Display device

Abstract

A display device is disclosed. The display device includes: a first pixel connected to a first data line, a first scan line, and a first power supply line, emitting light in a first period and not emitting light in a second period after the first period; a second pixel connected to a second data line, the first scan line, and the first power supply line, not emitting light in the first period and emitting light in the second period; a current sensor sensing a current flowing through the first power supply line in the first period to provide a first sensed current value and sensing a current flowing through the first power supply line in the second period to provide a second sensed current value; and a memory storing a first block of target current values corresponding to the first sensed current value and a second block of target current values corresponding to the second sensed current value.

Description

[0001] This application claims the priority and benefit of Korean Patent Application No. 10-2019-0082651, filed on Jul. 9, 2019, which is hereby incorporated by reference in its entirety for all purposes as if fully set forth herein. Technical Field

[0002] Exemplary embodiments relate to a display device and a driving method thereof. Background Art

[0003] With the development of information technology, the importance of a display device as a connection medium between a user and information has been emphasized. In view of this, the use of display devices such as liquid crystal display devices, organic light emitting display devices, and plasma display devices has been increasing.

[0004] A display device may include pixels, and an image frame displayed by the pixels may have different load values. That is, an image frame corresponding to a bright image may have a large load value, and an image frame corresponding to a dark image may have a small load value.

[0005] As the load value increases, the amount of current required by the pixels increases. If the current supplied to the pixels is insufficient, the brightness of the image frame displayed by the pixels is lower than the target brightness.

[0006] As the load value decreases, the amount of current required by the pixels decreases. If the current supplied to the pixels is excessive, the brightness of the image frame displayed by the pixels is higher than the target brightness, and power is unnecessarily consumed.

[0007] Therefore, it is important to supply an appropriate current to the pixels in response to the load value of the image frame. However, due to process variations of the pixels, the luminous efficiency of the pixels may be different for each display region. The luminous efficiency of the pixels may represent the luminous brightness of the pixels compared to the current supplied to the pixels. Therefore, it is difficult to select an appropriate current to be supplied to the pixels corresponding to the load value of the image frame. Summary of the Invention

[0008] An object of the inventive concept is to provide a display device and a driving method capable of supplying an appropriate current to pixels having different luminous efficiencies in response to the load value of an image frame.

[0009] According to some exemplary embodiments, a display device may include: a first pixel connected to a first data line, a first scan line, and a first power line, emitting light in a first period and not emitting light in a second period after the first period; a second pixel connected to a second data line, the first scan line, and the first power line, not emitting light in the first period and emitting light in the second period; a current sensor sensing a current flowing through the first power line in the first period to generate a first sensed current value and sensing a current flowing through the first power line in the second period to generate a second sensed current value; and a memory storing a first block target current value corresponding to the first sensed current value and a second block target current value corresponding to the second sensed current value.

[0010] The display device may further include: a block target current value generator generating a representative value of the first sensed current values provided multiple times in the first period as the first block target current value and generating a representative value of the second sensed current values provided multiple times in the second period as the second block target current value.

[0011] The display device may further include: a target current distribution generator generating a target current distribution corresponding to a histogram including the first block target current value and the second block target current value.

[0012] The display device may further include: a unit target current value generator determining a target current waveform based on the target current distribution and generating a unit target current value that is an instantaneous value of the target current waveform.

[0013] The display device may further include: a scale factor generator generating a target current value using the unit target current value and a frame load value corresponding to the unit target current value and generating a scale factor based on a difference between the sensed current value provided by the current sensor and the target current value.

[0014] The display device may further include: a timing controller scaling a first gray value for the first pixel and a second gray value for the second pixel using the scale factor.

[0015] The display device may further include: a data driver applying a first data voltage corresponding to the scaled first gray value to the first data line and applying a second data voltage corresponding to the scaled second gray value to the second data line.

[0016] According to some exemplary embodiments, a display device may include: a first pixel connected to a first data line, a first scan line, and a first power line; a second pixel connected to a second data line, the first scan line, and the first power line; a current sensor configured to sense a current flowing through the first power line to generate a sensed current value; a timing controller configured to scale a first gray value for the first pixel and a second gray value for the second pixel based on a gray value of a frame and the sensed current value; and a data driver configured to apply a first data voltage corresponding to the scaled first gray value to the first data line and apply a second data voltage corresponding to the scaled second gray value to the second data line, wherein the sensed current value, the first data voltage, and the second data voltage may change even if the gray value remains the same in consecutive frames.

[0017] The first pixel may emit light during a first period and not emit light during a second period after the first period. The second pixel may not emit light during the first period and emit light during the second period. The current sensor may sense the current flowing through the first power line during the first period to generate a first sensed current value and sense the current flowing through the first power line during the second period to generate a second sensed current value.

[0018] The display device may further include: a block target current value generator configured to generate a representative value of the first sensed current values provided multiple times during the first period as a first block target current value and generate a representative value of the second sensed current values provided multiple times during the second period as a second block target current value.

[0019] The display device may further include: a memory configured to store the first block target current value and the second block target current value.

[0020] The display device may further include: a target current distribution generator configured to generate a target current distribution corresponding to a histogram including the first block target current value and the second block target current value.

[0021] The display device may further include: a unit target current value generator configured to determine a target current waveform based on the target current distribution provided by the target current distribution generator and generate a unit target current value that is an instantaneous value of the target current waveform.

[0022] The display device may further include: a scale factor generator configured to generate a target current value using the unit target current value and a frame load value corresponding to the unit target current value and generate a scale factor based on a difference between the sensed current value provided by the current sensor and the target current value. The frame load value may correspond to the gray value of the frame.

