Display device

Abstract

A display device includes a pixel section that displays an image and includes a plurality of pixels that receive a reference voltage, a control section that decides a value of the reference voltage for suppressing a leakage current of the plurality of pixels based on a load of the entire pixel section, and controls a grayscale range of image data based on a position within the pixel section based on the reference voltage, a data drive section that supplies a data voltage to the pixel section through a plurality of data lines based on the grayscale range adjusted by the position, and a scan drive section that supplies a scan signal to the pixel section through a plurality of scan lines.

Description

TECHNICAL FIELD

[0001] The present application relates to a display device, and more particularly to a display device including low frequency driving. BACKGROUND

[0002] A display device displays an image on a display panel using a control signal applied from the outside.

[0003] A display device includes a plurality of pixels. Each pixel includes a plurality of transistors, a light emitting element electrically connected to the transistors, and a capacitor. Each transistor generates a driving current based on each signal supplied through a wire, and the light emitting element emits light in correspondence with the driving current.

[0004] In order to improve the driving efficiency of a display device, a display device with low power consumption is required. For example, when a still image is displayed, the driving frequency (or, data writing frequency) can be reduced to reduce the power consumption of the display device. However, due to the low driving frequency, flicker of the image or the like can be recognized. SUMMARY

[0005] An object of the present application is to provide a display device in which, when a still image is displayed by low frequency driving, a gradation range is gradually reduced with reference to a reference voltage as far as from a center portion of a pixel portion.

[0006] Another object of the present application is to provide a display device in which, when a still image is displayed by low frequency driving, a representative gradation of a histogram of a gradation of a peripheral region of a center portion of a pixel portion is shifted with reference to a gradation corresponding to a reference gradation.

[0007] However, the objects of the present application are not limited to the above-described objects, and various extensions can be made within the scope of the idea and the field of the present application.

[0008] To achieve an object of the present application, a display device according to an embodiment of the present application can include a pixel portion displaying an image and including a plurality of pixels receiving a reference voltage, a control portion deciding a value of the reference voltage for suppressing a leakage current of the plurality of pixels based on a load of the entire pixel portion, and controlling a gradation range of image data based on the position within the pixel portion based on the reference voltage, a data driving portion supplying a data voltage to the pixel portion through a plurality of data lines based on the gradation range adjusted by the position, and a scan driving portion supplying a scan signal to the pixel portion through a plurality of scan lines.

[0009] According to an embodiment, a difference between a maximum gray scale of image data corresponding to a second position of the pixel portion and a reference gray scale corresponding to the reference voltage can be smaller than a difference between a maximum gray scale of the image data corresponding to a first position of the pixel portion and the reference gray scale. A difference between a minimum gray scale of the image data corresponding to the second position and the reference gray scale can be smaller than a difference between a minimum gray scale of the image data corresponding to the first position and the reference gray scale. A distance from a center portion of the pixel portion to the second position can be larger than a distance from the center portion to the first position.

[0010] According to an embodiment, a voltage difference between a voltage of the maximum gray scale corresponding to the second position and a voltage of the minimum gray scale can be smaller than a voltage difference between a voltage of the maximum gray scale corresponding to the first position and a voltage of the minimum gray scale.

[0011] According to an embodiment, a gray scale range of image data corresponding to the second position can be smaller than a gray scale range of image data corresponding to the first position.

[0012] According to an embodiment, the greater the load, the more the control portion can decrease the reference voltage.

[0013] According to an embodiment, a voltage difference between a voltage of the maximum gray scale of the center portion and a voltage of the maximum gray scale of an outer portion of the pixel portion can be different from a voltage difference between a voltage of the minimum gray scale of the center portion and a voltage of the minimum gray scale of the outer portion.

[0014] According to an embodiment, the control portion can include a reference voltage decision portion that decides the reference voltage based on an On-pixel ratio (OPR) of the pixel portion, and a gray scale control portion that remaps a gray scale of the image data based on the reference voltage such that the farther from the center portion of the pixel portion, the smaller the width of the gray scale range.

[0015] According to an embodiment, a voltage of a maximum gray scale of a first region including the center portion can be smaller than a voltage of a maximum gray scale of a second region including an outer portion of the pixel portion, and a voltage of a minimum gray scale of the first region can be larger than a voltage of a minimum gray scale of the second region.

[0016] According to an embodiment, the gradation control section can determine a target maximum gradation and a target minimum gradation corresponding to an edge position region of the pixel section based on the reference voltage. The maximum gradation and the minimum gradation of the edge position region can gradually change in a predetermined period to reach the target maximum gradation and the target minimum gradation, respectively.

[0017] According to an embodiment, the display device can further include a region compensation section that performs region attenuation compensation that controls luminance according to a spatial position of the pixel based on the load.

[0018] According to an embodiment, the region compensation section can generate a region attenuation coefficient that is applied to the image data such that the luminance decreases as it moves away from the center section.

[0019] According to an embodiment, each of the pixels can include a light emitting element, a first transistor that controls a drive current based on a voltage of a first node and is connected between a second node and a third node, a second transistor that is connected between one of a plurality of data lines and the second node and is turned on according to a first scan signal supplied to a first scan line, a third transistor and a fourth transistor that are connected in series between the first node and the third node and are turned on according to a second scan signal supplied to a second scan line, and a fifth transistor that supplies the reference voltage to a fourth node between the third transistor and the fourth transistor and is turned off according to a light emission control signal supplied to a light emission control line.

[0020] According to an embodiment, each of the pixels can include a sixth transistor that is connected between a first power supply and the second node and is turned off according to the light emission control signal supplied to the light emission control line, a seventh transistor that is connected between the third node and the light emitting element and is turned off according to the light emission control signal supplied to the light emission control line, and an eighth transistor that supplies an initialization voltage to the third node and is turned on according to a third scan signal supplied to a third scan line.

[0021] According to an embodiment, the pixel can operate in one of a first mode in which the data voltage is written based on a first frequency and a second mode in which the data voltage is written based on a second frequency. The second frequency can be lower than the first frequency, and the control section can adjust the reference voltage and the gradation range in the second mode.

[0022] To achieve the object, the display device according to an embodiment of the present application includes: a pixel portion including a plurality of pixels arranged in a first region and a second region surrounding the first region; a control portion determining a value of a reference voltage supplied to the plurality of pixels in order to suppress a leakage current of the plurality of pixels based on a load of the entire pixel portion, and a reference gray scale corresponding to the reference voltage, and controlling a gray scale histogram of image data of the second region based on the reference gray scale; a data drive portion supplying a data voltage to the pixel portion through a plurality of data lines based on the image data; and a scan drive portion supplying a scan signal to the pixel portion through a plurality of scan lines.

[0023] According to an embodiment, the control portion can include: an image analysis portion determining an average value of a gray scale histogram of the entire pixel portion as the reference gray scale, and determining an average value of the gray scale histogram of the second region as a first representative gray scale; and a histogram shift portion shifting the gray scale histogram of the second region so that the first representative gray scale is shifted toward the reference gray scale.

