PATENT DOCUMENT

Publication Number: US-11282458-B2
Application Number: US-202016897206-A
Country: US
Kind Code: B2

Title: Systems and methods for temperature-based parasitic capacitance variation compensation

Abstract:
Systems and methods are presently disclosed that compensate for temperature-based parasitic capacitance variation of a pixel of a display by causing a driver transistor of the pixel to enter an ohmic or linear region. A lookup table is generated based on temperatures at the pixel, diode voltages, and target diode currents or luminances at a diode of the pixel. A correction voltage is determined based on a target diode current or luminance, a temperature at the pixel, and the lookup table. A data voltage is applied corresponding to the target diode current or luminance and the correction voltage to the driver transistor.

Claims:
What is claimed is: 
     
       1. A mobile electronic device comprising:
 a display comprising a pixel, wherein the pixel comprises:
 a diode configured to emit a luminance based at least on a current through the diode; and 
 a transistor configured to control the current flowing through the diode based at least on a voltage received; and 
 
 processing circuitry separate from but communicatively coupled to the display, wherein the processing circuitry is configured to:
 cause the display to operate the transistor to enter a linear region; 
 determine a plurality of diode voltages that generate a plurality of target diode currents of the diode at a plurality of temperatures at the pixel based at least on a difference between a positive supply voltage and a negative supply voltage supplied to the pixel; 
 generate a lookup table based at least on the plurality of temperatures, the plurality of diode voltages, and the plurality of target diode currents; 
 receive a target diode current and a temperature at the pixel; 
 apply the target diode current to the lookup table to determine a diode voltage per temperature; 
 determine a product of at least the diode voltage per temperature and the temperature at the pixel; 
 determine a correction voltage based on the product of at least the diode voltage per temperature and the temperature at the pixel; and 
 apply a data voltage corresponding to the target diode current and the correction voltage to the transistor. 
 
 
     
     
       2. The mobile electronic device of  claim 1 , wherein the processing circuitry is configured to cause the display to operate the transistor to enter the linear region by at least increasing the negative supply voltage. 
     
     
       3. The mobile electronic device of  claim 2 , wherein the negative supply voltage is increased such that a first voltage across a drain terminal and a source terminal of the transistor is less than a difference between a second voltage across a gate terminal and the source terminal of the transistor and a threshold voltage of the transistor. 
     
     
       4. The mobile electronic device of  claim 2 , wherein the processing circuitry is configured to set the negative supply voltage such that a first voltage across a drain terminal and a source terminal of the transistor is greater than or equal to a difference between a second voltage across a gate terminal and the source terminal of the transistor and a threshold voltage of the transistor prior to applying the data voltage. 
     
     
       5. The mobile electronic device of  claim 1 , wherein the lookup table represents changes in diode voltage per temperature depending on diode current. 
     
     
       6. The mobile electronic device of  claim 1 , wherein the processing circuitry is configured to determine the correction voltage based on a coupling efficiency and the product of at least the diode voltage per temperature and the temperature at the pixel. 
     
     
       7. The mobile electronic device of  claim 6 , wherein the coupling efficiency represents a relationship of a parasitic capacitance at a gate terminal of the transistor to a storage capacitance of a storage capacitor of the pixel. 
     
     
       8. The mobile electronic device of  claim 6 , wherein the processing circuitry is configured to determine the correction voltage based on an additional product of the coupling efficiency and the product of at least the diode voltage per temperature and the temperature at the pixel. 
     
     
       9. A method for compensating for temperature-based parasitic capacitance variation of a pixel of a display, wherein the method comprises:
 causing a transistor of the pixel to enter a linear region; 
 generating a lookup table based at least on a plurality of temperatures at the pixel, a plurality of diode voltages, and a plurality of target diode currents or a plurality of target luminances at a diode of the pixel; 
 applying a target diode current or a target luminance to the lookup table to determine a diode voltage per temperature; 
 determining a product of at least the diode voltage per temperature and a temperature at the pixel; 
 determining a correction voltage based on the product of at least the diode voltage per temperature and the temperature at the pixel; and 
 applying a data voltage corresponding to the target diode current or the target luminance and the correction voltage to the transistor. 
 
     
     
       10. The method of  claim 9 , wherein the plurality of diode voltages are configured to generate the plurality of target diode currents or the plurality of target luminances of the diode at the plurality of temperatures. 
     
     
       11. The method of  claim 9 , comprising determining each diode voltage of the plurality of diode voltages by at least determining a difference between a positive supply voltage and a negative supply voltage supplied to the pixel. 
     
     
       12. The method of  claim 11 , wherein each diode voltage is determined while the transistor is in the linear region. 
     
     
       13. The method of  claim 9 , comprising causing the transistor to enter a saturation region. 
     
     
       14. The method of  claim 13 , wherein the data voltage is applied while the transistor is in the saturation region. 
     
     
       15. A display comprising:
 a pixel comprising:
 a diode configured to emit a luminance based at least on a current through the diode; and 
 a transistor configured to control the current flowing through the diode based at least on a voltage received; and 
 
 a driver-integrated circuit configured to:
 cause the transistor to enter a linear region; 
 generate a lookup table based at least on a plurality of temperatures at the pixel, a plurality of diode voltages, and a plurality of target luminances at the diode; 
 apply a target luminance at the diode to the lookup table to determine a diode voltage per temperature; 
 determine a product of at least the diode voltage per temperature and a temperature at the pixel; 
 determine a correction voltage based on the product of at least the diode voltage per temperature and the temperature at the pixel; 
 cause the transistor to enter a saturation region; and 
 apply a data voltage corresponding to the target luminance and the correction voltage to the transistor. 
 
 
     
     
       16. The display of  claim 15 , wherein entering the linear region causes the transistor to act as a resistor. 
     
     
       17. The display of  claim 15 , wherein entering the saturation region causes the transistor to act as a current source. 
     
     
       18. The display of  claim 15 , wherein the plurality of diode voltages are configured to generate the plurality of target luminances of the diode at the plurality of temperatures. 
     
     
       19. The display of  claim 15 , wherein the driver-integrated circuit is configured to determine each diode voltage of the plurality of diode voltages by at least determining a difference between a positive supply voltage and a negative supply voltage supplied to the pixel. 
     
