Display device and gamma cell for display panel

Abstract

The present disclosure provides a display apparatus and a gamma unit for a display panel. The display apparatus includes a gamma unit including a gamma reference voltage generator generating a plurality of gamma reference voltages and a gamma voltage generator generating a gamma voltage based on the gamma reference voltages, a data driver generating a data voltage based on the gamma voltage, and a display panel electrically connected to the data driver. The gamma reference voltage generator includes a first gamma reference voltage generator generating a first gamma reference voltage based on external power and a second gamma reference voltage generator generating a second gamma reference voltage based on a feedback voltage from a high potential power voltage of the display panel. Accordingly, the plurality of gamma reference voltages can vary according to characteristics of an image to be used.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2021-0156600, filed on November 15, 2021, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to display devices and gamma units for display panels, more specifically to display devices that improve display quality by changing a gamma reference voltage. Background Technology

[0004] As display devices used as monitors for computers, televisions, or cellular phones, there are organic light-emitting display devices (OLEDs) that are self-emitting devices and liquid crystal display devices (LCDs) that require a separate light source.

[0005] The applications of display devices are being diversified to include personal digital assistants and monitors for computers and televisions, and research is underway on display devices with large display areas and reduced size and weight.

[0006] Simultaneously, the display device divides the gamma reference voltage to generate multiple gamma voltages, and generates a data voltage based on these multiple gamma voltages. At this point, the characteristics of the image displayed on the display device can vary according to the gamma reference voltage and the gamma voltages. Summary of the Invention

[0007] The purpose of this disclosure is to provide a display device that controls brightness by changing the gamma reference voltage.

[0008] Another objective of this disclosure is to provide a display device that reduces screen flicker caused by sudden voltage changes when the gamma reference voltage changes.

[0009] Another objective of this disclosure is to provide a display device that couples a gamma reference voltage and a high-potential power voltage to minimize brightness variations due to voltage drops.

[0010] The purpose of this disclosure is not limited to the purposes mentioned above, and other purposes not mentioned above will be clearly understood by those skilled in the art from the following description.

[0011] To achieve the above objectives, according to one aspect of this disclosure, a display device includes: a gamma unit, comprising a gamma reference voltage generator for generating a plurality of gamma reference voltages and a gamma voltage generator for generating a gamma voltage based on the gamma reference voltages; a data driver for generating a data voltage based on the gamma voltages; and a display panel electrically connected to the data driver. The gamma reference voltage generator includes: a first gamma reference voltage generator for generating a first gamma reference voltage among the plurality of gamma reference voltages based on external power; and a second gamma reference voltage generator for generating a second gamma reference voltage among the plurality of gamma reference voltages based on a feedback voltage from a high-potential power voltage from the display panel. Therefore, according to this disclosure, the plurality of gamma reference voltages can vary according to the characteristics of the image to be used.

[0012] To achieve the above objectives, according to another aspect of this disclosure, a display device includes: a gamma unit comprising a first gamma reference voltage generator generating a first gamma reference voltage, a second gamma reference voltage generator generating a second gamma reference voltage, and a gamma voltage generator generating a gamma voltage based on the first and second gamma reference voltages; a data driver generating a data voltage based on the gamma voltage; and a display panel comprising a plurality of pixels driven by a high-potential electrical voltage and the data voltage, wherein the gamma reference voltage generator generates a gamma voltage based on the first gamma reference voltage when an on-pixel ratio, representing the ratio of on-pixels among the plurality of pixels, is lower than a reference pixel ratio, and the gamma voltage generator generates a gamma voltage based on the second gamma reference voltage when the on-pixel ratio is higher than the reference pixel ratio. Therefore, according to this disclosure, the first gamma reference voltage is used for relatively dark images with a low on-pixel ratio to increase black-and-white contrast. Furthermore, the second gamma reference voltage is used for relatively bright images with a high on-pixel ratio, thereby minimizing brightness degradation caused by changes in the high-potential electrical voltage.

