KR20110052423A - Touch screen and compensation method for sensing capacitance variation and offset variation of the same - Google Patents

Abstract

PURPOSE: A touch screen and a compensation method for sensing capacitance variation and offset variation of the same are provided to increase the touch response speed by compensating for capacitance variation and offset variation. CONSTITUTION: A touch screen comprises: a touch panel where a plurality of driving lines and a plurality of sensing lines intersect and are wired; a driving unit for activating the driving lines sequentially; an input unit(20) for measuring a sensing capacitance formed in a sensing line corresponding to an activated driving line; a multiplexer(30) for serializing and outputting the measured sensing capacitance; an analog-to-digital converter(40) for sampling the sensing capacitance outputted from the multiplexer by reflecting an initial sensing capacitance as an offset and performing analog-to-digital conversion for the sampling result; and a host processor(60) for determining a touch event in response to the analog-to-digital conversion result.

Description

Touch screen and compensation method for sensing capacitance variation and offset variation of the same}

The present invention relates to a touch screen, and more particularly, to an apparatus and method for compensating for variation in sensing capacitance of a touch panel and reducing sensing error by compensating an offset of a charge amplifier of a controller input unit.

The present invention is derived from a study conducted as part of the IT SoC core design manpower development project of the Ministry of Knowledge Economy [Task Management Number: C1200-0901-0002, Task name: IT SoC core design manpower development].

Touch screens are one of the most popular human-machine interfaces. Touchscreens are used in many applications such as ATMs, laptop PCs, mobile devices, and the like. The touchscreen makes many functions easier to perform by simply touching or moving the cursor on the screen without the need for external input devices such as keyboards and mice. Because of these features, touchscreens are seen as more efficient, flexible, and cost effective interfaces when compared to keyboard, mouse, or key panel-only solutions.

Touch events of the touch screen may be sensed in various ways. For example, touch events of a touchscreen may include resistive, infrared infrared image, surface acoustic wave (SAW), acoustic pulse recognition (APR), and capacitive. It can be sensed through the sensing method.

Among them, the capacitive sensing method may be classified into a projected sensing method and a surface capacitive sensing method. Projected capacitive sensing methods have attracted much attention in that they can recognize multi-touch events.

However, the projection capacitive sensing method has a problem in that a sensing error may occur due to a variation in the sensing capacitance of the touch panel and an offset variation in the charge amplifier of the controller input unit. Sensing capacitance deviation and offset deviation of the controller input may result from manufacturing process variation caused when capacitance is formed. Therefore, in order to reduce the sensing error in the touch screen and accurately sense the touch event, a method for compensating the deviation of the manufacturing process of the capacitance of the touch panel and the offset deviation of the controller input unit is required.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide an apparatus and method for compensating for variation in sensing capacitance and offset variation in a controller input part generated in a manufacturing process of a touch panel.

Another object of the present invention is to provide an apparatus and a method capable of accurately sensing a touch event and reducing a sensing error in a touch screen even with a smaller chip area than a conventional controller.

In order to achieve the above object, the touch screen according to the present invention includes a touch panel in which a plurality of driving lines and a plurality of sensing lines are interconnected; A driver for sequentially activating the drive lines; An input unit configured to measure a sensing capacitance formed in a sensing line corresponding to the activated driving line; A multiplexer for serializing and outputting the measured sensing capacitance; An analog-digital converter for sampling the sensing capacitance output from the multiplexer by reflecting an initial sensing capacitance stored in a memory as an offset and digitally converting the sampling result; And a host processor configured to determine a touch event in response to the digital conversion result.

In an embodiment, the digital conversion result may correspond to a difference between the sensing capacitance and the initial sensing capacitance.

The analog-to-digital converter may include: a first switch configured to provide the sensing capacitance output from the multiplexer to the capacitor array in a sampling period; A capacitor array configured to sample the sensing capacitance in the sampling period after a plurality of capacitors are selectively connected to ground or a first reference voltage by the initial sensing capacitance; A SAR logic to provide the initial sensing capacitance to the capacitor array and to control a sampling result of the capacitor array to be output bit by bit in a digital conversion period; A comparator that receives the sampling result in bits and outputs digital data in bits in the digital conversion section; The sampling result may be provided from the capacitor array to the comparator in the digital conversion period.

In one embodiment, the capacitor array may be configured to be programmable.

In one embodiment, the sampling result may be input to the inverting input of the comparator.

In one embodiment, the capacitor array may correspond to a difference between a second reference voltage and a compensation voltage.

In one embodiment, the compensation voltage (V _COMP ), the second reference voltage is V _REF And recognizing deviations of the initial sensing capacitance, each bit is COMP ₁ , COMP ₂ ,... When COMP ₁₀

의 값을 가질 수 있다.

It can have a value of.

In an embodiment, the host processor may include a memory for storing the initial sensing capacitance, and the initial sensing capacitance may be provided from the memory to the capacitor array before the sampling interval is performed.

The input unit may include a plurality of charge amplifiers for converting the measured capacitance into voltage, and each of the plurality of charge amplifiers may include at least one feedback capacitor.

In one embodiment, in order to adjust the gain of the plurality of charge amplifiers, the feedback capacitor may configure a programmable capacitor array as a feedback capacitor under the control of the host processor.

The electronic device may further include an offset digital-to-analog converter configured to adjust a level of a reference voltage of the analog-to-digital converter under control of the host processor to compensate for offset deviations of the plurality of charge amplifiers. .

According to an aspect of the present invention, there is provided a sensing capacitance deviation and offset deviation compensation method of a touch screen, the method comprising: storing first data measured from a sensing capacitor when the panel is not touched at the beginning of driving of the touch screen controller; And converting second data measured from the sensing capacitor into digital data when the touch panel is driven to sense a touch, wherein the first data converts the second data into the digital data. Can be used to adjust the level of the sampling voltage for the second data.

The converting of the second data into the digital data may include: selectively connecting a plurality of capacitors of a capacitor array to ground or a first reference voltage based on the first data; Sampling the second data at the capacitor array; And converting the sampling result into N bits of digital data.

The converting of the N bits of digital data may include sequentially generating N scan signals corresponding to respective bits of the N bits of digital data; Sequentially inputting a voltage corresponding to each bit of the N bits of digital data among the sampling results into a comparator; And comparing the voltage input to the comparator with a second reference voltage to determine respective bits of the N-bit digital data.

