Abstract:
Methods and devices employing mura prevention circuitry, are provided. In one example, a method may include supplying a first voltage pathway between a common electrode driver and a common electrode of an electronic display device and supplying a second voltage pathway between the common electrode driver and ground. Mura prevention circuitry may be supplied that activates the first voltage pathway when the electronic display device is turned on and an activation gate signal is provided from a gate corresponding to the common electrode driver. Further, the mura prevention circuitry may activate the second voltage pathway when the electronic display device is turned off or no activation gate signal is provided from the gate corresponding to the common electrode driver.

Description:
The present application is a Non-Provisional of U.S. Provisional Patent Application No. 61/657,696, entitled “Devices and Methods for Common Electrode Mura Prevention,” filed Jun. 8, 2012, which is herein incorporated by reference. 
     BACKGROUND 
     The present disclosure relates generally to electronic displays (e.g., a liquid crystal display (LCD) or organic light-emitting diode (OLED) display) and, more particularly, to electronic displays that can be turned off in a manner that reduces non-uniformity in a display output when the display is subsequently turned back on. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, 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 displays, such as liquid crystal displays (LCDs), are commonly used in electronic devices such as televisions, computers, and phones. LCDs portray images by modulating the amount of light that passes through a liquid crystal layer within pixels of varying color. For example, by varying a voltage difference between a pixel electrode and a common electrode in a pixel, an electric field may result. The electric field may cause the liquid crystal layer to vary its alignment, which may ultimately result in more or less light being emitted through the pixel where it may be seen. By changing the voltage difference (often referred to as a data signal) supplied to each pixel, images may be produced on the LCD. 
     To store data representing a particular amount of light that is to be passed through pixels, gates of thin-film transistors (TFTs) in the pixels may be activated while the data signal is supplied to the pixels. Conventionally, when an LCD is turned off, the pixel electrodes of all pixels of the LCD may be supplied a minimal voltage. However, when triboelectric charging occurs, such as by friction, (e.g., friction caused by inserting or removing a cable from a cable connector) electro-static discharge (ESD) may enter the display. As the ESD enters the display, a charge may be left in the display, causing retained charges to the common electrodes of the display. It is believed that these retained charges, caused by the incorporation of ESD in the display, may result in mura or image artifacts, such as undesirable checkerboard patterns that could appear after the display is turned on again. 
     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 turning off an electronic display to prevent electro-static discharge (ESD) from causing image artifacts when the display is subsequently turned back on. By way of example, a method for turning off an electronic display may include short-circuiting any electrical charge in each common electrode of an electronic display as the panel is turned off. 
     Various refinements of the features noted above may be made 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 display having mura prevention circuitry, 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 handheld device representing another embodiment of the electronic device of  FIG. 1 ; 
         FIG. 4  is a schematic diagram illustrating a connection between a display and flex circuitry that utilizes mura prevention circuitry, in accordance with an embodiment; and 
         FIG. 5  is a circuit diagram of mura prevention circuitry, 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 mentioned above, embodiments of the present disclosure relate to electronic display devices and electronic devices incorporating electronic display devices that employ a display shut-down device, method, or combination thereof. Specifically, rather than turning off an electronic display in a conventional manner, which could result in a retained common voltage charged on the pixels of the electronic display, which could in turn cause image artifacts when the display is turned back on, embodiments of the present disclosure may incorporate mura prevention circuitry. When the electronic display device is turned off, this mura prevention circuitry may result in a significantly reduced amount of residual charge remaining on the common electrodes of the electronic display. In fact, the amount of residual charge remaining on the common electrodes may be so low as to substantially reduce the effect of any image artifacts that might otherwise form. 
     Specifically, when an electronic display device is turned off, to decrease the amount of residual charge remaining on the common electrodes, each of the common electrodes of the electronic display device may be short-circuited to ground by activating depletion mode MOSFETs along each of the common electrode driver lines. The activation of these depletion mode MOSFETs creates a low resistance path that can enable distribution of any retained charge across all of the display device&#39;s common electrodes, creating uniformity in charges across all of the common electrodes. 
     With the foregoing in mind, a general description of suitable electronic devices that may employ electronic displays having mura prevention capabilities 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 a 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  with associated mura prevention circuitry  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 the 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.” This 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 . As presented herein, the data processing circuitry may control the electronic display  18  by determining when the electronic display  18  is to be turned off and by issuing a turn-off or shutdown command. The turn-off or shutdown command is provided to the display  18 , which uses the mura prevention circuitry  20  to turn off the display  18  in a way that reduces the occurrence of image artifacts when the display  18  is later turned back on. 