[0013] To achieve the above objectives, according to another aspect of this disclosure, a gamma unit for a display panel includes: a gamma reference voltage generator for generating a plurality of gamma reference voltages; and a gamma voltage generator for generating a gamma voltage based on the gamma reference voltages, wherein the gamma reference voltage generator includes: a first gamma reference voltage generator for generating a first gamma reference voltage among the plurality of gamma reference voltages based on external power; and a second gamma reference voltage generator for generating a second gamma reference voltage among the plurality of gamma reference voltages based on a feedback voltage from a high-potential power voltage from the display panel.

[0014] Further details of the exemplary implementation are included in the detailed implementation and the accompanying drawings.

[0015] According to this disclosure, the gamma reference voltage can vary depending on the characteristics of the image to be displayed.

[0016] According to this disclosure, brightness variations caused by voltage drops of high-potential electrical voltages in images with a high on-pixel ratio can be minimized.

[0017] According to this disclosure, brightness is maximized in images with a low pass-through pixel ratio to improve contrast.

[0018] According to this disclosure, the gamma reference voltage is gradually varied to reduce screen flicker.

[0019] The effects of this disclosure are not limited to those exemplified above, and include a variety of other effects as described in this specification. Attached Figure Description

[0020] The above and other aspects, features and advantages of this disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0021] Figure 1 This is a schematic diagram of a display device according to an exemplary embodiment of the present disclosure.

[0022] Figure 2 This is a circuit diagram of a sub-pixel of a display device according to an exemplary embodiment of the present disclosure;

[0023] Figure 3 This is a diagram of the gamma unit of a display device according to an exemplary embodiment of the present disclosure.

[0024] Figure 4 This is a waveform of the gamma unit of a display device according to an exemplary embodiment of the present disclosure;

[0025] Figures 5A to 5C It is a schematic plan view of a display device used to illustrate the ratio of active pixels;

[0026] Figure 6A and Figure 6B This is a view used to illustrate the operation of the gamma unit when the ratio of active pixels is higher than the ratio of reference pixels; and

[0027] Figure 7A and Figure 7B This is a view used to illustrate the operation of the gamma unit when the ratio of active pixels is lower than the ratio of reference pixels. Detailed Implementation

[0028] The advantages and features of this disclosure, as well as methods for achieving these advantages and features, will become clear from the exemplary embodiments described in detail below with reference to the accompanying drawings. However, this disclosure is not limited to the exemplary embodiments disclosed herein, but will be implemented in various forms. The exemplary embodiments are provided merely as examples to enable those skilled in the art to fully understand the disclosure and scope of this disclosure. Therefore, this disclosure is limited only by the scope of the appended claims.

[0029] The shapes, dimensions, scales, angles, numbers, etc., shown in the accompanying drawings used to describe exemplary embodiments of this disclosure are merely examples, and this disclosure is not limited thereto. Throughout the specification, the same reference numerals generally denote the same elements. Furthermore, in the following description of this disclosure, detailed descriptions of known related technologies may be omitted to avoid unnecessarily obscuring the subject matter of this disclosure. Terms such as “comprising,” “having,” and “consisting of” as used herein are generally intended to allow for the addition of additional components, unless these terms are used in conjunction with the term “only.” Unless otherwise expressly stated, any reference to the singular may include the plural.

[0030] Even without explicit explanation, components are interpreted as including the normal tolerance range.

[0031] When using terms such as “on top of,” “above,” “below,” and “adjacent” to describe the positional relationship between two parts, one or more parts may be located between the two parts unless these terms are used with “immediately next to” or “directly.”

[0032] When an element or layer is placed "on" another element or layer, the other layer or element can be directly built on or between other elements.

[0033] Although the terms "first," "second," etc., are used to describe individual components, these components are not limited by these terms. These terms are merely used to distinguish one component from others. Therefore, the first component mentioned below can be a second component within the technical concept of this disclosure.

[0034] Throughout the specification, the same reference numerals generally denote the same elements.

[0035] For ease of description, the dimensions and thickness of each component shown in the accompanying drawings are illustrated, but this disclosure is not limited to the dimensions and thickness of the components shown.