In one embodiment, the sampling result may be input to the inverting input of the comparator.

In one embodiment, the N bits of digital data determined by the comparator may correspond to a difference between the first data and the second data.

In an embodiment, a voltage corresponding to the difference between the second reference voltage and the compensation voltage may be sampled in the capacitor array.

In one embodiment, the compensation voltage (V _COMP) is the second reference voltage V _REF And each of the bits of the first data value is COMP ₁ , COMP ₂ ,. When COMP ₁₀

의 값을 가질 수 있다.

It can have a value of.

In one embodiment, the level of the compensation voltage may be adjusted according to the first data value.

In an embodiment, the storing of the first data may be performed during an initialization operation in which driving of the touch panel is first started, or when an environment is changed.

In one embodiment, the method further comprises compensating for an offset of the charge amplifier measuring the second data from the sensing capacitor before the converting the second data into digital data is performed. A programmable feedback capacitor can be provided.

According to the present invention as described above, the difference between the current sensing capacitance and the initial sensing capacitance is extracted from the ADC itself of the touch panel by using the data stored during initialization, the deviation of the sensing capacitance generated in the manufacturing process and the offset deviation of the controller input unit To compensate. In this case, the compensation operation does not burden the computing device, thereby increasing the response speed of the touch panel.

In addition, the touch screen of the present invention may extract data for compensating for variation in sensing capacitance by applying a successive access register analog-to-digital converter (SAR-ADC) using an N-bit C-2C DAC. According to such a configuration, the touch screen can effectively reduce the sensing error of the touch screen and accurately sense the touch event, while occupying a smaller area than the SAR-ADC using the serial capacitor DAC.

1 is a diagram illustrating the overall configuration of a touch screen according to the present invention.
FIG. 2 is a diagram illustrating a detailed configuration of an input unit illustrated in FIG. 1.
FIG. 3 is a diagram illustrating a detailed configuration of the ADC illustrated in FIG. 1.
4 is a flowchart illustrating an example of a sensing capacitance deviation compensation method according to the present invention.
FIG. 5 is a diagram for describing a method of measuring an initial sensing capacitance C _INI and a method of extracting and storing compensation data COMP _{1 to} COMP _N from the initial state setup interval of FIG. 4.
6 and 7 illustrate a sampling operation of the ADC performed in the touch sensing and compensation section according to the present invention.
8 and 9 are diagrams for describing a data conversion operation and a deviation compensation method of an ADC performed in a touch sensing and compensation section according to the present invention.
FIG. 10 is a diagram for describing a data conversion operation and a deviation compensation method of the ADC illustrated in FIG. 9.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. Identical components will be referred to using the same reference numerals. Similar components will be quoted using similar reference numerals. The following embodiments may be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

The touch screen and its sensing capacitance deviation compensation method of the present invention, in order to compensate for the sensing capacitance deviation of the touch screen pad resulting from the manufacturing process, the initial value of the sensing capacitance during the set up initial conditions (hereinafter, Initial sensing capacitance (C _INI ) may be stored in memory. In addition, by using the initial sensing capacitance stored in the memory as an offset, the deviation of the sensing capacitance received during the touch sensing and compensation period is invalidated.

1 is a view showing the overall configuration of the touch screen 100 according to the present invention by way of example.

Referring to FIG. 1, the touch screen 100 according to the present invention includes a touch panel 10, an input unit 20, a multiplexer 30, an analog-to-digital converter, and an analog-to-digital converter. A digital convertor (ADC) 40, a host processor 60, and a driving unit 70 may be included. The input unit 20, the MUX 30, the ADC 40, the host processor 60, and the driver 70 may configure a controller.

The touch panel 10 may be configured as a projected capacitive touch panel to sense a touch event by a projected capacitive sensing method. The touch panel 10 may have a matrix structure in which a plurality of driving lines and a plurality of sensing lines cross each other. The driving lines may be disposed in the row direction on the touch panel 10, and the sensing lines may be disposed in the column direction on the touch panel 10, respectively. The driving lines and the sensing lines may be patterned in different layers, and the driving lines and the sensing lines may be manufactured in a structure separated by a transparent dielectric layer.

Capacitors may be formed at the intersection of each drive line and each sensing line, i.e., where the two patterned layers overlap. The capacitance of the capacitor is referred to as sensing capacitance C _SENSE . When a conductive object such as a finger approaches the touch panel 10, the size of the sensing capacitance C _SENSE changes. Accordingly, by sensing the change in the magnitude of the sensing capacitance C _SENSE , it is possible to know at which position the touch event occurs.

The driving lines of the touch panel 10 are connected to the driving unit 70, so that sequentially activated scan signals may be applied from the driving unit 70. The driver 70 may also be referred to as an excitation IC or a driving IC.

The activated scan signal applied to each driving line may be coupled to the corresponding sensing line through the sensing capacitance C _SENSE . As illustrated in FIG. 1, the plurality of sensing lines may be connected to the input unit 20. The input unit 20 may include a plurality of charge amplifiers CA. The plurality of charge amplifiers CA may form an array. Each charge amplifier CA may be connected to each sensing line.

When the sensing capacitance C _SENSE is changed in each sensing line, the amount of coupling is changed and thus the output value of the charge amplifier CA is changed. The charge amplifier CA senses the sensing capacitance C _SENSE of the corresponding sensing line and outputs it to the MUX 30. The MUX 30 sequentially transmits the output voltages of the input charge amplifiers CA to the ADC 40 in sequence (for example, in the form of a serial signal).

When the drive line is activated, all outputs of the charge amplifiers CA should exhibit the same voltage when the panel is not touched. However, due to the deviation of the sensing capacitance C _SENSE resulting from the manufacturing process of the panel, the outputs of the charge amplifiers CA have different values for each sensing line. As a result, the output values of the charge amplifiers CA may be changed even when the touch is not touched due to the variation in the sensing capacitance C _SENSE generated in the manufacturing process, and a sensing error occurs. In order to solve this problem, the ADC 40 according to the present invention compensates for the deviation of the sensing capacitance C _SENSE resulting from the manufacturing process, thereby preventing a sensing error.