     
       20. The display of  claim 15 , wherein each diode voltage is determined while the transistor is in the linear region.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/859,613, entitled “Systems and Methods for Temperature-Based Parasitic Capacitance Variation Compensation,” filed Jun. 10, 2019, which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     The present disclosure relates to devices and methods for improving performance of certain electronic display devices including, for example, light emitting diode (LED) displays, such as organic light emitting diode (OLED) displays, active matrix organic light emitting diode (AMOLED) displays, or micro LED (μLED) displays. Under certain conditions, non-uniformity of a display induced by process, non-uniformity temperature gradients, or other factors across the display may be compensated for to increase performance of a display (e.g., reduce visible anomalies). The non-uniformity of pixels in a display may vary between devices of the same type (e.g., two similar phones, tablets, wearable devices, or the like), vary over time and usage (e.g., due to aging and/or degradation of the pixels or other components of the display), and/or vary with respect to temperatures, as well as in response to additional factors. 
     To improve display panel uniformity, compensation techniques related to adaptive correction of the display may be employed. For example, as pixel response (e.g., luminance and/or color) can vary due to component processing, temperature, usage, aging, and the like, in one embodiment, to compensate for non-uniform pixel response, a property of the pixel (e.g., a current or a voltage) may be measured (e.g., sensed via a sensing operation) and compared to a target value that is, for example, stored in a lookup table or the like, to generate a correction value to be applied to correct pixel illuminations to match a desired gray level. In this manner, modified data values may be transmitted to the display to generate compensated image data (e.g., image data that accurately reflects the intended image to be displayed by adjusting for non-uniform pixel responses). 
     Various refinements of the features noted above may be made in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a schematic block diagram of an electronic device that performs display sensing and compensation, in accordance with an embodiment; 
         FIG. 2  is a perspective view of a notebook computer representing an embodiment of the electronic device of  FIG. 1 ; 
         FIG. 3  is a front view of a hand-held device representing another embodiment of the electronic device of  FIG. 1 ; 
         FIG. 4  is a front view of another hand-held 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 front view and side view of a wearable electronic device representing another embodiment of the electronic device of  FIG. 1 ; 
         FIG. 7  is a block diagram of a system for display sensing and compensation of the electronic device of  FIG. 1 , according to an embodiment of the present disclosure; 
         FIG. 8  is a schematic diagram of the system for display sensing and compensation of  FIG. 7 , according to an embodiment of the present disclosure; 
         FIG. 9  is a circuit diagram of a display pixel of the electronic display of the electronic device of  FIG. 1 , according to embodiments of the present disclosure; 
         FIG. 10  is a circuit diagram of a portion of the pixel of  FIG. 9  with a driver thin-film transistor (TFT) in an active or saturation region, according to embodiments of the present disclosure; 
         FIG. 11  is a plot of an example driver TFT current-voltage relationship and an example diode current-voltage relationship when the driver TFT of  FIG. 10  is in the active or saturation region, according to embodiments of the present disclosure; 
         FIG. 12  is a circuit diagram of a portion of the pixel of  FIG. 9  with the driver TFT in an ohmic or linear region, according to embodiments of the present disclosure; 
         FIG. 13  is a plot of an example driver TFT current-voltage relationship and an example diode current-voltage relationship when the driver TFT of  FIG. 12  is in the ohmic or linear region, according to embodiments of the present disclosure; 
         FIG. 14  is a block diagram of a driver-integrated circuit of the display of the electronic device of  FIG. 1  using a lookup table that represents changes in diode voltage per temperature depending on diode luminance to determine a correction voltage, according to embodiments of the present disclosure; 
         FIG. 15  is a plot of example curves representing changes in diode voltage per temperature depending on diode luminance for which lookup tables may be determined, according to embodiments of the present disclosure; 
         FIG. 16  is a block diagram of image and data generation and processing circuitry using a lookup table that represents changes in diode voltage per temperature depending on diode current to determine a correction voltage, according to embodiments of the present disclosure; 
         FIG. 17  is a plot of example curves representing changes in diode voltage per temperature depending on diode current for which lookup tables may be determined, according to embodiments of the present disclosure; 
         FIG. 18  is process for compensating for temperature-based parasitic capacitance variation in the display of the electronic device of  FIG. 1 , according to embodiments of the present disclosure; and 
         FIG. 19  is a circuit diagram of a portion of the pixel of  FIG. 9  with a correction voltage being applied, according to embodiments 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 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 pixel aging (among other things) across the electronic display cause pixels in different locations 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 pixel aging. Without appropriate compensation, these variations could produce undesirable visual artifacts. However, compensation of these variations may hinge on proper sensing of differences in the images displayed on the pixels of the display. Accordingly, the techniques and systems described below may be utilized to enhance the compensation of operational variations across the display. 
     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  28 . 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 using the feedback to adjust image data for display 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  28  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. 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. of Cupertino, Calif. 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. of Cupertino, Calif. 
     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 be configured to 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 a system  50  for display sensing and compensation of the electronic device  10  of  FIG. 1 , according to an embodiment of the present disclosure. The system  50  includes the processor core complex  12 , which includes image correction circuitry  52 . The image correction circuitry  52  may receive image data  54 , and compensate for non-uniformity of the display  18  based on and induced by process non-uniformity temperature gradients, aging of the display  18 , and/or other factors across the display  18  to increase performance of the display  18  (e.g., by reducing visible anomalies). The non-uniformity of pixels in the display  18  may vary between devices of the same type (e.g., two similar phones, tablets, wearable devices, or the like), over time and usage (e.g., due to aging and/or degradation of the pixels or other components of the display  18 ), and/or with respect to temperatures, as well as in response to additional factors. 
     As illustrated, the system  50  includes aging/temperature determination circuitry  56  that may determine or facilitate determining the non-uniformity of the pixels in the display  18  due to, for example, aging and/or degradation of the pixels or other components of the display  18 . The aging/temperature determination circuitry  56  that may also determine or facilitate determining the non-uniformity of the pixels in the display  18  due to, for example, temperature. The variation in temperature may be due to changes in ambient temperature and/or a proximity of the pixels to a heat source (e.g., a fingertip of a user). In some cases, the pixels may be laying on top of or be in otherwise close proximity to other components of an electronic device that may be more densely packed with components due to the relatively small size of the electronic device (e.g., handheld, mobile, or portable electronic devices such as  10 B,  10 C,  10 E). As such, the variation in temperature may be due to operation of the components that the pixels are laying on top of or are in close proximity to. 
