WO2013058446A1 - Capacitive touch sensor - Google Patents

Abstract

The present invention relates to a capacitive touch sensor that uses a mutual capacitance measuring technique which extracts a changed value, according to a touch motion of mutual capacitance between two electrodes intersecting on a capacitive touch sensor panel, to be impervious to noise generated in a flat panel display.

Description

Capacitive touch sensor

The present invention relates to a touch sensor attached to a flat panel display including a liquid crystal display (hereinafter referred to as LCD) and an organic light-emitting diode (hereinafter referred to as OLED). In order to extract the mutual capacitance (capacitance) between two intersecting electrodes of the capacitive touch sensor panel, the capacitive measuring method using mutual capacitance measurement method is made to be insensitive to the noise generated by the flat panel display. It relates to a capacitive touch sensor to be used.

Recently, with the revolution of the IT industry, various kinds of electronic devices have become very diverse, especially in the field of portable electronic devices such as laptops, mobile phones, and portable multimedia players (PMPs), new designs of electronic devices with new functions are pouring every day. .

In particular, a touch sensor panel is attached to a flat panel display device including an LCD and an OLED in a mobile phone or a tablet PC and used as an input device through a touch operation using a finger or a pen.

In the early touch sensor panel, resistive touch type was used. In the resistive touch sensor panel, two flexible membranes having a transparent electrode applied on the front surface are kept close at a uniform distance, and the parts to be touched are electrically connected to each other by mechanical contact. It refers to a method of finding the contacted position using a touch sensor circuit. However, in the resistive touch sensor panel, mechanical movements are transmitted to the touch sensor panel and the flat panel display device by a touch operation, thereby reducing the lifespan of the devices.

In recent years, capacitive touch sensor panels that remove mechanical movement by using tempered glass instead of flexible thin films have been increasingly used to compensate for these disadvantages. In the capacitive touch sensor panel, place a glass plane for the touch sensor panel on the flat panel display and attach tempered glass on it. Even if you touch it with a finger or a pen on the tempered glass, the glass plate and flat panel for the touch sensor panel under the tempered glass No mechanical movement is transmitted to the display device. Therefore, the capacitive touch sensor panel does not have the disadvantage of reducing the life of the display device even by repeated touch operations.

Transparent electrodes are disposed on the glass plate for the capacitive touch sensor panel. The capacitive touch sensor panel is divided into a method of measuring self capacitance and a method of measuring mutual capacitance. Initially, a method of measuring its own capacitance was mainly used, and as the number of touches increased to three or more, a method of measuring mutual capacitance was increasingly used.

Finding the touched position in the capacitive touch sensor panel is possible by connecting the touch sensor circuit and measuring the self capacitance between each lead and the ground or the mutual capacitance between two crossing conductors. The reference node (ground) of the self capacitance corresponds to the LCD common electrode (VCOM) terminal in the case of a liquid crystal display (LCD).

However, in the capacitive touch method for measuring mutual capacitance, the signal-to-noise ratio (SNR) is considerably small due to the common electrode (VCOM) noise generated in a flat panel display such as an LCD. Therefore, in this capacitive touch method, it is essential to reduce the influence of the VCOM noise generated in the flat panel display. In addition, in the capacitive touch system, the capacitance must be measured, and therefore, a charge amplifier is mainly used at the first stage of the receiving circuit unit.

As described above, various methods for reducing the influence of self-generated common electrode (VCOM) noise in flat panel displays such as LCDs have been attempted.

(1) Chopper method,

(2) increasing the amplitude of the touch sensor panel drive signal;

(3) Method of adjusting frequency of touch sensor panel drive signal,

(4) A method of operating the touch sensor panel only during the time period when the flat panel display is not operated.

First, the chopper method applies a signal identical to the driving signal applied to the capacitive touch sensor panel to the receiving circuit unit, passes the same signal as the driving signal through the charge amplifier output signal and the chopper circuit, and the output signal thereof. By passing through the integrator or low-pass filter to reduce the effect of the common electrode (VCOM) noise at the integrator or low-pass filter output.

Second, the method of increasing the amplitude of the driving signal is a method of increasing the amplitude of the driving signal of the touch sensor panel to increase the signal-to-noise ratio (SNR) of the output signal of the receiving circuit unit to one or more.

Third, a method of adjusting the frequency of the touch sensor panel driving signal is to find a frequency having a small noise level on the frequency spectrum of the common electrode (VCOM) noise and to adjust the driving signal frequency to the frequency.

Fourth, in the method of operating only the time interval in which the flat panel display is not operated, the VBLANK until the screen of one frame is transmitted and the next screen is transmitted in the flat panel display does not generate the common electrode (VCOM) noise. The touch sensor circuit is operated only in the section.

On the other hand, it is necessary to first understand the structure of the LCD before explaining the main technical idea of the present invention. Currently used LCDs can be divided into VA (vertical alignment) and IPS (in-plane switching).

In the VA method, as shown in FIG. 1, the common electrode (VCOM) node is a capacitive touch sensor because the common electrode (VCOM) node is located on the upper glass substrate of the LCD located far from the backlight of the LCD among the two glass substrates constituting the plane LCD. The distance from the panel electrode is close.

In the IPS method, as shown in FIG. 2, since the common electrode VCOM node is located on the lower glass substrate of the LCD located close to the backlight, it is far from the capacitive touch sensor panel electrode. However, in the IPS method, since there is no conductive plane between the touch sensor panel and the LCD, the touch sensor panel electrode is directly exposed to a video signal (analog gray scale signal) driven by a TFT or a source driver.

The pixel of the LCD is composed of two electrodes and a liquid crystal and a color filter positioned between the two electrodes. These electrodes are made of a transparent electrode made of indium tin oxide (ITO) or the like on a glass plate. As shown in FIG. 3, an analog signal indicating a gray scale transmitted from a source driver through a TFT switch is applied to one of the two electrodes, and the other electrode is common to all the pixels. DC 5V voltage is applied. This common node is called a common electrode (VCOM) node. Since the capacitive touch sensor panel usually does not have a ground or reference electrode as the touch sensor panel itself, and is directly attached to the LCD device, the LCD common electrode (VCOM) node acts as a reference voltage node or ground of the capacitive touch sensor panel.

Referring to FIG. 3, gate driver lines G1 to G3 corresponding to each row or column in the LCD are sequentially driven according to positions. Each gate driver line is connected to a large number of gate nodes of a TFT switch (about 6000 in full HD). As a result, a relatively large capacitance of tens of pF is connected to one gate driver line. The gate driving signal maintains a value of about -5V when off and about + 25V when on. As a result, significant voltage fluctuations occur in the rising and falling edge times of the gate driver signal over a short period of time, resulting in a significant displacement current (C · dV / dt) I _N (t). It flows to the LCD common electrode (VCOM) node through the gate capacitance (C _GD ) and the liquid crystal capacitance (C _LC ) of the TFT.

FIG. 4 is a diagram illustrating a noise generation mechanism of the common electrode VCOM by the driving signal of the gate driver line illustrated in FIG. 3. Referring to this, the displacement current I _N (t) passes through the common electrode (VCOM) plane composed of the transparent electrode and then flows through the output resistance (RO) of the LCD common electrode (VCOM) driver circuit (driver). The (VCOM) noise waveform is displayed in an impulse form at the rising edge and falling edge times of the gate driver signal.

However, as shown in FIG. 3, the gate driver signal sequentially moves to the next gate driver line. In all gate driver lines, the common electrode VCOM noise has an impulse waveform in each of the rising and falling edges of the gate driver signal. . Therefore, the common electrode VCOM noise has a periodic waveform with respect to time, and the period is equal to a time interval in which each gate driver signal is maintained at a high level. The period of the common electrode VCOM noise corresponds to half of the gate driver clock signal period.

As described above, the capacitive touch method is divided into a method of measuring self capacitance and a method of measuring mutual capacitance. The self capacitance, when touched, adds the capacitance between the human body and the earth and increases its value, thereby determining whether or not there is a touch. In addition, its capacitance is relatively insensitive to LCD common electrode (VCOM) noise because it has a relatively large capacitance value of about 50 pF or more.

