PATENT DOCUMENT

Publication Number: US-9626046-B2
Application Number: US-201314035104-A
Country: US
Kind Code: B2

Title: Devices and methods for reduction of display to touch crosstalk

Abstract:
Devices and methods for reducing display-to-touch crosstalk are provided. In or more examples, an electronic display panel may include a pixel. The pixel may include a pixel electrode, a common electrode, and a first transistor having a first source coupled to a data line, a first gate coupled to a gate line, and a first drain coupled to the pixel electrode. The pixel may also include a second transistor having a second source coupled to the common electrode, a second gate coupled to the gate line, and a second drain coupled to a common voltage source. The second transistor may be configured to cause a parasitic capacitance between the gate line and the second drain of the second transistor and to reduce an effect of a parasitic capacitance between the gate line and the first drain of the first transistor.

Claims:
What is claimed is: 
     
       1. A display panel, comprising:
 a unit pixel, including:
 a unit pixel electrode; 
 a first common electrode; 
 a first transistor having a first source coupled to a data line, a first gate coupled to a gate line, and a first drain coupled to the unit pixel electrode, wherein the first transistor is configured to pass a data signal from the data line to the unit pixel electrode upon receipt of an activation signal from the gate line; and 
 a second transistor having a second source coupled to the first common electrode, a second gate coupled to the gate line, and a second drain coupled to a common voltage source, wherein the second transistor is configured to cause a parasitic capacitance between the gate line and the second drain of the second transistor and to reduce an effect of a parasitic capacitance between the gate line and the first drain of the first transistor; 
 
 wherein the first common electrode of the unit pixel is configured to operate, while in a touch mode, as a touch sense electrode that detects a touch capacitance formed between the first common electrode and a second common electrode of another unit pixel, wherein the second common electrode is configured to operate, in the touch mode, as a touch drive electrode, wherein the touch capacitance is indicative of a touch or hover over the display panel. 
 
     
     
       2. The display panel of  claim 1 , wherein the first transistor is configured to pass displayable image data as the data signal to the unit pixel electrode. 
     
     
       3. The display panel of  claim 1 , wherein the second transistor is configured to receive a control signal to switch between one of an activated state or a deactivated state to control a voltage on the first common electrode, and wherein, in the deactivated state, the second drain of the second transistor is configured to allow the common voltage signal to charge the parasitic capacitance. 
     
     
       4. The display panel of  claim 1 , comprising a third transistor, wherein the first common electrode is communicatively coupled to the second drain of the second transistor and the second common electrode is communicatively coupled to a third drain of the third transistor, and wherein the parasitic capacitance is formed along a conductive path between the first common electrode and the second common electrode. 
     
     
       5. The display panel of  claim 1 , wherein the second transistor is configured to transmit a common voltage signal to the first common electrode upon receipt of a second activation signal from the gate line, and wherein the second transistor is configured to not transmit the common voltage signal when deactivated. 
     
     
       6. The display panel of  claim 5 , wherein, in a display mode, the second transistor is configured to transmit the common voltage signal to the first common electrode at substantially the same time the first transistor is configured to pass the data signal to the unit pixel electrode. 
     
     
       7. The display panel of  claim 5 , wherein, in a touch mode, the first transistor and the second transistor are configured to deactivate, during which time the display panel is configured to detect one or more touches or hovers on the display panel. 
     
     
       8. An electronic device, comprising:
 a liquid crystal display (LCD) panel comprising a plurality of unit pixels, wherein each of the plurality of unit pixels comprises a first transistor, a second transistor, and a unit pixel electrode formed there between; 
 a gate driver configured to transmit a signal to switch the first transistor and the second transistor to one of an activated state or a deactivated state, wherein, in the activated state, the first transistor is configured to supply image data to the unit pixel electrode; and 
 a touch controller configured to generate a touch drive signal to stimulate one or more touch drive voltage common (VCOM) electrodes and to receive a touch sense signal from one or more touch sense VCOM electrodes as an indication of a touch or hover of the LCD, wherein the second transistor is configured to substantially reduce an effect of a capacitive coupling between the unit pixel electrode and the touch drive signal or between the unit pixel electrode and the touch sense signal, and wherein the touch sense signal is configured to vary based on a touch capacitance formed between the one or more touch drive VCOM electrodes and the one or more touch sense VCOM electrodes. 
 