[0023] According to some exemplary embodiments, a method for driving a display device may include: in a first period, causing a first pixel connected to a first data line, a first scan line, and a first power line to emit light, and not causing a second pixel connected to a second data line, the first scan line, and the first power line to emit light; sensing, by a current sensor, a current flowing through the first power line to provide a first sensed current value; storing, by a memory, a first block target current value corresponding to the first sensed current value; in a second period, causing the second pixel to emit light and not causing the first pixel to emit light; in the second period, sensing, by the current sensor, a current flowing through the first power line to generate a second sensed current value; and storing, by the memory, a second block target current value corresponding to the second sensed current value.

[0024] The driving method may further include: generating a representative value of the first sensed current values provided multiple times in the first period as the first block target current value; and generating a representative value of the second sensed current values provided multiple times in the second period as the second block target current value.

[0025] The driving method may further include generating a target current distribution corresponding to a histogram including the first block target current value and the second block target current value.

[0026] The driving method may further include determining a target current waveform based on the target current distribution, and generating a unit target current value that is an instantaneous value of the target current waveform.

[0027] The driving method may further include: generating a target current value using the unit target current value and a frame load value corresponding to the unit target current value; and generating a scaling factor based on a difference between the sensed current value provided by the current sensor and the target current value.

[0028] The driving method may further include: scaling a first gray value for the first pixel and a second gray value for the second pixel using the scaling factor; and applying a first data voltage corresponding to the scaled first gray value to the first data line, and applying a second data voltage corresponding to the scaled second gray value to the second data line.

[0029] According to some exemplary embodiments, a display device may include: a plurality of blocks, the plurality of blocks including at least a first block and a second block, the first block including a plurality of first pixels, the second block including a plurality of second pixels, the plurality of blocks being connected to a first power supply line; a current sensor connected to the first power supply line, the current sensor sensing a current flowing through the first power supply line during a first period when the plurality of first pixels in the first block emit light and the plurality of second pixels in the second block do not emit light, and a current flowing through the first power supply line during a second period when the plurality of second pixels in the second block emit light and the plurality of first pixels in the first block do not emit light; a scale factor provider connected to the current sensor and a timing controller, the scale factor provider including a memory that stores a first block target current value corresponding to the current flowing through the first power supply line during the first period and a second block target current value corresponding to the current flowing through the first power supply line during the second period.

[0030] The current sensor may sense the current flowing through the first power supply line at least twice respectively during the first period and the second period to generate a plurality of first sensed current values and a plurality of second sensed current values. The scale factor provider may further include a block target current value generator connected to the current sensor and generating a representative value of the plurality of first sensed current values as the first block target current value, and generating a representative value of the plurality of second sensed current values as the second block target current value.

[0031] The scale factor provider may further include a target current distribution generator connected to the memory and generating a target current distribution corresponding to a histogram including the first block target current value and the second block target current value.

[0032] The scale factor provider may further include a unit target current value generator connected to the target current distribution generator, determining a target current waveform based on the target current distribution, and generating a unit target current value as an instantaneous value of the target current waveform.

[0033] The scale factor provider may further include a scale factor generator connected to the unit target current value generator and using the unit target current value and a frame load value corresponding to the unit target current value to generate a target current value, and generating a scale factor according to a difference between the sensed current value provided by the current sensor and the target current value.

[0034] The timing controller may use the scale factor to scale a first gray value for the plurality of first pixels and a second gray value for the plurality of second pixels.

[0035] The scaling factor provider may further include a data driver that is connected to the plurality of blocks and applies a first data voltage corresponding to the scaled first gray value to the plurality of first pixels and applies a second data voltage corresponding to the scaled second gray value to the plurality of second pixels. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings illustrate exemplary embodiments of the inventive concept and are used in connection with the description to explain the principles of the inventive concept. The drawings are included to provide a further understanding of the inventive concept and are incorporated in and constitute a part of this specification.

[0037] Figure 1 is a block diagram of a display device showing an embodiment according to the inventive concept.

[0038] Figure 2 is a circuit diagram of a pixel showing an embodiment according to the inventive concept.

[0039] Figure 3 is a diagram of a pixel unit showing an embodiment according to the inventive concept.

[0040] Figure 4 is a diagram for explaining a problem that occurs when a target current value is set based on a specific block of a pixel unit.

[0041] Figure 5 、 Figure 6 and Figure 7 are graphs for explaining a problem that occurs when a target current value is set based on a specific block of a pixel unit.

[0042] Figure 8 is a block diagram of a scaling factor provider showing an embodiment according to the inventive concept.

[0043] Figure 9 is a diagram of a block target current value generator and a memory showing an embodiment according to the inventive concept.

[0044] Figure 10 、 Figure 11 、 Figure 12 and Figure 13 are graphs for explaining a target current distribution generator according to an embodiment of the inventive concept.

[0045] Figure 14 、 Figure 15 、 Figure 16 and Figure 17 are graphs for explaining a unit target current value generator according to an embodiment of the inventive concept. DETAILED DESCRIPTION

[0046] Hereinafter, preferred embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. The following embodiments are provided so that those skilled in the art will be able to fully understand and implement the inventive concept. The embodiments can be modified in various ways. The scope of the inventive concept is not limited to the embodiments described below.

[0047] To clearly describe the inventive concept, parts irrelevant to the description are omitted. Throughout the specification, the same reference numerals denote the same elements. Accordingly, the foregoing reference numerals may be used in other drawings.