That is, the ADC 40 according to the present invention, in response to the compensation data provided from the host processor 60, when the sensing capacitance C _SENSE is converted into a digital value, the deviation of the sensing capacitance C _SENSE resulting from the manufacturing process. To compensate. Therefore, in FIG. 1, the digital data output from the ADC 40 to the host processor 60 may refer to data in which a manufacturing process deviation of the sensing capacitance C _SENSE is compensated for. As will be described in detail below, the deviation compensation operation of the sensing capacitance C _SENSE according to the present invention may be performed by the ADC 40 without having a separate calculation circuit such as an adder or a subtractor.

The host processor 60 receives data compensated for the process deviation from the ADC 40 and performs image processing. To this end, the host processor 60 may include an image processing filter or an image filter. In addition, the host processor 60 may perform interpolation on the sensing result in the digital form. Interpolation may be performed with reference to the resolution of the touch screen 100. In addition, the host processor 60 may perform a function of controlling overall operations of the touch screen 100.

In addition, the host processor 60 provides compensation data to the charge amplifier CA of the input unit 20, so that the offset deviation of the controller input unit (eg, the offset deviation of the charge amplifier CA) resulting from the manufacturing process is reduced. Can be compensated. Here, the compensation data provided to the input unit 20 may be configured to be the same as the compensation data provided to the ADC 40, or may be adjusted to other values to suit the operating characteristics of the input unit 20. Detailed configuration and operation characteristics of the input unit 20 will be described in detail below with reference to FIG. 2.

FIG. 2 is a diagram illustrating a detailed configuration of the input unit 20 shown in FIG. 1. 2 illustrates a detailed configuration of one of the plurality of charge amplifiers CA provided in the input unit 20.

Referring to FIG. 2, the charge amplifier CA may be configured as an operational amplifier OP-amp. The feedback capacitor C _FB may be connected between the inverting input (−) and the output terminal of the charge amplifier CA. The charge-to-voltage conversion of the charge amplifier CA may be performed by the feedback capacitor C _FB . In addition, the reset switch S _RST is connected to the feedback capacitor C _FB in parallel to reset the charge amplifier CA. For example, when the reset switch S _RST is turned on (ie, closed), the inverting input (−) of the charge amplifier CA may be reset to the reference voltage V _REF0 .

In one embodiment, the charge amplifiers CA of the present invention may have a single feedback capacitor C _FB as shown in FIG. 2. According to the configuration of the present invention, the sensing capacitance can be achieved with the ADC 40 alone without using a gain controllable charge amplifier using a programmable capacitor array as a feedback capacitor to compensate for the touch panel sensing capacitance. In addition to the deviation of the controller can be compensated for both the offset deviation of the controller input. Therefore, the area of the circuit can be reduced. In this case, the offset deviation of the controller input unit, which is compensated for, does not mean only the offset deviation of the charge amplifiers CA, but the input unit 20, the MUX 30, the ADC 40, the host processor 60, and the driver unit ( 70) means the total input offset deviation of the controller.

In another embodiment, the charge amplifiers CA of the present invention may have a programmable capacitor array instead of a single feedback capacitor C _FB . In this case, the capacitor value of the programmable capacitor array of the charge amplifiers CA may be adjusted by compensation data provided from the host processor 60. As the value of the programmable capacitor array is adjusted, the gains of the charge amplifiers CA may be adjusted. According to such a configuration, in the state where the deviation of the sensing capacitor is compensated by the adjustment of the gain of the charge amplifiers CA, the offset deviation of the entire controller input unit may be compensated by the ADC 40.

In another embodiment, the touch screen 100 of the present invention includes an offset digital-to-analog converter (DAC) 50 for adjusting the level of the reference voltage V _REF1 of the ADC 40 of the ADC 40. May be further provided. The reference voltage compensation data used at this time may be provided from the host 60. According to such a configuration, in the state where the deviation of the sensing capacitor and the reference voltage V _REF1 of the ADC 40 are adjusted by the input unit 20 and the offset DAC 50, the entire controller input unit is controlled by the ADC 40. Offset deviation can be compensated for. Thus, more accurate error and deviation compensation can be achieved.

In the present invention, a case in which the single feedback capacitor C _FB is provided in the charge amplifier CA will be described as an example. However, this is an example to which the present invention is applied, and the configuration of the feedback capacitor of the charge amplifier CA may be changed and modified in various forms. In addition, whether or not the offset DAC 50 is provided according to the type of the controller is configured.

The charge amplifier CA may be connected to the corresponding sensing line through the node A. The sensing line may be wired on the touch panel 10 in a column direction. The inverting input (−) of the operational amplifier may be connected to node A, and a corresponding sensing line may be connected to node A. As shown in FIG. 1, each of the sensing lines may be interconnected with a plurality of driving lines. A sensing capacitance C _SENSE may be formed between the sensing line and the driving line. Parasitic capacitance is present around the sensing capacitance (C _SENSE ). The parasitic capacitance is the total sum of the capacitances of the sensing lines themselves, and may mean the total capacitance of the sensing lines. In an exemplary embodiment, the charge amplifier CA may be configured to minimize the overall parasitic capacitance in the sensing operation.

The reference voltage V _REF0 may be input to the non-inverting input (+) of the charge amplifier CA. In this case, the inverting input (−) of the charge amplifier CA acts substantially as a virtual ground. The output voltage Vout of the charge amplifier CA (represented as CA Output in FIG. 2) may be expressed as shown in [Equation 1].

은 구동 라인과 피드백 커패시터(C_FB)로 인가되는 활성화 신호의 전압(excitation signal voltage)을 의미한다. here,

Means an excitation signal voltage applied to the driving line and the feedback capacitor C _FB .

As shown in Equation 1, the output voltage V _OUT of the charge amplifier CA may be configured regardless of the overall parasitic capacitance. Therefore, the influence of parasitic capacitance in the sensing operation of the charge amplifier CA can be eliminated. For example, when the size of the feedback capacitor C _FB is adjusted according to Equation 1, the gain of the charge amplifier CA predicted at the output of the charge amplifier CA may be changed. Thus, it is possible to ensure that the charge amplifier CA operates stably within the dynamic range of the charge amplifier CA.

