KR20170015776A - Stylus pen and touch sensing system and driving method of the same - Google Patents

Abstract

The touch sensing system of the present invention includes a touch screen including a plurality of touch electrodes to which a touch screen driving signal is applied, and a controller for generating a pen driving signal based on the touch screen driving signal received from the touch screen, And has a transmitting stylus pen. The stylus pen includes: an amplifier for amplifying the touch screen driving signal to generate an amplified signal; a comparator for comparing the amplified signal with a reference voltage to generate a comparator output signal; And controls the reference voltage to be input to the comparator to be varied according to the measured value. The output timing of the pen driving signal is determined based on the adjustment comparator output signal according to the variation of the reference voltage, And a reference voltage varying unit for varying a reference voltage inputted to the comparator under the control of the signal processing unit.

Description

TECHNICAL FIELD [0001] The present invention relates to a stylus pen, a touch sensing system,

The present invention relates to a touch sensing system, and more particularly, to a touch sensing system capable of touch input through a stylus pen and a driving method thereof.

A user interface (UI) enables a person (user) to easily control various electronic devices as he / she wants. Representative examples of such a user interface include a keypad, a keyboard, a mouse, an on screen display (OSD), a remote controller having infrared communication or radio frequency (RF) communication function, and the like. User interface technology has been developed to enhance the user's sensibility and ease of operation. Recently, the user interface has evolved into a touch UI, a voice recognition UI, a 3D UI, and the like.

The touch UI is essential for portable information devices. The touch UI is implemented by a method of forming a touch screen on the screen of a display device. Such a touch screen can be implemented in a capacitive manner. When a finger or a conductive material touches (or comes close to) the touch sensor, the touch screen having the capacitive touch sensor senses a change in capacitance due to the input of the touch screen drive signal, that is, Thereby detecting the touch input.

The capacitive touch sensor may be implemented as a self capacitance sensor or a mutual capacitance sensor. Each of the electrodes of the capacitance sensor may be connected in a one-to-one relationship with sensor wirings formed along one direction. The mutual capacitance sensor may be formed at the intersection of the sensor wirings orthogonal to each other with the dielectric layer interposed therebetween.

In recent years, not only a finger but also a stylus pen have been widely used as a human interface device (HID) in smart phones and smart books. The stylus pen has the advantage of being able to input more finely than the finger.

There are passive and active stylus pens. In the passive type, it is difficult to detect the touch position because the capacitance change is very small at the contact point with the touch screen. The active type generates the pen driving signal by itself and outputs it to the proximity or contact point with the touch screen, so it is easier to detect the touch position than the passive type.

However, the conventional active stylus pen uses a pen driving signal having a frequency different from that of the touch screen driving signal in order to avoid interference with the touch screen driving signal, as disclosed in Korean Laid-Open Publication No. 10-2014-0043299. In this technique, a separate sensing circuit portion for receiving the pen drive signal is further required in the touch module, which increases the manufacturing cost.

In order to solve this problem, there is proposed a technique of generating a pen driving signal to be applied to the touch screen in synchronization with receiving the touch screen driving signal from the active stylus pen.

However, the size of the touch screen driving signal received by the stylus pen is affected by the air gap, and is reduced as the distance between the stylus pen and the touch screen is increased. That is, the magnitude of the first touch screen drive signal input to the stylus pen in the close state is smaller than the magnitude of the second touch screen drive signal input to the stylus pen in the contact state.

In order to obtain the desired touch sensing signal, the pen driving signal must be synchronized with the touch screen driving signal. However, depending on the proximity distance between the touch screen and the stylus pen, when the size of the touch screen driving signal received by the stylus pen is changed, the synchronization is lost. If the synchronization between the pen driving signal and the touch screen driving signal is disrupted, the touch sensing signal is reduced and the touch performance is degraded.

It is therefore an object of the present invention to provide a touch sensing system having a stylus pen for generating a pen drive signal based on a touch screen drive signal from a touch screen and then applying the same to a touch screen, The present invention provides a touch sensing system and a method of driving the touch sensing system, which can precisely synchronize a pen drive signal with a touch screen drive signal.

According to an aspect of the present invention, there is provided a touch sensing system including: a touch screen having a plurality of touch electrodes to which a touch screen driving signal is applied; and a pen driving signal generating unit for generating a pen driving signal based on the touch screen driving signal received from the touch screen. And a stylus pen for transmitting the generated data to the touch screen. The stylus pen includes: an amplifier for amplifying the touch screen driving signal to generate an amplified signal; a comparator for comparing the amplified signal with a reference voltage to generate a comparator output signal; And controls the reference voltage to be input to the comparator to be varied according to the measured value. The output timing of the pen driving signal is determined based on the adjustment comparator output signal according to the variation of the reference voltage, And a reference voltage varying unit for varying a reference voltage inputted to the comparator under the control of the signal processing unit.

The signal processing unit determines an output timing of the pen drive signal based on a rising edge or a falling edge of the adjustment comparator output signal.

Wherein the signal processing unit counts a high section of the comparator output signal using an internal counter and compares the count value with a default count value stored in an internal register, the count value corresponds to the measured value, The count value indicates the default pulse width for the comparator output signal.

Wherein the signal processing unit controls the reference voltage variable unit to raise the reference voltage to a value higher than the default reference voltage when the count value is larger than the default count value and to control the reference voltage variable unit when the count value is smaller than the default count value The reference voltage is lower than the default reference voltage, and when the count value is equal to the default count value, the reference voltage variable unit is controlled to maintain the reference voltage at the default reference voltage.