[0048] In addition, for ease of description, the dimensions and thicknesses of each component shown in the drawings are arbitrarily shown. The inventive concept is not necessarily limited to what is shown. In the drawings, to be clear, when expressing layers and regions, the thickness may be exaggerated.

[0049] Figure 1 is a block diagram showing a display device according to an embodiment of the inventive concept.

[0050] Referring to Figure 1 , a display device 10 according to an embodiment of the inventive concept may include a timing controller 11, a data driver 12, a scan driver 13, a pixel unit 14, a current sensor 15, and a scaling factor provider 16.

[0051] The timing controller 11 may receive grayscale values and control signals for each frame from an external processor. The timing controller 11 may render the grayscale values to correspond to the specifications of the display device 10. For example, the external processor may provide a red grayscale value, a green grayscale value, and a blue grayscale value for each unit point. However, for example, when the pixel unit 14 has a pentile structure, since adjacent unit points share pixels, the pixels may not correspond one-to-one with the grayscale values. In this case, it may be necessary to render the grayscale values. When the pixels correspond one-to-one with the grayscale values, rendering the grayscale values may not be required. The rendered or unrendered grayscale values may be provided to the data driver 12. At this time, the grayscale values provided to the data driver 12 may be in a scaled state by a scaling factor provided by the scaling factor provider 16. In addition, the timing controller 11 may provide control signals suitable for respective specifications to the data driver 12, the scan driver 13, etc. for displaying a frame.

[0052] The data driver 12 may generate data voltages to be provided to data lines D1, D2, D3, …, Dj, D(j + 1), ……, and Dn using the grayscale values and the control signals. For example, the data driver 12 may sample the grayscale values using a clock signal and apply data voltages corresponding to the grayscale values to the data lines D1 to Dn in units of pixel rows (e.g., a group of pixels connected to the same scan line), where n and j may be integers greater than zero.

[0053] The scan driver 13 may receive a clock signal, a scan start signal, etc. from the timing controller 11, and generate scan signals to be provided to scan lines S1, S2, S3, ……, Si, S(i + 1), ……, and Sm, where m and i may be integers greater than zero.

[0054] The scan driver 13 may sequentially supply scan signals having pulses of an on level to the scan lines S1 to Sm. The scan driver 13 may include scan stages including shift registers. The scan driver 13 may generate scan signals by sequentially transferring a scan start signal in the form of a pulse having an on level to the next scan stage under the control of the clock signal.

[0055] The pixel unit 14 may include pixels PXij, PXi(j + 1), and PX(i + 1)j. Each of the pixels PXij, PXi(j + 1), and PX(i + 1)j may be connected to a corresponding data line and a corresponding scan line. In the pixel PXij, a scan transistor may be connected to the i-th scan line Si and the j-th data line Dj. In the pixel PXi(j + 1), the scan transistor may be connected to the i-th scan line Si and the (j + 1)-th data line D(j + 1). In the pixel PX(i + 1)j, the scan transistor may be connected to the (i + 1)-th scan line S(i + 1) and the j-th data line Dj. The pixels PXij, PXi(j + 1), and PX(i + 1)j may be commonly connected to a first power line ELVDDL. At this time, the pixels PXij, PXi(j + 1), and PX(i + 1)j may be commonly connected to a second power line ELVSSL. In another embodiment, the pixels PXij, PXi(j + 1), and PX(i + 1)j may be connected to different second power lines. That is, different second power supply voltages may be applied to the pixels PXij, PXi(j + 1), and PX(i + 1)j.

[0056] According to another embodiment, the pixels PXij, PXi(j + 1), and PX(i + 1)j may be commonly connected to the second power line ELVSSL, and the pixels PXij, PXi(j + 1), and PX(i + 1)j may be connected to different first power lines. In this case, different from the Figure 1 embodiment, the current sensor 15 may be connected to the second power line ELVSSL to sense the current flowing through the second power line ELVSSL.

[0057] The pixel unit 14 may include a plurality of blocks BLK1 and BLK2. Each of the blocks BLK1 and BLK2 may include at least one pixel. For example, the first block BLK1 may include pixels PXij and PX(i + 1)jj, and the second block BLK2 may include the pixel PXi(j + 1).

[0058] The current sensor 15 may be connected to the first power supply line ELVDDL. In this case, the current sensor 15 may sense the current flowing through the first power supply line ELVDDL to provide the sensed current value to the scale factor provider 16. As described above, in another embodiment, the current sensor 15 may be connected to the second power supply line ELVSSL that is commonly connected to the pixels PXij, PXi(j + 1), and PX(i + 1)j. At this time, the current sensor 15 may sense the current flowing through the second power supply line ELVSSL to provide the sensed current value to the scale factor provider 16. Since the current sensor 15 is connected to the common power supply line of all the pixels in the pixel unit 14, even if only one current sensor is provided, embodiments of the inventive concept can be implemented.

[0059] The display device 10 may emit light sequentially through the blocks BLK1 and BLK2, and the current sensor 15 may provide the sensed current value to the scale factor provider 16 at each time point. In this case, the block target current values corresponding to the sensed current values may be sequentially stored in the memory. For example, the pixels PXij and PX(i + 1)j of the first block BLK1 may emit light in the first period and may not emit light in the second period after the first period. The pixel PXi(j + 1) of the second block BLK2 may not emit light in the first period and may emit light in the second period. The current sensor 15 may sense the current flowing through the first power supply line ELVDDL in the first period to provide the first sensed current value to the scale factor provider 16, and may sense the current flowing through the first power supply line ELVDDL in the second period to provide the second sensed current value to the scale factor provider 16. The memory may store the first block target current value corresponding to the first sensed current value and store the second block target current value corresponding to the second sensed current value.

