KR20090000532A - A device and method for driving a touchpad - Google Patents

Abstract

A device and a method for driving a touch pad to prevent wrongly read a touch is provided to improve quality of a driving chip by outputting the same number of output from a comparator when the same touch signal information is received even if a capacitance change occurs in a capacitor by process allowance. A first capacitor charges electric charge received according to a touch of a touch pad(202). A first switch(201) is connected between the first capacitor and a voltage source, and charges the electric charge to the first capacitor. A second switch(203) is connected between the first capacitor and the second capacitor, and controls amount of electric charge charged in the second capacitor. A discharge circuit(206) is connected to the second capacitor, and receives the electric charge discharged from the second capacitor. A comparator(207) is connected to the second capacitor, and determines a low/high state according to the amount of the electric charge charged in the second capacitor. A latch(208) stores output of the comparator. A counter(209) counts the number of the low/high state of the output received from the latch. A compensating circuit is connected between the counter and the second capacitor, and compensates capacitance of the second capacitor(205).

Description

Touch pad driving device and driving method {A device and method for driving a touchpad}

1 is a circuit diagram of a touch pad driving apparatus according to the prior art.

2 is a circuit diagram of a touch pad driving apparatus in which capacitance is compensated according to a first embodiment of the present invention.

3 is a circuit diagram of a touch pad driving apparatus in which capacitance is compensated according to a second embodiment of the present invention.

4 is a diagram illustrating a capacitance compensator including a capacitor and a transistor according to an embodiment of the present invention.

5 is a view showing a change in the amount of charge according to the operation period of the first capacitor and the second capacitor according to an embodiment of the present invention.

※ Explanation of code about main part of drawing ※

100, 200, 300: voltage source

101, 201, 301: first switch

102, 202, and 302: first capacitor

103, 203, 303: second switch

104, 204, 304: second capacitor

205 and 305: capacitance compensation unit

106, 206, 306: discharge circuit

107, 207, 307: comparators

108, 208, 308: latch

109, 209, 309: counting part

210, 310: low / high number comparators

211: memory

311: Compensation capacitance determiner

The present invention relates to a touch pad driving apparatus and a driving method, and more particularly, to a touch pad driving integrated circuit having a capacitance compensator for constantly compensating for capacitance in order to prevent misreading of touch due to a change in capacitance. The structure and method of operation thereof.

In general, the touch pad includes a cathode ray tube (CRT), a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescent device (Electro). It is a computer peripheral device installed on a display surface of a display device such as a luminescence device (LCD) and the like, and a user presses a touch panel while looking at the display device to input predetermined information into a computer.

In order to efficiently use various electronic devices, a touch pad for inputting a signal on a display surface of a display device without a remote controller or a separate input device is widely used. That is, a touch pad is provided on the display surface of an electronic notebook, a flat panel display device such as an LCD, a PDP, an EL, and an image display device such as a CRT. Accordingly, when the user presses the surface with a pen or finger on the screen of the image display device, information corresponding to the position is input.

The touch pad may be classified into a resistive type, a capacitive type, an electro-magnetic type, and the like according to a method of sensing a touch.

The basic structure of the capacitive touch pad of the above touch pad is to install a film with a transparent electrode on the liquid crystal panel and to apply a voltage to each corner or corner of the film to generate a uniform electric field on the transparent electrode finger Alternatively, when the conductive stylus contacts, the voltage drop occurs to find the position coordinate.

In general, the semiconductor chip for driving a touch pad reads an amount of charge transferred according to whether the touch pad is touched, and reads whether a specific terminal of the touch pad is touched, and processes data accordingly.

The conventional touch pad driving apparatus will be described with reference to the accompanying drawings.

1 is a circuit diagram of a touch pad driving apparatus used in a conventional touch pad as described above. As shown in FIG. 1, a conventional touch pad driving apparatus includes a capacitor 102 that charges a charge transferred according to whether a touch pad is touched, and a capacitor 104 connected in parallel with the capacitor. These capacitors 102 and 104 are controlled by the amount of charge charged according to the on / off of the switches 101 and 103 connected to each of them.

In addition, in the circuit configuration of the conventional driving apparatus shown in FIG. 1, the discharge circuit 106 in which the charge charged in the capacitor 104 is discharged, the comparator 107 connected to the discharge circuit 106, and the The latch unit 108 connected to the comparator 107 and the counting unit 109 connected to the latch unit 108 are also provided.

The conventional touch pad driving device having the circuit configuration as described above operates as follows.