Wherein the stylus pen includes a conductive tip coupled to the touch screen to receive the touch screen driving signal from the touch screen and to transmit the pen driving signal to the touch screen when the stylus pen is in contact with or proximate to the touch screen, And a switching unit coupled to the conductive tip for transmitting the touch screen driving signal to the amplifier and transmitting the pen driving signal to the conductive tip.

Wherein at least one frame of signal switching section is provided between a reception section for receiving the touch screen driving signal and a transmission section for transmitting the pen driving signal and the signal processing section outputs the pen driving signal Determines the timing and generates the pen driving signal in accordance with the timing.

According to another aspect of the present invention, there is provided a method of driving a touch sensing system, including: a first step of contacting a stylus pen with or from a touch screen to receive a touch screen driving signal from the stylus pen; A third step of generating a comparator output signal by comparing the amplified signal with a reference voltage; a third step of measuring a pulse width of the comparator output signal and varying the reference voltage according to the measured value; A fourth step of synchronizing the pen drive signal with the touch screen drive signal by determining the output timing of the pen drive signal based on the adjustment comparator output signal according to the variation of the reference voltage, And a fifth step of transmitting the pen driving signal synchronized with the pen driving signal from the stylus pen to the touch screen The.

Since the comparator output signal is adjusted so that the pulse width is constant by varying the reference voltage input to the comparator and the pen driving signal is synchronized with the touch screen driving signal on the basis of the adjusting comparator output signal, By maintaining the synchronization between the touch screen driving signal and the pen driving signal regardless of whether the proximity distance between the screens is changed, the touch performance can be greatly improved by keeping the size of the touch sensing signal constant under the same conditions.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of a touch sensing system of the present invention.
2 is a view illustrating a display device to which a touch sensing system according to an embodiment of the present invention is applied.
3 is a view showing an example of a touch screen implemented by a mutual capacitance sensor.
4 is a view showing an example of a touch screen implemented with a magnetic capacity sensor.
5 is a view showing a detailed configuration of a touch IC;
Fig. 6 is a view showing that one frame is time-divided into a display driving period and a touch sensor driving period; Fig.
7 is a view showing the internal configuration of the stylus pen 200 according to the present invention.
8 is a view showing the operation procedure of the stylus pen 200 according to the present invention
Fig. 9 is a diagram showing that the touch screen driving signal and the pen driving signal are synchronized with each other within the touch sensor driving period T2. Fig.
10 shows waveforms of signals received and processed in the stylus pen of Fig. 7; Fig.
Fig. 11 is a view showing in detail the internal configuration of the stylus pen 200 shown in Fig. 7; Fig.
12 is a view showing that the sensitivity of the touch sensing signal is improved when the stylus pen is contacted as compared with the finger contact.
13 illustrates an example in which the synchronization between the touch screen driving signal and the pen driving signal is changed according to the proximity distance between the stylus pen and the touch screen.
14 is a diagram showing the magnitude of a touch sensing signal according to the degree of synchronization in a touch sensing system using a stylus pen.
FIGS. 15 through 18 illustrate a method of precisely synchronizing a pen drive signal to a touch screen drive signal regardless of the proximity distance between the stylus pen and the touch screen. FIG.
FIG. 19 illustrates that the magnitude of the touch sensing signal is kept constant regardless of the proximity distance when applying the synchronization scheme of FIGS. 15 to 18. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

[Touch Sensing  system]

1 schematically shows a touch sensing system of the present invention.

Referring to FIG. 1, the touch sensing system of the present invention includes a display device 100 and a stylus pen 200.

The display device 100 also has a display function and a touch detection function. The display device 100 is capable of performing touch detection by proximity or contact of a conductive object such as a finger or the stylus pen 200, and is provided with a capacitive touch screen as an integral unit. Here, the touch screen may be configured independently of the display panel for implementing the display, or may be embedded in the pixel array of the display panel. The configuration and operation of the display apparatus 100 will be described later with reference to Figs. 2 to 6. Fig.

The stylus pen 200 itself generates a pen drive signal and outputs it to the proximity or contact point with the touch screen to facilitate touch position detection on the touch screen. The stylus pen 200 receives a touch screen driving signal from a touch screen, generates a pen driving signal based on the received driving signal, and applies the pen driving signal to the touch screen. The configuration and operation of the stylus pen 200 will be described later with reference to Figs. 7 to 12. Fig.

In order to obtain a desired touch sensing signal, the pen driving signal must be precisely synchronized with the touch screen driving signal and then applied to the touch screen. 13 to 18 propose a configuration and a method for synchronizing a pen drive signal with a touch screen drive signal.

[Display device]

FIG. 2 shows a display device to which a touch sensing system according to an embodiment of the present invention is applied. FIG. 3 shows an example of a touch screen implemented as a mutual capacitance sensor. 4 shows an example of a touch screen implemented by a magnetic capacity sensor. 5 shows the detailed structure of the touch IC.

Referring to FIGS. 1 to 5, the touch sensing system of the present invention includes a display device 100 and a stylus pen 200.

The display device 100 may be a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting display , OLEDs, and electrophoresis (EPD) devices. In the following embodiments, the display device is implemented as a liquid crystal display device, but the display device of the present invention is not limited to the liquid crystal display device.

The display device 100 includes a display module and a touch module.

The touch module includes a touch screen (TSP) and a touch IC (20).

