KR101343572B1 - Touch sensing circuit and touch sensing system having the same - Google Patents

Abstract

A touch sensing circuit is disclosed. The touch sensing circuit includes a first input terminal for receiving a charged voltage, a second input terminal for receiving a reference voltage, and an output terminal for outputting a comparison signal corresponding to a comparison result of the charged voltage and the reference voltage. A comparator configured to select one of the plurality of first capacitors in response to the selection signal, and to generate the charged voltage, a first current supplied to the one selected capacitor according to a first control code. A first current controller to generate, a first switch connected between the first current controller and the first input terminal, and a second switch and resistor connected in series between the first input terminal and ground.

Description

Touch sensing circuit and touch sensing system including the same {Touch sensing circuit and touch sensing system having the same}

An embodiment according to the concept of the present invention relates to a touch sensing system, and more particularly, to a touch sensing circuit capable of sensing a change in capacitance and a touch sensing system including the same.

The touch sensor is a device capable of detecting whether the touch sensor array is in contact.

The touch sensor uses capacitance to detect whether the touch sensor array is in contact. The capacitance refers to the ability of a capacitor to store energy in an electric field.

The touch sensor array includes touch sensor components each having two conductor plates.

When a conductive object (eg, a conductive pen such as a human finger or a stylus) approaches the touch sensor array, the capacitance between two conductor plates of either one of the touch sensor components changes. The touch sensor may detect whether the conductive object contacts the sensor by using the change in capacitance.

Therefore, a touch sensing circuit for accurately detecting the change in capacitance is needed.

The technical problem to be achieved by the present invention is to provide a touch sensing circuit and a touch sensing system including the same that can detect a change in capacitance.

The touch sensing circuit according to an exemplary embodiment of the present invention provides a first input terminal for receiving a charged voltage, a second input terminal for receiving a reference voltage, and a comparison signal corresponding to a comparison result of the charged voltage and the reference voltage. A comparator including an output terminal for outputting, a selector for selecting any one of a plurality of capacitors in response to a selection signal, and supplied to the selected one capacitor according to a first control code to generate the charged voltage A first current controller for generating a first current, a first switch connected between the first current controller and the first input terminal, and a second switch and resistor connected in series between the first input terminal and ground; Include.

According to an embodiment, the touch sensing circuit generates a second current supplied to one of the selected capacitors according to a second control code to generate the charged voltage, and the second current. The apparatus may further include a third switch connected between the controller and the first input terminal.

In some embodiments, the touch sensing circuit may further include a switched capacitor array including a plurality of internal capacitors and a plurality of switches. The switched capacitor array is connected between the first input terminal and ground.

According to an embodiment, the touch sensing circuit may further include a digital to analog converter that generates the reference voltage according to a third control code.

The first control code, the second control code, the third control code, and the selection signal are generated by a micro control unit.

The comparator outputs the comparison signal having a high level when the charged voltage is greater than the reference voltage, and the comparison having a low level when the charged voltage is less than the reference voltage. Output the signal.

The first switch and the second switch are complementary to each other.

The first switch is turned on before the third switch.

The touch sensing system according to an exemplary embodiment of the present invention includes a touch sensor array including a plurality of capacitors, a micro control unit generating a first control code and a selection signal, and the touch sensing circuit.

The micro control unit generates the first control code, the second control code, and the third control code according to the comparison signal.

The touch sensing circuit and the touch sensing system including the same according to an embodiment of the present invention have the effect of detecting a change in capacitance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully understand the drawings recited in the detailed description of the present invention, a detailed description of each drawing is provided.
1 is a block diagram of a touch sensing system according to an exemplary embodiment of the present invention.
FIG. 2 is a block diagram of the touch sensing circuit shown in FIG. 1.
3 is a timing diagram illustrating a sensing operation of the touch sensing circuit shown in FIG. 2.
4 is a flowchart illustrating a method of operating the touch sensing circuit of FIG. 2.

It is to be understood that the specific structural or functional descriptions of embodiments of the present invention disclosed herein are only for the purpose of illustrating embodiments of the inventive concept, But may be embodied in many different forms and is not limited to the embodiments set forth herein.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are intended to distinguish one element from another, for example, without departing from the scope of the invention in accordance with the concepts of the present invention, the first element may be termed the second element, The second component may also be referred to as a first component.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "comprises ", or" having ", or the like, specify that there is a stated feature, number, step, operation, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings.