When a specific terminal of the touch pad is touched, the switch 101 connected to the voltage source 100 is shorted to charge the touch pad with the capacitor 102. Thereafter, another switch 103 connected between the capacitor 102 and the capacitor 104 connected in parallel repeats the short-circuit and the open. If the switch 103 is short-circuited, the capacitor 104 Charge).

In this state in which the capacitor 104 is charged, the comparator 107 determines high / low. After the reading is completed, the electric charge charged in the capacitor 104 is discharged through the discharge circuit 106.

After the switch 103 is first shorted / opened, the charge stored in the capacitor 102 is reduced by the charge charged in the capacitor 104 rather than the charge in the initial state. After that, the switch 103 is short-circuited and the discharged capacitor 104 is charged with the charge of the capacitor 102, and the comparator 107 determines the voltage of the capacitor 104 in the charged state to determine the high / low again. do.

At this time, when the charges of the capacitor 102 are all discharged and there is no more amount to charge the capacitor 104, the comparator 107 outputs a low value thereafter. That is, the more charges are charged, the higher the number of highs output from the comparator 107 within a predetermined time. That is, since the high number of output values of the comparator 107 means the amount of charges of the capacitor 102, when the high number of output values of the comparator 107 becomes larger than a predetermined reference number, it means whether the touch pad is touched.

However, since the capacitance Cs of the capacitor 104 varies according to the semiconductor device process, even if the chip is composed of the same designed circuit, this value will change according to the process, and the high number of comparator output values will change even in the same touch signal. . In this way, even if the same touch input is input to the touch pad, different high numbers are transmitted to the display panel, which causes malfunction.

The object of the present invention is to overcome this problem. Specifically, the present invention provides the same number of outputs in a comparator when the same touch signal information is input even when a capacitance change of a capacitor occurs due to process variation. The aim is to improve the quality of.

That is, the present invention is a drive having a touch pad driving circuit that can maintain the capacitance of the comparator for each chip to compensate the capacitance of the comparator chip so that the same number of comparator high output value can be output for the information of the same touch pad It is an object to provide an apparatus and a driving method.

The present invention for achieving the above object relates to a touch pad driving apparatus and a driving method, and more particularly, a touch having a touch pad driving circuit that can be consistently maintained in process variation by compensating the capacitance for each chip A pad drive device and a drive method are provided.

Specifically, the touch pad driving device according to the present invention includes a first capacitor that charges a charge transferred according to whether the touch pad is touched; A first switch connected between the first capacitor and a voltage source and configured to charge electric charges to the first capacitor; A second capacitor connected to the first capacitor; A second switch connected between the first capacitor and the second capacitor and controlling an amount of electric charge charged in the second capacitor; A discharge circuit connected to the second capacitor and discharging charges from the second capacitor; A comparator coupled to the second capacitor and discriminating a low / high according to an amount of electric charge charged in the second capacitor; A latch unit connected to the comparator and storing the comparator output; A counting unit connected to the latch unit and counting a low / high number of outputs from the latch unit; And a compensation circuit connected between the counting unit and the second capacitor and compensating for the capacitance of the second capacitor, wherein the second switch repeats a short / open.

The present invention also relates to a method for driving a touch pad, comprising: charging a first capacitor with charges transferred according to whether a touch pad is touched; Charging a charge to the first capacitor by a first switch connected between the first capacitor and a voltage source; Controlling an amount of electric charge charged in the second capacitor by a second switch connected between the first capacitor and a second capacitor connected to the first capacitor; Discharging charge from the second capacitor in a discharge circuit connected to the second capacitor; Determining low / high according to the amount of charge charged in the second capacitor in a comparator connected to the discharge circuit; Storing the comparator output in a latch unit connected to the comparator; Counting a low / high number of outputs from the latch unit in a counting unit connected to the latch unit; And compensating for capacitance of the second capacitor in a compensation circuit connected between the counting unit and the second capacitor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited by the following examples.

2 is a circuit diagram of a touch pad driving apparatus in which capacitance is compensated according to a first embodiment of the present invention. As shown in FIG. 2, in the first embodiment of the present invention, the touch pad driving circuit includes a first capacitor 202 and a second capacitor 204, which are connected in parallel, respectively, and the capacitors 202 and 204. The first switch 201 and the second switch 203 which are connected to each other to control the operation of each capacitor have a configuration.

