Patent Application
20120081347
The present disclosure relates generally to control of a display in a device.
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.
Liquid crystal displays (LCDs) are commonly used as screens or displays for a wide variety of electronic devices, including such consumer electronics as televisions, computers, and handheld devices (e.g., cellular telephones, audio and video players, gaming systems, and so forth). Such LCD devices typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such LCD devices typically use less power than comparable display technologies, making them suitable for use in battery-powered devices or in other contexts where it is desirable to minimize power usage.
LCDs typically include an LCD panel having, among other things, a liquid crystal layer and various circuitry for controlling orientation of liquid crystals within the layer to modulate an amount of light passing through the LCD panel and thereby render images on the panel. If a voltage of a single polarity is consistently applied to the liquid crystal layer, a biasing (polarization) of the liquid crystal layer may occurs such that the light transmission characteristics of the liquid crystal layer may be disadvantageously altered.
To aid in preventing this biasing of the liquid crystal layer, periodic inversion of the electric field applied to the liquid crystal layer may be utilized. Furthermore, various inversion techniques may be utilized to reduce visual artifacts caused by slight differences in the value of applied positive and negative voltages during the periodic inversion of the electric field applied to the liquid crystal layer. For example, a dot inversion method may cause each adjacent pixel location in the liquid crystal layer to be driven with a voltage opposite of its neighboring pixels over a given time frame. This technique may greatly reduce the generation of visual artifacts on the LCD, however, it may require a substantial amount of power to perform. Accordingly, there is a need for low power inversion techniques that minimize the generation of visual artifacts on an LCD.
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.
A method and system for driving a matrix of pixels in a display with alternating positive and negative voltages. Column drivers of a display may drive a first voltage, for example, a positive voltage, to selected rows along columns of a pixel array (matrix) in a display during a first period of time in a frame (i.e., the first half of the time required to update data for the entire matrix of pixels). The column driver may subsequently drive an inverse voltage of the first voltage to the remaining rows along the columns of the pixel array during a second period of time in the frame. That is, row drivers may alternately activate, for example, even then odd rows (or, alternatively, odd then even rows) during the first and seconds periods. In this manner, for example, odd rows driven by the first voltages may be scanned during a first period of time in a frame, while even rows driven by the inverse of the first voltage may be scanned during a second period of time in the frame. Additionally, since rows are scanned in two steps alternatively, image data may be pre-arranged before being scanned into display. That is, each of the odd and even rows of data may be grouped such that as the even rows scanned to the display followed by the odd rows, or vice versa.
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 will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are 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 would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
Certain embodiments of the present disclosure are generally directed to reducing power consumption by an electronic display, such as an LCD, through driving a matrix of pixels in a display with alternating positive and negative voltages to aid in prevent biasing of the pixels in the display. For example, column drivers of a display may drive a first voltage, for example, a positive voltage, to selected rows of a pixel array in the display during a first period of time in a frame (i.e., the time required to update data for the entire matrix of pixels) and subsequently may drive an second (inverse) voltage of the first voltage to the remaining rows of the pixel array during a second period of time in the frame. That is, row drivers may alternately activate, for example, even and odd rows during the first and seconds periods in conjunction with the first and second voltages. In this manner, for example, odd rows driven by the first voltages may be scanned during a first period of time in a frame, while even rows driven by the inverse of the first voltage may be scanned during a second period of time in the frame. Alternatively, for example, even rows driven by the first voltages may be scanned during a first period of time in a frame, while odd rows driven by the inverse of the first voltage may be scanned during a second period of time in the frame. Additionally, data for display on the display may be arranged such that the data is transmitted to activated rows of pixels of the matrix in conjunction with the alternate activation of the rows discussed above. With these foregoing features in mind, a general description of electronic devices including a display that may use the presently disclosed technique is provided below.