However, in the capacitive touch method, when the number of simultaneously touching positions increases to three or more, mutual capacitance should be measured. When there is a touch operation, the mutual capacitance value decreases. By the way, the mutual capacitance is usually about 1pF, as shown in FIG. 7 of the present invention, the self capacitance (C _SXj ) between the touch sensor panel electrode connected to the charge amplifier and the LCD common electrode (VCOM). Through this, common electrode (VCOM) noise appears at the output of the charge amplifier.

Although the common electrode (VCOM) noise amplitude is smaller than the amplitude of the touch sensor panel drive signal, the self capacitance (C _SXj ) is usually 50 times or more than the mutual capacitance (Cm _ij ). The noise ratio (SNR) is often less than one. In such a situation, in order to overcome the LCD common electrode (VCOM) noise and stably determine the touch in the mutual capacitance measurement method, a noise reduction type touch sensor is essential.

The technical problem to be solved by the present invention is to provide a capacitive touch sensor that can be reliably determined whether the touch is present and the touched position while being insensitive to self-generated noise of the flat panel display.

The capacitive touch sensor according to the present invention for achieving the technical problem is provided with a flat panel display for displaying an image, and a touch sensor panel located on the inside (on-cell) of the flat panel display (in-cell) A capacitive touch sensor, comprising: a drive signal generator configured to generate a time periodic output signal for a plurality of times to be applied to the touch sensor panel and the receiver circuit, among the output signals of the drive signal generator; And a driver for generating a driving signal of the touch sensor panel using a part, and a receiving circuit unit for processing noise from the signals received from the touch sensor panel using the output signals.

The present invention for achieving the technical problem is a drive signal generation for generating a periodic output signal for a plurality of times by a flat panel display, a touch sensor panel coupled to the flat panel display, the clock signal for driving the gate of the flat panel display The driver may include a driver for driving the touch sensor panel using some of the output signals of the driving signal generator, and a reception circuit unit for receiving a signal transmitted from the touch sensor panel to reduce noise.

The present invention for achieving the technical problem is to generate a plurality of periodic output signals (Vsrc, Vchop, Vrst) by a flat panel display, a touch sensor panel coupled to the flat panel display, the clock signal driving the gate of the flat panel display A driver for driving the touch sensor panel using a driving signal generator, some of the output signals Vsrc and Vchop of the drive signal generator, and a signal received from the touch sensor panel to receive a common electrode of the flat panel display. And a AC coupling circuit for transmitting the common electrode (VCOM) noise waveform to the receiving circuit unit.

According to an aspect of the present invention, there is provided a flat panel display for displaying an image, and a capacitive touch sensor including a touch sensor panel on or inside the flat panel display, the clock signal driving a gate of the flat panel display. And a driving signal generator for generating a plurality of periodic output signals Vsrc, Vchop, and Vrst, and a plurality of output terminals, each of the plurality of output terminals being a center of the Y electrodes of the touch sensor panel. A driver having a one-to-one correspondence and electrically connected to each other, having a plurality of input terminals, wherein each of the plurality of input terminals correspond to one-to-one correspondence with one of the X electrodes of the touch sensor panel and is electrically connected thereto. Each of the plurality of input terminals of the circuit section and the receiving circuit section includes a charge amplifier of the charge amplifier existing in the receiving circuit section. The inverting input terminal is electrically connected in one-to-one correspondence, and a mutual capacitance Cm _ij is formed between the i-th Y electrode and the j-th X electrode of the flat panel display and the touch sensor panel.

According to an aspect of the present invention, a capacitive touch sensor for driving a flat panel display and a touch sensor panel coupled with the flat panel display includes a plurality of periodic output signals by a clock signal for driving a gate of the flat panel display. A driver for driving the touch sensor panel using a generated driving signal generator, a part of the output signals of the driving signal generator, and a signal transmitted from the touch sensor panel to receive a common electrode VCOM of the flat panel display. A receiving circuit unit for reducing the influence of noise, and an analog-to-digital converter to which the output signal of the receiving circuit unit is transmitted is characterized in that it is included in one integrated circuit chip.

In the capacitive touch sensor using the mutual capacitance measuring method according to the present invention, the influence of the self-generated common electrode (VCOM) noise in the flat panel display is hardly seen in the output signal of the touch sensor receiving circuit. Therefore, it is possible to maintain the digital signal level without increasing the amplitude of the touch sensor panel driving signal, thereby reducing the power consumption of the touch sensor chip and eliminating the high voltage driving circuit, thereby reducing the manufacturing cost of the touch sensor chip.

In addition, the touch sensor circuit may be operated not only in the blank (VBLANK) time interval in which the flat panel display device is operated but also in all time domains in which the flat panel display device operates, thereby increasing the touch sensing speed.

1 is a view showing a cross-section LCD of the VA (Vertical Alignment) method according to the prior art, Figure 2 is a view showing the LCD cross section of the IPS (In Plane Switching) method.

3 is a diagram illustrating a sequential driving operation of the gate driver line illustrated in FIGS. 1 and 2.

FIG. 4 is a diagram illustrating a noise generation mechanism of the common electrode VCOM by the driving signal of the gate driver line illustrated in FIG. 3.

5 is a view showing the layout of the capacitive touch sensor using the mutual capacitance measurement method according to the present invention.

FIG. 6 is a diagram illustrating a layout of the touch sensor panel shown in FIG. 5.

FIG. 7 is a diagram illustrating a structure of a capacitive touch sensor using a mutual capacitance measurement method in which a charge amplifier is connected to the first stage of a receiving circuit unit.

FIG. 8 is a diagram illustrating noise generated at a common LCD common electrode VCOM and a clock GCLK signal of a gate driver line.

FIG. 9 is a diagram illustrating a frequency spectrum of common electrode (VCOM) noise illustrated in FIG. 8.

FIG. 10 is a view illustrating the same effect of the common electrode (VCOM) noise appearing on the final output of the receiving circuit unit at any touch sensor panel position by synchronizing the output signal of the driving signal generator Vsrc with the common electrode (VCOM) noise. to be.

FIG. 11 is a diagram illustrating a touch sensor circuit in which an analog multiplier synchronized to a receiving circuit unit is applied and uses a Vsrc signal synchronized to common electrode (VCOM) noise.

12 is a diagram illustrating a touch sensor circuit using two analog multipliers synchronized to a receiving circuit unit and using Vsrc and Vchop signals synchronized to common electrode (VCOM) noise.

FIG. 13 is a diagram illustrating signal waveforms used in the synchronized analog multiplier shown in FIG. 12, wherein the periods of the Vchop and Vrst signals are twice the noise period T _N of the common electrode VCOM and the frequency of the Vsrc signal is the common electrode. (VCOM) This is the case of three times the inverse of the noise period.

FIG. 14 is a diagram illustrating a signal waveform used in the synchronized analog multiplier shown in FIG. 12, wherein the periods of the Vchop and Vrst signals are four times the common period VCOM noise period T _N , and the frequency of the Vsrc signal is the common electrode. (VCOM) This is the case of 3.5 times the inverse of the noise period.

FIG. 15 is a view showing various combinations of the Vchop signals used in the synchronized analog multiplier shown in FIG. 12, and a Vrst signal for resetting the charge amplifier and the integrator.

FIG. 16 is a diagram illustrating a touch sensor circuit to which a technique of compensating self-generated noise of a flat panel display through an AC coupling is applied to a reception circuit unit.

FIG. 17 is a diagram illustrating a SPICE simulation result of the circuit illustrated in FIGS. 11, 12, and 16.

18 is a diagram illustrating a touch sensor circuit to which all of self-generated noise reduction techniques of a flat panel display according to the present invention are applied.

19 is a diagram illustrating a SPICE simulation result of the circuit disclosed in FIG. 18.

20 is a view illustrating a touch sensor circuit in which a circuit for increasing the output dynamic range of the touch sensor receiving circuit unit according to the present invention is added.

21 is a diagram illustrating a SPICE simulation result of the circuit of FIG. 20.

22 is a view showing an embodiment of a drive signal generation unit according to the present invention.

FIG. 23 is a diagram illustrating a gate driving clock signal GCLK during one frame time period of a flat panel display.

24 is a diagram illustrating a clock-data recovery circuit without a reference clock input or a frequency fixed loop without a reference clock input.

25 is a diagram illustrating a simulation result of a frequency fixed loop without a reference clock input.

FIG. 26 is a diagram illustrating a driving signal Vsrc and a reset signal Vrst generated in the circuit of FIG. 22.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be embodied in a form that is not combined with other components or features. In addition, some of the components and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment, or may be replaced with corresponding components or features of another embodiment.