[0060] The process of storing the block target current value may be executed once when the display device 10 is turned on. In other embodiments, the time point at which this process is executed may be set differently and may be executed multiple times.

[0061] The scale factor provider 16 may be connected to the current sensor 15 and the timing controller 11. The scale factor provider 16 may compare the sensed current value provided by the current sensor 15 with the target current value to provide a scale factor. The target current value may be generated using the above-described block target current value and the frame load value.

[0062] In this case, the timing controller 11 may scale the grayscale values of the pixels PXij, PXi(j + 1), and PX(i + 1)j using a scaling factor. The scaling factor may be commonly applied to all the pixels of the pixel unit 14. In another embodiment, the scaling factor may be applied to some of the pixels in the pixel unit 14. For example, the timing controller 11 may scale the grayscale value of the pixel PXij and the grayscale value of the pixel PXi(j + 1) using the scaling factor. That is, the timing controller 11 may scale the grayscale value of the pixel Pxij and the grayscale value of the pixel PXi(j + 1) based on the grayscale value of the frame and the sensed current value.

[0063] In this case, the data driver 12 may apply data voltages corresponding to the scaled grayscale values to the data lines D1 to Dn. For example, the data driver 12 may apply the data voltage corresponding to the scaled grayscale value of the pixel PXij to the j-th data line Dj, and apply the data voltage corresponding to the scaled grayscale value of the pixel PXi(j + 1) to the (j + 1)-th data line D(j + 1).

[0064] Figure 2 is a circuit diagram of a pixel showing an embodiment according to the inventive concept.

[0065] Referring to Figure 2 , the pixel PXij may include transistors T1 and T2, a storage capacitor Cst, and a light-emitting diode LD.

[0066] Hereinafter, a circuit including an N-type transistor will be described as an example. However, those skilled in the art will be able to design a circuit including a P-type transistor. When a P-type transistor is used, the polarity of the voltage applied to the gate electrode may be different from the polarity when an N-type transistor is used. Similarly, those of ordinary skill in the art will be able to design a circuit including a combination of a P-type transistor and an N-type transistor. A P-type transistor is a superordinate concept of a transistor in which the amount of current to be conducted increases when the voltage difference between the gate electrode and the source electrode increases in the negative direction. An N-type transistor is a superordinate concept of a transistor in which the amount of current to be conducted increases when the voltage difference between the gate electrode and the source electrode increases in the positive direction. The transistor may be configured in various forms, such as a thin-film transistor (TFT), a field-effect transistor (FET), and a bipolar junction transistor (BJT).

[0067] The first transistor T1 may include a gate electrode connected to the first electrode of the storage capacitor Cst, a first electrode connected to the first power line ELVDDL, and a second electrode connected to the second electrode of the storage capacitor Cst. The first transistor T1 may be referred to as a driving transistor.

[0068] The second transistor T2 may include a gate electrode connected to the i-th scan line Si, a first electrode connected to the j-th data line Dj, and a second electrode connected to the gate electrode of the first transistor T1. The second transistor T2 may be referred to as a scan transistor.

[0069] The light-emitting diode LD may include an anode connected to the second electrode of the first transistor T1 and a cathode connected to the second power supply line ELVSSL. The light-emitting diode LD may be an organic light-emitting diode, an inorganic light-emitting diode, a quantum dot light-emitting diode, or the like. In another embodiment, the anode of the light-emitting diode LD may be connected to the first power supply line ELVDDL, and the cathode may be connected to the first electrode of the first transistor T1.

[0070] A first power supply voltage may be applied to the first power supply line ELVDDL, and a second power supply voltage may be applied to the second power supply line ELVSSL. For example, the first power supply voltage may be greater than the second power supply voltage.

[0071] When a scan signal having a conductive level (here, a logic high level) is applied through the scan line Si, the second transistor T2 may be turned on. At this time, the data voltage applied to the data line Dj may be stored in the storage capacitor Cst.

[0072] A positive drive current corresponding to the voltage difference between the first electrode and the second electrode of the storage capacitor Cst may flow between the first electrode and the second electrode of the first transistor T1. Accordingly, the light-emitting diode LD may emit light with a brightness corresponding to the data voltage. The sensed current value provided by the current sensor 15 may be the sum of the drive current values flowing through all the pixels in the pixel unit 14. Since the magnitude of the data voltage is adjusted by a scaling factor, the drive current value of the pixel may be adjusted.

[0073] Next, when a scan signal having a cut-off level (here, a logic low level) is applied through the scan line Si, the second transistor T2 may be turned off, and the data line Dj and the storage capacitor Cst may be electrically isolated. Accordingly, even if the data voltage of the data line Dj changes, the voltage stored in the first electrode of the storage capacitor Cst does not change.

[0074] Exemplarily shown is Figure 2 the pixel PXij, and embodiments of the inventive concept may be applied to pixel circuits having different configurations. For example, the pixel may also receive an emission control signal such that the emission period may be adjusted.

[0075] Figure 3 is a diagram showing a pixel unit according to an embodiment of the inventive concept.

[0076] Referring to Figure 3, the pixels of the pixel unit 14 can be divided into multiple blocks BLK11, BLK12, BLK13, BLK14, BLK15, BLK21, BLK22, BLK23, BLK24, BLK25, BLK31, BLK32, BLK33, BLK34, and BLK35. Each of the blocks BLK11 to BLK35 may include at least one pixel. The number of the blocks BLK11 to BLK35 may be equal to or less than the number of pixels.