     The image correction circuitry  52  may send the image data  54  (for which the non-uniformity of the pixels in the display  18  have or have not been compensated for by the image correction circuitry  52 ) to analog-to-digital converter  58  of a driver-integrated circuit  60  of the display  18 . The analog-to-digital conversion converter  58  may digitize the image data  54  when it is in an analog format. The driver-integrated circuit  60  may send signals across gate lines to cause a row of pixels of a display panel  62 , including pixel  64 , to become activated and programmable, at which point the driver-integrated circuit  60  may transmit the image data  54  across data lines to program the pixels, including the pixel  64 , to display a particular gray level (e.g., individual pixel brightness). By supplying different pixels of different colors with the image data  54  to display different gray levels, full-color images may be programmed into the pixels. The driver-integrated circuit  60  may also include a sensing analog front end (AFE)  66  to perform analog sensing of the response of the pixels to data input (e.g., the image data  54 ) to the pixels. 
     The processor core complex  12  may also send sense control signals  68  to cause the display  18  to perform display panel sensing. In response, the display  18  may send display sense feedback  70  that represents digital information relating to the operational variations of the display  18 . The display sense feedback  70  may be input to the aging/temperature determination circuitry  56 , and take any suitable form. Output of the aging/temperature determination circuitry  56  may take any suitable form and be converted by the image correction circuitry  52  into a compensation value that, when applied to the image data  54 , appropriately compensates for non-uniformity of the display  18 . This may result in greater fidelity of the image data  54 , reducing or eliminating visual artifacts that would otherwise occur due to the operational variations of the display  18 . In some embodiments, the processor core complex  12  may be part of the driver-integrated circuit  60 , and as such, be part of the display  18 . 
       FIG. 8  is a schematic diagram of the system  50  for display sensing and compensation of  FIG. 7 , according to an embodiment of the present disclosure. The processor core complex  12  may include image data generation and processing circuitry  80  to generate the image data  54  for display by the electronic display  18 . The image data generation and processing circuitry  80  represents various circuitry and processing that may be employed by the processor core complex  12  to generate the image data  54  and control the electronic display  18 . As such, the image data generation and processing circuitry  80  may include, for example, the image correction circuitry  52  and/or the aging/temperature determination circuitry  56  of  FIG. 7 . In some embodiments, the image data generation and processing circuitry  80  may include a graphics processing unit, a display pipeline, or the like, to facilitate control of operation of the electronic display  18 . The image data generation and processing circuitry  80  may include a processor and memory such that the processor of the image data generation and processing circuitry  80  may execute instructions and/or process data stored in memory of the image data generation and processing circuitry  80  to control operation of the electronic display  18 . 
     To compensate for operational variations of the electronic display  18  due to, for example, temperature variation or aging of the display  18 , the processor core complex  12  may provide sense control signals  82  to cause the electronic display  18  to perform display panel sensing and generate display sense feedback  84 . The display sense feedback  84  represents digital information relating to the operational variations of the electronic display  18 . The display sense feedback  84  may take any suitable form, and may be converted by the image data generation and processing circuitry  80  into a compensation value that, when applied to the image data  54 , appropriately compensates for the conditions of the electronic display  18  in the image data  54 . This may result in greater fidelity of the image data  54 , reducing or eliminating visual artifacts that would otherwise occur due to the operational variations of the electronic display  18 . 
     The electronic display  18  includes an active area  86  with an array of pixels  64 . The pixels  64  are schematically shown distributed substantially equally apart and of the same size, but in an actual implementation, pixels of different colors may have different spatial relationships to one another and may have different sizes. In one example, each pixel  64  may have a red-green-blue (RGB) format that includes red, green, and blue pixels or sub-pixels. In another example, the pixels  64  may take a red-green-blue-green (RGBG) format in a diamond pattern. The pixels  64  are controlled by the driver-integrated circuit  60 , which may be a single module or may be made up of separate modules, such as a column or source driver-integrated circuit  88  and a row or gate driver-integrated circuit  90 . The driver-integrated circuit  60  (e.g., the row driver-integrated circuit  90 ) may send signals across gate lines  92  (e.g., using gate drivers) to cause a row of pixels  64  to become activated and programmable, at which point the driver-integrated circuit  60  (e.g., the column driver-integrated circuit  88 ) may transmit image data signals across data lines  94  to program the pixels  64  to display a particular gray level (e.g., individual pixel brightness). By supplying different pixels  64  of different colors with image data  54  to display different gray levels, full-color images may be programmed into the pixels  64 . The image data  54  may be driven to an active row of pixels  64  via source drivers  96 , which may also be referred to as column drivers. 
     Regardless of the particular arrangement and layout of the pixels  64 , each pixel  64  may be sensitive to changes on the active area  86  of the electronic display  18 , such as variations and temperature of the active area  86 , as well as the overall age of the pixel  64 . Indeed, when each pixel  64  is a light emitting diode (LED), it may gradually emit less light over time. This effect is referred to as aging, and takes place over a slower time period than the effect of temperature on the pixel  64  of the electronic display  18 . 
     As described above, the electronic display  18  may display image frames through control of the luminance of the pixels  64  based on the received image data  54 . When a pixel  64  is activated (e.g., via a gate activation signal across a gate line  92  activating a row of pixels  64 ), luminance of a display pixel  64  may be adjusted by image data  54  received via a data line  94  coupled to the pixel  64 . Thus, as depicted, each pixel  64  may be located at an intersection of a gate line  92  (e.g., which may act as, include, or be disposed alongside a scan line) and a data line  94  (e.g., a source line). Based on the received image data  54 , the luminance of a display pixel  64  may be adjusted using electrical power supplied from a power source  28 , for example, via power a supply lines coupled to the pixel  64 . 
     In some embodiments, to facilitate displaying an image frame, a timing controller may determine and transmit timing data to a gate driver of the row driver-integrated circuit  90  based on the image data  54 . For example, in the depicted embodiment, the timing controller may be included in the column driver-integrated circuit  88 . The column driver-integrated circuit  88  may receive image data  54  that indicates desired luminance of one or more display pixels  64  for displaying an image frame of the image data  54 , analyze the image data  54  to determine the timing data based on the display pixels  64  that the image data  54  corresponds to, and transmit the timing data to the gate driver of the row driver-integrated circuit  90 . Based on the timing data, the gate driver may then transmit gate activation signals to activate a row of display pixels  64  via a gate line  92 . 
     As illustrated, the image data generation and processing circuitry  80  may be externally coupled to the electronic display  18 . For example, the image data generation and processing circuitry  80  may be included in the processor core complex  12 , which is separate from but communicatively coupled to the electronic display  18  and the driver-integrated circuit  60  (including the column driver-integrated circuit  88  and the row driver-integrated circuit  90 ) of the electronic display  18 . Additionally or alternatively, the image data generation and processing circuitry  80  may represent separate circuitry from the processor core complex  12 . In some cases, the image data generation and processing circuitry  80  may be modular from the display  18  and conveniently updated and/or replaced (e.g., compared to if it were integrated in the display  18 ). In other cases, the image data generation and processing circuitry  80  may be a component of the electronic display  18  itself. Moreover, in cases where the system  50  is part of a component-dense electronic device  10  (such as the handheld devices  10 B-C or the wearable electronic device  10 E) that would place a display-integrated image data generation and processing circuitry in close proximity to (e.g., underlying) the pixels  64 , heat generated from the image data generation and processing circuitry  80  may combine or intermix with the heat generated from the pixels  64 , which may result in inaccurate temperature measurements of the pixels  64 . However, in other embodiments, the image data generation and processing circuitry  80  may be part of the display  18 . 
