KR102248878B1 - Touch sensing system - Google Patents

Abstract

The touch sensing system according to the present invention includes: a touch screen including a plurality of touch sensors and sensor wires connected to the touch sensors; A plurality of sensing units for receiving a touch sensor signal from the touch sensors through a plurality of reception channels and sensing a touch input using the received touch sensor signal; A signal generator for generating charge erasing control signals for controlling output voltages of the sensing units; And a charge eraser formed between the receiving channels and the sensing units, and reducing a variation width of touch sensor signals input to the sensing units in response to the charge erasing control signals.

Description

Touch sensing system {TOUCH SENSING SYSTEM}

The present invention relates to a touch sensing system.

The user interface (UI) allows a person (user) to easily control various electronic devices as desired. Representative examples of such a user interface include a keypad, a keyboard, a mouse, an On Screen Display (OSD), a remote controller having an infrared or radio frequency (RF) communication function. User interface technology continues to develop in the direction of enhancing user sensibility and operational convenience. Recently, user interfaces are evolving into touch UIs, voice recognition UIs, and 3D UIs.

Touch UI is essentially adopted in portable information devices. The touch UI is implemented by forming a touch screen on the screen of a display device. Such a touch screen may be implemented in a capacitive manner. A touch screen having a capacitive touch sensor detects a touch input by sensing a change in capacitance, that is, an amount of change in charge of the touch sensor when a finger or a conductive material contacts the touch sensor.

The capacitive touch sensor may be implemented as a self-capacitance sensor or a mutual capacitance sensor. Each of the electrodes of the self-capacitive sensor may be connected 1:1 with sensor wires formed along one direction. The mutual capacitance sensor may be formed at an intersection of sensor wires Tx and Rx that are orthogonal to each other with a dielectric layer therebetween.

A touch screen having a capacitive sensor is connected to a plurality of sensing units. Each sensing unit senses a change in charge of the touch sensor by receiving a touch sensor signal from the touch screen through a reception channel. Such a sensing unit may be integrated in a touch IC (Integrated Circuit) and connected to sensor wires of the touch screen.

An example of a sensing unit is shown in FIGS. 1 and 2. FIG. 1 shows a sensing unit when the touch screen TSP is implemented as a mutual capacitive sensor Cm, and FIG. 2 shows a sensing unit when the touch screen TSP is implemented as a self-capacitive sensor Cs. .

1 and 2, the sensing unit may include an operational amplifier OP and a sensing capacitor Cf. The inverting input terminal (-) of the operational amplifier (OP) is connected to the touch sensor (Cm or Cs) through the receiving channel, and the non-inverting input terminal (+) of the operational amplifier (OP) is connected to the reference voltage (Vref) terminal. And, the output terminal of the operational amplifier OP may be connected to the inverting input terminal (-) via the sensing capacitor Cf.

In the sensing unit of FIG. 1, the operational amplifier OP functions as an inverting amplifier. The output voltage Vout of the sensing unit can be expressed as in Equation 1.

In Equation 1, the reference voltage Vref is a direct current (DC) level, Vtx represents the driving voltage applied to the mutual capacitance sensor Cm, CM represents the mutual capacitance of the mutual capacitance sensor Cm, and CF is It represents the capacity of the sensing capacitor Cf. The output voltage Vout of FIG. 1 indicating the amount of change in charge of the mutual capacitance sensor Cm has a voltage polarity opposite to that of the driving voltage Vtx.

Meanwhile, in the sensing unit of FIG. 2, the operational amplifier OP functions as a non-inverting amplifier. The output voltage Vout of the sensing unit can be expressed as in Equation 2.

In Equation 2, the reference voltage Vref is an AC level swinging between the high potential level VH and the low potential level VL, ΔVref represents the swing width of the reference voltage Vref, and CS is The self-capacitance sensor Cs represents the self-capacity, and CF denotes the sensing capacitor Cf. The output voltage Vout of FIG. 2 indicating the amount of change in charge of the self-capacitive sensor Cs has the same voltage polarity as the reference voltage Vref.

The allowable range for the output voltage Vout of the sensing unit is predetermined at the time of design in consideration of the size of the touch IC and the like. However, as the display device becomes larger in area, the size of the touch screen TSP increases, and the mutual capacitance value or the self capacitance value of the touch sensor is increasing. When the capacitance value (CM or CS) of the touch sensor is increased, the output voltage (Vout) of the sensing unit increases as in Equations 1 and 2 above, and in some cases, the output voltage (Vout) of the sensing unit is set within the allowed range. In some cases, a problem of saturation may occur. Since the determination of touch or non-touch is made according to the size of the output voltage Vout of the sensing unit, if the output voltage Vout is saturated outside the allowable range, it becomes impossible to distinguish whether or not touch is performed.