     
     
       9. The electronic device of  claim 8 , wherein the plurality of unit pixels comprises an array of display pixels. 
     
     
       10. The electronic device of  claim 8 , wherein the plurality of unit pixels comprises an array of touch pixels. 
     
     
       11. The electronic device of  claim 8 , wherein the gate driver is configured to transmit the signal to switch the first transistor and the second transistor to the deactivated state, and wherein the touch controller is configured to generate the touch drive signal to stimulate the one or more touch drive VCOM electrodes when the first transistor and the second transistor are each in the deactivated state. 
     
     
       12. The electronic device of  claim 8 , wherein a change in the capacitance comprises an indication of the touch or hover of the LCD. 
     
     
       13. The electronic device of  claim 8 , wherein, in the activated state, the second transistor is configured to pass a common voltage signal to a common electrode formed between the first transistor and the second transistor, wherein the unit pixel electrode and the common electrode are configured to form a liquid crystal capacitance. 
     
     
       14. A method of reducing display-to-touch crosstalk, comprising:
 in a display mode of operation:
 supplying an activation signal to a first active switching device of a display pixel of an electronic display, wherein the first active switching device is configured to control a data signal supplied to a unit pixel electrode of the display pixel; 
 supplying an activation signal to a second active switching device of the display pixel, wherein the second active switching device is configured to control a common voltage signal supplied to a common electrode of the display pixel; and 
 
 in a touch mode of operation:
 deactivating the second active switching device, wherein deactivating the second active switching device comprises substantially reducing an effect of an occurrence of a parasitic capacitance between a gate line of the display pixel and a first common voltage (VCOM) electrode used in touch sensing in the electronic display; and 
 supplying a touch drive signal to the touch pixel to stimulate the touch pixel. 
 
 
     
     
       15. The method of  claim 14 , wherein supplying the activation signal to the first active switching device comprises activating the first active switching device to store image data to the unit pixel electrode. 
     
     
       16. The method of  claim 14 , wherein deactivating the second active switching device comprises deactivating the second active switching following a period of time in which the data signal is supplied to the unit pixel electrode. 
     
     
       17. The method of  claim 14 , wherein deactivating the second active switching) The method of  claim 14 , wherein reducing the occurrence of the parasitic capacitance between the display pixel and the touch pixel comprises reducing a dependence of the parasitic capacitance on a voltage of the unit pixel electrode. 
     
     
       18. The method of  claim 14 , comprising:
 receiving a touch sense signal from the touch pixel; and 
 determining a touch or hover of the electronic display based on the received touch sense signal, wherein a touch drive signal and the touch sense signal are substantially unmitigated by the parasitic capacitance. 
 
     
     
       19. An electronic device, comprising:
 a first thin-film transistor (TFT) of a unit pixel, wherein the first TFT comprises a first source, a first gate, and a first drain, wherein the first TFT is configured to transmit an image data signal from the first source to the first drain; 
 a second TFT of the unit pixel, wherein the second TFT comprises a second source, a second gate, and a second drain, wherein the second TFT is configured to transmit a common voltage signal from the second drain to the second source, wherein the first TFT is communicatively coupled to the second TFT, and wherein the first drain of the first TFT and the second source of the second TFT are configured to form a liquid crystal capacitance therebetween to store image data thereto; and 
 a row common voltage (VCOM) electrode and a column common voltage (VCOM) electrode coupled to the first TFT and the second TFT, wherein a touch capacitance is formed along a first conductive path between row VCOM electrode and the column VCOM electrode, and wherein a parasitic capacitance is formed along a second conductive path between row VCOM electrode and the column VCOM electrode to reduce any effect of another parasitic capacitance that may form along the first conductive path. 
 
     
     
       20. The electronic device of  claim 19 , wherein the second TFT is configured such that the common voltage signal on the second drain of the second TFT charges the parasitic capacitance in lieu of the image data signal on the first drain of the first TFT. 
     
     
       21. The electronic device of  claim 19 , wherein the touch capacitance is configured to provide an indication of a touch or hover of a display of the electronic device.