In the description of the drawings, procedures or steps that may obscure the technical gist of the present invention are not described, and procedures or steps that can be understood by those skilled in the art are not described. In addition, the same code | symbol is attached | subjected about the same part through the specification.

Specific terms used in the embodiments of the present invention are provided to help the understanding of the present invention, and the use of the specific terms may be changed to other forms without departing from the technical spirit of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced.

5 is a view showing a structure of a capacitive touch sensor using a mutual capacitance measurement method according to the present invention.

Referring to FIG. 5, the capacitive touch sensor using the mutual capacitance measuring method according to the present invention includes a flat panel display 100 to which a touch sensor panel 200 is attached, and the flat panel display 100. The touch sensor circuit includes a driver 300, a driving signal generator 400, and a receiver circuit 500 connected to an input / output terminal of the controller.

In the present embodiment, the touch sensor panel 200 is attached to the upper portion of the flat panel display 100. However, the present invention can be used in a form in which the touch sensor panel is in-cell inside the flat panel display in addition to the on-cell form.

In addition, the touch sensor circuit is a touch sensor using a driving clock generator 400 for generating a periodic signal to be applied to the touch sensor panel 200, Vsrc and Vchop which are output signals of the driving signal generator. The driver 300 converts the driving signal Vdrv, which is a signal for driving the panel 200, and the reception circuit unit 500, which processes a signal received from the touch sensor panel 200.

The capacitive touch sensor using the mutual capacitance measuring method according to the present invention configured as described above has a touch sensor panel (to remove the noise effect of the common electrode VCOM (see FIG. 3) generated in the flat panel display 100). The driving signal Vdrv applied to the 200 and the output signal Vsrc generating the same are a periodic signal such as a sine wave or a square wave, and the frequency of the output signal is equal to the reciprocal of the noise period reciprocal of the common electrode VCOM of the flat panel display. The noise effect is reduced in the receiving circuit unit 500 by making an integer multiple or a positive integer +0.5 times and compensating for the noise effect of the common electrode VCOM.

The noise waveform of the common electrode VCOM in the flat panel display 100 is synchronized with the gate driver signal of FIG. 3, and the gate driver signal is generated from the gate driving clock signal GCLK of the flat panel display. The driving signal Vdrv applied to) should be generated from the gate driving clock signal GCLK.

The receiving circuit unit 500 includes one charge amplifier 510 illustrated in FIG. 7 to be described later, an analog multiplier 530 illustrated in FIG. 12, a chopper circuit 540, and an integrator 520. When the integrator 520 is replaced with a low-pass filter, the low-pass filter may be configured if the frequency of Vsrc, which is the output signal of the driving signal generator of FIG. 5, is greater than the bandwidth of the low-pass filter. Performs the same function as integrator 520.

In the case where one analog multiplier 530 and one integrator 520 are used for the charge amplifier as shown in FIG. 11, the analog multiplier inputs Vsrc, which is the output signal of the driving signal generator, and Vamp, which is the output of the charge amplifier 510. Integrator 520 receives the output of this analog multiplier as an input signal.

In the case of using two analog multipliers as shown in FIG. 12, the first analog multiplier 530 receives Vsrc, which is the output signal of the driving signal generator, and Vamp, which is the output of the charge amplifier 520, and the second analog multiplier is made of the first multiplier. The output of one analog multiplier and Vchop are used as input signals, and the integrator 520 uses the output of the second multiplier as an input. For convenience of description, the second analog multiplier may use the name chopper circuit to distinguish the two from each other.

Vchop, which is an input signal of the chopper circuit, is generated by the driving signal generator 400, and its period is an even multiple of the common electrode VCOM noise period. To this end, the value of k in FIG. 22 should be a positive integer.

In addition, the reset signal Vrst is generated in the driving signal generator 400 and used to reset the outputs of the charge amplifier 510 and the integrator 520 of the receiver circuit 500. In this case, the reset signal Vrst is generated using Vchop, which is an output signal of the driving signal generator.

FIG. 6 is a diagram illustrating a layout of the touch sensor panel shown in FIG. 5.

Referring to FIG. 6, a touch sensor circuit is connected to the capacitive touch sensor panel 200 to determine the presence and location of a touch by measuring mutual capacitance Cm between two conductive wires crossing each other. Here, the reference node (ground) of the self capacitance corresponds to the LCD common electrode (VCOM) terminal in the case of LCD.

7 illustrates a charge amplifier 510 connected to the touch sensor panel 200 and the receiving circuit unit 500 according to the present invention.

Referring to FIG. 7, the touch sensor panel 200 has a mutual capacitance Cm _ij connected between the i-th Y electrode Yi and the j-th X electrode Xj of the flat panel display 100 and the touch sensor panel 200. It is configured to include). Vdrv is applied to the i-th Y electrode Yi of the touch sensor panel 200, the receiving circuit unit 500 is connected to the j-th X electrode Xj, and the Y electrode Yi and the X electrode Xj are connected to each other. Self capacitances C _SYi and C _SXj exist for the flat panel display common electrode VCOM, and mutual capacitances Cm _ij exist between the Y electrode Yi and the X electrode Xj. do.

In addition, since the touch sensor panel 200 needs to measure mutual capacitance Cm _ij , a charge amplifier is mainly used in the first stage of the receiving circuit unit 500. The capacitor Cf is used as a feedback element connecting the inverting input terminal and the output terminal of the charge amplifier. In the case of using a resistor as the feedback element, the charge amplifier operates as a linear amplifier and amplifies high frequency noise. Therefore, the charge amplifier has excellent noise characteristics.

In the capacitive touch sensor using the mutual capacitance measuring method according to the present invention configured as described above, as shown in FIG. 8, the common electrode (VCOM) noise waveform generated by the flat panel display 100 has periodic characteristics with respect to time. Has 8 illustrates a case in which the common electrode VCOM noise period T _N is half of the GCLK period that is the flat panel display gate driver clock signal. By using this characteristic, the Vrst signal period used by the receiving circuit unit 500 is a positive integer multiple of the common electrode (VCOM) noise period and measured at any position (what i, j combination) of the touch sensor panel is applied to the output of the receiving circuit unit. The influence of the noise of the common electrode (VCOM) is the same and this value becomes a constant DC value irrespective of the values of i and j so that it can be easily removed.

Looking at the frequency spectrum of this noise shown in Fig. 9, each harmonic component has a high noise value every integer multiple of f _{CK which} is the inverse of the noise period T _N.

FIG. 10 is when the frequency of Vsrc, which is a signal used for generating the touch sensor panel driving signal Vdrv, is an integer multiple of the inverse of the noise period of the common electrode VCOM, and the Vrst period is the same as the noise period. It shows that the influence of the common electrode (VCOM) noise appearing at the final output of the receiving circuit unit is the same at any position of the touch sensor panel.

Referring to FIG. 10, the frequency of Vsrc, which is a signal used to generate the touch sensor panel driving signal Vdrv of the driver 300, is three times the positive integer multiple of the common electrode VCOM noise period reciprocal f _CK . . Vsrc may use a square wave Vsrc (b) in addition to a sine wave Vsrc (a). Initially, the output value (V) of the receiving circuit unit 500 measured by integrating the common electrode VCOM noise for one cycle time from the X1 line with respect to the time when the driver 300 drives the Y2 line of the touch sensor panel 200 of FIG. 6. _{N (X1.Y2)} and the time when the driver 300 drives the Y3 line of the touch sensor panel 200 of FIG. 6 after the passage of time, integrates the common electrode (VCOM) noise for one cycle time on the X1 line. The output values V _{N (X1.Y3)} of the receiving circuit unit 500 measured by the same are the same. This is because the period of Vrst is a positive integer multiple of the period of the common electrode VCOM noise, and the frequency of the Vsrc signal is an integer multiple of the reciprocal of the noise period inverse, so that the output of the chopper is at the same point in one period of the common electrode VCOM noise. This is because you will always get the same value. Ignoring the delay time generated when the driving signal of the touch sensor panel 200 propagates the Yl line in FIG. 6 and all the Xl in FIG. 6 through its capacitance from the common electrode VCOM plane in the touch sensor panel 200. When the common electrode VCOM noise induced in the line is the same, the influence of the common electrode VCOM noise on the output signal of the receiving circuit unit 500 is the same. That is, the output voltage of the touch sensor receiving circuit unit 500 which is an influence of the common electrode VCOM noise measured by integrating the common electrode VCOM noise for one cycle time at the Xj line when the driving signal is applied to the Yi line of FIG. 6. The V _{N (Xj.Yi)} value has the same value for all i and j values.

