Touch sensing system and display device including the same

The present application claims the priority benefit of Korean Patent Application No. 10-2016-0184249 filed in Republic of Korea on Dec. 30, 2016, which is hereby incorporated by reference in its entirety for all purposes as if fully set forth herein.

The present disclosure relates to a touch sensing system and a display device including the same.

Facing information society, display field of displaying electric information signals has been rapidly advanced, and accordingly, various flat display devices have been developed and used. As flat display devices, a liquid crystal display device (LCD), a plasma display panel device (PDP), an organic light emitting diode (OLED) display device and the like are used.

A touch panel as a user input device is applied to a display device and senses a user's touch.

Recently, to realize an UI (user interface)/UX (user experience), the related art touch sensing system capable of a user touch position and a user recognition as well is provided. This system employs an IR (infrared ray) type touch panel to detect of a user touch position, and a mutual capacitive type touch panel for a user recognition (or user ID).

The IR type touch panel senses an infrared ray from an IR generator and detects a user touch position.

The mutual capacitive type touch panel has a driving electrode and a sensing electrode which are formed entirely over the panel and form a single capacitor, and this capacitor is connected to a resistor and an inductor, which are located outside the panel, to form a RLC band cut filter. At a user touch, an impedance of the RLC filter is measured to recognize a user.

Since the related art touch sensing system requires both of the IR type touch panel and the mutual capacitive type touch panel, a thickness and a cost of the system increase, and a thickness and a cost of a display device using the system increase.

Further, the related art touch sensing system uses the RLC band cut filter for a user recognition. However, the RLC band cut filter has a narrow gain range (or dynamic range) for an impedance measurement due to its characteristics, and a touch detection capability is degraded.

Accordingly, the present disclosure is directed to a touch sensing system and a display device including the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

An advantage of the present disclosure is to provide a touch sensing system and a display device including the same that can reduce a thickness and a cost of a touch sensing system achieving a user touch position detection and a user recognition, and improve a detection capability of a user recognition.

Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the disclosure. These and other advantages of the disclosure will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the present disclosure, as embodied and broadly described herein, a touch sensing system includes: a touch screen that includes a plurality of first driving electrodes, a plurality of second driving electrodes, and a plurality of sensing electrodes; a first driving circuit that outputs a first driving signal of a pulse waveform to a respective first driving electrode of the plurality of first driving electrodes in a first sensing period; a second driving circuit that outputs a second driving signal of a frequency sweep waveform to a respective second driving electrode of the plurality of second driving electrodes in a second sensing period; a first detection circuit that detects a first sensing signal sensed by at least one of the sensing electrodes in the first sensing period; a second detection circuit that detects a second sensing signal sensed by at least one of the sensing electrodes in the second sensing period; and an inductor that is connected between the sensing electrodes and the second detection circuit in the second sensing period.

In another aspect, a touch sensing system includes: a touch screen that includes a plurality of driving electrodes, and a plurality of sensing electrodes; a driving circuit that outputs a first driving signal of a pulse waveform to a first driving electrode of the plurality of driving electrodes in a first sensing period, and outputs a second driving signal of a frequency sweep waveform to the first driving electrode in a second sensing period; a first detection circuit that detects a first sensing signal sensed by at least one of the sensing electrodes in the first sensing period; a second detection circuit that detects a second sensing signal sensed by at least one of the sensing electrodes in the second sensing period; and an inductor that is connected between the sensing electrodes and the second detection circuit in the second sensing period.

In another aspect, a display device includes: a display panel; a touch screen that corresponds to a display region of the display panel, and includes a plurality of first driving electrodes, a plurality of second driving electrodes, and a plurality of sensing electrodes; a first driving circuit that outputs a first driving signal of a pulse waveform to a respective first driving electrode of the plurality of first driving electrodes in a first sensing period; a second driving circuit that outputs a second driving signal of a frequency sweep waveform to a respective second driving electrode of the plurality of second driving electrodes in a second sensing period; a first detection circuit that detects a first sensing signal sensed by at least one of the sensing electrodes in the first sensing period; a second detection circuit that detects a second sensing signal sensed by at least one of the sensing electrodes in the second sensing period; and an inductor that is connected between the sensing electrodes and the second detection circuit in the second sensing period.

In another aspect, a display device includes: a display panel; a touch screen that corresponds to a display region of the display panel, and includes a plurality of driving electrodes, and a plurality of sensing electrodes; a driving circuit that outputs a first driving signal of a pulse waveform to a first driving electrode of the plurality of driving electrodes in a first sensing period, and outputs a second driving signal of a frequency sweep waveform to the first driving electrode in a second sensing period; a first detection circuit that detects a first sensing signal sensed by at least one of the sensing electrodes in the first sensing period; a second detection circuit that detects a second sensing signal sensed by at least one of the sensing electrodes in the second sensing period; and an inductor that is connected between the sensing electrodes and the second detection circuit in the second sensing period.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed.