[0077] For example, when the pixel unit 14 has a resolution of ultra high definition (UHD), the pixel unit 14 may include 3840×2160 pixels. For example, there may be 3840 pixels in a horizontal line. For example, 3840 pixels may be connected to a scanning line. For example, there may be 2160 pixels in a vertical line. For example, 2160 pixels may be connected to a data line.

[0078] For example, when the pixel unit 14 is divided into 100 blocks, each block may include the same number of pixels. For example, each block may include 384×216 pixels.

[0079] Figure 4 is a diagram for explaining problems that occur when a target current value is set based on a specific block of a pixel unit. Figures 5 to 7 is a graph for explaining problems that occur when a target current value is set based on a specific block of a pixel unit.

[0080] When the display device 10 is turned on, the pixels included in a specific block BLK23 of the pixel unit 14 may emit light with the highest gray level (e.g., white gray level), and the remaining blocks may not emit light (e.g., black gray level). The block BLK23 may be a block set at the center of the pixel unit 14.

[0081] In this case, the current sensor 15 may sense the current flowing through the first power supply line ELVDDL to provide a sensed current value SC. Assuming that there are 100 blocks as in the above example, the sensed current value SC may be the current value flowing through the pixels in the block BLK23, and the block BLK23 corresponds to 1% of the pixels in the pixel unit 14 of a full white image frame. The full white image frame may refer to an image frame in which all the pixels in the pixel unit 14 emit light with the highest gray level (white gray level). In Figures 4 to 7 In an embodiment, a unit target current value may be generated once when the display device 10 is turned on, and the unit target current value may be stored in a memory. The stored unit target current value may be used during the display period of an image frame of the display device 10. In Figures 4 to 7 In an embodiment, the unit target current value stored in the memory may not change with time during the display period. That is, in Figures 4 to 7In an embodiment, the unit target current value may be a single value.

[0082] For example, during a display period, the scale factor provider 16 may obtain a target current value TC of a corresponding image frame by multiplying the unit target current value by a frame load value FL. The frame load value may be determined corresponding to the grayscale value of the frame. For example, the larger the sum of the grayscale values of the frame, the larger the frame load value FL of the frame.

[0083] For example, the frame load value FL may be 100 in a completely white image frame, and the frame load value FL may be 0 in a completely black image frame. A completely black image frame may refer to an image frame in which all pixels in the pixel unit 14 are set to the lowest grayscale (black grayscale) and thus do not emit light. That is, the frame load value FL may have a value between 0 and 100.

[0084] The scale factor provider 16 may compare the sensed current value SC received from the current sensor 15 with the target current value TC to provide a scale factor. The scale factor provider 16 may provide a scale factor such that the grayscale value of the pixel is proportionally enlarged when the sensed current value SC is less than the target current value TC. The scale factor provider 16 may provide a scale factor such that the grayscale value of the pixel is proportionally reduced when the sensed current value SC is greater than the target current value TC. The above driving process may be referred to as global current management (GCM).

[0085] When all blocks BLK11 to BLK35 in the pixel unit 14 have the same luminous efficiency, global current management based on a specific block BLK23 may be appropriate. However, as described above, due to process variations during the manufacture of the display device 10, the luminous efficiencies of the blocks BLK11 to BLK35 may be different.

[0086] Refer to Figure 5 for an exemplary illustration of the luminous efficiencies of the blocks BLK11 to BLK35. Figure 5 The luminous efficiencies shown in represent the luminous intensity (unit: candela) per unit current (unit: ampere) required when each of the blocks BLK11 to BLK35 emits light at 500 nits. Since the above scale factor is determined based on the luminous efficiency of a specific block BLK23, it is appropriate only when the luminous efficiencies of all blocks BLK11 to BLK35 in the pixel unit 14 are equal to each other at 6.08 cd / A (represented by the horizontally extending dashed line). However, some blocks may have a lower luminous efficiency than the block BLK23. For example, the block BLK14 may have a luminous efficiency of 5.92 cd / A. Additionally, some blocks may have a higher luminous efficiency than the block BLK23. For example, the block BLK34 may have a luminous efficiency of 6.40 cd / A.

[0087] Refer to Figure 6, assume that the sensed current value SC is greater than the target current value TC at time point t0. In this case, a scaling factor will be provided to reduce the sensed current value SC. Since the target current value TC is set based on block BLK23, the sensed current value SC can converge to the target current value TC at time point t1. Therefore, at time point t1, the brightness L23 of block BLK23 can converge to the target brightness TL.

[0088] Since block BLK14 has a lower luminous efficiency than block BLK23, the brightness L14 of block BLK14 can be close to the target brightness TL at time point t0. However, due to the commonly applied scaling factor, the brightness L14 becomes less than the target brightness TL at time point t1. Additionally, when the frame load value remains the same after time point t1 (e.g., a still image), the insufficient brightness L14 of block BLK14 is maintained, causing the brightness non-uniformity of pixel unit 14 to be visually recognized by the user.

[0089] Refer to Figure 7 , when the sensed current value SC is less than the target current value TC at time point t0. In this case, a scaling factor will be provided to increase the sensed current value SC. Since the target current value TC is set based on a specific block BLK23, the sensed current value SC can converge to the target current value TC at time point t1. Therefore, at time point t1, the brightness L23 of block BLK23 can also converge to the target brightness TL.