[0036] Features of various embodiments of this disclosure may be partially or completely adhered to or combined with each other and may be interlocked and operated in technically different ways, and the embodiments may be implemented independently of each other or in relation to each other.

[0037] In the following, a display device according to an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0038] Figure 1 This is a schematic diagram of a display device according to an exemplary embodiment of the present disclosure. Figure 1 For ease of description, among the various components of the display device 100, the display panel 110, gate driver 120, data driver 130, gamma unit 150, power supply unit 140, and timing controller 160 are shown.

[0039] Reference Figure 1 The display device 100 includes: a display panel 110, which includes a plurality of sub-pixels SP; a gate driver 120 and a data driver 130, which provide various signals to the display panel 110; a gamma unit 150, which provides a gamma voltage VG to the data driver 130; a timing controller 160, which controls the gate driver 120 and the data driver 130; and a power supply unit 140, which provides various types of power.

[0040] Gate driver 120 provides scan signals to multiple scan lines SL according to multiple gate control signals GCS provided from timing controller 160. Although in Figure 1 The diagram shows a gate driver 120 positioned spaced apart from one side of the display panel 110, but the number and arrangement of gate drivers 120 are not limited thereto.

[0041] Data driver 130, based on multiple data control signals DCS provided from timing controller 160, uses gamma voltage VG to convert image data RGB input from timing controller 160 into data voltage Vdata. Data driver 130 receives gamma voltage VG from gamma unit 150, selects gamma voltage VG corresponding to the grayscale of image data RGB from the received gamma voltage VG to generate data voltage Vdata, and can provide the generated data voltage Vdata to multiple data lines DL.

[0042] The power supply unit 140 can generate power to be applied to the data driver 130, the gamma unit 150, and the display panel 110. The power supply unit 140 can provide power to drive the gamma unit 150 and the data driver 130, as well as a high-potential power voltage VDDEL and a low-potential power voltage VSSEL to drive the display panel 110. Furthermore, the power supply unit 140 can provide power to drive other configurations of the display device 100.

[0043] Timing controller 160 aligns externally input image data (RGB) to provide the image data (RGB) to data driver 130. Timing controller 160 can use externally input synchronization signals (e.g., dot clock signals, data enable signals, and horizontal / vertical synchronization signals) to generate a gate control signal GCS and a data control signal DCS. Timing controller 160 provides the gate control signal GCS and the data control signal DCS to gate driver 120 and data driver 130, respectively, to control gate driver 120 and data driver 130.

[0044] Display panel 110 is configured to display an image to a user and includes multiple subpixels SP. In display panel 110, multiple scan lines SL and multiple data lines DL intersect each other, and the multiple subpixels SP are respectively connected to the scan lines SL and data lines DL. Additionally, a high-potential power voltage VDDEL and a low-potential power voltage VSSEL can be provided to each of the multiple subpixels SP, as will be described below. Figure 2 To describe in more detail.

[0045] Multiple subpixels (SPs) are the smallest units for configuring a screen, and several subpixels (SPs) are grouped together to form a pixel. Each of the multiple subpixels (SPs) includes a light-emitting element and pixel circuitry for driving the light-emitting element. Depending on the type of display panel 110, the multiple light-emitting elements can be defined in different ways. For example, when the display panel 110 is an organic light-emitting display panel, the light-emitting element can be an organic light-emitting diode (OLED) including an anode, an organic light-emitting layer, and a cathode. Alternatively, light-emitting diodes (LEDs) or quantum dot light-emitting diodes (QLEDs) including quantum dots (QDs) can also be used as light-emitting elements.

[0046] Gamma unit 150 generates a gamma reference voltage and divides the gamma reference voltage to generate multiple gamma voltages VG. Gamma unit 150 generates multiple gamma voltages VG to provide the generated gamma voltages to data driver 130, and data driver 130 can generate data voltages based on the provided multiple gamma voltages VG.

[0047] Simultaneously, the gamma unit 150 can generate a gamma reference voltage using the feedback voltage VDDEL' of the high-potential electrical voltage VDDEL transmitted from the display panel 110 in a specific image. This will be referred to below. Figures 3 to 7B Describe it.