The touch screen (TSP) can be implemented in a capacitive manner that senses touch input through a plurality of capacitive sensors. The touch screen TSP includes a plurality of touch sensors having a capacitance. Capacitance can be divided into Self Capacitance and Mutual Capacitance. The electrostatic capacitance can be formed along a single-layer conductor wiring formed in one direction, and mutual capacitance can be formed between two orthogonal conductor wiring.

The touch screen TSP implemented by the mutual capacitive sensor Cm includes Tx electrode lines, Rx electrode lines intersecting the Tx electrode lines, and a plurality of Rx electrode lines at the intersections of the Tx electrode lines and the Rx electrode lines, And the touch sensors Cm formed thereon. The Tx electrode lines are driving signal lines for applying a touch screen driving signal to each of the touch sensors Cm to supply electric charges to the touch sensors. The Rx electrode lines are sensor wirings connected to the touch sensors Cm to supply the charges of the touch sensors to the touch IC 20. [ In the mutual capacitance sensing method, a driving signal is applied to a Tx electrode through a Tx electrode line to supply a charge to a touch sensor (Cm). When sensing a capacitance change through an Rx electrode and an Rx electrode line in synchronization with a touch screen driving signal, The input can be sensed.

The touch screen TSP implemented by the capacitance sensor Cs may be connected in a one-to-one relationship with the sensor wires 32 formed along one direction of the touch electrodes 31 as shown in FIG. The capacitance sensor Cs includes a capacitance formed in each of the electrodes 31. [ In the capacitance sensing method, when a drive signal is applied to the electrode 31 through the sensor wiring 32, the charge Q is accumulated in the touch sensor Cs. At this time, when a finger or a conductive object contacts the electrode 31, the parasitic capacitance Cf is further connected to the capacitance sensor Cs to change the capacitance value. Accordingly, the capacitance value between the finger-touched sensor and the non-touched sensor can be changed to determine whether the finger is touched or not.

The touch screen TSP may be bonded onto the upper polarizer plate of the display panel DIS or between the upper polarizer plate of the display panel DIS and the upper substrate. In addition, the touch sensors Cm or Cs of the touch screen TSP may be embedded in the pixel array of the display panel DIS.

The touch IC 20 senses the amount of change in charge of the touch sensor before and after touching to determine whether or not a conductive substance such as a finger (or a stylus pen) is touched and its position. The touch IC 20 includes a receiving system circuit group, a CPU 40, a control section 42, and a drive signal generating section 46.

The receiving circuit group is connected to the receiving channels of the touch screen (TSP) (Rx channels in Fig. 3, or S1 to Sm in Fig. 4). The receiving circuit group includes a receiving amplifier 30 for sensing touch (or proximity) input from receiving channels, an analog-to-digital converter (ADC) 30 for converting an analog sensing signal from the receiving amplifier 30 into a digital sensing signal, A detection unit 34 for removing a noise component from a digital sensing signal from the analog-to-digital conversion unit (ADC) 32; a storage unit 36 for storing a sensing signal input from the detection unit 34; And a position calculating unit 38 for comparing the sensing signal stored in the storage unit 36 with a predetermined threshold value and deriving a sensing signal having a larger value than the threshold value as a sensing signal at the touch input position.

The CPU 40 calculates the coordinate information TDATA (XY) of the touch (or proximity) input position by applying the sensing signal from the position calculating unit 38 to a preset coordinate extraction algorithm. Then, the calculated coordinate information (TDATA (XY)) is transmitted to the host system 18. The CPU 40 can receive the touch-driving synchronization signal SYNC from the host system 18 and transmit it to the control unit 42. [

The control unit 42 collectively controls the operation of the touch module based on the touch-driving synchronization signal SYNC.

The driving signal generating unit 46 is connected to the power supply unit 44 and receives driving power. The drive signal generator 46 generates a touch screen drive signal under the control of the controller 42 and generates a touch screen drive signal through the Tx channels of the touch screen TSP (Tx channels of FIG. 3 or S1 to Sm of FIG. 4) To the sensors. The touch screen driving signal may be generated in various forms such as a square wave type pulse, a sinusoidal wave, and a triangular wave, but it is preferably implemented as a square wave. The touch screen driving signal may be applied to each of the touch sensors N times so that the electric charges accumulated in the reception amplifier 30 may be accumulated N or more times (N is a natural number of 2 or more).

The display module may include a display panel (DIS), a display drive circuit (12, 14, 16), and a host system (18).

The display panel DIS includes a liquid crystal layer formed between two substrates. The pixel array of the display panel DIS includes pixels formed in the pixel region defined by the data lines (D1 to Dm, m is a positive integer) and the gate lines (G1 to Gn, n is a positive integer) . Each of the pixels is connected to TFTs (Thin Film Transistors) formed at intersections of the data lines D1 to Dm and the gate lines G1 to Gn, a pixel electrode for charging a data voltage, A storage capacitor (Cst) for maintaining a voltage, and the like.

A black matrix, a color filter, and the like may be formed on the upper substrate of the display panel DIS. The lower substrate of the display panel DIS may be implemented with a COT (Color Filter On TFT) structure. In this case, the black matrix and the color filter can be formed on the lower substrate of the display panel DIS. The common electrode to which the common voltage is supplied may be formed on the upper substrate or the lower substrate of the display panel DIS. On the upper substrate and the lower substrate of the display panel DIS, a polarizing plate is attached, and an alignment film for forming a pre-tilt angle of the liquid crystal on the inner surface in contact with the liquid crystal is formed. A column spacer for maintaining a cell gap of the liquid crystal cell is formed between the upper substrate and the lower substrate of the display panel DIS.