[0090] Since block BLK34 has a higher luminous efficiency than block BLK23, the brightness L34 of block BLK34 can be close to the target brightness TL at time point t0. However, due to the commonly applied scaling factor, the brightness L34 becomes greater than the target brightness TL at time point t1. Additionally, when the frame load value remains the same after time point t1 (e.g., a still image), the excessive brightness L14 of block BLK34 is maintained, causing the brightness non-uniformity of pixel unit 14 to be visually recognized by the user.

[0091] Figure 8 is a block diagram showing a scaling factor provider according to an embodiment of the inventive concept. Figure 9 is a diagram showing a block target current value generator and a memory according to an embodiment of the inventive concept. Figures 10 to 13 is a graph for explaining a target current distribution generator according to an embodiment of the inventive concept. Figures 14 to 17 is a graph for explaining a unit target current value generator according to an embodiment of the inventive concept.

[0092] Refer to Figure 8, according to an embodiment of the inventive concept, the scaling factor provider 16 may include a block setting unit 161, a block target current value generator 162, a memory 163, a target current distribution generator 164, a unit target current value generator 165, and a scaling factor generator 166.

[0093] The scaling factor provider 16 may be an integrated circuit (IC) separate from the timing controller 11. At the same time, all or part of the scaling factor provider 16 may be integrated into the timing controller 11. On the other hand, all or part of the scaling factor provider 16 may be implemented in software in the timing controller 11.

[0094] The block setting unit 161 may be connected to the timing controller 11 and set blocks BLK11 to BLK35 such that each of the blocks BLK11 to BLK35 includes at least one pixel. The block setting unit 161 may provide a block setting unit value BLKI to the timing controller 11. The blocks BLK11 to BLK35 are set with reference to Figure 3 and examples of related descriptions. According to an embodiment, the block setting unit 161 may set the blocks to include different numbers of pixels. According to an embodiment, the block setting unit 161 may set the blocks such that adjacent blocks share at least one pixel. Additionally, the block setting unit 161 may set the blocks in various ways.

[0095] The block target current value generator 162 may be connected to the current sensor 15, the scaling factor generator 166, and the memory 163. The block target current value generator 162 may provide a representative value of the sensed current value SC provided from the current sensor 15 as a block target current value BTC to the memory 163. For example, the representative value may be an average value of the sensed current value SC provided from the current sensor 15 during a sensing period for each of the blocks BLK11 to BLK35. As another example, the representative value may be a weighted average value of the sensed current value SC. If the current sensor 15 provides the sensed current value SC only once during the sensing period of a block, the block target current value BTC of the block may be the same as the sensed current value SC.

[0096] With reference to Figure 9 , in a first period, the block BLK11 may emit light with maximum gray scale, and the remaining blocks may not emit light. In this case, the current sensor 15 may sense the current flowing through the first power supply line ELVDDL and provide the current flowing through the first power supply line ELVDDL as a first sensed current value to the block target current value generator 162. The block target current value generator 162 may provide a representative value of the first sensed current value provided multiple times during the first period as a first block target current value. The memory 163 may store the first block target current value.

[0097] In a second period after the first period, the block BLK12 can emit light at maximum gray level, and the remaining blocks can be non - emitting. In this case, the current sensor 15 can sense the current flowing through the first power supply line ELVDDL, and provide the current flowing through the first power supply line ELVDDL as a second sensed current value to the block target current value generator 162. The block target current value generator 162 can provide a representative value of the second sensed current values provided multiple times during the second period as the second block target current value. The memory 163 can store the second block target current value.

[0098] Similarly, the same steps as those in the first period and the second period are repeated to store the block target current values BTC of the blocks BLK11 to BLK35 in the memory 163. The emission order of the blocks BLK11 to BLK35 can be determined arbitrarily.

[0099] The storage process of the block target current value BTC can be executed once when the display device 10 is turned on. In other embodiments, the storage process can be executed at least twice, and the number of repetitions can be determined as needed.

[0100] The target current distribution generator 164 can be connected to the memory 163 and the unit target current value generator 165, and can generate a target current distribution TCPF corresponding to a histogram including the block target current value BTC.

[0101] Referring to Figure 10 , an exemplary target current distribution TCPF1 is shown. In the graph, the horizontal axis represents luminous efficiency (cd / A), and the vertical axis represents the number of blocks. Each interval 1U of the luminous efficiency can be arbitrarily determined within the range where the histogram has a significant shape.

[0102] Since the block target current value BTC is the sensed current value SC measured at the same brightness (e.g., maximum gray level), the block target current value BTC can be inversely proportional to the luminous efficiency. That is, the larger the block target current value BTC, the smaller the luminous efficiency. The weight applied when converting the block target current value BTC into luminous efficiency can be set in various methods according to the embodiments. Additionally, the luminous efficiency can be calculated using an appropriate conversion equation. Alternatively, the horizontal axis of the histogram can be the block target current value BTC.

[0103] Referring to Figure 11 , the target current distribution TCPF2 is a simplified graph of the target current distribution TCPF1. The target current distribution TCPF2 is a graph connecting the minimum value MIN of the luminous efficiency, the maximum value MAX of the luminous efficiency, and the maximum value TOP1 of the target current distribution TCPF1.

[0104] When using Figure 10When the target current distribution is TCPF1, the target current value TC suddenly changes. Therefore, the change in brightness can be visually recognized by the user (for example, recognized as flickering). Therefore, a target current distribution TCPF2 that reduces the gradient can be used by using some parameters of the target current distribution TCPF1.