[0048] In the following text, reference will be made to Figure 2 A more detailed description of multiple sub-pixels SP.

[0049] Figure 2 This is a circuit diagram of a sub-pixel of a display device according to an exemplary embodiment of the present disclosure.

[0050] Reference Figure 2 Multiple sub-pixels SP are connected to the first scan line SL1, the second scan line SL2, the data line DL, the transmit control signal line EML, the first initialization line, the second initialization line, the high-potential power line, and the low-potential power line. Each sub-pixel SP contains a first transistor T1, a second transistor T2, a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, a driving transistor DT, a storage capacitor Cst, and a light-emitting element EL.

[0051] The driving transistor DT includes a gate electrode, a source electrode, and a drain electrode. The source electrode of the driving transistor DT is connected to a first node N1, the gate electrode is connected to a second node N2, and the drain electrode is connected to a third node N3. The driving transistor DT can control the driving current I flowing in the light-emitting element EL. OLED .

[0052] The first transistor T1 includes a gate electrode, a source electrode, and a drain electrode. The gate electrode of the first transistor T1 is connected to the second scan line SL2, the source electrode is connected to the second node N2, and the drain electrode is connected to the third node N3. The first transistor T1 can connect the gate electrode and the drain electrode of the driving transistor DT, thus forming a diode connection with the driving transistor DT. In the diode connection, the gate electrode and the drain electrode are short-circuited, causing the transistor to operate as a diode.

[0053] The second transistor T2 includes a gate electrode, a source electrode, and a drain electrode. The gate electrode of the second transistor T2 is connected to the second scan line SL2, the source electrode is connected to the data line DL, and the drain electrode is connected to the first node N1. The second transistor T2 can transmit the data voltage Vdata from the data line DL to the first node N1 based on the scan signal of the second scan line SL2.

[0054] The third transistor T3 includes a gate electrode, a source electrode, and a drain electrode. The gate electrode of the third transistor T3 is connected to the emitter control signal line EML, the source electrode is connected to the high-potential power line, and the drain electrode is connected to the first node N1. The third transistor T3 can send a high-potential power voltage VDDEL to the first node N1 based on the emitter control signal on the emitter control signal line EML.

[0055] The fourth transistor T4 includes a gate electrode, a source electrode, and a drain electrode. The gate electrode of the fourth transistor T4 is connected to the emitter control signal line EML, the source electrode is connected to the third node N3, and the drain electrode is connected to the fourth node N4. The fourth transistor T4 can drive the current I based on the emitter control signal on the emitter control signal line EML. OLEDData is transferred from the driving transistor DT to the light-emitting element EL.

[0056] The fifth transistor T5 includes a gate electrode, a source electrode, and a drain electrode. The gate electrode of the fifth transistor T5 is connected to the first scan line SL1, the source electrode is connected to the first initialization line, and the drain electrode is connected to the second node N2. The fifth transistor T5 can reset the second node N2 based on the scan signal of the first scan line SL1 using the first initialization voltage Vinit1 from the first initialization line.

[0057] The sixth transistor T6 includes a gate electrode, a source electrode, and a drain electrode. The gate electrode of the sixth transistor T6 is connected to the second scan line SL2, the source electrode is connected to the second initialization line, and the drain electrode is connected to the fourth node N4. The sixth transistor T6 can reset the fourth node N4 based on the scan signal of the second scan line SL2 using the second initialization voltage Vinit2 from the second initialization line.

[0058] The storage capacitor Cst comprises multiple capacitor electrodes. Some of these electrodes are connected to a high-potential power line, while others are connected to a second node N2. The threshold voltage of the driving transistor DT is compensated by a data voltage Vdata charged in the storage capacitor Cst to sample data and compensate for the deviation of each driving transistor DT in each of the multiple sub-pixels SP.

[0059] The light-emitting element EL includes a first electrode and a second electrode. The first electrode of the light-emitting element EL is connected to the fourth node N4, and the second electrode is connected to the low-potential power voltage VSSEL. The light-emitting element EL can be driven by a drive current I from the driving transistor DT. OLED Glowing light.