A backlight unit may be disposed below the rear surface of the display panel DIS. The backlight unit is implemented as an edge type or direct type backlight unit, and irradiates the display panel (DIS) with light. The display panel DIS may be implemented in any known liquid crystal mode such as TN (Twisted Nematic) mode, VA (Vertical Alignment) mode, IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode.

The display driving circuit includes a data driving circuit 12, a scan driving circuit 14, and a timing controller 16, and writes video data of the input image to pixels of the display panel DIS. The data driving circuit 12 converts the digital video data RGB input from the timing controller 16 into an analog positive / negative gamma compensation voltage to output a data voltage. The data voltage output from the data driving circuit 12 is supplied to the data lines D1 to Dm. The scan driving circuit 14 sequentially supplies a gate pulse (or a scan pulse) synchronized with the data voltage to the gate lines G1 to Gn to select a pixel line of the display panel DIS to which the data voltage is written.

The timing controller 16 inputs timing signals such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE and a main clock MCLK input from the host system 18 And synchronizes the operation timings of the data driving circuit 12 and the scan driving circuit 14 with each other. The scan timing control signal includes a gate start pulse (GSP), a gate shift clock, a gate output enable signal (GOE), and the like. The data timing control signal includes a source sampling clock (SSC), a polarity control signal (Polarity), a source output enable signal (SOE), and the like.

The host system 18 may be implemented in any one of a television system, a set-top box, a navigation system, a DVD player, a Blu-ray player, a personal computer (PC), a home theater system, and a phone system. The host system 18 includes a system on chip (SoC) with a built-in scaler to convert the digital video data RGB of the input image into a format suitable for display on the display panel DIS. The host system 18 transmits timing signals (Vsync, Hsync, DE, MCLK) to the timing controller 16 together with the digital video data. The host system 18 also transmits the touch-driving synchronization signal SYNC to the touch IC 20 and executes an application program associated with the touch coordinate information XY input from the touch IC 20. [

The host system 18 divides one frame period into a display driving period T1 and a touch sensor driving period T2 by referring to the vertical synchronization signal Vsync and the touch driving synchronization signal SYNC as shown in FIG. . Display noise may be mixed into the touch sensing signal. Especially, when the touch sensors of the touch screen TSP are embedded in the pixel array of the display panel DIS, the amount of the mixing is increased. The time division driving is useful for reducing the influence of noise and improving the accuracy of touch sensing.

The host system 18 generates the touch-driving synchronization signal SYNC based on the vertical synchronization signal Vsync and then transmits it to the timing controller 16 and the touch IC 20. On the other hand, the touch-driving synchronization signal SYNC may be generated in the timing controller 16.

During the display driving period T1, the data driving circuit 12 supplies the data voltages to the data lines D1 to Dm under the control of the timing controller 16, and the scan driving circuit 14 supplies the data voltages to the timing controller 16. [ A gate pulse synchronized with the data voltage is sequentially supplied to the gate lines G1 to Gn under the control of the control circuit. On the other hand, during the display driving period T1, the touch IC 20 stops operating.

During the touch sensor driving period T2, the touch IC 20 senses a touch (or proximity) input position by applying a touch screen driving signal to the touch sensors of the touch screen TSP. Meanwhile, during the touch sensor driving period T2, the display driving circuits 12, 14, and 16 are turned on in order to minimize the parasitic capacitance between the signal lines D1 to Dm, G1 to Gn connected to the pixels and the touch sensors It is possible to supply an AC signal having the same amplitude and the same phase as the touch screen driving signal to the signal lines D1 to Dm and G1 to Gn. In this case, the display noise mixed into the touch sensing signal is drastically reduced, which greatly increases the accuracy of the touch sensing.

[ Stylus  pen]

7 shows the internal structure of the stylus pen 200 according to the present invention.

7, the stylus pen 200 includes a housing 280, a conductive tip 210 protruding outward from one side of the housing 280, and a switch 210 connected to the conductive tip 210 in the housing 280. [ A touch sensing unit 230 for sensing a touch screen driving signal input from the conductive tip 210 through the switching unit 220 and a controller 230 for controlling the touch screen driving signal based on a touch screen driving signal from the receiving unit 230, A driving unit 240 for level-shifting the pen driving signal generated by the signal processing unit 250 and then supplying the pen driving signal to the conductive tip 210 through the switching unit 220; A power supply unit 260 for generating driving power required for the operation, and an input / output interface 270.

The conductive tip 210 is made of a conductive material such as metal and serves as a receiving electrode and a transmitting electrode. When the conductive tip 210 is contacted or hovered on the touch screen TSP of the display device 200, the conductive tip 210 at the contact (or proximity) Lt; / RTI > The conductive tip 210 receives the touch screen drive signal from the touch screen TSP at a point of contact (or proximity), and then transmits the pen drive signal generated inside the stylus pen 200 to the touch screen (TSP) To the point of contact (or proximity).

The switching unit 220 may switch the conductive tip 210 and the receiving unit 230 for one hour when the conductive tip 210 is contacted or hovered on the touch screen TSP of the display device 200. [ And electrically connects the conductive tip 210 and the driving unit 240 for another period of time to temporally separate the timing of receiving the touch screen driving signal and the timing of transmitting the pen driving signal. The structure of the stylus pen 200 is simplified because the conductive tip 210 also functions as a receiving electrode and a transmitting electrode.

The receiving unit 230 may include at least one amplifier to amplify a touch screen driving signal input from the conductive tip 210 through the switching unit 220. The receiving unit 230 includes a comparator, compares the amplified signal with a preset reference voltage, and outputs the result to the signal processing unit 250.