1 is a block diagram of a touch sensing system according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a touch sensing system 10 includes a touch sensor array 11 and a touch sensor 20.

The touch sensing system 10 may be implemented as a mobile phone, a mobile device, a tablet PC, an MP3 player, a touch screen, or a touch key.

The touch sensor array 11 includes a plurality of touch sensor elements 11-1-11-m; m is a natural number.

The touch sensor 20 is a device capable of detecting whether the touch sensor array 11 is in contact.

The touch sensor 20 includes a touch sensing circuit 30, a micro control unit (MCU) 50, and a memory 60.

The touch sensing circuit 30 will be described in detail with reference to FIG. 2.

The micro control unit 50 communicates with the touch sensing circuit 30 and the memory 60.

The memory 60 stores the instructions performed by the micro control unit 50. The memory 60 may be implemented as a nonvolatile memory such as flash or a volatile memory such as dynamic random access memory (DRAM).

The touch sensor 20 may be implemented as one integrated circuit.

FIG. 2 is a block diagram of the touch sensing circuit shown in FIG. 1.

1 and 2, each of the plurality of touch sensor components 11-1-11-m has two conductor plates.

The capacitance between the two conductor plates of the plurality of touch sensor components 11-1 to 11-m may be represented by a plurality of capacitors C1 to Cm.

The touch sensing circuit 30 includes a comparator 31, a selector 33, and a first current controller 35, a first switch 37, and a first connected in series between the first input terminal ND1 and ground. 2 includes a switch 39 and a resistor (R).

The comparator 31 includes a first input terminal ND1 for receiving the charged voltage Vs, a second input terminal ND2 for receiving the reference voltage Vr, and a charged voltage Vs and a reference voltage Vr. Output terminal ND3 for outputting a comparison signal OUT corresponding to the comparison result.

The comparator 31 outputs a comparison signal OUT having a high level when the charged voltage Vs is greater than the reference voltage Vr.

The comparator 31 outputs a comparison signal OUT having a low level when the charged voltage Vs is smaller than the reference voltage Vr.

The selector 33 selects any one of the capacitors C1 to Cm in response to the selection signal SS.

The selection signal SS is generated by the MCU 50.

The first current controller 35 generates a first current I1 supplied to any one capacitor (eg, C1) selected according to the first control code CD1 to generate the charged voltage Vs. . The first control code CD1 includes a plurality of bits and is received from the MCU 50.

For example, when the first control code CD1 is 3 bits, each time the bits of the first control code CD1 are increased by one, the first current controller 35 receives the first current I1 increased by 1 mA. Create

This is summarized in Table 1.

CD1 I1 000 0㎂ 001 1㎂ 010 2㎂ 011 3㎂ 100 4㎂ 101 5㎂ 110 6㎂ 111 7㎂

The first switch 37 is connected between the first current controller 35 and the first input terminal ND1.

The first switch 37 is controlled by the first switching signal SWC, and the second switch 39 is controlled by the second switching signal SWS. The plurality of switching signals SWC and SWS are signals output from the MCU 50.

When the first switch 37 is turned on and the second switch 39 is turned off, the first current I1 generated by the first current controller 35 is supplied to the capacitor C1, and the capacitor (C1) is charged.

According to an embodiment, the touch sensing circuit 30 may further include a second current controller 41 and a third switch 43.

The second current controller 41 generates a second current I2 supplied to any one capacitor (eg, C1) selected according to the second control code CD2 to generate the charged voltage Vs. . The second control code CD2 includes a plurality of bits, and the second control code CD2 is received from the MCU 50.

The second current I2 has a lower current range than the first current.

For example, when the second control code CD2 is 3 bits, whenever the bits of the second control code CD2 are increased by one, the second current controller 41 receives the second current I2 increased by 0.125 mA. Create

Table 2 summarizes these.

CD2 I2 000 0.000㎂ 001 0.125㎂ 010 0.250㎂ 011 0.375㎂ 100 0.500㎂ 101 0.625㎂ 110 0.750㎂

The third switch 43 is connected between the second current controller 41 and the first input terminal ND1.

