KR101553605B1 - Touch detecting apparatus and method - Google Patents

Abstract

According to an embodiment of the present invention, a sensor pad for outputting a sensing signal according to a touch state in response to a reference voltage after an initialization process; An operational amplifier having a first input connected to the sensor pad and a second input receiving the reference voltage and outputting different signals in response to the sensing signal; A first switch for controlling a potential at both ends of a driving capacitance connected between a first input terminal and an output terminal of the operational amplifier; A second switch which is alternately turned on and off with respect to the first switch and switches connection between the sensor pad and the first input terminal of the operational amplifier; And a second switch control circuit for controlling on / off of the second switch based on the sensing signal.

Description

TECHNICAL FIELD [0001] The present invention relates to a touch detection apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a touch detection apparatus and method, and more particularly, to a touch detection apparatus and method with a minimized influence on noise while ensuring linearity.

The touch screen panel is a device for inputting a command of a user by touching a character or a figure displayed on the screen of the image display device with a finger or other contact means of a person, and is attached and used on the image display device. The touch screen panel converts a contact position that is touched by a human finger or the like into an electrical signal. The electrical signal is used as an input signal.

1 is an exploded top view of an example of a conventional capacitive touch screen panel.

1, a touch screen panel 10 includes a transparent substrate 12 and a first sensor pattern layer 13, a first insulating layer 14, and a second sensor pattern layer (not shown) sequentially formed on a transparent substrate 12 15, a second insulating film layer 16, and a metal wiring 17.

The first sensor pattern layer 13 may be connected on the transparent substrate 12 along the lateral direction and connected to the metal wiring 17 on a row-by-row basis.

The second sensor pattern layer 15 may be connected to the first insulating layer 14 along the column direction and alternately arranged with the first sensor pattern layer 13 so as not to overlap the first sensor pattern layer 13 . In addition, the second sensor pattern layer 15 is connected to the metal wiring 17 on a row basis.

When a human finger or a contact means is brought into contact with the touch screen panel 10, a change in capacitance according to the contact position is transmitted to the drive circuit side through the first and second sensor pattern layers 13 and 15 and the metal wiring 17 do. Then, the contact position is determined as the change in capacitance transferred is converted into an electrical signal.

However, the touch screen panel 10 must have a separate pattern of transparent conductive material such as indium tin oxide (ITO) on each of the sensor pattern layers 13 and 15, The insulating layer 14 must be provided to increase the thickness.

In addition, since the touch detection can be performed by accumulating the changes of capacitance slightly generated by the touch several times, it is necessary to detect the capacitance change at a high frequency. In order to sufficiently accumulate the capacitance change within a predetermined time, a metal wiring is required to maintain a low resistance, which thickens the bezel at the edge of the touch screen and generates an additional mask process.

To solve this problem, a touch detection apparatus as shown in Fig. 2 has been proposed.

2 includes a touch panel 20, a driving device 30, and a circuit board 40 connecting the two.

The touch panel 20 includes a plurality of sensor pads 22 formed on a substrate 21 and arranged in the form of a polygonal matrix and a plurality of signal wirings 23 connected to the sensor pads 22.

Each signal wiring 23 has one end connected to the sensor pad 22 and the other end extending to the lower edge of the substrate 21. The sensor pad 22 and the signal wiring 23 can be patterned on the cover glass 50. [

The driving device 30 sequentially selects a plurality of sensor pads 22 one by one to measure the electrostatic capacitance of the corresponding sensor pad 22, thereby detecting whether or not a touch is generated.

FIG. 3 is an equivalent circuit diagram for explaining an operation of performing touch detection when a touch occurs in the touch detection apparatus of FIG. 2. FIG.

3, when a touch occurs, a touch capacitance Ct is formed between a touch generating tool (for example, a finger) and the sensor pad 22, and a common capacitance Ct is formed between the sensor pad 22 and the common electrode. A capacitance Cvcom is formed. An unknown parasitic capacitance Cp is formed in the sensor pad 22 and a driving capacitance Cdrv is formed between the sensor pad 22 and the alternate voltage Vdrv supply path.

The touch detection method of the touch detection device will be described as follows.

First, the sensor pad 22 is charged by the charging signal Vb. Thereafter, when the supply of the charging signal Vb is interrupted by the transistor, the charges charged in the touch capacitance Ct, the parasitic capacitance Cp, the driving capacitance Cdrv and the common voltage capacitance Cvcom are isolated do. This charge isolated state is referred to as a floating state. At this time, when the alternating voltage Vdrv is applied, the output voltage Vo of the sensor pad 22 changes in accordance with the alternating voltage Vdrv. In this case, the rise and fall of the output voltage Vo have different values depending on the connected capacitances. The phenomenon that the rising or falling value of the voltage level changes depending on the connected capacitance is called a " kick-back " .