[0105] Referring to Figure 12 , as an example, a target current distribution TCPF3 in which the minimum value MIN of the luminous efficiency, the maximum value MAX of the luminous efficiency, and the intermediate value MID of the luminous efficiency using the target current distribution TCPF1 are simplified to a triangular shape is shown. In this case, the maximum value TOP2 of the number of blocks can be the same as or different from the maximum value TOP1.

[0106] In addition, referring to Figure 13 , a target current distribution TCPF4 in which the minimum value MIN of the luminous efficiency, the maximum value MAX of the luminous efficiency, and the intermediate value MID of the luminous efficiency using the target current distribution TCPF1 are simplified to a semi-circular shape is shown.

[0107] In this way, the target current distribution generator 164 can generate the target current distribution TCPF in various ways.

[0108] The above operation of the target current distribution generator 164 can be executed once when the display device 10 is turned on or arbitrarily executed during the display period of the display device 10.

[0109] The unit target current value generator 165 can be connected to the target current distribution generator 164 and the scale factor generator 166, determine the target current waveforms WV1, WV2, and WV3 based on the target current distribution TCPF, and provide the unit target current value UTC as the instantaneous values of the target current waveforms WV1, WV2, and WV3 to the scale factor generator 166.

[0110] Referring to Figure 14 , as an example, Figure 10 the target current distribution TCPF1 is determined as the target current waveforms WV1, WV2, and WV3, and the unit target current values UCT1, UTC2, and UTC3 are sequentially provided at respective time points t11, t12, and t13.

[0111] Each of the target current waveforms WV1, WV2, and WV3 can be obtained by changing the unit of the horizontal axis of the target current distribution TCPF1 to time and changing the unit of the vertical axis to the current value. The weights according to the unit change can be set in various ways. The target current waveforms WV1, WV2, and WV3 can be continuous with each other.

[0112] The scale factor generator 166 can be connected to the current sensor 15, the block target current value generator 162, the unit target current value generator 165, and the timing controller 11, and uses the frame load value FL provided by the timing controller 11 and the unit target current value UTC provided by the unit target current value generator 165 to generate a target current value TC at the time point corresponding to the unit target current value UTC, and generates a scale factor SCF according to the difference between the sensed current value SC provided by the current sensor 15 and the target current value TC generated in the scale factor generator 166.

[0113] For example, the scale factor generator 166 can generate the target current value TC by multiplying the unit target current value UTC by the frame load value FL. At this time, any weight can be used. Refer to Figure 4 for an exemplary description of the unit target current value UTC and the frame load value FL. However, in this embodiment, the unit target current value UTC can be a value that changes over time rather than a fixed value (see Figure 14 ). The timing controller 11 can provide the frame load value FL generated by analyzing the gray value of the image frame.

[0114] The scale factor generator 166 can generate a scale factor SCF such that the gray value of the pixel becomes smaller when the sensed current value SC is greater than the target current value TC. Additionally, if the sensed current value SC is less than the target current value TC, the scale factor generator 166 can generate a scale factor SCF such that the gray value of the pixel becomes larger.

[0115] The timing controller 11 can use the scale factor SCF as shown in Equation 1 below.

[0116] Equation 1

[0117] OUTG = ING × SCF / GR

[0118] Here, OUTG can be the output gray value, ING can be the input gray value, SCF can be the scale factor SCF, and GR can be the gray resolution.

[0119] The input gray value can be the gray value input from an external processor to the timing controller 11, and the output gray value can be the gray value provided by the timing controller 11 to the data driver 12.

[0120] For example, when each grayscale value is represented by 10 bits, the grayscale resolution can be 1024. At this time, each of the input grayscale value ING and the output grayscale value OUTG can have a value ranging from 0 to 1023. When each grayscale value is represented by 8 bits, the grayscale resolution can be 256. At this time, the input grayscale value ING and the output grayscale value OUTG can have values in the range from 0 to 255. The output grayscale value OUTG falling outside this range can be set to the maximum value of this range.

[0121] The magnitude of the scale factor SCF can be proportional to the difference between the sensed current value SC and the target current value TC. For example, if the sensed current value SC is greater than the target current value TC, the scale factor generator 166 can generate a scale factor SCF smaller than the grayscale resolution. Additionally, if the sensed current value SC is less than the target current value TC, the scale factor generator 166 can generate a scale factor SCF greater than the grayscale resolution.

[0122] Refer to Figure 15 , the target current values TC generated based on Figure 14 the target current waveforms WV1, WV2, and WV3 are shown. For ease of explanation, it is assumed that the frame load value FL is constant (e.g., a still image). Therefore, Figure 15 the waveform of the target current value TC can be similar to Figure 14 the target current waveforms WV1, WV2, and WV3.

[0123] Since the target current value TC changes over time, the scale factor SCF also changes over time. The waveform of the sensed current value SC has a shape such that the waveform follows the waveform of the target current value TC. Therefore, the waveform of the sensed current value SC can be similar to the waveform of the target current value TC. In this case, the amplitude of the waveform of the sensed current value SC can be smaller than the amplitude of the waveform of the target current value TC. Additionally, the slope of the waveform of the sensed current value SC can be gentler than the slope of the waveform of the target current value TC. This means that even with Figure 10 the unsimplified target current distribution TCPF1, sudden brightness changes can be alleviated to a certain extent.

[0124] Since it is assumed that the image is a still image, the target brightness TL can be constant over time. The brightness L23 of block BLK23, the brightness L14 of block BLK14, and the brightness L34 of block BLK34 all change smoothly around the target brightness TL. Therefore, different from Figure 6 and Figure 7 , since each of blocks BLK11 to BLK35 emits light with a brightness similar to the brightness of the target brightness TL, the brightness non-uniformity phenomenon can be alleviated despite the process variations of the pixels in pixel unit 14.