According to an embodiment, the touch sensing circuit 30 may include a switched capacitor array 45 including a plurality of internal capacitors Ci1 to Cin (n is a natural number) and a plurality of switches SW1 to SWn. It may further include.

Each of the switches SW1 to SWn may be controlled by a signal output from the MCU 50.

The switched capacitor array 45 is connected between the first input terminal ND1 and ground. The switched capacitor array 45 is used to verify the sensing sensitivity of the touch sensing circuit 30.

According to an embodiment, the touch sensing circuit 30 may further include a digital analog converter 47 generating the reference voltage according to the third control code CD3. The third control code CD3 is received from the MCU 50.

 3 is a timing diagram illustrating a sensing operation of the touch sensing circuit shown in FIG. 2. The x-axis represents time and the y-axis represents voltage.

2 and 3, the sensing operation of the touch sensing circuit 30 may be divided into three sections.

The first section T1 is a charging operation.

When the first switch 37 or the third switch 43 is turned on and the second switch 39 is turned off, any one of the plurality of capacitors C1 to Cm selected by the selection signal SS (Eg, C1) is charged, which is defined as a charging operation.

The second section T2 is a voltage holding operation.

When the first switch 37 or the third switch 43 is turned off and the second switch 39 is turned off, any one of the plurality of capacitors C1 to Cm selected by the selection signal SS is turned on. For example, C1 maintains the charged voltage Vs, which is defined as a voltage holding operation.

At this time, the comparator 31 compares the charged voltage Vs with the reference voltage Vr and outputs a comparison signal OUT corresponding to the comparison result.

The third section T3 is a discharge operation.

When the first switch 37 or the third switch 43 is turned off and the second switch 39 is turned on, any one of the plurality of capacitors C1 to Cm selected by the selection signal SS ( For example, C1) is discharged, which is defined as a discharge operation.

Table 3 summarizes these.

First switch 37 or third switch 43 Second switch (39) Charging operation Turn on Turn off Voltage hold operation Turn off Turn off Discharge operation Turn off Turn on

4 is a flowchart illustrating a method of operating the touch sensing circuit of FIG. 2.

1 to 4, the touch sensing circuit 30 is set up (S10).

For example, the bits of the first control code CD1 are set to 001, the time Tc is set to 1 ms, and the reference voltage Vr is set to 1V.

A coarse scan operation on the current is performed (S20).

The coarse scan for the current is the output signal of the comparator 31 when the capacitance of any one of the plurality of touch sensor elements 11-1 to 11-m selected by the selection signal SS is unknown. The process of searching for the first current I1 at which OUT) becomes high for the first time.

For example, when the bits of the first control code CD1 are 001, the first current I1 generated by the first current controller 35 is 1 mA.

The capacitor C1 selected by the selection signal SS is charged according to the first current I1. At this time, the first switch 37 is turned on, and the second switch 39 is turned off.

The comparator 31 compares the voltage Vs charged by the first current I1 with the reference voltage Vr and outputs a comparison signal OUT. At this time, both the first switch 37 and the second switch 39 are turned off.

When the comparison signal OUT has a low level, the MCU 50 performs a first bit increasing operation of increasing the first control code CD1 by one bit. Accordingly, the first current controller 35 generates an increased first current I1 according to the first control code CD1 having one bit increased. For example, the first current I1 is 2 mA.

A first charging operation for charging the capacitor C1 is performed according to the first current I1.

The comparator 31 compares the voltage Vs charged by the first current I1 with the reference voltage Vr, and outputs a comparison signal OUT corresponding to the comparison result.

The first bit increment operation, the first charging operation, and the first comparison operation are repeatedly performed until the comparison signal OUT has a high level for the first time.

For example, assuming that the comparison signal OUT first has a high level when the first control code CD1 is 110, the value of the coarse scan for the current is 101, which is a bit value of the first control code CD1.

According to an embodiment, a redundancy check operation may be performed to check whether a coarse scan value for the current is valid (S30).

The digital-to-analog converter 47 adjusts the reference voltage Vr, and the comparator 31 compares the adjusted reference voltage Vr with the charged voltage Vs and outputs a comparison signal OUT corresponding to the comparison result. do.

The digital analog converter 47 may adjust the reference voltage Vr according to the third control code CD3.

For example, the digital to analog converter 47 may adjust the reference voltage Vr from 1V to 1.05V or 0.95V according to the third control code CD3.

