The present disclosure relates generally to electronic displays, and more particularly, to adjusting VCOM driving for a display based on content.
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.
Generally, an electronic display may enable information to be communicated to a user by displaying visual representations of the information, for example, as pictures, text, or videos. More specifically, the visual representations may be displayed as successive static image frames. In some embodiments, each image frame may be displayed by successively writing image data to rows of pixels in the electronic display.
In addition to outputting information, the electronic display includes a VCOM that connects to pixel capacitor of unit pixels in the electronic display to connect the pixel capacitors to a common voltage. When pixels change, current may be injected into a dataline for a unit pixel. Resulting in a voltage variation in the VCOM due to dataline and VCOM coupling. The display during this voltage variation may result in display artifacts and/or improper final pixel voltages due to writing during VCOM voltage settling. In scenarios where the display has a relatively high refresh rate (e.g., 120 or 240 Hz), the period for the VCOM to settle is reduced. Furthermore, in scenarios where high voltage slewing is applied to the VCOM and/or the dataline may increase VCOM settling times. Moreover, VCOM settling time increases may increase when column or row drivers switch in the same direction simultaneously. Thus, it may be desirable to compensate for the charge.
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.
The present disclosure generally relates to improving display appearance by reducing or eliminating artifacts resulting from coupling a VCOM to one or more datalines. Typically, when uncompensated VCOMs are coupled to one or more datalines through pixel circuitry, the VCOM is injected with some charge from the one or more connected datalines. Such injection of charge to the VCOM may result in display artifacts (e.g., greenish hue) while the VCOM is settling to a voltage level appropriate for the pixel content to be displayed.
Such VCOM variations may be pre-determined before coupling the VCOM to the one or more datalines. The VCOM may then be injected with charge to offset the calculated variations that would result from the coupling. Accordingly, the VCOM variation may be reduced or eliminated by setting the VCOM to the compensation level before (or during) the connection of the VCOM to the one or more datalines.
In some embodiments, the compensated VCOM may be calculated using a next line buffer that includes pixel content for one or more pixels to be displayed next while another line buffer is used to write pixel content to the one or more pixels currently displayed. Accordingly, the pre-compensation includes determining and compensating for future VCOM variations before the variations occur.
Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:
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' 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 may 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 discussed, the present disclosure generally relates to reducing or eliminating artifacts resulting from coupling a VCOM to one or more datalines. Typically, when uncompensated VCOMs are coupled to one or more datalines through pixel circuitry, the VCOM is injected with some charge from the one or more connected datalines. Such injection of charge to the VCOM may result in display artifacts (e.g., greenish hue) while the VCOM is settling to a voltage level appropriate for the pixel content to be displayed.
Such VCOM variations may be pre-determined before coupling the VCOM to the one or more datalines. The VCOM may then be injected with charge to offset the calculated variations that would result from the coupling. Accordingly, the VCOM variation may be reduced or eliminated by setting the VCOM to the compensation level before (or during) the connection of the VCOM to the one or more datalines.
In some embodiments, the compensated VCOM may be calculated using a next line buffer that includes pixel content for one or more pixels to be displayed next while another line buffer is used to write pixel content to the one or more pixels currently displayed. Accordingly, the pre-compensation includes determining and compensating for future VCOM variations before the variations occur. Furthermore, in some embodiments, the refresh rate may vary by content or even within content. For example, some content (e.g., movies) may have a set refresh rate (e.g., 24 Hz) while other content (e.g., specific application programs) may have dynamically determined refresh rates or may specify a specific refresh rate. This refresh rate information may be used in determine when and/or how often to compensate for expected VCOM fluctuations due to coupling the VCOM to a data line.
To help illustrate, a electronic device 10 that varies VCOM driving based on content is described in
Accordingly, as depicted, the electronic device 10 includes the display 12, input structures 14, input/output (I/O) ports 16, one or more processor(s) 18, memory 20, nonvolatile storage 22, a network interface 24, and a power source 26. The various components described in
As depicted, the processor 18 is operably coupled with memory 20 and/or nonvolatile storage device 22. More specifically, the processor 18 may execute instructions stored in memory 20 and/or non-volatile storage device 22 to perform operations in the electronic device 10, such as outputting image data to the display 12. As such, the processor 18 may include one or more general purpose microprocessors, one or more application specific processors (ASICs), one or more field programmable logic arrays (FPGAs), or any combination thereof. Additionally, memory 20 and/or non volatile storage device 22 may be a tangible, non-transitory, computer-readable medium that stores instructions executable by and data to be processed by the processor 18. In other words, the memory 20 may include random access memory (RAM) and the non-volatile storage device 22 may include read only memory (ROM), rewritable flash memory, hard drives, optical discs, and the like. By way of example, a computer program product containing the instructions may include an operating system or an application program.