Description:
BACKGROUND 
     The present disclosure relates generally to electronic displays and, more particularly, to reducing crosstalk in electronic displays having touch screen sensor components within display pixel cells. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Electronic devices may employ a variety of user input devices, including buttons, mice, touch sensor panels, touch screens, and so forth. Touch screens, in particular, may be popular because of their ease and versatility of operation. Conventionally, touch screens may be flat panel displays such as liquid crystal displays (LCDs) or organic light emitting diode (OLED) displays overlaid with a touch panel. Such a touch screen may generally recognize the occurrence and position of touches on the screen, enabling the electronic device to respond appropriately. 
     Many touch screens may be formed from a capacitive touch sensor panel that is overlaid across an LCD. Such a capacitive touch sensor panel may be formed from some matrix of touch drive lines and touch sense lines. These touch drive and touch sense lines are often arranged in rows and columns on a substrate. When an object, such as a user&#39;s finger or stylus, is near an intersection of a touch drive line and a touch sense line, a capacitance between the touch drive line and touch sense line may change. This change in capacitance may indicate that a touch is occurring at this location. However, because touch screen components may be integrated into display pixel cells of the display (e.g., in-cell touch), the touch screen components may be susceptible to display-to-touch crosstalk (DTX), which may refer to a condition in which image data signals may adversely impact or distort sensed touch signals. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Embodiments of the present disclosure relate to devices and methods for reducing display-to-touch crosstalk. By way of example, an electronic display panel may include a pixel. The pixel may include a pixel electrode, a common electrode, and a first transistor having a first source coupled to a data line, a first gate coupled to a gate line, and a first drain coupled to the pixel electrode. The first transistor may be configured to pass a data signal from the data line to the pixel electrode upon receipt of an activation signal from the gate line. The pixel may also include a second transistor having a second source coupled to the common electrode, a second gate coupled to the gate line, and a second drain coupled to a common voltage source. The second transistor may be configured to cause a parasitic capacitance between the gate line and the second drain of the second transistor instead of between the gate line and the first drain of the first transistor. 
     Various refinements of the features noted above may exist in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a schematic block diagram of an electronic device with a liquid crystal display (LCD) having in-cell touch sensor components, in accordance with an embodiment; 
         FIG. 2  is a perspective view of a notebook computer representing an embodiment of the electronic device of  FIG. 1 ; 
         FIG. 3  is a front view of a hand-held device representing another embodiment of the electronic device of  FIG. 1 ; 
         FIG. 4  is a circuit diagram of switching a display circuitry of pixels of an LCD, in accordance with an embodiment; 
         FIG. 5  is a schematic block diagram illustrating an in-cell touch sensor subsystem of an LCD, in accordance with an embodiment; 
         FIG. 6  is a schematic block diagram of the multiple VCOMs of the LCD, in accordance with an embodiment; 
         FIG. 7  is a circuit diagram of one or more pixels of an LCD, in accordance with an embodiment; 
         FIG. 8  is a flowchart describing a display mode of operation and a touch mode of operation of an LCD, in accordance with an embodiment; 
         FIG. 9  is a flowchart illustrating an embodiment of a process suitable for reducing display-to-touch crosstalk when operating the LCD of  FIG. 8  in the display mode of operation, in accordance with an embodiment; and 
         FIG. 10  is a flowchart illustrating an embodiment of a process suitable for reducing display-to-touch crosstalk when operating the LCD of  FIG. 8  in the touch mode of operation, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     As previously noted, embodiments of the present disclosure relate to liquid crystal displays (LCDs) and electronic devices incorporating LCDs that employ touch sensor components within display pixel cells (“in-cell”). Specifically, in-cell touch technology (e.g., in-cell touch charge sensing) may be susceptible to display to-touch crosstalk (DTX). As used herein, “display to-touch crosstalk (DTX)” may refer to a condition in which image data (e.g., data signal voltage) adversely impacts and/or distorts a sensed touch signal. DTX may often appear touch when the touch sensing signal path travels through a conductive path in which a parasitic capacitance (Cgd) may be formed between the gate and drain of, for example, a thin film transistor (TFT) supplying the image data (e.g., pixel electrode voltage) to one or more pixel electrodes. Accordingly, it may be useful to include a second active switching device (e.g., a second TFT) to control the common voltage (VCOM) on one or common electrodes to reduce the dependence of the parasitic capacitance (Cgd) on the voltage of the pixel electrodes by, for example, causing a parasitic capacitance between the gate line and the drain of the second active switching device instead of between the gate line and the drain of the TFT. In this manner, the sensed touch signal may not be distorted by the image data (e.g., pixel electrode voltage). 
