KR20120055175A - Apparatus and method for driving touch sensor - Google Patents

Abstract

PURPOSE: A touch sensor driving device and a method thereof are provided to effectively eliminate noise components using a driving waveform of a specific frequency band different from noise. CONSTITUTION: A touch controller(30) drives a touch sensor(20) using a second scan pulse into a high frequency of a specific domain is inserted. The first scan pulse is for determining a scanning period of the touch sensor. The specific domain avoids a frequency of a noise component of the first scan pulse. The touch controller filters an output signal of the touch sensor. The touch controller passes a signal with a high frequency of the specific area. The touch controller detects and outputs sensing data from the high frequency signal.

Description

Touch sensor driving device and method {APPARATUS AND METHOD FOR DRIVING TOUCH SENSOR}

The present invention relates to a touch sensor driving apparatus and method, and more particularly to a touch sensor driving apparatus and method that can effectively remove the noise component by using a drive waveform of a specific frequency band different from noise.

Today, touch sensors capable of inputting information by touch on screens of various display devices are widely applied as information input devices of computer systems. The touch sensor can be easily used by anyone of all ages since the user simply touches the screen with a finger or a stylus to move or select display information.

The touch sensor detects the touch and the touch position generated on the display device screen to output touch information, and the computer system analyzes the touch information to perform a command. As the display device, a flat panel display device such as a liquid crystal display device, a plasma display panel, an organic light emitting diode display device, or the like is mainly used. Touch sensor technology includes a resistive film method, a capacitive method, an optical method, an infrared method, an ultrasonic method, and an electromagnetic method according to a sensing principle.

The touch sensor is composed of an on-cell touch sensor manufactured in the form of a panel and attached to an upper portion of the display device, or an in-cell touch sensor embedded in a pixel matrix of the display device. It is composed of As the touch sensor, a photo touch sensor that recognizes a touch according to light intensity using a photo transistor and a capacitive touch sensor that recognizes a touch according to a capacitive variable are mainly used.

In a display device having a touch sensor, a signal-to-noise ratio (SNR) is low due to a noise component generated from the display device, thereby lowering the sensing sensitivity or delaying the detection time of the sensing signal. Since the driving waveform of the conventional touch sensor has a low frequency square wave waveform, the driving waveform of the conventional touch sensor has a disadvantage of being extremely vulnerable to noise of a display device such as a liquid crystal display.

In order to reduce the noise component, the conventional touch controller additionally uses various noise filters such as a low pass filter, a rank filter, an average filter, etc. Increase the SNR). However, conventional noise filters have to repeat filtering until the noise component is reduced in order to increase the signal-to-noise ratio (SNR), and the detection time of the sensing data is delayed by increasing the number of sampling for the output signal of the touch sensor. There is a problem.

The present invention has been made to solve the above-mentioned problems of the prior art, the problem to be solved by the present invention is a touch sensor driving device and method that can effectively remove the noise component by using the drive waveform of the noise and other specific frequency band To provide.

In order to solve the above problems, the touch sensor driving device according to an embodiment of the present invention includes a touch sensor attached to or integrated in the display panel; The touch sensor is driven by using a second scan pulse in which a high frequency of a specific region in which a frequency of a noise component is avoided is inserted into a first scan pulse for determining a scanning period of the touch sensor, and the output signal of the touch sensor is filtered. And a touch controller configured to pass a signal having a high frequency of the specific region and to detect and output sensing data from the high frequency signal.

The touch controller may include a high frequency generator generating a high frequency of the specific region; A touch sensor driver for switching a high frequency from the high frequency generator in response to the first scan pulse to supply a second scan pulse having the high frequency inserted thereto to each transmission line of the touch sensor; Band-pass filtering the signal output through each receiving line of the touch sensor to output a high frequency of the specific region, and output the sensing signal by low-pass filtering the output signal, and converts the sensing signal into digital data A touch sensor for outputting sensing data; And a signal processor configured to generate the first scan pulse to control the touch sensor driver and to calculate and output a touch coordinate value by combining the sensing data supplied from the touch sensor.