As may be appreciated, electronic devices may include various internal and/or external components which contribute to the function of the device. For instance,
The display 12 may be used to display various images generated by the electronic device 10. The display 12 may be any suitable display, such as a liquid crystal display (LCD) or an organic light-emitting diode (OLED) display. Additionally, in certain embodiments of the electronic device 10, the display 12 may be provided in conjunction with a touch-sensitive element, such as a touchscreen, that may be used as part of the control interface for the device 10.
The I/O ports 14 may include ports configured to connect to a variety of external devices, such as a power source, headset or headphones, or other electronic devices (such as handheld devices and/or computers, printers, projectors, external displays, modems, docking stations, and so forth). The I/O ports 14 may support any interface type, such as a universal serial bus (USB) port, a video port, a serial connection port, an IEEE-1394 port, an Ethernet or modem port, and/or an AC/DC power connection port.
The input structures 16 may include the various devices, circuitry, and pathways by which user input or feedback is provided to processor(s) 18. Such input structures 16 may be configured to control a function of an electronic device 10, applications running on the device 10, and/or any interfaces or devices connected to or used by device 10. For example, input structures 16 may allow a user to navigate a displayed user interface or application interface. Non-limiting examples of input structures 16 include buttons, sliders, switches, control pads, keys, knobs, scroll wheels, keyboards, mice, touchpads, and so forth. Additionally, in certain embodiments, one or more input structures 16 may be provided together with display 12, such an in the case of a touchscreen, in which a touch sensitive mechanism is provided in conjunction with display 12.
Processors 18 may provide the processing capability to execute the operating system, programs, user and application interfaces, and any other functions of the electronic device 10. The processors 18 may include one or more microprocessors, such as one or more “general-purpose” microprocessors, one or more special-purpose microprocessors or ASICS, or some combination of such processing components. For example, the processors 18 may include one or more reduced instruction set (RISC) processors, as well as graphics processors, video processors, audio processors, and the like. As will be appreciated, the processors 18 may be communicatively coupled to one or more data buses or chipsets for transferring data and instructions between various components of the electronic device 10.
Programs or instructions executed by processor(s) 18 may be stored in any suitable manufacture that includes one or more tangible, computer-readable media at least collectively storing the executed instructions or routines, such as, but not limited to, the memory devices and storage devices described below. Also, these programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processors 18 to enable device 10 to provide various functionalities, including those described herein.
The instructions or data to be processed by the one or more processors 18 may be stored in a computer-readable medium, such as a memory 20. The memory 20 may include a volatile memory, such as random access memory (RAM), and/or a non-volatile memory, such as read-only memory (ROM). The memory 20 may store a variety of information and may be used for various purposes. For example, the memory 20 may store firmware for electronic device 10 (such as basic input/output system (BIOS)), an operating system, and various other programs, applications, or routines that may be executed on electronic device 10. In addition, the memory 20 may be used for buffering or caching during operation of the electronic device 10.
The components of the device 10 may further include other forms of computer-readable media, such as non-volatile storage 22 for persistent storage of data and/or instructions. Non-volatile storage 22 may include, for example, flash memory, a hard drive, or any other optical, magnetic, and/or solid-state storage media. Non-volatile storage 22 may be used to store firmware, data files, software programs, wireless connection information, and any other suitable data.
The embodiment illustrated in
The components depicted in
The electronic device 10 may take the form of a computer system or some other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, tablet, and handheld computers), as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, electronic device 10 in the form of a computer may include a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac® Pro available from Apple Inc. of Cupertino, Calif. By way of example, an electronic device 10 in the form of a laptop computer 30 is illustrated in
The display 12 may be integrated with the computer 30 (e.g., such as the display of the depicted laptop computer) or may be a standalone display that interfaces with the computer 30 using one of the I/O ports 14, such as via a DisplayPort, Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI), or analog (D-sub) interface. For instance, in certain embodiments, such a standalone display 12 may be a model of an Apple Cinema Display®, available from Apple Inc.