The size of the feedback capacitor C _FB may be adjusted in response to compensation data provided from the host processor 60. As a result, the gain of the charge amplifier CA predicted at the output of the charge amplifier CA is changed, so that the offset deviation of the controller input portion resulting from the manufacturing process (for example, the offset deviation of the charge amplifier CA). To compensate. Here, the compensation data provided to the input unit 20 may be configured to be the same as the compensation data provided to the ADC 40, or may be adjusted to other values to suit the operating characteristics of the input unit 20.

In particular, the charge amplifier CA of the present invention uses a charge amplifier using a single feedback capacitor in performing the adjustment and offset compensation of the gain of the charge amplifier CA with only a single feedback capacitor C _FB . Offset deviation of the charge amplifier can be compensated for. Therefore, it occupies a smaller area than the SAR-ADC using a serial capacitor DAC (serial capacitor DAC).

For example, a programmable capacitor array, used as a feedback capacitor in a gain controllable charge amplifier, has a large area that doubles with each increase in the number of bits of the programmed digital value. It takes up space. In contrast, in the present invention, since a charge amplifier using a single feedback capacitor is used instead of the gain-adjustable charge amplifier, its area can be greatly reduced. Therefore, while taking up a small chip area, it is possible to reduce the sensing error of the touch screen and accurately sense the touch event.

3 is a diagram showing the detailed configuration of the ADC 40 shown in FIG.

1 to 3, the input unit 20 may include a plurality of charge amplifiers CA connected to a plurality of sensing lines. Each charge amplifier CA senses a sensing capacitance C _SENSE of a corresponding sensing line and outputs it to the MUX 30.

The host processor 60 may be configured to include a core 61 and a memory 65. The core 61 may receive digital sensing results provided from the ADC 40 to perform image processing and / or interpolation. The touch event and the gesture may be determined according to the image processing and / or interpolation result of the core 61.

The memory 65 may store the measurement result of the initial sensing capacitance C _INI in the form of digital data bits. The measurement result of the initial sensing capacitance C _INI stored in the memory 65 may be used as compensation data COMP ₁ to COMP _N to compensate for the deviation caused by the process of the sensing capacitance C _SENSE . For example, the measurement result of the initial sensing capacitance (C _INI) is a compensation voltage (V _COMP), and each bit value of the compensation voltage (V _COMP) may be defined as COMP ₁ to _N COMP. In the following, the measurement result of the initial sensing capacitance C _INI will be described as the compensation data COMP ₁ to COMP _N for convenience of explanation.

The compensation data COMP ₁ to COMP _{P N} stored in the memory 65 are provided to the ADC 40 to be reflected in the sampling and data conversion of the currently measured sensing capacitance C _SENSE value, thereby resulting in the sensing capacitance derived from the manufacturing process. The deviation of (C _SENSE ) can be compensated.

The ADC 40 may include a first switch SW1, a second switch SW2, a capacitor array 410, a comparator 420, and a SAR logic (Successive Approximate Register Logic) 430. It may include. Here, the first switch SW1 and the second switch SW2 will be described as being included in the ADC 40 for convenience of description. However, this is an example of constituting the present invention, and the shape and configuration of the first switch SW1 and the second switch SW2 are not limited to a specific form and can be variously configured. For example, the first switch SW1 and the second switch SW2 may be included in the ADC 40 or may be separately configured outside the ADC 40.

The output of the MUX 30 may be connected to a sampling node SN of the ADC 40 by the first switch SW1. A capacitor array 410 including a plurality of capacitors may be connected to the sampling node SN. Capacitor array 410 may be configured to be programmable. The capacitor array 410 may constitute an N-bit C-2C DAC. In this case, the capacitor array 410 may have a capacitor array structure of C-2C. The output of the capacitor array 410 is used as the sampling capacitance Cs.

In an exemplary embodiment, the capacitor array 410 may include a plurality of first type capacitors C connected in parallel to the sampling node SN. Charge switches S ₁ to S _N may be connected to each of the plurality of first type capacitors. The ground voltage or the reference voltage V _REF2 may be selectively connected to the first type capacitor according to the switching operation of the charge switches S ₁ to S _N. In an exemplary embodiment, each first type capacitor may correspond sequentially from the most significant bit MSB to the least significant bit LSB of a plurality of bits (eg, N bits). For example, the first type capacitor connected to the first charge switch S ₁ may correspond to an MSB of N bits of digital data. The first type capacitor connected to the Nth charge switch S _N may correspond to the LSB among the N bits of digital data.

A second type capacitor 2C may be connected between adjacent first type capacitors. In addition, the second type capacitor may be configured to not be connected between the capacitor corresponding to the MSB and the LSB among the plurality of first type capacitors connected in parallel and an adjacent capacitor thereof. Here, the shape of the capacitor array 410 is not limited to a specific shape may be changed in various forms. In addition, the connection type and the capacitance of the first type capacitor C and the second type capacitor 2C may also be changed in various forms without being limited to a specific type.

The capacitance (i.e., sampling capacitance Cs) provided from the capacitor array 410 to the sampling node SN is controlled by the on / off operation of the charge switches S ₁ to S _N connected to the capacitor array 410. Can be determined. The on / off operation of the charge switches S ₁ to S _N is performed by the scan signals SO ₁ to SO _N provided from the SAR logic 430 and the compensation data COMP ₁ to COMP _N stored in the memory 65. Can be controlled by For example, the on / off operation of the charge switches S ₁ to S _N during the sampling operation of the ADC 40 may be controlled by the compensation data COMP ₁ to COMP _N stored in the memory 65. The on / off operation of the charge switches S ₁ to S _N in the data conversion operation of the ADC 40 may be controlled by the scan signals SO ₁ to SO _N provided from the SAR logic 430. . The ADC 40 may generate N bits of digital data bits b ₁ to b _N as a result of the analog-to-digital conversion, which outputs the output signals (O ₁ to O ₁₀ ) of the SAR logic 430 to the host processor 60. May be provided as

 If the resolution of the ADC 40 is N-bits, the ADC 40 will require a total of N frames to perform the compensation operation. However, since the ADC 40 of the present invention requires only one frame time for initial excitation when the compensation operation starts, the initialization operation time is significantly reduced. In addition, as the ADC 40 of the present invention is configured as a SAR-ADC using an N-bit C-2C DAC, the touch screen 100 of the present invention can take up a small area while having a high resolution.

