PATENT DOCUMENT

Publication Number: US-11626047-B1
Application Number: US-202117405497-A
Country: US
Kind Code: B1

Title: Reference array current sensing

Abstract:
Embodiments disclosed herein provide systems and methods for testing and compensating for pixel degradation in an electronic display based on current and voltage values sensed in a reference array. An electronic display includes an active array, a reference array, and sensing circuitry. A compensation manager obtains current data values of the reference array from the sensing circuitry. The compensation manager generates a current-voltage curve based on the current data and adjusts the current-voltage curve to compensate for variations in temperature and/or pixel brightness. In this way, the compensation manager may improve performance of the electronic display by, for example, by reducing visible anomalies.

Claims:
The invention claimed is: 
     
       1. An electronic device comprising:
 a reference array comprising a first plurality of pixels of a display panel; 
 reference array sensing circuitry configured to acquire a first plurality of currents by consecutively sensing a current in each pixel of the first plurality of pixels during a burst sensing operation; 
 an active array of the display panel comprising a second plurality of pixels; and 
 a compensation manager configured to:
 generate an initial current-voltage curve based on the first plurality of currents and a target current; 
 determine one or more gamma tap points based on the initial current-voltage curve; 
 receive a second plurality of currents associated with a first pixel of the first plurality of pixels during a plurality of vertical blanking periods of a plurality of frames of image data, wherein the plurality of frames of image data is received after the burst sensing operation; 
 generate an updated current-voltage curve based on the initial current-voltage curve and each current of the second plurality of currents sensed in the first pixel; 
 determine one or more updated gamma tap points based on the updated current-voltage curve. 
 
 
     
     
       2. The electronic device of  claim 1 , the electronic device comprising:
 active array sensing circuitry configured to acquire a third plurality of currents associated with a second pixel of the second plurality of pixels. 
 
     
     
       3. The electronic device of  claim 2 , wherein the compensation manager is configured to program the second pixel based on the updated current-voltage curve and the third plurality of currents. 
     
     
       4. The electronic device of  claim 2 , wherein the compensation manager comprises a negative feedback loop configured to continuously update the initial current-voltage curve and an additional current used to program the second pixel. 
     
     
       5. The electronic device of  claim 1 , wherein the burst sensing operation is performed upon start-up of the electronic device. 
     
     
       6. The electronic device of  claim 1 , wherein the burst sensing operation comprises obtaining the first current at a number of consecutive gamma tap points. 
     
     
       7. The electronic device of  claim 1 , wherein the compensation manager is configured to apply a loop gain and a clamping threshold to the first current and the second current before generating or updating the initial current-voltage curve. 
     
     
       8. An electronic device comprising:
 a reference array comprising a first plurality of pixels; 
 reference array sensing circuitry configured to acquire a first plurality of currents by consecutively sensing a current in each pixel of the first plurality of currents during a burst sensing operation; 
 an active array comprising a second plurality of pixels; and 
 a gate driver coupled to the second plurality of pixels; and 
 a compensation manager configured to:
 perform the burst sensing operation to obtain baseline current data based on the first plurality of currents; 
 perform subsequent sensing operations to receive a second plurality of currents associated with a first pixel of the first plurality of pixels during a plurality of vertical blanking periods of a plurality of frames of image data, wherein the plurality of frames of image data is received after the burst sensing operation; 
 generate a current-voltage curve based on the baseline current data and the second plurality of currents; 
 determine a set of gamma tap points for each brightness setting of an electronic display based at least in part on the current-voltage curve; and 
 instruct the gate driver to program the second plurality of pixels based on image data and the set of gamma tap points. 
 
 
     
     
       9. The electronic device of  claim 8 , wherein the compensation manager is configured to:
 generate an initial current-voltage curve based on the first plurality of currents; 
 determine an initial set of gamma tap points based at least in part on the initial current-voltage curve; and 
 instruct the gate driver to program the second plurality of pixels based on the initial set of gamma tap points. 
 
     
     
       10. The electronic device of  claim 9 , wherein the compensation manager performs the subsequent sensing operations at a periodic time interval. 
     