On the other hand, chopper techniques are commonly used to measure weak signals combined with large noise. In the present invention, a second chopper circuit is added to a general single chopper technique to use a dual chopper method, and the chopper signal Vchop period of the second chopper circuit is made to be a positive integer multiple of the common electrode VCOM noise period. This is different from the capacitive touch sensor circuit using different mutual capacitance measurement methods. In the present invention, since the chopper is used only in the reception circuit unit 500 without using a chopper for the driver 300, the chopper driving signal used for the driver 300 and the chopper driving signal used for the reception circuit unit 500 are close to a mixed structure. Functions like a chopper because they all use the same signal (Vsrc). Therefore, the method is called a chopper method or an analog multiplier method and they can be used interchangeably in the name. Even so, in the following description, the first analog multiplier is an 'analog multiplier', and the second analog multiplier is a 'chopper circuit'. Used separately.

FIG. 11 is a diagram illustrating a touch sensor circuit in which an analog multiplier is applied to the reception circuit unit 500 and uses a Vsrc signal having a frequency of a positive integer multiple of a common electrode (VCOM) noise period reciprocal or a positive integer +0.5 times.

Referring to FIG. 11, in the capacitive touch sensor using the mutual capacitance measuring method according to the present invention, the driving signal Vdrv is applied to the i th Y electrode Yi of the touch sensor panel 200 and the j th X electrode. The charge amplifier 510 is connected to (Xj). C _SYi and C _SXj are self capacitances to the common electrode (VCOM) plane of the Yi and Xj electrodes, respectively, and Cm _ij is the mutual capacitance between the Yi and Xj electrodes. An analog multiplier 530 and an integrator 520 are connected in series to an output terminal of the charge amplifier 510. At this time, the common electrode VCOM noise is input to the charge amplifier 510 through its capacitance C _SXj .

FIG. 12 illustrates a frequency in which one analog multiplier 530 and another chopper circuit 540 are applied to the receiving circuit unit 500 and a positive integer multiple or a positive integer plus 0.5 times the reciprocal of the common electrode VCOM noise period. FIG. 13 is a diagram illustrating a touch sensor circuit using a Vchop signal having an even multiple of Vsrc and a common electrode (VCOM) noise period, and FIGS. 13 and 14 illustrate signal waveforms used in the touch sensor circuit shown in FIG. 12. to be.

Referring to FIG. 12, in the single chopper receiving circuit (see FIG. 11), as the frequency of the chopper driving signal Vsrc increases, the influence of the common electrode VCOM noise appearing on the output of the receiving circuit unit 500 may be reduced. have. However, if the frequency of Vsrc is increased, the phase of the two signals multiplied by each other in the chopper is different due to the delay time generated when the signal is transmitted through the transparent electrode of the touch sensor panel. (500) The output signal value may decrease. However, in order to minimize the effect of the common electrode (VCOM) noise in the touch sensor output signal while maintaining the frequency of Vsrc low, the present invention proposes a dual chopper method. In this method, the chopper operation of the dual structure is performed by additionally using a digital signal called Vchop whose period is an even multiple of the common electrode VCOM noise period.

Referring to FIG. 13, the waveform of the Vchop signal is twice the common electrode VCOM noise period and the frequency of the Vsrc signal is three times the inverse of the common electrode VCOM noise period. During one cycle of the common electrode VCOM noise, Vchop is '+1', the driving signal Vdrv of the touch sensor panel becomes + Vsrc, and the + Vsrc signal is also used as a chopper driving signal in the receiving circuit unit. During the next period of the common electrode VCOM noise, Vchop becomes '-1', the driving signal Vdrv of the touch sensor panel becomes + Vsrc, and the + Vsrc signal is also used as a chopper driving signal in the receiving circuit. . Here, '+1' and '-1' are used to represent the effect of phase inversion of the Vchop signal. Therefore, the Vsrc signal is always input to the integrator 520 of the receiving circuit unit 500 by the chopper operation, but the common electrode VCOM noise is received in a direction canceled with each other during two periods of the common electrode VCOM noise. It is input to the integrator 520 of the circuit unit 500. The charge amplifier and the integrator of the receiving circuit unit 500 are reset every two periods of the noise of the common electrode VCOM by the reset signal Vrst and correspond to the two adjacent reset operations of the charge amplifier and the integrators 510 and 520. Integral operation is performed for two periods of the time of the common electrode (VCOM) noise. The reset signal Vrst is synchronized with the chopper signal Vchop and has the same period. In the dual chopper method, the common electrode (VCOM) noise waveform is periodically repeated, and the common electrode (VCOM) for one period of the common electrode (VCOM) noise in the receiving circuit unit 500 by the operation of the chopper circuit. ) Minimize the influence of the common electrode (VCOM) noise at the output of the receiving circuit unit 500 by adding the influence of noise and subtracting the influence of the common electrode (VCOM) noise during the next period of the common electrode (VCOM) noise. That's the way.

In FIG. 13, the frequency of the Vsrc signal is an integer multiple (3 times) of the inverse of the common period (VCOM) noise period. However, when the frequency of the Vsrc signal is a positive integer +0.5 times (3.5 times) of the inverse of the common electrode (VCOM) noise period as shown in FIG. 14, the Vsrc signal of the Vsrc signal applied for one period of the common electrode (VCOM) noise is applied. The phase and the phase of the Vsrc signal applied during another cycle time adjacent to the one cycle time have a difference of 180 Hz. Therefore, when the frequency of the Vsrc signal is a positive integer +0.5 times the inverse of the common electrode (VCOM) noise period, the analog multiplier 530 and the integrator (even if the Vchop signal is always kept at a DC state of '+1'). By operation of the operation 520, the Vsrc signal component is added in the same phase for two periods of the common electrode VCOM noise, and the common electrode VCOM noise component is added for the two periods of the common electrode VCOM noise. Offset each other. Maintaining the Vchop signal only at '+1' is equivalent to not using the chopper circuit 540 of FIG. 12 driven by the Vchop signal, which is a frequency inverse of the common electrode (VCOM) noise period. When the positive integer of +0.5 times, the single chopper circuit configuration of FIG. 11 achieves the same effect as the dual chopper circuit of FIG. If the period of the Vchop signal and the Vrst signal is four times (FIG. 14) or a multiple of 4 instead of twice the common electrode (VCOM) noise period, the frequency of the Vsrc signal is the common electrode (VCOM). In the case of a positive integer multiple of the noise period reciprocal or a positive integer +0.5 times, the influence of the common electrode VCOM noise may be canceled by using the dual chopper circuit structure of FIG. 12. To this end, the value of k in FIG. 22 should be even.

Therefore, even when the frequency of the Vsrc is relatively low, the influence of the common electrode (VCOM) noise at the output of the receiving circuit unit can be made very small. Even when the period of the Vchop signal is an even multiple of four or more times the common period VCOM noise period, the reset period may be the same as the period of the Vchop signal. In this case, the operating time of the charge amplifier and the integrator in the receiving circuit is also equal to the period of the Vchop signal.

15 shows a case where the period of the Vrst signal, which is the reset signal of the charge amplifier and the integrator of the receiver circuit unit, and the Vchop signal, which is the chopper signal, is four times the noise period of the common electrode (VCOM). It can be configured to have various different combinations (++-,-++-, +-+, etc.). In this case, the data throughput of the touch sensor circuit is twice as slow as the period of the Vrst signal and the Vchop signal is twice the noise period of the common electrode (VCOM), but the integration time is doubled. As a result, the signal-to-noise ratio (SNR) of the touch sensor circuit output signal is increased by about 3 dB. In this case, the chopper operation is performed in the case where the frequency of Vsrc, which is the output signal of the driving signal generator, is a positive integer multiple of the common electrode (VCOM) noise cycle reciprocal or a positive integer +0.5 times. Reduce the impact.