In addition, a discharge circuit 206 for discharging the charge charged in the second capacitor 204, a comparator 207 connected to the second capacitor 204, and a latch unit 208 connected to the comparator 207. In addition, a counting unit 209 connected to the latch unit 208 and a compensation circuit for compensating the capacitance of the second capacitor 204 are also provided.

According to an exemplary embodiment of the present disclosure, the compensation circuit may include: a low / high number comparator 210 for comparing the low / high number and the reference low / high number output from the counting unit 209; A memory unit 211 receiving a comparison result of the low / high number comparator 210 and outputting data corresponding to a capacitance compensation value accordingly; And a capacitance compensator 205 for compensating capacitance according to the output of the memory unit.

According to an embodiment of the present disclosure, the discharge circuit 206 may be configured as a transistor switch. In addition, the memory unit 211 may be a nonvolatile memory, and the capacitance compensation unit 205 may have a configuration in which a plurality of capacitors connected in series with a transistor are arranged in a parallel structure.

The operation method of each component of the driving apparatus according to the first embodiment of the present invention having the configuration as described above will now be described in detail.

First, when the touch terminal is touched, the voltage source 200 is charged as in the prior art, and is charged to the first capacitor 202 through the first switch 201. Thereafter, the second capacitor 204 is charged through the second switch 203 which repeats open / short at equal intervals.

After the short circuit of the second switch 203, the comparator 207 determines the potential of the node between the second capacitor 204 and the comparator 207 by comparing with the reference voltage Vref. Output a high value.

After the sensing of the comparator 207 is finished, the charge of the second capacitor 204 is discharged through the discharge circuit 206, and when the second switch 203 is shorted again, the second capacitor 204 is charged. do.

As described above, as the charging / discharging process of the second capacitor 204 is repeated while being synchronized with the repetition process of the opening / shorting of the second switch 302, all of the charges of the first capacitor 202 are stored in the second capacitor ( The output of comparator 207 outputs high values until it is charged and discharged to 204.

At this time, the capacitance Cs (~ 1pF) of the second capacitor 204 is very small compared to the amount of charge charged in the capacitance Cx (2-50pF) or the voltage source 200 (Vs) of the first capacitor 202. Accordingly, the capacitance is also changed, and even the same touch information may change in the high output value of the comparator 207 according to the change of the Cs value so that the displayed image information may be different. As such, in order to compensate for the capacitance Cs value of the second capacitor 204 according to the process change, the present invention provides the following structure and operation method.

There is a reference charge charging unit for charging the reference charge to the first capacitor 202, and the reference charge charging unit charges the first capacitor 202 at the beginning of the driving device operation. Thereafter, while the open / short of the second switch 203 is repeated, the comparator 207 compares the potential of the node between the second capacitor 204 and the comparator 207 with the reference voltage Vref and outputs a high / low output value. Repeatedly print

The counting unit 209 counts the number of highs or lows output at this time. In this case, since the first capacitor 202 is charged with the same reference charge, the same designed chip should output the same number of high output numbers.

Accordingly, the low / high number comparator 210 compares the low / high output number output from the counting unit 209 with the reference low / high number. When the number of high outputs is smaller than the reference number, the second capacitor ( The capacitance Cs of 204 means larger than an expected value, and if the number of highs is larger than the reference number, Cs means smaller than a desired value.

According to the capacitance read result of the low / high number comparator 210, the memory unit 211 outputs data corresponding to the capacitance compensation value, and the capacitance compensator 205 according to the output of the memory unit 211 is provided. It serves to increase the size of the capacitance, or to reduce the size of the capacitance.

Therefore, the size of Cs is always kept constant for each chip regardless of the process change, thereby outputting the same high output number for the same touch signal, thereby preventing malfunction.

3 is a circuit diagram of a touch pad driving apparatus in which capacitance is compensated according to a second embodiment of the present invention. As shown in Fig. 3, the circuit diagram configuration of the second embodiment of the present invention is similar to the circuit diagram configuration of the first embodiment of the present invention shown in Fig. 2, and similar to that of the memory section 211 of Fig. A function, that is, a compensation capacitance determiner 311 which performs a role of determining a capacitance to be compensated for, has been configured, and the operating method of the entire driving apparatus is also the same as described above through the first embodiment of the present invention.

4 is a diagram illustrating a capacitance compensator including a capacitor and a transistor according to an embodiment of the present invention. As shown in FIG. 4, the capacitance compensation unit has a configuration in which a plurality of transistors connected in series with the transistors are arranged in a parallel structure.