     Display panel sensing may be used to obtain the display sense feedback  84 , which may enable the processor core complex  12  to generate compensated image data  54  to negate the effects of temperature, aging, and other variations of the active area  86 . The driver-integrated circuit  60  (e.g., the column driver-integrated circuit  88 ) may include the sensing analog front end (AFE)  66  to perform analog sensing of the response of pixels  64  to test data (e.g., test image data) or user data (e.g., user image data). It should be understood that further references to test data or test image data in the present disclosure include test data and/or user data. The analog signal may be digitized by sensing analog-to-digital conversion circuitry (ADC)  58 . 
     For example, to perform display panel sensing, the electronic display  18  may program one of the pixels  64  with test data (e.g., having a particular reference voltage or reference current). The sensing analog front end  66  then senses (e.g., measures, receives, etc.) at least one value (e.g., voltage, current, etc.) along sense line  98  connected to the pixel  64  that is being tested. Here, the data lines  94  are shown to act as extensions of the sense lines  98  of the electronic display  18 . In other embodiments, however, the display active area  86  may include other dedicated sense lines  98  or other lines of the display  18  (e.g., such as the gate or scan lines  92 ) may be used as sense lines  98  instead of the data lines  94 . In some embodiments, other pixels  64  that have not been programmed with test data may be also sensed at the same time a pixel  64  that has been programmed with test data is sensed. Indeed, by sensing a reference signal on a sense line  98  when a pixel  64  on that sense line  98  has not been programmed with test data, a common-mode noise reference value may be obtained. This reference signal can be removed from the signal from the test pixel  64  that has been programmed with test data to reduce or eliminate common mode noise. 
     The analog signal may be digitized by the sensing analog-to-digital conversion circuitry  58 . The sensing analog front end  66  and the sensing analog-to-digital conversion circuitry  58  may operate, in effect, as a single unit. The driver-integrated circuit  60  (e.g., the column driver-integrated circuit  88 ) may also perform additional digital operations to generate the display sense feedback  84 , such as digital filtering, adding, or subtracting, to generate the display sense feedback  84 , or such processing may be performed by the processor core complex  12 . 
       FIG. 9  is a circuit diagram of a display pixel  64  of the electronic display  18  of the electronic device  10  of  FIG. 1 , according to embodiments of the present disclosure. The circuit diagram of the display pixel  64  is intended to represent one example of pixel circuitry that may benefit from this disclosure, and is not intended to be exhaustive. Indeed, many other pixel circuits may benefit from the systems and methods of this disclosure. In the example of  FIG. 9 , the display pixel  64  may include a circuit-switching thin-film transistor (TFT)  110 , a driver TFT  112 , a storage capacitor  114 , and a diode  116  (e.g., an OLED). The storage capacitor  114  and/or the diode  116  may be coupled to any suitable negative or ground power supply voltage, V SS    118 . That is, the negative power supply voltage, V SS    118  (which may be provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ), may provide between 0 and, for example, −100 Volts (V), such as a voltage of zero, −1 V, −2 V, −4 V, −6 V, or any other suitable negative or ground voltage. While V SS    118  is referred to as a negative or ground power supply voltage, it should be understood this is with respect to the positive power supply voltage V DD    120 . As such, in some cases, V SS    118  may be positive, as long as it provides a voltage that is less than V DD    120 . For example, if V DD    120  is 4 V, then V SS    118  may be 2 V. Moreover, variations may be utilized in place of the illustrated pixel  64 . For example,  FIG. 9  illustrates the circuit-switching TFT  110  as a p-channel metal-oxide-semiconductor (PMOS) TFT. However, in some embodiments, the circuit-switching TFT  110  may be an n-channel metal-oxide-semiconductor (NMOS) TFT. Similarly,  FIG. 9  illustrates the driver TFT  112  as an NMOS TFT, though, in some embodiments, the driver TFT  112  may be a PMOS TFT. 
     To facilitate adjusting luminance and operating the diode  116 , the switching TFT  110  and the driver TFT  112  may each serve as a switching device that may couple to or decouple from other circuits and be controllably turned on and off by voltage applied to their respective gates. In the depicted embodiment, the gate of the circuit-switching TFT  110  is electrically coupled to a gate line  122 . Accordingly, when a gate activation signal (e.g., an emission voltage EM which may be provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ) received from the gate line  122  is below a threshold voltage, the first circuit-switching TFT  110  may turn on, thereby activating the pixel  64  and charging the storage capacitor  114  with image data received at data line  124 . When the gate activation signal received from the gate line  122  is above the threshold voltage, the circuit-switching TFT  110  may turn off, thereby deactivating the pixel  64  and ceasing charging of the storage capacitor  114  with the image data received at the data line  124 . The signal received by the driver TFT  112  from the data line  124  may be referred to as a V GS  signal  126 , since it is received between the gate and the source of the driver TFT  112 . 
     Additionally, in the depicted embodiment, the gate of the driver TFT  112  is electrically coupled to the storage capacitor  114 . As such, voltage of the storage capacitor  114  may control operation of the driver TFT  112 . More specifically, in some embodiments, the driver TFT  112  may be operated in an active or saturation region to control magnitude of supply current flowing through the diode  116 , such as from a power supply providing positive supply voltage V DD    120 . That is, the positive power supply voltage, V DD    120  (which may be provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ), may provide between 0 and, for example, 100 V, such as a voltage of zero, 1 V, 2 V, 4 V, 6 V, or any other suitable positive voltage (relative to the negative or ground power supply voltage, V SS    118 ). In other words, as gate voltage V G    128  (e.g., storage capacitor  114  voltage) increases above a threshold voltage, the driver TFT  112  may increase the amount of its channel available to conduct electrical current, thereby increasing supply current flowing to the diode  116 . On the other hand, as the gate voltage V G    128  decreases while still being above the threshold voltage, the driver TFT  112  may decrease the amount of its channel available to conduct electrical current, thereby decreasing supply current flowing to the diode  116 . The luminance of the diode  116  is dependent on the amount of current flowing through the diode  116 . In this manner, the luminance of the pixel  64  may be controlled and, when similar techniques are applied across the display  18  (e.g., to additional pixels  64  of the display  18 ), an image may be displayed. 
     However, temperature variation or gradients may alter the luminance or color emitted by the diode  116  due to effects on the driver TFT  112  and/or the diode  116 . For example, when temperature increases at the pixel  64 , more thermally activated charges may be generated in the diode  116  and, as a result, an applied voltage may result in higher current (compared to the current induced at the applied voltage at lower temperatures). 
     Moreover, in a source-follower pixel, the gate of the driver TFT  112  serves as an input, the source of the driver TFT  112  serves as an output, and the drain of the driver TFT  112  may serve as either an input or an output, such as the pixel  64  illustrated in  FIG. 9 . Boot-strapping (or pulling up an operating point of the driver TFT  112  above its power supply rail (e.g., supplying the positive power supply voltage, V DD    120 )) of the gate voltage (V G    128 ) of the pixel  64  occurs through the storage capacitor  114  when anode or input voltage of the diode  116  (or source voltage V S    130  of the driver TFT  112 ) increases during emission to maintain a constant data voltage (V GS    126 ). 
     In some cases, a parasitic capacitance at the gate of the driver TFT  112  (illustrated as C G    132 ) may cause a loss of data voltage (V GS    126 ) during emission, as illustrated by the following equation: 
     