Assume that the value of the coarse scan for the current ranges between 101 and 110.

When the coarse scan value is 101, the comparator 31 compares the charged voltage Vs with the adjusted reference voltage (for example, 1.05V) and outputs a comparison signal OUT corresponding to the comparison result.

When the comparison signal OUT has a low level, the coarse scan value is valid and determined, and the next operation may be performed.

If the comparison signal OUT has a high level, the setup operation S10 is performed again.

When the coarse scan value is 110, the comparator 31 compares the charged voltage Vs with the adjusted reference voltage (for example, 0.95V) and outputs a comparison signal OUT corresponding to the comparison result.

If the comparison signal OUT has a high level, the coarse scan value is valid and determined, and the next operation may be performed.

If the comparison signal OUT has a low level, the setup operation S10 is performed again.

A fine scan operation on the current is performed (S40).

The fine scan of the current refers to a process of finding a second current I2 at which the output signal OUT of the comparator 31 first becomes high to obtain a more sophisticated current value when the coarse scan value is determined. .

For example, when the bits of the second control code CD1 are 001, the second current I2 generated by the second current controller 41 is 0.125 mA.

The first switch 37 and the third switch 43 are turned on, and the second switch 39 is turned off.

Therefore, the capacitor C1 selected by the selection signal SS is charged according to the sum of the sum of the first current I1 and the second current I2.

For example, the sum of the first current I1 and the second current I2 is 5.125 mA.

The comparator 31 outputs a comparison signal OUT by comparing the voltage Vs charged with the reference voltage Vr charged by the sum of the first current I1 and the second current I2. At this time, the first switch 37, the second switch 39, and the third switch 43 are all turned off.

When the comparison signal OUT has a low level, the MCU 50 performs a second bit increasing operation of increasing the second control code CD2 by one bit. Accordingly, the second current controller 41 generates the increased second current I2 according to the second control code CD2 having one bit increased. For example, the second current I2 is 0.250 mA.

A second charging operation is performed to charge the capacitor C1 according to the sum of the first current I1 and the second current I2 (for example, 5.25 mA).

The comparator 31 compares the voltage Vs charged by the first current I1 and the second current I2 with the reference voltage Vr, and outputs a comparison signal OUT corresponding to the comparison result. The compare operation is performed.

The second bit increasing operation, the second charging operation, and the second comparison operation are repeatedly performed until the comparison signal OUT has a high level for the first time.

For example, assuming that the comparison signal OUT first has a high level when the second control code CD2 is 101, the value of the fine scan for the current is 100, which is a bit value of the second control code CD2.

According to an embodiment, a redundancy check operation may be performed to check whether a value of the fine scan for the current is valid, similar to the coarse scan (S50).

When the comparison signal OUT has a high level, the value of the fine scan is valid and determined, and the next operation may be performed.

If the comparison signal OUT has a low level, the file scan operation S40 for the current is performed again.

According to an embodiment, the reference voltage scan operation may be performed (S60).

The digital to analog converter 47 generates the reference voltage Vr according to the third control code CD3.

The third control code CD3 includes a plurality of bits.

For example, when the third control code CD3 is 4 bits, the digital-to-analog converter 47 generates a reference voltage Vr increased by 0.025V whenever the bits of the third control code CD3 are increased by one. .

When the sum of the first current I1 and the second current I2 is 5.5 mA, the comparator 31 compares the charged voltage Vs with the reference voltage Vr and compares the comparison signal corresponding to the comparison result ( OUT) is output.

When the comparison signal OUT has a low level, the MCU 50 performs a third bit increasing operation of increasing the third control code CD3 by one bit. Therefore, the digital-to-analog converter 47 generates an increased reference voltage Vr according to the third control code CD3 having one bit increased. For example, the reference voltage Vr is 1.025V.

A third charging operation is performed to charge the capacitor C1, which is the sum of the first current I1 and the second current I2 (for example, 5.5 mA).

The comparator 31 compares the voltage Vs charged by the first current I1 and the second current I2 with the reference voltage Vr, and outputs a comparison signal OUT corresponding to the comparison result. The compare operation is performed.

The third bit increasing operation, the third charging operation, and the third comparison operation are repeatedly performed until the comparison signal OUT has a high level for the first time.

The touch sensing circuit 30 is initialized.