In addition to the above method, in the present invention, in order to increase the signal-to-noise ratio of the charge amplifier output signal Vamp without increasing the amplitude of the touch sensor panel driving signal Vdrv to a very large value, the common electrode VCOM having self-generated noise information of the flat panel display is used. A method of extracting a voltage waveform and applying the waveform to a touch sensor receiver circuit is proposed.

FIG. 16 is a diagram illustrating a touch sensor circuit to which a common electrode (VCOM) noise compensation technique is applied to a receiving circuit.

In the LCD, the common electrode (VCOM) voltage waveform has a form in which an impulse noise waveform is added based on a DC voltage value (for example, 5V) (see FIG. 8).

Referring to FIG. 16, the charge amplifier of the receiving circuit unit 500 according to the present invention has one capacitance C _C because the input common mode voltage is different from the DC voltage of the common electrode VCOM of the flat panel display. And a common electrode (VCOM) noise waveform is extracted using an AC (capacitive) coupling method in which two resistors R _C1 and R _C2 are connected in parallel, and the extracted waveform VCOMC is applied to the touch sensor receiving circuit unit 500. A non-inverting input terminal of the charge amplifier 510 and an analog multiplier 530 connected to the charge amplifier output terminal. In FIG. 16, in order to faithfully extract the noise waveform of the common electrode VCOM through the AC coupling method, C _C · (R _C1 || R _C2 ), which is a time constant of the AC coupling circuit, is defined as VCOM) must be much larger than the inverse of the maximum frequency component of the noise waveform. When the common electrode (VCOM) noise compensation method of FIG. 16 is performed, the charge amplifier output signal Vamp is given by the following equation.

Equation 1

Here, VCOMC is a signal extracted from the VCOM signal through an AC coupling method. The DC level is different from VCOM, but the AC component is the same signal as VCOM. Since VCOM is not completely removed in Equation 1, VCOMC is applied to the reference voltage terminal of the input signal connected to the charge amplifier output terminal of the two input signals of the analog multiplier connected to the charge amplifier output in the touch sensor receiving circuit unit 500. By applying a voltage, the (Vamp-VCOMC) signal and the Vsrc signal are multiplied with each other in the analog multiplier 530. As a result, the touch sensor receiving circuit 500 may remove the influence of VCOM, the noise generated by the flat panel display itself.

FIG. 17 is a diagram illustrating a SPICE simulation result of the circuit illustrated in FIGS. 11, 12, and 16.

In order to observe only noise components, the driving signal of the touch sensor panel 200 of the driver 300 is set to zero. The period TN of the common electrode (VCOM) noise used in the simulation is 60.9 ms, and the integrator output value is obtained by performing the simulation for the two periods of time (2TN) in all three cases (Figs. 11, 12, and 16). Was compared.

The period of Vchop, which is the driving signal of the chopper circuit 540 of FIG. 12, is twice the noise period TN of the common electrode VCOM. The charge amplifier and integrator reset signal, Vrst, was set to zero to turn off the reset switch of the charge amplifier and integrator.

The parameters used in the SPICE simulation are _CpSXj and _{CSYi, which} are the capacitances of the X and Y electrodes, respectively, 100pF, mutual capacitance Cm _ij is 1pF, the feedback capacitor C _F of the charge amplifier is 3pF, and the integrator resistor R _I and the capacitor are C _I is 440kΩ and 40pF, respectively.

The capacitor C _C used in the AC coupling circuit of FIG. 16 is 500 nF and both R _C1 and R _C2 are 200 kΩ. The frequency of the first analog multiplier driving signal, Vsrc, is about 368kHz, 23 times the odd number of the common electrode (VCOM) noise period (T _N ). The amplifier used in the charge amplifier and integrator is an ideal op amp with a voltage gain of 100. The analog multiplier uses the behavior model described by Verilog-A.

Figure 17 shows the SPICE simulation waveforms for the three techniques. The final output values of the receiving circuit portion of the circuits of Fig. 10 (Single chopper), Fig. 12 (Dual chopper) and Fig. 16 (Common Electrode (VCOM) Noise Compensation) are 8.82 mV, 0.06 mV, and -9.19 mA, respectively. In this simulation condition, the common electrode (VCOM) noise compensation technique (see FIG. 16) has the best noise characteristics, and the dual chopper technique (see FIG. 12) is next superior.

18 is a touch sensor circuit to which all of the common electrode (VCOM) noise reduction techniques according to the present invention are applied.

The receiving circuit unit 500 includes a charge amplifier 510, an analog multiplier 530, a chopper circuit 540, and an integrator 520.

In order to compensate the common electrode VCOM noise in the reception circuit unit 500, the flat display common electrode VCOM noise signal is AC-coupled to the non-inverting input terminal of the charge amplifier and the analog multiplier 530. Of the two input signals, it is connected to the reference voltage terminal of the input signal connected to the output of the charge amplifier. The drive signal of the analog multiplier 530 is Vsrc, and the drive signal of the chopper circuit 540 is Vchop. The Vsrc and Vchop are generated by the driving signal generator 400 of FIG. 5, where Vsrc is a periodic signal in the form of a square wave or a sine wave synchronized with the common electrode (VCOM) noise waveform, and Vchop is a common electrode (VCOM) noise waveform. The period of the Vchop signal as a digital signal synchronized with the synchronous signal is an even multiple of the common electrode VCOM noise period TN. Here, the driver 300 generates a Vdrv, which is a touch sensor panel driving signal, by multiplying Vsrc and Vchop using the third chopper circuit 310.

FIG. 19 illustrates SPICE simulation results for a case in which the touch is performed in a state in which the common electrode VCOM noise is applied in the circuit of FIG.

The Cm _ij value was set to 1.0 pF when not touching and 0.9 pF when touching. The final output voltage value of the touch sensor receiver circuit is 1.53V when not touched and 1.38V when touched, and has a difference of 10% as in Cm _ij . Therefore, it can be seen that the influence of the common electrode (VCOM) noise induced from the LCD on the output of the touch sensor receiving circuit is almost eliminated. The touch sensor panel driving signal Vdrv for the simulation of FIG. 19, the second chopper driving signal Vchop, and the values of the parameters C _F , R _I , C _I , C _C , R _C1 , and R _C2 are the same as in FIG. 17.

As shown in FIG. 19, the difference between the output signal of the reception circuit unit 500 and the non-touch of the reception circuit unit 500 is small (eg, 5 to 15%), so that the dynamic range of the output signal is limited to about 1.05 to 1.15. In the capacitive touch sensor of the mutual capacitance measurement method, the output voltage of the receiving circuit is proportional to the mutual capacitance (Cm, Fig. 5), and the mutual capacitance changes only about 5 to 15% when it is touched and when it is not touched. Because it does not.

In the present invention, the feedback circuit 700 is operated when an output signal compensator 700 (see FIG. 20) is added to the reception circuit unit 500 and is not touched at an initial time such as a time immediately after the power is turned on. As a result of the operation, the receiving circuit unit 500 is calibrated so that the output signal value becomes a minimum value close to zero, and the result of calibration is stored as a digital code.

After the calibration time period is finished, the output signal compensator 700 is turned off and the reception circuit unit 500 is continuously maintained in the same state as the completion of calibration using the digital code obtained in the calibration process. Thus, when the touch is not touched after the end of calibration, the touch sensor output voltage continues to maintain the minimum value close to zero. Therefore, when touched, the gain of the receiving circuit 500 may be greatly increased so that the output voltage of the receiving circuit 500 is considerably larger than that in FIG. 19.

20 illustrates a specific circuit of the output signal compensator 700 for increasing the output dynamic range of the receiving circuit unit 500. Compensation capacitor Cm _ij for the 'add to the reception circuit, and Cm _ij' of 'compensation signal Vsrcb with the other terminal of the "one terminal connected to the reception circuit 500, the charge amplifier inverting (inverting) input terminal of the first stage and Cm _ij the Is authorized. The compensation signal Vsrcb 'is an inverted signal of Vsrc, which is the driving signal of the touch sensor panel 200, is 180 degrees out of phase with Vsrc and its amplitude is different from the amplitude of Vsrc. Cm _ij 'has a value close to Cm _ij, and usually uses a value slightly larger than Cm _ij (example 2). For example, in the case of Cm _ij '= 2Cm _ij , when the amplitude of Vsrcb' is half (0.5) of the Vsrc amplitude, the output voltage Output of the receiving circuit 500 becomes zero when not touched.