     
       11. The electronic device of  claim 8 , wherein the burst sensing operation is performed upon start-up of the electronic device and wherein the burst sensing operation comprises obtaining the current at a number of consecutive gamma tap points based at least in part on the current-voltage curve. 
     
     
       12. The electronic device of  claim 11 , wherein the gate driver drives illumination of the second plurality of pixels based at least in part on the set of gamma tap points. 
     
     
       13. The electronic device of  claim 8 , wherein the compensation manager comprises a negative feedback loop to continuously update the current-voltage curve and a current used to program the second plurality of pixels. 
     
     
       14. The electronic device of  claim 8 , wherein the active array does not include light emitting diodes (LEDs) during a testing procedure. 
     
     
       15. A method comprising:
 obtaining current-voltage data associated with a plurality of currents in an electronic display by consecutively sensing a current in each pixel of a plurality of pixels in the electronic display during a burst sensing operation; 
 obtaining a target current for a pixel in a reference array of the electronic display; 
 sensing a pixel current through the pixel after performing the burst sensing operation; 
 determining a delta between the target current and the pixel current; 
 generating an adjusted delta by applying a loop gain and a clamping threshold to the delta; 
 combining the adjusted delta and the current-voltage data as compensated current-voltage data; and 
 driving one or more pixels of an active array of the electronic display based at least in part on the compensated current-voltage data. 
 
     
     
       16. The method of  claim 15 , comprising:
 generating a current-voltage curve based at least in part on the target current and the pixel current; 
 periodically sensing a new pixel current through the pixel; and 
 updating the current-voltage curve based at least in part on the new pixel current. 
 
     
     
       17. The method of  claim 16 , wherein the burst sensing operation is performed on start-up of the electronic display and comprises obtaining current-voltage data at a number of consecutive gamma tap points based at least in part on the current-voltage curve. 
     
     
       18. The method of  claim 16 , comprising:
 determining a set of gamma tap points for each brightness setting of the electronic display based at least in part on the current-voltage curve. 
 
     
     
       19. The method of  claim 18 , wherein the set of gamma tap points is used to obtain a target brightness level at the one or more pixels of the active array. 
     
     
       20. The method of  claim 18 , comprising:
 driving the one or more pixels of the active array based at least in part on the set of gamma tap points.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/083,676, filed Sep. 25, 2020, and entitled “REFERENCE ARRAY CURRENT SENSING,” which is incorporated herein by reference in its entirety for all purposes. 
    