The voltage variation (? Vo) of the output voltage (Vo) of the sensor pad (22) when a touch occurs in the touch detection apparatus can be expressed by the following Equation (1).

Here, VdrvH and VdrvL are the high level voltage and the low level voltage of the alternating voltage Vdrv, respectively.

Since the touch capacitance Ct is located in the denominator in Equation 1, the output voltage variation? Vo (level shift value) before and after the touch does not have a linear relationship with the touch capacitance Ct.

Since the level shift value DELTA Vo before and after the touch corresponds to the touch area related to the touch capacitance Ct, if the linearity between the level shift value DELTA Vo and the touch capacitance Ct is secured, The coordinates can be obtained.

Therefore, a technique capable of securing linearity between the level shift value before and after the touch and the touch capacitance is required. In addition, a touch detecting apparatus which is not vulnerable to noise is required while securing such linearity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a touch detection apparatus and method in which linearity between a level shift value and a touch capacitance is ensured while external noise is minimized.

According to an aspect of the present invention, there is provided a touch sensing apparatus including: a sensor pad for outputting a sensing signal according to a touch state in response to a reference voltage after initialization; An operational amplifier having a first input connected to the sensor pad and a second input receiving the reference voltage and outputting different signals in response to the sensing signal; A first switch for controlling a potential at both ends of a driving capacitance connected between a first input terminal and an output terminal of the operational amplifier; A second switch which is alternately turned on and off with respect to the first switch and switches connection between the sensor pad and the first input terminal of the operational amplifier; And a second switch control circuit for controlling on / off of the second switch based on the sensing signal.

And the second switch control circuit controls the on / off state of the second switch based on the potential of the first node connected to the sensor pad and the second switch or the first node of the operational amplifier and the second node connected to the drive capacitance, Off.

Wherein the second switch control circuit compares the sensing signal with a threshold voltage to output a first signal when the sensing signal is greater than or equal to the first potential and output a second signal when the sensing signal is less than the second potential; And a second switch control unit for turning off the second switch in response to the first signal and controlling the second switch to be turned on in response to the second signal.

The first potential may be a potential lower than the reference voltage, and the second potential may be lower than the first potential.

The second switch control circuit outputs a first signal when the potential fluctuation width of the sensing signal is equal to or greater than the threshold value and outputs a second signal when the potential fluctuation width of the sensing signal is less than the threshold value A comparator; And a second switch control unit for controlling the switching of the second switch to be repeated in response to the first signal and for controlling the second switch to be in the off state in response to the second signal.

The threshold voltage may be less than or equal to the reference voltage.

The touch detection apparatus may further include a level shift detection section for detecting whether or not the touch is detected based on a voltage variation at the output terminal of the operational amplifier according to the reference voltage.

According to another embodiment of the present invention, there is provided a method of driving a plasma display panel, comprising: initializing a driving capacitance in which a connection between a sensor pad and a sensor pad is switched; Coupling the sensor pad coupled to the first input of the operational amplifier to the driving capacitance; And switching the connection between the sensor pad and the driving capacitance based on a sensing signal output from the sensor pad in response to a reference voltage applied to a second input of the operational amplifier, / RTI >

The switching control step may include switching the connection between the sensor pad and the driving capacitance based on an output terminal potential of the sensor pad or a potential of the first input terminal.

Wherein the switching control step comprises the step of comparing and intercepting the sensor pad and the driving capacitance when the sensing signal is greater than or equal to the first potential or when the sensing signal is less than the second potential, . ≪ / RTI >

The first potential may be a potential lower than the potential of the reference voltage, and the second potential may be lower than the first potential.

Wherein the switching control step comprises the step of comparing the threshold voltage with the sensing signal and repeating the connection and disconnection between the sensor pad and the driving electrostatic capacitance when the potential fluctuation width of the sensing signal is equal to or greater than the threshold value, And maintaining the blocking between the sensor pad and the driving capacitance when the threshold is less than the threshold.

The threshold voltage may be less than or equal to the reference voltage.

The touch detection method may further include a step of detecting whether or not the touch is detected based on a voltage variation at the output terminal of the operational amplifier according to the reference voltage.