     With the foregoing in mind, a general description of suitable electronic devices that may employ electronic touch screen displays having in-cell touch components and are useful in reducing display-to-touch crosstalk (DTX) will be provided below. In particular,  FIG. 1  is a block diagram depicting various components that may be present in an electronic device suitable for use with such a display.  FIGS. 2 and 3  respectively illustrate perspective and front views of suitable electronic device, which may be, as illustrated, a notebook computer or a handheld electronic device. 
     Turning first to  FIG. 1 , an electronic device  10  according to an embodiment of the present disclosure may include, among other things, one or more processor(s)  12 , memory  14 , nonvolatile storage  16 , a display  18  having in-cell touch sensor components  20 , input structures  22 , an input/output (I/O) interface  24 , network interfaces  26 , and a power source  28 . The various functional blocks shown in  FIG. 1  may include hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. It should be noted that  FIG. 1  is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in electronic device  10 . 
     By way of example, the electronic device  10  may represent a block diagram of the notebook computer depicted in  FIG. 2 , the handheld device depicted in  FIG. 3 , or similar devices. It should be noted that the processor(s)  12  and/or other data processing circuitry may be generally referred to herein as “data processing circuitry.” Such data processing circuitry may be embodied wholly or in part as software, firmware, hardware, or any combination thereof. Furthermore, the data processing circuitry may be a single contained processing module or may be incorporated wholly or partially within any of the other elements within the electronic device  10 . 
     In the electronic device  10  of  FIG. 1 , the processor(s)  12  and/or other data processing circuitry may be operably coupled with the memory  14  and the nonvolatile memory  16  to perform various algorithms for responding appropriately to a user touch on the display  18 . Such programs or instructions executed by the processor(s)  12  may be stored in any suitable article of manufacture that includes one or more tangible, computer-readable media at least collectively storing the instructions or routines, such as the memory  14  and the nonvolatile storage  16 . The memory  14  and the nonvolatile storage  16  may include any suitable articles of manufacture for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, and optical discs. Also, programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor(s)  12  to enable the electronic device  10  to provide various functionalities. 
     The display  18  may be a touch screen liquid crystal display (LCD), which may allow users to interact with a user interface of the electronic device  10 . Various touch sensor components, such as touch sense and/or touch drive electrodes may be located within display pixel cells of the display  18 . As mentioned above, in-cell touch sensor  20  components may include integrated display panel components serving a secondary role as touch sensor components. As such, it should be appreciated that the in-cell touch sensor  20  components may be formed from a gate line of the display, a pixel electrode of the display, a common electrode of the display, a source line of the display, or a drain line of the display, or some combination of these elements. In some embodiments, the in-cell touch sensor  20  may be a MultiTouch™ display allowing multiple touches to be detected on the display  18  at once. 
     The input structures  22  of the electronic device  10  may enable a user to interact with the electronic device  10  (e.g., pressing a button to increase or decrease a volume level). The I/O interface  24  may enable electronic device  10  to interface with various other electronic devices, as may the network interfaces  26 . The network interfaces  26  may include, for example, interfaces for a personal area network (PAN), such as a Bluetooth network, for a local area network (LAN), such as an 802.11x Wi-Fi network, and/or for a wide area network (WAN), such as a 3G or 4G cellular network. The power source  28  of the electronic device  10  may be any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
     The electronic device  10  may take the form of a computer or other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, and tablet computers) as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, the electronic device  10  in the form of a computer may be a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. By way of example, the electronic device  10 , taking the form of a notebook computer  30 , is illustrated in  FIG. 2  in accordance with one embodiment of the present disclosure. The depicted computer  30  may include a housing  32 , a display  18 , input structures  22 , and ports of an I/O interface  24 . In one embodiment, the input structures  22  (such as a keyboard and/or touchpad) may be used to interact with the computer  30 , such as to start, control, or operate a GUI or applications running on computer  30 . For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on display  18 . The display  18  may be relatively thin and/or bright, as the in-cell touch sensor  20  may not require an additional capacitive touch panel overlaid on it. 