The signal processing unit 250 analyzes the output signal of the comparator input from the receiving unit 230 in one frame or more and generates a pen driving signal synchronized with the touch screen driving signal and outputs the pen driving signal to the driving unit 240.

The driving unit 240 includes a level shifter to adjust the voltage level of the pen driving signal according to the touch screen driving signal. The driving unit 240 outputs the level-shifted pen driving signal to the conductive tip 210 through the switching unit 220.

The input / output interface 270 is connected to the power supply unit 260 according to a user pressing operation from the outside, and supplies necessary power to the receiving unit 230, the driving unit 240, and the signal processing unit 250.

8 shows the operation procedure of the stylus pen 200 according to the present invention.

8, the conductive tip 210 is brought into contact with (or brought into proximity to) a predetermined point of the touch screen TSP in a state in which the power is applied through the input / output interface 270 and the power supply unit 260 (S1, S2).

During the driving of the touch sensor, a touch screen driving signal is supplied to each touch sensor of the touch screen (TSP). During the touch sensor driving period, the conductive tip 210 is directly coupled to the touch screen TSP at the contact time to sense the touch screen driving signal received from the touch electrode of the touch screen TSP, (220). The receiving unit 220 amplifies the touch screen driving signal through an internal amplifier, compares the amplified signal with a reference voltage in an internal comparator, and outputs the comparison result to the signal processing unit 250 (S3).

The signal processing unit 250 analyzes a comparator output signal input from the receiving unit 230 and determines a timing to be synchronized with the touch screen driving signal. The signal processing unit 250 generates a pen driving signal according to the synchronization timing, and outputs the pen driving signal to the driving unit 240. In particular, the signal processor 250 measures the pulse width of the comparator output signal, controls the reference voltage input to the comparator to vary according to the measured value, Determines the output timing of the driving signal, and synchronizes the pen driving signal with the touch screen driving signal. At this time, the signal processing unit 250 is based on a rising edge or a falling edge of a comparator output signal or a high-range center value of a comparator output signal in determining synchronization timing. If the pulse width of the comparator output signal is adjusted to be constant by varying the reference voltage input to the comparator, even if the magnitude of the comparator input signal (amplified by the amplifier) changes according to the external noise or hovering degree, There is an advantage that the synchronization timing can be kept constant (S4, S5). This will be described in detail later with reference to FIG. 15 to FIG. On the other hand, the process of determining the synchronization timing may be performed through an accumulation value of one frame or more with respect to the output signal of the comparator. The reason for this is to precisely synchronize the touch screen drive signal and the pen drive signal.

The driving unit 240 includes a level shifter for level shifting the voltage level of the pen driving signal according to the touch screen driving signal and then outputs the level shifted pen driving signal to the conductive tip 210 through the switching unit 220 . The conductive tip 210 applies a pen drive signal to the touch (or proximity) point of the touch screen (S6).

9 shows that the touch screen driving signal and the pen driving signal are synchronized with each other within the touch sensor driving period T2. 10 shows a waveform of a signal received and processed in the stylus pen of FIG. 7;

9 and 10, following the ON operation of the first stylus pen 200, after the contact of the stylus pen 200 with the touch screen TSP, the receiving period Ra of the touch screen driving signal Ts, A signal switching period of at least one frame is provided between the transmission period Ta of the driving signal Ps and the stability of the operation is ensured. The signal processing unit 250 determines the synchronization timing using the signal switching period and generates the pen driving signal Ps accordingly.

A process (Ta) of transmitting a pen driving signal (Ps) synchronized with the touch screen driving signal (Ts) to the touch screen (TSP) through the conductive tip (210) The process (Ra) of receiving the touch screen driving signal (Ts) is repeatedly and alternately performed. After the first pen drive signal Ps is synchronized with the touch screen drive signal Ts, the signal changeover interval in the following frames may be omitted.

10, the reception interval Ra of the touch screen drive signal Ts and the transmission interval Ta of the pen drive signal Ps are shown as equally, but the time width of the reception interval Ra is substantially The smaller the time required for the touch response, the larger the time width of the transmission period Ta is.

11 shows the internal structure of the stylus pen 200 shown in FIG. 7 in more detail.

11, the input / output stage 205 of the stylus pen 200 may further include a conductive tip 210 and a pressure sensor 215 in addition to the switching unit 220. The pressure sensor 215 senses the pressure at which the stylus pen 200 is pressed on the touch screen TSP and transmits the sensed pressure to the signal processing unit 250. The signal processing unit 250 can change the pen driving signal Ps according to the sensed pressure level, thereby improving the sensitivity of the stylus pen 200 when a touch event occurs.

The receiving section 230 of the stylus pen 200 includes a receiving buffer 231, an amplifier 233, and a comparator 235. The reception buffer 231 receives the touch screen driving signal Ts transmitted through the switching unit 220 and applies the received touch screen driving signal Ts to the amplifier 233. The amplifier 233 includes at least two stages to amplify the touch screen driving signal Ts at the analog level to increase the sensitivity of the received signal. The comparator 235 compares the amplified signal from the amplifier 233 with an internal reference voltage to generate a comparator output signal COM at a digital level above the reference voltage or below the reference voltage. Here, when the amplifier 233 is implemented as an inverting amplifier, the comparator 235 uses a signal equal to or higher than the reference voltage as the comparator output signal COM. When the amplifier 233 is implemented as a non-inverting amplifier, Can be used as the comparator output signal COM.

