News Column

Patent Application Titled "Touch Sensing System and Method for Driving the Same" Published Online

June 12, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors Seo, Sangwoo (Daegu, KR); Lee, Jaedo (Gyeongsangbuk-do, KR); JEONG, Beom (Daejeon, KR); Choi, Sungpil (Gyeonggi-do, KR), filed on November 14, 2013, was made available online on May 29, 2014.

The assignee for this patent application is Lg Display Co., Ltd.

Reporters obtained the following quote from the background information supplied by the inventors: "Embodiments of the invention relate to a touch sensing system and a method for driving the same.

"User interface (UI) is configured so that users are able to communicate with various electronic devices and thus can easily and comfortably control the electronic devices as they desire. Examples of the user interface include a keypad, a keyboard, a mouse, an on-screen display (OSD), and a remote controller having an infrared communication function or a radio frequency (RF) communication function. User interface technology has continuously expanded to increase user's sensibility and handling convenience. The user interface has been recently developed to include touch UI, voice recognition UI, 3D UI, etc.

"A capacitive touch sensing system includes a capacitive touch screen which has durability and definition better than an existing resistive touch screen and is able to recognize a multi-touch input and a proximity touch input. Hence, the capacitive touch sensing system may be applied to various applications.

"The size of mobile information terminals using the touch UI is becoming larger and larger. Thus, the touch UI is expected to be applied to large-sized display devices such as computer monitors in the future. As the size of the touch screen increases, the length of lines used in the touch screen lengthens. Hence, a resistance and a capacitance of the touch screen increase, and an RC delay of a driving signal applied to the touch screen increases. FIGS. 1 and 2 illustrate examples of the RC delay.

"As the size of the touch screen increases, the RC delay varies depending on a position of the touch screen. Therefore, an amount of charges supplied to touch sensors of the touch screen varies, and a discharge delay of undesired remaining charges is caused in the touch sensors. Hence, a signal-to-noise ratio (often abbreviated SNR) of the signal read from the touch screen is not good. Because a length of a sensing period of the touch screen increases due to an increase in the size of the touch screen, a touch report rate is reduced. When the touch report rate is reduced, touch sensitivity is further reduced. Touch raw data obtained by sensing the touch sensors of the touch screen during the sensing period is analyzed to calculate coordinates of the touch raw data, and coordinate informations of the touch raw data are gathered. The touch report rate is a velocity or a frequency, at which the gathered coordinate informations are transmitted to an external host system. As the touch report rate increases, a latency between a touch input and a coordinate recognition is reduced. Therefore, the touch sensitivity a user feels increases.

"FIG. 1 illustrates a portion of a mutual capacitive touch screen. In FIG. 1, Tx1 to Tx5 denote Tx lines to which a driving signal is applied, and Rx1 to Rx6 denote Rx lines receiving voltages of touch sensors Cm. A mutual capacitive touch screen TSP is connected to a readout integrated circuit (ROIC) which drives the touch screen TSP and receives the voltages of the touch sensors Cm. The ROIC applies the driving signal to the Tx lines Tx1 to Tx5 and receives the voltages of the touch sensors Cm through the Rx lines Rx1 to Rx6.

"If the touch sensors Cm close to the ROIC have a small RC delay, there is an increase in an amount of charges .DELTA.Q1 (refer to FIG. 2) charged when the driving signal is applied to the touch sensors Cm close to the ROIC. On the other hand, if the touch sensors Cm far away from the ROIC have a large RC delay, there is a reduction in an amount of charges .DELTA.Q2 (refer to FIG. 2) charged when the driving signal is applied to the touch sensors Cm far away from the ROIC. As the RC delay increases, a discharge time of the touch sensors Cm increases. Thus, as the touch sensors Cm are far away from a portion of the touch screen TSP to which the driving signal is applied, an amount of charges charged to the touch sensors Cm decreases due to the RC delay, and a discharge of remaining charges is delayed."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "Embodiments of the invention provide a touch sensing system and a method for driving the same uniformalizing the charge characteristics of the touch sensors over the whole surface of the large size touch screen.