       FIG. 3  depicts a front view of a handheld device  34 , which represents one embodiment of the electronic device  10 . The handheld device  34  may represent, for example, a portable phone, a media player, a personal data organizer, a handheld game platform, or any combination of such devices. By way of example, the handheld device  34  may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, Calif. In other embodiments, the handheld device  34  may be a tablet-sized embodiment of the electronic device  10 , which may be, for example, a model of an iPad® available from Apple Inc. 
     The handheld device  34  may include an enclosure  36  to protect interior components from physical damage and to shield them from electromagnetic interference. The enclosure  36  may surround the display  18 , which may display indicator icons  38 . The indicator icons  38  may indicate, among other things, a cellular signal strength, Bluetooth connection, and/or battery life. The I/O interfaces  24  may open through the enclosure  36  and may include, for example, a proprietary I/O port from Apple Inc. to connect to external devices. 
     User input structures  40 ,  42 ,  44 , and  46 , in combination with the display  18 , may allow a user to control the handheld device  34 . For example, the input structure  40  may activate or deactivate the handheld device  34 , the input structure  42  may navigate user interface  20  to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  34 , the input structures  44  may provide volume control, and the input structure  46  may toggle between vibrate and ring modes. A microphone  48  may obtain a user&#39;s voice for various voice-related features, and a speaker  50  may enable audio playback and/or certain phone capabilities. A headphone input  52  may provide a connection to external speakers and/or headphones. As mentioned above, the display  18  may be relatively thin and/or bright, as the in-cell touch sensor  20  may not require an additional capacitive touch panel overlaid on it. 
       FIG. 4  generally represents a circuit diagram of certain components of the display  18  in accordance with some embodiments. In particular, the pixel array  100  of the display  18  may include a number of unit pixels  102  disposed in a pixel array or matrix. In such an array, each unit pixel  102  may be defined by the intersection of rows and columns, represented by gate lines  104  (also referred to as scanning lines), and source lines  106  (also referred to as data lines), respectively. Although only 6 unit pixels  102 , referred to individually by the reference numbers  102   a - 102   f , respectively, are shown for purposes of simplicity, it should be understood that in an actual implementation, each source line  106  and gate line  104  may include hundreds or thousands of such unit pixels  102 . Each of the unit pixels  102  may represent one of three subpixels that respectively filters only one color (e.g., red, blue, or green) of light through, for example, a color filter. For purposes of the present disclosure, the terms “pixel,” “subpixel,” and “unit pixel” may be used largely interchangeably. 
     In the presently illustrated embodiment, each unit pixel  102  may include a thin film transistor (TFT)  108  for switching a data signal stored on a respective pixel electrode  110 . The potential stored on the pixel electrode  110  relative to a potential of a common electrode  112 , which may be shared by other pixels  102 , may generate an electrical field sufficient to alter the arrangement of liquid crystal molecules (not illustrated in  FIG. 4 ). In the depicted embodiment of  FIG. 4 , a source  114  of each TFT  108  may be electrically connected to a source line  106  and a gate  116  of each TFT  108  may be electrically connected to a gate line  104 . A drain  118  of each TFT  108  may be electrically connected to a respective pixel electrode  110 . Each TFT  108  may serve as a switching element that may be activated and deactivated (e.g., turned on and turned off) for a predetermined period of time based on the respective presence or absence of a scanning signal on the gate lines  104  that are applied to the gates  116  of the TFTs  108 . 
     When activated, a TFT  108  may store the image signals received via the respective source line  106  as a charge upon its corresponding pixel electrode  110 . As noted above, the image signals stored by the pixel electrode  110  may be used to generate an electrical field between the respective pixel electrode  110  and a common electrode  112 . This electrical field may align the liquid crystal molecules to modulate light transmission through the pixel  102 . 
     The display  18  also may include a source driver integrated circuit (IC)  120 , which may include a chip, such as a processor or application specific integrated circuit (ASIC) that controls the display pixel array  100  by receiving image data  122  from the processor(s)  12 , and sending corresponding image signals to the unit pixels  102  of the pixel array  100 . The source driver  120  may also provide timing signals  126  to the gate driver  124  to facilitate the activation/deactivation of individual rows of pixels  102 . In other embodiments, timing information may be provided to the gate driver  124  in some other manner. The display  18  may or may not include a common voltage (VCOM) source  128  to provide a common voltage (VCOM) voltage to the common electrodes  112 . In certain embodiments, the VCOM source  128  may supply a different VCOM to different common electrodes  112  at different times. In other embodiments, the common electrodes  112  all may be maintained at the same potential or similar potential. 