    
     SUMMARY 
     The present disclosure generally relates to electronic displays and, more particularly, to testing and compensating for pixel degradation in an electronic display based on current and voltage values sensed in a reference array. 
     Flat panel displays, such as light-emitting diode (LED) displays or organic-LED (OLED) displays, are commonly used in a wide variety of electronic devices, including such consumer electronics such as televisions, computers, and handheld devices (e.g., cellular telephones, audio and video players, gaming systems, and so forth). Such display panels typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such devices may 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. 
     Electronic displays typically include pixels arranged in a matrix to display an image that may be viewed by a user. Individual pixels of an LED display may generate light as current is applied to each pixel. Current may be applied to each pixel by programming a voltage to the pixel that is converted by circuitry of the pixel into the current. The circuitry of the pixel that converts the voltage into the current may include, for example, thin film transistors (TFTs). However, certain operating conditions, such as aging or temperature, may affect the amount of current applied to a pixel in relation to the programmed voltage. 
     Display panel sensing allows for operational properties of pixels of an electronic display to be identified to improve the performance of the electronic display. For example, variations in temperature and periphery circuit aging (e.g., an LDO) (among other things) across the electronic display cause pixels on the display to behave differently. Indeed, the same image data programmed on different pixels of the display could appear to be different due to the variations in temperature and periphery circuit aging. For example, a pixel emits an amount of light, gamma, or grey level based at least in part on an amount of current supplied to a diode (e.g., an LED) of the pixel. For voltage-driven pixels, a target voltage may be applied to the pixel to cause a target current to be applied to the diode (e.g., as expressed by a current-voltage relationship or curve) to emit a target gamma value. Variations may affect a pixel by, for example, changing the resulting current that is applied to the diode when applying the target voltage. Without appropriate compensation, these variations could produce undesirable visual artifacts. 
     Accordingly, the techniques and systems described below may be used to test and compensate for the functionality of various components of the display. A compensation manager may compensate for degradation of one or more pixels in the display based on current and voltage values sensed from a reference array that is used for the testing. The compensation manager may determine a current through circuitry of each pixel of the display to confirm operation of each pixel and corresponding components. 
     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 described below. 
         FIG.  1    is a block diagram of an electronic device, according to an embodiment of the present disclosure. 
         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 front view of another handheld device representing another embodiment of the electronic device of  FIG.  1   . 
         FIG.  5    is a front view of a desktop computer representing another embodiment of the electronic device of  FIG.  1   . 
         FIG.  6    is a perspective view of a wearable electronic device representing another embodiment of the electronic device of  FIG.  1   . 
         FIG.  7    is a block diagram of an example architecture for closed-loop compensation based on a current-voltage curve, according to an embodiment of the present disclosure. 
         FIG.  8    is a timing diagram for a sensing operation of a reference array, according to some embodiments of the present disclosure. 
         FIG.  9    is a block diagram of an example architecture of the compensation manager of  FIG.  7   , according to some embodiments of the present disclosure. 
         FIG.  10    illustrates a current-voltage curve based on data sensed from the reference array, according to some embodiments of the present disclosure. 
         FIG.  11    is a flowchart for sensing and compensation using the architecture of  FIG.  7   , according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     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&#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. Furthermore, the phrase A “based on” B is intended to mean that A is at least partially based on B. Moreover, the term “or” is intended to be inclusive (e.g., logical OR) and not exclusive (e.g., logical XOR). In other words, the phrase A “or” B is intended to mean A, B, or both A and B. 
     Electronic displays are ubiquitous in modern electronic devices. As electronic displays gain ever-higher resolutions and dynamic range capabilities, image quality has increasingly grown in value. In general, electronic displays contain numerous picture elements, or “pixels,” that are programmed with image data. Each pixel emits a particular amount of light based at least in part on the image data. By programming different pixels with different image data, graphical content including images, videos, and text can be displayed. 