[0024] According to an embodiment, the control portion can include: a distribution control portion reducing a gray scale histogram distribution of a first gray scale region exceeding a gray scale region to a preset first gray scale so that the gray scale region exceeding a gray scale region is represented in the shifted gray scale histogram.

[0025] According to an embodiment, the distribution control portion can expand a gray scale histogram distribution of a second gray scale region to a preset second gray scale so that a deficient gray scale region is represented in the shifted gray scale histogram. The first gray scale and the second gray scale can be one of a maximum gray scale and a minimum gray scale set in the control portion, respectively.

[0026] According to an embodiment, the pixel portion can further include a third region surrounding the second region. The control portion can shift a gray scale histogram of the third region so that a second representative gray scale, which is an average value of the gray scale histogram of the third region, is shifted toward the reference gray scale, and a gray scale difference between the shifted second representative gray scale and the reference gray scale is smaller than a gray scale difference between the shifted first representative gray scale and the reference gray scale.

[0027] According to an embodiment, each of the pixels can include a light emitting element, a first transistor that controls a drive current based on a voltage of a first node and connected between a second node and a third node, a second transistor connected between one of the plurality of data lines and the second node and turned on according to a first scan signal supplied to a first scan line, a third transistor and a fourth transistor connected in series between the first node and the third node and turned on according to a second scan signal supplied to a second scan line, and a fifth transistor that supplies the reference voltage to a fourth node between the third transistor and the fourth transistor and turned off according to a light emission control signal supplied to a light emission control line.

[0028] (EFFECT OF INVENTION)

[0029] The low-frequency-driven display device according to the embodiments of the present application can control, based on the reference voltage, the gray scale range (and the gray scale voltage range) to be narrower as it approaches the outer periphery of the pixel portion. Further, the low-frequency-driven display device according to the embodiments of the present application can correct the gray scale histogram and the representative gray scale of each of the respective regions to be closer to the reference gray scale as it approaches the outer periphery of the pixel portion.

[0030] Thus, the deviation between the gray scale voltage range of the image data corresponding to the outer periphery of the pixel portion and the reference voltage supplied to the pixel can be reduced. Therefore, the leakage current in the pixel in the outer periphery region of the pixel portion to which the region attenuation compensation is applied can be minimized, and flicker in the outer periphery portion of the pixel portion at the time of low-frequency driving for displaying a still image or the like can be reduced.

[0031] However, the effects of the present application are not limited to the above-mentioned objects, and various extensions can be made without departing from the scope of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a block diagram showing a display device according to the embodiments of the present application.

[0033] Figure 2 is a circuit diagram showing an example of a pixel included in the display device of Figure 1

[0034] Figure 3 is a timing chart showing an example of signals supplied to the pixel of Figure 2

[0035] Figure 4 is a diagram for explaining an example of correction of luminance by a region compensation portion included in the display device of Figure 1

[0036] Figure 5 is a block diagram showing a display device according to the embodiments of the present application. Figure 1 ​​​is a block diagram of an example of a control section included in a display device.

[0037] Figure 6 is a graph showing an example of a control section Figure 5 is a graph showing an example of a control section of a display device controlling a gray scale range.

[0038] Figure 7a and Figure 7b is a graph showing an example of a change in data voltage corresponding to a maximum gray scale and a minimum gray scale output by a control section Figure 5 of a display device.

[0039] Figure 8 is a graph showing another example of a change in data voltage corresponding to a maximum gray scale and a minimum gray scale output by a control section Figure 5 of a display device.

[0040] Figure 9 is a block diagram of another example of a control section included in a display device Figure 1 .

[0041] Figure 10a is a graph showing an example of a gray scale histogram of a first region of a pixel section.

[0042] Figure 10b is a graph showing an example of a shift in a gray scale histogram of a second region of a pixel section.

[0043] Figure 10c is a graph showing an example of a shift in a gray scale histogram of a third region of a pixel section.

[0044] Figure 11 is a graph showing an example of a gray scale histogram corrected by a control section Figure 9 of a display device. DETAILED DESCRIPTION

[0045] Hereinafter, preferred embodiments of the present application will be described in greater detail with reference to the accompanying drawings. Like reference numerals are used throughout the drawings and repeated descriptions are omitted for clarity.

[0046] Figure 1 is a block diagram of a display device to which each embodiment of the present application relates.

[0047] Referring to Figure 1 , the display device 1000 can include a pixel section 100, a scan driving section 200, a data driving section 300, and a control section 400. The display device 1000 can further include a region compensation section 500 and a power supply section 600.

[0048] The pixel section 100 can include scan lines SIl to Sin, S21 to S2n, S31 to S3n, light emission control lines El to En, and data lines Dl to Dm, and can include a plurality of pixels PX connected to the scan lines SIl to Sin, S21 to S2n, S31 to S3n, the light emission control lines El to En, and the data lines Dl to Dm (where m, n are integers greater than 1). Each pixel PX can include a drive transistor and a plurality of switching transistors. In low-frequency driving, in order to prevent a leakage current within each pixel PX, a reference voltage Vref can be supplied to the pixel PX.

[0049] The control section 400 can generate a first control signal SCS, a second control signal DCS, and a third control signal PCS in correspondence with a synchronization signal supplied from the outside. The first control signal SCS can be supplied to the scan driving section 200, the second control signal DCS can be supplied to the data driving section 300, and the third control signal PCS can be supplied to the power supply section 600. Further, the control section 400 can correct the image data IDATA supplied from the outside and supply the corrected image data CDATA to the data driving section 300. That is, the control section 400 can perform the function of a timing control section.

[0050] The control section 400 can determine the reference voltage Vref based on a load of the entire pixel section 100. For example, the control section 400 can supply reference data REF corresponding to the reference voltage Vref to the power supply section 600.

[0051] In one embodiment, the control section 400 can control a gray scale range (or, a gray scale expression range) of the image data IDATA based on a position within the pixel section 100 based on the reference voltage Vref. The control section 400 can change a maximum gray scale and a minimum gray scale to be closer to a gray scale corresponding to the reference voltage Vref as it is farther from a center portion of the pixel section 100. For example, as it is farther from the center portion of the pixel section 100, a voltage difference between a voltage of the maximum gray scale and a voltage of the minimum gray scale can be reduced.

[0052] In other embodiments, the control section 400 can determine a reference gray scale corresponding to the reference voltage Vref, and control a gray scale histogram of at least a portion of the image data IDATA based on the reference gray scale.

[0053] The configuration and functions of the control section 400 will be described in detail with reference to Figures 5 to 11

[0054] ​The scan driving section 200 can receive the first control signal SCS from the control section 400, and supply the first scan signal, the second scan signal, and the third scan signal to the first scan lines S11 to S1n, the second scan lines S21 to S2n, and the third scan lines S31 to S3n, respectively, based on the first control signal SCS. In addition, the scan driving section 200 can supply the light emission control signal to the light emission control lines E1 to En.

