the thin film transistor is higher, L.sub.2 indicates the IV curve when the drain source voltage of the thin film transistor is medium, L.sub.3 indicates the IV curve when the drain source voltage of the thin film transistor is lower, a circle indicates a corresponding position when the LCD displays an image (i.e., the signal inputted to the common electrode is a signal for the display), a triangle indicates scanning the touch signal (i.e., the signal inputted to the common electrode is a signal for scanning the touch signal) and a corresponding position when the voltage on the data line is not increased, and a diamond indicates scanning the touch signal and a corresponding position when the voltage on the data line is increased. As shown in FIG. 4, when the signal inputted to the common electrode is the signal for the display (i.e., the position indicated by the circle), the drain source voltage is lower, and thus the leakage current is lower; when the signal inputted to the common electrode is the signal for scanning the touch signal and the voltage on the data is not increased (i.e., the position indicated by the triangle), the drain source is higher, and thus the leakage current is larger. According to the exemplary embodiment of the disclosure, since the voltage on the data line is increased during the period of scanning the touch signal (i.e., the position indicated by the diamond), the drain source voltage is decreased to decrease the leakage current.

[0037] FIG. 5 is a correlogram before and after increasing a voltage for the P-type thin film transistor according to an exemplary embodiment of the disclosure. As shown in FIG. 5, if the voltage on the data line is not increased during the period of scanning the touch signal, since the coupling effect occurs, a significant voltage drop (ΔV (leakage)) is generated to generate a larger leakage current, thereby increasing the power consumption and the frame quality is low. If the voltage on the data line is increased during the period of scanning the touch signal, a lower voltage drop is generated, thereby generating a lower leakage current.

[0038] As another example, in a case of the thin film transistor in the pixel is a N-type transistor (e.g., NMOS transistor), and when the voltage on the data line connected to the pixel is in a negative half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a high level to a low level, outputting a signal after decreasing a voltage by the data line during the time period of scanning the touch signal.

[0039] Here, the voltage in the negative half period is that a voltage is less than 0, and the pulse signal transformed from the high level to the low level is that a pulse signal transformed from a positive voltage or a ground voltage to a negative voltage.

[0040] As an example, a voltage region of the signal after decreasing the voltage is: [−V.sub.data(min)−(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [−V.sub.data(max)−(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein, V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

[0041] FIG. 6 is a schematic view of the leakage current for a N-type thin film transistor according to an exemplary embodiment of the disclosure. Here, the abscissa indicates a gate source voltage (Vgs) of the thin film transistor, the ordinate indicates a drain source current (Ids) of the thin film transistor, L.sub.1 indicates a IV curve when the drain source voltage of the thin film transistor is higher, L.sub.2 indicates the IV curve when the drain source voltage of the thin film transistor is medium, L.sub.3 indicates the IV curve when the drain source voltage of the thin film transistor is lower, a circle indicates a corresponding position when the LCD displays (i.e., the signal inputted to the common electrode is a signal for the display), a triangle indicates scanning the touch signal (i.e., the signal inputted to the common electrode is a signal for scanning the touch signal) and a corresponding position when the voltage on the data line is not decreased, and a diamond indicates scanning the touch signal and a corresponding position when the voltage on the data line is decreased. As shown in FIG. 6, when the signal inputted to the common electrode is the signal for the display (i.e., the position indicated by the circle), the drain source voltage is lower, and thus the leakage current is lower; when the signal inputted to the common electrode is the signal for scanning the touch signal and the voltage on the data is not decreased (i.e., the position indicated by the triangle), the drain source is higher, and thus the leakage current is larger. According to the exemplary embodiment of the disclosure, since the voltage on the data line is decreased during the period of scanning the touch signal (i.e., the position indicated by the diamond), the drain source voltage is decreased to decrease the leakage current.