     Display panel sensing allows for operational properties of pixels of an electronic display to be identified to improve the performance of the electronic display. For example, variations in temperature and periphery circuit (e.g., an LDO) aging (among other things) across the electronic display cause pixels on the display to behave differently from calibration. Indeed, the same calibrated image data could appear to be different due to the variations in temperature and periphery circuit aging. For example, a pixel emits an amount of light, gamma, or grey level based at least in part on an amount of current supplied to a diode (e.g., an LED) of the pixel. For voltage-driven pixels, a target voltage may be applied to the pixel to cause a target current to be applied to the diode (e.g., as expressed by a current-voltage relationship or curve) to emit a target gamma value. Variations may affect a pixel by, for example, changing the resulting current that is applied to the diode when applying the target voltage. Without appropriate compensation, these variations could produce undesirable visual artifacts. 
     Accordingly, the techniques and systems described below may be used to test and compensate for functionality of various components of the display. Testing circuitry is coupled to an active array and a reference array of the display. The testing circuitry may determine current and/or voltage for driving pixels of the active array based at least in part on current and/or voltage data sensed from the reference array. The testing circuitry may determine a current through circuitry of each pixel of the reference array and compensate for variations of the display, such as temperature and periphery circuit aging. 
     With this in mind, a block diagram of an electronic device  10  is shown in  FIG.  1   . As will be described in more detail below, the electronic device  10  may represent any suitable electronic device, such as a computer, a mobile phone, a portable media device, a tablet, a television, a virtual-reality headset, a vehicle dashboard, or the like. The electronic device  10  may represent, for example, a notebook computer  10 A as depicted in  FIG.  2   , a handheld device  10 B as depicted in  FIG.  3   , a handheld device  10 C as depicted in  FIG.  4   , a desktop computer  10 D as depicted in  FIG.  5   , a wearable electronic device  10 E as depicted in  FIG.  6   , or a similar device. 
     The electronic device  10  shown in  FIG.  1    may include, for example, a processor core complex  12 , a local memory  14 , a main memory storage device  16 , an electronic display  18 , input structures  22 , an input/output (I/O) interface  24 , network interfaces  26 , and a power source  29 . The various functional blocks shown in  FIG.  1    may include hardware elements (including circuitry), software elements (including machine-executable instructions stored on a tangible, non-transitory medium, such as the local memory  14  or the main memory storage device  16 ) 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 . Indeed, the various depicted components may be combined into fewer components or separated into additional components. For example, the local memory  14  and the main memory storage device  16  may be included in a single component. 
     The processor core complex  12  may carry out a variety of operations of the electronic device  10 , such as causing the electronic display  18  to perform display panel sensing and generate a current-voltage (IV) curve that may be used to adjust image data to be displayed on the electronic display  18 . The processor core complex  12  may include any suitable data processing circuitry to perform these operations, such as one or more microprocessors, one or more application specific processors (ASICs), or one or more programmable logic devices (PLDs). In some cases, the processor core complex  12  may execute programs or instructions (e.g., an operating system or application program) stored on a suitable article of manufacture, such as the local memory  14  and/or the main memory storage device  16 . In addition to instructions for the processor core complex  12 , the local memory  14  and/or the main memory storage device  16  may also store data to be processed by the processor core complex  12 . By way of example, the local memory  14  may include random access memory (RAM) and the main memory storage device  16  may include read only memory (ROM), rewritable non-volatile memory such as flash memory, hard drives, optical discs, or the like. 
     The electronic display  18  may display image frames, such as a graphical user interface (GUI) for an operating system or an application interface, still images, or video content. The processor core complex  12  may supply at least some of the image frames. The electronic display  18  may be a self-emissive display, such as an organic light emitting diodes (OLED) display, a micro-LED display, a micro-OLED type display, or a liquid crystal display (LCD) illuminated by a backlight. In some embodiments, the electronic display  18  may include a touch screen, which may allow users to interact with a user interface of the electronic device  10 . The electronic display  18  may employ display panel sensing to identify operational variations of the electronic display  18 . This may allow the processor core complex  12  to adjust image data that is sent to the electronic display  18  to compensate for these variations, thereby improving the quality of the image frames appearing on the electronic display  18 . 
     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 interface  26 . The network interface  26  may include, for example, interfaces for a personal area network (PAN), such as a Bluetooth network, for a local area network (LAN) or wireless local area network (WLAN), such as an 802.11x Wi-Fi network, and/or for a wide area network (WAN), such as a cellular network. The network interface  26  may also include interfaces for, for example, broadband fixed wireless access networks (WiMAX), mobile broadband wireless networks (mobile WiMAX), asynchronous digital subscriber lines (e.g., ADSL, VDSL), digital video broadcasting-terrestrial (DVB-T) and its extension DVB Handheld (DVB-H), ultra wideband (UWB), alternating current (AC) power lines, and so forth. The power source  29  may include any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