Additionally, as depicted, the processor 18 is operably coupled with the network interface 24 to communicatively couple the electronic device 10 to a network. For example, the network interface 24 may connect the electronic device 10 to a personal area network (PAN), such as a Bluetooth network, a local area network (LAN), such as an 802.11 Wi-Fi network, and/or a wide area network (WAN), such as a 4G or LTE cellular network. Furthermore, as depicted, the processor 18 is operably coupled to the power source 26, which provides power to the various components in the electronic device 10. As such, the power source 26 may include any suitable source of energy, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter.
As depicted, the processor 18 is also operably coupled with I/O ports 16, which may enable the electronic device 10 to interface with various other electronic devices, and input structures 14, which may enable user interaction with the electronic device 10. Accordingly, the inputs structures 14 may include buttons, keyboards, mice, trackpads, and the like. In addition to the input structures 14, in some embodiments, the display 12 may include touch sensing components to enable user inputs via user touches to the surface of the display 12. In fact, in some embodiments, the electronic display 12 may detect multiple user touches at once.
In addition to enabling user inputs, the display 12 may display visual representations via one or more static image frames. In some embodiments, the visual representations may be a graphical user interface (GUI) for an operating system, an application interface, text, a still image, or a video. As depicted, the display 12 is operably coupled to the processor 18, which may enable the processor 18 (e.g., image source) to output image data to the display 12.
Based on the received image data, the display 12 may then write image frames to the display pixels in the display 12 to display a visual representation. As will be described in more detail below, a VCOM of the display 12 may be adjusted to compensate for VCOM variations that occur from coupling the VCOM to one or more datalines of the display.
As described above, the electronic device 10 may be any suitable electronic device. To help illustrate, one example of a handheld device 10A is described in
As depicted, the handheld device 10A includes an enclosure 28, which may protect interior components from physical damage and to shield them from electromagnetic interference. The enclosure 28 may surround the display 12, which, in the depicted embodiment, displays a graphical user interface (GUI) 30 having an array of icons 32. By way of example, when an icon 32 is selected either by an input structure 14 or a touch sensing component of the display, an application program may launch.
Additionally, as depicted, input structure 14 may open through the enclosure 28. As described above, the input structures 14 may enable a user to interact with the handheld device 10A. For example, the input structures 14 may activate or deactivate the handheld device 10A, navigate a user interface to a home screen, navigate a user interface to a user-configurable application screen, activate a voice-recognition feature, provide volume control, and toggle between vibrate and ring modes. Furthermore, as depicted, the I/O ports 16 open through the enclosure 28. In some embodiments, the I/O ports 16 may include, for example, an audio jack to connect to external devices.
To further illustrate a suitable electronic device 10, a tablet device 10B is described in
As described above, the display 12 may facilitate communication of information between the electronic device 10 and a user, for example, by displaying visual representations based on image data received from the processor 18 and detecting user touch on the surface of the display 12. To help illustrate, a portion 34 of the electronic device 10 is described in
To facilitate such operations, the display 12 may include display components (e.g., display driver circuitry) 38 and touch sensing components (e.g., touch sensing circuitry) 40. More specifically, the display components 38 may include any suitable components used to display an image frame on the display 12. For example, when the display 12 is a liquid crystal display, the display components 38 may include a thin film transistor (TFT) layer and a liquid crystal layer organized as display pixels. To help illustrate, operation of display components 38 used in a liquid crystal display are described in
In the depicted embodiment, the display components 38 include a number of display pixels 42 disposed in a pixel array or matrix. More specifically, each display pixel 42 may be defined at the intersection of a gate line 44 (e.g. scanning line) and a source lines 46 (e.g., data line). Although only six display pixels 42, referred to individually by the reference numbers 42A-42F, are shown for purposes of simplicity, it should be understood that in an actual implementation, each source line 46 and gate line 44 may include hundreds or thousands of such display pixels 42.
As described above, image data may be written to each of the display pixels 42 to display an image frame. More specifically, image data may be written to a display pixel 42 by using a thin film transistor 48 to selectively store an electrical potential (e.g., voltage) on a respective pixel electrode 50. Accordingly, in the depicted embodiment, each thin film transistor 48 includes a source, which is electrically connected to a source line 46, a drain 56, which is electrically connected to a pixel electrode 50, and a gate 58, which is electrically connected to a gate line 54.
Thus, to write image data to a row of display pixels 42 (e.g., 42A-42C), the corresponding TFT gates 48 may be activated (e.g., turned on) by a scanning signal on the gate line 44. Image data may then be written to the row of display pixels by storing (e.g., via a capacitor) an electrical potential corresponding with the grayscale value of the image data from the source lines 46 to the pixel electrode 50. The potential stored on the pixel electrode 50 relative to a potential of a common electrode 52 may then generate an electrical field sufficient to alter the arrangement of the liquid crystal layer (not shown). More specifically, this electrical field may align the liquid crystal molecules within the liquid crystal layer to modulate light transmission through the display pixel 42. In other words, as the electrical field changes, the amount of light passing through the display pixel 42 may increase or decrease. As such, the perceived brightness level of the display pixel 42 may be varied by adjusting the grayscale value of the image data. In this manner, an image frame may be displayed by successively writing image data the rows of display pixels 42.