According to another embodiment of the present invention, there is provided a touch pad device including: a sensor pad forming a touch capacitance in relation to a touch input tool; A first switch connected between the sensor pad and the ground terminal, the first switch being ON only in the process of initializing the sensor pad; An operational amplifier having a first input terminal receiving a sensing signal output from the sensor pad and a second input terminal receiving a reference voltage based on the touch capacitance and outputting a touch detection signal; A driving electrostatic capacitance connected between the first input terminal and the output terminal of the operational amplifier; A second switch connected to both ends of the driving capacitance, the second switch being ON only while the sensor pad is being charged; A third switch connected between the sensor pad and a first input terminal of the operational amplifier, the third switch being alternately turned on and off with respect to the first switch and the second switch; And a third switch control unit for comparing the sensing signal with a preset threshold voltage to control on-off of the third switch.

According to the embodiment of the present invention, since the level shift value serving as a basis of touch detection and the touch capacitance have linearity, it is possible to easily obtain an output value in a linear relationship. On the other hand, The influence on external noise can also be reduced.

1 is an exploded top view of a conventional touch screen panel.
2 is an exploded top view of a conventional touch detection device.
FIG. 3 is an equivalent circuit diagram for explaining an operation of performing touch detection when a touch occurs in the touch detection apparatus of FIG. 2. FIG.
4 is a circuit diagram illustrating a touch detection apparatus according to an embodiment.
5 is a circuit diagram illustrating a touch detection apparatus according to another embodiment.
6 is a circuit diagram illustrating a touch detection apparatus according to an embodiment of the present invention.
7 is a waveform diagram for explaining the operation of the touch detection apparatus shown in Fig.
8 is a circuit diagram illustrating a touch detection apparatus according to another embodiment of the present invention.
9 is a waveform diagram for explaining the operation of the touch detection apparatus shown in Fig.

The terms used in this specification will be briefly described and the present invention will be described in detail.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Also, in certain cases, there may be a term selected arbitrarily by the applicant, in which case the meaning thereof will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term, not on the name of a simple term, but on the entire contents of the present invention.

When an element is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements as well, without departing from the spirit or scope of the present invention. Also, the terms "part," " module, "and the like described in the specification mean units for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software . When a part is "connected" to another part, it includes not only a direct connection but also a connection with another system in the middle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

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

4 is a circuit diagram illustrating a touch detection apparatus according to an embodiment.

4, the touch sensing device 400 includes a sensor pad 410, a touch capacitance Ct, a parasitic capacitance Cp, a driving capacitance Cdrv, a transistor Q, an operational amplifier OP- amp, and an analog-to-digital converter (ADC).

The sensor pad 410 forms a touch capacitance Ct with the touch input tool as a patterned electrode on the substrate for touch input detection, and outputs a sensing signal according to the touch state. The sensor pads 410 may be formed in a plurality of independent polygons, and may be formed of a transparent conductive material. For example, the sensor pad 410 may be formed of a transparent conductive material such as indium tin oxide (ITO), antimony tin oxide (ATO), indium zinc-oxide (IZO), carbon nanotube (CNT), or graphene ≪ / RTI >

The transistor Q, the parasitic capacitance Cp and the driving capacitance Cdrv can be grouped into one each for the sensor pad 410 and the signal wiring (not shown) connected thereto. The sensor pad 410, the signal wiring, the transistor Q, the parasitic capacitance Cp, and the driving capacitance Cdrv are collectively referred to as a "touch sensing unit ". This touch sensing unit is a concept that includes the case where each component is electrically connected by a multiplexer.

The transistor Q may be a field effect transistor, for example, a control signal Vg may be applied to a gate, a charge signal Vb may be applied to a source, May be connected to signal lines connected to each of the plurality of sensor pads 410. Of course, the source may be connected to the signal line and the charge signal Vb may be applied to the drain. The transistor Q may be replaced with another element capable of switching according to a predetermined control signal.

The parasitic capacitance Cp means a capacitance attached to the sensor pad 410 and is a kind of parasitic capacitance formed by the sensor pad 410 or signal wiring. The parasitic capacitance Cp may be a concept including capacitance formed between the touch sensing device 400 and the common electrode of the display device when the touch sensing device 400 is mounted on a display device such as an LCD.

The driving electrostatic capacitance Cdrv is a capacitance formed in a path that supplies the reference voltage Vref to the sensor pad 410. [ The reference voltage Vref may be a square wave signal. The reference voltage Vref may be a clock signal having the same duty ratio, but may have a different duty ratio.