In FIG. 20, the output signal compensator 700 operates as a negative feedback circuit to adjust the amplitude of Vsrcb 'such that the output voltage Output approaches zero. The output signal compensator 700 includes a comparator 701, a successive approximation register 702, a digital analog converter DA 703, and a voltage buffer as shown in FIG. 704 and an inverter 705.

The SAR logic circuit uses the Vrst signal as the clock signal.

The resulting digital code is stored as a SAR logic circuit output during the calibration interval. After the calibration interval is over, the SAR logic input clock is stopped to keep the SAR logic output digital code determined during the calibration interval. Therefore, the amplitude of Vsrcb 'continues to remain the same.

According to the technical idea of the present invention, the output signal compensator 700 should be arranged in connection with the receiving circuit unit 500. There may be various methods. For example, if the touch sensor receiving circuit unit 500 is disposed one by one for every X line displayed on the touch sensor panel of FIG. 5, the output signal compensator 700 may also be arranged in a one-to-one correspondence with every receiving circuit unit 500. have. If there is a concern that the output signal compensator 700 disposed at each receiving circuit part 500 increases the semiconductor chip area and the power consumption, the output signal compensator 700 only has one receiving circuit part connected to one X line. After the connection, the Vsrcb 'signal generated by the output signal compensator 700 may be supplied to all other receiving circuits (connected to other X lines). At this time, the compensation capacitor Cm _ij 'is preferably added to every receiving circuit unit 500.

However, as described above, the output signal compensator 700 of FIG. 20 is connected to a few reception circuits of the touch sensor, and each of the generated Vsrcb 'signals is not connected to the output signal compensator 700 of FIG. 20. It can also be supplied to

21 shows a SPICE simulation result of the circuit shown in FIG. 20.

In the circuit of FIG. 20, Cm _ij 'is set to 2 pF, R _I is set to 40kΩ, and other parameters are the same as those of FIG. In the case of receiving circuit output dynamic range compensation shown in FIG. It can be seen that the dynamic range of the output signal of the receiving circuit unit 500 is greatly increased compared to 1.38 V and 1.58 V when the compensation is not performed.

Meanwhile, when the technical idea of the present invention is implemented as a semiconductor integrated circuit, it is preferable that the driver 300, the driving signal generator 400, and the receiver circuit 500 be implemented on one chip. This is the same in all embodiments of the present invention shown in FIGS. 5, 11, 12, 16, 18, and 20. It is also preferable that the analog-to-digital converter to receive and process the signal from the output signal compensator 700 or the receiving circuit unit 500 is also implemented on one chip.

Naturally, various components constituting the circuit of the present invention, for example, the driver 300, the drive signal generator 400, the receiver circuit 500, the output signal compensator 700, the RC network, the receiver circuit Any component of the analog-to-digital converter to which the output is delivered may be appropriately distributed and arranged in several integrated circuit chips according to the circuit designer's intention, which is also included in the present invention, It doesn't violate it.

According to the researchers of the present invention, when the current level of manufacturing technology of semiconductor integrated circuits and the simulation of circuit operation based on them, the integrated circuit chip can operate without a power supply voltage of less than 4V, In addition, it has been verified that the integrated circuit chip can be operated without a separate boost circuit. Then, we verified that it is possible to drive the touch sensor panel using only this integrated circuit chip.

An embodiment of the driving signal generator 400 is illustrated in FIG. 22. Hereinafter, the function of the driving signal generator 400 will be described in more detail. As described with reference to FIGS. 13 and 14, the Vsrc signal used to generate Vdrv, the touch sensor panel driving signal according to the present invention, is a positive integer or a positive integer plus 0.5 times the frequency of the common electrode (VCOM) noise period inverse. The period of Vchop, which is the driving signal of the chopper circuit 540 of the receiving circuit unit 500, and Vrst, which is the reset signal of the charge amplifier and the integrator of the receiving circuit unit, is the period of the common electrode (VCOM) noise waveform period, which is the flat display self-generated noise. It is a positive integer multiple.

Because of the noise characteristics of the common electrode VCOM noise waveform, it is difficult to generate the generation signals Vsrc, Vdrv, Vchop, and Vrst from the common electrode VCOM noise waveform. However, in the flat panel display 100 such as an LCD, as shown in FIG. 8, the gate driver clock signal GCLK is synchronized with the common electrode VCOM noise waveform. In other words, the rising and falling edge times of GCLK coincide with the impulse waveform times of the common electrode (VCOM) noise. Accordingly, the signals Vsrc, Vdrv, Vchop, and Vrst may be generated from the gate driving clock signal GCLK. However, as shown in FIG. 23, unlike the general clock signal, the GCLK signal has rising and falling edges only in an active time period for driving an image signal in one frame time period of a flat panel display. It is a clock signal and maintains a DC value of '0' or '1' in a VBLANK time interval in which the flat panel display does not drive a video signal. Therefore, when the GCLK signal is applied as an input of a general phase locked loop (PLL), the PLL is locked in an ACTIVE time interval during which the flat panel display drives the video signal, so that the frequency of the PLL output clock signal is a desired value. This is a positive integer multiple of the clock signal GCLK frequency. As shown in FIG. 8, in this embodiment, since the period of the gate driving clock signal GCLK is twice the noise period of the common electrode VCOM, the frequency of the Vsrc signal that is the output signal of the driving signal generator is increased. The common electrode VCOM may have a positive integer multiple of the inverse of the noise period or a positive integer multiple of +0.5 times.

However, in the VBLANK time interval in which the edge of the GCLK does not occur, only one of the UP or DOWN pulse signals is always kept at '1' and the other signal is always at '0' at the phase detector output of the PLL. As a result, the control voltage of the voltage controlled oscillator is changed and is not maintained at the same value as the locked state, so that the PLL is released from the locked state. Thus, in the VBLANK time interval, the output clock signal frequency of the PLL is out of a desired value so that the frequency of the periodic signals Vsrc, Vdrv, Vchop, and Vrst also differs from a desired value. It becomes difficult to remove the influence of noise.

In order to solve this problem, the gate driving clock signal (CLL) is used in this embodiment by using a clock-data recovery (CDR) circuit or a frequency-locked loop (FLL) circuit 420. GCLK) is recognized as an arbitrary data input to generate a clock signal of a constant frequency for all time intervals including VBLANK. Typical CDR and FLL circuits accept reference clock signals and data as inputs, thus increasing the cost of manufacturing touch sensors, as additional crystal oscillators are needed to provide the reference clock. To avoid this, in the present embodiment, the gate driving is performed using a reference-less CDR circuit without a reference clock input or a frequency locked loop (FLL) without a reference clock input instead of the general CDR or FLL circuit. The signals Vsrc, Vdrv, Vchop and Vrst necessary for driving and sensing the touch sensor are generated from the clock signal GCLK.

However, in order to realize the idea of the present invention, the phases of the signals Vsrc, Vdrv, Vchop, and Vrst need not be synchronized with the phase of the gate driving clock signal GCLK, and the signals Vsrc, Only the frequencies of Vdrv, Vchop, and Vrst need only be a positive integer multiple of the gate drive clock signal GCLK signal frequency or an inverse of a positive integer multiple. When the CDR circuit 420 is used in this embodiment, not only the frequency but also the phase of the signals Vsrc, Vdrv, Vchop, and Vrst are synchronized with the gate driving clock signal GCLK, but the FLL circuit 420 may be used. In this case only frequency is synchronized and phase is not synchronized. Therefore, the idea of the present invention can be realized by using the FLL circuit as well as the CDR circuit in the driving signal generation unit. The FLL circuit has no phase detection loop compared to the CDR circuit, and thus, when implemented as an integrated circuit, the FLL circuit has advantages of small chip area and power consumption and excellent loop stability.

24 is a block diagram of a reference-less CDR circuit without the reference clock input. The clock-data recovery circuit 421 without the reference clock input receives the GCLKs signal whose amplitude is reduced by passing the gate driving clock signal GCLK through the level converter 410 as the data input of FIG. 24. Generates a regular clock signal (CLK) having an integer frequency (N-fGCLK) of the highest frequency (GCLK) of N1 fGCLK in one frame time interval. .