4 is a flowchart exemplarily illustrating a sensing capacitance (C _SENSE ) deviation compensation method according to the present invention.

Referring to FIG. 4, the sensing capacitance C _SENSE compensation method may be largely divided into a set up initial conditions section and a touch sensing and compensation section. The initial state setup period may be performed when the driving of the touch panel 10 is started for the first time (ie, during an initialization operation) or when the environment is severely changed. Alternatively, the touch panel 10 may be performed during idle time when no touch occurs for a predetermined time or when no operation is performed in the host processor 60.

The operation performed in the initial state setup section is as follows.

First, in step S1000, the initial sensing capacitance C _INI is measured through the input unit 20. Here, the initial sensing capacitor C _INI means a value output from the charge amplifiers CA when the touch panel 10 is not touched. The measured initial sensing capacitor C _INI may mean a deviation of the sensing capacitor C _SENSE generated by the manufacturing process. The measured initial sensing capacitance C _INI value may be provided to the ADC 40 via the MUX 30.

In operation S1100, an analog-to-digital conversion is performed on the measurement result of the initial sensing capacitance C _INI measured in operation S1000 through the ADC 40, and compensation data is obtained from the digital conversion result of the measurement result (ie, V _COMP ). Extract (COMP ₁ to COMP _N ). In an exemplary embodiment, the compensation data COMP ₁ to COMP _N may correspond to each bit of the digital conversion result V _COMP of the measured value of the initial sensing capacitance C _INI . The extracted compensation data COMP ₁ to COMP _N are stored in the memory 65 in operation S1200. In the memory 65, compensation data COMP ₁ to COMP _N corresponding to an entire area or a partial area of the touch panel 10 may be stored.

In step S1300 it is determined whether the frame is terminated. Here, the frame may mean an entire area of the touch panel 10 or an area of the touch panel 10 to be applied to image processing. As a result of the determination in step S1300, if the frame is terminated, the initial state setup section ends. As a result of the determination in operation S1300, if the frame is not finished, the measurement operation on the initial sensing capacitance C _INI until the frame is finished and the compensation data COMP ₁ to ₁ corresponding to the initial sensing capacitance C _INI are performed. The extraction and storage operations of COMP _N ) are repeatedly performed.

The memory 65 may be provided inside the host processor 60 or may be provided outside the host processor 60. The memory 65 may be formed of a semiconductor memory such as a register, a flip-flop, an EEPROM, or the like. The configuration of the memory 65 and the storage method of the compensation data COMP ₁ to COMP _N stored in the memory 65 are not limited to a specific form and can be changed and modified in various forms.

After the initial state setup interval ends, the touch sensing and compensation interval may begin. The touch sensing and compensation section may mean a section in which the touch panel 10 is normally operated. Therefore, the operation performed in the touch sensing and compensation period may be repeated at any time without limit on the number of executions.

An operation performed in the touch sensing and compensation section is as follows.

First, when the touch sensing and compensation section starts, in operation S2100, compensation data stored in the initial state setup section may be provided from the memory 65 to the ADC 40. In operation S2200, the sensing capacitance C _SENSE is measured through the input unit 20 and the MUX 30, and the deviation of the sensing capacitance C _SENSE resulting from the manufacturing process is compensated for using the compensation data provided in the operation S2100. .

In an exemplary embodiment, the operation of compensating for the variation in the sensing capacitance C _SENSE may be performed in the ADC 40. For example, when the ADC 40 converts the sensing capacitance C _SENSE provided from the MUX 30 into digital data, the difference between the sensing capacitance C _SENSE and the initial sensing capacitance C _INI (that is, deviation compensation). Result). For example, the value of the sensing capacitance C _SENSE provided from the MUX 30 includes a deviation of the sensing capacitance C _SENSE generated during the manufacturing process. The initial sensing capacitance C _INI may correspond to the deviation of the sensing capacitance C _SENSE generated during the manufacturing process. Therefore, the present invention directly reflects the compensation data COMP ₁ to COMP _N extracted from the measured value of the initial sensing capacitance C _{INI as} the offset of the ADC 40 without going through a separate calculation process. Therefore, deviation compensation and analog-to-digital conversion of the sensing capacitance C _SENSE generated during the manufacturing process may be simultaneously performed.

For example, as seen from the step of sampling to convert the sensed capacitance (C _SENSE) into digital data in the invention, ADC (40) has a sensing capacitance (C _SENSE) only without the sampling compensation corresponding to the sensed capacitance (C _SENSE) Data (COMP _{1 to} COMPP _N ) can also be additionally sampled. The sampling result of the compensation data COMP _{1 to} COMP P _N additionally reflected in the sampling process will be provided to the inverting input (-) of the comparator 420 together with the sampling result of the sensing capacitance C _SENSE during the data conversion period. In this case, the compensation data COMP _{1 to} COMP _N may be reflected as an offset of the ADC 40.

According to such a configuration, the output of the comparator 420 output in the data conversion period becomes equal to the sensing capacitance C _SENSE minus the initial sensing capacitance C _INI . This may mean that the comparator 420 outputs output data in which a manufacturing process deviation of the sensing capacitance C _SENSE is compensated for. That is, when the compensation data COMP _{1 to} COMP P _N are reflected as the offset of the ADC 40, a separate operation for calculating the difference between the sensing capacitance C _SENSE and the initial sensing capacitance C _INI is used to compensate for the deviation. It is not necessary. Therefore, the configuration of the circuit becomes simpler, and the variation in the sensing capacitance C _SENSE resulting from the manufacturing process can be compensated for.

The compensation result of the deviation of the sensing capacitance C _SENSE may be output and stored as output data O ₁ ˜O _N of the ADC 40 in step S2300. The compensation result may be stored in the memory 65 of the host processor 60, or may be stored in another storage device corresponding thereto.

Subsequently, in step S2400, it is determined whether the frame is finished. As a result of the determination in step S2400, if the frame is not finished, steps S2100 to S2300 are repeated until the frame ends. In operation S2400, when the frame is finished, the deviation compensation result is provided to the core 61 of the host processor 60 in operation S2500. The deviation compensation result provided to the core 61 may correspond to one frame. In operation S2600, the core 61 performs image processing on the deviation compensation result. In operation S2700, it is determined at which position and how the touch event and gesture are generated according to the image processing result of the core 61. The operations of steps S2100 to S2700 (that is, operations of touch sensing and compensation intervals) described above may be repeated without limiting the number of times whenever the touch screen pad 10 is touched during normal operation.