To facilitate writing image data to the display pixels 42, the display components 38 may also include a source driver 60, a gate driver 62, and a common voltage (Vcom) source 64. More specifically, the source driver 60 may output the image data (e.g., as an electrical potential) on the source lines 46 to control electrical potential stored in the pixel electrodes 50. Additionally, the gate driver 62 may output a gate signal (e.g., as an electrical potential) on the gate lines 44 to control activation of rows of the display pixels 42. Furthermore, the Vcom source 64 may provide a common voltage to the common electrodes 52.
Similarly, in embodiments with touch sensing, the touch sensing components 40 may include any suitable components used to detect occurrence and/or presence of a user touch on the surface of the display 12. For example, as illustrated in
As described above, in some embodiments, occurrence and/or position of a user touch may be detected based on impedance changes caused by the user touch. To facilitate detecting impedance changes, the touch sensing components 40 may include touch drive logic 72 and touch sense logic 74. More specifically, the touch drive logic 72 may output touch drive signals at various frequencies and/or phases on the touch drive lines 68. When an object, such as a user finger, contacts the surface of the display 12, the touch sense lines 70 may respond differently to the touch drive signals, for example by changing impendence (e.g., capacitance). More specifically, the touch sense lines 70 may generate touch sense signals to enable the touch sense logic 74 to determine occurrence and/or position of the object on the surface of the display 12.
In some embodiments, the touch sensing components 40 may utilize dedicated touch drive lines 68, dedicated touch sense lines 70, or both. Additionally or alternatively, the touch drive lines 68 and/or the touch sense lines 70 may utilize one or more of the display components 38. For example, the touch drive lines 68 and/or the touch sense lines 70 may be formed from one or more gate lines 44, one or more pixel electrodes 50, one or more common electrodes 52, one or more source lines 46, or any combination thereof.
To facilitate controlling operation of both the display components 38 and/or the touch sensing components 40, the display 12 may include a timing controller (TCON) 76 as depicted in
Moreover, in embodiments with touch sensing, the timing controller 76 may instruct the display components 38 to write image data to the display pixels 42 and instruct the touch sensing components 40 to check for a user touch. As described above, the frequency the touch sensing components 40 detects whether a user touch is present may be increased to improve the user touch detection accuracy. In fact, the timing controller 76 may utilize intra-frame pauses by alternating between instructing the display components 38 to write a portion of an image frame and instructing the touch sensing components 40 to check for a user touch.
As previously discussed, when a VCOM is paired to a dataline when pixel content is being written to a pixel, the VCOM voltage may fluctuate and result in an artifact on the display screen. For example, in some scenarios, if the VCOM charge fluctuation exceeds a certain value (e.g., 10 mV), the pixel may appear greenish.
While displaying the pixel content of the line buffer, the processor 18 calculates a change of charge in the dataline between the pixel contents and resultant change in the VCOM from the change in dataline change (block 108). For example, a processor 18 may calculate a voltage charge dumped into a dataline during a dataline transition using the following equation:
Q=CΣV_changedata_i*Polaritydata_i (Equation 1)
, where C is dataline capacitance to the VCOM, V_change is the pixel voltage change from the current line to the next line, and polarity (−1 or 1) indicates a voltage swing direction for the pixels. In some embodiments, the capacitance may be determined using empirical determinations, calculations, and/or other suitable means for determining or estimating capacitance between the dataline and the VCOM. Using this value, the processor 18 determines a compensated VCOM voltage level to compensate for VCOM variation due to coupling with the dataline (block 110). By calculating this charge, a VCOM driver can use a compensated VCOM to compensate for VCOM fluctuations caused by the VCOM and dataline coupling based at least in part on the polarity of the current data signal. The electronic device 10 then places at least some of the pixels corresponding to the linebuffers in a non-writeable state (block 112).
After the pixels are not in the writeable mode, the processor 18 causes the VCOM driver to adjust the VCOM to the compensation level (block 114). The processor 18 then writes a new next line and uses the previous next line as the current line and continues to compensate for charge fluctuations in the VCOM due to dataline coupling to the VCOM. Moreover, the compensated VCOM is used when writing the display for the original next line (and now current line) since the VCOM voltage level has been set to the compensated level for the next line to be written. Then, the electronic device 10 continues displaying future pixels using compensated VCOM values.
Furthermore, the illustrated compensation circuit 120 may be used to compensate for VCOM variations since, in some embodiments, a large bias would be used rarely if at all. For small disturbances to the VCOM plane 124 may be compensated easily with a relatively small bias current, and smaller bias currents consume less power. Moreover, even large bias voltages are pre-compensated. Thus, large changes may be made the VCOM plane 124 without causing substantial changes to an appearance of a display if any changes are made. Furthermore, the pre-compensated VCOM values may be set since these compensations would not result in a panelized regular image pattern.
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.
This application is a continuation of U.S. application Ser. No. 14/640,931, filed on Mar. 6, 2015, the contents of which are herein expressly incorporated by reference for all purposes.
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Number | Date | Country | |
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Parent | 14640931 | Mar 2015 | US |
Child | 15701001 | US |