TWI590138B - In-cell touch screen and a method of driving the same - Google Patents

Description

In-cell touch screen and driving method thereof

The present invention relates to a touch screen, and more particularly to an in-cell touch screen.

The touch screen is an output/input device that combines touch technology and display technology to allow users to interact directly with display objects. A capacitive touch panel is a common touch panel that utilizes a capacitive coupling effect to detect a touch position. When the finger touches the surface of the touch panel, the capacitance of the corresponding position changes, and the touch position is detected.

In order to make a thinner touch screen, the built-in technology is used to make the capacitor inside the display, thus omitting some levels. However, the traditional in-cell touch screen has considerable stray capacitance, which causes a large load and thus affects the sensitivity of the touch screen. Therefore, there is a need to propose a novel mechanism for driving an in-cell touch screen to enhance sensitivity.

In view of the above, one of the objects of the embodiments of the present invention is to provide a driving method of an in-cell touch screen such that stray capacitance does not affect the sensing result.

According to an embodiment of the invention, the common voltage layer of the touch screen is divided into a plurality of common voltage electrodes, and is used as a sensing point in the touch sensing mode. The complex source lines below the current common voltage electrode are equally divided into n groups, where n is an integer greater than one. _A current voltage V _{A is} applied to the current common voltage electrode during the conversion phase of each sensing period. For each group of source lines, a second voltage V _{B is} applied to the conversion period for a continuous n sensing periods except for one sensing period. For each sense period, for all group source lines, in addition to a group of source lines, a second voltage V _{B is} applied during the conversion period. Wherein the second voltage V _{B is} approximately equal to (n/(n-1))*V _A .

The first figure shows a perspective view of a self-capacitance in-cell touch screen 100 in accordance with an embodiment of the present invention. The self-capacitance in-cell touch screen (hereinafter referred to as the touch screen) 100 mainly includes a gate (G) line 11, a source (S) line 13, and a common voltage (VCOM) layer 15, which are isolated from each other from bottom to top. For the sake of brevity, some elements of touch screen 100 are not shown in the drawings. For example, a liquid crystal layer may be disposed over the common voltage layer 15.

The gate lines 11 are arranged laterally or columnwise, and the source lines 13 are arranged longitudinally or in a row direction. The common voltage layer 15 is divided into a plurality of common voltage electrodes 151, as exemplified in the second figure, as a sensing point (or receiving (RX) electrode) in the touch sensing mode; and in the display mode, connected to a total Voltage (eg DC voltage).

For the miniaturized touch screen 100, the common voltage electrode 151, the source line 13 and the gate line 11 are very close to each other, and thus the touch screen 100 has stray capacitance. The third diagram shows a circuit diagram of the equivalent capacitance of the common voltage electrode 151, the source line 13 and the gate line 11. VCOM1, VCOM2, and VCOM3 represent three adjacent common voltage electrodes 151. C _C1 and C _C2 represent equivalent capacitances between the common voltage electrodes 151. C _S1 , C _S2 and C _S3 represent equivalent capacitances between the common voltage electrodes 151 (ie, VCOM1, VCOM2, and VCOM3) and the source line 13 located below. C _G1 , C _G2 and C _G3 represent the equivalent capacitance between the common voltage electrode 151 (ie, VCOM1, VCOM2, and VCOM3) and the gate line 11 located below. Each sense point (or common voltage electrode 151) has a total capacitance value (C _CX + C _SX + C _GX ) (where X is 1, 2 or 3), and the resulting load affects the touch screen 100 Sensitivity.

