KR20070016684A - Sensing circuit and display apparatus having the same - Google Patents

Abstract

A sensing circuit performing a touch panel function and a display device having the same are provided. The sensing array of the display device is electrically connected to the sensing electrode and the sensing electrode, the first switching element which is operated according to the first switching signal to charge the sensing capacitor, and electrically connected to the sensing electrode. And a second switching element for generating a first current corresponding to the capacitance change and a third switching element for operating in accordance with the second switching signal to generate a sensing signal corresponding to the difference between the second current and the first current. Accordingly, a display device having a touch panel function for generating position information by external pressure may be implemented by a sensing array provided in the display panel.

Description

SENSING CIRCUIT AND DISPLAY APPARATUS HAVING THE SAME

1 is a plan view of a display device according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a display area and a peripheral area of the display panel shown in FIG. 1 in detail.

3 is a cross-sectional view illustrating a portion A shown in FIG. 1.

4 is a diagram illustrating a capacitance change of a sensing capacitor due to external pressure.

FIG. 5 is a diagram illustrating the sensing array and the op amp shown in FIG. 1.

FIG. 6 is a diagram illustrating a timing signal for operating the sensing array shown in FIG. 5.

<Explanation of symbols for the main parts of the drawings>

100: display device 200: array substrate

210: first substrate 220: pixel array

230: sensing array 300: opposing substrate

330: common electrode 400: liquid crystal layer

500: display panel 600: gate driving circuit

700: data driving circuit 800: op amp

The present invention relates to a sensing circuit and a display device having the same, and more particularly, to a sensing circuit performing a touch panel function and a display device having the same.

In general, the touch panel is provided on the uppermost side of the display device so that the instruction content displayed on the screen of the display device can be selected by a human hand or an object. The touch panel detects a position where a hand or an object is in contact with the touch panel, and the display device receives the content indicated at the touched position as an input signal and is driven according to the input signal.

Since a display device having a touch panel does not require a separate input device connected to the display device such as a keyboard and a mouse, its use is increasing.

However, in general, the touch panel is formed separately from the display panel and is provided on the display panel to increase the overall thickness of the display device.

Accordingly, an object of the present invention is to provide a sensing circuit that detects position information provided with an external input signal by changing a thickness of a liquid crystal layer provided in a display panel.

Another object of the present invention is to provide a display device having the sensing circuit.

The present invention for achieving the above object includes a display panel, a sensing array and a control unit. The display panel includes an array substrate, an opposing substrate having a common electrode facing the array substrate and receiving a common voltage, and a liquid crystal layer interposed between the array substrate and the opposing substrate.

The sensing array is provided on an array substrate, the sensing electrode facing the common electrode with the liquid crystal layer interposed therebetween, and electrically connected to the sensing electrode, the sensing electrode being operated according to a first switching signal to perform the sensing. A first switching element for charging a capacitor, electrically connected to the sensing electrode, and operated according to a second switching element and a second switching signal for generating a first current corresponding to a change of the sensing capacitor due to the external pressure; And a third switching element configured to output a second current maintaining a constant level to output a change amount of the first current according to the capacitance change amount, wherein the change amount of the first current is the sensing signal.

The controller generates position information provided with the external pressure according to the sensing signal.

According to such a display device, since only the current change amount corresponding to the capacitance change amount is input to the op amp by the third switching element, the size of the op amp can be reduced and power consumption can be reduced.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a plan view of a display device according to an exemplary embodiment of the present invention. FIG. 2 is a view illustrating a display area and a peripheral area of the display panel shown in FIG. 1 in detail. .

1 to 3, the display device 100 according to the present invention includes a display panel 500 including an array substrate 200, an opposing substrate 300, and a liquid crystal layer 400. In this case, the display panel 500 has a touch panel function.

The array substrate 200 includes a first substrate 210, a pixel array 220, and a sensing array 230. The first substrate 210 is divided into a display area DA displaying an image and a peripheral area PA adjacent to the display area DA.