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the principles of the disclosure. In the drawings:

FIG. 1 is a plan view illustrating a touch sensing system according to a first embodiment of the present disclosure;

FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1 ;

FIG. 3 is a circuit diagram illustrating an RCL series circuit produced in the touch sensing system according to the first embodiment of the present disclosure;

FIG. 4 is a timing chart of driving signals and a sensing signal of the touch sensing system according to the first embodiment of the present disclosure;

FIG. 5 is a cross-sectional view illustrating an example of a display device including a display panel and a touch panel according to the first embodiment of the present disclosure;

FIG. 6 is a timing chart of first and second driving signals and a sensing signal in an example that a first driving electrode and a sensing electrode of a touch screen is formed in a display panel according to the first embodiment of the present disclosure;

FIG. 7 is a view illustrating a user recognition by an impedance measurement according to the first embodiment of the present disclosure;

FIG. 8 is a plan view illustrating a touch sensing system according to a second embodiment of the present disclosure;

FIG. 9 is a cross-sectional view taken along a line IX-IX of FIG. 8 . FIG. 9 shows an example that a touch screen is formed as a touch panel;

FIG. 10 is a circuit diagram illustrating an CRCL series circuit produced in the touch sensing system according to the second embodiment of the present disclosure;

FIG. 11 is a timing chart of driving signals and a sensing signal of the touch sensing system according to the second embodiment of the present disclosure;

FIG. 12 is a cross-sectional view illustrating an example of a display device including a display panel and a touch panel according to the second embodiment of the present disclosure; and

FIG. 13 is a timing chart of first and second driving signals and a sensing signal in an example that a driving electrode and a sensing electrode of a touch screen is formed in a display panel according to the second embodiment of the present disclosure.

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The same reference numbers may be used throughout the drawings to refer to the same or like parts.

[First Embodiment]

FIG. 1 is a plan view illustrating a touch sensing system according to a first embodiment of the present disclosure, and FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1 . FIG. 2 shows an example that a touch screen is formed as a touch panel.

Referring to FIG. 1 , the touch sensing system 100 of this embodiment is a touch sensing system that is applied to a display device and performs a user touch position detection and a user recognition. The touch sensing system 100 includes a touch screen 110 in which driving electrodes DE 1 and DE 2 and sensing electrodes SE to sense a user touch are located, and a driving circuit to operate the electrodes DE 1 , DE 2 and SE of the touch screen 110 . The driving circuit includes a first driving circuit 120 , a second driving circuit 130 , and a read-out circuit 140 .

The touch screen 110 is arranged to correspond to a display region of a display panel of a display device and senses a user touch on a display surface of the display panel. The touch screen 110 may be manufactured separately from the display panel and be attached to the display panel.

Referring to FIGS. 1 and 2 , the touch screen 110 includes a plurality of first driving electrodes DE 1 extending, parallel with each other, along a first direction (e.g., a horizontal direction or a X direction), and a plurality of sensing electrodes SE extending, parallel with each other, along a second direction (e.g., a vertical direction or a Y direction) crossing the first direction. The touch screen 110 further includes a plurality of second driving electrodes DE 2 extending, parallel with each other, along a second direction and overlapping the plurality of sensing electrodes SE. Alternatively, the second driving electrodes DE 2 may be configured to extend along the first direction while overlapping the sensing electrodes SE.

In this embodiment, an example, as shown in FIG. 2 , that the first driving electrode DE 1 and the sensing electrode SE are formed on a substrate 111 , a dielectric layer 112 made of an insulating material is formed entirely on the substrate 111 having the first driving electrode DE 1 and the sensing electrode SE, and the second electrode DE 2 is formed on the dielectric layer 112 is illustrated. A protection layer 113 may be formed on the second driving electrode DE 2 . In this case, the first driving electrode DE 1 and the sensing electrode SE are formed at the same layer, and one of them, for example, the sensing electrode SE on each horizontal line may have a connection structure along its extended direction using bridge patterns that each connect neighboring parts of the sensing electrode SE.

A configuration other than the above configuration may be employed. For example, the first driving electrode DE 1 and the sensing electrode SE may be located at different layers with a dielectric layer therebetween. For other example, at least one of the first driving electrode DE 1 and the sensing electrode SE may be located below the substrate 111 .

The substrate 111 may be made of a glass or polymer, and may have a rigid or flexible property.

The first driving electrode DE 1 may be supplied with a first driving signal DS 1 to sense a mutual capacitance change between the first driving electrode DE 1 and the sensing electrode SE by a user touch and detect a touch position. The first driving signal DS 1 may be, for example, a driving signal of a pulse waveform, and the first driving signal DS 1 may be referred to as a pulse waveform driving signal DS 1 .

Each first driving electrode DE 1 may be configured to include a plurality of first driving electrode patterns PD 1 that are arranged along the first direction and are electrically connected to each other.

Each sensing electrode SE crossing each first driving electrode DE 1 to form a mutual capacitance may be configured to include a plurality of sensing electrode patterns PS that are arranged along the second direction and are electrically connected to each other.