The fourth figure shows an operation timing chart of the touch screen 100. Each sensing period includes a conversion phase 41 and a pre-charge phase 42. In a typical operation, in the conversion phase 41, (the common voltage unit 22 of the second figure) applies a (positive) voltage V _A to the common voltage electrode 151; in the precharge phase 42, no voltage (or ground) is applied. . The source line 13 located below is applied with a fixed voltage V _S and the gate line 11 located below is applied with a fixed voltage V _G throughout the sensing period. Let C _S denote the equivalent capacitance between the common voltage electrode 151 and the source line 13 located below, and C _G denote the equivalent capacitance between the common voltage electrode 151 and the gate line 11 located below, Q _S /Q _G Indicates the charge provided by the source line 13/gate line 11 for the common voltage electrode 151 during the conversion phase 41, and Q _S '/Q _G ' indicates the source line 13 / gate line 11 at the precharge stage 42 for the common voltage The charge provided by the electrode 151: in the conversion phase 41 (e.g., t ₀ to t ₁ ) Q _S = (V _A - V _S ) * C _S Q _G = (V _A - V _G ) * C _G in the precharge phase 42 (eg t ₁ to t ₂ ) Q _S '=(0-V _S )*C _S Q _G '=(0-V _G )*C _G in the sensing period (eg t ₀ to t ₂ ) ΔQ _S =Q _S -Q _S '=V _A *C _S ΔQ _G =Q _G -Q _G '=V _A *C _G

During the sensing period, since the source line 13 and the gate line 11 respectively supply electric charges to the common voltage electrode 151, the touch sensing result is affected. In order to reduce the influence of stray capacitance on the touch sensing result, the following embodiments are proposed.

Figure 5A is a circuit diagram showing the equivalent capacitance between the common voltage electrode 151 (e.g., VCOM1) and the source line 13 of the first embodiment of the present invention. FIG. 5B shows an operation timing chart of the touch screen 100 of FIG.

In the present embodiment, a plurality of source lines 13 are provided below the common voltage electrode 151 (for example, VCOM1), and are equally divided into two groups: a first group source line S_A and a second group source line S_B. The first equivalent capacitance between the common voltage electrode 151 and the first group source line S_A is C _{S_A} , and the second equivalent capacitance between the common voltage electrode 151 and the second group source line S_B is C _{S_B} . The value of the first equivalent capacitor C _{S_A} is approximately half of the (original) equivalent capacitance C _S , and the value of the second equivalent capacitor C _{S_B} is approximately half of the (original) equivalent capacitance C _S , that is, C _{S_A} =C _{S_B} =(1/2)*C _S .

As shown in FIG. 5B, in the conversion phase 41, the common voltage electrode 151 is applied with the first voltage V _A ; in the pre-charging phase 42, no voltage (or ground) is applied. In the conversion phase 41 of the even-numbered sensing periods, the first group source line S_A is applied with the second voltage V _B ; in other stages, no voltage (or ground) is applied. The second group of source lines S_B is applied with a second voltage V _B during the conversion phase 41 of the odd-numbered sensing periods; at other stages, no voltage (or ground) is applied.

Let Q _{S_A} denote the charge provided by the first group source line S_A for the common voltage electrode 151, and Q _{S_B} denote the charge provided by the second group source line S_B for the common voltage electrode 151: during the even number of sensing periods Conversion phase 41 (eg, t ₀ to t ₁ ) Q _{S_A} = (V _A - V _B ) * C _{S_A} Q _{S_B} = (V _{A -} 0) * C _{S_B} in the precharge phase 42 of the even number of sensing cycles (eg t ₁ to t ₂ ) Q _S _ _A =(0-0)*C _{S_A} Q _{S_B} =(0-0)*C _{S_B} for the entire even number of sensing periods (eg t ₀ to t ₂ ) ΔQ _{S_A} =( V _A -V _B )*C _{S_A} ΔQ _{S_B} =V _A *C _{S_B} ΔQ _{S_A} +ΔQ _{S_B} =(2V _A -V _B )*0.5*C _S

If the second voltage V _B is twice the first voltage V _A (that is, V _B =2V _A ), the net charge supplied to the common voltage electrode 151 is zero, so the stray capacitance does not have a touch sensing result. influences. A similar situation occurs for the odd-numbered sensing periods: in the conversion phase 41 of the odd-numbered sensing periods (eg, t ₂ to t ₃ ) Q _{S_A} =(V _A -0)*C _{S_A} Q _{S_B} =(V _A -V _B )*C _{S_B} in the pre-charging phase 42 of the odd-numbered sensing periods (eg t ₃ to t ₄ ) Q _S _ _A =(0-0)*C _{S_A} Q _{S_B} =(0-0)*C _{S_B} The entire odd-numbered sensing periods (eg, t ₂ to t ₄ ) ΔQ _{S_A} =(V _A -V _B )*C _{S_A} ΔQ _{S_B} =V _A *C _{S_B} ΔQ _{S_A} +ΔQ _{S_B} =(2V _A -V _B )* 0.5*C _S