The pixel array 220 is formed in a matrix form on the first substrate 210 to correspond to the display area DA. The pixel array 220 includes a plurality of gate lines GL1 to GLn, a plurality of data lines DL1 to DLm, and a plurality of pixel thin film transistors TFT (PT) PT.

The plurality of gate lines GL1 to GLn extend in a first direction D1, and the plurality of data lines DL1 to DLm extend in a second direction D2 orthogonal to the first direction D1. Intersect with the gate lines GL1 to GLn. A plurality of pixel areas PA is defined by two adjacent gate lines and data lines among the plurality of gate lines GL1 to GLn and the plurality of data lines DL1 to DLm.

The plurality of pixel TFTs PT are formed on the first substrate 210 corresponding to each pixel area PA. In addition, each of the plurality of pixel TFTs PT may include a gate electrode (not shown) electrically connected to a corresponding gate line, a source electrode (not shown) electrically connected to a corresponding data line, and a drain formed apart from the source electrode. It consists of an electrode (not shown).

In this case, a gate insulating layer 250 is formed on the first substrate 210 on which the gate electrode is formed, and a passivation layer 260 is formed on the first substrate 210 on which the source electrode and the drain electrode are formed. In addition, a pixel electrode (not shown) patterned in a predetermined shape is formed on the passivation layer 260.

The sensing array 230 may include a sensing electrode SE, a first TFT ST1, a second TFT ST2, and a third TFT ST3.

The sensing electrode SE is formed on the first substrate 210 to correspond to the display area DA. The sensing electrode SE is made of the same material in the same process when forming the source electrode and the drain electrode of the pixel TFT PT. In addition, the sensing electrode SE extends in parallel with the plurality of data lines DL1 to DLm.

In the present exemplary embodiment, the sensing electrode SE is formed to be parallel to the plurality of data lines DL1 to DLm, but the sensing electrode SE may be formed to be parallel to the plurality of gate lines GL1 to GLn. have. In this case, the sensing electrode SE is made of the same material in the same process when the gate electrode of the pixel TFT PT is formed. In addition, the sensing electrode SE is formed of the same material in the same process when forming the pixel electrode.

The first to third TFTs ST1, ST2, and ST3 are formed on the first substrate 210 to correspond to the peripheral area PA. The first TFT ST1 is formed in the first area A1 of the peripheral area PA adjacent to the first ends of the plurality of data lines DL1 to DLm. In addition, the second and third TFTs ST2 and ST3 are formed in the second area A2 of the peripheral area PA adjacent to the second ends of the plurality of data lines DL1 to DLm.

In addition, the sensing array 230 may include a first power supply voltage line VL1, a second power supply voltage line VL2, a third power supply voltage line VL3, a first switching line SL1, and a second switching line SL2. And an output line OL. In this case, the first power supply voltage line VL1 provides the first power supply voltage Vsensor to the first TFT ST1, and the second power supply voltage line VL2 supplies the second power supply voltage to the second TFT ST2. VDD), and the third power supply voltage line VL3 provides a third power supply voltage VSS to the third TFT ST3. The first switching line SL1 provides the first switching signal S1 to the first TFT ST1, and the second switching line SL2 supplies the second switching signal S2 to the third TFT ST3. to provide. In addition, the output line OL outputs a sensing signal according to an external pressure applied to the display panel 500 to the op amp 800 (see FIG. 5).

The gate electrode of the first TFT ST1 is connected to the first switching line SL1, the drain electrode is connected to the first power voltage line VL1, and the source electrode is connected to the sensing electrode SE. The gate electrode of the second TFT ST2 is connected to the sensing electrode SE, and the drain electrode is connected to the second power voltage line VL2. The gate electrode of the third TFT ST3 is connected to the second switching line SL2, and the source electrode is connected to the third power voltage line VL3. The source electrode of the second TFT ST2 and the drain electrode of the third TFT ST are connected to each other and connected to the output line OL.

The opposing substrate 300 includes the second substrate 310, the color filter layer 320, and the common electrode 330 to face the array substrate 200. The color filter layer 320 is formed on the second substrate 310 and is formed of a plurality of color pixels (not shown). The common electrode 330 is made of a transparent conductive material and formed on the color filter layer 320.