The second driving electrode DE 2 may be supplied with a second driving signal DS 2 to sense an impedance change by a user touch and recognize a user (or detect a user ID). The second driving signal DS 2 may be, for example, a driving signal of a frequency sweep (or sweep frequency) waveform, and the second driving signal DS 2 may be referred to as a frequency sweep (or sweep frequency) driving signal DS 2 . The second driving signal DS 2 is a band frequency driving signal in which signals in a predetermined frequency band (e.g., 10 Hz˜10 MHz) are mixed.

Each second driving electrode DE 2 corresponds to and overlaps each sensing electrode SE, and is configured to be exposed to the outside such that a user directly contacts the second driving electrode DE 2 at a user touch. Accordingly, at a user touch, a resistor (substantially a user's resistor) Ru between the second driving electrode DE 2 and the sensing electrode SE, and a capacitor Cu between a user and the sensing electrode SE are produced, and thus a RC series circuit can be produced.

It is preferable that, to minimize a mutual capacitance between the second driving electrode DE 2 and the sensing electrode SE, the second driving electrode DE 2 is formed to have a size, as small as possible, less than that of the sensing electrode SE. By minimizing the mutual capacitance between the second driving electrode DE 2 and the sensing electrode SE, an effect, by a capacitance between the second driving electrode DE 2 and the second electrode SE, on an RCL impedance in operation of the second driving electrode DE 2 can be minimized, and thus a detection capability of a user recognition according to an impedance change can be improved.

Further, it is preferable that, to minimize a mutual capacitance between the second driving electrode DE 2 and the first driving electrode DE 1 , they do not overlap each other.

Each second driving electrode DE 2 may be configured to include a plurality of second driving electrode patterns PD 2 that are arranged along the second direction and are electrically connected to each other. Alternatively, each second driving electrode DE may extend along the first direction.

The second driving electrode DE 2 may be partially exposed to the outside for a user's contact. For example, a part of each second driving electrode pattern PD 2 may be exposed. In this regard, referring to FIG. 2 , an exposing hole He exposing a part of the second driving electrode pattern PD 2 is formed in the protection layer 113 covering the second driving electrode pattern PD 2 , and thus a user can directly contact the second driving electrode pattern PD 2 .

The first driving circuit 120 outputs the first driving signal DS 1 to the corresponding first driving electrode DE 1 . For example, in each frame, the first driving signal DS 1 is sequentially supplied to the plurality of first driving electrodes DE 1 by a predetermined period, for example, one or more horizontal period of the touch screen 110 .

The first driving circuit 120 may include a first current source IS 1 generating a pulse waveform signal, and a plurality of first switches SW 1 that are connected to the respective first driving electrodes DE 1 , and switch and output the pulse waveform signal, input thereto, at respective output timings to the respective first driving electrodes DE 1 .

The second driving circuit 130 outputs the second driving signal DS 2 to the corresponding second driving electrode DE 2 . For example, in each frame, the second driving signal DS 2 is sequentially or simultaneously supplied to the plurality of second driving electrodes DE 2 by a predetermined period, for example, one or more horizontal period of the touch screen 110 .

The second driving circuit 130 may include a second current source IS 2 generating a frequency sweep signal, and a plurality of second switches SW 2 that are connected to the respective second driving electrodes DE 2 , and switch and output the frequency sweep signal, input thereto, at respective output timings to the respective second driving electrodes DE 2 .

The second electrode DE 2 is a driving electrode operated for a user detection (i.e., a user recognition) by an impedance change (i.e., an RCL impedance change), and performs a function different from the first driving electrode DE 1 for detection of a user touch position. Accordingly, it may be not necessary that the second driving signal DS 2 is sequentially supplied to the plurality of second driving electrodes DE 2 by a predetermined period. Thus, the second electrodes DE 2 are sequentially selected and supplied with the second driving signal DS 2 by a predetermined period, or are simultaneously selected and supplied with the second driving signal DS 2 by a predetermined period.

The read-out circuit 140 is connected to the sensing electrodes SE, and senses analog sensing signals SS, output from the sensing electrodes SE, during a sensing period. A sensing period may be referred to herein as a sensing time. Such a “sensing time” does not imply a particular instant in time; rather, the “sensing time” is a period of time in which sensing may be performed.

The read-out circuit 140 may include a first channel selection circuit 141 , a second channel selection circuit 142 , a first detection circuit 150 , a second detection circuit 160 , an inductor L, and an analog-to-digital (AD) circuit 170 .

The first channel selection circuit 141 includes a plurality of input channels connected to the respective sensing electrodes SE, and sequentially selects the plurality of input channels and outputs a signal of the selected input channel. In other words, the first channel selection circuit 141 sequentially selects the plurality of sensing electrodes SE and outputs a sensing signal SS of the selected sensing electrode SE. The first channel selection circuit 141 may be configured with a multiplexer.

The second channel selection circuit 142 is supplied with the sensing signal SS from the first channel selection circuit 141 . The second channel selection circuit 142 outputs the sensing signal SS to the first detection circuit 150 through its first output channel when the sensing signal SS is a first sensing signal SS 1 produced by the first driving signal DS 1 , and outputs the sensing signal SS to the second detection circuit 160 through its second output channel when the sensing signal SS is a second sensing signal SS 2 produced by the second driving signal DS 2 . The second channel selection circuit 142 may be configured with a demultiplexer.