Accordingly, an object of the present invention is to provide a touch sensing system capable of preventing saturation of an output voltage of a sensing unit out of a predetermined allowable range.

In order to achieve the above object, a touch sensing system according to an embodiment of the present invention includes: a touch screen including a plurality of touch sensors and sensor wires connected to the touch sensors; A plurality of sensing units for receiving a touch sensor signal from the touch sensors through a plurality of reception channels and sensing a touch input using the received touch sensor signal; A signal generator for generating charge erasing control signals for controlling output voltages of the sensing units; And a charge eraser formed between the receiving channels and the sensing units, and reducing a variation width of touch sensor signals input to the sensing units in response to the charge erasing control signals.

The present invention can effectively prevent the output voltage of the sensing unit from being saturated out of a predetermined allowable range by reducing the variation width of the touch sensor signal through the charge eraser formed between the receiving channel and the sensing unit.

1 is a view showing a conventional sensing unit when a touch screen is implemented as a mutual capacitive sensor.
2 is a view showing a conventional sensing unit when the touch screen is implemented as a self-capacitive sensor.
3 is a block diagram illustrating a display device to which a touch sensing system according to an embodiment of the present invention is applied.
4 is a diagram illustrating an example of a touch screen implemented by a mutual capacitive sensor.
5 is a diagram illustrating an example of a touch screen implemented with a self-capacitive sensor.
6A to 6C are views showing an example of a touch screen mounted on a display device.
7 is a view showing a touch IC of the present invention further including charge erasers and signal generators in addition to the sensing unit.
8A and 9A are diagrams showing the configuration of a sensing unit to which a charge eraser according to the first embodiment of the present invention is applied, respectively.
8B and 9B are diagrams illustrating an operation timing of FIGS. 8A and 9A and an effect of controlling an output voltage according thereto.
10A and 11A are views each showing a configuration of a sensing unit to which a charge eraser according to a second embodiment of the present invention is applied.
10B and 11B are diagrams showing an operation timing of FIGS. 10A and 11A and an effect of controlling an output voltage according thereto.

The display device to which the touch sensing system of the present invention is applied is a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting diode display. It can be implemented based on flat panel display devices such as devices (Organic Light Emitting Display, OLED) and electrophoresis (EPD) devices. In the following embodiments, a display device as an example of a flat panel display device will be described centering on a liquid crystal display device, but the display device of the present invention is not limited to a liquid crystal display device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numbers throughout the specification mean substantially the same elements. In the following description, when it is determined that a detailed description of a known function or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

3 to 7, the touch sensing system of the present invention includes a touch screen (TSP) and a touch IC 20.

The touch sensing system of the present invention may be implemented as a capacitive touch screen (TSP) that senses a touch input through a plurality of capacitive sensors. The capacitive touch screen includes a plurality of touch sensors. Each of the touch sensors includes a capacitance. The capacitance may be divided into self capacitance and mutual capacitance. The self-capacitance may be formed along a single-layer conductor wiring formed in one direction, and the mutual capacitance may be formed between two orthogonal conductor wirings.

The touch screen TSP implemented by the mutual capacitive sensor Cm includes Tx lines, Rx lines crossing the Tx lines, and touch sensors formed at each intersection of the Tx lines and the Rx lines as shown in FIG. 4. Cm). The Tx lines are driving signal wirings that supply electric charges to the touch sensors by applying a sensor driving pulse signal (driving signal) to each of the touch sensors Cm. The Rx lines are sensor wires connected to the touch sensors Cm and supplying electric charges from the touch sensors to the touch IC 20. In the mutual capacitance sensing method, a driving signal is applied to the Tx electrode through the Tx line to supply charge to the mutual capacitance sensor (Cm), and a touch input is sensed by sensing a change in capacitance through the Rx electrode and Rx line in synchronization with the driving signal. can do.

The touch screen TSP implemented by the self-capacitive sensor Cs may be connected 1:1 to the sensor wires 32 in which each of the touch electrodes 31 is formed along one direction as shown in FIG. 5. The self-capacitance sensor Cs includes a capacitance formed on each of the electrodes 31. In the self-capacitance sensing method, when a driving signal is applied to the electrode 31 through the sensor wiring 32, the electric charge Q is accumulated in the touch sensor Cs. At this time, when a finger or a conductive object comes into contact with the electrode 31, a parasitic capacitance Cf is additionally connected to the self-capacitance sensor Cs, thereby changing a capacitance value. Accordingly, a capacitance value is different between the sensor touched by the finger and the sensor not touched, so that it is possible to determine whether or not the finger touched.