In addition, the counter substrate 300 is formed in a matrix form between the color pixels of the color filter layer 320 to correspond to the display area DA of the array substrate 200 to block light leakage between the color pixels. The display device further includes a second light blocking pattern (not shown) formed to correspond to the peripheral area PA of the array substrate 200 to surround the first light blocking pattern (not shown) and the color filter layer 320. Therefore, the first to third TFTs ST1, ST2, and ST3 of the sensing array 230 are formed to correspond to the second light blocking pattern.

The liquid crystal layer 400 is interposed between the array substrate 200 and the counter substrate 300. Therefore, the common electrode 330 faces the pixel electrode with the liquid crystal layer 400 interposed therebetween. In addition, the common electrode 330 faces the sensing electrode SE with the liquid crystal layer 400 therebetween.

Thus, the liquid crystal capacitor Clc is defined by the common electrode 330, the liquid crystal layer 400, and the pixel electrode. In addition, the sensing capacitor Cs is defined by the common electrode 330, the liquid crystal layer 400, and the sensing electrode SE. In addition, various parasitic capacitors are formed. As shown in FIG. 3, the parasitic capacitor Cp is defined by the sensing electrode SE, the gate insulating layer 250, and the n-th gate line GLn. In this case, the sensing capacitor Cs and the parasitic capacitor Cp have a shape connected to each other through the first node N1.

The capacitance of the sensing capacitor Cs is changed by a pressure provided from the outside.

4 is a diagram illustrating a capacitance change of a sensing capacitor due to external pressure.

As shown in FIG. 4, when an external pressure by a predetermined user is provided to the display panel 100, the capacitance of the sensing capacitor Cs is changed. That is, the capacitance increases as the distance between the upper electrode and the lower electrode of the sensing capacitor Cs decreases due to the external pressure.

Where C is the capacitance, ε is the permittivity, A is the electrode area, and d is the electrode spacing.

As in Equation 1, it can be seen that the capacitance increases as the electrode spacing decreases.

Therefore, as the external pressure is provided, the capacitance of the sensing capacitor Cs increases as the distance between the common electrode 330 which is the upper electrode of the sensing capacitor Cs and the sensing electrode SE which is the lower electrode decreases.

The sensing array 230 detects position information of an external pressure applied to the display panel 100 in response to a change in capacitance of the sensing capacitor Cs.

The display device 100 further includes a gate driving circuit 600 and a data driving circuit 700. The gate driving circuit 600 is electrically connected to the plurality of gate lines GL1 to GLn, and sequentially provides gate signals to the plurality of gate lines GL1 to GLn. The gate driving circuit 600 is formed together on the first substrate 210 when the pixel array 220 is formed through a thin film process.

The data driving circuit 700 is electrically connected to the plurality of data lines DL1 to DLm and provides a data signal to the plurality of data lines DL1 to DLm. The data driving circuit 700 is formed embedded in a chip. In this case, the chip in which the data driving circuit 700 is embedded is mounted on the peripheral area PA of the first substrate 210.

FIG. 5 is a diagram illustrating the sensing array and the op amp shown in FIG. 1, and FIG. 6 is a diagram illustrating timing signals for operating the sensing array shown in FIG. 5.

5 and 6, the sensing array 230 outputs a sensing signal corresponding to a capacitance change of the sensing capacitor Cs as the user touches the display panel 500. The operational amplifier 800 is connected to the sensing array 230 to receive a sensing signal, amplify the sensing signal, and output a sensing voltage Vs. At this time, the operational amplifier 800 is configured in the data driving circuit 700.

In detail, before the user touches the display panel 100, the first TFT ST1 is turned on in response to the first switching signal S1 and the first power supply voltage Vsensor. In addition, when the common voltage Vcom is provided to the common electrode 330, the potential of the first node N1 is initialized to the first power supply voltage Vsensor by the sensing capacitor Cs.

Here, the common voltage Vcom is repeatedly provided in a high state and a low state. The first switching signal S1 has the same phase as the common voltage Vcom. In addition, the first switching signal S1 is converted to the low state before a predetermined time t before the common voltage Vcom is changed from the high state to the low state.