For example, in each horizontal period, during a first sensing time when the first driving signal DS 1 is applied, the first sensing signal SS 1 to sense a mutual capacitance is produced. The first sensing signal SS 1 during the respective first sensing times are selected by the first channel selection circuit 141 and output to the second channel selection circuit 142 , and during the first sensing time, the second channel selection circuit 142 transfers the first sensing signal SS 1 to the first detection circuit 150 .

In each horizontal period, during a second sensing time when the second driving signal DS 2 is applied, the second sensing signal SS 2 to sense an impedance (i.e., an RC impedance) is produced. The second sensing signals SS 2 during the respective second sensing times are sequentially selected by the first channel selection circuit 141 and output to the second channel selection circuit 142 , and during the second sensing time, the second channel selection circuit 142 transfers the second sensing signal SS 2 to the second detection circuit 160 .

The first detection circuit 150 serves to detect the first sensing signal SS 1 and measure a mutual capacitance, and may include a sample hold circuit 151 and a low pass filter 152 .

The sample hold circuit 151 samples and holds the first sensing signal SS 1 input thereto and outputs it into a voltage signal. The low pass filter 152 removes a high frequency noise from the signal that is output from the sample hold circuit 151 , and outputs the noise-removed signal.

The first detection circuit 150 is supplied with the first sensing signal SS 1 and detects a mutual capacitance, and thus a user touch position according to a mutual capacitance change can be decided.

The second detection circuit 160 serves to detect the second sensing signal SS 2 and measure an impedance change (i.e., an RCL impedance change), and may include a transimpedance amplifier 161 and a log amplifier 162 .

The transimpedance amplifier 161 amplifies the second sensing signal SS 2 input thereto and output the amplified signal into a voltage signal. The log amplifier 162 detects and outputs a magnitude component (i.e., an envelope) of the signal input thereto.

The inductor L is connected between the second detection circuit 160 and the second channel selection circuit 142 , and is connected electrically in series to the sensing electrode SE during the second sensing time when the second sensing signal SS 2 is input. Accordingly, referring to FIG. 3 , the inductor L is connected in series to a user's resistor Ru and a user's capacitor Cu between the user and the sensing electrode SE, and thus an RCL series circuit is produced.

Accordingly, an RCL impedance of the RCL series circuit is reflected in the second sensing signal SS 2 and this second sensing signal SS 2 is input to the second detection circuit 160 . Thus, the second detection circuit 160 can detect the RCL impedance, and a user ID according to an impedance change can be decided.

Further, an RCL band pass filter as the RCL series circuit is used for a user recognition, and an RCL band pass filter has a wider gain range, due to its characteristics, than that of the related art RLC band cut filter. Thus, a user recognition capability i.e., a user detection capability can be improved.

An analog detection signal detected by each of the first and second detection circuits 150 and 160 is input to the AD circuit 170 , and then is converted into a digital signal and output.

A method of driving the touch sensing system 100 of this embodiment is explained further with reference to FIG. 4 . FIG. 4 is a timing chart of driving signals and a sensing signal of the touch sensing system according to the first embodiment of the present disclosure.

In each frame, both of a mutual capacitance sensing and an RCL impedance sensing may be conducted with a time division (or a time sharing) by a predetermined period, for example, a horizontal period H. Alternatively, the predetermined period for the sensing may be two or more horizontal periods of the touch screen 110 .

At least part of a first half A of each horizontal period H is the first sensing time SP 1 , and for the first sensing time SP 1 , the first driving signal DS 1 is applied to the first driving electrode DE selected in the corresponding horizontal period H. At least part of a second half B of each horizontal period H is the second sensing time SP 2 , and for the second sensing time SP 2 , the second driving signal DS 2 is applied to the second driving electrode DE 2 selected in the corresponding horizontal period H (or all the second driving electrodes DE 2 ). A sequence of the first sensing time SP 1 and the second sensing time SP 2 may be reversed.

In the first sensing time SP 1 , the first sensing signal SS 1 i.e., a mutual capacitance sensing signal is produced by the first driving signal DS 1 , and is input to and detected by the first detection circuit 150 .

Accordingly, a mutual capacitance by a user touch is measured and thus a user touch position is detected.

In the second sensing time SP 2 , the second sensing signal SS 2 i.e., an RC impedance sensing signal is produced by the second driving signal DS 2 , the inductor L is electrically connected to the sensing electrode SE thus a RCL series circuit is made, and an RCL impedance sensing signal due to the RCL series circuit is input to and detected by the second detection circuit 160 .

Accordingly, an impedance by a user touch is measured and thus a user recognition is achieved.

In this embodiment, the first driving electrode DE 1 and the sensing electrode SE may be formed in a display panel. This configuration is explained with reference to FIG. 5 . FIG. 5 is a cross-sectional view illustrating an example of a display device including a display panel and a touch panel according to the first embodiment of the present disclosure.