[0060] [Equation 1]

[0061] I oled = k / 2*(VDDEL-Vdata) 2

[0062] Simultaneously, the driving current I flowing in the light-emitting element EL OLED It can be defined by Equation 1. Here, k is a constant value determined by the mobility and parasitic capacitance of the driving transistor DT.

[0063] Referring to Equation 1, the driving current I OLEDThe brightness of the display device can be determined by the high-potential power voltage VDDEL and the data voltage Vdata. In this case, the data voltage Vdata can be generated based on the gamma voltage VG. In the display device 100 according to the exemplary embodiment of this disclosure, the gamma voltage VG used to generate the data voltage Vdata is generated solely by external power, or the gamma voltage is coupled to the high-potential power voltage VDDEL to control the brightness of the display device according to the image to be displayed. Therefore, in the display device 100 according to the exemplary embodiment of this disclosure, the brightness variation caused by the voltage drop of the high-potential power voltage VDDEL can be minimized according to the characteristics of the image to be displayed. Furthermore, the increase in brightness is maximized to improve the contrast between black and white (i.e., contrast ratio).

[0064] In the following text, reference will be made to Figures 3 to 7B A more detailed description of the Gamma Unit 150.

[0065] Figure 3 This is a diagram of the gamma unit of a display device according to an exemplary embodiment of the present disclosure. Figure 4 This is a waveform of the gamma unit of a display device according to an exemplary embodiment of the present disclosure; Figures 5A to 5C It is a schematic plan view of a display device used to illustrate the ratio of active pixels; Figure 6A and Figure 6B This is a view used to illustrate the operation of the gamma unit when the ratio of active pixels is higher than the ratio of reference pixels. Figure 7A and Figure 7B This is a view used to illustrate the operation of the gamma unit when the ratio of active pixels is lower than the ratio of reference pixels. Specifically, Figure 6A This is a flowchart illustrating the process of generating a gamma voltage VG using a second gamma reference voltage V2 in a display device 100 according to an exemplary embodiment of the present disclosure. Figure 6B This is a diagram of the gamma unit 150 of a display device 100 according to an exemplary embodiment of the present disclosure. Figure 7A This is a flowchart illustrating the process of generating a gamma voltage VG in a display device 100 using a first gamma reference voltage V1 according to an exemplary embodiment of the present disclosure. Figure 7B This is a diagram of the gamma unit 150 of a display device 100 according to an exemplary embodiment of the present disclosure.

[0066] Reference Figure 3 The gamma unit 150 includes a first gamma reference voltage generator 151, a second gamma reference voltage generator 152, a voltage setting unit 153, an output unit 154, and a gamma voltage generator 155.

[0067] Reference Figure 3The first gamma reference voltage generator 151 generates a first gamma reference voltage V1 based on a first external power supply AVDDH. At this time, the first gamma reference voltage V1 includes a first higher gamma reference voltage VREG1 and a first lower gamma reference voltage VREF1. The first gamma reference voltage generator 151 generates the first gamma reference voltage V1 based on the first external power supply AVDDH, such that a first gamma reference voltage V1 with a constant value can be generated regardless of the voltage drop of the high-potential power supply voltage VDDL. For example, even if the change in the feedback voltage VDDEL' increases, the first gamma reference voltage V1 can be maintained constant.

[0068] Refer to together Figure 4 When using the first gamma reference voltage V1, the waveform in the second time period T2 can be identified. The high-potential power voltage VDDEL changes when the on-pixel ratio (OPR) changes, that is, when the image to be displayed changes. However, the first gamma reference voltage V1, generated based on the first external power AVDDH, can be kept constant.

[0069] Meanwhile, the On-Phase Ratio (OPR) indicates the proportion of on-pixels in the entire pixel, which will be referred to below. Figures 5A to 5C To describe in more detail.

[0070] Reference Figure 3 The second gamma reference voltage generator 152 generates a second gamma reference voltage V2 based on the feedback voltage VDDEL' of the second external power VCIR and the high-potential power voltage VDDEL. The second gamma reference voltage V2 includes a second higher gamma reference voltage AVREG1 and a second lower gamma reference voltage AVREF1.