     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 execute instructions. 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 . 
     The display  18  may be a touch-screen liquid crystal display (LCD) or organic light-emitting diode (OLED) display, for example, which may enable users to interact with a user interface of the electronic device  10 . In some embodiments, the electronic display  18  may be a MultiTouch™ display that can detect multiple touches at once. Various display components, such as turn-off logic and associated switching devices may be located within the electronic display  18 . As will be described further below, the mura prevention circuitry  20  may include circuitry for creating a low resistance path from the common electrode drivers of the display  18  to ground when the display  18  is turned off. This low resistance path to ground may enable any retained charges found in the common electrodes to dissipate, resulting in more uniform display  18  outputs when the display  18  is turned back on. 
     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 the display  18 . Further, the display  18  may include the zero-bias display turn-off circuitry  20 . 
       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 a user interface 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  of the handheld device  34  may make use of the mura prevention circuitry  20 .  FIG. 4  illustrates a connector  60  that electrically couples and conntects a display  18  with flex circuitry  62 . In certain embodiments, the flex circuitry  62  may be a main logic board (e.g., main logic board  100  of  FIG. 5 ) or may be coupling circuitry that couples a main logic board to a display  18 . For example, the flex circuitry  62  may provide voltages through the connector  60  to one or more common electrodes (e.g., the 20×10 common electrode matrix  64  depicted in  FIG. 4 ) of the display  18 . As previously mentioned, whenever a flex circuit  62  is connected to or disconnected from the display  18  (e.g., via the connector  60 ), electro-static discharge may enter the display  18 . This electro-static discharge may result in stored charges among the common electrodes. These stored charges may induce patterns or other uniformities in the display  18  outputs. 
     As discussed above, the display  18  may make use of mura prevention circuitry  20 . As illustrated by the dashed boxes, the mura prevention circuitry  20  may reside in, for example, the flex circuitry  62 , the connector  60 , or the display  18 . As will be discussed in more detail with regards to  FIG. 5 , the mura prevention circuitry  20  may enable more uniform display  18  outputs by distributing and/or depleting any charges that may be stored in the common electrodes  64  of the display  18 . 
     Turning now to a more detailed discussion of the mura prevention circuitry,  FIG. 5  illustrates a circuit diagram of the mura prevention circuitry  20  electrically coupled to the display  18 , in accordance with an embodiment. As discussed above, the mura prevention circuitry  20  may be found in any one of a multitude of areas of circuitry. For example, the mura prevention circuitry  20  may be found in either the display  18 , the connector  60 , or the flex circuitry  62 . As illustrated, a main logic board (MLB)  100  may provide one or more common electrode (VCOM) drivers  102 . When electrically coupled with the display  18 , the VCOM drivers  102  may provide voltage signals to one or more (e.g., an array) of VCOMs  64  of the display  18 . In certain embodiments, the MLB  100  or coupling circuitry may be a flex circuit that enables the MLB  100  to flex due to mounting of the MLB  100  circuitry on a flexible substrate. The MLB  100  may electrically couple with the display  18  via a connector, such as a board-to-board (B2B) connector  60 . 
     The mura prevention circuitry  20  may include metal-oxide-semicondutor field-effect transistors (MOSFETs), such as n-channel depletion mode MOSFETs  108 . The MOSFETs  108  may provide an electrical connection between the coupled VCOM drivers  102  and ground  110 . A gate signal  112  may determine whether signals from the VCOM drivers  102  will reach the ground  110  or the VCOMs  103  of the display  18 . Generally speaking, depletion mode MOSFETs  108  are normally closed, allowing voltage to pass through the MOSFETs  108 , until a gate activation signal (e.g., gate signal  112 ) is provided to the n-channel depletion mode MOSFETs  108 . Thus, when no signal is provided via the gate signal  112  (e.g., when an electronic display device  18  is turned off), the VCOM driver  102  signals will flow to the ground  110 . However, when a gate signal  112  is applied to the n-channel depletion mode MOSFETs  108  (e.g., when the electronic display device  18  is turned on and a gate activation signal  112  is present), the VCOM driver  102  signals will flow to the VCOMs  64  of the display  18 . Accordingly, when the display  18  is turned off or no gate activation signal  112  is provided, any charge retained by the VCOMs  64  may flow to ground  110 , thus reducing any image artifacts that may be caused by such retained charges in the VCOMs  64 . Accordingly, any induced charges due to electro-static discharge occurring while the display  18  is off will also be dissipated since in the MOSFETs  108  may always be closed while the display is off. 
     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.