     In certain embodiments, the electronic device  10  may take the form of a computer, a portable electronic device, a wearable electronic device, 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. of Cupertino, Calif. By way of example, the electronic device  10 , taking the form of a notebook computer  10 A, is illustrated in  FIG.  2    in accordance with one embodiment of the present disclosure. The depicted computer  10 A may include a housing or enclosure  36 , an electronic 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  10 A, such as to start, control, or operate a GUI or applications running on computer  10 A. For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on the electronic display  18 . 
       FIG.  3    depicts a front view of a handheld device  10 B, which represents one embodiment of the electronic device  10 . The handheld device  10 B 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  10 B may be a model of an iPod® or iPhone® available from Apple Inc. The handheld device  10 B 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 electronic display  18 . The I/O interfaces  24  may open through the enclosure  36  and may include, for example, an I/O port for a hard wired connection for charging and/or content manipulation using a standard connector and protocol, such as the Lightning connector provided by Apple Inc., a universal serial bus (USB), or other similar connector and protocol. 
     User input structures  22 , in combination with the electronic display  18 , may allow a user to control the handheld device  10 B. For example, the input structures  22  may activate or deactivate the handheld device  10 B, navigate user interface to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  10 B. Other input structures  22  may provide volume control, or may toggle between vibrate and ring modes. The input structures  22  may also include a microphone may obtain a user&#39;s voice for various voice-related features, and a speaker may enable audio playback and/or certain phone capabilities. The input structures  22  may also include a headphone input may provide a connection to external speakers and/or headphones. 
       FIG.  4    depicts a front view of another handheld device  10 C, which represents another embodiment of the electronic device  10 . The handheld device  10 C may represent, for example, a tablet computer or portable computing device. By way of example, the handheld device  10 C 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. 
     Turning to  FIG.  5   , a computer  10 D may represent another embodiment of the electronic device  10  of  FIG.  1   . The computer  10 D may be any computer, such as a desktop computer, a server, or a notebook computer, but may also be a standalone media player or video gaming machine. By way of example, the computer  10 D may be an iMac®, a MacBook®, or other similar device by Apple Inc. It should be noted that the computer  10 D may also represent a personal computer (PC) by another manufacturer. A similar enclosure  36  may be provided to protect and enclose internal components of the computer  10 D such as the electronic display  18 . In certain embodiments, a user of the computer  10 D may interact with the computer  10 D using various peripheral input devices, such as input structures  22 A or  22 B (e.g., keyboard and mouse), which may connect to the computer  10 D. 
     Similarly,  FIG.  6    depicts a wearable electronic device  10 E representing another embodiment of the electronic device  10  of  FIG.  1    that may operate using the techniques described herein. By way of example, the wearable electronic device  10 E, which may include a wristband  43 , may be an Apple Watch® by Apple, Inc. However, in other embodiments, the wearable electronic device  10 E may include any wearable electronic device such as, for example, a wearable exercise monitoring device (e.g., pedometer, accelerometer, heart rate monitor), or other device by another manufacturer. The electronic display  18  of the wearable electronic device  10 E may include a touch screen display  18  (e.g., LCD, OLED display, active-matrix organic light emitting diode (AMOLED) display, and so forth), as well as input structures  22 , which may allow users to interact with a user interface of the wearable electronic device  10 E. 
       FIG.  7    is a block diagram of an example architecture  100  for closed-loop compensation based on a current-voltage curve, according to an embodiment of the present disclosure. The architecture  100  includes compensation circuitry  104  coupled to the display panel  61 . As illustrated, the display panel  61  includes a number of gate drivers  90  coupled to the active array  62  and the reference array  64 . The active array  62  comprises a first number of pixels  63  and the reference array comprises a second number of pixels  65 . The reference array  64  may include any suitable number (e.g., 1-1000) of columns of pixels  65 . In some embodiments, a number of the pixels  65  in the reference array may be equal to or less than a number of the pixels  63  in the active array  62 . 
     The display panel  61  may also include a sensing analog front end (AFE)  66  to perform analog sensing of the response of the pixels  63 ,  65  to input data. In some embodiments, the AFE  66  may be used for sensing in both the active array  62  and the reference array  64 . In alternative or additional embodiments, there may be at least a first AFE used for sensing in the active array  62  and at least a second AFE used for sensing in the reference array  64 . 