[0125] According to an embodiment, even if the gray value remains the same in consecutive frames (i.e., in the case of a still image), the sensed current value SC and the data voltage of the pixels included in blocks BLK11 to BLK35 may change. The change in the data voltage of the pixels can be seen through Figure 15 the waveforms of the luminances L14, L23, and L34. The waveforms of the luminances L14, L23, and L34 and the waveform of the data voltage of the pixels may have substantially the same pattern.

[0126] The sensed current value SC and the data voltage may change in substantially the same pattern. For example, the sensed current value SC and the data voltage may change in the same period. For example, the sensed current value SC and the data voltage may change simultaneously in the same increasing and decreasing directions.

[0127] The unit target current value generator 165 may set the target current waveforms WV1, WV2', and WV3 based on the target current distribution TCPF such that at least two of the target current waveforms WV1, WV2', and WV3 are different from each other. Referring to Figure 16 , the target current waveforms WV1, WV2', and WV3 have been set such that the non-inverted target current waveforms WV1 and WV3 and the inverted target current waveform WV2' repeat over time. According to this embodiment, it is possible to prevent an undesired display pattern caused by the regularity over time from being recognized by the user.

[0128] The unit target current value generator 165 may set the frequencies of the target current waveforms WV1", WV2", and WV3" differently. For example, Figure 17 the frequencies of the target current waveforms WV1", WV2", and WV3" in Figure 14 may be higher than the frequencies of the target current waveforms WV1, WV2, and WV3 in Figure 17 . That is, Figure 14 the periods P1", P2", and P3" in Figure 14 may be shorter than the periods P1, P2, and P3 in

[0129] Alternatively, the frequencies of the target current waveforms may be set to be lower than the frequencies of the target current waveforms WV1, WV2, and WV3 in

[0130] The above operations of the unit target current value generator 165 and the scale factor generator 166 may be continuously performed during the display period of an image frame of the display device 10.

[0131] As described above, the preferred embodiments of the inventive concept have been disclosed through the detailed description and the accompanying drawings. It will be understood that the terms used herein are for the purpose of describing the inventive concept only and are not intended to limit the scope of the inventive concept described in the claims. Thus, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the inventive concept. Therefore, the true scope of the inventive concept should be determined by the technical concept of the appended claims.

Claims

1. A display device, the display device comprising: A first pixel, connected to a first data line, a first scan line, and a first power line, emitting light in a first period and not emitting light in a second period after the first period; A second pixel, connected to a second data line, the first scan line, and the first power line, not emitting light in the first period and emitting light in the second period; A current sensor, sensing a current flowing through the first power line in the first period to generate a first sensed current value, and sensing a current flowing through the first power line in the second period to generate a second sensed current value; A memory, storing a first block target current value corresponding to the first sensed current value and a second block target current value corresponding to the second sensed current value; A target current distribution generator, generating a target current distribution corresponding to a histogram including the first block target current value and the second block target current value; A unit target current value generator, determining a target current waveform based on the target current distribution, and generating a unit target current value that is an instantaneous value of the target current waveform; A scale factor generator, generating a target current value using the unit target current value and a frame load value corresponding to the unit target current value, and generating a scale factor according to a difference between the sensed current value provided by the current sensor and the target current value; And A timing controller, scaling a first gray value for the first pixel and a second gray value for the second pixel using the scale factor.

2. The display device according to claim 1, the display device further comprising: A block target current value generator, generating a representative value of a plurality of the first sensed current values as the first block target current value, and generating a representative value of a plurality of the second sensed current values as the second block target current value.

3. The display device according to claim 1, the display device further comprising: A data driver, applying a first data voltage corresponding to the scaled first gray value to the first data line, and applying a second data voltage corresponding to the scaled second gray value to the second data line.

4. A display device, the display device comprising: A first pixel, connected to a first data line, a first scan line, and a first power line; A second pixel, connected to a second data line, the first scan line, and the first power line; A current sensor, sensing a current flowing through the first power line to generate a sensed current value; A timing controller, scaling a first gray value for the first pixel and a second gray value for the second pixel based on a gray value of a frame and the sensed current value; And A data driver, applying a first data voltage corresponding to the scaled first gray value to the first data line, and applying a second data voltage corresponding to the scaled second gray value to the second data line, wherein, even if the gray value remains the same in consecutive frames, the sensed current value, the first data voltage, and the second data voltage change. Among them, the first pixel emits light in the first period and does not emit light in the second period after the first period. Among them, the second pixel does not emit light in the first period and emits light in the second period. Among them, the current sensor senses the current flowing through the first power line in the first period to generate a first sensed current value, and senses the current flowing through the first power line in the second period to generate a second sensed current value, and Among them, the display device further includes: a block target current value generator that generates a representative value of the plurality of first sensed current values as a first block target current value, and generates a representative value of the plurality of second sensed current values as a second block target current value; a memory that stores the first block target current value and the second block target current value; a target current distribution generator that generates a target current distribution corresponding to a histogram including the first block target current value and the second block target current value; a unit target current value generator that determines a target current waveform based on the target current distribution provided by the target current distribution generator, and generates a unit target current value that is an instantaneous value of the target current waveform; and a scale factor generator that generates a target current value using the unit target current value and a frame load value corresponding to the unit target current value, and generates a scale factor based on the difference between the sensed current value provided by the current sensor and the target current value, wherein the frame load value corresponds to the gray value of the frame.

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