Although an electronic device 10 is generally depicted in the context of a computer in
Handheld device 36 of the presently illustrated embodiment includes a display 12, which may be in the form of an LCD 34. The LCD 34 may display various images generated by the handheld device 36, such as a graphical user interface (GUI) 38 having one or more icons 40. The device 36 may also include various I/O ports 14 to facilitate interaction with other devices, and user input structures 16 to facilitate interaction with a user.
One example of an LCD display 34 is depicted in
The backlight unit 44 includes one or more light sources 48. Light from the light source 48 is routed through portions of the backlight unit 44 (e.g., a light guide and optical films) and generally emitted toward the LCD panel 42. In various embodiments, light source 48 may include a cold-cathode fluorescent lamp (CCFL), one or more light emitting diodes (LEDs), or any other suitable source(s) of light. Further, although the LCD 34 is generally depicted as having an edge-lit backlight unit 44, it is noted that other arrangements may be used (e.g., direct backlighting) in full accordance with the present technique.
Referring now to
Each unit pixel 60 includes a pixel electrode 66 and thin film transistor (TFT) 68 for switching the pixel electrode 66. In the depicted embodiment, the source 70 of each TFT 68 is electrically connected to a data line 62 extending from respective data line driving circuitry 56, and the drain 72 is electrically connected to the pixel electrode 66. Similarly, in the depicted embodiment, the gate 74 of each TFT 68 is electrically connected to a scanning line 64 extending from respective scanning line driving circuitry 58.
In one embodiment, column drivers of the data line driving circuitry 56 send image signals to the pixels via the respective data lines 62. Such image signals may be applied by line-sequence, i.e., the data lines 62 may be sequentially activated during operation. The scanning lines 64 may apply scanning signals from the scanning line driving circuitry 58 to the gate 74 of each TFT 68. Such scanning signals may be applied by line-sequence with a predetermined timing or in a pulsed manner.
Each TFT 68 serves as a switching element which may be activated and deactivated (i.e., turned on and off) for a predetermined period based on the respective presence or absence of a scanning signal at its gate 74. When activated, a TFT 68 may store the image signals received via a respective data line 62 as a charge in the pixel electrode 66 with a predetermined timing.
The image signals stored at the pixel electrode 66 may be used to generate an electrical field between the respective pixel electrode 66 and a common electrode. Such an electrical field may align liquid crystals within a liquid crystal layer to modulate light transmission through the LCD panel 42. Unit pixels 60 may operate in conjunction with various color filters, such as red, green, and blue filters. In such embodiments, a “pixel” of the display may actually include multiple unit pixels, such as a red unit pixel, a green unit pixel, and a blue unit pixel, each of which may be modulated to increase or decrease the amount of light emitted to enable the display to render numerous colors via additive mixing of the colors.
In some embodiments, a storage capacitor may also be provided in parallel to the liquid crystal capacitor formed between the pixel electrode 66 and the common electrode to prevent leakage of the stored image signal at the pixel electrode 66. For example, such a storage capacitor may be provided between the drain 72 of the respective TFT 68 and a separate capacitor line.
Certain components for processing image data and rendering images on an LCD 34 based on such data are depicted in block diagram 80 of
As noted above, data, which may include image data that may be processed by circuitry of the LCD 34 to drive pixels 60 of, and render an image on, the LCD 34, may be transmitted from the GPU 94 to the display 12. This data may be received by the timing controller 100. In one embodiment, the timing controller 100 may operate to control the timing of the data line driving circuitry 56 or the scanning line driving circuitry 58 of the LCD 34. Control of the data line driving circuitry 56 or the scanning line driving circuitry 58 (which may include a single switched column driver or multiple column drivers in each of data line driving circuitry 56 and a single switched row driver or multiple row drivers in each of the scanning line driving circuitry 58) may be accomplished through generation and transmission of display signals (e.g., via a driver 102). These display signals may be based on the data received along path 96 and/or based on control signals received along path 96 and may include column driver signals transmitted to column drivers 104 in the data line driving circuitry 56 as well as gate pulse signals transmitted to the gate drivers 106 in the scanning line driving circuitry 58 of the LCD 34.