Referring to FIG. 5 , a display panel 200 may use a liquid crystal panel. The display panel 200 may include an array substrate 210 , and an opposing substrate 220 , for example, a color filter substrate 220 facing and coupled to the array substrate 210 with a liquid crystal layer 230 therebetween. In the array substrate 210 , a plurality of pixels may be arranged, in a matrix form, along a plurality of row lines and a plurality of column lines, and a pixel electrode supplied with a corresponding data signal is formed in each pixel.

A touch panel 115 is attached on the opposing substrate 220 of the display panel 200 .

The first driving electrode DE 1 and the sensing electrode SE of the touch screen 110 may be formed at the array substrate 210 of the display panel 200 . Further, each of the first driving electrode DE 1 and the sensing electrode SE may serve as a common electrode that faces a pixel electrode to operate liquid crystal molecules of the liquid crystal layer 230 .

The second driving electrode DE 2 may be formed at the touch panel 115 .

As such, the first driving electrode DE 1 and the sensing electrode SE may be formed in an in-cell structure and serve as a common electrode supplied with a common voltage. In this case, per a frame, an image display, and a mutual capacitance sensing and an impedance sensing may be performed with a time division (or a time sharing).

This is explained further with reference to FIG. 6 , which is a timing chart of first and second driving signals and a sensing signal in an example that a first driving electrode and a sensing electrode of a touch screen is formed in a display panel according to the first embodiment of the present disclosure.

Referring to FIG. 6 , per a frame, in each horizontal period H, the first sensing time SP 1 as a mutual capacitance sensing time, the second sensing time SP 2 as an impedance sensing time, and a display period DP (which may be referred to herein as a “display time”) as an image display period (or “image display time”) of the display panel 200 may be time-divided from each other.

For example, in a first half A of the horizontal period H, the first sensing time SP 1 and the display time DP i.e., a first display time DP 1 may be divided from each other in a sequence, and in a second half B of the horizontal period H, the second sensing time SP 2 and the display time DP i.e., a second display time DP 2 may be divided from each other in a sequence. That is, the display time DP, which may include both the first and second display times DP 1 , DP 2 , is temporally separated from the first sensing time SP 1 and the second sensing time SP 2 . Positions of the first and second sensing times SP 1 and SP 2 may be reversed.

In this case, per the horizontal period H, in the first sensing time SP 1 , the first driving signal DS 1 is applied to the first driving electrode DE 1 , and the first sensing signal SS 1 is detected. Then, in the first display time DP 1 , data signals are written to pixels on corresponding row lines of the display panel 200 and an image display is performed. Then, in the second sensing time SP 2 , the second driving signal DS 2 is applied to the second driving electrode DE 2 , and the second sensing signal SS 2 is detected. Then, in the second display time DP 2 , data signals are written to pixels on corresponding row lines of the display panel 200 and an image display is performed.

During the display time DP and the second sensing time SP 2 , except for the first sensing time SP 1 , of the horizontal period H, the first driving electrode DE 1 may be supplied with a common voltage Vcom. During the display time DP, except for the first and second sensing time SP 1 and SP 2 , of the horizontal period H, the sensing electrode SE may be supplied with a common voltage Vcom. Further, during times, except for horizontal periods when sensing operations are conducted, of a frame, the first driving electrode DE 1 and the sensing electrode SE may be supplied with a common voltage Vcom. In other words, in a frame, times except for the first and second sensing times SP 1 and SP 2 are display times, and during the display times, the first driving electrode DE 1 and the sensing electrode SE may be supplied with a common voltage Vcom.

As such, in the case that the first driving electrode DE 1 and the sensing electrode SE is configured with the in-cell structure, during times except for the corresponding sensing times, the common voltage Vcom is supplied, and thus the first driving electrode DE 1 and the sensing electrode SE can each serve as a common electrode.

FIG. 7 is a view illustrating a user recognition by an impedance measurement according to the first embodiment of the present disclosure. FIG. 7 shows a graph of a frequency to an impedance.

Referring to FIG. 7 , it is seen that at a resonance frequency of about 1.4E+06 Hz, peak values of different impedances are measured differently. Accordingly, since users have different resistors thus have different RCL impedances, by an impedance measurement, a user can be effectively recognized.

As described above, in this embodiment, the touch screen is configured using the first driving electrode applied with the first driving signal of a pulse waveform, the second driving electrode applied with the second driving signal of a frequency sweep waveform, and the sensing electrode sensing the sensing signal for each of the first and second driving signals.

Accordingly, a user touch position is determined through a mutual capacitance detection, and a user is recognized (or identified) through a RCL impedance detection.

Thus, the related art two touch panel used for a user touch position and a user recognition, respectively, is not required. Therefore, a cost and a thickness of a touch sensing system can be reduced, and a cost and a thickness of a display device using the touch sensing system can be reduced.

Further, since a RCL band pass filter, of a wide gain range, configured with a RCL series circuit is used at a RCL impedance detection, a user recognition capability can be improved.

[Second Embodiment]

The above first embodiment relates to a touch sensing system that produces an RCL series circuit at a user touch, measures its impedance, and achieves a user recognition.