       
         
           
             
               
                 
                   
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       V 
                       G 
                     
                   
                   = 
                   
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       V 
                       S 
                     
                     × 
                     
                       
                         C 
                         ST 
                       
                       
                         
                           C 
                           ST 
                         
                         + 
                         
                           C 
                           G 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ) 
                 
               
             
           
         
       
     
     C ST  represents the storage capacitance (of the storage capacitor  114 ). As such, an increase in gate voltage (ΔV G    128 ) at the driver TFT  112  may not be the same as an increase in anode voltage of the diode  116  or source voltage V S    130  of the driver TFT  112 . Thus, the parasitic capacitance C G    132  at the gate of the driver TFT  112  may result in less effective boot-strapping by the storage capacitor  114 , and possibly undesired luminance and/or color emitted by the diode  116 . 
     In some embodiments, the pixel  64  may include subpixels (e.g., a red subpixel, a green subpixel, and a blue subpixel), each having a respective diode  116 . To have the pixel  64  produce a light of desired luminance and color, the voltage applied to each diode  116  (e.g., the anode voltage of the diode  116  or source voltage V S    130  of the driver TFT  112 ) of each subpixel of the pixel  64  may be different. As such, compensation schemes based on sensing (e.g., current) at the driver TFT  112  may fail to compensate for or take into account the separate and possible different voltage losses due to respective parasitic capacitances C G    132  at diodes  116  of each subpixel of a pixel  64 , resulting in undesired luminance and/or color produced by the pixel  64 . 
     To compensate for operational variations, such as temperature, at a pixel  64 , and particularly to compensate for the effect of the operational variations on parasitic capacitance on the diode  116  of the pixel  64 , the presently disclosure systems and methods include generating a lookup table representing changes in diode voltage (e.g., V Diode ) that correspond to resulting diode currents or luminances at different temperatures. The diode voltage V Diode  may refer to the anode voltage of the diode  116  or source voltage V S    130  of the driver TFT  112 . The changes in diode voltages may be determined based on differences between a positive supply voltage V DD    120  and a negative supply voltage V SS    118 . Because the differences may also include driver TFT voltages when the driver TFT  112  is in an active or saturation region, the driver-integrated circuit  60  may increase the negative supply voltage V SS    118  to place the driver TFT  112  in a linear region. This may cause the driver TFT  112  to operate as a resistor, and reduce or minimize the driver TFT voltages in comparison to the diode voltages. 
     For example,  FIG. 10  is a circuit diagram of a portion of the pixel  64  with the driver TFT  112  in the active or saturation region, according to embodiments of the present disclosure. In particular, the driver TFT  112  may operate in the active or saturation region to control the magnitude of supply current flowing through the diode  116 , causing the diode  116  to emit light. The driver TFT  112  may operate in the active or saturation region when V GS    126  (e.g., the voltage between the gate and the source of the driver TFT  112 , which may include the data voltage provided via the data line  124 ) is greater than V th  (e.g., the threshold voltage of the driver TFT  112 ), and V DS  (e.g., the voltage between the drain and the source of the driver TFT  112 ) is greater than or equal to a difference between V GS    126  and V th , as illustrated in the following equations:
 
 V   GS   &gt;V   th   (Equation 2)
 
 V   DS   ≥V   GS   −V   th   (Equation 3)
 
     V TH  may represent the minimum V GS    126  needed to create a conducting path between the source and drain of the driver TFT  112 . Because, V GS    126  is greater than V TH , the driver TFT  112  acts as a switch that is turned on or closed, and creates a channel that enables current to flow between drain and source. Since V D  (e.g., the drain voltage) is higher than V S  (e.g., the source voltage), the electrons spread out, and conduction is not through a narrow channel but through a broader, two- or three-dimensional current distribution extending away from the interface and deeper in the substrate of the driver TFT  112 . As such, the driver TFT  112  may act as a current source  134 , as illustrated in  FIG. 10 . As a result, the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may be applied in significant portions to both the driver TFT  112  (e.g., V TFT    135 ) and the diode voltage (e.g., V Diode    136 ), and thus may not provide an accurate estimation of the diode voltage V Diode    136 . 
     In particular,  FIG. 11  is a plot of an example driver TFT current-voltage relationship  137  and an example diode current-voltage relationship  138  when the driver TFT  112  is in the active or saturation region, according to embodiments of the present disclosure. The plot illustrates the current  139  between drain and source terminals of the driver TFT  112  in terms of the voltage  140  between the drain and source terminals. As illustrated, the difference  141  between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  is applied in significant portions to both the driver TFT  112  (e.g., V TFT    135 ) and the diode voltage (e.g., V Diode    136 ), illustrated here as a 50-50 relationship between V TFT    135  and V Diode    136 . That is, V TFT    135  and V Diode    136  are comparable in magnitude. Thus, determining the difference  141  between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may not provide an accurate estimation of the diode voltage V Diode    136 . 
     However, when the negative supply voltage V SS    118  is increased to place the driver TFT  112  in an ohmic or linear region, the driver TFT  112  may operate as a resistor, reducing or minimizing the driver TFT voltage V TFT    135  when compared to the diode voltage V Diode    136 . For example,  FIG. 12  is a circuit diagram of a portion of the pixel  64  with the driver TFT  112  in the ohmic or linear region, according to embodiments of the present disclosure. In particular, driver TFT  112  may operate in the ohmic or linear region when V GS    126  is greater than V th , and V DS  is less than to a difference between V GS    126  and V th , as illustrated in the following equations:
 
 V   GS   &gt;V   th   (Equation 4)
 
 V   DS   &lt;V   GS   −V   th   (Equation 5)
 