     The display panel  61  may also include a digital-to-analog converter (DAC)  92 . The DAC  92  may be a gamma DAC and provide gamma correction to the pixels  63 ,  65  of the active array and/or reference array based on the IV curve, as discussed below. As illustrated, the DAC  92  is coupled to and shared by the reference array  64  and the active array  62 . In additional or alternative embodiments, at least a first DAC may be coupled to the active array  62  and at least a second DAC may be coupled to the reference array  64 . 
     As illustrated, the compensation circuitry  104  includes an optical calibration  98 , a reference array manager  96 , a compensation manager  102 , and a clock  94 . The optical calibration  98  may provide a target current value to be applied to a diode of a pixel  63 ,  65  to emit a target gamma value. In some embodiments, the target current value may be based on a current and/or voltage sensed at the respective pixel  65  in the reference array  64 . 
     The reference array manager  96  include a timing controller (TCON) and may share some functionality of the processor core complex  12  with respect to the reference array  64 . For example, the reference array manager  96  may cause the reference array  64  to perform a sensing operation and generate a current-voltage (IV) curve that may be used to adjust image data to be displayed on the electronic display  18  via the active array  62 . In some embodiments, the reference array manager  96  may control timing of the sensing operation of the reference array  64 . For example, the reference array manager  96  may determine an interval at which the sensing operation is performed on the pixels  65  of the reference array  64 . 
     The compensation manager  102  may receive the IV curve (e.g., IV data) from the reference array manager  96  and determine an amount of compensation to adjust the image data. In some embodiments, the compensation manager  102  may generate an IV spline coefficient for the reference array  64 . In some embodiments, the compensation manager may be implemented via hardware elements (including circuitry), software elements (including machine-executable instructions stored on a tangible, non-transitory medium, such as the local memory  14  or the main memory storage device  16  discussed with respect to  FIG.  1   ) or a combination of both hardware and software elements. The compensation manager  102  is discussed in detail below with respect to  FIG.  9   . 
     In some embodiments, the compensation manager  102  may send signals across gate lines of the display panel  61  to cause a row of pixels  63  of the active array  62  to become activated and programmable, at which point the compensation manager  102  may transmit the image data (e.g., input data to be displayed by the display panel  61 ) across data lines (e.g., via the gate drivers  90 ) to program the pixels  63  to display a particular grey level (e.g., individual pixel brightness). By supplying the image data to different pixels  63  of different colors, full-color images may be programmed into the pixels  63  of the active array  62  of the display panel  61 . 
     The compensation manager  102  may also send signals across gate lines to cause a row of pixels  65  of a reference array  64  to become activated and programmable. For example, the compensation manager  102  may send signals to the pixels  65  of the reference array via the gate drivers  90 . The reference array  64  may not be visible to a user of the electronic device  10 . For example, the reference array  64  may be covered by an opaque structure or material (e.g., black material) that blocks sight of the reference array  64  from view. In some embodiments, the reference array  64  may wrap around an edge or back side of the electronic device  10  such that it is hidden from view. 
     In some embodiments, the compensation manager  102  may send sense control signals  68  to cause the display  18  to perform display panel sensing. In response, the display  18  may send sense feedback representing digital information relating to the operational variations of the display  18 . The sense feedback may be input to the compensation manager  102  and take any suitable form. An output of the compensation manager  102  may take any suitable form and may be converted into a compensation value that, when applied to the image data, appropriately compensates for operational changes of the display  18  (e.g., resulting in global changes to the display  18 ). This may result in greater fidelity of the image data, reducing or eliminating visual artifacts that would otherwise occur due to the operational variations of the display  18 . 
       FIG.  8    is a timing diagram  110  for a sensing operation of a reference array  64 , according to some embodiments of the present disclosure. The timing diagram  110  illustrates various types of sensing operations that may occur at startup and during normal operation of the electronic device  10 . For example, at startup  112  of the electronic device, a burst sensing operation  114  may occur. Subsequently, a normal sensing operation  116 ,  118  may be used. That is, the burst sensing operation  114  may occur once when the electronic device is powered on. Subsequent sensing operations may be normal sensing operations  116 ,  118 . 
     After the electronic device is turned on at operation  120 , the burst sensing operation  122  may be initialized to consecutively sense a current and/or voltage at multiple pixels  65  of the reference array  64 . In some embodiments, the current-voltage data from the burst sensing operation  122  may be used to generate one or more taps to be used for determining compensation values for the pixels  63  of the active array  62 . As an example, between 5 and 20 taps may be used. That is, the burst sensing operation  122  may be used to determine tap points on the IV curve to be compared to the target current value from the optical calibration  98 . 