"In one aspect, there is a touch sensing system comprising a touch screen including touch sensors and a touch sensing circuit configured to apply a driving signal to the touch sensors.

"The touch sensing circuit applies at least one first driving signal to a first position of the touch screen and applies at least one second driving signal to a second position of the touch screen.

"When RC delay of the first position is less than RC delay of the second position, at least one of a width and a voltage of the second driving signal is greater than the first driving signal, or the number of second driving signals is more than the number of first driving signals.

"In another aspect, there is a method for driving a touch sensing system comprising applying at least one first driving signal to a first position of the touch screen and applying at least one second driving signal to a second position of the touch screen.

BRIEF DESCRIPTION OF THE DRAWINGS

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

"FIG. 1 illustrates a portion of a mutual capacitive touch screen;

"FIG. 2 illustrates an non-uniformity of an amount of charges charged to touch sensors due to an RC delay of a touch screen;

"FIG. 3 illustrates a touch sensing system according to an exemplary embodiment of the invention;

"FIG. 4 is an equivalent circuit diagram of a touch screen shown in FIG. 3;

"FIGS. 5 to 7 illustrate various combinations of a touch screen and a display panel according to an exemplary embodiment of the invention;

"FIG. 8 is a circuit diagram of an integrator of an Rx driving circuit;

"FIG. 9 is a waveform diagram showing changes in a voltage of a touch sensor before and after a touch operation;

"FIG. 10 is a waveform diagram showing driving signals according to a first embodiment of the invention;

"FIG. 11 is a waveform diagram showing changes in an amount of charges of touch sensors through a comparison between a related art driving signal and a driving signal shown in FIG. 10 according to an exemplary embodiment of the invention;

"FIG. 12 illustrates an example of connecting a touch screen and a touch sensing circuit in a touch sensing system according to an exemplary embodiment of the invention;

"FIG. 13 illustrates a method for dividedly driving a touch screen in a touch sensing system according to an exemplary embodiment of the invention;

"FIG. 14 is a waveform diagram showing driving signals according to a second embodiment of the invention;

"FIG. 15 is a waveform diagram showing driving signals according to a third embodiment of the invention;

"FIG. 16 is a waveform diagram showing driving signals according to a fourth embodiment of the invention;

"FIG. 17 is a circuit diagram of a driving signal generator according to an exemplary embodiment of the invention;

"FIG. 18 is a waveform diagram showing on/off timings and an output waveform of switches in a driving signal generator shown in FIG. 17;

"FIG. 19 is a circuit diagram of a driving signal generator according to another embodiment of the invention;

"FIG. 20 is a waveform diagram showing an output waveform of a driving signal generator according to a fifth embodiment of the invention;

"FIG. 21 is a waveform diagram showing driving signals according to a sixth embodiment of the invention;

"FIG. 22 is a waveform diagram showing changes in a charge amount when a width of driving signals shown in FIG. 21 changes;

"FIG. 23 is an exemplary circuit diagram of a driving signal generator outputting driving signals shown in FIG. 21;

"FIG. 24 is a waveform diagram showing input and output signals of a driving signal generator shown in FIG. 23;

"FIG. 25 is a waveform diagram showing driving signals according to a seventh embodiment of the invention;

"FIG. 26 is a waveform diagram showing driving signals according to an eighth embodiment of the invention;

"FIG. 27 is a waveform diagram showing driving signals according to a ninth embodiment of the invention;

"FIG. 28 is a waveform diagram showing driving signals according to a tenth embodiment of the invention;

"FIG. 29 is a waveform diagram showing driving signals according to an eleventh embodiment of the invention; and

"FIG. 30 shows an example of connecting a plurality of touch ICs to a touch screen."

For more information, see this patent application: Seo, Sangwoo; Lee, Jaedo; JEONG, Beom; Choi, Sungpil. Touch Sensing System and Method for Driving the Same. Filed November 14, 2013 and posted May 29, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4444&p=89&f=G&l=50&d=PG01&S1=20140522.PD.&OS=PD/20140522&RS=PD/20140522

Keywords for this news article include: Lg Display Co. Ltd.

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Source: Politics & Government Week


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