Since the GCLK maintains a DC value in the VBLANK time interval of the frame time of the flat panel display, the clock-data recovery circuit without the reference clock using the GCLKs as a data input is a fast time (a small number of input signal edges). The clock signal having the same frequency as the GCLK must be restored. Thus, the clock-data recovery circuit without the reference clock has a double loop having two frequency detectors (FDs), coarse 423 and fine 424, which extract frequency information from the input signal GCLKs. (dual loop) structure is used. When a coarse frequency recovery loop using a coarse frequency detector (coarse FD) 423 increases the reference-less CDR output clock (CLK) starting at a low frequency and gradually increases to reach the desired frequency, a coarse lock is declared. The FC_on signal becomes '0' and the coarse frequency recovery loop is cut off. From this time, the FF_on signal becomes '1' and the fine frequency recovery loop starts to operate. The outputs of the coarse frequency recovery loop and the fine frequency recovery loop are input to the same UP / DN counter 4421, which is coupled to the most significant bit (MSB) input of the UP / DN counter. The output of the fine frequency recovery loop is connected to the least significant bit (LSB) input of the UP / DN counter. This allows the coarse frequency recovery loop to quickly follow the desired frequency and the fine frequency loop to restore the correct frequency.

As described in FIG. 23, when the CDR circuit 421 is used, not only the frequency but also the phase of the output signals Vsrc, Vdrv, Vchop, and Vrst of the driving signal generator 400 may be displayed in the gate driving clock signal. Synchronized with (GCLK). However, in order to implement the spirit of the present invention, the phases of the signals Vsrc, Vdrv, Vchop, and Vrst do not have to be synchronized with the phase of the gate driving clock signal GCLK, but the signals Vsrc, Vdrv, Vchop, The frequency of the Vsrc and Vdrv signals in Vrst is a positive integer multiple of the gate drive clock signal (GCLK) signal frequency and the frequency of the Vchop and Vrst signals is an inverse of the positive integer multiple of the gate drive clock signal (GCLK) signal frequency. do. Accordingly, the frequency lock loop (FLL, 422) without reference clock input, which is a circuit from which a phase detection loop is removed from the CDR circuit 421 without the reference clock input shown in FIG. 24, is used. The idea is feasible.

FIG. 25 shows HSPICE simulation results of a reference-less FLL without the reference clock input. Although the actual frequency of the GCLKs signal to be applied to the data input of the reference-less FLL circuit 422 is about 16 kHz (60 frame / sec), the frequency of the GCLKs signal is set to 4 MHz to reduce the simulation time. In order to reduce the simulation time, one frame time period of the flat panel display is set to 20 clock periods of the GCLK, and an active time period of driving the video signal is 16 clock periods of the GCLK. The VBLANK time interval for not driving the video signal was set as 4 clock cycles of the GCLK. 24 are waveforms of the GCLKs signal and the restored output signal CLK, which are data inputs of the reference-less FLL circuit 422, respectively. It can be seen that the frequency of the recovered output signal CLK is uniformly close to the GCLKs signal frequency in all frame time intervals including the VBLANK time interval. The reference-less FLL circuit 422 took 1200 clock cycles of the GCLKs to restore the frequency of the output signal CLK to the frequency of the GCLKs signal.

As described above, the Vchop signal, which is the driving signal of the chopper circuit 540 of the touch sensor receiving circuit unit 500, has a period in which the period is an even multiple of the noise period of the common electrode VCOM and is maintained at '+1' or '-1'. This should be the same. In the present exemplary embodiment, the period of the gate driving clock signal GCLK is twice the noise period TN of the common electrode VCOM and the duty cycle thereof is 50%. Thus, the driving signal generator shown in FIG. In this case, the period of the Vchop signal may be an integer multiple (k times) of the GCLK period.

Meanwhile, as mentioned in the foregoing description, the Vsrc signal used to generate the driving signal Vdrv of the touch sensor panel 200 may use a sine wave in addition to a square wave. The sine wave generator 470 in the driving signal generator 400 may select a clock-data recovery circuit without the reference clock input or the output signal CLK of the frequency fixed loop 420 without the reference clock input. Generate a sine wave of the frequency. The sine wave generator receives the output signal CLK having a frequency higher than that of a desired Vsrc signal, and generates and outputs a sine wave or a square wave having a frequency obtained by dividing the frequency of the output signal CLK by M times. The sine wave generator 470 includes a counter 471 for generating a sine wave, a look-up table (LUT) 472, a digital-to-analog converter (DAC) 473, and a frequency divider for dividing a frequency of a square wave into a desired frequency. 474), a multiplexer 475 for selecting one of sine waves or square waves, and the like. The LUT 472 and the DAC 473 form one numerically controlled oscillator (NCO).

The frequency of the GCLK signal is N times the frequency of the clock-data recovery circuit 421 without the reference clock input or the frequency divider 425 located in the internal feedback path of the frequency fixed loop 422 without the reference clock input. Since the multiplication is performed and the frequency division of M times is performed by the sine wave generator 470, the frequency of the Vsrc signal is N / M times the frequency of the GCLK signal. In order to realize the idea of the present invention, the frequency of the Vsrc signal should be a positive integer multiple of the common period (VCOM) noise cycle inverse of the flat panel display (f _CK = 1 / TN) or a positive integer +0.5 times. In this embodiment, referring to FIG. 8, the frequency of the Vsrc signal is equal to the common frequency VCOM noise cycle inverse f _CK is twice the gate driving clock signal GCLK frequency fGCLK of the flat panel display. It is a positive integer multiple of the GCLK signal frequency. In other words, N / M must always be a positive integer.

Vrst, a signal for resetting the output value of the charge amplifier and the integrator of the touch sensor receiver circuit 500, is synchronized with the Vchop signal. In this embodiment, as shown in FIG. To generate).

However, the waveforms shown in FIG. 15 require an additional logic circuit not shown in FIG. 22 to generate the Vchop signal when k = 2 in FIG. The level converter 410 of FIG. 22 converts the GCLK signal having a large amplitude (e.g., -5V, + 25V) into a GCLKs signal having a small amplitude of a digital level suitable for a touch sensor chip.

FIG. 26 illustrates the synchronization signals Vsrc and Vrst generated from the GCLK signal using a reference-less CDR circuit 422 without a reference clock input of FIG. 22.

The frequency of Vsrc (a) and Vsrc (b) in FIG. 26 is three times the frequency of the common electrode VCOM noise period TN inverse f _CK (6 times the GCLK frequency), and Vsrc (c) and Vsrc (d). ) Is 3.5 times the common electrode (VCOM) noise period (TN) inverse (f _CK ) (7 times the GCLK frequency). In the common electrode VCOM noise spectrum shown in FIG. 9, Vsrc (a) and Vsrc (b) correspond to a frequency band having a large noise power since the frequency is 3 · f _CK , and Vsrc (c) and Vsrc (d) are Since the frequency is 3.5 · f _CK, it corresponds to a frequency band with a small noise power. As shown in FIG. 26, the Vsrc signal is a periodic signal with respect to time, and may be a sine wave as well as a square wave.

In the above description, the technical idea of the present invention has been described with the accompanying drawings, which illustrate exemplary embodiments of the present invention by way of example and do not limit the present invention. In addition, it is obvious that any person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (30)

1. In the capacitive touch sensor having a flat panel display for displaying an image, and a touch sensor panel located on (on-cell) or in-cell (top) of the flat panel display,

   A driving signal generator for generating time periodic output signals for a plurality of times to be applied to the touch sensor panel and the receiving circuit unit;

   A driver for generating a driving signal of the touch sensor panel by using some of the output signals of the driving signal generator; And

   And a receiving circuit unit configured to process noise received from the touch sensor panel using the output signals.
2. Flat panel display;

   A touch sensor panel coupled to the flat panel display;

   A driving signal generator for generating periodic output signals for a plurality of times by a clock signal (GCLK) for driving the gate of the flat panel display;

   A driver for driving the touch sensor panel by using some of the output signals of the driving signal generator;

   Receiving circuit unit for reducing the noise by receiving the signal transmitted from the touch sensor panel; Capacitive touch sensor comprising a.
3. The method according to claim 1 or 2,

   Using the noise having a time periodic property, the receiving circuit unit is operable to reduce the influence of the noise on its output signal.
4. The method according to claim 1 or 2,

   And capturing the noise from a common electrode (VCOM) noise waveform and then performing a compensation process on the receiving circuit unit.
5. The method of claim 4, wherein

   The noise waveform is a voltage waveform between the common electrode (VCOM) and a common ground (common ground).
6. The method of claim 5,