The touch sensing unit includes an amplifier for comparing and amplifying the output signal of the touch sensor with a reference voltage and outputting the amplified signal; A band pass filter for band-pass filtering the output signal of the amplifier and outputting a high frequency of the specific region; A low pass filter configured to low pass filter the output signal of the band pass filter to output the sensing signal; And an analog-digital converter configured to convert the output signal of the low pass filter into the digital data and output the sensing data.

A touch sensor driving method according to an embodiment of the present invention comprises the steps of generating a high frequency of a specific region avoiding the frequency of the noise component; Generating a first scan pulse that determines a scanning period of the touch sensor; Switching the high frequency of the specific region in response to the first scan pulse to drive the touch sensor with a second scan pulse in which the high frequency of the specific region is inserted; Band-pass filtering the output signal of the touch sensor to pass a signal having a high frequency of the specific region; Outputting a sensing signal by performing low pass filtering on the band pass filtered output signal; Converting the sensing signal into digital data and outputting sensing data; And calculating and outputting touch coordinate values by combining the sensing data.

The fundamental frequency of the sensing signal is equal to the frequency of the first scan pulse.

The high frequency of the specific region has a frequency that forms an impedance match with the capacitance of the touch sensor.

The touch sensor driving apparatus and method according to the present invention uses a frequency of a specific region, which avoids the frequency of a main noise source including a display device, as a driving waveform of the touch sensor, and passes a band pass mainly through the frequency of the specific region. By using a filter and a low pass filter, the ambient noise component can be effectively removed.

In addition, the touch sensor driving apparatus and method according to the present invention, by avoiding the frequency of the main noise source, while using the optimum frequency matching the impedance (that is, capacitance) of the capacitive touch sensor as the drive waveform of the touch sensor, the noise component Can be removed more effectively to improve the sensitivity.

Accordingly, the apparatus and method for driving a touch sensor according to the present invention can improve sensing sensitivity by increasing the signal-to-noise ratio (SNR), and shorten the detection time of sensing data by reducing the number of sampling.

1 is a block diagram schematically illustrating a driving device of a display device having a touch sensor according to an exemplary embodiment of the present invention.
FIG. 2 illustrates a capacitive touch sensor as an example of the touch sensor illustrated in FIG. 1.
3 is a driving waveform diagram of the touch sensor illustrated in FIG. 2.
4 is a block diagram illustrating an internal configuration of the touch controller shown in FIG. 1.
5 is an input / output waveform diagram of the touch sensor driver illustrated in FIG. 4.
6 is an input / output waveform diagram of the touch sensing unit illustrated in FIG. 4.
7A and 7B are graphs illustrating a comparison between sensing data output values of a touch sensor driving apparatus according to the present invention.

1 is a block diagram schematically illustrating a display device having a touch sensor driving device according to an exemplary embodiment of the present invention.

The display device having the touch sensor shown in FIG. 1 includes a display panel 10, a data driver 12 and a gate driver 14 driving the display panel 10, a data driver 12 and a gate driver 13. And a timing controller 18 for controlling the panel driver 16 including the touch panel, a touch sensor 20 on the display panel 10, and a touch controller 30 for driving the touch sensor 20. The timing controller 18 and the touch controller 30 are connected to the host computer 50.

The timing controller 18 and the data driver 12 may be integrated into respective integrated circuits (ICs), or the timing controller 18 may be integrated into the data driver 12 and integrated into one IC. The touch controller 30 and the timing controller 18 may also be integrated into respective ICs, or the touch controller 30 may be integrated into the timing controller 18 and integrated into one IC.

The host computer 50 supplies image data and a plurality of synchronization signals to the timing controller 18, analyzes touch information input from the touch controller 30, and performs a command.