Similar to the even-numbered sensing periods, if the second voltage V _B is twice the first voltage V _A (ie, V _B =2V _A ) among the odd-numbered sensing periods, it is supplied to the common voltage electrode. The net charge of 151 is zero, so the stray capacitance has no effect on the touch sensing results.

Figure 6A is a circuit diagram showing the equivalent capacitance between the common voltage electrode 151 (e.g., VCOM1) and the source line 13 (e.g., S1) of the second embodiment of the present invention. FIG. 6B is a timing chart showing the operation of the touch screen 100 of FIG.

In this embodiment, the plurality of source lines 13 under the common voltage electrode 151 (for example, VCOM1) are equally divided into three groups: a first group source line S_A, a second group source line S_B, and a third group source line. S_C. The first equivalent capacitance between the common voltage electrode 151 and the first group source line S_A is C _{S_A} , and the second equivalent capacitance between the common voltage electrode 151 and the second group source line S_B is C _{S_B} , common voltage The third equivalent capacitance between the electrode 151 and the third group source line S_C is C _{S_C} . The value of the first equivalent capacitor C _{S_A} is approximately one-third of the (original) equivalent capacitance C _S , and the value of the second equivalent capacitor C _{S_B} is approximately one-third of the (original) equivalent capacitance C _S . And the value of the third equivalent capacitor C _{S_C} is about one third of the (original) equivalent capacitance C _S , that is, C _{S_A} = C _{S_B} = C _{S_C} = (1/3) * C _S .

As shown in FIG. 6B, in the conversion phase 41, the common voltage electrode 151 is applied with the first voltage V _A ; in the pre-charging phase 42, no voltage (or ground) is applied. For each group of source lines, a second voltage V _{B is} applied to the conversion period 41 in addition to one sensing period for three consecutive sensing periods. For each sense period, a second voltage V _{B is} applied to the conversion period 41 for all group source lines except for a group of source lines.

Let Q _{S_A} denote the charge provided by the first group source line S_A for the common voltage electrode 151, Q _{S_B} denote the charge provided by the second group source line S_B for the common voltage electrode 151, and Q _{S_C} denotes the third group source The electric charge provided by the line S_C for the common voltage electrode 151: at the (3m-2)th (m is a positive integer) sensing period conversion phase 41 (for example, t ₀ to t ₁ ) Q _{S_A} = (V _A - V _B *C _{S_A} Q _{S_B} =(V _A -0)*C _{S_B} Q _{S_C} =(V _A -V _B )*C _{S_C} in the precharge phase 42 of the (3m-2)th sensing period (eg t ₁ to t ₂ ) Q _S _ _A =(0-0)*C _{S_A} Q _{S_B} =(0-0)*C _{S_B} Q _{S_C} =(0-0)*C _{S_C} for the entire (3m-2) sensing period (eg t ₀ to t ₂ ) ΔQ _{S_A} = (V _A - V _B ) * C _{S_A} ΔQ _{S_B} = V _A * C _{S_B} ΔQ _{S_C} = (V _A - V _B ) * C _{S_C} ΔQ _{S_A} + ΔQ _{S_B} + ΔQ _{S_C} =(3V _A -2V _B )*(1/3)*C _S