The touch screen TSP may be bonded to the upper polarizing plate POL1 of the display panel as shown in FIG. 6A or formed between the upper polarizing plate POL1 and the upper substrate GLS1 of the display panel as shown in FIG. 6B. Also, the touch sensors Cm or Cs of the touch screen TSP may be embedded in the pixel array of the display panel as shown in FIG. 6C. In FIGS. 6A to 6C, “PIX” denotes a pixel electrode of a liquid crystal cell, “GLS2” denotes a lower substrate, and “POL2” denotes a lower polarizing plate.

The touch IC 20 determines whether a conductive material such as a finger is touched and its location by sensing the amount of change in charge of the touch sensor before and after the touch. The touch IC 20 includes a plurality of sensing units SU#1 to SU#m connected to the reception channels S1 to Sm, and an output voltage Vout1 from the sensing units SU#1 to SU#m. ~Voutm) may include an analog-to-digital conversion unit (ADC) for analog-to-digital conversion.

Each sensing unit SU receives a touch sensor signal from touch sensors through a plurality of reception channels, and senses a touch input using the received touch sensor signal. The receiving channels S1 to Sm may be connected 1:1 to the Rx lines or the sensor wires 32. The sensing unit SU may include a charge amplifier having an operational amplifier OP and a sensing capacitor Cf as shown in FIGS. 8A, 9A, 10A, and 11A to receive a touch sensor signal.

The sensing unit SU may further include a driving signal generator (not shown) to supply a driving signal to the touch sensors Cs or Cm. The driving signal may be generated in various forms such as a square wave type pulse, a sine wave, and a triangle wave, but in the case of the present invention, it is preferable to be implemented as a square wave. The driving signal may be applied N times to each of the touch sensors Cs or Cm so that charges are accumulated N (N is a positive integer of 2 or more) times or more to the charge amplifier of the sensing unit SU. The sensing unit SU accumulates the charge Q from the touch sensors Cs or Cm in the charge amplifier and supplies it to the ADC. The ADC converts the output voltage Vout from the sensing unit SU into a digital value. In addition, the touch IC 20 may perform a touch sensing algorithm to compare the ADC result value with a reference value and determine a result value greater than the reference value as the touch sensor signal at the touch input position. The touch report output from the touch IC 20 may be transmitted to the host system 18 including coordinate information (TDATA(XY)) of each of the touch inputs.

In order to solve the problem that the output voltage Vout of the sensing unit SU on the large-screen touch screen TSP is out of the specified allowable range, saturation occurs, the touch IC 20 of the present invention includes a plurality of touch ICs as shown in FIG. 7. The charge erasing units CR#1 to CR#m and a signal generation unit PGR may be provided.

The signal generator PGR generates charge erasing control signals for controlling the output voltages of the sensing units SU#1 to SU#m. The charge erasing control signals include a charge erasing pulse signal (Vcr in FIGS. 8A to 11B) to be described later, and first and second switching control signals (signals for switching SW1 and SW2 in FIGS. 8A to 11B) to be described later. Includes.

The charge erasing units CR#1 to CR#m are formed between the reception channels S1 to Sm and the sensing units SU#1 to SU#m, and are sensed in response to control signals for charge erasing. It serves to reduce the variation width of the touch sensor signals input to the units SU#1 to SU#m.

The detailed configuration and operation of the sensing units SU#1 to SU#m together with the charge erasing units CR#1 to CR#m will be described in detail with reference to FIGS. 8A to 11B.

Meanwhile, a display device to which the touch sensing system of the present invention is applied may include a display panel DIS, display driving circuits 12, 14, and 16, and a host system 18.

The display panel DIS includes a liquid crystal layer formed between two substrates. The pixel array of the display panel DIS includes pixels formed in a pixel area defined by data lines (D1 to Dm, m is a positive integer) and gate lines (G1 to Gn, n is a positive integer). . Each of the pixels is connected to TFTs (Thin Film Transistor) formed at the intersections of the data lines D1 to Dm and the gate lines G1 to Gn, a pixel electrode charging the data voltage, and a pixel electrode. It may include a storage capacitor (Cst) for maintaining the voltage.

A black matrix, a color filter, or the like may be formed on the upper substrate of the display panel DIS. The lower substrate of the display panel DIS may be implemented in a color filter on TFT (COT) structure. In this case, the black matrix and the color filter may be formed on the lower substrate of the display panel DIS. The common electrode to which the common voltage is supplied may be formed on the upper or lower substrate of the display panel DIS. A polarizing plate is attached to each of the upper and lower substrates of the display panel DIS, and an alignment layer for setting a pretilt angle of the liquid crystal is formed on an inner surface in contact with the liquid crystal. A column spacer is formed between the upper substrate and the lower substrate of the display panel DIS to maintain a cell gap of the liquid crystal cell.