     After the burst sensing operation  122 , data  124  may be sent to the active array  62  to program the pixels  63  thereof. The normal sensing operations  116 ,  118  may be performed on the pixels  65  of the reference array  64  during a vertical blank  126  of each image frame programmed at the pixels  63  of the active array  62 . In some embodiments, the normal sensing operations  116 ,  118  may be time triggered to occur at a given time interval (e.g., two seconds). In this way, the normal sensing operations  116 ,  118  may continuously track current and/or temperature drift of the pixels  63 ,  65 . 
     The timing diagram  110  illustrates how the burst sensing operation  114  occurs at the start-up of the electronic device  10  and is used to determine baseline data for the IV curve. Then, the normal sensing operations  116 ,  118  are executed to obtain current sensing data that is used to update the IV curve. The various sensing operations  114 ,  116 ,  118  are used to obtain sensing data to generate and update the IV curve to improve an accuracy of the IV curve over time and track the operation of the electronic display  18 . 
       FIG.  9    is a block diagram of an example architecture of the compensation manager  102  of  FIG.  7   , according to some embodiments of the present disclosure. The compensation manager  102  receives the IV sensing data  130  from the burst sensing operation  122  as a baseline. The IV sensing data  130  from the burst sensing operation  122  is used to compute initial gamma tap points  145  for the reference array  64 . The initial gamma tap points  145  may be computed based on an initial IV curve generated from the burst sensing data  130 . Once the normal sensing operation  116 ,  118  is performed, the compensation manager  102  receives a digitized current from the AFE  66 . A normalizer  134  normalizes the digitized current. A comparator  136  compares and determines a delta between the normalized current and target currents  132 . The target current  123  may be provided by the optical calibration unit  98  and may be a current to which the reference array is expected to converge and has a range large enough to cover the entire gamma range of a calibration current  148 . 
     The compensation manager  102  multiplies the delta by a loop gain  138  and clamps  140  the output of the loop gain  138  to reduce any sudden increase in the voltage applied to the corresponding pixel  63  which could cause a sudden change in the luminance change during operation of the display panel  61 . The loop gain  138  and the clamping threshold  140  may depend on the slope of the IV curve. Thus, the value of the loop gain  138  and the clamping threshold  140  may be determined to match or closely resemble the slope of the IV curve. This may lead to a smooth settling of the voltage applied to the corresponding pixel  63  in the active array  62 . In some embodiments, the clamping  140  may be performed using a clamping threshold which is grey level dependent. That is, for a low grey level of the corresponding pixel, a high clamping threshold  140  may be used. The output of the clamping threshold  140  is one or more tapcode adjustments  146  for the gamma tap points  145 . An accumulator  142  adds the tapcode adjustments  146  and the gamma tap points  145 . An output of the accumulator  142  is one or more gamma tap points  141  for the reference array  64 . In some embodiments, spline interpolation  144  may be applied to the burst sensing data  130  for smoothing of the IV curve. In that case, the output of the spline interpolation  144  includes the initial gamma tap points  145  for the reference array  64 . 
     The compensation manager  102  compensates for variations in temperature and periphery circuit aging and ensures that a proper voltage is applied to pixels  63  in the active array  62  based on the input image data. In this way, the compensation manager may increase a performance of the display  18  by reducing visible anomalies. 
     To generate gamma tap points  143  for the active array  62 , cubic spline interpolation  147  may be applied to a combination of calibrated pixel currents  148 , the gamma tap points  141  of the reference array  64 , and the target currents  132 . The calibrated pixel currents  148  may be current values that when applied to various pixels of the display  18  cause a target luminance of the pixels at selected grey levels. The gamma tap points  143  for the active array  62  are used to drive pixel drivers of pixels  63  in the active array  62 . That is, the gamma tap points  143  for the active array  62  and the gamma tap points  141  of the reference array  64  are provided to the DAC  92  of the display panel  61 , as discussed with respect to  FIG.  7   . 
       FIG.  10    illustrates a current-voltage (IV) curve  150  based on data sensed from the reference array  64 , according to some embodiments of the present disclosure. As shown, the IV curve  150  is plotted on a logarithmic scale. In some embodiments, the IV curve  150  may be based on a different scale to make the IV curve  150  more linear. A number of taps  160  (e.g., gamma tap points) are determined based on the current-voltage data from the burst sensing operation  122 . A current value corresponding to the taps  160  may be used by the compensation manager  102  to determine compensation values to be applied to the pixels  63  of the active array  62  to compensate for variations in pixel temperature and periphery circuit aging. In some embodiments, the taps  160  may be used to obtain a target brightness level at the pixel  63  of the active array  62 . 