FIG. 5 is a diagram for describing a method of measuring an initial sensing capacitance C _INI and a method of extracting and storing compensation data COMP _{1 to} COMP _N from the initial state setup interval of FIG. 4.

Referring to FIG. 5, initial sensing capacitances C _INI are measured through charge amplifiers CA provided in the input unit 20 when the driving line is activated and the touch panel 10 is not _touched . The measurement results of the initial sensing capacitances C _INI measured through the input unit 20 are serialized through the MUX 30 and sequentially provided to the ADC 40.

The operation performed by the ADC 40 can be largely divided into a sampling section and a data conversion section.

In the initial state setup period, the capacitor array 410 may be connected to all the capacitors corresponding to the MSB to LSB before the sampling operation is started. In this state, when the first switch SW1 is turned on (that is, closed), the sampling operation is started. During the sampling period, the capacitor array 410 samples the measurement result of the initial sensing capacitance C _INI . In the sampling operation, the second switch SW2 remains turned off (ie, opened).

Subsequently, when the first switch SW1 is turned off (ie, opened) and the second switch SW2 is turned on (ie, closed), the data conversion section starts. When the data conversion period starts, the SAR logic 430 sequentially generates scan signals SO ₁ to SO _N for setting a plurality of bits (eg, N bits) from the MSB to the LSB. The capacitor array 410 supplies the reference voltages V _REF2 at ground to the charge switches S ₁ to S _N corresponding to the MSBs to LSBs in response to the scan signals SO ₁ to SO _N generated from the SAR logic 430. ) Sequentially. Since the charge switches S ₁ to S _N are sequentially connected to the reference voltage V _REF2 at ground, the sampling results of the MSB of the measured initial sensing capacitance C _INI to the LSB are sequentially transferred to the comparator 420. Is provided. Each sampling result corresponding to the MSB to the LSB is input to the inverting input (-) of the comparator 420, and the reference voltage V _REF1 is input to the non-inverting input (+) of the comparator 420.

The comparator 420 compares the sampling result corresponding to the MSB to LSB of the initial sensing capacitance C _INI and the reference voltage V _REF1 , and compares the values of each of the MSB to LSB of the measurement result of the initial sensing capacitance C _INI . Determined as 0 or 1 digital data. Each bit value determined by the comparator 420 is stored in the memory 65 of the host processor via the SAR logic 640 as compensation data COMP _{1 to} COMP _N.

In the above, the measurement method of the initial sensing capacitance C _INI performed in the initial state setup period and the extraction and storage of the compensation data COMP _{1 to} COMP _N have been described. However, this is only an example to which the present invention is applied, and even during the idle time when no touch is generated in the touch panel 10 for a predetermined time or no operation is performed in the host processor 60, the initial sensing capacitance ( The measurement operation of C _INI ) and the extraction and storage of the compensation data COMP _{1 to} COMP _N may be performed. According to such a configuration, changes in the surrounding environment can be immediately reflected in the compensation data COMP _{1 to} COMP _N.

Hereinafter, a process deviation compensation operation of the sensing capacitance C _SENSE according to the present invention performed in the touch sensing and compensation section shown in FIG. 4 will be described with reference to FIGS. 6 to 10.

In one embodiment, the process deviation compensation operation of the sensing capacitance (C _SENSE ) according to the present invention may be performed in the ADC (40). An operation performed by the ADC 40 during the touch sensing and compensation period may be divided into a sampling period and a data conversion operation.

In the sampling operation, the compensation data COMP _{1 to} COMPP _N stored in the memory 65 may be reflected as an offset value of the sampling data before the sensing capacitance C _SENSE is sampled. The sampling result of the sensing capacitance C _SENSE sampled while the initial sensing capacitance C _INI is reflected as an offset is compared with a predetermined reference voltage V _REF1 in the data conversion period. And based on the comparison result, N bits of digital data each having a value of 0 or 1 can be generated as an analog-to-digital conversion result. Thus, the sensing capacitance (C _SENSE) and initial sensing capacitance (C _INI) (i.e., data compensation (COMP ₁ ~COMP _N)) separate without the need to perform the operation for the period, or in addition off my difference, the sensing capacitance (C _SENSE Variation in the manufacturing process can be compensated for.

6 and 7 illustrate a sampling operation of the ADC 40 performed in the touch sensing and compensation section according to the present invention. 6 shows the operation timing of the ADC 40 for performing the sampling operation. 7 illustrates a data flow (see hatching) of the compensation data COMP ₁ to COMP _N provided to the ADC 40 during the sampling operation.

6 and 7, in the touch sensing and compensation period, the capacitors corresponding to the MSBs to the LSBs included in the capacitor array 410 may have the SAR logic 430 before the sensing capacitance C _SENSE is sampled. It may be selectively connected to the ground or the reference voltage (V _REF2 ) by the compensation data (COMP ₁ ~ COMP _{P N} ) provided from. In this case, the compensation data COMP ₁ to COMP _N may be provided to the capacitor array 410 of the ADC 40 from the memory 65 through the SAR logic 430 as shown in FIG. 7. As a result, the compensation data COMP ₁ to COMP _N may be reflected as an offset value during the sampling operation of the sensing capacitance C _SENSE .

In this state, when the first switch SW1 is turned on (ie, closed) and the sampling operation is started, the capacitor array 410 receives the sensing capacitance C _SENSE (ie, the touch panel sensing signal provided from the MUX 30). Sampling is performed on In the sampling operation, the second switch SW2 remains turned off (ie, opened). The capacitance sampled in the capacitor array 410 during the sampling period (ie, the sampling capacitance Cs) is the compensation data corresponding to the sensing capacitance C _SENSE provided from the MUX 30 and the initial sensing capacitance C _INI . Can be determined by (COMP ₁ ~ COMP _N ).

During the sampling period, a voltage corresponding to the difference between the reference voltage and the compensation voltage V _REF1 -V _COMP may be sampled in the capacitor array 410. V _COMP is a compensation voltage corresponding to the initial sensing capacitance C _INI , which may be expressed as Equation 2 below.