If the second voltage V _B is one and a half times the first voltage V _A (that is, V _B =1.5V _A ), the net charge supplied to the common voltage electrode 151 is zero, so the stray capacitance is sensed for the touch. The result has no effect. A similar situation occurs in the (3m-1)th sensing period: in the conversion phase 41 of the (3m-1)th sensing period (eg, t ₂ to t ₃ ) Q _{S_A} =(V _A -V _B )*C _{S_A} Q _{S_B} = (V _A - V _B ) * C _{S_B} Q _{S_C} = (V _{A -} 0) * C _{S_C} in the precharge phase 42 of the (3m - 1)th sensing period (eg, t ₃ to t ₄ ) Q _S _ _A =(0-0)*C _{S_A} Q _{S_B} =(0-0)*C _{S_B} Q _{S_C} =(0-0)*C _{S_C} for the entire (3m-1)th sensing period (eg t ₂ to t ₄ ) ΔQ _{S_A} = (V _A - V _B ) * C _{S_A} ΔQ _{S_B} = (V _A - V _B ) * C _{S_B} ΔQ _{S_C} = V _A * C _{S_C} ΔQ _{S_A} + ΔQ _{S_B} + ΔQ _{S_C} = (3V _A -2V _B )*(1/3)*C _S

Similar to the (3m-2)th sensing period, if in the (3m-1)th sensing period, the second voltage V _B is one and a half times the first voltage V _A (ie, V _B = 1.5) V _A ), the net charge supplied to the common voltage electrode 151 is zero, so the stray capacitance has no effect on the touch sensing result. A similar situation occurs in the 3mth sensing period: in the conversion phase 41 of the 3m sensing period (eg, t ₄ to t ₅ ) Q _{S_A} = (V _A -0) * C _{S_A} Q _{S_B} = (V _A -V _B )*C _{S_B} Q _{S_C} =(V _A -V _B )*C _{S_C} in the pre-charging phase 42 of the _3mth sensing period (eg t ₅ to t ₆ ) Q _S _ _A =(0-0)*C _{S_A} Q _{S_B} = (0-0) * C _{S_B} Q _{S_C} = (0-0) * C _{S_C} over the entire 3m sensing period (eg t ₄ to t ₆ ) ΔQ _{S_A} = V _A * C _{S_A} ΔQ _{S_B} = (V _A -V _B )*C _{S_B} ΔQ _{S_C} =(V _A -V _B )*C _{S_C} ΔQ _{S_A} +ΔQ _{S_B} +ΔQ _{S_C} =(3V _A -2V _B )*(1/3)*C _S

Similar to the (3m-1)th sensing period, if the second voltage V _B is one and a half times the first voltage V _A (ie, V _B =1.5V _A ) during the 3m sensing period, Then, the net charge supplied to the common voltage electrode 151 is zero, so the stray capacitance has no effect on the touch sensing result.

In general, the plurality of source lines 13 under the common voltage electrode 151 are equally divided into n groups (n is an integer greater than 1). In the conversion phase 41, the common voltage electrode 151 is applied with a first voltage V _A ; in the pre-charging phase 42, no voltage (or ground) is applied. For each group of source lines, a second voltage V _{B is} applied to the conversion period 41 for a continuous n sensing periods except for one sensing period. For each sense period, a second voltage V _{B is} applied to the conversion period 41 for all group source lines except for a group of source lines. If the second voltage V _{B is} approximately equal to (n/(n-1))*V _A , the net charge supplied to the common voltage electrode 151 is zero, and thus the stray capacitance has no effect on the touch sensing result.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the invention should be included in the following Within the scope of the patent application.

100‧‧‧Self-capacitor in-cell touch screen
11‧‧‧ gate line
13‧‧‧ source line
15‧‧‧Common voltage layer
151‧‧‧Common voltage electrode
22‧‧‧Common voltage unit
41‧‧‧Conversion phase
42‧‧‧Precharge stage
G‧‧‧ gate
S‧‧‧ source
VCOM‧‧‧ common voltage
VCOM1, VCOM2, VCOM3‧‧‧ common voltage electrode
S1, S2, S3‧‧‧ source
G1, G2, G3‧‧‧ gate
C _C1 , C _C2 ‧‧‧ equivalent capacitance
C _S1 , C _S2 , C _S3 ‧‧‧ equivalent capacitance
C _G1 , C _G2 , C _G3 ‧‧‧ equivalent capacitance
V _A ‧‧‧Voltage / First Voltage
V _B ‧‧‧second voltage
V _S ‧‧‧ voltage
V _G ‧‧‧ voltage
S_A‧‧‧The first group of source lines
S_B‧‧‧Second group source line
S_C‧‧‧ third group source line
C _{S_A} ‧‧‧First equivalent capacitance
C _{S_B} ‧‧‧Second equivalent capacitance
C _{S_C} ‧‧‧ third equivalent capacitance