     As noted above, the in-cell touch sensor  20  of the display  18  may operate using certain in-cell touch sensor components. For example, as illustrated in  FIG. 5 , the in-cell touch sensor  20  may interface with the processors  12  of the electronic device  10  through a touch processor  130 . Specifically, the touch processor  130  may communicate the occurrence and/or position of user touches or hovers the display  18 , to enable the processors  12  to appropriately respond to such user touch or hover events. As further illustrated in  FIG. 5 , the touch processor  130  may be operably coupled to a touch controller  132 , which may control the general operation of a touch pixel array  140 . As will be discussed in further detail below, the touch pixel array may include an N×M of touch pixels  142  (e.g., a 6×10 matrix or other size matrix of touch pixels  142 ). The touch controller  132  may include, for example, touch drive logic  134  and touch sense logic  136 . The touch processor  130  may be integrated into a single application specific integrated circuit (ASIC). The touch drive logic  136  may generate and transmit touch drive signals  148  at various frequencies and/or phases to a touch drive interface  144 , and a touch sense interface  146  may provide various sense signals  150  to the touch sense logic  136  in response. 
     As mentioned above, the touch pixel array  140  may include an M×N matrix of touch pixels  142 . These touch pixels  142  arise due to interactions between touch drive electrodes  152  and touch sense electrodes  154 . It should be noted that the terms “lines” and “electrodes” as sometimes used herein simply refers to conductive pathways, and is not intended to be limited to structures that are strictly linear. Rather, the terms “lines” and “electrodes” may encompass pathways that change direction, of different size, shape, materials, and regions. The touch drive electrodes  152  may be driven by touch drive signals  148  from the touch drive logic  134  of the touch controller  132 . 
     The sense lines  154  may respond differently to the touch drive signals  148  when an object, such as a finger, is located near the confluence of a given touch drive electrode  152  and a given touch sense electrode  154 . The presence of the object may be “seen” by the touch pixel  142  that may result at an intersection of the touch drive electrode  152  and the touch sense electrode  154 . That is, the touch drive electrodes  152  and the touch sense electrodes  154  may form capacitive sensing nodes, or more aptly, the touch pixels  142 . It should be appreciated that the respective touch drive electrodes  152  and touch sense electrodes  154  may be formed, for example, from dedicated touch drive electrodes  152  and/or dedicated touch sense electrodes  154 , and/or may be formed from one or more gate lines  104  of the display  18 , one or more pixel electrode  110   s  of the display  18 , one or more common electrodes  112  of the display  18 , or some combination of these elements. 
     For example, as illustrated in  FIG. 6 , the touch drive electrodes  152  and touch sense electrodes  154  may include column VCOM  156  electrodes and row VCOM  158  electrodes. Specifically, although  FIG. 6  depicts only two column VCOMs  156 A and  156 B and two row VCOMs  158 , an actual implementation of the display  18  may include any suitable number of column VCOMs  156  and row VCOMs  158 . As previously noted, the column VCOMs  156  and row VCOMs  158  may gather touch sense information when operating in what may be referred to herein as a touch mode of operation. Though the column VCOMs  156  and row VCOMs  158  may be supplied the same direct current (DC) bias voltage, for example, in some embodiments, different alternating current (AC) voltages may be supplied and/or received on VCOMs  156  and  158  at substantially different times. For example, as previously noted, the display  18  may be configured to switch between two modes of operation: a display mode of operation and the touch mode of operation. 
     In the display mode, the column VCOMs  156  and the row VCOMs  158  may operate in the aforementioned manner, in which an electric field is generated between the column and row VCOMs  156  and  158  and respective pixel electrodes  110 . The electric field may modulate the liquid crystal molecules to allow a certain amount of light to pass through the pixel. Thus, an image may be displayed on the display  18  in the display mode. On the other hand, in the touch mode, the row VCOM  158  and the column VCOM  156  may be configured to sense a touch on the display  18 . In certain embodiments, a stimulus signal or voltage may be provided by the row VCOM  158 . The column VCOM  156  may receive a touch signal and output the data to be processed, for example, by the touch processor  130  and/or the processor(s)  12 . The touch signal may be generated when a user, for example, touches and/or hover a finger nearby the display  18 , creating capacitive coupling with a portion of the row VCOM  158  and a portion of the column VCOM  156 . Thus, the portion of the column VCOM  156  may receive a signal indicative of the touch and/or hover. 