[0055] For example, the first scan signal can be supplied to the first scan lines S11 to S1n sequentially, the second scan signal can be supplied to the second scan lines S21 to S2n sequentially, and the third scan signal can be supplied to the third scan lines S31 to S3n sequentially. The light emission control signal can be supplied to the light emission control lines E1 to En sequentially.

[0056] The scan signal can be set to a gate-on voltage (e.g., a low voltage). The transistor receiving the scan signal can be set to an on state when the scan signal is supplied.

[0057] The light emission control signal can be set to a gate-off voltage (e.g., a high voltage). The transistor receiving the light emission control signal can be set to an off state when the light emission control signal is supplied, and can be set to an on state in other cases.

[0058] The scan driving section 200 can be mounted to the substrate by a thin film process. In Figure 1 One scan driving section supplying the first scan signal to the third scan signal and the light emission control signal is shown in the above embodiment, but the present application is not limited thereto. For example, the scan driving section 200 can include a plurality of scan driving sections supplying at least one of the first scan signal to the third scan signal and the light emission control signal, respectively.

[0059] The data driving section 300 can receive the second control signal DCS and the corrected image data CADATA from the control section 400. The data driving section 300 can supply the data signal (data voltage) to the data lines D1 to Dm in correspondence with the second control signal DCS.

[0060] The area compensation section 500 can perform zonal attenuation compensation that controls luminance differently according to the spatial location of each pixel PX based on the load. In an embodiment, the area compensation section 500 can generate a zonal attenuation coefficient ZF that is applied to the image data IDATA so that luminance decreases as it moves away from the center of the pixel section 100.

[0061] That is, the area fade compensation can mean a luminance compensation method in which the luminance is gradually reduced from the center of the pixel portion 100 toward the outer periphery. Thus, the outer periphery region of the pixel portion 100 can display an image darker than the center portion, and the image can be improved in the sense of immersion and the power consumption can be reduced. In one embodiment, the luminance distribution of the corrected image data CDATA can have a Gaussian distribution from the center portion of the pixel portion 100.

[0062] On the other hand, the display device 1000 can operate in one of a first mode (or, a normal mode) in which a data voltage is written on the basis of a first frequency in order to display a dynamic image or the like and a second mode (or, a low power mode) in which a data voltage is written on the basis of a second frequency in order to display a static image or the like. Here, the second frequency can be a value lower than the first frequency. For example, the second frequency can be 30 Hz or lower and the first frequency can be 60 Hz or higher.

[0063] In the low frequency driving in the second mode, leakage of the driving current in the pixel PX can occur, and due to such a leakage current, flicker can be recognized. In order to prevent or minimize the leakage current, a pixel as illustrated in Figure 2 may be proposed. That is, the reference voltage Vref can be supplied to the pixel PX to improve flicker in low frequency driving. In addition, according to the flicker recognition characteristics of an image viewer, there is a tendency that flicker is more easily recognized at a peripheral viewpoint of the viewer than at a central viewpoint of the viewer.

[0064] In order to improve the case where flicker at the peripheral viewpoint (i.e., the outer periphery region of the pixel portion 100) is recognized, the control portion 400 can adjust the gray scale range on the basis of the reference voltage Vref and the reference gray scale corresponding thereto (see Figures 5 to 8 ) in the second mode, or shift the representative gray scale of the gray scale histogram of the outer periphery region on the basis of the reference gray scale (see Figures 9 to 11 ). That is, by correction of the image data IDATA, the flicker recognition problem of the outer periphery region of the display device 1000 in the case where the area fade compensation and the low frequency driving are performed can be improved.

[0065] Figure 2 is a circuit diagram of an example of a pixel included in a display device of Figure 1 .

[0066] In Figure 2 , for convenience of explanation, a pixel PXij (where i, j are natural numbers) located at the i-th horizontal line (or the i-th pixel row) and connected to the j-th data line Dj is illustrated.

[0067] Referring to Figure 2 , the pixel PXij can include a light emitting element LD, a first transistor T1 to an eighth transistor T8, and an energy storage capacitor Cst.

[0068] The first electrode (anode or cathode) of the light emitting element LD is connected to the seventh transistor T7, and the second electrode (cathode or anode) is connected to the second power supply VSS. The light emitting element LD generates light of a predetermined brightness in correspondence with the amount of current supplied from the first transistor Tl.

[0069] In one embodiment, the light emitting element LD can be an organic light emitting diode including an organic light emitting layer. In other embodiments, the light emitting element LD can be an inorganic light emitting element formed of an inorganic substance. In other embodiments, the light emitting element LD can also be a light emitting element composed of a combination of an inorganic substance and an organic substance. Alternatively, the light emitting element LD can also have a configuration in which a plurality of inorganic light emitting elements are connected in parallel and / or in series between the second power supply VSS and the seventh transistor T7.

[0070] The first transistor Tl (or driving transistor) can be connected between the second node N2 and the third node N3. The gate electrode of the first transistor Tl can be connected to the first node Nl. The first transistor Tl can control the amount of current (driving current) flowing from the first power supply VDD to the second power supply VSS via the light emitting element LD based on the voltage of the first node Nl. To this end, the first power supply VDD can be set to a higher voltage than the second power supply VSS.

[0071] The second transistor T2 can be connected between the jth data line Dj (hereinafter, referred to as data line) and the second node N2. The gate electrode of the second transistor T2 can be connected to the ith first scan line Sli (hereinafter, referred to as first scan line). The second transistor T2 can be turned on when a first scan signal is supplied to the first scan line Sli, thereby electrically connecting the data line Dj and the second node N2.

[0072] The third transistor T3 and the fourth transistor T4 can be connected in series between the first node Nl and the third node N3. The gate electrode of the third transistor T3 and the gate electrode of the fourth transistor T4 can be connected to the ith second scan line S2i (hereinafter, referred to as second scan line). The third transistor T3 and the fourth transistor T4 can be turned on by a second scan signal supplied to the second scan line S2i.

[0073] On the other hand, due to the physical layer structure of each transistor, a parasitic capacitance component can exist between the fourth node N4 and the second scan line S2i. In order to prevent unintended leakage current caused by such a parasitic capacitance, a fifth transistor T5 capable of directly controlling the voltage of the fourth node N4 can be added.

[0074] The fifth transistor T5 can be connected to the fourth node N4 between the third transistor T3 and the fourth transistor T4. The fifth transistor T5 can supply the reference voltage Vref to the fourth node N4. A gate electrode of the fifth transistor T5 can be connected to the i-th light emission control line Ei (hereinafter, referred to as a light emission control line). The fifth transistor T5 can be turned off by a light emission control signal (high level) supplied to the light emission control line Ei. That is, the fifth transistor T5 can be turned on to supply the reference voltage Vref to the fourth node N4 during a light emission period.