This second embodiment relates to a touch sensing system that produces a CRCL series circuit at a user touch, measures its impedance, and achieves a user recognition.

For the purpose of explanations, explanations of parts similar to parts of the first embodiment may be omitted.

FIG. 8 is a plan view illustrating a touch sensing system according to a second embodiment of the present disclosure, and FIG. 9 is a cross-sectional view taken along a line IX-IX of FIG. 8 . FIG. 9 shows an example that a touch screen is formed as a touch panel.

Referring to FIG. 8 , the touch sensing system 100 of this embodiment includes a touch screen 110 in which driving electrodes DE and sensing electrodes SE to sense a user touch are located, and a driving circuit to operate the electrodes DE and SE of the touch screen 110 . The driving circuit includes a driving circuit 125 , and a read-out circuit 140 .

The touch screen 110 is arranged to correspond to a display region of a display panel of a display device and senses a user touch on a display surface of the display panel. The touch screen 110 may be manufactured separately from the display panel and be attached to the display panel.

Referring to FIGS. 8 and 9 , the touch screen 110 includes a plurality of driving electrodes DE extending, parallel with each other, along a first direction (e.g., a horizontal direction or a X direction), and a plurality of sensing electrodes SE extending, parallel with each other, along a second direction (e.g., a vertical direction or a Y direction) crossing the first direction.

In this embodiment, an example, as shown in FIG. 9 , that the driving electrode DE and the sensing electrode SE are formed on a substrate 111 , a protection layer (or a dielectric layer) 113 made of an insulating material is formed entirely on the substrate 111 having the driving electrode DE and the sensing electrode SE.

A configuration other than the above configuration may be employed. For example, the driving electrode DE and the sensing electrode SE may be located at different layers with a dielectric layer therebetween. For other example, at least one of the driving electrode DE and the sensing electrode SE may be located below the substrate 111 .

The substrate 111 may be made of a glass or polymer, and may have a rigid or flexible property.

The touch screen 110 of this embodiment does not employ the second driving electrode DE 2 of the first embodiment but employs the driving electrode DE having both of the functions of the first and second driving electrodes DE 1 and DE 2 of the first embodiment.

Accordingly, the driving electrode DE is selectively supplied with a first driving signal DS 1 of a pulse waveform to detect a mutual capacitance change and a second driving signal DS 2 of a frequency sweep waveform to detect an impedance change.

In this regard, a mutual capacitance is produced between the driving electrode DE and the sensing electrode SE, and changes according to a user touch. Further, at a user touch, a capacitor Cu 1 between the driving electrode DE and a user, a user's resistor Ru, and a capacitor Cu 2 between a user and the sensing electrode SE are produced, and thus a CRC series circuit is produced.

Accordingly, when the first driving signal DS 1 is applied, a mutual capacitance produced between the driving electrode DE and the sensing electrode SE by a user touch is detected. When the second driving signal DS 2 is applied, an impedance of a CRCL series circuit produced with a CRC series circuit that is produced between the driving electrode DE and the sensing electrode SE by a user touch, and an inductor L, connected in series to the CRC series circuit, of the detection circuit 140 is detected.

Each driving electrode DE may be configured to include a plurality of driving electrode patterns PD that are arranged along the first direction and are electrically connected to each other.

Each sensing electrode SE crossing each driving electrode DE to form a mutual capacitance or an impedance may be configured to include a plurality of sensing electrode patterns PS that are arranged along the second direction and are electrically connected to each other.

The driving circuit 125 outputs the first driving signal DS 1 and the second driving signal DS 2 to each driving electrode DE with a time division. For example, in each frame, the driving circuit 125 supplies the first driving signal DS 1 sequentially to the plurality of driving electrodes DE by a predetermined period. Further, the driving circuit 125 supplies the second driving signal DS 2 sequentially or simultaneously to the plurality of driving electrodes DE by a predetermined period. The predetermined period may be, for example, one or more horizontal period of the touch screen 110 .

The driving circuit 125 may include a first current source IS 1 generating a pulse waveform signal, a second current source IS 2 generating a frequency sweep signal, and a plurality of selection switches SWS that are connected to the respective driving electrodes DE, and selectively switch the pulse waveform signal and the frequency sweep signal at respective output timings and output the selected signals to the respective driving electrodes DE.

The driving electrode DE is operated for a user touch position by a mutual capacitance change and for a user recognition by an impedance change (i.e., an CRCL impedance change) as well. Accordingly, it may be not necessary that the second driving signal DS 2 is sequentially supplied to the plurality of electrodes DE by a predetermined period. Thus, the driving electrodes DE are sequentially selected and supplied with the second driving signal DS 2 by a predetermined period, or are simultaneously selected and supplied with the second driving signal DS 2 by a predetermined period.

The read-out circuit 140 is connected to the sensing electrodes SE, and senses analog sensing signals SS, output from the sensing electrodes SE, during a sensing time.

The read-out circuit 140 may include a first channel selection circuit 141 , a second channel selection circuit 142 , a first detection circuit 150 , a second detection circuit 160 , an inductor L, and an analog-to-digital (AD) circuit 170 .