The first input terminal N2 of the operational amplifier OP-amp is connected to the output terminal N1 of the sensor pad 410 which is the touch detection object among the plurality of sensor pads and a sensing signal is applied. (Vref) is applied. A driving capacitance Cdrv is connected between the first input terminal N2 and the output terminal N3 of the operational amplifier OP-amp and a charging signal Vb is connected to the output terminal N3 of the operational amplifier OP- And the supply and cutoff of the charging signal (Vb) is controlled by the first switch (SW1). The second switch SW2 is connected between the first input terminal N2 of the operational amplifier OP-amp and the output terminal N1 of the sensor pad 410. The output terminal N3 of the operational amplifier OP-amp outputs different signals based on the sensing signal output from the output terminal N1 of the sensor pad 410 and is connected to the level shift detection unit. The level shift detection unit may include an analog-to-digital converter (ADC), a voltage to frequency converter (VFC), a flip-flop, a latch, a buffer, a TR, a TFT, A comparator, a digital to analog converter (DAC), an integrator, a differentiator, or the like, or a combination of these components. The level shift detection unit detects whether or not the touch is detected based on the voltage variation of the operational amplifier (OP-amp) output terminal N3 that varies depending on the touch capacitance.

Hereinafter, the operation of the touch detection apparatus 400 shown in Fig. 4 will be described.

First, the transistor Q is turned on to supply the charging signal Vb to charge the sensor pad 410 and the parasitic capacitance Cp. The touch capacitance Ct is charged by the charging signal Vb when the touch is generated in the sensor pad 410. Since the touch capacitance Ct does not exist when the touch pad 410 is not touch generated, the parasitic capacitance Cp Is charged. For convenience of description, all embodiments will be described on the assumption that the touch pad 410 has a touch capacitance Ct.

Thereafter, when the transistor Q is turned off, the charged charge is isolated. The input terminal N2 of the operational amplifier OP-map and the input terminal N3 of the analog-to-digital converter ADC are preferably formed to have a high impedance Hi-Z for stable isolation of charges, The potential at the output terminal N1 of the pad 410 can be kept constant. The state in which the charge is charged and isolated as described above is called a floating state. Thereafter, when a reference voltage Vref causing a voltage rise or a voltage drop is applied to the second input terminal of the operational amplifier OP-amp, the level of the output terminal N3 voltage of the operational amplifier OP- Or drop, which is referred to as "kick-back ".

According to the embodiment of the present invention, the touch sensing device 400 may include a first switch SW1 and a second switch SW2 having separate phases. Although only a simple switch is shown as an example of the switching device, in other embodiments, a three-terminal device such as a metal oxide semiconductor (MOS), a BJT, or a FET may be used. When a three-terminal device is used as the switching device, a control signal is applied so that a section in which the first switch SW is turned on and a section in which the second switch SW2 is turned on do not overlap each other . For example, the control signal input to the control terminal of the three-terminal device can be set such that the first switch is turned on in the low level interval and the second switch is turned on in the high level interval.

When the first switch SW1 is turned on and the second switch SW2 is kept off, the drive capacitance Cdrv is initialized and the initial charge amount is charged by the charge voltage Vb . On the other hand, the touch capacitance Ct and the parasitic capacitance Cp can be charged through the same charging voltage Vb by turning the transistor Q on. The voltage across the driving capacitance Cdrv becomes the difference between the high level voltage and the low level voltage of the reference voltage Vref applied to the input terminal N2 of the operational amplifier OP-amp, that is, VrefH-VrefL, And the voltage of the amplifier (OP-amp) output terminal N3 becomes the charging voltage Vb.

Assuming that the amount of charge charged in the touch capacitance Ct and the parasitic capacitance Cp is Q ₁ and the amount of charge in the drive capacitance Cdrv is Q ₂ and VdrvH-VdrvL is ΔVdrv, The formula for this is as follows. Here, the equation of Q = CV representing the charge conservation law is used.

On the other hand, when the second switch SW2 is turned on and the first switch SW1 is turned off, the charges charged in the touch capacitance Ct and the parasitic capacitance Cp are shared with the drive capacitance Cdrv. The charge amount is expressed by the following formula.

Here, Vo is the output terminal voltage of the operational amplifier OP-amp. The second amount of charge (Q) has a first switch (SW1), when only hayeoteul one touch capacitance (Ct) and the parasitic amount of charge (Q ₁₎ and the driving electrostatic charging of the electrostatic capacitance (Cp) of the time only hayeoteul on switch (SW2) Is equal to the sum of the amount of charge Q ₂ charged in the capacitor Cdrv, so that Q = Q ₁ + Q ₂ can be established. Substituting Equations (2) and (3) into Equation (4) yields Equation (4).