As the display panel 10, a flat panel display panel such as a liquid crystal display panel (hereinafter, referred to as a liquid crystal panel), a plasma display panel, and an organic light emitting diode display panel may be mainly used. Hereinafter, a liquid crystal panel will be described as an example. When a liquid crystal panel is used as the display panel 10, the display panel 10 includes a color filter substrate on which a color filter array is formed, a thin film transistor substrate on which a thin film transistor array is formed, and a liquid crystal layer between the color filter substrate and the thin film transistor substrate. And a polarizing plate attached to the outer surface of the color filter substrate and the thin film transistor substrate, respectively. The display panel 10 displays an image through a pixel matrix in which a plurality of pixels are arranged. Each pixel realizes a desired color by using a combination of red, green, and blue sub-pixels that adjust light transmittance by varying liquid crystal arrays according to data signals. Each subpixel includes a thin film transistor TFT connected to a gate line GL and a data line DL, a liquid crystal capacitor Clc connected in parallel with the thin film transistor TFT, and a storage capacitor Cst. The liquid crystal capacitor Clc charges the data signal supplied to the pixel electrode through the thin film transistor TFT and the difference voltage between the common voltage Vcom supplied to the common electrode and drives the liquid crystal according to the charged voltage to thereby transmit light. Adjust. The storage capacitor Cst keeps the voltage charged in the liquid crystal capacitor Clc stable. The liquid crystal layer is driven by a vertical electric field such as twisted nematic (TN) mode or vertical alignment (VA) mode, or by a horizontal electric field such as IPS (In-Plane Switching) mode or FFS (Fringe Field Switching) mode.

The timing controller 18 processes the image data input from the host computer 50 and supplies it to the data driver 12. For example, the timing controller 18 corrects and outputs data by overdriving driving to add an overshoot value or an undershoot value according to the data difference between adjacent frames in order to improve the response speed of the liquid crystal. can do. In addition, the timing controller 18 uses a plurality of synchronization signals input from the host computer 18, that is, the data driver 12 using a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal, and a dot clock. Generates a data control signal for controlling the driving timing of the control panel) and a gate control signal for controlling the driving timing of the gate driver 14, and supplies the data control signal and the gate control signal to the data driver 12 and the gate driver 14, respectively. Output The data control signal includes a source start pulse and a source sampling clock for controlling the latch of the data signal, a polarity control signal for controlling the polarity of the data signal, a source output enable signal for controlling the output period of the data signal, and the like. The gate control signal includes a gate start pulse and a gate shift clock for controlling the scanning of the gate signal, a gate output enable signal for controlling the output period of the gate signal, and the like. The timing controller 18 supplies a synchronization signal (a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, etc.) to the touch controller 30 to drive the driving timing of the liquid crystal panel 10 and the driving timing of the touch sensor 20. Driving timing of the touch controller 30 may be controlled to interlock with each other.

The gate driver 14 sequentially drives a plurality of gate lines GL formed in the thin film transistor array of the liquid crystal panel 10 in response to a gate control signal from the timing controller 11. The gate driver 14 supplies a scan pulse of a gate-on voltage for each scan period of each gate line GL, and supplies a gate-off voltage in the remaining periods in which another gate line GL is driven. The gate driver 14 includes at least one gate IC and is mounted on a circuit film such as a tape carrier package (TCP), a chip on film (COF), a flexible print circuit (FPC), and the like, and the tape driver (TAB) on the display panel 10. The display panel 10 may be attached by an automatic bonding method or mounted on the display panel 10 by a chip on glass (COG) method. In addition, the gate driver 14 may be embedded in the display panel 10 in a gate in panel (GIP) manner and formed on the thin film transistor substrate together with the pixel array.

The data driver 12 supplies the image data from the timing controller 18 to the plurality of data lines DL of the display panel 10 in response to the data control signal from the timing controller 18. The data driver 12 converts the digital data input from the timing controller 18 into a positive / negative analog data signal using a gamma voltage, and converts the data signal each time the gate line GL is driven. DL). The data driver 12 includes at least one data IC and is mounted on a circuit film such as TCP, COF, FPC, etc., and attached to the display panel 10 in a tape automatic bonding (TAB) method, or in a chip on glass (COG) method. The display panel 10 may be mounted on the display panel 10.