Here, COMP ₁ represents the MSB of the compensation voltage (V _{COMP), COMP 10} represents the LSB of the compensation voltage (V _COMP).

8 and 9 are diagrams for explaining a data conversion operation and a deviation compensation method of the ADC 40 performed in the touch sensing and compensation section according to the present invention. 8 shows an operation timing of the ADC 40 for performing a data conversion operation. FIG. 9 illustrates a data flow (see hatching) for generating an analog-to-data conversion result (that is, compensated data O ₁ to O _N ) output from the ADC 40 during a data conversion operation.

8 and 9, after the sampling operation is performed in the capacitor array 410, the first switch SW1 is turned off (ie, opened) and the second switch SW2 is turned on (ie, closed). The data conversion section may be started.

When the data conversion period starts, the SAR logic 430 sequentially generates scan signals SO ₁ to SO _N for setting a plurality of bits (eg, N bits) from the MSB to the LSB. The capacitor array 410 supplies the reference voltages V _REF2 at ground to the charge switches S ₁ to S _N corresponding to the MSBs to LSBs in response to the scan signals SO ₁ to SO _N generated from the SAR logic 430. ) Sequentially. Since the charge switches S ₁ to S _N are sequentially connected from the ground to the reference voltage V _REF2 , the sampling result of the sensing capacitance C _SENSE reflecting the initial sensing capacitance C _INI as the offset value is MSB. To LSB in sequence, are provided to the comparator 420.

Each sampling result corresponding to the MSB to the LSB is input to the inverting input (-) of the comparator 420, and the reference voltage V _REF1 is input to the non-inverting input (+) of the comparator 420. The comparator 420 compares each sampling result corresponding to the MSB to the LSB and the reference voltage V _REF1 , and outputs the comparison result in the form of digital data O ₁ ˜O _N. Therefore, the analog-to-digital conversion results O ₁ to O _N of the ADC 40 according to the present invention correspond to a result of the compensation of the deviation of the sensing capacitance C _SENSE generated during the manufacturing process.

FIG. 10 is a diagram for describing a data conversion operation and a deviation compensation method of the ADC 40 illustrated in FIG. 9. 10 illustrates the overall configuration of the touch screen 100 and the detailed configuration of the ADC 40 having a resolution of 10 according to the present invention.

In FIG. 10, the host processor 60 may provide the compensation data COMP ₁ to COMPN _N to the ADC 40 to compensate for the deviation of the sensing capacitance C _SENSE . However, since the compensation data COMP ₁ to COMPP _N may be provided in the sampling period, the compensation data COMP ₁ to COMPP _N are not specifically illustrated in FIG. Instead, the compensation data COMP ₁ to COMP _N are specifically illustrated in FIG. 7, which is a diagram for explaining a sampling operation.

In FIG. 10, b ₁ to b ₁₀ provided from the SAR logic 430 to the capacitor array 410 may mean an initial value (ie, an initial digital bit) of an analog-to-digital conversion result output from the ADC 40. have. B ₁ to b ₁₀ may be generated as initial digital bits from the SAR logic 430 when the analog input signal begins to be applied. Here, b ₁ may represent the MSB of the analog-to-digital conversion result output from the ADC 40, and b ₁₀ may represent the LSB of the analog-to-digital conversion result output from the ADC 40.

8 to 10, when the first scan signal SO ₁ generated by the SAR logic 430 is activated to connect the switch S ₁ from ground (0V) to the reference voltage V _REF2 , b ₁ Is applied to the inverting input (-) of the comparator through the sampling node SN. The comparator 420 compares the voltage of the sampling node SN with the reference voltage V _REF1 provided to the non-inverting input (+) and outputs a value of b ₁ as 0 or 1.

For example, a, V _x is referred to as the sampled voltage sampling Vs during the sampling period i-inverting input of the comparator 420 in the conversion stage of the second bit through the sampling node (SN) - Let the voltage supplied to the ().

The output of the comparator 420, the comparison result, the reference voltage V _x is greater than comparator 420 (V _REF1) is at a logic low, b ₁ is zero. In this case, SAR logic 430 causes switch S1 to connect to ground at reference voltage V _REF2 , causing V _x to return to sampling voltage V _s . As a result of the comparison in the comparator 420, when V _x is less than the _reference voltage V _REF1 , the output of the comparator 420 is logic high, and b ₁ is 1. In this case, the SAR logic 430 maintains the state in which the switch S1 is connected to the reference voltage V _REF2 . In this way the value of the MSB of the analog-to-digital conversion result is determined. In the same manner as above, the digital values for the second to last bit LSB of the analog-to-digital conversion result are sequentially determined.

Equation 3 represents the relationship between the voltage V _x and the reference voltage VREF1 provided to the inverting input (-) of the comparator 420 through the sampling node SN in the conversion step for the i th bit. It may be displayed as follows.

Equation 3 shows the behavior of the SAR ADC during initial state setup. When initially setting up ₁ b ~b _N is soon O ₁ ~O _N. However, during touch sensing and compensation, Vin is changed by the compensation voltage V _COMP , so that Equation 3 can be expressed as Equation 4.

[Equation 4] can be developed as shown in [Equation 5].

If the voltage value of any capacitor that is not compensated is V _REF -V _IN , and the number of bits of the corresponding digital value is b _n , the value compensated by the bit COMP _n of the corresponding compensation voltage V _COMP (O _n ) is the same as [Equation 6].

는 초기 센싱 커패시턴스(C_INI)로부터 얻어진 보상전압(

)에 해당된다. V_x와

는 모두 초기 센싱 커패시턴스(C_INI)가 반영되어 얻어진 전압들이다. [수학식 3]으로부터 알 수 있는 바와 같이, 제조 공정시 발생된 센싱 커패시턴스(C_SENSE)의 편차는 초기 센싱 커패시턴스(C_INI)가 반영된 V_x와

에 의해 보상될 수 있다. here,

Is the compensation voltage obtained from the initial sensing capacitance (C _INI )

Corresponds to). V _x and

Are the voltages obtained by reflecting the initial sensing capacitance (C _INI ). As can be seen from [Equation 3], the deviation of the sensing capacitance C _SENSE generated in the manufacturing process is determined by V _x reflecting the initial sensing capacitance C _INI .

Can be compensated for.