A backlight unit may be disposed under the rear surface of the display panel DIS. The backlight unit is implemented as an edge type or direct type backlight unit and irradiates light to the display panel DIS. The display panel DIS may be implemented in any known liquid crystal mode such as a twisted nematic (TN) mode, a vertical alignment (VA) mode, an in plane switching (IPS) mode, and a fringe field switching (FFS) mode.

The display driving circuit includes a data driving circuit 12, a scan driving circuit 14, and a timing controller 16 to write video data of an input image to pixels of the display panel DIS. The data driving circuit 12 converts digital video data RGB input from the timing controller 16 into an analog positive/negative gamma compensation voltage and outputs a data voltage. The data voltage output from the data driving circuit 12 is supplied to the data lines D1 to Dm. The scan driving circuit 14 sequentially supplies a gate pulse (or scan pulse) synchronized with the data voltage to the gate lines G1 to Gn to select a pixel line of the display panel DIS to which the data voltage is written.

The timing controller 16 inputs timing signals such as a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), a data enable signal (Data Enable, DE), and a main clock (MCLK) input from the host system 18. In response, the operation timing of the data driving circuit 12 and the scan driving circuit 14 is synchronized. The scan timing control signal includes a gate start pulse (GSP), a gate shift clock, a gate output enable signal (Gate Output Enable, GOE), and the like. The data timing control signal includes a source sampling clock (SSC), a polarity control signal (Polarity, POL), a source output enable signal (Source Output Enable, SOE), and the like.

The host system 18 may be implemented as any one of a television system, a set-top box, a navigation system, a DVD player, a Blu-ray player, a personal computer (PC), a home theater system, and a phone system. The host system 18 converts the digital video data RGB of an input image into a format suitable for display on the display panel DIS, including a system on chip (SoC) with a built-in scaler. The host system 18 transmits timing signals Vsync, Hsync, DE, and MCLK together with the digital video data to the timing controller 16. In addition, the host system 18 executes an application program linked with coordinate information (XY) of the touch report input from the touch screen driving circuit.

8A and 9A show the configuration of a sensing unit to which a charge eraser according to the first embodiment of the present invention is applied, respectively, and FIGS. 8B and 9B are operation timings of FIGS. 8A and 9A and output voltage control according thereto. Show the effect. The charge eraser CR according to the first embodiment may be implemented with a charge erase capacitor Ccr as shown in FIGS. 8A and 9A.

First, when the touch screen TSP is implemented with the mutual capacitive sensor Cm, the sensing unit SU may include an operational amplifier OP and a sensing capacitor Cf as shown in FIG. 8A. The inverting input terminal (-) of the operational amplifier (OP) is connected to the mutual capacitance sensor (Cm) through the receiving channel, and the non-inverting input terminal (+) of the operational amplifier (OP) is connected to the reference voltage (Vref) terminal. , The output terminal of the operational amplifier OP may be connected to the inverting input terminal (-) via the sensing capacitor Cf. The sensing capacitor Cf has a function of integrating a touch sensor signal input through the inverting input terminal (-). The reset switch RST of the sensing unit SU performs a function of resetting the sensing capacitor Cf at a predetermined period.

In the charge erasing capacitor Ccr constituting the charge erasing unit CR, one electrode thereof is connected to the inverting input terminal (-) of the operational amplifier OP, and the other electrode thereof is the charge erasing pulse signal Vcr. It is connected to the input terminal. Here, to reduce the variation width of the touch sensor signals, the charge erasing pulse signal Vcr is the same pulse width PWM as compared to the sensor driving pulse signal Vtx applied to the mutual capacitance sensor Cm as shown in FIG. 8B. And a feature of having an opposite phase.

In the sensing unit SU of FIG. 8A, the operational amplifier OP functions as an inverting amplifier. The output voltage Vout of the sensing unit can be expressed as Equation 3 due to the charge eraser CR.

In Equation 3, the reference voltage Vref is a direct current (DC) level, Vtx represents the driving voltage applied to the mutual capacitance sensor Cm, CM represents the mutual capacitance of the mutual capacitance sensor Cm, and CF is Represents the capacity of the sensing capacitor Cf, CCR denotes the capacity of the charge erasing capacitor Ccr, and Vcr denotes the charge erasing pulse signal applied to the charge erasing capacitor Ccr.