As the first switching signal S1 goes low before the common voltage Vcom is changed from the high state to the low state, the first node N1 floats to the first power voltage Vsensor. do.

Thereafter, when the user touches the display panel 500, the thickness of the liquid crystal layer 400 is changed, and as a result, the voltage value of the first node N1 is changed. That is, as the thickness of the liquid crystal layer 400 is pressed, the capacitance of the sensing capacitor Cs is increased. At this time, since the capacitance of the parasitic capacitor Cp does not change, the voltage value of the first node N1 is reduced.

As the voltage value of the first node N1 decreases, the first current i1 flowing in the second TFT ST2 decreases. At this time, the second TFT ST2 is provided with a second power supply voltage VDD. Meanwhile, the third TFT ST3 is turned on in response to the second switching signal S2 and the third power supply voltage VSS. The second switching signal S2 has an inverted phase with respect to the first switching signal S1. That is, the second switching signal S2 maintains a low state when the first switching signal S1 is high and maintains a high state when the first switching signal S1 is low. In addition, the first to third power supply voltages Vsensor, VDD, and VSS have a DC voltage level.

Here, as the third TFT ST3 is turned on, the second current i2 flowing in the third TFT ST3 always maintains a constant level. Therefore, the third current i3 corresponding to the change amount of the first current i1 according to the change amount of the capacitance is input to the operational amplifier 800. Specifically, the third current i3 input to the operational amplifier 800 may be obtained by the difference between the first current i1 and the second current i2. At this time, since the second current i2 flowing through the third TFT ST3 is always maintained at a constant level, and the first current i1 varies according to the change in capacitance, the third current input to the operational amplifier 800. i3 has a current value corresponding to the variable amount of the first current i1.

Therefore, the operational amplifier 800 receives the third current i3 and outputs the sensing voltage Vs according to the amplification of the third current i3.

The sensing voltage Vs output from the operational amplifier 800 is provided to a controller (not shown) in the data driving circuit 700. In this case, the operational amplifier 800 outputs the sensing voltage Vs by the readout signal provided from the controller. The readout signal has the same phase as the second switching signal S2. Therefore, the sensing voltage Vs is output to the controller when the readout signal is high.

Subsequently, the controller determines whether the display panel 500 has been touched by the user by comparing the sensing voltage with the initial voltage, and generates information on the touched position. In addition, the controller provides the first and second switching signals S1 and S2 and the first to third power supply voltages Vsensor, VDD, and VSS to the sensing array 230.

Since the variable amount of the first current i1 according to the change in capacitance is input to the op amp 800 by the third TFT ST3, the size of the op amp 800 can be reduced. For this reason, the power consumption by the operational amplifier 800 can be reduced.

Although the liquid crystal display device has been described above as an example, the present invention can be applied to other display devices. For example, the present invention can be implemented when the upper substrate and the lower substrate, one electrode is formed on one substrate, and a predetermined insulating layer is formed between the two substrates.

As described above, the present invention includes a sensing array consisting of sensing electrodes and first to third TFTs. In this case, a sensing capacitor is formed by the common electrode, the liquid crystal layer, and the sensing electrode. The present invention further includes an op amp which amplifies the current value detected by the sensing array and outputs it to the data driving circuit. Here, only the current change amount corresponding to the capacitance change amount of the sensing capacitor is input to the op amp by the third TFT.

Therefore, the present invention accurately detects the positional information provided by the external input signal by detecting the amount of change in current caused by the capacitance change of the sensing capacitor according to the change in thickness of the liquid crystal layer due to the external pressure by the sensing array and generating the positional information provided with the external pressure. Can be detected. Thus, a display device having a touch panel function can be implemented.