   The common ground is a capacitive touch sensor, characterized in that the ground terminal of the driving circuit for driving the panel of the flat panel display and the ground terminal of the touch sensor circuit is shorted with each other.
7. The method according to claim 1 or 2,

   The signal Vsrc of one of the output signals of the driving signal generator is characterized in that the frequency is a positive integer multiple of the inverse of the common electrode (VCOM) noise period or a positive integer +0.5 times.
8. The method according to claim 1 or 2,

   The noise waveform is a capacitive touch sensor, characterized in that the transfer to the receiving circuit through the RC network including a resistance and capacitance.
9. The method of claim 8,

   The transfer is the capacitive touch sensor, characterized in that consisting of the input terminal of the amplifier present in the receiving circuit portion.
10. The method of claim 8,

    The time constant of the RC network is larger than the inverse of the maximum frequency component of the noise waveform of the common electrode (VCOM) capacitive touch sensor.
11. The method of claim 1,

    At least one of the output signal of the driving signal generation unit of the capacitive touch sensor or the signal applied to the receiving circuit unit is generated using the gate driving clock signal GCLK of the flat panel display; Touch sensor.
12. The method according to claim 1 or 2,

    Capacitive touch sensor, characterized in that one of the output signal of the drive signal generator is a sine wave (square wave) or square wave (square wave).
13. The method of claim 2, wherein the receiving circuit unit,

    A charge amplifier receiving a signal transmitted from the touch sensor panel;

    An analog multiplier for multiplying one of the output of the charge amplifier and the output of the driving signal generator;

    A chopper circuit for multiplying the other of the output of the analog multiplier and the output of the drive signal generator; And

    And a low-pass filter configured to pass only a low frequency band signal from an integrator integrating the output of the chopper circuit or an output signal of the chopper circuit.
14. The method of claim 2,

    And the noise is reduced by two multiplication operations performed by the receiving circuit unit.
15. Flat panel display;

    A touch sensor panel coupled to the flat panel display;

    A driving signal generator configured to generate a plurality of periodic output signals Vsrc, Vchop, and Vrst based on a clock signal driving the gate of the flat panel display;

    A driver for driving the touch sensor panel by using some of the output signals Vsrc and Vchop of the driving signal generator;

    Receiving circuit unit for receiving the signal transmitted from the touch sensor panel to reduce the influence of the common electrode (VCOM) noise of the flat panel display;

    An AC coupling circuit transferring the common electrode VCOM noise waveform to the receiving circuit unit; Capacitive touch sensor comprising a.
16. A capacitive touch sensor comprising a flat panel display for displaying an image and a touch sensor panel on or inside the flat panel display;

    A driving signal generator configured to generate a plurality of periodic output signals Vsrc, Vchop, and Vrst based on a clock signal driving the gate of the flat panel display;

    A driver having a plurality of output terminals, each of the plurality of output terminals being electrically connected in a one-to-one correspondence with one of the Y electrodes of the touch sensor panel;

    A receiving circuit unit having a plurality of input terminals, each of the plurality of input terminals being electrically connected in a one-to-one correspondence with one of the X electrodes of the touch sensor panel;

    Each of the plurality of input terminals of the receiving circuit unit is electrically connected in one-to-one correspondence with an inverting input terminal of the charge amplifier existing in the receiving circuit unit.

    Capacitive touch sensor (Cm _ij ) is formed between the flat panel display and the i-th Y electrode and the j-th X electrode of the touch sensor panel.
17. The method according to claim 15 or 16,

    Capacitive touch is characterized in that the effect of the noise is reduced in the receiving circuit portion by the multiplication operation of the signals input to the receiving circuit portion and the subsequent integration operation or low-pass filtering operation is performed. sensor.
18. The method according to claim 15 or 16,

    The capacitive touch sensor, characterized in that the driver includes a configuration for performing a signal multiplication operation.
19. The method according to claim 7 or 15 or 16,

     The frequency of one signal Vsrc of the output signals of the driving signal generator is set to be a positive integer multiple of the inverse of the common electrode VCOM noise period or a positive integer +0.5 times,

    One signal Vchop of the output signals of the driving signal generator is

    Performs a function of a chopper signal, the period of which is an even multiple of the flat display noise period (TN),

    The chopper signal is maintained at a constant value of '+1' or '-1' for a positive integer multiple of the self-generated noise period,

    The capacitive touch sensor is a time periodic digital signal for a time at which a constant value of '+1' or '-1' is maintained for one period of the chopper signal.
20. The method of claim 15 or 16, wherein at least one signal Vrst of the plurality of periodic output signals of the drive signal generation unit,

    The period is an even multiple of the flat panel display self-generated noise period (T _N ),

    The time for which the signal level remains at "1" is much shorter than the time for which the signal level remains at "0", but it is a time periodic digital signal over time.

    The integrator or low pass filter existing in the receiving circuit section is reset in a time interval in which the signal level is maintained at '1', and performs an integral or low pass filter operation in a time interval in which the signal level is maintained at '0'. Capacitive touch sensor.
21. The method according to claim 1, 2, 15, 16,

    And the output circuit compensator for increasing the output dynamic range of the reception circuit unit.
22. The method of claim 21, wherein the output signal compensator,

    Comparator;

    Continuous approximation register;

    Digital to analog converters;

    Voltage buffer;

    Inverter; Capacitive touch sensor comprising a.
23. In the capacitive touch sensor for driving a flat panel display and a touch sensor panel combined with the flat panel display,

    A driving signal generator configured to generate a plurality of periodic output signals based on a clock signal driving the gate of the flat panel display;

    A driver for driving the touch sensor panel by using some of the output signals of the driving signal generator;

    Receiving circuit unit for receiving the signal transmitted from the touch sensor panel to reduce the influence of the common electrode (VCOM) noise of the flat panel display;

    An analog-to-digital converter to which the output signal of the receiving circuit unit is transmitted; Capacitive touch sensor characterized in that it is included in one integrated circuit chip.
24. The method of claim 23, wherein the integrated circuit chip,

    Power supply voltage is 4V or less,

    Without boosting the power supply voltage inside the integrated circuit chip,

    The touch sensor panel is driven only by the integrated circuit chip.

    The capacitive touch sensor outputs a digital signal by processing the analog signal received from the touch sensor panel with the integrated circuit chip.
25. The method of claim 4, wherein

    The common electrode (VCOM) terminal refers to a transparent electrode that is entirely coated on a flat glass plate located far from the backlight unit BLU among two flat glass plates constituting the pixel element in a vertical alignment (LCD) type liquid crystal display (VA). Capacitive touch sensor, characterized in that.
26. The method of claim 4, wherein

    The common electrode (VCOM) terminal is a common electrode pattern positioned together with a thin film transistor (TFT) on a glass plate close to a backlight unit (BLU) of two flat glass plates constituting a pixel element in an IPS (in-plane switching) type LCD. Capacitive touch sensor, characterized in that.
27. The method of claim 1, 2, 15, and 16, wherein the drive signal generation unit,

    A capacitive touch sensor comprising a reference-less CDR circuit without a reference clock input or a frequency-locked loop (FLL) without a reference clock input.
28. The method of claim 1, 2, 15, and 16, wherein the drive signal generation unit,

    Level translator;

    A reference-less CDR circuit with no reference clock input or a frequency-locked loop (FLL) without reference clock input;

    Frequency divider;

    Rising edge detector;

    Multiplexer;

    counter;

    Look-up table (LUT);

    Digital-to-analog converters (DACs);

    Chopper circuit; Capacitive touch sensor comprising a.
29. The method according to claim 1 or 2,

    The capacitive touch sensor, characterized in that the touch operation can be recognized in the time interval (ACTIVE time period) for the flat panel display to drive the video signal and the VBLANK and HBLANK time intervals for the flat panel display do not drive the video signal.
30. The receiver circuit according to claim 2 or 4,

    A charge amplifier receiving a signal transmitted from the touch sensor panel;

    An analog multiplier for multiplying one of the output of the charge amplifier and the output of the driving signal generator;

    And a low-pass filter configured to pass only a low frequency band signal of an integrator or an output signal of the analog multiplier integrating the output of the analog multiplier.

    And a frequency of one of the outputs of the driving signal generator is a positive integer +0.5 times the inverse of the common electrode (VCOM) noise period.

Images