[0042] FIG. 7 is a correlogram before and after decreasing a voltage for the P-type thin film transistor according to an exemplary embodiment of the disclosure. As shown in FIG. 7, if the voltage on the data line is not decreased during the period of scanning the touch signal, since the coupling effect occurs, a significant voltage drop (ΔV (leakage)) is generated to generate a larger leakage current, thereby increasing the power consumption and the frame quality is low. If the voltage on the data line is decreased during the period of scanning the touch signal, a lower voltage drop is generated, thereby generating a lower leakage current.

[0043] FIG. 8 is a diagram of a device for decreasing a leakage current of an in-cell touch liquid crystal panel according to an exemplary embodiment of the disclosure. Here, the in-cell touch liquid crystal panel includes a pixel array and a scan line and a data line connected to each pixel in the pixel array.

[0044] As shown in FIG. 8, according to an exemplary embodiment of the disclosure, the device for increasing the leakage current of the in-cell liquid crystal panel includes a voltage control unit 10. The unit may be achieved by a common hardware processor, such as a digital signal processor, a field programmable gate arrays, and may also be achieved by a dedicated hardware processor, such as a dedicated chip, other common hardware processor to achieve, but also by dedicated chips, and may further be achieved by a computer program implemented in a software, for example, it is implemented as a module installed in the software of the in-cell liquid crystal panel.

[0045] The voltage control unit 10 is used for outputting a signal after adjusting a voltage through the data line during a time period of scanning a touch signal according to a voltage on the data line connected to the pixel and a signal inputted to a common electrode of the pixel for scanning the touch signal, so as to decrease a drain source voltage of a thin film transistor in the pixel.

[0046] Since a capacitor formed of the pixel electrode and the common electrode accounts a large portion of the whole for the pixel capacitor, therefore, during the time period of scanning the touch signal, the pixel voltage may generate strong coupling effect following the signal inputted to the common electrode for scanning the touch signal and a larger leakage occurs, thus according to an exemplary embodiment of the disclosure, the voltage control unit 10 adjust the voltage on the data line to decrease the drain source voltage, thereby generating a lower leakage current.

[0047] As an example, in a case of the thin film transistor in the pixel is a P-type transistor (e.g., PMOS transistor), and when the voltage on the data line connected to the pixel is in a positive half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a low level to a high level, the voltage control unit 10 outputs a signal after increasing a voltage through the data line during the time period of scanning the touch signal.

[0048] As an example, a voltage region of the signal after increasing the voltage is: [V.sub.data(min)+(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [V.sub.data(max)+(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

[0049] As another example, in a case of the thin film transistor in the pixel is a N-type transistor (e.g., NMOS transistor), and when the voltage on the data line connected to the pixel is in a negative half period and the signal inputted to the common electrode of the pixel for scanning the touch signal is a pulse signal transformed from a high level to a low level, the voltage control unit 10 outputs a signal after decreasing a voltage through the data line during the time period of scanning the touch signal.

[0050] As an example, a voltage region of the signal of after decreasing the voltage is: [−V.sub.data(min)−(Vgh−Vgl)*Cgs/(Clc.sub.min+Cst)] to [−V.sub.data(max)−(Vgh−Vgl)*Cgs/(Clc.sub.max+Cst)], wherein V.sub.data(min) indicates a minimum voltage on the data line, V.sub.data(max) indicates a maximum voltage on the data line, Vgh indicates a maximum voltage on the scan line, Vgl indicates a minimum voltage on the scan line, Cgs indicates a capacitance value of a parasitic capacitor between a gate and a source of the thin film transistor, Cst indicates a capacitance value of a storage capacitor, Clc.sub.min indicates a minimum capacitance value of a liquid crystal capacitor, and Clc.sub.max indicates a maximum capacitance value of the liquid crystal capacitor.

[0051] According to the exemplary embodiment of the disclosure, in the method and the device for decreasing the leakage current of the in-cell touch liquid crystal panel, it is capable of decreasing the drain source voltage of the thin film transistor in the pixel, thereby effectively decreasing the leakage current and increasing the frame quality.

[0052] Although some exemplary embodiments of the disclosure have been shown and described, those skilled in the art should understand that, without departing from the principles and spirit is defined in the scope of the disclosure is defined by the claims and their equivalents of the cases, these embodiment may be modified.