Cdrv DELTA Vref, which is common to both sides, is deleted, and the equation is expanded so that Vo remains on the left side.

The variation? Vo of the voltage at the output terminal N3 of the operational amplifier OP-amp becomes equal to the difference between the charging voltage Vb and the output voltage Vo. When the first switch SW1 is turned on, since the voltage of the output terminal N3 of the operational amplifier OP-amp is equal to the charging voltage Vb, the first switch SW1 is turned off, If the voltage of the operational amplifier (OP-amp) output terminal N3 is represented by Vo,? Vo = Vb-Vo. In Equation (5), (DELTA Verf-Vb) is a constant that takes a constant value of the voltage. Therefore, when the constant A is replaced with (A = DELTA Vref-Vb)

를 상수 B로 치환할 수 있다(B=

)The parasitic capacitance Cp, the drive electrostatic capacitance Cdrv, and A correspond to constants taking a constant value

Can be replaced with a constant B (B =

)

According to Equation (6), the variation? Vo of the output voltage of the operational amplifier (OP-amp) is proportional to the touch capacitance Ct. Accordingly, the relationship between the voltage variation of the operational amplifier (OP-amp) output terminal before and after the touch, that is, the level shift value? Vo and the touch capacitance Ct can be established. In addition, the output value of the analog-to-digital converter (ADC) receiving the level shift value? Vo is also linearly proportional to the touch capacitance Ct, thereby securing the linearity.

5 is a circuit diagram illustrating a touch detection apparatus according to another embodiment.

The circuit shown in Fig. 5 also includes a switch, which is the same as the circuit shown in Fig. 4, except that the first switch SW1 is connected between both ends N12 and N13 of the driving capacitance Cdrv. In the circuit diagram of Fig. 5, the difference between the operational amplifier (OP-amp) output voltage variations before and after the touch, that is, the level shift value? Vo, is linear with respect to the touch capacitance.

The first switch SW1 and the second switch SW2 are alternately turned on / off in the same manner as the embodiment shown in Fig. 5, when the output voltage Vo of the operational amplifier OP-amp is summarized using the charge conservation law (Q = CV), the output voltage Vo of the operational amplifier OP- The relationship can be derived.

)(here,

)

On the other hand, a method of controlling on / off of the first switch SW1 and the second switch SW2 in the above method is problematic.

The first switch SW1 and the second switch SW2 can be turned on / off for a predetermined time in the easiest manner. The first switch SW1 maintains the ON state for a minimum time period in which the touch capacitance Ct, the parasitic capacitance Cp and the drive capacitance Cdrv can be sufficiently charged, Lt; RTI ID = 0.0 > on < / RTI > state for a suitable period of time in which charged charges can be shared. For example, a method of measuring the impedance of the touch target node repeatedly and measuring the time constant tau in advance and determining a statistically optimized time interval may be used. However, this method has a problem that the optimized time can not be applied because it is only a method of selecting a time interval determined to be statistically safe. In addition, when the deviation between sensor pads is severe, the reliability of the statistics may be degraded. To compensate for this, the switching time of each switch should be set to be considerably larger than the optimum value. If the second switch SW2 is kept on for a longer time than the optimum time, the touch measurement node is connected to the external network for an unnecessary long time, thereby increasing the possibility of influx of external noise.

Therefore, in the present invention, it is desired to optimize the control of the switch operation.

6 is a circuit diagram illustrating a touch detection apparatus according to an embodiment of the present invention.

Referring to FIG. 6, it can be seen that the second switch control circuit 600 is added in the circuit diagram of FIG.

The second switch control circuit 600 includes a comparator 610 and a second switch control unit 620. The threshold voltage Vdc is input to the first input terminal of the comparator 610 and the connection node S of the second switch SW2 and the sensor pad 410 is input to the second input terminal of the comparator 610. [ That is, the comparator 610 continuously observes the voltage Vsens of the node S to which the second switch SW2 and the sensor pad 410 are connected. Meanwhile, the node S to which the second switch SW2 and the sensor pad 410 are connected is connected to the ground terminal through the first switch SW1.

Although FIG. 6 illustrates a mode in which the second switch control circuit 600 is added based on the circuit diagram of FIG. 5, the second switch control circuit 600 may be added in the circuit diagram of FIG. 4, a second switch control circuit (not shown) for controlling the operation of the second switch SW2 by observing the potential Vsens of the node S to which the second switch SW2 and the sensor pad 410 are connected 600 may be added equally.