[0075] In one embodiment, the reference voltage Vref can be a value included in a data voltage range determined in accordance with a gray scale range. For example, the reference voltage Vref can be a middle value of the data voltage range. The reference voltage Vref has a value between a black gray scale voltage and a white gray scale voltage, and thus can control the source-drain voltage of the third transistor T3 during a light emission period in which the second scan signal is not supplied at a low level. Accordingly, during the light emission period, leakage of a driving current toward the current paths of the third transistor T3 and the fourth transistor T4 can be suppressed.

[0076] The sixth transistor T6 can be connected between the first power supply VDD and the second node N2. A gate electrode of the sixth transistor T6 can be connected to the light emission control line Ei. The seventh transistor T7 can be connected between the third node N3 and the light emission element LD. A gate electrode of the seventh transistor T7 can be connected to the light emission control line Ei. The sixth transistor T6 and the seventh transistor T7 can be turned off when a light emission control signal is supplied to the light emission control line Ei, and can be turned on in other cases.

[0077] The eighth transistor T8 can be connected to the third node N3. A gate electrode of the eighth transistor T8 can be connected to the i-th third scan line S3i (hereinafter, referred to as a third scan line). The eighth transistor T8 can be turned on by a third scan signal supplied to the third scan line S3i, and thus supply the initialization voltage Vint to the third node N3.

[0078] The storage capacitor Cst can be connected between the first power supply VDD and the first node N1.

[0079] Figure 3 is a signal supplied to the pixel PXij. Figure 2 is a timing chart of an example of a signal supplied to the pixel PXij.

[0080] Referring to Figures 1 to 3 , the pixel PXij and the display device 1000 including the same can operate in low-frequency driving (low-power driving) to display a still image or the like.

[0081] In the second mode in which low-frequency driving is performed, the light emission control signal and the third scan signal can be supplied at a first frequency, and the first scan signal and the second scan signal can be supplied at a second frequency lower than the first frequency. For example, the first frequency can be 60 Hz, and the second frequency can be 10 Hz. That is, as shown in FIG. 6, the frequency of the first scan signal supplied to the first scan line S1i and the frequency of the second scan signal supplied to the second scan line S2i can be lower than the frequency at which the light emission control signal and the third scan signal are supplied. Figure 3

[0082] In an embodiment, in the first mode (normal driving), the light emission control signal, the first scan signal, the second scan signal, and the third scan signal can be supplied at the same frequency.

[0083] Except for the period in which the light emission control signal has a low level in the first period P1, a period other than the light emission period can be a non-light emission period.

[0084] In the first period P1 in which the fifth transistor T5 to the seventh transistor T7 have an on state, the third scan signal can be supplied to the third scan line S3i. In the first period P1, the eighth transistor T8 can be turned on, and thus the initialization voltage Vint can be supplied to the light emitting element LD. That is, in the first period P1, the anode voltage of the light emitting element LD can be initialized.

[0085] In the second period P2, a high level of the light emission control signal, a low level of the second scan signal, and a low level of the third scan signal can be supplied. The fifth transistor T5 to the seventh transistor T7 can be turned off, and the third transistor T3 and the fourth transistor T4 can be turned on. The eighth transistor T8 can maintain an on state. Thus, the initialization voltage Vint can be supplied to the first node N1. That is, in the second period P2, the gate voltage of the first transistor T1 can be initialized.

[0086] In the third period P3, the supply of the third scan signal can be interrupted, and the first scan signal can be supplied to the first scan line S1i. In the third period P3, the eighth transistor T8 can be turned off, and the second transistor T2 can be turned on. The third transistor T3 and the fourth transistor T4 can maintain an on state. Thus, the first transistor T1 can be connected in a diode form. In the third period P3, data writing and threshold voltage compensation can be performed on the pixel PXij.

[0087] Then, if the supply of the light emission control signal to the light emission control line Ei is interrupted (i.e., the light emission control signal having a low level is supplied), the fifth transistor T5 to the seventh transistor T7 are turned on, and thus the pixel PXij can emit light.

[0088] ​In the second mode, in order to suppress an increase in the drain-source voltage of the third transistor T3 and the fourth transistor T4 caused by the parasitic capacitance, a reference voltage Vref can be applied through the fifth transistor T5.

[0089] However, since the reference voltage Vref is commonly supplied in all pixels, it is difficult to perform optimal drain current control for each pixel to which various data voltages are supplied. In particular, in the display device 1000 in which the area decay compensation is applied, the outer area of the pixel portion 100 emits light at a relatively low luminance than the center portion, and thus image data compensation for the drain current control and flicker control of the outer portion needs to be further performed.

[0090] Figure 4 is a diagram for illustrating an example of the area compensation portion included in the display device that compensates for luminance by Figure 1

[0091] With reference to Figure 1 and Figure 4 , the area compensation portion 500 can perform the area decay compensation that controls luminance according to spatial positions of respective pixels based on the load.

[0092] In an embodiment, the load can be derived from the effective pixel rate. That is, the load can be detected based on a ratio of pixels that emit light among all pixels or a ratio of luminance of the current frame with respect to the maximum luminance. For example, the area compensation portion 500 can transform the image data IDATA into luminance data and detect the load of the entire pixel portion 100 based on the luminance data. The brighter image can be displayed as the load increases.

[0093] The area compensation portion 500 can determine the area decay coefficient ZF that is applied to the compensation of the image data IDATA based on the load. The area compensation portion 500 can determine the area decay coefficient ZF using a look-up table in which the area decay coefficient ZF is set according to the size of the load. For example, the area decay coefficient ZF can be linearly or nonlinearly set in the look-up table in proportion to the increase in the load. Alternatively, the area decay coefficient ZF can be determined by interpolation based on values set in the look-up table.

[0094] According to an embodiment, the area decay coefficient ZF increases as the load increases, and thus the degree to which luminance decreases as it moves away from the center portion of the pixel portion 100 can be increased.

[0095] In an embodiment, the compensation of the image data IDATA based on the area decay coefficient ZF can be applied to respective pixels included in a preset outer area of the pixel portion 100. In this case, the area decay compensation can be performed only for the outer area.

[0096] ​The spatial location of the pixel corresponding to the image data DATA can extract the coordinate values x and y representing the pixel position as factors. For example, the left upper end of the pixel section 100 can be [x, y] = [0, 0], and the right lower end can be [x, y] = [the width w of the image, the height h of the image]. The manner for performing the area attenuation compensation therefor can be such that the degree of luminance reduction is increased as the position of the pixel is closer to the outer area of the pixel section 100. In an embodiment, the luminance distribution of the image data IDATA to which the area attenuation coefficient ZF is applied can have a Gaussian distribution from the center portion of the pixel section 100.

[0097] That is, the luminance of the second region A2, which is the outer region of the first region Al, can be lower than the luminance of the first region Al when representing the same gray scale. In addition, the luminance of the third region A3, which is the outer region of the second region A2, can be lower than the luminance of the second region A2 when representing the same gray scale. For example, the luminance of the pixel of the second position B of the third region A3 can be lower than the luminance of the pixel of the first position (A) of the second region A2 when representing the same gray scale. Figure 4

[0098] Figure 5 is a block diagram illustrating an example of a control section included in the display device of Figure 1 Figure 6 is a diagram illustrating an example of the control section controlling the gray scale range of Figure 5

[0099] Referring to Figure 1 , Figure 4 , Figure 5 and Figure 6 , the control section 400A can include a reference voltage decision section 420 and a gray scale control section 440.