5 is a view showing a change in the amount of charge according to the operation period of the first capacitor and the second capacitor according to an embodiment of the present invention. In the graph of FIG. 5, the lower portion of the two curves representing the state change represents the change in the charge amount of the first capacitor, and the upper portion represents the change in the charge amount of the second capacitor.

As described above, charge is charged to the first capacitor through the first switch, and charge is charged to the second capacitor 204 through the second switch repeating the opening / shorting at equal intervals. The change in charge amount as the charge / discharge process of the second capacitor is repeated while being synchronized with the repetition process of the opening / shorting of the second switch is shown through the change in the upper curve of FIG. 5 graph, and the charges of the first capacitor are all The change in the amount of charge until charged and discharged with the two capacitors is shown through the change in the lower part of the graph of FIG. 5.

The present invention has a touch pad driving circuit that compensates the capacitance of a comparator used to read information on a touch panel so that the same number of high outputs are output for the same touch signal, so that the capacitance can be kept constant even with process changes. By providing the touch pad driving device and the driving method, the reliability of the touch pad driving can be improved.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the technical field of the present invention without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

Claims (13)

A first capacitor configured to charge electric charges transferred according to whether the touch pad is touched; A second capacitor connected to the first capacitor; A comparator coupled to the second capacitor, the comparator determining a low / high according to an amount of charge charged in the second capacitor; A counting unit counting a low / high number of the comparator outputs; And And a compensation circuit connected between the counting unit and the second capacitor and compensating for capacitance of the second capacitor. The method of claim 1, A first switch connected between the first capacitor and a voltage source and configured to charge electric charges to the first capacitor; A second switch connected between the first capacitor and the second capacitor and controlling an amount of electric charge charged in the second capacitor; A discharge circuit connected to the second capacitor and discharging charges from the second capacitor; And And a latch unit connected to the comparator and storing the comparator output. The method according to claim 1 or 2, The compensation circuit, A low / high number comparator for comparing the low / high number output from the counting unit with a reference low / high number; A memory unit receiving a comparison result of the low / high number comparator and outputting data corresponding to a capacitance compensation value accordingly; And And a capacitance compensator for compensating capacitance according to the output of the memory unit. The method according to claim 1 or 2, The compensation circuit, A low / high number comparator for comparing the low / high number output from the counting unit with a reference low / high number; A compensation capacitance determiner which receives a comparison result of the low / high number comparator and outputs data corresponding to a capacitance compensation value accordingly; And And a capacitance compensator for compensating capacitance according to the output of the compensation capacitance determiner. The method of claim 1, And the first capacitor and the second capacitor are connected in parallel. The method of claim 2, And the discharge circuit is a transistor switch. The method of claim 3, And the memory unit is a nonvolatile memory. The method of claim 3, The capacitance compensation unit is a touch pad driving device, characterized in that a plurality of capacitors connected in series with the transistor are arranged in a parallel structure. The method of claim 4, wherein The capacitance compensation unit is a touch pad driving device, characterized in that a plurality of capacitors connected in series with the transistor are arranged in a parallel structure. Charging a charge to the second capacitor by turning on a second switch connected between a first capacitor and a second capacitor connected to the first capacitor; Determining low / high according to the amount of charge charged in the second capacitor in a comparator connected to the second capacitor; Storing the comparator output in a latch unit connected to the comparator; Counting a low / high number of outputs from the latch unit in a counting unit connected to the latch unit; And Compensating for the capacitance of the second capacitor in a compensation circuit connected between the counting unit and the second capacitor. The method of claim 10, Charging the first capacitor with charges transferred according to whether the touch pad is touched; And Discharging charge from the second capacitor in a discharge circuit connected to the second capacitor, And alternately charging and comparing voltages at a node to which the second capacitor is connected while the second switch is repeatedly shorted / opened. The method according to claim 10 or 11, wherein Compensating step, Comparing, in a low / high number comparator, a low / high number and a reference low / high number output from the counting unit; Receiving a comparison result of the low / high number comparator in a memory unit and outputting data corresponding to a capacitance compensation value accordingly; And Compensating the capacitance in accordance with the output of the memory unit in the capacitance compensation unit; operation method of the touch pad driving apparatus. The method according to claim 10 or 11, wherein Compensating step, Comparing, in a low / high number comparator, a low / high number and a reference low / high number output from the counting unit; Receiving a comparison result of the low / high number comparator from a compensation capacitance determiner and outputting data corresponding to a capacitance compensation value accordingly; And Compensating the capacitance in accordance with the output of the memory unit in the capacitance compensation unit; operation method of the touch pad driving apparatus.

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