The first channel selection circuit 141 includes a plurality of input channels connected to the respective sensing electrodes SE, and sequentially selects the plurality of input channels and outputs a signal of the selected input channel. In other words, the first channel selection circuit 141 sequentially selects the plurality of sensing electrodes SE and outputs a sensing signal SS of the selected sensing electrode SE.

The second channel selection circuit 142 is supplied with the sensing signal SS from the first channel selection circuit 141 . The second channel selection circuit 142 outputs the sensing signal SS to the first detection circuit 150 through its first output channel when the sensing signal SS is a first sensing signal SS 1 produced by the first driving signal DS 1 , and outputs the sensing signal SS to the second detection circuit 160 through its second output channel when the sensing signal SS is a second sensing signal SS 2 produced by the second driving signal DS 2 .

For example, in each horizontal period, during a first sensing time when the first driving signal DS 1 is applied, the first sensing signal SS 1 to sense a mutual capacitance is produced. The first sensing signal SS 1 during the respective first sensing times are selected by the first channel selection circuit 141 and output to the second channel selection circuit 142 , and during the first sensing time, the second channel selection circuit 142 transfers the first sensing signal SS 1 to the first detection circuit 150 .

In each horizontal period, during a second sensing time when the second driving signal DS 2 is applied, the second sensing signal SS 2 to sense an impedance (i.e., a CRC impedance) is produced. The second sensing signals SS 2 during the respective second sensing times are sequentially selected by the first channel selection circuit 141 and output to the second channel selection circuit 142 , and during the second sensing time, the second channel selection circuit 142 transfers the second sensing signal SS 2 to the second detection circuit 160 .

The first detection circuit 150 serves to detect the first sensing signal SS 1 and measure a mutual capacitance, and may include a sample hold circuit 151 and a low pass filter 152 .

The first detection circuit 150 is supplied with the first sensing signal SS 1 and detects a mutual capacitance, and thus a user touch position according to a mutual capacitance change can be decided.

The second detection circuit 160 serves to detect the second sensing signal SS 2 and measure an impedance change (i.e., a CRCL impedance change), and may include a transimpedance amplifier 161 and a log amplifier 162 .

The inductor L is connected between the second detection circuit 160 and the second channel selection circuit 142 , and is connected electrically in series to the sensing electrode SE during the second sensing time when the second sensing signal SS 2 is input. Accordingly, referring to FIG. 10 , the inductor L is connected in series to a capacitor Cu 1 between the driving electrode DE and the user, a user's resistor Ru and a user's capacitor Cu 2 between the user and the sensing electrode SE, and thus a CRCL series circuit is produced.

Accordingly, a CRCL impedance of the CRCL series circuit is reflected in the second sensing signal SS 2 and this second sensing signal SS 2 is input to the second detection circuit 160 . Thus, the second detection circuit 160 can detect the CRCL impedance, and a user ID according to an impedance change can be decided.

Further, a CRCL band pass filter as the CRCL series circuit is used for a user recognition, and a CRCL band pass filter is substantially an RCL band pass filter. A CRCL band pass filter has a wider gain range, due to its characteristics, than that of the related art RLC band cut filter. Thus, a user recognition capability i.e., a user detection capability can be improved.

An analog detection signal detected by each of the first and second detection circuits 150 and 160 is input to the AD circuit 170 , and then is converted into a digital signal and output.

A method of driving the touch sensing system 100 of this embodiment is explained further with reference to FIG. 11 . FIG. 11 is a timing chart of driving signals and a sensing signal of the touch sensing system according to the second embodiment of the present disclosure.

In each frame, both of a mutual capacitance sensing and an impedance sensing may be conducted with a time division (or a time sharing) by a predetermined period, for example, a horizontal period H. Alternatively, the predetermined period for the sensing may be two or more horizontal periods of the touch screen 110 .

At least part of a first half A of each horizontal period H is the first sensing time SP 1 , and for the first sensing time SP 1 , the first driving signal DS 1 is applied to the driving electrode DE of the corresponding horizontal period H. At least part of a second half B of each horizontal period H is the second sensing time SP 2 , and for the second sensing time SP 2 , the second driving signal DS 2 is applied to the driving electrode DE of the corresponding horizontal period H (or all the driving electrodes DE). A sequence of the first sensing time SP 1 and the second sensing time SP 2 may be reversed.

In the first sensing time SP 1 , the first sensing signal SS 1 i.e., a mutual capacitance sensing signal is produced by the first driving signal DS 1 , and is input to and detected by the first detection circuit 150 .

Accordingly, a mutual capacitance by a user touch is measured and thus a user touch position is detected.

In the second sensing time SP 2 , the second sensing signal SS 2 i.e., a CRC impedance sensing signal is produced by the second driving signal DS 2 , the inductor L is electrically connected to the sensing electrode SE thus a CRCL series circuit is made, and an CRCL impedance sensing signal due to the CRCL series circuit is input to and detected by the second detection circuit 160 .