The touch sensor 20 mainly uses a capacitive touch sensor that senses a touch by detecting a change in capacitance generated when a small amount of electric charge moves to a touch point when a human body or a conductor such as a stylus touches the touch point. The touch sensor 20 may be attached to the display panel 10 or embedded in the pixel array of the display panel 10. For example, in the capacitive touch sensor 20 attached to the display panel 10, a plurality of first sensing electrodes 22 arranged in a row direction as shown in FIG. 2 are electrically connected to each other. The transmission lines TX1 to TXn and the plurality of second sensing electrodes 24 arranged in the column direction may be electrically connected to each other and may include a plurality of reception lines RX1 to RXm. Each of the first and second sensing electrodes 22 and 24 is mainly formed in a rhombus shape and may be formed in various other shapes. The first and second sensing electrodes 22 and 24 are driven by the touch controller 30 to form capacitance by a fringe field, and a capacitor with a conductive touch object that touches the touch sensor 20. And output a signal indicating whether or not it is touched by changing the capacitance. As each of the transmission lines TX1 to TXn of the touch sensor 20 is sequentially driven by the scan waveform supplied from the touch controller 30, an output signal indicating whether a touch is received through the reception lines RX1 to RXm is a touch controller ( 30).

The touch controller 30 supplies a driving signal to the touch sensor 20, senses a touch through an output signal from the touch sensor 20, generates sensing data, calculates touch coordinates from the sensing data, and generates a host computer ( 50). The touch controller 30 drives the touch sensor 20 by synthesizing a scan waveform with a square wave or a sine wave having a high frequency of a specific region while avoiding a noise source frequency. In other words, as illustrated in FIG. 3, the touch controller 30 switches the high frequency of the specific area and supplies it to each transmission line for each scan period T for driving the transmission lines TX1 to TXn of the touch sensor 20. As a result, the touch sensor 30 is driven. The high frequency of the specific region has a higher frequency than the general low frequency scan waveform of the touch sensor 20 and is designed not to overlap with the frequency of noise and other ambient noise (such as power supply noise) of the display device including the display panel 10. do. In addition, the high frequency of the specific frequency may be designed to form impedance matching with the capacitance of the touch sensor 20 without overlapping the noise frequency.

Accordingly, the touch sensor 20 receives each Rx1 of the touch sensor 20 in response to the driving waveform of the specific high frequency supplied for each scan period T of each of the transmission lines TX1 to TXn as shown in FIG. 3. ~ RXm) receives the output signal of the specific high frequency indicating whether or not the touch and outputs it to the touch controller 30. The touch controller 30 may amplify the output signal of the touch sensor 20, pass-band filter and low pass filter, and pass the output signal around the high frequency of the specific region to output a sensing signal from which noise components are effectively removed. . In addition, the touch controller 30 converts the analog sensing signal from which the noise component is removed into digital sensing data, calculates the touch coordinate value using the sensing data, and supplies the same to the host computer 50.

4 is an internal block diagram illustrating an embodiment of the touch controller 30 shown in FIG. 1.

The touch controller 30 shown in FIG. 4 includes a touch detector 40, a signal processor 32, a high frequency generator 34, and a touch sensor driver 36.

The signal processor 32 generates a basic scan pulse that determines the scan period of each transmission line of the touch sensor 20, that is, the first scan pulse SP1 having a low frequency as shown in FIG. 5, and thus the touch sensor driver 36. ) Is output as a switching control signal. The signal processor 32 generates the first scan pulse SP1 for each scan period of the touch sensor 20 and supplies it to the touch sensor driver 36. In addition, the signal processor 32 calculates a touch coordinate value (XY coordinate value) using the sensing data supplied from the touch sensor 40 and supplies the touch information to the host computer 50 as touch information. The signal processor 32 adjusts the touch coordinate value (XY coordinate) based on the position information (X coordinate) of the reception line RX to which the sensing data is output and the position information (Y coordinate) of the transmission line TX to be scanned. Can be calculated.

The high frequency generator 34 generates a square wave or sinusoidal high frequency RF having a high frequency of a specific region while outputting the high frequency RF to a touch sensor driver 36 while avoiding a noise source frequency. In general, noise of the display device flowing into the touch sensor 20 from the display panel 10 of the liquid crystal display is mainly generated every time the thin film transistor TFT is turned on and off. It is fixed at every frequency (for example, 40kHz to 50kHz for VGA LCDs) or at a specific multiple of that particular frequency. In addition, power supply noise generated from the power supply unit of the display device is also generated at a specific frequency (for example, 30 kHz). Therefore, by experimentally detecting the frequencies of noise components and other noise components of the display device, the high frequency generator 34 generates a high frequency RF having a frequency (for example, 70 kHz to 80 kHz) that does not overlap with the noise frequency. Is designed to generate. In addition, the high frequency generator 34 may generate and output an optimum high frequency RF that forms a capacitance and an impedance match of the touch sensor 20 while avoiding a noise frequency. For example, when it is assumed that the capacitance of the touch sensor 20 is several pF, the high frequency generator 34 may generate and output a high frequency RF in a range of several MHz to several tens of MHz, which matches the capacitance.