The column drivers 104 and row drivers 106 may generate analog signals for driving the various pixels 60 of a pixel array of the LCD 34. In some embodiments, the timing controller 100 may transmit data and timing signals to the column drivers 104 via, for example, one or more flex circuits 108. The column drivers 104, or other circuitry in the data line driving circuitry 56, may then forward appropriate timing or data information to the row drivers 106. In other embodiments, the timing controller 100 may directly provide timing information to each of the column drivers 104 and the row drivers 106.
Additionally, the display 12 may include a frame buffer 110 that may be utilized in place of the frame buffer 98. Frame buffer 110 may be coupled to the timing controller 100 and may be utilized to store data relating to a single frame (i.e., the period of time to transmit data to all pixels 60 in the display 12) to be displayed on the LCD 34 at a given time. The data stored in the frame buffer 110 may, for example, be retrieved by the timing controller 100 in a particular order. For example, data or timing signals relating to even numbered video scan lines 64 for a given frame may retrieved by the timing controller 100 for transmission to the LCD 34. Subsequently, data or timing signals relating to odd numbered video scan lines 64 for a given frame may retrieved by the timing controller 100 for transmission to the LCD 34. In this manner, a frame buffer 110 local to the timing controller 100 may be utilized to alter the transmission of data or timing signals to the LCD 34. It should be noted that the same process described above for modified retrieval of data from frame buffer 110 may alternatively be performed by the GPU 94 in conjunction with frame buffer 98. For example, instead of transmitting a whole frame of data to the display 12, the GPU 12 may retrieve and transmit data relating to even numbered video scan lines 64 for a given frame and subsequently may retrieve and transmit data relating to odd numbered video scan lines 64 for the LCD 34.
To aid in preventing biasing of the liquid crystal layer of the LCD panel 42, periodic inversion of the electric field applied to the liquid crystal layer may be utilized. For example, a dot inversion method may cause each adjacent unit pixel 60 in the liquid crystal layer to be driven with a voltage opposite of its neighboring unit pixel 60 over a given time frame. This dot inversion technique is illustrated in
As illustrated in
This process may be repeated for each unit pixel 60c-60e, as illustrated by directional arrows 118, 120, and 122 until each unit pixel 60a-60e has been updated with a value corresponding to a respective output of the column driver 104l. Moreover, this process may be concurrently applied across each of column drivers 104a-104l and row drivers 106a-106e. When each of the unit pixels 60 has been updated by column driver output 112a-112l, a frame (i.e., an update to the entire matrix 54 of unit pixels 60) has been completed. These frames may occur, for example at a rate of 30, 60, or more frames per second.
Once a frame has been completed, the column driver outputs 112a-112l may be inverted by inverting oscillating signal transmitted to the column drivers 104a-104l during a second frame immediately subsequent to the first frame. That is, in the second frame, unit pixels 60a, 60c, 60e, etc. receive positive values while unit pixels 60b, 60d, 60f, etc. receive negative values. This result is illustrated in
While the oscillation of the polarity of the unit pixels 60 in subsequent frames is desirable to aid in the prevention of biasing of the LCD 34, utilization of an oscillating signal transmitted to the column drivers 104a-104l to generate column driver outputs 112a-112l may require a substantial amount of power to drive the liquid crystals in each of the unit pixels to an alternating voltage polarity in a periodic manner. That is, each transition of the column drivers 104a-104l (each generation of an oscillation of the column driver outputs 112a-112l) consumes power at a rate higher than transmitting a positive or negative voltage from the column drivers 104a-104l at lower rate. Thus, it may be beneficial to drive unit pixels 60 of matrix 54, as illustrated in
For example, column driver output 124l may first be a negative voltage, for example −5 volts. This value may be output from column driver 104l at a first time period during a single frame. As this negative voltage is transmitted from column driver 104l along source line 62l, a gate signal may be transmitted along gate line 64a from row driver 106a. This may cause unit pixel 60a to be driven by the value transmitted from the column driver 104l (represented in