     As shown, the IV curve  150  includes various curves corresponding to different temperatures of the reference array  64  and/or the pixels  65  of the reference array  64 . For example, a first IV curve  152  may correspond to a temperature of about 50 degrees Celsius, a second IV curve  154  may correspond to a temperature of about 35 degrees Celsius, a third IV curve  156  may correspond to a temperature of about 20 degrees Celsius, and a fourth IV curve  158  may correspond to a temperature of about 5 degrees Celsius. Thus, the IV curve  150  may be based at least in part on a temperature of the reference array  64  and/or the pixels  65  of the reference array  64 . 
       FIG.  11    is a flowchart  161  for sensing and compensation using the architecture of  FIG.  7   , according to an embodiment of the present disclosure. The example operations of the flowchart  161  may be performed by one or more components of the electronic device  10  of  FIG.  1   , including, for example, the processor core complex  12 . Moreover, the flowchart  161  is merely an example of the operations that may be performed, and at least some operations of the flowchart  161  may be performed in a different order or skipped altogether. 
     The flowchart  161  begins at operation  162  where a target current  132  is obtained by the compensation manager  102 . The optical calibration unit  98  may provide the target current  132  to the compensation manager  102 . The target current  132  may be based on a target luminance level (e.g., brightness level) for a corresponding pixel at a particular grey level. That is, the target current  132  when applied to pixels of the display  18  satisfies a target luminance of the display panel  61  at a particular grey level. The target current  132  may be a target convergence current of the reference array  64 . That is, the target current  132  is a current to which the reference array  64  is expected to converge. At operation  164 , a pixel current is sensed and obtained by the compensation manager  102 . The pixel current may be received from the analog front end (AFE)  66  of the display  18 . The pixel current may be measured at a corresponding pixel  65  of the reference array  64  and converted to a digitized current by the AFE  66 . 
     At operation  166 , the compensation manager  102  determines a difference between the target current  132  and the pixel current. At operation  168 , the compensation manager  102  computes tapcode adjustments  146  (e.g., adjustments to the gamma tap points  141 ,  143 ) by applying a loop gain  138  and a clamping threshold  140  to the difference  136  determined at operation  166 . The loop gain  138  and the clamping threshold  140  may be computed to satisfy a slope of a current-voltage curve generated from burst sensing data  130 , as discussed above with respect to  FIGS.  8  and  9   . 
     At operation  170 , the compensation manager  102  generates reference array tapcodes (e.g., gamma tap points) based on the tapcode adjustments and initial tapcodes generated from the burst sensing operation. To do so, the compensation manager  102  may aggregate (e.g., combine) the tapcode adjustments  146  and the initial tapcodes  145  to adjust the initial tapcodes  145  based on the tapcode adjustments  146 . As discussed with respect to  FIGS.  8 - 10   , the burst sensing data  130  may provide baseline data to generate the current-voltage curve. The reference array tapcodes  141  determined at operation  170  may be used to drive one or more pixels  65  in the reference array  64 . 
     At operation  172 , the compensation manager  102  computes active array tapcodes  143  (e.g., gamma tap points  143  of the active array  62 ) based on the reference array tap codes  141  determined at operation  170 , the target current  132 , and a calibration current  148 . The calibration current  148  may be a current that when applied to various pixels of the display  18  causes a target luminance of the pixels at selected grey levels. The active array tapcodes  143  may be used to drive pixels  63  of the pixels  63  of the active array  62  via one or more drivers (e.g., source drivers and/or gate drivers) of the display  18 . That is, the active array tapcodes  143  may be provided to the DAC  92  of the display panel  61  to drive the pixels  63  of the active array  62 . During operation of the display  18 , the compensation manager  102  may periodically obtain a new target current  132  and pixel current, and update the current-voltage curve and tapcodes  143  used to drive the pixels  63  of the active array  62  using the operations of the flowchart  161 . That is, the operations of the flowchart  161  may be used to update and track the current-voltage curve over time and compensate for variations in temperature and periphery circuit aging, among other things. 
     The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ,” it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Metadata:
Filing Date: 20210818
Publication Date: 20230411
Grant Date: 20230411
Priority Date: 20200925
Inventors: CAI, SHENGCHANG
AKYOL, HASAN
YANG, XUEBEI
ZHANG, SHENG
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2330/026", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0693", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/029", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3685", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3275", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0693", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0693", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2330/12", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 85805143