The signal processing unit 250 of the stylus pen 200 determines the timing of synchronizing with the touch screen driving signal Ts based on the comparator output signal COM as described above and then, And generates a signal Ps.

In the driving unit 240 of the stylus pen 200, the voltage level of the pen driving signal Ps is level-shifted by the level shifter 243 in accordance with the touch screen driving signal Ts , And outputs the level shifted pen driving signal Ps to the switching unit 220 through the transmission buffer 241. [ Then, the switching unit 220 transfers the pen driving signal Ps to the conductive tip 210.

FIG. 12 is a simulation result showing that the sensitivity of the touch sensing signal is improved when the stylus pen is contacted as compared with the finger contact.

Referring to FIG. 12, the applicant of the present invention has experimentally measured the intensity of each touch sensing signal when touching the touch screen with the stylus pen and when touching the touch screen with the finger. Experimental results show that the intensity of the sensing signal when touching the stylus pen against the touch screen is high and the intensity of the sensing signal is greater when the coupled capacitance between the touch screen and the conductive tip is larger.

The touch sensing system of the present invention has an effect of increasing the size of a touch sensing signal by including an active stylus pen that generates a pen driving signal synchronized with a touch screen driving signal and applies the pen driving signal to the touch screen.

[Synchronization plan]

13 shows an example in which the synchronization between the touch screen driving signal and the pen driving signal is changed according to the proximity distance between the stylus pen and the touch screen. 14 shows the magnitude of the touch sensing signal according to the degree of synchronization in the touch sensing system using the stylus pen.

The signal processing unit 250 of the stylus pen 200 determines the timing of synchronizing with the touch screen driving signal Ts based on the comparator output signal COM as described above and then, And generates a signal Ps.

However, the size of the touch screen driving signal received by the stylus pen varies depending on the proximity distance between the touch screen and the stylus pen, as shown in FIG. The size of the touch screen driving signal becomes smaller when the proximity distance is shorter (dotted line waveform) than when the proximity distance is shorter (solid line waveform). When generating a comparator output signal based on the same reference voltage at the comparator 235 of the stylus pen 200, the second comparator 233 when the proximity distance is close to the first comparator output signal (dotted line waveform) The output signal (solid line waveform) has different pulse widths.

In this case, when the signal processing unit 250 determines the synchronization timing based on the specific time point of the comparator output signal, the synchronization timing necessarily depends on the proximity distance between the touch screen and the stylus pen. For example, when the rising edge of the comparator output signal is determined as the synchronous timing and the pen driving signal is generated after a certain time (?) Delay from the rising edge as shown in FIG. 13, the first comparator output signal (dotted line waveform) A phase difference is generated between the first pen drive signal Ps # 1 and the second pen drive signal Ps # 2 by the phase difference ta-tb of the second comparator output signal (solid line waveform). If the first pen drive signal Ps # 1 is synchronized with the touch screen drive signal Ts, the second pen drive signal Ps # 2 is synchronized with the touch screen drive signal Ts by the phase difference, Is in a distorted state.

In this way, when the comparator output signal is generated in accordance with a constant reference voltage and the synchronization timing is determined based on the rising edge or the falling edge of the comparator output signal, the proximity distance between the touch screen and the stylus pen, The synchronization timing is changed every time the magnitude of the touch screen driving signal received by the pen is changed. When the synchronization timing is changed, a synchronization error occurs between the touch screen driving signal Ts and the pen driving signal Ps, and accordingly, the size of the touch sensing signal is kept constant under the same condition (touch or fine touch) There is a problem that it can not be reduced. If the size of the touch sensing signal can not be kept constant under the same condition (touch or fine touch), a non-touch point may be erroneously recognized as a touch point and conversely, a touch point may be erroneously recognized as a non-touch point have.

FIGS. 15 to 18 show a method of precisely synchronizing the pen drive signal with the touch screen drive signal regardless of the proximity distance between the stylus pen and the touch screen. FIG. 19 shows the magnitude of the touch sensing signal according to the proximity distance when the synchronization scheme of FIGS. 15 to 18 is applied.

Referring to FIG. 15, the stylus pen 200 of the present invention is characterized in that a reference voltage inputted to the comparator is varied so that the pulse width of the comparator output signal satisfies a predetermined default value before determining the synchronous timing. To this end, the stylus pen 200 of the present invention further includes a reference voltage varying unit 260 for varying a reference voltage input to the comparator 235 under the control of the signal processing unit 250.

The signal processing unit 250 controls the operation of the reference voltage varying unit 260 to vary the reference voltage AVref input to the comparator 235 according to the pulse width of the comparator output signal COM. The signal processing unit 250 measures the pulse width of the comparator output signal COM to obtain a measured value, generates an adjustment control signal CV according to the measured value, and supplies the adjusted control signal CV to the reference voltage varying unit 260. The reference voltage varying unit 260 varies the reference voltage AVref according to the adjustment control signal CV. Specifically, if the measured value is greater than the default pulse width, the signal processing unit 250 controls the reference voltage varying unit 260 to raise the reference voltage AVref to a value higher than the default reference voltage. On the contrary, if the measured value is smaller than the default pulse width , The reference voltage changing unit 260 is controlled so that the reference voltage AVref is lower than the default reference voltage to maintain the pulse width of the comparator output signal COM constant.

After the pulse width of the comparator output signal COM is adjusted to be equal to the default value, the signal processing unit 250 outputs the timing of the output of the pen driving signal COM based on the rising edge or the falling edge of the adjusted comparator output signal COM .