The touch sensor driver 36 may generate a high frequency wave of a specific region from the high frequency generator 34 for each scan period T of each transmission line TX in response to the first scan pulse SP1 from the signal processor 32. By switching the RF, the second scan pulse SP2 into which the high frequency RF is inserted is supplied to the touch sensor 20. Accordingly, the touch sensor driver 36 transmits the second scan pulse SP2 into which the high frequency RF is inserted, as shown in FIG. 5, during each scan period T of each transmission line TX of the touch sensor 20. Supplies). The second scan pulse SP2 having the high frequency RF inserted in FIG. 5 is sequentially supplied to the plurality of transmission lines TX1 to TXn of the touch sensor 20 in response to the first scan pulse SP1. The touch sensor 20 is sequentially driven in units of transmission lines. The touch sensor 20 outputs a signal indicating whether a touch is made through the plurality of receiving lines in response to the second scan pulse SP2 including the high frequency RF supplied to each transmission line. In this case, since the second scan pulse SP2 including the high frequency RF supplied to each transmission line is induced to the plurality of receiving lines through the capacitance of the touch sensor 20, the output signal of each receiving line may also be generated. It includes high frequency (RF). Since the high frequency RF of this specific area is set by avoiding the frequency of the noise component as described above, it has a high frequency of the specific area which is distinguished from the noise component mixed in the output signal of the touch sensor 20.

The touch detector 30 amplifies the output signal of the touch sensor 20, passes through the band pass filtering and the low pass filtering, and passes the output signal around the high frequency (RF) of the specific region to effectively remove the sensing signal from which the noise component is removed. The analog sensing signal from which the noise component is removed is converted into digital sensing data and output to the signal processor 32.

To this end, the touch detector 30 may include an amplifier 42, a band pass filter (hereinafter referred to as BPF) 44, a low pass filter (hereinafter referred to as LPF) 46, and an analog-to-digital converter ( An analog-to-digital converter (ADC) 48 is provided. The amplifier 42 compares the output signal of the touch sensor 20 with a preset reference voltage and amplifies and outputs an output signal equal to or greater than the reference voltage. The BPF 44 effectively removes a noise component having a frequency different from that of the specific region by passing the high frequency RF of the specific region set by the high frequency generator 34. The LPF 46 additionally removes noise components remaining in the output signal of the BPF 44 and outputs a sensing signal having a basic waveform of the same low frequency as the first scan pulse SP1 as shown in FIG. 6. The ADC 48 converts the analog sensing signal supplied from the LPF 44 into digital sensing data and outputs it to the signal processor.

As described above, the touch sensor driving apparatus according to the present invention drives the touch sensor 20 by inserting a high frequency having a frequency of a specific region avoiding noise components into a basic scan pulse and band-passing the output signal of the touch sensor 20. By filtering and low pass filtering, noise components distinguished from high frequencies of the specific region may be effectively removed from the sensing signal. In particular, when the frequency of a specific region that avoids the noise frequency is set to a frequency that is impedance matched with the touch sensor 20, the sensing sensitivity may be further improved by increasing the sensing signal through impedance matching.

7A and 7B are diagrams illustrating signal levels of sensing data output from the ADC of the conventional touch controller and the ADC of the touch controller of the present invention.

7A and 7B illustrate sensing data output from the nine receiving lines RX1 to RX9 through the ADC of the touch controller while driving the seven transmission lines TX1 to TX7 of the touch sensors, respectively. Referring to FIG. 7A, an average value of sensing data output from the reception line RX5 of a touch point and sensing output from the reception lines RX1 to RX4 and RX6 to RX9 of a non-touch point are provided through an ADC of a conventional touch controller. Since the difference from the average value of the data is about 126, it can be seen that there is a problem that the sensing sensitivity is low, because the signal-to-noise ratio (SNR) is low due to the noise component. On the other hand, referring to Figure 7b, through the ADC of the touch controller according to the present invention, the average value of the sensed data output from the receiving line (RX5) of the touch point, and the receiving lines (RX1 ~ RX4, RX6 ~ ~ non-touch point) It can be seen that the sensing sensitivity is improved by increasing the difference from the average value of the sensing data output from RX9) to about 374. This is because the signal-to-noise ratio (SNR) is increased by effectively removing the noise component.