According to the present invention as described above, the difference between the current sensing capacitance and the initial sensing capacitance is extracted from the ADC itself of the touch panel by using the data stored during initialization, the deviation of the sensing capacitance generated in the manufacturing process and the offset deviation of the controller input unit To compensate. In this case, since the compensation operation occurs at the same time as the measurement operation, the response speed of the touch panel can be increased because no time for the additional compensation operation is required.

Compensating the deviation of the sensing capacitance and the offset deviation of the controller input unit may be performed through the input unit 20 and the ADC 40 as shown in FIGS. 2 and 10. However, this is an example to which the present invention is applied, and the deviation compensation operations of the input unit 20 and the ADC 40 are not limited to specific embodiments and may be changed and modified in various forms. For example, the deviation may be compensated through only the input unit 20, and the touch screen may be configured to compensate for the deviation through only the ADC 40. Alternatively, both the input unit 20 and the ADC 40 may be configured to compensate for the deviation of the sensing capacitance and the offset deviation of the controller input unit. In addition, the deviation compensation of the present invention is optionally provided with an offset DAC 50 shown in Figure 2, it is also possible to adjust the reference voltage of the ADC (40).

Meanwhile, the touch screen of the present invention may extract data for compensating for variation in sensing capacitance by applying a Successive Approximation Register Analog-to-Digital Converter (SAR-ADC) using an N-bit C-2C DAC. According to such a configuration, the touch screen can effectively reduce the sensing error of the touch screen and accurately sense the touch event, while occupying a smaller area than the SAR-ADC using the serial capacitor DAC.

As described above, embodiments of the present invention have been disclosed. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

10: touch panel 20: input unit
30: multiplexer 40: analog-to-digital converter (ADC)
60: host processor 61: core
65 memory 70 drive unit
100: touch screen

Claims (20)

A touch panel in which a plurality of driving lines and a plurality of sensing lines cross each other;
A driver for sequentially activating the drive lines;
An input unit configured to measure a sensing capacitance formed in a sensing line corresponding to the activated driving line;
A multiplexer for serializing and outputting the measured sensing capacitance;
An analog-digital converter for sampling the sensing capacitance output from the multiplexer by reflecting an initial sensing capacitance as an offset and digitally converting the sampling result; And
And a host processor configured to determine a touch event in response to the digital conversion result. The method of claim 1,
The digital conversion result corresponds to a difference between the sensing capacitance and the initial sensing capacitance. The method of claim 1,
The initial sensing capacitance is measured when the touch panel is not touched. The method of claim 1,
The analog-to-digital converter,
A first switch configured to provide the sensing capacitance output from the multiplexer to the capacitor array in a sampling period;
A capacitor array configured to sample the sensing capacitance in the sampling period after a plurality of capacitors are selectively connected to ground or a first reference voltage by the initial sensing capacitance;
A SAR logic to provide the initial sensing capacitance to the capacitor array and to control a sampling result of the capacitor array to be output bit by bit in a digital conversion period;
A comparator that receives the sampling result in bits and outputs digital data in bits in the digital conversion section; And
And a second switch configured to provide the sampling result from the capacitor array to the comparator in the digital conversion period. The method of claim 4, wherein
And a voltage corresponding to a difference between a second reference voltage and a compensation voltage is sampled on the capacitor array. The method of claim 5, wherein
The compensation voltage (V _COMP ), the second reference voltage is V _REF And each of the bits of the initial sensing capacitance is COMP ₁ , COMP ₂ ,. When COMP ₁₀

Touch screen with the value of. The method of claim 4, wherein
The host processor includes a memory for storing the initial sensing capacitance, wherein the initial sensing capacitance is provided from the memory to the capacitor array before the sampling interval is performed. The method of claim 1,
The input unit includes a plurality of charge amplifiers for converting the sensed capacitance into a voltage, each of the plurality of charge amplifiers having at least one feedback capacitor. The method of claim 8,
And the feedback capacitor forms a programmable capacitor array under control of the host processor to adjust the gain of the plurality of charge amplifiers so that the sensing capacitor is compensated. The method of claim 8,
And an offset digital-analog converter configured to adjust a level of a reference voltage of the analog-to-digital converter under control of the host processor to compensate for offset deviations of the plurality of charge amplifiers. Storing first data measured from a sensing capacitor when the touch panel is not touched; And
Converting the second data measured from the sensing capacitor into digital data when the touch panel is touched,
And the first data is used to adjust a level of a sampling voltage for the second data when converting the second data to the digital data. The method of claim 11,
Converting the second data into the digital data,
Selectively connecting a plurality of capacitors of a capacitor array to ground or a first reference voltage based on the first data;
Sampling the second data at the capacitor array; And
And converting the sampling result into N bits of digital data. The method of claim 12,
Converting to the N bits of digital data,
Sequentially generating N scan signals corresponding to each bit of the N bits of digital data;
Sequentially inputting a voltage corresponding to each bit of the N bits of digital data among the sampling results into a comparator; And
And comparing each of the voltages input to the comparator with a second reference voltage to determine respective bits of the N bits of digital data. The method of claim 13,
The sampling result is a sensing capacitance deviation and offset deviation compensation method of the touch screen input to the inverting input of the comparator. The method of claim 13,
The N-bit digital data determined by the comparator is a sensing capacitance deviation and offset deviation compensation method of the touch screen corresponding to the difference between the first data and the second data. The method of claim 11,
2. The method of claim 1, wherein the capacitor array is sampled with a voltage corresponding to a difference between a second reference voltage and a compensation voltage. 17. The method of claim 16,
The compensation voltage (V _COMP ), the second reference voltage is V _REF And each of the bits of the first data value is COMP ₁ , COMP ₂ ,. When COMP ₁₀

A method for compensating for sensing capacitance deviation and offset deviation of a touch screen having a value of. 17. The method of claim 16,
And the level of the compensation voltage is adjusted according to the first data value. The method of claim 11,
The storing of the first data may include a sensing capacitance deviation and an offset deviation compensation method of a touch screen, which is performed during an initialization operation that first starts driving the touch panel or when an environment changes. The method of claim 11,
Compensating for an offset of the charge amplifier measuring the second data from the sensing capacitor before converting the second data into digital data;
The charge amplifier is a sensing capacitance deviation and offset deviation compensation method of a touch screen having a programmable feedback capacitor.

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