[0100] The reference voltage decision section 420 can decide the reference voltage Vref based on the load of the pixel section 100. In an embodiment, the load of the pixel section 100 is decided according to the effective pixel rate, and the reference data REF corresponding to the corresponding load is generated.

[0101] The reference voltage decision section 420 can calculate the effective pixel rate using the image data IDATA. The effective pixel rate can be calculated based on the ratio of the pixels emitting light among all the pixels or the average gray scale of all the pixels.

[0102] The reference voltage decision section 420 can include a look-up table in which the reference data REF corresponding to the effective pixel rate or the load is set. The reference data REF can be a digital value capable of deciding the size of the reference voltage Vref.

[0103] ​​​In one embodiment, in a case of a bright image (first image) in which average gradation is large, the data voltage supplied to each pixel including the first transistor T1 of the PMOS driving transistor Figure 2 may be formed to be relatively low. In contrast, in a case of a relatively low average gradation (second image), the data voltage supplied to each pixel can be relatively high. Therefore, the reference voltage Vref corresponding to the first image in which the load is relatively large can be decided to be a voltage lower than the reference voltage Vref corresponding to the second image in which the load is relatively small. In other words, the larger the load (effective pixel rate), the more the reference voltage decision section 420 can decrease the reference voltage Vref.

[0104] The reference voltage decision section 420 can supply the reference data REF to the gradation control section 440 and the power supply section 600.

[0105] The gradation control section 440 can remap the gradation of the image data IDATA based on the reference data REF corresponding to the reference voltage Vref so that the width of the gradation range decreases as it moves away from the center portion of the pixel section 100. The gradation control section 440 can correct the gradation of the image data IDATA or the image data IDATA to which the area attenuation coefficient ZF is applied. For example, the gradation control section 440 can include a lookup table in which gradations set according to the value of the reference data REF are stored, a hardware circuit configuration, and / or an algorithm.

[0106] The remapped image data IDATA can be output as corrected image data CADATA, and thus provided to the data driving section 300.

[0107] The gradation range can be decided according to the maximum gradation and the minimum gradation that can be expressed. In one embodiment, the gradation control section 440 can change the maximum gradation and the minimum gradation to be closer to the gradation corresponding to the reference voltage Vref as it moves away from the center portion of the pixel section 100. Thereby, the voltage difference between the voltage of the maximum gradation and the voltage of the minimum gradation can be decreased as it moves away from the center portion of the pixel section 100.

[0108] In one embodiment, the gradation range can decrease progressively as it moves away from the center portion of the pixel section 100. For example, the corrected image data CADATA can be expressed as shown in Figure 6 The image data IDATA supplied from an external graphic source or the like can be expressed in 256 gradations from 0 gradation G0 to 255 gradation G255. The 0 gradation G0 can be a black gradation, and the 255 gradation G255 can be a white gradation. The reference gradation Gref corresponding to the reference voltage Vref can be a gradation value between the 0 gradation G0 and the 255 gradation G255.

[0109] Further, the image data of the first region A1 can be expressed as a gradation range from 0 gradation G0 to 255 gradation G255 without gradation remapping. The gradation control section 440 can perform remapping on the image data of the third region A3. For example, the gradation range applicable to the third region A3 can be expressed as 40 gradation G40 to 190 gradation G190. That is, 0 gradation G0 to 255 gradation G255 are remapped to 40 gradation G40 to 190 gradation G190, respectively, so that the gradation range can be reduced. Thus, the data voltage supplied to the outer region of the center section can converge to a value closer to the reference voltage Vref.

[0110] As described above, the data voltage of each pixel PX supplied to the outer region in which flicker can be easily recognized due to the region attenuation compensation (e.g., the second region A2 and the third region A3 of the pixel section 100) can be adjusted to a value relatively closer to the reference voltage Vref. Thus, the farther from the first region A1 toward the third region A3, the difference between the voltage of the fourth node N4 and the voltage of the first node N1 (and the third node N3) of the pixel is reduced further, so that the leakage current within the pixel in the outer region of the pixel section 100 can be minimized. Thus, the flicker of the outer region of the pixel section 100 to which the region attenuation compensation is applied can be reduced. Figure 4

[0111] Figure 7a and Figure 7b are graphs showing an example of a change in data voltage corresponding to the maximum gradation and the minimum gradation output by the control section of Figure 5

[0112] Referring to Figures 4 to 7b , the range of the data voltage can be different depending on the position within the pixel section 100.

[0113] Figure 7a shows a change in data voltage (or gradation voltage V) from the center section C of the pixel section 100 to the x-axis direction X corresponding to the first direction DR1 or the y-axis direction Y corresponding to the second direction DR2. The voltage of the highest gradation can be expressed as a white voltage VW, and the voltage of the lowest gradation can be expressed as a black voltage VB. The reference voltage Vref can be an intermediate value of the white voltage VW and the black voltage VB corresponding to the center section C.

[0114] As shown in Figure 7a , the voltage difference between the white voltage VW and the black voltage VB can be reduced as moving away from the center section C of the pixel section 100 toward the x-axis direction X and / or the y-axis direction Y. According to an embodiment, the gradation range can be gradually reduced as moving away from the center section C of the pixel section 100. Thus, the black voltage VB can be set in a form of protruding from the center section C as a reference, and the white voltage VW can be set in a form of recessing from the center section C as a reference.​​

[0115] For example, the voltage difference between the white voltage VW and the black voltage VB of the pixel corresponding to the second position (B) can be smaller than the voltage difference between the white voltage VW and the black voltage VB of the pixel corresponding to the first position (A). Figure 4 Figure 4 The remaining gray scales between the black gray scale and the white gray scale can be represented as voltages between the black voltage VB and the white voltage VW according to the gray scale remapping result.

[0116] The remaining gray scales between the black gray scale and the white gray scale can be represented as voltages between the black voltage VB and the white voltage VW according to the gray scale remapping result.

[0117] On the other hand, when driven in the second mode for displaying a static image, the gray scale range can be gradually reduced in a preset period, so that the change of the static image caused by the sharp change of the gray scale range by position can not be recognized by the user.

[0118] In an embodiment, the gray scale control unit 440 can determine the target maximum gray scale and the target minimum gray scale corresponding to the edge position area (for example, the edge position of the third area A3) of the pixel unit 100 when entering the second mode. Figure 4

[0119] The black voltage VB and the white voltage VW when entering the second mode can be denoted as t0. The maximum gray scale and the minimum gray scale of the edge position area can be gradually changed until reaching the target maximum gray scale and the target minimum gray scale, respectively. The gradual change of the gray scale range based on the time lapse is the change of the gray voltage V, which can be denoted as t0, t1, t2. That is, the black voltage VB and the white voltage VW of the outer portion at the second time t2 can be closer to the reference voltage Vref than the black voltage VB and the white voltage VW of the outer portion at the first time t1.