[0071] The feedback voltage VDDEL' of the high-potential power voltage VDDEL is the feedback voltage VDDEL' of the high-potential power voltage VDDEL applied to the display panel 110. The high-potential power voltage VDDEL supplied to the display panel 110 can vary due to voltage drop, and the varied high-potential power voltage VDDEL can be provided to the gamma unit 150 as the feedback voltage VDDEL'. Therefore, the second gamma reference voltage generator 152 reflects the voltage drop of the high-potential power voltage VDDEL to generate a second gamma reference voltage V2. Therefore, the second gamma reference voltage V2 generated considering the feedback voltage VDDEL' of the high-potential power voltage VDDEL can vary similarly to the high-potential power voltage VDDEL and can maintain a constant difference from the high-potential power voltage VDDEL. For example, when the change in the feedback voltage VDDEL' increases, the change in the second gamma reference voltage V2 can also increase.

[0072] When using the second gamma reference voltage V2, the gamma voltage VG and data voltage Vdata generated by the second gamma reference voltage V2 can also be coupled to the high-potential power voltage VDDEL. This minimizes the brightness variation caused by the voltage drop across the high-potential power voltage VDDEL. Specifically, as shown in Equation 1, the drive current I... OLED It can be determined by the high-potential power voltage VDDEL and the data voltage Vdata. However, even though the high-potential power voltage VDDEL varies according to its voltage drop, the second gamma reference voltage V2 and the data voltage Vdata generated by the second gamma reference voltage V2 are also coupled to the high-potential power voltage VDDEL. Therefore, the drive current I caused by the change in the high-potential power voltage VDDEL can be... OLED Therefore, the second gamma reference voltage V2 is used to minimize the change in brightness caused by the voltage drop of the high-potential power voltage VDDEL.

[0073] For example, refer to together Figure 4 When using the second gamma reference voltage V2, the waveform in the first time period T1 can be identified. As the ratio of on-pixels and the image to be displayed change, the high-potential power voltage VDDEL changes, and the second gamma reference voltage V2 generated based on the feedback voltage VDDEL' of the high-potential power voltage VDDEL can vary similarly to the high-potential power voltage VDDEL.

[0074] Meanwhile, the first external power VDDH and the second external power VCIR supplied to the first gamma reference voltage generator 151 and the second gamma reference voltage generator 152 respectively can be provided from the power supply unit 140 or from another configuration outside the display device 100. However, it is not limited to this.

[0075] Refer again Figure 3 The gamma voltage generator 155 can generate multiple gamma voltages VG based on a first gamma reference voltage V1 from a first gamma reference voltage generator 151 or a second gamma reference voltage V2 from a second gamma reference voltage generator 152. For example, the gamma voltage generator 155 divides the voltage between a first higher gamma reference voltage VREG1 and a first lower gamma reference voltage VREF1 to generate multiple gamma voltages VG corresponding to each of all individual grayscale values. Furthermore, the gamma voltage generator 155 divides the voltage between a second higher gamma reference voltage AVREG1 and a second lower gamma reference voltage AVREF1 to generate multiple gamma voltages VG corresponding to each of all individual grayscale values.

[0076] The voltage setting unit 153 selectively connects one of the first gamma reference voltage generator 151 and the second gamma reference voltage generator 152 to the gamma voltage generator 155. The voltage setting unit 153 is connected between the first gamma reference voltage generator 151 and the gamma voltage generator 155, and between the second gamma reference voltage generator 152 and the gamma voltage generator 155, so that only either the first gamma reference voltage generator 151 or the second gamma reference voltage generator 152 is connected to the gamma voltage generator 155. For example, the voltage setting unit 153 may be configured to include a switch connected between each of the first gamma reference voltage generator 151 and the gamma voltage generator 155, and between the second gamma reference voltage generator 152 and the gamma voltage generator 155, but is not limited thereto.