Fig. 7 is a diagram illustrating the voltage waveform Vsens of the node S observed by the comparator in the circuit diagram shown in Fig. 6 and the opening and closing states of the switches SW1 and SW2.

6 and 7, the operation of the second switch control circuit 600 will be described below.

First, when the first switch SW1 is in the on state and the second switch SW2 is in the off state (T1 period), the transistor Q is turned on to turn on the touch capacitance Ct and the parasitic capacitance Cp, Is charged by the charging signal Vb. Although FIG. 6 illustrates the case where the charging signal Vb is supplied, the charging signal Vb may not be supplied. That is, the transistor Q connected to the output terminal N21 of the sensor pad 410 and the charging signal Vb applied through the transistor Q may be omitted. In this case, when the first switch SW1 is turned on, all the charges existing in the sensor pad 410 and the capacitances Ct and Cp connected thereto are discharged.

Since the observation node S of the comparator 610 is connected to the ground when the first switch SW1 is on, its potential Vsens is maintained at 0V. On the other hand, both ends of the driving electrostatic capacitance Cdrv are held on the same potential by the first switch SW1.

The process in which the charge signal is supplied to the electrostatic capacity or both ends of the electrostatic capacity are placed on the same potential and all of the charge is discharged will be referred to as "initialization process ". When the first switch SW1 is on, The capacitances Ct and Cp and the driving capacitance Cdrv connected to the sensor pad 410 are all initialized.

When the first switch SW1 is turned off and the second switch SW2 is turned on in the period T2, the charges charged in the touch capacitance Ct and the parasitic capacitance Cp become equal to the drive capacitance Cdrv Shared together. The transistor Q is also turned off and the supply of the charging signal Vb is interrupted. The drive capacitance Cdrv is not charged because the both ends N22 and N23 of the drive capacitance Cdrv are held on the same potential by the first switch SW1 in the T1 interval, The electric charge charged in the electrostatic capacitance Ct and the parasitic electrostatic capacitance Cp flows into the driving electrostatic capacity Cdrv. As a result, the voltage across the driving capacitance Cdrv rises and the potential Vsens of the observation node S also rises.

The comparator 610 continuously observes the potential Vsens of the observation node S with respect to the threshold voltage Vdc and when the potential Vsens of the observation node S rises, it is smaller than the first potential V1 And outputs a second signal when the first signal is higher than the first potential V1. Further, when the potential Vsens of the observation node falls, the third signal is outputted when it is larger than the second potential V2 and the fourth signal when the potential is lower than the second potential V2.

The first potential V1 and the second potential V2 may be identical in an ideal case, but may actually vary depending on the offset size of the comparator 610. [ The first potential V1 may be a value larger than the second potential V2. The second switch control unit 620 controls on / off of the second switch SW2 in accordance with the output signal of the comparator 610. [

The potential Vsens of the observation node S increases in the T2 interval and the comparator 610 outputs the first signal in a period lower than the first potential V1. The second switch control unit 620 keeps the second switch SW2 on in accordance with the first signal. The comparator 610 outputs the second signal when the potential Vsens of the observation node continuously rises and becomes equal to or higher than the first potential V1. The second switch control unit 620 switches the second switch SW2 to the OFF state based on the second signal (T3 section).

The potential Vsens of the observation node S due to the resistances existing in the touch capacitance Ct, the parasitic capacitance Ct and the peripheral conductor is changed to the potential Vsens at the time of the turn-off of the second switch SW2 . When the level at which the potential Vsens of the observation node falls is larger than the second potential V2, the third signal is outputted from the comparator 610. [ The second switch control unit 620 keeps the second switch SW2 in the OFF state based on the third signal. The falling of the potential Vsens of the observation node continues, and when the potential falls below the second potential V2, the comparator 610 outputs the fourth signal. The second switch control unit 620 switches the second switch SW2 to the ON state based on the fourth signal.

When the second switch SW2 is turned on, the potential Vsens of the observation node rises to the first potential V1 again (T4 section). This is because the driving electrostatic capacitance Cdrv is charged again by the reference copper voltage Vref. The potential Vsens of the observation node is maintained between the first potential V1 and the second potential V2 while repeating the same operation as the period from the period T3 to the period T4.

In FIG. 7, the first potential V1 is illustrated as being equal to the potential of the reference voltage Vref, but it may be selected as a potential smaller than the first potential V1. The smaller the first potential V1 is set, the shorter the T1 interval in Fig. 7 and the shorter the time that the second switch SW2 is maintained in the on state, thereby improving the speed of touch detection .