[0120] Figure 7b denote the spatial change and the temporal change of the black voltage VB1, VB2 and the white voltage VW1, VW2 relative to the two-dimensional plane of the pixel unit 100 (i.e., the difference between VB1 and VB2 and the difference between VW1 and VW2).

[0121] As described above, the display device 1000 related to the embodiments of the present application can control, in the second mode for low-frequency driving, that the gray scale range (and the gray voltage range) becomes narrower as more toward the outer portion of the pixel unit 100, with the reference voltage Vref as the reference. Therefore, the leakage current in the pixels of the outer portion area to which the area fading compensation is applied can be minimized. Therefore, the flicker of the outer portion of the pixel unit 100 when displaying a static image or the like can be reduced, and the image quality when low-frequency driving can be improved.

[0122] Figure 8 denote the spatial change and the temporal change of the black voltage VB1, VB2 and the white voltage VW1, VW2 relative to the two-dimensional plane of the pixel unit 100 (i.e., the difference between VB1 and VB2 and the difference between VW1 and VW2).​​Figure 5 The figure shows another example of the change in data voltage corresponding to the maximum and minimum gray levels output by the control unit.

[0123] Reference Figure 5 , Figure 7a and Figure 8 The reference voltage Vref can be determined according to the size of the load.

[0124] In one embodiment, the larger the load, the more the control unit 400A reduces the reference voltage Vref. Figure 8 The reference voltage Vref can be set to the same as... Figure 7a Compared to relatively low voltage values. In addition, the voltage difference between the maximum gray level voltage (white voltage VW) of the center part C and the maximum gray level voltage (white voltage VW) of the outer contour can be different from the voltage difference between the minimum gray level voltage (black voltage VB) of the center part C and the minimum gray level voltage (black voltage VB) of the outer contour.

[0125] like Figure 8 As shown, when the reference voltage Vref is closer to the white voltage VW than the black voltage VB applied to the center C of the pixel section 100, the spatial variation of the black voltage VB can be greater than the spatial variation of the white voltage VW. Furthermore, the temporal variation of the black voltage VB (t0->t1-t2) can be greater than the temporal variation of the white voltage VW (t0->t1-t2).

[0126] Conversely, when the reference voltage Vref is closer to the black voltage VB than the white voltage VW applied to the center C of the pixel section 100, the spatial variation of the black voltage VB can be less than the spatial variation of the white voltage VW. Furthermore, the temporal variation of the black voltage VB can be less than the temporal variation of the white voltage VW.

[0127] Figure 9 It means Figure 1 A block diagram of another example of the control unit included in the display device.

[0128] Reference Figure 1 , Figure 4 and Figure 9 The control unit 400B can determine the reference voltage Vref supplied to each pixel PX and the reference gray level Gref corresponding to the reference voltage Vref based on the overall load of the pixel unit 100, and control the gray level histogram of the image data of the second region A2 (and the third region A3) based on the reference gray level Gref.

[0129] In one embodiment, the control unit 400B may include an image analysis unit 450, a histogram shifting unit 470, and a distribution control unit 490.

[0130] The image analysis section 450 can analyze the gradation information included in the image data IDATA to calculate a gradation histogram. It can be understood that the gradation histogram is the number of pixels corresponding to each gradation in a frame.

[0131] The image analysis section 450 can determine the average value of the gradation histogram of the entire pixel section 100 as the reference gradation Gref, and determine the average value of the gradation histogram of the second region A2 as the first representative gradation RG1. Similarly, the image analysis section 450 can determine the average value of the gradation histogram of the third region A3 as the second representative gradation RG2. Figure 10c

[0132] The histogram shift section 470 can shift the entire gradation histogram of the second region A2 so that the first representative gradation RG1 is shifted toward the reference gradation Gref. The histogram shift section 470 can shift the entire gradation of the image data corresponding to the second region A2 in correspondence with the amount of change of the first representative gradation RG1 shifted toward the target gradation. For example, in the case where the first representative gradation RG1 is shifted by 10 gradations in the positive direction, each gradation of the second region A2 can be transformed to be shifted by 10 gradations in the positive direction. Such gradation shift can be achieved by various known techniques such as gradation remapping. The shifted image data SDATA can be provided to the distribution control section 490.

[0133] Similarly, the histogram shift section 470 can shift the entire gradation histogram of the third region A3 so that the second representative gradation RG2 is shifted toward the reference gradation Gref. At this time, the amount of change of the first representative gradation RG1 and the amount of change of the second representative gradation RG2 can be different from each other. In an embodiment, the shifted second representative gradation S_RG2 and the reference gradation Gref can be controlled to have a smaller gradation difference than the shifted first representative gradation S_RG1 and the reference gradation Gref. For example, the more toward the outer portion of the pixel section 100, the representative gradation of the corresponding region can be shifted to a value closer to the reference gradation Gref. Figure 10c Figure 10c Figure 10c

[0134] The distribution control section 490 can narrow the histogram distribution of a part of the shifted image histogram (excess gradation region) so that the shifted image data SDATA can be expressed within the gradation range and the gamma voltage range set in the display device. In addition, the distribution control section 490 can expand the histogram distribution of another part of the shifted image histogram (insufficient gradation region). The gradation of the image data CDATA corrected by the distribution control section 490 can be included in the gradation range set in the display device. ​​​​

[0135] The operation of the control section 400B will be described in detail below with reference to Figures 10a to 11

[0136] Figure 10a is a graph showing an example of a gray scale histogram of the first region of the pixel section, Figure 10b is a graph showing an example of a gray scale histogram shift of the second region of the pixel section, Figure 10c is a graph showing an example of a gray scale histogram shift of the third region of the pixel section.

[0137] With reference to Figure 4 , Figure 9 , Figure 10a , Figure 10b and Figure 10c , the control section 400B can shift the representative gray scale and the overall gray scale of the image data IDATA according to the region of the pixel section 100.

[0138] As shown in Figure 10a , the image analysis section 450 can analyze the gray scale histogram of the first region Al corresponding to the center portion of the pixel section 100, thereby calculating the representative gray scale RG C of the first region Al. The representative gray scale RG C of the first region Al can be different from the reference gray scale Gref.

[0139] The first region Al is a region in which the main information of the image is included and the user's visual field is concentrated, and thus the control section 400B does not shift the image data and the representative gray scale RG C of the first region Al.

[0140] As shown in Figure 10b , the image analysis section 450 can analyze the gray scale histogram of the second region A2 to calculate the first representative gray scale RG1. The histogram shift section 470 can shift the first representative gray scale RG1 toward the reference gray scale Gref, and can shift the entire gray scale histogram according to the gray scale variation amount of the shifted first representative gray scale S_RG1.