The first figure shows a perspective view of a self-capacitance in-cell touch screen of an embodiment of the present invention. The second figure shows the common voltage layer of the first figure. The third figure shows the circuit diagram of the equivalent capacitance of the common voltage electrode, the source line and the gate line of the first figure. The fourth figure shows the operation timing diagram of the touch screen of the first figure. Figure 5A is a circuit diagram showing the equivalent capacitance between the common voltage electrode and the source line of the first embodiment of the present invention. FIG. 5B shows an operation timing chart of the touch screen of FIG. Figure 6A is a circuit diagram showing the equivalent capacitance between the common voltage electrode and the source line of the second embodiment of the present invention. Figure 6B shows an operational timing diagram of the touch screen of Figure 6A.

VCOM‧‧‧ common voltage

S_A‧‧‧The first group of source lines

S_B‧‧‧Second group source line

C _{S_A} ‧‧‧First equivalent capacitance

C _{S_B} ‧‧‧Second equivalent capacitance

Claims (8)

A driving method of an in-cell touch screen includes: providing a touch screen, wherein the common voltage layer is divided into a plurality of common voltage electrodes, in a touch sensing mode, as a sensing point; and a current common voltage electrode The plurality of source lines are equally divided into n groups, wherein n is an integer greater than one; at the conversion phase of each sensing period, the current common voltage electrode is applied with a first voltage V _A ; and below the current common voltage electrode Each group of source lines is applied with a second voltage V _B such that the net charge provided by the source lines to the current common voltage electrode is zero, so the corresponding stray capacitance of the current common voltage electrode is for touch sensing The result has no effect; for each group of source lines, the second voltage V _{B is} applied to the conversion period except for one sensing period for successive n sensing periods; for each sensing period, for each group source The line, except for a group of source lines, applies the second voltage V _B during the conversion period; wherein the second voltage V _B is equal to (n/(n-1))*V _A . According to the driving method of the in-cell touch screen according to the first aspect of the patent application, no voltage is applied to the current common voltage electrode in the pre-charging phase of each sensing period. The driving method of the in-cell touch screen according to the first aspect of the patent application, wherein the in-cell touch screen comprises a self-capacitance in-cell touch screen. According to the driving method of the in-cell touch screen according to the first aspect of the patent application, in the display mode, the common voltage electrodes are connected to a common voltage. An in-cell touch screen comprising: a plurality of gate lines, a lateral arrangement; a plurality of source lines, a longitudinal setting; and a common voltage layer divided into a plurality of common voltage electrodes for use as a sensing point in the touch sensing mode Connected to a common voltage in the display mode; one of the source lines below the current common voltage electrode is equally divided into n groups, where n is an integer greater than 1; the current common voltage is converted during each sensing period Applying a first voltage V _{A to the} electrode; and applying a second voltage V _B to each of the source lines below the current common voltage electrode such that the net charges provided by the source lines to the current common voltage electrode are zero Therefore, the corresponding stray capacitance of the current common voltage electrode has no influence on the touch sensing result; for each group of source lines, in the continuous n sensing periods, except for one sensing period, the switching period is applied Two voltages V _B ; for each sense period, for all group source lines, except for a group of source lines, the second voltage V _{B is} applied during the conversion period; wherein the second voltage V _B is equal to (n/( N-1)) *V _A . The in-cell touch screen of claim 5, wherein the gate lines, the source lines, and the common voltage layer are sequentially disposed and isolated from each other. The in-cell touch screen of claim 5, wherein the in-cell touch screen comprises a self-capacitance in-cell touch screen. According to the in-cell touch screen described in claim 5, no voltage is applied to the current common voltage electrode during the pre-charging phase of each sensing cycle.