According to the embodiment of the present invention described with reference to FIGS. 6 and 7, the time for which the second switch SW2 is maintained in the ON state is shortened as compared with the method described with reference to FIGS. 4 and 5, Can be relatively small. Further, the open / close time of the second switch SW2 is automatically determined by the electrical condition, and it becomes unnecessary to store the open time and the like determined by a statistical method or the like, so that the size of the in-circuit storage device can be optimized do. However, as shown in FIG. 6, since the observation node S exists at a point connected to the sensor pad 410, that is, at an external point, there is also the aspect that perfect noise can not be blocked.

8 is a circuit diagram illustrating a touch detection apparatus according to another embodiment of the present invention.

Referring to FIG. 8, it can be seen that the circuit diagram is the same as that described with reference to FIG. 6 except that the position of the node observed by the comparator 810 of the second switch control circuit 800 is different.

Specifically, the comparator 810 of the second switch control circuit 800 according to another embodiment of the present invention may include a comparator 810 for comparing the driving capacitance Cdrv of the first node N32 and the node N32 of the operational amplifier OP- (S) is observed. The reference voltage Vref is input to the second input terminal of the operational amplifier OP-amp and the output terminal of the operational amplifier OP-amp is connected to the other terminal N33 of the driving capacitance Cdrv. same.

Although FIG. 8 illustrates a mode in which the second switch control circuit 800 is added based on the circuit diagram of FIG. 5, the second switch control circuit 800 may be added in the circuit diagram of FIG. That is, in the circuit diagram of FIG. 4, the second switch SW2 controls the operation of the second switch SW2 by observing the potential of the node S connected to one end of the driving capacitance Cdrv and the first input terminal of the operational amplifier OP- The switch control circuit 800 can be added equally.

9 is a waveform diagram for explaining the operation of the touch detection apparatus shown in Fig.

8 and 9, the operation of the touch detection apparatus according to another embodiment of the present invention will be described as follows.

First, the sensor pad 410 is initialized when the first switch SW1 is on and the second switch SW2 is off (T1 period). As described above, when the transistor Q is turned on so that the touch capacitance Ct and the parasitic capacitance Cp may be charged by the charging signal Vb and the charging signal Vb is not present, All of the charges present in the pad 410 and the capacitances Ct and Cp connected thereto may be discharged. The potential Vsens of the observation node connected to the first input terminal of the operational amplifier OP-amp is set to the reference potential Vref because the reference voltage Vref is input to the second input terminal of the operational amplifier OP- And remains at the same potential as the reference voltage Vref while being kept in the ON state.

A relatively large potential difference is generated across the second switch SW2 when the first switch SW1 is turned off and the second switch SW2 is switched from the off state to the on state. Since the operational amplifier OP-amp does not actually have an infinite gain, when the touch detection apparatus does not reach the steady state at the reference voltage Vref, the potential Vsens of the observation node becomes It can be instantly dropped and then recovered again. Therefore, if the potential Vsens of the observation node is instantaneously changed when the second switch SW2 is repeatedly opened and closed, it can be seen that the touch detection apparatus has not reached the steady state of the reference voltage Vref.

A threshold voltage Vdc is input to the first input terminal of the comparator 810 and a second input terminal is connected to the observation node S. [ The comparator 810 compares the threshold voltage Vdc with the observation node potential Vsens and the threshold voltage Vdc may be set to a voltage lower than or equal to the reference voltage Vref. In FIG. 9, the case where the threshold voltage Vdc is equal to the reference voltage Vref is exemplified.

The comparator 810 outputs a first signal when the threshold voltage Vdc and the observation node potential Vsens differ by more than a threshold value and the second switch control unit 820 receives the signal to receive the second switch SW2 (T3 section). When the second switch SW2 is repeatedly opened and closed, the touch detection device reaches the steady state of the reference voltage Vref. In this state, even if the second switch SW2 is repeatedly opened and closed, the difference between the threshold voltage Vdc input to the comparator 810 and the observation node potential Vsens falls below the threshold value. The comparator 810 outputs a second signal when the difference between the threshold voltage Vdc and the observation node potential Vsens is less than the threshold value and the second switch control unit 820 receives the signal and receives the signal to the second switch SW Thereby stopping the opening / closing repetitive operation and maintaining the OFF state (T4 section).

Referring to FIG. 9, it can be seen that the interval (T2 interval) during which the second switch SW2 is first turned on is relatively long. This is because the touch sensing device can be charged to some extent . However, it is not necessary to set the charging time.