According to the present invention, even if the magnitude of the touch screen driving signal received by the stylus pen changes according to the proximity distance between the touch screen and the stylus pen, the first amplifier output signal (solid line waveform) (Dashed line waveform) when the proximity distance is close to the relatively high second reference voltage Vref2 by comparing the first reference voltage Vref1 with the relatively low first reference voltage Vref1 and by comparing the second amplifier output signal And a comparator output signal COM having an amplitude can be obtained. A pen drive signal Ps synchronized with the touch screen drive signal Ts is generated after a certain time delay from the rising edge RE of the comparator output signal COM or the falling edge FE of the comparator output signal COM. That is, even if the proximity distance between the touch screen and the stylus pen changes, the synchronization between the pen drive signal Ps and the touch screen drive signal Ts based on the first amplifier output signal (solid line waveform) and the second amplifier output signal , The synchronization between the pen drive signal Ps and the touch screen drive signal Ts is not interrupted.

The process of performing the synchronization process according to the present invention through the amplifier 233, the comparator 235, the signal processing unit 250, and the reference voltage varying unit 260 with reference to FIG. 17 and FIG. ) Will be described in detail as follows.

The synchronization scheme according to the present invention amplifies the touch screen driving signal inputted from the touch screen through the amplifier 233 and compares the signal amplified by the amplifier 233 with the default reference voltage through the comparator 235, And outputs the signal to the signal processing unit 250 (S41, S42).

The signal processing unit 250 controls the operation of the reference voltage varying unit 260 to adjust the reference voltage applied to the comparator 235 so that the pulse width of the comparator output signal inputted from the comparator 235 satisfies a predetermined value . The signal processing unit 250 counts the pulse width (high section Th from the rising edge to the falling edge) of the comparator output signal using an internal counter, and compares the count value with the default count value stored in the internal register . If the count value is larger than the default count value, the signal processing unit 250 increases the reference voltage applied to the comparator 235 to be higher than the default reference voltage. On the other hand, if the count value is smaller than the default count value, the signal processing unit 250 lowers the reference voltage applied to the comparator 235 to be lower than the default reference voltage. Meanwhile, if the count value is equal to the default count value, the signal processing unit 250 maintains the reference voltage applied to the comparator 235 as the default reference voltage (S43).

The signal processing unit 250 determines the output timing of the pen driving signal Ps synchronized with the touch screen driving signal Ts based on the adjusting comparator output signal whose pulse width is set to a predetermined value through the reference voltage adjusting process. That is, the signal processing unit 250 outputs a timing at which the rising edge (RE) or the falling edge (FE) of the output signal of the adjustment comparator, or the delayed value of the high-range center value of the adjustment comparator output signal by the predetermined value (Td) As the output timing of the pen drive signal Ps synchronized with the signal Ts (S44, S45). Here, when determining the output timing of the pen drive signal Ps, the reason for delaying the rising edge (or the falling edge) or the high-section center value by a predetermined value Td is to secure the stability of the operation.

When the output timing of the pen drive signal Ps is determined based on the adjustment comparator output signal after the reference voltage input to the comparator is varied to make the pulse width of the comparator output signal constant, The synchronization between the touch screen driving signal Ts and the pen driving signal Ps is not changed even when the size of the touch screen driving signal is changed due to external noise. Accordingly, as shown in FIG. 18, the size of the touch sensing signal is kept constant regardless of the proximity distance in the state where the touch is performed, and the touch performance is greatly improved.

As described above, according to the present invention, even if a separate additional circuit (or additional electrode) for driving the stylus pen is not provided to the display device, the conductive tip of the stylus pen is used as a medium for transmitting and receiving the touch screen driving signal and the pen driving signal The structure of the system can be simplified even in a state in which high sensitivity of the touch sensing is maintained. According to the present invention, there is no need to form an electromagnetic sensor on a display device for driving a stylus pen, and thus a touch screen having a simplified structure can be realized. Especially, when a touch sensor is applied to an in- The effect is great.

The stylus pen generates a pen driving signal based on a touch screen driving signal inputted from a touch screen, so that it is possible to detect whether or not the pen contact (or proximity) is exactly in the touch interval period, and the accuracy of touch detection can be achieved. Therefore, it is possible to realize a highly sensitive stylus pen, maintain the linearity of touch detection, and improve the touch performance. Further, by using such a stylus pen, it is possible to realize better touch sensitivity compared to a finger touch.

Particularly, the present invention adjusts the output signal of the comparator so as to vary the reference voltage inputted to the comparator so that the pulse width is constant, and then synchronizes the pen driving signal with the touch screen driving signal on the basis of the adjusting comparator output signal, The synchronization between the touch screen driving signal and the pen driving signal is maintained regardless of whether the proximity distance between the touch screen and the touch screen is changed, thereby making it possible to improve the touch performance by making the size of the touch sensing signal constant under the same conditions.