As can be seen from Equation 3 and FIG. 8B, the output voltage Vout of the sensing unit SU is entering the allowable range of the predetermined output voltage Vout due to the application of the charge eraser CR.

For example, the allowable range of the output voltage (Vout) of the sensing unit (SU) is set to 0V to 3.3V, Vref=1.65V, Vtx=3.3V, CM=10pF, CF=10pF, Vcr=-15V, CCR=2pF Assuming this, the output voltage Vout of the conventional sensing unit SU is Vout=1.65V-3.3V*(10pF/10pF)=-1.65V according to Equation 1, so that the allowable range (0V to 3.3V) is set. The output voltage (Vout) is eventually saturated to 0V. On the other hand, the output voltage Vout of the sensing unit SU according to the first embodiment is Vout=1.65V-3.3V*(10pF/10pF)-(-15V)*(2pF/10pF)= It becomes 1.35V and satisfies the allowable range (0V~3.3V).

Next, when the touch screen TSP is implemented with the self-capacitive sensor Cs, the sensing unit SU may include an operational amplifier OP and a sensing capacitor Cf as shown in FIG. 9A. The inverting input terminal (-) of the operational amplifier (OP) is connected to the mutual capacitance sensor (Cm) through the receiving channel, and the non-inverting input terminal (+) of the operational amplifier (OP) is connected to the reference voltage (Vref) terminal. , The output terminal of the operational amplifier OP may be connected to the inverting input terminal (-) via the sensing capacitor Cf. In order to sense the self-capacitance sensor Cs, the reference voltage Vref is input as an AC-type reference voltage pulse signal swinging between the high potential level VH and the low potential level VL. The sensing capacitor Cf has a function of integrating a touch sensor signal input through the inverting input terminal (-). The reset switch RST of the sensing unit SU performs a function of resetting the sensing capacitor Cf at a predetermined period.

In the charge erasing capacitor Ccr constituting the charge erasing unit CR, one electrode thereof is connected to the inverting input terminal (-) of the operational amplifier OP, and the other electrode thereof is the charge erasing pulse signal Vcr. It is connected to the input terminal. Here, the charge erasing pulse signal Vcr has the same pulse width PW2 and the same phase as compared to the reference voltage pulse signal Vref as shown in FIG. 9B so that the variation width of the touch sensor signals is reduced.

In the sensing unit SU of FIG. 9A, the operational amplifier OP functions as a non-inverting amplifier. The output voltage Vout of the sensing unit can be expressed as in Equation 4 due to the charge eraser CR.

In Equation 4, the reference voltage Vref is an AC level that swings between the high potential level VH and the low potential level VL, ΔVref represents the swing width of the reference voltage Vref, and CS is Self-capacitance sensor (Cs) represents the self-capacity, CF represents the capacity of the sensing capacitor (Cf), CCR represents the capacity of the charge erasing capacitor (Ccr), Vcr is applied to the charge erasing capacitor (Ccr). Represents a pulse signal for erasing charge.

As can be seen in Equation 4 and FIG. 9B, the output voltage Vout of the sensing unit SU is entering the allowable range of the predetermined output voltage Vout due to the application of the charge erasing unit CR.

For example, assume that the allowable range of the output voltage (Vout) of the sensing unit (SU) is set to 0V to 3.3V, and Vref=1.65V±0.08V, CS=200pF, CF=10pF, Vcr=-15V, CCR=2pF Then, the output voltage Vout of the conventional sensing unit SU is Vout=(1.65V+0.08V)+(-0.16V)*(1+(200pF/10pF))=-1.63V by Equation 2 As a result, it goes out of the allowable range (0V~3.3V), and eventually the output voltage (Vout) is saturated to 0V. On the other hand, the output voltage Vout of the sensing unit SU according to the first embodiment is Vout=1.73V+(-0.16V)*(1+((200pF+2pF)/10pF))-( -15V)*(2pF/10pF)=1.38V, satisfying the allowable range (0V~3.3V).

As such, in the first embodiment of the present invention, as shown in FIGS. 8A to 9B, the charge eraser CR is further included, and the same pulse is compared with the pulse signal Vcr for driving the charge and the pulse signal Vtx for driving the sensor. Sensing units are applied to the sensing unit (SU) once to have a width and opposite phase, or applied to the sensing unit (SU) once to have the same pulse width and phase compared to the reference voltage pulse signal (Vref). It is possible to reduce the variation width of the touch sensor signals input to the device.

However, in order to obtain the desired effect in the first embodiment, it is necessary to use a charge erasing pulse signal (Vcr) with a large voltage swing width and a charge erasing capacitor (Ccr) with a large capacity, which requires a high voltage process. It can lead to the disadvantage of increasing the size.