     Turning now to  FIG. 7 , which illustrates an embodiment of a circuit diagram (e.g., equivalent circuit) of one or more display pixels  102  and touch pixels  142  included within, for example, the touch drive regions (e.g., across the row VCOMs  158 ) and touch sense regions (e.g., along the column VCOMs  158 ) of the display  18 . As depicted, the pixels  102  may include TFTs  108 , as previously discussed above with respect to  FIGS. 4 and 5 . The respective sources  114  of the TFTs  108  may be electrically connected to respective source lines (D x1 ) and (D x2 )  106 , and the gates  116  of the TFTs  108  may be electrically connected to the gate line (G y )  104 . Further, the drains  118  of the TFTs  108  may be electrically connected to respective pixel electrodes  110 . As further illustrated, liquid crystal capacitances (C LC )  160  and/or storage capacitances (C ST )  160  may be present between the respective pixel electrodes  110  and the common electrodes  112 . 
     During the display mode of operation, data signals may be supplied to the source lines (D x1 ) and (D x2 )  106  and by extension, to the respective sources  114  of the TFTs  108 . Similarly, an activation signal may be supplied to the gate line (G y )  104  to activate the gates  116  of the TFTs  108 . With the TFTs  108  activated, the data signals supplied to the respective sources  114  flow through the TFTs  108  to the respective drains  118 . Thus, the data signal may be supplied to the pixel electrodes  110 . Specifically, to store the data signals onto the pixel electrodes  110 , the activation signal may be removed from the gate line (G y )  104  while the data signals are still being supplied to the source lines (D x1 ) and (D x2 )  106 . However, when the activation signal is removed, a portion of the voltage stored by the pixel electrodes  110  may, in some embodiments, contribute to a parasitic capacitance (C gd ) (not illustrated) that may be formed between the gates  116  and the drains  118 . In one embodiment, the parasitic capacitance (C gd ) may be a function (e.g., non-linear function) of the voltage levels (e.g., white and black color levels) of the data signals being supplied to the source lines (D x1 ) and (D x2 )  106 . In the touch mode of operation, if the parasitic capacitance (C gd ) is left to persist, crosstalk (e.g., display image-dependent and/or data signal-dependent interference) may be introduced between, for example, the display pixels  102  and the touch pixels  142  illustrated in FIG. 5 . That is, a parasitic capacitance (C gd ) may be formed, for example, in one or more coupling paths of the drive signals  148  and/or the sense signals  150 , and may thus adversely impact or distort the drive signals  148  and/or the sense signals  150  (e.g., create an image of a phantom touch or otherwise an undetectable image of a touch). 
     In certain embodiments, one or more active switches  162  may be included between each of the column VCOMs  156  and the row VCOMs  158  and respective common electrodes  112 . Indeed, the one or more active switches  162  may be provided to reduce the dependence of parasitic capacitance (C gd ) on the voltage of the pixel electrodes  110 , such that any distortion (e.g., image data related) to the drive signals  148  and/or the sense signals  150  may be substantially reduced. The active switches  162  may include any active switching devices (e.g., one or more specific transistors, or other solid-state switching devices) useful in controlling the common voltage signal (VCOM) delivered to the common electrode  112 , and by extension, the charge on the common electrodes  112 . For example, during the display mode, an activation signal may be supplied to the gate line (G y )  104  to activate a gate  164  of the active switch  162  (e.g., switch to an “ON” state), thus allowing the VCOM signals to pass from drains  166  of the active switches  162  to respective sources  168  coupled to the common electrodes  112 . As it should be appreciated, during the display mode, the TFTs  108  may be activated at substantially the same time to allow image data to be stored on the pixel electrodes  110 . 
     On the other hand, as further illustrated in  FIG. 7 , during the touch mode, the activation signal may be removed from the active switches  162  (e.g., switch to an “OFF” state), causing, for example, a high impedance or floating charge on the common electrodes  112 . During this period of time, touch drive signals  148  generated, for example, by a touch drive amplifier  169  may emanate from the VCOM  156  and generate a touch signal capacitance (C SIG )  172 . The touch signal capacitance (C SIG )  172  may be indicative a user touch or hover. The touch signal capacitance (C SIG )  172 , or a change thereof (e.g., the indication of the touch or hover), may be then sensed by the VCOM  158  and amplified by a touch sense amplifier  170 . 