Accordingly, an impedance by a user touch is measured and thus a user recognition is achieved.

In this embodiment, the driving electrode DE and the sensing electrode SE may be formed in a display panel. This configuration is explained with reference to FIG. 12 . FIG. 12 is a cross-sectional view illustrating an example of a display device including a display panel and a touch panel according to the second embodiment of the present disclosure.

Referring to FIG. 12 , a display panel 200 may use a liquid crystal panel. The display panel 200 may include an array substrate 210 , and an opposing substrate 220 , for example, a color filter substrate 220 facing and coupled to the array substrate 210 with a liquid crystal layer 230 therebetween. In the array substrate 210 , a plurality of pixels may be arranged, in a matrix form, along a plurality of row lines and a plurality of column lines, and a pixel electrode supplied with a corresponding data signal is formed in each pixel.

The driving electrode DE and the sensing electrode SE of the touch screen 110 may be formed at the array substrate 210 of the display panel 200 . Further, each of the driving electrode DE and the sensing electrode SE may serve as a common electrode that faces a pixel electrode to operate liquid crystal molecules of the liquid crystal layer 230 .

As such, the driving electrode DE and the sensing electrode SE may be formed in an in-cell structure and serve as a common electrode supplied with a common voltage. In this case, per a frame, an image display, and a mutual capacitance sensing and an impedance sensing may be performed with a time division (or a time sharing).

This is explained further with reference to FIG. 13 , which is a timing chart of first and second driving signals and a sensing signal in an example that a driving electrode and a sensing electrode of a touch screen is formed in a display panel according to the second embodiment of the present disclosure.

Referring to FIG. 13 , per a frame, in each horizontal period H, the first sensing time SP 1 as a mutual capacitance sensing time, the second sensing time SP 2 as an impedance sensing time, and a display time DP as an image display time of the display panel 200 may be time-divided from each other.

For example, in a first half A of the horizontal period H, the first sensing time SP 1 and the display time DP i.e., a first display time DP 1 may be divided from each other in a sequence, and in a second half B of the horizontal period H, the second sensing time SP 2 and the display time DP i.e., a second display time DP 2 may be divided from each other in a sequence. Positions of the first and second sensing times SP 1 and SP 2 may be reversed.

In this case, per the horizontal period H, in the first sensing time SP 1 , the first driving signal DS 1 is applied to the driving electrode DE, and the first sensing signal SS 1 is detected. Then, in the first display time DP 1 , data signals are written to pixels on corresponding row lines of the display panel 200 and an image display is performed. Then, in the second sensing time SP 2 , the second driving signal DS 2 is applied to the driving electrode DE, and the second sensing signal SS 2 is detected. Then, in the second display time DP 2 , data signals are written to pixels on corresponding row lines of the display panel 200 and an image display is performed.

During the first and second display times DP 1 and DP 2 , except for the first and second sensing times SP 1 and SP 2 , of the horizontal period H, the driving electrode DE and the sensing electrode SE may be supplied with a common voltage Vcom. Further, during times, except for horizontal periods when sensing operations are conducted, of a frame, the driving electrode DE and the sensing electrode SE may be supplied with a common voltage Vcom. In other words, in a frame, times except for the first and second sensing times SP 1 and SP 2 are display times, and during the display times, the driving electrode DE and the sensing electrode SE may be supplied with a common voltage Vcom.

As such, in the case that the driving electrode DE and the sensing electrode SE is configured with the in-cell structure, during times except for the corresponding sensing times, the common voltage Vcom is supplied, and thus the driving electrode DE and the sensing electrode SE can each serve as a common electrode.

A structure other than the above structure of the touch screen 110 may be employed. For example, the touch screen 110 may have an on-cell structure and be configured on an outer surface of the opposing substrate 220 of the display panel 200 , and in this case, the driving electrode DE and the sensing electrode SE may be formed on the outer surface of the opposing substrate 220 while manufacturing the opposing substrate 220 . Further, a polarizing plate may be attached on the outer surface (i.e., a display surface of the display panel 200 ) of the opposing substrate having the driving electrode DE and the sensing electrode SE.

When the touch screen 110 is formed in an in-cell structure or on-cell structure, there is an advantage that a thickness of the touch screen 110 can be reduced.

As described above, in this embodiment, the touch screen is configured using the driving electrode applied with the first driving signal of a pulse waveform and the second driving signal of a frequency sweep waveform with a time division, and the sensing electrode sensing the sensing signal for each of the first and second driving signals.

Accordingly, a user touch position is determined through a mutual capacitance detection, and a user is recognized (or identified) through a CRCL impedance detection.

Thus, the related art two touch panel used for a user touch position and a user recognition, respectively, is not required. Therefore, a cost and a thickness of a touch sensing system can be reduced, and a cost and a thickness of a display device using the touch sensing system can be reduced.

Further, since a CRCL band pass filter, of a wide gain range, configured with a CRCL series circuit is used at a CRCL impedance detection, a user recognition capability can be improved.

It will be apparent to those skilled in the art that various modifications and variation can be made in the present disclosure without departing from the spirit or scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.