10A and 11A respectively show the configuration of a sensing unit to which a charge eraser according to a second embodiment of the present invention is applied, and FIGS. 10B and 11B are operation timings of FIGS. 10A and 11A and output voltage control accordingly. Show the effect. The charge eraser CR according to the second embodiment may be implemented with a charge erase capacitor Ccr and first and second switches as shown in FIGS. 10A and 11A.

First, when the touch screen TSP is implemented as a mutual capacitive sensor Cm, the sensing unit SU is as shown in FIG. 10A, which is substantially the same as that described in FIG. 8A.

In the charge erasing capacitor Ccr constituting the charge erasing unit CR, one electrode thereof is connected to the inverting input terminal (-) of the operational amplifier OP, and the other electrode thereof is the charge erasing pulse signal Vcr. It is connected to the input terminal. The charge erasing unit CR according to the second embodiment includes a first switch SW1 connected between one electrode of the charge erasing capacitor Ccr and the inverting input terminal (-) of the operational amplifier OP, and a charge erasing. A second switch SW2 connected between one electrode of the capacitor Ccr and the non-inverting input terminal (+) of the operational amplifier OP is further provided. The first and second switches SW1 and SW2 are switched opposite to each other according to a switching control signal belonging to control signals for erasing charge.

Here, the switching control signal may be generated based on the charge erasing pulse signal Vcr. In order to reduce the width of change of the touch sensor signals, the charge erasing pulse signal Vcr has an opposite phase compared to the sensor driving pulse signal Vtx applied to the mutual capacitance sensor Cm as shown in FIG. 10B and has a sensor driving pulse. Within the pulse width PW1 of the signal Vtx, it may be applied multiple times to the other electrode of the charge erasing capacitor Ccr. By such an increase in the number of applications, the second embodiment can effectively prevent a disadvantage in the first embodiment, that is, a high voltage process is required and the size of the touch IC is increased.

As shown in FIG. 10B, each time the pulse signal Vcr for charge erasing is polled multiple times from the high potential level (3.3V) to the low potential level (0V) within the pulse width PW1 of the sensor driving pulse signal Vcr. , The first switch SW1 may be turned on and the second switch SW2 may be turned off at a timing prior to the polling time point for a predetermined time Td. The reason why the first switch SW1 is turned on prior to the polling time of the charge erasing pulse signal Vcr is to secure operation stability. The reason for turning on the second switch SW2 while the first switch SW1 is off is to stabilize the potential of one electrode of the charge erasing capacitor Ccr to a predetermined value Vref prior to sampling. When the first switch SW1 is turned on, the charge erasing pulse signal Vcr is polled, and as the number of polling increases, the accumulated number of adjustments of the output voltage Vout increases. Therefore, in the second embodiment, since the desired effect related to the output voltage (Vout) limitation can be sufficiently obtained only with the charge erasing pulse signal Vcr having a small voltage swing width and the charge erasing capacitor Ccr having a small capacity. The shortcomings in the example can be easily eliminated.

In the sensing unit SU of FIG. 10A, the operational amplifier OP functions as an inverting amplifier. The output voltage Vout of the sensing unit can be expressed as in Equation 5 due to the charge eraser CR.

In Equation 5, the reference voltage Vref is a direct current (DC) level, Vtx represents the driving voltage applied to the mutual capacitance sensor Cm, CM represents the mutual capacitance of the mutual capacitance sensor Cm, and CF is Represents the capacity of the sensing capacitor Cf, CCR represents the capacity of the charge erasing capacitor Ccr, Vcr represents the charge erasing pulse signal applied to the charge erasing capacitor Ccr, and n represents the number of applications. .

As can be seen from Equation 5 and FIG. 10B, the output voltage Vout of the sensing unit SU is entering the allowable range of the predetermined output voltage Vout due to the application of the charge erasing unit CR, and in particular, n times. There is an effect of reducing the size of the touch IC through the repetitive charge erasing operation.

For example, the allowable range of the output voltage (Vout) of the sensing unit (SU) is set to 0V to 3.3V, Vref=1.65V, Vtx=3.3V, CM=10pF, CF=10pF, Vcr=-3.3V, CCR= Assuming that 2pF and n=4, the output voltage Vout of the sensing unit SU according to the second embodiment is Vout=1.65V-3.3V*(10pF/10pF)-4*(- 3.3V)*(2pF/10pF)=0.99V, satisfying the allowable range (0V~3.3V). This shows that even with Vcr=-3.3V and CCR=2pF, the desired effect can be sufficiently obtained.