     As such, the driver TFT  112  acts as a switch that is turned on or closed, and creates a channel is created that enables current to flow between drain and source, but the channel is narrower than the broader two- or three-dimensional current distribution created when the driver TFT  112  is operating in the active or saturation region (e.g., as illustrated in  FIG. 10 ). Thus, the driver TFT  112  may act as a resistor  142 , as illustrated in  FIG. 10 . As a result, the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may be largely applied to the diode voltage (e.g., V Diode    136 ), and only negligibly to the driver TFT  112  (e.g., V TFT    135 ), and thus may provide an accurate estimation of the diode voltage V Diode    136 . 
     In particular,  FIG. 13  is a plot of an example driver TFT current-voltage relationship  137  and an example diode current-voltage relationship  138  when the driver TFT  112  is in the ohmic or linear region, according to embodiments of the present disclosure. As illustrated, the difference  141  between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  is largely applied to the diode voltage (e.g., V Diode    136 ), and only negligibly to the driver TFT  112  (e.g., V TFT    135 ). That is, the difference  141  between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may be “V Diode -dominant” (e.g., when compared to V TFT    135 ). Indeed,  FIG. 13  shows approximately a 95% to 5% relationship between V Diode    136  V TFT    135 . As such, determining the difference  141  between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may an accurate estimation of the diode voltage V Diode    136 . 
     Multiple temperatures may then be applied to the pixel  64 , and, for each temperature, the driver-integrated circuit  60  may apply multiple data voltages to the driver TFT  112  to generate multiple target diode currents or luminances, and determine corresponding diode voltages based on the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118 . The lookup table may be generated based on the temperatures applied, the target diode currents or luminances, and the diode voltages (which represent changes in diode voltage), and represent changes in diode voltage per temperature (e.g., ΔV Diode /Temperature) depending on diode current or luminance (e.g., gray level). 
     The lookup table may then be used to compensate for operational variations. For example, if compensation is performed internally with respect to the display  18 , the driver-integrated circuit  60  may receive a target diode luminance and temperature at the pixel  64  (e.g., as sensed via a temperature sensor of the display  18 ), and determine a correction voltage by applying the target diode luminance and the temperature to the lookup table. The driver-integrated circuit  60  may then apply a data voltage corresponding to the target diode luminance and the correction voltage to the driver TFT  112  to produce the target diode luminance at the diode  116 . If compensation is performed externally with respect to the display  18 , the processor core complex  12  may receive a target diode current and temperature at the pixel  64  (e.g., as sensed via a current sensor of the display  18 ), and determine the correction voltage by applying the target diode current and the temperature to the lookup table. The processor core complex  12  may then instruct the driver-integrated circuit  60  to apply the data voltage corresponding to the target diode current and the correction voltage to the driver TFT  112  to produce the target diode current. 
     With this in mind,  FIG. 14  is a block diagram of the driver-integrated circuit  60  of the display  18  of the electronic device  10  of  FIG. 1  using a lookup table  150  that represents changes in diode voltage per temperature depending on diode luminance to determine a correction voltage  152 , according to embodiments of the present disclosure. As such,  FIG. 14  may illustrate the driver-integrated circuit  60  internally (e.g., with respect to the display  18 ) compensating for operational variations (e.g., temperature variations) at a pixel  64 . The lookup table  150  may be generated by increasing the negative supply voltage V SS    118  to place the driver TFT  112  in a linear region, causing the driver TFT  112  to operate as a resistor, thus reducing or minimizing the presence of the driver TFT voltage in comparison to the presence of the diode voltage when taking a difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118 . Multiple temperatures may then be applied to the pixel  64 , and, for each temperature, the driver-integrated circuit  60  may apply multiple data voltages to the driver TFT  112  to generate multiple target diode luminances, and determine corresponding diode voltages based on the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118 . The lookup table may be generated based on the temperatures applied, the target diode luminances, and the diode voltages (which represent changes in diode voltage), and represent changes in diode voltage per temperature (e.g., ΔV Diode /Temperature) depending on diode luminance (e.g., gray level). For example, a relationship or curve (e.g., a linear relationship or curve) may be generated, extrapolated, and/or interpolated based on the temperatures applied, the target diode luminances, and the diode voltages, and the values in the lookup table may be determined using the relationship or curve. 
       FIG. 15  is a plot of example curves  170 ,  172 ,  174  representing changes in diode voltage per temperature  156  depending on diode luminance  176  for which lookup tables  150  may be determined, according to embodiments of the present disclosure. A pixel  64  may include subpixels (e.g., a red subpixel, a green subpixel, and a blue subpixel), each having a respective diode  116 . To have the pixel  64  produce a light of desired luminance and color, the voltage applied to each diode  116  of each subpixel of the pixel  64  may be different. As such, compensation schemes based on sensing (e.g., current) at the driver TFT  112  may fail to compensate for or take into account the separate and possible different voltage losses due to respective parasitic capacitances C G    132  at diodes  116  of each subpixel of a pixel  64 , resulting in undesired luminance and/or color produced by the pixel  64 . 
       FIG. 15  illustrates a separate curve or relationship corresponding to each subpixel, for which a separate lookup table  150  may be determined. The driver-integrated circuit  60  may use each lookup table to compensate for operational variations that are unique or different for each subpixel, due to the different voltage losses caused by at each subpixel. In particular, a first curve  170  represents changes in diode voltage per temperature  156  depending on diode luminance  176  for a red subpixel of the pixel  64 , a second curve  172  represents changes in diode voltage per temperature  156  depending on diode luminance  176  for a green subpixel of the pixel  64 , and a third curve  174  represents changes in diode voltage per temperature  156  depending on diode luminance  176  for a blue subpixel of the pixel  64 . While each curve  170 ,  172 ,  174  depicts a linear relationship between the changes in diode voltage per temperature  156  and the diode luminance  176 , it should be understood that any suitable relationship is contemplated, such as an exponential relationship, logarithmic relationship, quadratic relationship, random relationship, quasi-random relationship, and so on. 
     The driver-integrated circuit  60  may then use the lookup tables to compensate for operational variations. In particular, as illustrated in  FIG. 14 , the driver-integrated circuit  60  may receive a target diode luminance  154 , and apply the target diode luminance  154  to the lookup table  150  and determine a diode voltage per temperature (e.g., ΔV Diode /Temperature)  156 . In particular, the target diode luminance  154  may be a luminance that is desired to be emitted by the diode  116  such that image data  54  is properly displayed by the pixel  64  (and thus the display  18 ). 
     The driver-integrated circuit  60  may also receive a temperature at the pixel  64  via a virtual temperature map  158 . The virtual temperature map  158  may store temperature values received from, for example, thermal sensors in the display  18 , that correspond to individual pixels  64  or regions (e.g., of pixels  64 ) of the display  18 . As such, the temperature at the pixel  64  may be provided by a temperature value stored in the virtual temperature map  158  that corresponds to the pixel  64  or a region of the display  18  that includes the pixel  64 . In additional or alternative embodiments, the temperature may be provided based on receiving current or voltage measurements at or near the pixel  64 . The driver-integrated circuit  60  may then multiply the diode voltage per temperature  156  by the temperature to determine the correction voltage  152 . 