After the touch sensing circuit 30 is initialized, when a conductive object (eg, a conductive pen such as a human finger or a stylus) approaches the touch sensor array 11, the touch sensor components 11-1. Capacitance between the two conductor plates of any one of ˜11-m) changes.

When the capacitance changes, the bit values of the first control code CD1, the second control code CD2, or the third control code CD3 to make the comparison signal OUT of the comparator 31 high are The capacitance is different from before.

Accordingly, the touch sensing circuit 30 may include the first control code CD1, the second control code CD2, or the third control code CD3 before the capacitance changes and the first control code after the capacitance changes. CD1), the second control code CD2, or the third control code CD3 may be compared to determine whether the conductive object is sensed.

When the conductive object approaches the touch sensor array 11, the capacitance becomes large.

Therefore, the first control code CD1, the second control code CD2, or the third control code CD3 after the capacitance changes, the first control code CD1, the second control code before the capacitance changes. When larger than the CD2 or the third control code CD3, the touch sensing circuit 30 may determine that the conductive object approaches the touch sensor array 11.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

10; 1 touch sensing system
11; Touch sensor array
20; Touch sensor
30; Touch sensing circuit
50; Micro control unit
60; Memory
31; Comparator
33; Selector
35; First current controller
37; The first switch
39; The second switch
41; Second current controller
43; The third switch
45; Switched capacitor array
47; Digital to analog converter

Claims (12)

A comparator including a first input terminal for receiving a charged voltage, a second input terminal for receiving a reference voltage, and an output terminal for outputting a comparison signal corresponding to a comparison result of the charged voltage and the reference voltage;
A selector for selecting any one of the plurality of capacitors in response to the selection signal generated by the micro control unit;
A first current controller for generating a first current supplied to the one of the selected capacitors according to a first control code generated by the micro control unit to generate the charged voltage;
A first switch connected between the first current controller and the first input terminal; And
A second switch and a resistor connected in series between the first input terminal and ground;
And the micro control unit increases the first control code by one bit until the comparison signal changes from a low level to a high level. The method of claim 1, wherein the touch sensing circuit,
A second current controller for generating a second current supplied to the selected one of the capacitors according to a second control code generated by the micro control unit to generate the charged voltage; And
And a third switch connected between the second current controller and the first input terminal. The method of claim 1, wherein the touch sensing circuit,
Further comprising a switched capacitor array comprising a plurality of internal capacitors and a plurality of switches,
The switched capacitor array,
And a touch sensing circuit connected between the first input terminal and ground. The method of claim 1, wherein the touch sensing circuit,
And a digital-to-analog converter for generating the reference voltage according to a third control code generated by the micro control unit. delete The apparatus of claim 1,
Outputting the comparison signal having a high level when the charged voltage is greater than the reference voltage,
And outputting the comparison signal having a low level when the charged voltage is less than the reference voltage. The touch sensing circuit of claim 2, wherein the first switch and the second switch operate complementary to each other. 3. The method of claim 2,
And the first switch is turned on before the third switch. A touch sensor array comprising a plurality of capacitors;
A micro control unit generating a first control code and a selection signal according to the comparison signal; And
A touch sensing circuit,
The touch sensing circuit,
A comparator including a first input terminal for receiving a charged voltage, a second input terminal for receiving a reference voltage, and an output terminal for outputting the comparison signal corresponding to a comparison result of the charged voltage and the reference voltage;
A selector for selecting any one of the plurality of capacitors in response to the selection signal;
A first current controller for generating a first current supplied to the one selected capacitor according to the first control code generated by the micro control unit according to the comparison signal to generate the charged voltage;
A first switch connected between the first current controller and the first input terminal; And
A second switch and a resistor connected in series between the first input terminal and ground;
And the micro control unit increments the first control code by one bit until the comparison signal changes from a low level to a high level. The method of claim 9, wherein the touch sensing circuit,
A second current controller for generating a second current supplied to the selected one of capacitors according to a second control code to generate the charged voltage; And
And a third switch connected between the second current controller and the first input terminal.
The second control code is,
And a touch sensing system generated by the micro control unit according to the comparison signal. The method of claim 9, wherein the touch sensing circuit,
And a digital analog converter for generating the reference voltage according to a third control code generated by the micro control unit according to the comparison signal. delete

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