Next, when the touch screen TSP is implemented with the self-capacitive sensor Cs, the sensing unit SU is as shown in FIG. 11A, which is substantially the same as that described in FIG. 9A. In order to sense the self-capacitance sensor Cs, the reference voltage Vref is input as an AC-type reference voltage pulse signal swinging between the high potential level VH and the low potential level VL.

In the charge erasing capacitor Ccr constituting the charge erasing unit CR, one electrode thereof is connected to the inverting input terminal (-) of the operational amplifier OP, and the other electrode thereof is the charge erasing pulse signal Vcr. It is connected to the input terminal. The charge eraser CR according to the second embodiment includes a first switch SW1 connected between one electrode of a charge erase capacitor Ccr and an inverting input terminal (-) of the operational amplifier OP, and a charge eraser. A second switch SW2 connected between one electrode of the capacitor Ccr and the non-inverting input terminal (+) of the operational amplifier OP is further provided. The first and second switches SW1 and SW2 are switched opposite to each other according to a switching control signal belonging to control signals for erasing charge.

Here, the switching control signal may be generated based on the charge erasing pulse signal Vcr. In order to reduce the variation width of the touch sensor signals, the charge erasing pulse signal Vcr has the same phase compared to the reference voltage pulse signal Vref as shown in FIG. 11B, and the pulse width PW2 of the reference voltage pulse signal Vref ) May be applied multiple times to the other electrode of the capacitor Ccr for erasing charge. By such an increase in the number of applications, the second embodiment can effectively prevent a disadvantage in the first embodiment, that is, a high voltage process is required and the size of the touch IC is increased.

As shown in FIG. 11B, every time a pulse signal for erasing charge (Vcr) is polled multiple times from a high potential level (3.3V) to a low potential level (0V) within the pulse width PW2 of the sensor driving pulse signal Vcr. , The first switch SW1 may be turned on and the second switch SW2 may be turned off at a timing prior to the polling time point for a predetermined time Td. The reason why the first switch SW1 is turned on prior to the polling time of the charge erasing pulse signal Vcr is to secure operation stability. The reason for turning on the second switch SW2 while the first switch SW1 is off is to stabilize the potential of one electrode of the charge erasing capacitor Ccr to a predetermined value Vref prior to sampling. When the first switch SW1 is turned on, the charge erasing pulse signal Vcr is polled, and as the number of polling increases, the accumulated number of adjustments of the output voltage Vout increases. Therefore, in the second embodiment, since the desired effect related to the output voltage (Vout) limitation can be sufficiently obtained only with the charge erasing pulse signal Vcr having a small voltage swing width and the charge erasing capacitor Ccr having a small capacity. The shortcomings in the example can be easily eliminated.

In the sensing unit SU of FIG. 11A, the operational amplifier OP functions as a non-inverting amplifier. The output voltage Vout of the sensing unit can be expressed as Equation 6 due to the charge eraser CR.

In Equation 6, the reference voltage Vref is an AC level swinging between the high potential level VH and the low potential level VL, ΔVref represents the swing width of the reference voltage Vref, and CS is Self-capacitance sensor (Cs) represents the self-capacity, CF represents the capacity of the sensing capacitor (Cf), CCR represents the capacity of the charge erasing capacitor (Ccr), Vcr is applied to the charge erasing capacitor (Ccr). Represents a pulse signal for charge erasing, and n represents the number of times of application.

As can be seen from Equation 6 and FIG. 11B, the output voltage Vout of the sensing unit SU is entering the allowable range of the predetermined output voltage Vout due to the application of the charge erasing unit CR, and in particular, n times. There is an effect of reducing the size of the touch IC through the repetitive charge erasing operation.

For example, the allowable range of the output voltage (Vout) of the sensing unit (SU) is set to 0V to 3.3V, Vref=1.65V±0.08V, CS=200pF, CF=10pF, Vcr=-3.3V, CCR=2pF, Assuming that n=4, the output voltage Vout of the sensing unit SU according to the second embodiment is Vout=1.73V+(-0.16V)*(1+((200pF+2pF)/ 10pF))-4*(-3.3V)*(2pF/10pF)=1.02V, satisfying the allowable range (0V~3.3V).

As described above, in the second embodiment of the present invention, as shown in FIGS. 10A and 10B, a charge erasing unit CR is further included, and an opposite phase by comparing the charge erasing pulse signal Vcr with the sensor driving pulse signal Vtx. And a plurality of times applied to the other electrode of the charge erasing capacitor Ccr within the sensor driving pulse signal Vtx, effectively reducing the variation width of the touch sensor signals input to the sensing units without increasing the size of the touch IC. I can.