[0141] For example, the first gray scale histogram C1 at the time of entering the second mode in which a still image is displayed (t0) can be corrected to the second gray scale histogram S_C1 shifted toward the reference gray scale Gref at the first time t1.

[0142] As shown in Figure 10c , the image analysis section 450 can analyze the gray scale histogram of the third region A3 to calculate the second representative gray scale RG2. The histogram shift section 470 can shift the second representative gray scale RG2 toward the reference gray scale Gref, and can shift the entire gray scale histogram according to the gray scale variation amount of the shifted second representative gray scale S_RG2.

[0143] ​For example, when entering the second mode for displaying a static image (t0), the third grayscale histogram C2 can be corrected at the first time t1 to a third grayscale histogram S_C2 that has been shifted toward the reference grayscale Gref. According to an embodiment, the shifted second representative grayscale S_RG2 can be the same as the reference grayscale Gref.

[0144] At this time, as Figure 10b and Figure 10c As shown, the grayscale difference between the shifted second representative grayscale S_RG2 and the reference grayscale Gref can be smaller than the grayscale difference between the shifted first representative grayscale S_RG1 and the reference grayscale Gref. That is, corrections can be made so that the representative grayscale of the grayscale histogram is closer to the reference grayscale Gref the further it is towards the outer contour of the pixel portion 100.

[0145] Therefore, the grayscale and grayscale range of the image data corresponding to the outline of the pixel unit 100 can be corrected to values ​​closer to the reference grayscale Gref, thereby reducing the deviation between the corresponding grayscale voltage range (data voltage range) and the reference voltage Vref supplied to the pixel. Thus, leakage current within the pixel in the outline region of the applicable area attenuation compensation can be minimized.

[0146] Furthermore, such as Figure 10b and Figure 10c As shown, the grayscale histograms of the corresponding regions can be shifted so that the grayscale values ​​of the regions closer to the outer contour of the pixel 100 gradually approach the reference grayscale Gref.

[0147] Figure 11 It means through Figure 9 The control unit corrected an example of a grayscale histogram.

[0148] Reference Figures 9 to 11 The control unit 400B may include a distribution control unit 490 that adjusts the histogram distribution of the shifted grayscale histogram S_C2.

[0149] The display device 1000 sets the representable grayscale range and the corresponding grayscale voltage range. That is, it can output a grayscale voltage corresponding to the grayscale range between a first grayscale G1 and a second grayscale G2. For example, as... Figure 11 As shown, the first gray level G1 can be set to 0 gray level G0, the second gray level G2 can be set to 255 gray level G255, and the gray level range can be represented by an 8-bit digital value.

[0150] However, according to the operation of the histogram shift section 470, the shifted gray scale histogram S_C2 can be out of the preset gray scale range. For example, a low gray scale highlight phenomenon can be recognized due to the shifted first gray scale S_G1, or an image quality can be degraded due to the fact that a high gray scale region is not expressed due to the shifted second gray scale S_G2.

[0151] The distribution control section 490 can expand the histogram distribution of the insufficient gray scale region IA and shrink the histogram distribution of the excess gray scale region OA by remapping, interpolation, or the like on the shifted image data SDATA. Referring to FIG. 6, the distribution control section 490 can expand the histogram distribution of the insufficient gray scale region IA to the first gray scale G1 and shrink the histogram distribution of the excess gray scale region OA to the second gray scale G2. Figure 11 The insufficient gray scale region IA can be a region in which a gray scale is not expressed due to the shift of the gray scale histogram, i.e., a gray scale range between the first gray scale G1 and the shifted first gray scale S_G1. In addition, the excess gray scale region OA can be a region out of the expressible gray scale range, i.e., a gray scale range between the second gray scale G2 and the shifted second gray scale S_G2. In this case, the distribution control section 490 can expand the histogram distribution of the insufficient gray scale region IA to the first gray scale G1 and shrink the histogram distribution of the excess gray scale region OA to the second gray scale G2. Figure 11 The case in which the gray scale histogram C2 is shifted to the right is shown in FIG. 6, but is not limited thereto, and the gray scale histogram C2 can also be shifted to the left. In this case, the insufficient gray scale region IA and the excess gray scale region OA can be set in positions opposite to those of the case in which the gray scale histogram C2 is shifted to the right. Figure 11

[0152] The distribution control section 490 can expand the gray scale histogram distribution of the first gray scale region GA1 to the first gray scale G1 including the insufficient gray scale region IA, so that the gray scale of the insufficient gray scale region IA of the shifted gray scale histogram S_C2 can be expressed. Here, the first gray scale region GA1 can be a gray scale range between the shifted second representative gray scale S_RG2 and the shifted first gray scale S_G1. That is, by the expansion of the gray scale histogram, an image can be displayed in a gray scale range including the first gray scale region GA1 and the insufficient gray scale region IA (i.e., GA1+IA).

[0153] By correcting the image data so that the gray scale histogram corresponding to the first gray scale region GA1 is expanded to the first gray scale G1, it is possible to minimize the case in which a low gray scale highlight is recognized.

[0154] In addition, the distribution control section 490 can shrink the gray scale histogram distribution of the second gray scale region GA2 to within the second gray scale G2, so that the excess gray scale region OA of the shifted gray scale histogram S_C2 is expressed. Here, the second gray scale region GA2 can be a gray scale range between the shifted second representative gray scale S_RG2 and the shifted second gray scale S_G2. That is, by the shrinkage of the gray scale histogram, an image can be displayed in a gray scale range excluding the excess gray scale region OA from the second gray scale region GA2 (i.e., GA2-OA).

[0155] ​By correcting the image data so that the gray scale histogram corresponding to the second gray scale region GA2 is reduced within the displayable gray scale, the image quality can be improved.

[0156] As described above, the distribution control section 490 can generate corrected image data C DATA including the corrected gray scale histogram C C2. The data driving section 300 can generate a data signal based on the corrected image data C DATA. Figure 1

[0157] As described above, each embodiment of the present application relates to a low-frequency driven display device that can be controlled so that the gray scale range (and the gray scale voltage range) becomes narrower toward the outer periphery of the pixel section with reference to a reference voltage (refer to Vref). In addition, each embodiment of the present application relates to a low-frequency driven display device that can be corrected so that the gray scale histogram and the representative gray scale (refer to RG1) of each corresponding region become closer to a reference gray scale Gref toward the outer periphery of the pixel section. Figure 2 Figure 9

[0158] Thus, the deviation between the gray scale voltage range of the image data corresponding to the outer periphery of the pixel section and the reference voltage Vref supplied to the pixel can be reduced. Therefore, the leakage current in the pixel within the outer periphery region of the pixel section to which the area attenuation compensation is applied can be minimized, and the flicker of the outer periphery of the pixel section at the time of low-frequency driving for displaying a static image or the like can be reduced.