Table 1 below shows the average output value of the conventional touch controller and the sensing data output from the ADC of the touch controller of the present invention according to the inversion method of the liquid crystal display.

Inversion type Average Output Data of Lead-Out Circuit Signal level Noise level SNR Conventional
Column inversion 126.1 43.2 2.92 Dot inversion 103.1 33.5 3.08 Invention
Column inversion 374.3 49.4 7.58 Dot inversion 244.5 41.7 5.86

Referring to Table 1, when the display panel is driven by column inversion or dot inversion, the signal-to-noise ratio (SNR) of the average data output from the ADC of the conventional touch controller is relatively small, so that the sensing sensitivity is low. In addition, it can be seen that the sensing sensitivity is high because the signal-to-noise ratio (SNR) of the average data output from the ADC of the touch controller according to the present invention is high.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of.

10: display panel 12: data driver
14: gate driver 16: panel driver
18: timing controller 20: touch sensor
30: touch controller 32: signal processor
34: high frequency generation unit 36: touch sensor drive unit
40: touch sensing unit 42: amplifier
44: Band Pass Filter (BPF) 46: Low Pass Filter (LPF)
48: analog-to-digital converter (ADC) 50: host computer

Claims (8)

A touch sensor attached to or embedded in the display panel and integrated;
The touch sensor is driven using a second scan pulse in which a high frequency of a specific region in which a frequency of a noise component is avoided is inserted into a first scan pulse for determining a scanning period of the touch sensor, and the output signal of the touch sensor is filtered. And a touch controller configured to pass a signal having a high frequency of the specific region and detect and output sensing data from the high frequency signal. The method according to claim 1,
The touch controller
A high frequency generator for generating a high frequency of the specific region;
A touch sensor driver for switching a high frequency from the high frequency generator in response to the first scan pulse to supply a second scan pulse having the high frequency inserted thereto to each transmission line of the touch sensor;
Band-pass filtering the signal output through each receiving line of the touch sensor to output a high frequency of the specific region, and output the sensing signal by low-pass filtering the output signal, and converts the sensing signal into digital data A touch sensor for outputting sensing data;
And a signal processor configured to generate the first scan pulse to control the touch sensor driver and to calculate and output a touch coordinate value by combining the sensing data supplied from the touch sensor. Device. The method according to claim 2,
The touch sensing unit
An amplifier for comparing and amplifying the output signal of the touch sensor with a reference voltage and outputting the amplified signal;
A band pass filter for band-pass filtering the output signal of the amplifier and outputting a high frequency of the specific region;
A low pass filter configured to low pass filter the output signal of the band pass filter to output the sensing signal;
And an analog-to-digital converter configured to convert the output signal of the low pass filter into the digital data to output the sensing data. The method according to claim 2,
And a fundamental frequency of the sensing signal is the same as the frequency of the first scan pulse. The method according to any one of claims 1 to 4,
And a high frequency of the specific region has a frequency that forms impedance matching with capacitance of the touch sensor. Generating a high frequency of a specific region avoiding the frequency of the noise component;
Generating a first scan pulse that determines a scanning period of the touch sensor;
Switching the high frequency of the specific region in response to the first scan pulse to drive the touch sensor with a second scan pulse in which the high frequency of the specific region is inserted;
Band-pass filtering the output signal of the touch sensor to pass a signal having a high frequency of the specific region;
Outputting a sensing signal by performing low pass filtering on the band pass filtered output signal;
Converting the sensing signal into digital data and outputting sensing data;
And calculating and outputting touch coordinate values by combining the sensing data. The method of claim 6,
And a fundamental frequency of the sensing signal is equal to a frequency of the first scan pulse. The method according to any one of claims 6 and 7,
And a high frequency of the specific region has a frequency that forms impedance matching with capacitance of the touch sensor.

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