     In some embodiments, the driver-integrated circuit  60  may receive or determine a coupling efficiency  160  that represents a relationship (e.g., a proportion) of the parasitic capacitance C G    132  at the gate of the driver TFT  112  to the storage capacitance C ST  of the storage capacitor  114 . The coupling efficiency  160  may be determined based on a design layout of the pixel  64 . In such embodiments, the driver-integrated circuit  60  may multiply the diode voltage per temperature  156 , the temperature, and the coupling efficiency to determine the correction voltage  152 . 
     The driver-integrated circuit  60  may then apply a data voltage corresponding to the target diode luminance and the correction voltage to the driver TFT  112  to produce the target diode luminance at the diode  116 . 
     In some cases, compensation for operational variations (e.g., temperature variations) at the pixel  64  may be performed externally (e.g., with respect to the display  18 ), such as by the processor core complex  12 .  FIG. 16  is a block diagram of the image and data generation and processing circuitry  80  of the electronic device  10  of  FIG. 1  using a lookup table  190  that represents changes in diode voltage per temperature depending on diode current to determine a correction voltage  152 , according to embodiments of the present disclosure. The lookup table  190  may be generated by increasing the negative supply voltage V SS    118  to place the driver TFT  112  in a linear region, causing the driver TFT  112  to operate as a resistor, thus reducing or minimizing the presence of the driver TFT voltage in comparison to the presence of the diode voltage when taking a difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118 . Multiple temperatures may then be applied to the pixel  64 , and, for each temperature, the processor core complex  12  may instruct the driver-integrated circuit  60  to apply multiple data voltages to the driver TFT  112  to generate multiple target diode currents, and determine corresponding diode voltages based on the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118 . The lookup table may be generated based on the temperatures applied, the target diode currents, and the diode voltages (which represent changes in diode voltage), and represent changes in diode voltage per temperature (e.g., ΔV Diode /Temperature) depending on diode current. For example, a relationship or curve (e.g., an exponential relationship or curve) may be generated, extrapolated, and/or interpolated based on the temperatures applied, the target diode currents, and the diode voltages, and the values in the lookup table may be determined using the relationship or curve. 
       FIG. 17  is a plot of example curves  210 ,  212 ,  214  representing changes in diode voltage per temperature  156  depending on diode current  216  for which lookup tables  190  may be determined, according to embodiments of the present disclosure. Each separate curve or relationship  210 ,  212 ,  214  corresponds to a respective subpixel of the pixel  64 , and a separate lookup table  190  may be determined for each curve  210 ,  212 ,  214 . The processor core complex  12  may use each lookup table to compensate for operational variations that are unique or different for each subpixel, due to the different voltage losses caused by at each subpixel. In particular, a first curve  210  represents changes in diode voltage per temperature  156  depending on diode current  216  for a red subpixel of the pixel  64 , a second curve  212  represents changes in diode voltage per temperature  156  depending on diode current  216  for a green subpixel of the pixel  64 , and a third curve  214  represents changes in diode voltage per temperature  156  depending on diode current  216  for a blue subpixel of the pixel  64 . While each curve  210 ,  212 ,  214  depicts an exponential relationship between the changes in diode voltage per temperature  156  and the diode current  216 , it should be understood that any suitable relationship is contemplated, such as a linear relationship, logarithmic relationship, quadratic relationship, random relationship, quasi-random relationship, and so on. 
     The processor core complex  12  may then use the lookup tables to compensate for operational variations. In particular, as illustrated in  FIG. 16 , the processor core complex  12  may receive a target diode current  192 , and apply the target diode current  192  to the lookup table  190  and determine a diode voltage per temperature (e.g., ΔV Diode /Temperature)  156 . In particular, the target diode current  192  may be a current that is desired to be supplied to the diode  116  that causes the diode  116  to emit a luminance such that image data  54  is properly displayed by the pixel  64  (and thus the display  18 ). 
     The processor core complex  12  may also receive a temperature at the pixel  64  via a sensed temperature map  194 . The sensed temperature map  194  may store temperature values received or derived from, for example, current or voltage values determined via current or voltage sensors in the display  18 . The temperature values may correspond to individual pixels  64  or regions (e.g., of pixels  64 ) of the display  18 . As such, the temperature at the pixel  64  may be provided by a temperature value stored in the sensed temperature map  194  that corresponds to the pixel  64  or a region of the display  18  that includes the pixel  64 . In additional or alternative embodiments, the temperature may be provided based on receiving temperature measurements at or near the pixel  64 . The processor core complex  12  may then multiply the diode voltage per temperature  156  by the temperature to determine the correction voltage  152 . 
     In some embodiments, the processor core complex  12  may receive or determine a coupling efficiency  160  that represents a relationship or proportion of the parasitic capacitance C G    132  at the gate of the driver TFT  112  to the storage capacitance C ST  of the storage capacitor  114 . The coupling efficiency  160  may be determined based on a design layout of the pixel  64 . In such embodiments, the processor core complex  12  may multiply the diode voltage per temperature  156 , the temperature, and the coupling efficiency to determine the correction voltage  152 . 
     The processor core complex  12  may then instruct the driver-integrated circuit  60  to apply a data voltage corresponding to the target diode current and the correction voltage to the driver TFT  112  to produce the target diode current at the diode  116 . 
     With this in mind,  FIG. 18  is process  230  for compensating for temperature-based parasitic capacitance variation in the display  18  of the electronic device  10  of  FIG. 1 , according to embodiments of the present disclosure. The process  230  may be repeated for multiple pixels  64  (and subpixels of the pixels  64 ) to determine multiple target voltages to be applied at respective driver TFTs  112  of the multiple pixels  64  (and subpixels) to compensate for temperature-based parasitic capacitance variation at each of the multiple pixels  64  (and subpixels). While the process  230  is described using steps in a specific sequence, it should be understood that the present disclosure contemplates that the describe steps may be performed in different sequences than the sequence illustrated, and certain described steps may be skipped or not performed altogether. 
     In some embodiments, such as when compensation is performed externally (with respect to the display  18 ), the process  230  may be implemented by executing instructions stored in a tangible, non-transitory, computer-readable medium, such as the local memory  14  and/or the main memory storage device  16 , using a processor, such as the processor core complex  12 , and, in particular, the image correction circuitry  52  and/or the aging/temperature determination circuitry  56  of the processor core complex  12  shown in  FIG. 7 . In alternative or additional embodiments, such as when compensation is performed internally (with respect to the display  18 ), the process  230  may be performed by the driver-integrated circuit  60  and/or implemented by the processor core complex  12  causing or instructing components of the display  18 , such as the driver-integrated circuit  60 , to carry out instructions. 