[0159] The above has been described with reference to each embodiment of the present application, but those skilled in the art will understand that various modifications and changes can be made to the present application without departing from the spirit and scope of the present application as recited in the claims.​​​

Claims

1. A display device comprising: a pixel portion that displays an image and includes a plurality of pixels that receive a reference voltage; a control portion that decides a value of the reference voltage for suppressing a leakage current of the plurality of pixels based on a load of the entire pixel portion, and that, when displaying a still image by low-frequency driving, causes a gradation range of image data based on a position within the pixel portion to be progressively reduced with reference to the reference voltage farther away from a center portion of the pixel portion; a data drive portion that supplies a data voltage to the pixel portion through a plurality of data lines based on the adjusted gradation range; and a scan drive portion that supplies a scan signal to the pixel portion through a plurality of scan lines.

2. The display device according to claim 1, wherein a difference between a maximum gradation of image data corresponding to a first position of the pixel portion and a reference gradation corresponding to the reference voltage is smaller than a difference between a maximum gradation of image data corresponding to a second position of the pixel portion and the reference gradation, a difference between a minimum gradation of the image data corresponding to the first position and the reference gradation is larger than a difference between a minimum gradation of the image data corresponding to the second position and the reference gradation, a distance from the center portion of the pixel portion to the second position is larger than a distance from the center portion to the first position.

3. The display device according to claim 2, wherein a voltage difference between a voltage of the maximum gradation and a voltage of the minimum gradation corresponding to the second position is smaller than a voltage difference between a voltage of the maximum gradation and a voltage of the minimum gradation corresponding to the first position.

4. The display device according to claim 2, wherein a gradation range of image data corresponding to the second position is smaller than a gradation range of image data corresponding to the first position.

5. The display device according to claim 2, wherein the greater the load, the more the control portion reduces the reference voltage.

6. The display device according to claim 5, wherein a voltage difference between a voltage of the maximum gradation of the center portion and a voltage of the maximum gradation of an outer portion of the pixel portion is different from a voltage difference between a voltage of the minimum gradation of the center portion and a voltage of the minimum gradation of the outer portion.

7. The display device according to claim 1, wherein the control portion includes: a reference voltage deciding portion that decides the reference voltage based on an effective pixel rate of the pixel portion; and a gradation control portion that, based on the reference voltage, re-maps a gradation of the image data such that the farther away from a center portion of the pixel portion, the smaller the width of the gradation range, the effective pixel rate is calculated based on a ratio of pixels that emit light among all pixels or an average gradation of all pixels.

8. The display device according to claim 7, wherein a voltage of a maximum gradation of a first region including the center portion is smaller than a voltage of a maximum gradation of a second region including an outer portion of the pixel portion, a voltage of a minimum gradation of the first region is larger than a voltage of a minimum gradation of the second region. ​ 9. The display device according to claim 7, wherein the gradation control section decides a target maximum gradation and a target minimum gradation corresponding to an edge position region of the pixel section based on the reference voltage, the maximum gradation and the minimum gradation of the edge position region are gradually changed in a predetermined period, respectively, so as to reach the target maximum gradation and the target minimum gradation.

10. The display device according to claim 2, further comprising: a region compensation section which performs a region attenuation compensation which controls luminance according to a spatial position of the pixel based on the load.

11. The display device according to claim 10, wherein the region compensation section generates a region attenuation coefficient which is applied to the image data so that the luminance decreases as it is farther from the center section.

12. The display device according to claim 2, wherein each of the pixels includes: a light emitting element; a first transistor which controls a drive current based on a voltage of a first node and is connected between a second node and a third node; a second transistor which is connected between one of a plurality of data lines and the second node and is turned on according to a first scan signal supplied to a first scan line; a third transistor and a fourth transistor which are connected in series between the first node and the third node and are turned on according to a second scan signal supplied to a second scan line; a fifth transistor which supplies the reference voltage to a fourth node between the third transistor and the fourth transistor and is turned off according to a light emission control signal supplied to a light emission control line.

13. The display device according to claim 12, wherein each of the pixels includes: a sixth transistor which is connected between a first power supply and the second node and is turned off according to the light emission control signal supplied to the light emission control line; a seventh transistor which is connected between the third node and the light emitting element and is turned off according to the light emission control signal supplied to the light emission control line; and an eighth transistor which supplies an initialization voltage to the third node and is turned on according to a third scan signal supplied to a third scan line.

14. The display device according to claim 13, wherein the pixel operates in one of a first mode in which the data voltage is written based on a first frequency and a second mode in which the data voltage is written based on a second frequency which is lower than the first frequency, the control section adjusts the reference voltage and the gradation range in the second mode.

15. A display device comprising: a pixel section including a plurality of pixels arranged in a first region having a center section and a second region surrounding the first region; a control section which decides a value of a reference voltage supplied to a plurality of the pixels in order to suppress a leak current of the plurality of the pixels and a reference gradation corresponding to the reference voltage based on a load of the pixel section as a whole, and shifts a first representative gradation decided by an average value of a gradation histogram of image data of the second region based on a gradation corresponding to the reference gradation when a still image is displayed by low frequency driving. ​ a data driving section that supplies a data voltage to the pixel section through a plurality of data lines on the basis of the image data; and a scan driving section that supplies a scan signal to the pixel section through a plurality of scan lines.

16. The display device according to claim 15, wherein the control section includes: an image analysis section that determines an average value of a histogram of gray scales of the entire pixel section as the reference gray scale, and determines an average value of the histogram of gray scales of the second region as the first representative gray scale; and a histogram shift section that shifts the histogram of gray scales of the second region so that the first representative gray scale is shifted toward the reference gray scale.

17. The display device according to claim 16, wherein the control section includes a distribution control section that narrows a distribution of a histogram of gray scales of a first gray scale region that exceeds a gray scale region to within a preset first gray scale so that the histogram of gray scales that represents the shift includes the first gray scale region that exceeds the gray scale region.

18. The display device according to claim 17, wherein the distribution control section expands a distribution of a histogram of gray scales of a second gray scale region to a preset second gray scale so that a gray scale of a deficient gray scale region of the histogram of gray scales that represents the shift, the first gray scale and the second gray scale are one of a maximum gray scale and a minimum gray scale set in the control section, respectively.

19. The display device according to claim 17, wherein the pixel section further includes a third region that surrounds the second region, the control section shifts a histogram of gray scales of the third region so that a second representative gray scale that is an average value of the histogram of gray scales of the third region is shifted toward the reference gray scale, a gray scale difference between the shifted second representative gray scale and the reference gray scale is smaller than a gray scale difference between the shifted first representative gray scale and the reference gray scale.

20. The display device according to claim 17, wherein each of the pixels includes: a light emitting element; a first transistor that controls a drive current on the basis of a voltage of a first node, and is connected between a second node and a third node; a second transistor that is connected between one of a plurality of the data lines and the second node, and is turned on in accordance with a first scan signal supplied to a first scan line; a third transistor and a fourth transistor that are connected in series between the first node and the third node, and are turned on in accordance with a second scan signal supplied to a second scan line; a fifth transistor that supplies the reference voltage to a fourth node between the third transistor and the fourth transistor, and is turned off in accordance with a light emission control signal supplied to a light emission control line.

Images