According to the embodiment described with reference to FIGS. 8 and 9, since the observation node S of the comparator 810 is not connected to the outside, the influence on the noise can be further reduced.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

600, 800: Second switch control circuit
610, 810: comparator
620, 820: a second switch control section

Claims (15)

A sensor pad for outputting a sensing signal according to a touch state in response to a reference voltage after the initialization process;
An operational amplifier having a first input connected to the sensor pad and a second input receiving the reference voltage and outputting different signals in response to the sensing signal;
A first switch for controlling a potential at both ends of a driving capacitance connected between a first input terminal and an output terminal of the operational amplifier;
A second switch which is alternately turned on and off with respect to the first switch and switches connection between the sensor pad and the first input terminal of the operational amplifier; And
And a second switch control circuit for controlling on / off of the second switch based on the sensing signal. The method according to claim 1,
And the second switch control circuit controls the on / off state of the second switch based on the potential of the first node connected to the sensor pad and the second switch or the first node of the operational amplifier and the second node connected to the drive capacitance, OFF of the touch detection device. The method according to claim 1,
The second switch control circuit includes:
A comparator for comparing a threshold voltage with the sensing signal and outputting a first signal when the sensing signal is higher than the first potential and outputting a second signal when the sensing signal is lower than the second potential; And
And a second switch control section for turning off the second switch in response to the first signal and controlling the second switch to be turned on in response to the second signal. The method of claim 3,
Wherein the first potential is a potential lower than the reference voltage and the second potential is lower than the first potential. The method according to claim 1,
The second switch control circuit includes:
A comparator comparing the threshold voltage with the sensing signal and outputting a first signal when the potential fluctuation width of the sensing signal is equal to or greater than a threshold value and outputting a second signal when the potential fluctuation width of the sensing signal is less than a threshold value; And
And a second switch control section for controlling the second switch so as to repeatedly open and close in response to the first signal and to control the second switch to remain in the OFF state in response to the second signal. 6. The method of claim 5,
Wherein the threshold voltage is equal to or lower than the reference voltage. The method according to claim 1,
Further comprising a level shift detecting section for detecting whether or not a touch is made based on a voltage variation at the output terminal of the operational amplifier according to the reference voltage. Initializing a driving capacitance in which connection between the sensor pad and the sensor pad is switched;
Coupling the sensor pad coupled to the first input of the operational amplifier to the driving capacitance; And
And switching the connection between the sensor pad and the driving capacitance based on a sensing signal output from the sensor pad in response to a reference voltage applied to a second input of the operational amplifier. 9. The method of claim 8,
Wherein the switching control step includes switching control of connection between the sensor pad and the driving capacitance based on an output terminal potential of the sensor pad or a potential of the first input terminal. 9. The method of claim 8,
Wherein the switching control step comprises:
And comparing the sensed signal with the threshold voltage to disconnect and connect the sensor pad and the driving capacitance when the sensing signal is greater than or equal to the first potential or when the sensing signal is less than the second potential, Way. 11. The method of claim 10,
Wherein the first potential is a potential lower than the potential of the reference voltage, and the second potential is lower than the first potential. 9. The method of claim 8,
Wherein the switching control step comprises:
Comparing the threshold voltage with the sensing signal and repeating the connection and disconnection between the sensor pad and the driving electrostatic capacitance when the potential fluctuation width of the sensing signal is equal to or greater than the threshold value, and when the potential fluctuation width of the sensing signal is less than the threshold value, And maintaining an interruption between the sensor pad and the drive capacitance. 13. The method of claim 12,
Wherein the threshold voltage is equal to or less than the reference voltage. 9. The method of claim 8,
Further comprising the step of detecting whether or not the touch is based on the voltage variation at the output of the operational amplifier according to the reference voltage. A sensor pad forming a touch capacitance in relation to the touch input tool;
A first switch connected between the sensor pad and the ground terminal, the first switch being ON only in the process of initializing the sensor pad;
An operational amplifier having a first input terminal receiving a sensing signal output from the sensor pad and a second input terminal receiving a reference voltage based on the touch capacitance and outputting a touch detection signal;
A driving electrostatic capacitance connected between the first input terminal and the output terminal of the operational amplifier;
A second switch connected to both ends of the driving capacitance, the second switch being ON only while the sensor pad is being charged;
A third switch connected between the sensor pad and a first input terminal of the operational amplifier, the third switch being alternately turned on and off with respect to the first switch and the second switch; And
And a third switch control unit for comparing the sensing signal with a preset threshold voltage to control on / off of the third switch.

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