     As illustrated, in process block  232 , the driver-integrated circuit  60  increases the negative power supply voltage V SS    118  to place the driver TFT  188  of a pixel  64  in the ohmic or linear region. As a result, the driver TFT  188  may act as a resistor  142  (e.g., as shown in the circuit diagram of  FIG. 12 ), and the difference  141  between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may be V Diode -dominant (e.g., as shown in the plot of  FIG. 13 ). This way, taking the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118  may provide an accurate estimation of the diode voltage V Diode    136 . 
     In process block  234 , multiple temperatures are applied to the pixel  64 . In particular, any suitable temperatures may be applied to generate an accurate relationship or curve between changes in diode voltage per temperature and diode luminance or current (as shown in the example curves  170 ,  172 ,  174 ,  210 ,  212 ,  214  in the plots of  FIGS. 15 and 17 ). For example, at the manufacturing facility or assembly plant at which the display  18  is made or assembled, multiple different temperatures may be applied to the display  18  and/or pixel  64 . 
     In process block  236 , for each temperature applied to the pixel  64 , the driver-integrated circuit  60  determines a diode voltages V Diode    136  that generate target diode currents or luminances based on the difference between the positive supply voltage V DD    120  and the negative supply voltage V SS    118 . That is, for a target diode current or luminance, and for an applied temperature, the driver-integrated circuit  60  determines the diode voltage V Diode    136  that generates the diode current or luminance at the diode  116 . 
     In process block  238 , the driver-integrated circuit  60  generates a lookup table based on the temperatures, the diode voltages, and the target diode currents or luminances. For example, for cases where the compensation is performed internally, the driver-integrated circuit  60  may generate the lookup table  150  (e.g., as illustrated in  FIG. 14 ) to express change in diode voltage per temperature varying by diode luminance. As such, the lookup table  150  may be based on generated, interpolated, and/or extrapolated curves or relationships that associate change in diode voltage per temperature to diode luminance, such as those illustrated in the plot of  FIG. 15 . For cases where the compensation is performed externally, the processor core complex  12  may generate the lookup table  190  (e.g., as illustrated in  FIG. 16 ) to express change in diode voltage per temperature varying by diode current. As such, the lookup table  190  may be based on generated, interpolated, and/or extrapolated curves or relationships that associate change in diode voltage per temperature to diode current, such as those illustrated in the plot of  FIG. 17 . 
     In process block  240 , the driver-integrated circuit  60  receives a target diode current or luminance and a temperature at the pixel  64 . The target diode luminance  154  may be a luminance that is desired to be emitted by the diode  116  such that image data  54  is properly displayed by the pixel  64  (and thus the display  18 ). As such, for cases where the compensation is performed internally, as shown in  FIG. 14 , the driver-integrated circuit  60  may receive the target diode luminance  154 , and receive a temperature at the pixel  64  via a virtual temperature map  158 . The virtual temperature map  158  may store temperature values received from, for example, thermal sensors in the display  18 , that correspond to individual pixels  64  or regions (e.g., of pixels  64 ) of the display  18 . 
     Similarly, the target diode current  192  may be a current that is desired to be supplied to the diode  116  that causes the diode  116  to emit a luminance such that image data  54  is properly displayed by the pixel  64  (and thus the display  18 ). As such, for cases where the compensation is performed externally, as shown in  FIG. 16 , the processor core complex  12  may receive the target diode current  192 , and receive a temperature at the pixel  64  via a sensed temperature map  194 . The sensed temperature map  194  may store temperature values received or derived from, for example, current or voltage values determined via current or voltage sensors in the display  18 . 
     In process block  242 , the driver-integrated circuit  60  determines a correction voltage based on the target diode current or luminance, the temperature, and the lookup table. For example, as shown in  FIGS. 14 and 16 , the driver-integrated circuit  60  may multiply the diode voltage per temperature  156  by the temperature to determine the correction voltage  152 . In some embodiments, the driver-integrated circuit  60  may receive or determine a coupling efficiency  160  that represents a relationship or proportion of the parasitic capacitance C G    132  at the gate of the driver TFT  112  to the storage capacitance C ST  of the storage capacitor  114 . As such, the driver-integrated circuit  60  may multiply the diode voltage per temperature  156 , the temperature, and the coupling efficiency to determine the correction voltage  152 . 
     In process block  244 , the driver-integrated circuit  60  decreases the negative supply voltage V SS    118  to place the driver TFT  188  of a pixel  64  in the active or saturation region. As a result, the driver TFT  188  may act as a current source  134  (e.g., as shown in the circuit diagram of  FIG. 10 ), and be operated to control magnitude of supply current flowing through the diode  116  to cause the diode  116  to emit light at a desired or target luminance. 
     In process block  246 , the driver-integrated circuit  60  applies the data voltage corresponding to the target diode current or luminance and the correction voltage to the driver TFT  112 . In particular, the data voltage may be predetermined (e.g., at an initial time and/or temperature, such as at the manufacturing facility or assembly plant at which the display  18  is made or assembled) as a voltage that causes the target diode current or luminance at the diode  116 . In some embodiments, the data voltage may be stored in a lookup table with other data voltages that cause other target diode current or luminance at the diode  116 . For example,  FIGS. 14 and 16  illustrate the correction voltage  152  output from the driver-integrated circuit  60  or the image data generation and processing circuitry  80 , respectively. In this manner, the process  230  may compensate for temperature-based parasitic capacitance variation in the display  18 . 
     As an illustrative example,  FIG. 19  is a circuit diagram of a portion of the pixel  64  with the correction voltage  152  being applied, according to embodiments of the present disclosure. That is, to properly display image data  54  on the display  18 , the driver-integrated circuit  60  may apply both the data voltage V data    260  and the correction voltage  152  to the gate of the driver TFT  112  of the pixel  64 . The data voltage V data    260  may be the predetermined voltage that causes the target diode current or luminance at the diode  116 . Because temperature-based parasitic capacitance variation at the gate of the driver TFT  112  may cause a loss of data voltage during emission, the correction voltage  152  may be applied (e.g., added to) the data voltage V data    260  to compensate for the loss of data voltage, thus causing the target diode current to be supplied or the target diode luminance to be emitted at the diode  116 . 
     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. 
     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: 20200609
Publication Date: 20220322
Grant Date: 20220322
Priority Date: 20190610
Inventors: KIM, HYUNSOO
HWANG, INJAE
KIM, JESUN
RICHMOND, Jesse A.
TAN, JUNHUA
RYU, JIE WON
NHO, HYUNWOO
BRAHMA, KINGSUK
WANG, CHAOHAO
SHEN, Shiping
CHOI, MYUNGJOON
CHO, Myung-Je
PARK, REBECCA
CHANG, SUN-IL
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3655", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0852", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0223", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3233", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0861", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3258", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2300/0819", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3258", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0223", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3655", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 73650726