[0077] Output unit 154 outputs either a first gamma reference voltage V1 from the first gamma reference voltage generator 151 or a second gamma reference voltage V2 from the second gamma reference voltage generator 152 to gamma voltage generator 155. Output unit 154 is connected between voltage setting unit 153 and gamma voltage generator 155. When the first gamma reference voltage generator 151 and the second gamma reference voltage generator 152 switch between each other, output unit 154 gradually changes and outputs the first gamma reference voltage V1 and the second gamma reference voltage V2. For example, when voltage setting unit 153 separates the first gamma reference voltage generator 151 from gamma voltage generator 155, but connects the second gamma reference voltage generator 152 to gamma voltage generator 155, output unit 154 gradually changes the initial second gamma voltage VG for N frames to output the second gamma reference voltage V2.

[0078] Meanwhile, the voltage setting unit 153 selectively connects one of the first gamma reference voltage generator 151 and the second gamma reference voltage generator 152 to the gamma voltage generator 155 according to the on-pixel ratio (OPR).

[0079] Reference Figures 5A to 5C The activated pixel ratio represents the percentage of pixels out of a set that are activated to emit white light. For example, as... Figure 5A As shown, when all pixels are turned on to emit white light, the ratio of turned-on pixels can be 100%. Furthermore, as... Figure 5B and Figure 5C As shown, when only some pixels are turned on to emit white light, the ratio of turned-on pixels can be 80% and 20%.

[0080] In the following text, reference will be made to Figures 6A to 7B Describe the process of generating gamma voltage VG based on the ratio of active pixels.

[0081] Reference Figure 6A and Figure 6B When the active pixel ratio is higher than the reference pixel ratio (S110), the voltage setting unit 153 separates the first gamma reference voltage generator 151 from the gamma voltage generator 155 and connects the second gamma reference voltage generator 152 to the gamma voltage generator 155 (S120). For example, when the active pixel ratio is higher than 10%, the voltage setting unit 153 can connect the second gamma reference voltage generator 152 to the gamma voltage generator 155.

[0082] At this time, when the first gamma reference voltage generator 151 and the second gamma reference voltage generator 152 switch between each other, screen flicker may occur due to the difference between the first gamma reference voltage V1 and the second gamma reference voltage V2. The first gamma reference voltage V1 is generated based on the first external power AVDDH, and the second gamma reference voltage V2 is generated based on the feedback voltage VDDEL' of the high-potential power voltage VDDEL. Therefore, even in the same image, the first gamma reference voltage V1 and the second gamma reference voltage V2 can be different. Furthermore, the target brightness corresponding to each of the first gamma reference voltage V1 and the second gamma reference voltage V2 can be different.

[0083] For example, refer to Figure 4 When comparing the interval where the pixel ratio is 30% in the second time period T2 using the first gamma reference voltage V1 and the interval where the pixel ratio is 30% in the first time period T1 using the second gamma reference voltage V2, it can be confirmed that even with the same pixel ratio of 30%, the first gamma reference voltage V1 and the second gamma reference voltage V2 are different. Furthermore, because the first gamma reference voltage V1 and the second gamma reference voltage V2 are different, the data voltage Vdata generated based on the first gamma reference voltage V1 and the second gamma reference voltage V2, and the brightness of the displayed image, are also different.

[0084] Therefore, when the gamma reference voltage supplied to the gamma voltage generator 155 changes from the first gamma reference voltage V1 to the second gamma reference voltage V2 or from the second gamma reference voltage V2 back to the first gamma reference voltage V1, screen flicker may occur due to the sudden change in voltage and target brightness. Therefore, as the first gamma reference voltage V1 and the second gamma reference voltage V2 switch between each other, the output unit 154 gradually changes the gamma reference voltage to supply a gamma reference voltage to the gamma voltage generator 155.