After all of the odd rows of source line 62l have been driven to a negative voltage by a negatively charged column driver output 124l, the column driver output 124l may be driven to a positive voltage, for example, 5 volts. This value may be output from column driver 104l at a time period immediately subsequent to the last unit pixel 60 in an odd row of the matrix 54 being driven by the column driver output 124l. As this positive voltage is transmitted from column driver 104l along source line 62l, a gate signal may be transmitted along gate line 64b from row driver 106b. This may cause unit pixel 60b to be driven by the positive value transmitted from the column driver 104l (represented in
When each of the unit pixels 60 has been updated by column driver output 124a-124l, a frame (i.e., an update of data to the entire matrix 54 of unit pixels 60) has been completed. These frames may occur, for example at a rate of 30, 60, or more frames per second. This may occur for each of the column drivers 104a-104l such that the matrix 54 includes unit pixels 60 each driven to an opposite polarity of its immediately row and column adjacent unit pixels 60. Moreover, the image data to be displayed may be pre-arranged before being scanned into display 34. That is, each of the odd and even rows of data may be grouped such that as the even rows scanned to the display 34 followed by the odd rows to match with the order of gate line driving so that final image displayed is correct.
Once a frame has been completed, the column driver outputs 124a-124l may be switched back to a negative value transmitted to the even rows of the matrix 54 (including, e.g., unit pixels 60b and 60d) followed by a negative value transmitted to the odd rows of the matrix 54 (including, e.g., unit pixels 60a, 60c, and 60e) during the next frame immediately subsequent to the first frame. Alternatively, once the first frame has been completed, the column driver outputs 124a-124l may continue to transmit a positive value which may be read into the odd rows of the matrix 54 (including, e.g., unit pixels 60a, 60c, and 60e) followed by a negative value transmitted to the even rows of the matrix 54 (including, e.g., unit pixels 60b and 60d) during the next frame immediately subsequent to the first frame. In either case, in the second frame, unit pixels 60a, 60c, 60e, etc. receive positive values while unit pixels 60b, 60d, 60f, etc. receive negative values. Thus, the column driver outputs 124a-124l may be utilized to generate the identical results illustrated in matrix 54 in
At the end of the first half 138 of a frame 140, the output 138 may switch to a positive value, e.g., 5 volts. This value may also be transmitted to a column driver, e.g., column driver 104l. Thus, during the second half 142 of frame 140, various gates may be sequentially activated, as represented by gate output signals 150 and 152. For example, gate output signal 150 may correspond to a signal transmitted along gate line 64b from row driver 106b, while gate output signal 152 may correspond to a signal transmitted along gate line 64d from row driver 106d.
However, a potential problem may exist if as the output 136 switches from a negative value to a positive value, the voltage of the output 136 may not have settled to the proper (positive) level. This may cause, for example, insufficient charging of one of the unit pixels 60 driven as the output 136 is switching.
At the end of the first time period 154 of a frame 140, but prior to the final time period 156 of frame 140, may be an intermediary time period 158, which may equal, for example, the activation time for a gate output signal, e.g., signal 144. During this intermediary time period 158, no gates may be activated and either dummy data (i.e., a data value not to be displayed on the display 12) or no data may be transmitted to the LCD 34. Instead, during this intermediary time period 158, the output 136 may be allowed to settle at a positive value, for example, 5 volts.
Upon the completion of the intermediary time period 158, a final time period 156 of the frame 140 may begin, during which various gates may be sequentially activated, as represented by gate output signals 150 and 152. For example, gate output signal 150 may correspond to a signal transmitted along gate line 64b from row driver 106b, while gate output signal 152 may correspond to a signal transmitted along gate line 64d from row driver 106d. This process may be repeated for a second and any subsequent frames, as well as for each of the column drivers 104a-104l.
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.