     Furthermore, in certain embodiments, a portion of the touch drive signal  148  emanating from the VCOM  156  may charge the parasitic capacitance (C gd )  174  formed between the respective drains  166  of the active switches  162 , creating, for example, a secondary touch signal path to the touch sense amplifier  170 . Similarly, a touch signal  150  sensed by the VCOM  158  may pass through a corresponding parasitic capacitance (C gd )  174  being amplified by the touch sense amplifier  170 . In this way, the dependence of the parasitic capacitance (C gd )  174  on, for example, the voltage of the pixel electrodes  110  may be substantially reduced. Instead, the parasitic capacitance (C gd )  174  may be charged by the voltage of the touch drive signals  148  emanating from the VCOM  156 . Thus, whether the touch drive signals  148  are detected as a change in signal capacitance (C SIG )  172 , or the touch drive signals  148  alternatively travels a conductive path through the parasitic capacitances (C gd )  174 , the touch drive signals  148  and/or the touch sense signals  150  may be substantially unmitigated by the voltage of the pixel electrodes  110  (e.g., the voltage between the drains  118  of the respective TFTs  108  and the gate line (G y )  104 ). 
     Turning now to  FIGS. 8, 9, and 10 , flow diagrams are presented, illustrating embodiments of a process  180  (e.g., display mode process  182  and touch mode process  184 ) useful in reducing display-to-touch crosstalk (DTX) by using, for example, the one or more processor(s)  12  included within the system  10  depicted in  FIG. 1 . For the purpose of illustration, henceforth,  FIG. 8  may be discussed in conjunction with  FIGS. 9 and 10 . The process  180  may include code or instructions stored in a non-transitory machine-readable medium (e.g., the memory  14 ) and executed, for example, by the one or more processor(s)  12  included within the system  10 . As previously noted, the system  10  may operate in each of a display mode operation (block  182 ) and a touch mode of operation (block  184 ). In the display mode, operation may begin with supplying (block  186 ) an activation signal to the display pixels  102  (e.g., via the gate line  104 ). Operation in the display mode  182  may continue with supplying (block  188 ) an activation signal to the active switches  162  (e.g., via the gate line  104 ). For example, as noted above with respect to  FIG. 7 , the active switches  162  may be included between each of the column VCOMs  156  and the row VCOMs  158  and respective common electrodes  112 , and may be useful in controlling the common voltage signal (VCOM) delivered to the common electrode  112 , and by extension, the charge on the common electrodes  112  of the display pixels  102 . 
     Operation in the display mode  182  may then continue with supplying (block  190 ) a data signal to the pixel electrodes  110  of the display pixels  102  (e.g., via the drains  118  of the pixels  102 ) to store image data onto the pixel electrodes  110 . Operation in the display mode  182  may then conclude with removing (block  192 ) the activation signals from the display pixels. In a similar manner,  FIG. 10  illustrates the touch mode  184 . It should be appreciated that the display mode  182  and the touch mode  184  may be operable substantially concurrently with respect to each other, substantially sequentially with respect to each other, substantially interdependently, or otherwise operable in some combination thereof. Considering the foregoing, operation in the touch mode  184  may begin with deactivating (block  196 ) the active switches  162 . Specifically, the active switches  162  controlling the common voltage signal (VCOM) delivered to the common electrodes  112  may be deactivated to reduce the possibility of crosstalk between, for example, the display pixels  102  and touch pixels  140 . 
     Operation in the touch mode  184  may continue with supplying (block  198 ) touch drive signals (e.g., stimulation signals) to the touch pixels  140 . As noted above with respect to  FIG. 7 , a portion of the touch drive signals emanating from, for example, the VCOM  156  may charge a parasitic capacitance (C gd )  174  formed between the respective drains  166  of the active switches  162  and the gate line (G y )  104  during the period of time the active switches  162  is switched to the “OFF” state. Operation in the touch mode  184  may then continue with receiving (block  200 ) touch sense signals from the touch pixels  140 . Operation in the touch mode  184  may then conclude with determining (block  202 ) one or more touch and/or hover events without an occurrence of a parasitic capacitance (C gd ) due to the voltage level of the display pixel electrodes  110 . In other words, dependence of the parasitic capacitance (C gd )  174  on, for example, the voltage of the pixel electrodes  110  may be reduced, and by extension, the possibility of crosstalk between the display pixels  102  and touch pixels  140  may be reduced. 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Metadata:
Filing Date: 20130924
Publication Date: 20170418
Grant Date: 20170418
Priority Date: 20130924
Inventors: STRONKS DAVID A.
AL-DAHLE AHMAD
YAO WEI H.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3655", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/13606", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0209", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0847", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13624", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13606", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13606", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13624", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13624", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0847", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0209", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0209", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3655", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 52690537