In addition, in the present invention, since only the current change amount corresponding to the capacitance change amount of the sensing capacitor is input into the operational amplifier, the size of the operational amplifier can be reduced. As a result, power consumption of the display device can be reduced.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (16)

Sensing an external pressure applied to a first substrate, a second substrate having a predetermined electrode facing the first substrate and receiving a predetermined voltage, and a panel having an insulating layer interposed between the first substrate and the second substrate In the sensing circuit, A sensing electrode provided on the first substrate to form a sensing capacitor facing the predetermined electrode with the insulating layer interposed therebetween; A first switching element electrically connected to the sensing electrode and operated according to a first switching signal to charge the sensing capacitor; A second switching element electrically connected to the sensing electrode and generating a first current corresponding to a change of the sensing capacitor due to the external pressure; And And a third switching element configured to output a second current operated according to a second switching signal to maintain a constant level, and output a change amount of the first current according to the change amount of the capacitance. The sensing circuit of claim 1, wherein the first switching signal and the second switching signal have inverted phases. The method of claim 1, wherein the sensing array A first power supply voltage line providing a first power supply voltage to the first switching device; A first switching line providing the first switching signal to the first switching element; A second power supply voltage line providing a second power supply voltage to the second switching device; A third power supply voltage line providing a third power supply voltage to the third switching device; And And a second switching line providing the second switching signal to the third switching device. The method of claim 3, wherein the first switching device A first electrode provided with the first power supply voltage; A second electrode provided with the first switching signal; And And a third electrode electrically connected to the sensing electrode. The method of claim 3, wherein the second switching device A first electrode electrically connected to the sensing electrode; A second electrode provided with the second power supply voltage; And And a third electrode connected to the third switching element. The method of claim 3, wherein the third switching device A first electrode provided with the second switching signal; A second electrode provided with the third power supply voltage; And And a third electrode connected to the second switching element. The sensing circuit of claim 1, further comprising an op amp that amplifies the sensing signal. A display panel comprising an array substrate, an opposing substrate having a common electrode facing the array substrate and receiving a common voltage, and a liquid crystal layer interposed between the array substrate and the opposing substrate; A sensing array provided in the display panel and outputting a sensing signal according to a change in thickness of the liquid crystal layer due to external pressure; And And a controller configured to generate position information provided with the external pressure according to the sensing signal. The sensing array A sensing electrode provided on the array substrate to form a sensing capacitor facing the common electrode with the liquid crystal layer interposed therebetween; A first switching element electrically connected to the sensing electrode and operated according to a first switching signal to charge the sensing capacitor; A second switching element electrically connected to the sensing electrode and generating a first current corresponding to a change of the sensing capacitor due to the external pressure; And A third switching element configured to output a second current operated according to a second switching signal to maintain a constant level, and output a change amount of the first current according to the capacitance change amount, And the change amount of the first current is the sensing signal. The display device of claim 8, wherein the first switching signal and the second switching signal have inverted phases. The method of claim 8, wherein the array substrate is A substrate divided into a display area and a peripheral area adjacent to the display area; And A pixel array provided on the substrate corresponding to the display area; The sensing electrode is formed in the display area, And the first to third switching elements are formed in the peripheral area. The method of claim 10, wherein the pixel array Gate lines; A data line crossing the gate line insulated from the gate line; A pixel switching element electrically connected to the gate line and the data line; And And a pixel electrode electrically connected to the pixel switching element. The display device of claim 11, wherein the sensing electrode is formed of the same material as one of the gate line and the data line and is provided on the same layer. 12. The method of claim 11, wherein the sensing electrode extends in parallel with the data line, the first switching element is provided in the first region of the peripheral region adjacent to the first end of the data line, the second and And a third switching element is provided in the second region of the peripheral region adjacent to the second end of the data line. The display device of claim 11, wherein the sensing electrode is formed of the same material as the pixel electrode and disposed on the same layer. The method of claim 8, wherein the sensing array A first power supply voltage line providing a first power supply voltage to the first switching device; A first switching line providing the first switching signal to the first switching element; A second power supply voltage line providing a second power supply voltage to the second switching device; A third power supply voltage line providing a third power supply voltage to the third switching device; And And a second switching line providing the second switching signal to the third switching element. The display device of claim 8, further comprising an op amp that amplifies the sensing signal to generate a sensing voltage, and outputs the generated sensing voltage to the controller.

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