In addition, as shown in FIGS. 11A and 11B, the second embodiment of the present invention further includes a charge eraser CR, and compares the charge erase pulse signal Vcr with the reference voltage pulse signal Vref. And the change width of the touch sensor signals input to the sensing units without increasing the size of the touch IC by applying multiple times to the other electrode of the charge erasing capacitor Ccr within the pulse width of the reference voltage pulse signal Vref. Can be effectively reduced.

It will be appreciated by those skilled in the art through the above description that various changes and modifications can be made without departing from the technical idea of the present invention. Accordingly, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

DIS: Display panel TSP: Touch screen
12: data driving circuit 14: scan driving circuit
16: timing controller 18: host system
20: touch IC

Claims (10)

A touch screen including a plurality of touch sensors outputting a touch sensor signal according to a touch driving pulse, and sensor wires connected to the touch sensors;
A plurality of sensing units for receiving the touch sensor signal from the touch sensors through a plurality of reception channels and sensing a touch input using the received touch sensor signal;
A signal generator for generating a pulse signal for erasing charge for controlling the output voltage of the sensing units; And
And a charge erasing capacitor having one electrode connected between the receiving channels and the sensing units and the other electrode to which the charge erasing pulse signal is directly applied, and the output voltage of the sensing unit does not exceed a predetermined allowable range. A charge eraser to reduce a variation width of the touch sensor signals input to the sensing units by using the charge erase pulse signal,
The first transition edge of the charge erasing pulse signal is synchronized with the first transition edge of the touch driving pulse, and the last transition edge of the charge erasing pulse signal is synchronized with the last transition edge of the touch driving pulse. Touch sensing system. The method of claim 1,
Each of the sensing units includes an inverting input terminal to which the touch sensor signal is input from the receiving channel, a non-inverting input terminal to which a reference voltage is input, and an operational amplifier having an output terminal to which the output voltage is output, and the op. A sensing capacitor connected between the inverting input terminal and the output terminal of the amplifier;
One electrode of the charge erasing capacitor is connected to an inverting input terminal of the op amp, and the other electrode of the charge erasing capacitor is connected to an input terminal of the charge erasing pulse signal. The method of claim 2,
The touch sensors are implemented as mutual capacitive sensors, and the mutual capacitive sensors are formed at intersections of the sensor wires orthogonal to each other with a dielectric layer therebetween,
The charge erasing pulse signal has the same pulse width and opposite phase compared to the touch driving pulse applied to the mutual capacitive sensor, and has a larger pulse amplitude. The method of claim 2,
The touch sensors are implemented as self-capacitive sensors, the self-capacitive sensors are connected to the sensor wires formed along one direction, and the reference voltage is an AC type swinging between a first high potential level and a first low potential level Is input as the touch driving pulse of,
The charge erasing pulse signal has the same pulse width and phase as that of the touch driving pulse, and has a larger pulse amplitude. The method of claim 2,
The charge erasing unit,
A first switch connected between one electrode of the charge erasing capacitor and an inverting input terminal of the op amp; And
A second switch connected between one electrode of the charge erasing capacitor and a non-inverting input terminal of the op amp;
The first and second switches are switched opposite to each other according to a switching control signal further generated by the signal generator. The method of claim 5,
The switching control signal is generated based on a pulse signal for erasing charge applied to the other electrode of the capacitor for erasing charge. The method of claim 6,
The touch sensors are implemented as mutual capacitive sensors, and the mutual capacitive sensors are formed at intersections of the sensor wires orthogonal to each other with a dielectric layer therebetween,
The charge erasing pulse signal is implemented as a plurality of pulses having the same pulse amplitude and opposite phase compared to the touch driving pulse applied to the mutual capacitive sensor, and swinging within the pulse width of the touch driving pulse. Touch sensing system, characterized in that. The method of claim 7,
Whenever the charge erasing pulse signal is polled a plurality of times from the second high potential level to the second low potential level within the pulse width of the touch driving pulse, the first switch is turned on at a timing preceding this polling time. And at the same time, the second switch is turned off. The method of claim 6,
The touch sensors are implemented as self-capacitive sensors, the self-capacitive sensors are connected to the sensor wires formed along one direction, and the reference voltage is an AC type swinging between a first high potential level and a first low potential level Is input as the touch driving pulse of,
The charge erasing pulse signal has a larger pulse amplitude and the same phase compared to the touch driving pulse, and is implemented by a plurality of pulses swinging within a pulse width of the touch driving pulse. . The method of claim 9,
Whenever the charge erasing pulse signal is polled a plurality of times from the second high potential level to the second low potential level within the pulse width of the touch driving pulse, the first switch is turned on at a timing preceding this polling time. And at the same time, the second switch is turned off.

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