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. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

100: display device 200: stylus pen
210: Conductive tip 220:
230: Receiving unit 231: Receiving buffer
233: Amplifier 235: Comparator
240: driving unit 241: transmission buffer
243: level shifter 250: signal processor
260: Reference voltage variable section

Claims (17)

A touch screen having a stylus pen for generating a pen driving signal based on the touch screen driving signal received from the touch screen and transmitting the pen driving signal to the touch screen, In a sensing system,
The stylus pen,
An amplifier for amplifying the touch screen driving signal to generate an amplified signal;
A comparator for comparing the amplified signal with a reference voltage to generate a comparator output signal;
And a controller for controlling the reference voltage to be input to the comparator according to the measured value and controlling the output timing of the pen drive signal based on the adjustment comparator output signal according to the variation of the reference voltage And synchronizing the pen drive signal with the touch screen drive signal; And
And a reference voltage varying unit for varying a reference voltage inputted to the comparator under the control of the signal processing unit. The method according to claim 1,
The signal processing unit,
Wherein the output timing of the pen drive signal is determined based on a rising edge or a falling edge of the adjustment comparator output signal. 3. The method of claim 2,
The signal processing unit,
Counts a high section of the comparator output signal using an internal counter, compares the count value with a default count value stored in an internal register,
Wherein the count value corresponds to the measurement value and the default count value indicates a default pulse width for the comparator output signal. The method of claim 3,
The signal processing unit,
When the count value is greater than the default count value, the reference voltage variable unit is controlled to raise the reference voltage to be higher than a default reference voltage,
When the count value is smaller than the default count value, the reference voltage variable unit is controlled to lower the reference voltage to less than the default reference voltage,
And controls the reference voltage varying unit to maintain the reference voltage at the default reference voltage when the count value is equal to the default count value. The method according to claim 1,
The stylus pen,
A conductive tip coupled to the touch screen to receive the touch screen driving signal from the touch screen and to transmit the pen driving signal to the touch screen when the touch screen is in contact with or proximate to the touch screen,
And a switching unit coupled to the conductive tip for delivering the touch screen drive signal to the amplifier and delivering the pen drive signal to the conductive tip. The method according to claim 1,
A signal switching section of at least one frame is provided between a reception section for receiving the touch screen driving signal and a transmission section for transmitting the pen driving signal,
Wherein the signal processing unit determines the output timing of the pen driving signal using the signal switching period and generates the pen driving signal accordingly. A first step of receiving a touch screen driving signal from the stylus pen by bringing the stylus pen into contact with or proximity to the touch screen;
A second step of amplifying the touch screen driving signal to generate an amplified signal;
A third step of comparing the amplified signal with a reference voltage to generate a comparator output signal;
And a controller for controlling the reference voltage to be varied according to the measured value and determining an output timing of the pen driving signal based on an adjustment comparator output signal according to the variation of the reference voltage, A fourth step of synchronizing a driving signal with the touch screen driving signal; And
And a fifth step of transmitting the pen driving signal synchronized with the touch screen driving signal from the stylus pen to the touch screen. 8. The method of claim 7,
In the fourth step,
Wherein the output timing of the pen drive signal is determined based on a rising edge or a falling edge of the adjustment comparator output signal. 9. The method of claim 8,
In the fourth step,
Counts a high section of the comparator output signal using an internal counter and compares the count value with a default count value stored in an internal register, the count value corresponds to the measured value, Wherein a default pulse width for an output signal is indicated. 10. The method of claim 9,
In the fourth step,
If the count value is greater than the default count value, increasing the reference voltage to a value higher than a default reference voltage,
If the count value is less than the default count value, lowering the reference voltage to less than the default reference voltage
And maintaining the reference voltage at the default reference voltage when the count value is equal to the default count value. 8. The method of claim 7,
A signal switching section of at least one frame is provided between a reception section for receiving the touch screen driving signal and a transmission section for transmitting the pen driving signal,
Wherein the fourth step determines the output timing of the pen driving signal using the signal switching period and generates the pen driving signal accordingly. A stylus pen for generating a pen driving signal based on a touch screen driving signal received from a touch screen and transmitting the pen driving signal to the touch screen,
An amplifier for amplifying the touch screen driving signal to generate an amplified signal;
A comparator for comparing the amplified signal with a reference voltage to generate a comparator output signal;
And a controller for controlling the reference voltage to be input to the comparator according to the measured value and controlling the output timing of the pen drive signal based on the adjustment comparator output signal according to the variation of the reference voltage And synchronizing the pen drive signal with the touch screen drive signal; And
And a reference voltage varying section for varying a reference voltage inputted to the comparator under the control of the signal processing section. 13. The method of claim 12,
The signal processing unit,
Wherein the output timing of the pen drive signal is determined based on a rising edge or a falling edge of the adjustment comparator output signal. 14. The method of claim 13,
The signal processing unit,
Counts a high section of the comparator output signal using an internal counter, compares the count value with a default count value stored in an internal register,
Wherein the count value corresponds to the measurement value and the default count value indicates a default pulse width for the comparator output signal. 15. The method of claim 14,
The signal processing unit,
When the count value is greater than the default count value, the reference voltage variable unit is controlled to raise the reference voltage to be higher than a default reference voltage,
When the count value is smaller than the default count value, the reference voltage variable unit is controlled to lower the reference voltage to less than the default reference voltage,
And controls the reference voltage varying unit to maintain the reference voltage at the default reference voltage when the count value is equal to the default count value. 13. The method of claim 12,
A conductive tip coupled to the touch screen to receive the touch screen driving signal from the touch screen and to transmit the pen driving signal to the touch screen when the touch screen is in contact with or proximate to the touch screen,
Further comprising a switching unit coupled to the conductive tip for delivering the touch screen drive signal to the amplifier and delivering the pen drive signal to the conductive tip. 13. The method of claim 12,
A signal switching section of at least one frame is provided between a reception section for receiving the touch screen driving signal and a transmission section for transmitting the pen driving signal,
Wherein the signal processing unit determines the output timing of the pen driving signal using the signal switching period and generates the pen driving signal accordingly.

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