[0085] Specifically, refer to Figure 6BWhen the voltage setting unit 153 separates the first gamma reference voltage generator 151 from the gamma voltage generator 155 and connects the second gamma reference voltage generator 152 to the gamma voltage generator 155, the output unit 154 outputs an initial second gamma reference voltage V2' (S130). The initial second gamma reference voltage V2' includes an initial second higher gamma reference voltage AVREG1' and an initial second lower gamma reference voltage AVREF1'. The initial second gamma reference voltage V2' has the same target brightness as the first gamma reference voltage V1, and the initial second gamma reference voltage V2' and the first gamma reference voltage V1 can display an image with the same brightness. In this case, the display device 100 is pre-tested to detect the initial second gamma reference voltage V2' according to the first gamma reference voltage V1, which achieves an image with the same brightness as the image displayed on the display panel 110.

[0086] Next, output unit 154 gradually increases or decreases the initial second gamma reference voltage V2' over N frames to output the second gamma reference voltage V2 (S140). In the first frame after connecting the second gamma reference voltage generator 152 and the gamma voltage generator 155, output unit 154 converts the second gamma reference voltage V2 provided from the second gamma reference voltage generator 152 to output the initial second gamma reference voltage V2'. Next, in subsequent frames, output unit 154 gradually increases or decreases the initial second gamma reference voltage V2' to approach the second gamma reference voltage V2, thereby outputting the initial second gamma reference voltage V2'. In the Nth frame (e.g., the fourth frame), the second gamma reference voltage V2 can finally be output. Therefore, output unit 154 gradually outputs the initial second gamma reference voltage V2' to the second gamma reference voltage V2 to the gamma voltage generator 155 during the Nth frame.

[0087] For example, refer to Figure 6B Given a second higher gamma reference voltage AVREG1 under the second gamma reference voltage V2, in the first frame, an initial second higher gamma reference voltage AVREG1' can be output to the gamma voltage generator 155. The initial second higher gamma reference voltage AVREG1' is gradually increased or decreased during the Nth frame to eventually output the second higher gamma reference voltage AVREG1 to the gamma voltage generator 155.

[0088] Even if not in Figure 6BAs shown, the second lower gamma reference voltage AVREF1 of the second gamma reference voltage V2 can also be output to the gamma voltage generator 155 in the same manner as the second higher gamma reference voltage AVREG1. For example, in the first frame connected to the second gamma reference voltage generator 152, the initial second lower gamma reference voltage AVREF1' is output to the gamma voltage generator 155. During the Nth frame, the initial second gamma reference voltage AVREF1' is gradually increased or decreased to eventually output the second lower gamma reference voltage AVREF1 to the gamma voltage generator 155.

[0089] At the same time, despite Figure 6B The diagram shows that the Nth frame is the fourth frame, but the number of frames in which the initial second gamma reference voltage V2' is gradually changed to output the second gamma reference voltage V2 is not limited to this.

[0090] At this time, the output unit 154 may be configured by elements such as regulators to gradually change and output the second gamma reference voltage V2 from the second gamma reference voltage generator 152, but is not limited thereto.

[0091] Reference Figure 7A and Figure 7B When the active pixel ratio is lower than the reference pixel ratio (S210), the voltage setting unit 153 separates the second gamma reference voltage generator 152 from the gamma voltage generator 155, but connects the first gamma reference voltage generator 151 to the gamma voltage generator 155 (S220). For example, when the active pixel ratio is lower than 10%, the voltage setting unit 153 can connect the first gamma reference voltage generator 151 to the gamma voltage generator 155.

[0092] The first gamma reference voltage V1 is generated from the first external power supply AVDDH and is independent of the high-potential power voltage VDDEL. The gamma voltage VG and data voltage Vdata generated using the first gamma reference voltage V1 are unaffected by changes in the high-potential power voltage VDDEL. In this case, the data voltage Vdata does not change along with the high-potential power voltage VDDEL, thereby increasing the voltage difference between the data voltage Vdata and the high-potential power voltage VDDEL based on the first gamma reference voltage V1, and also increasing the drive current I. OLED And brightness. In other words, the second gamma reference voltage V2, coupled to the high-potential power voltage VDDEL, minimizes the change in brightness according to changes in the high-potential power voltage VDDEL. In contrast, the first gamma reference voltage V1, not coupled to the high-potential power voltage VDDEL, maximizes the change in brightness according to changes in the high-potential power voltage VDDEL.

[0093] In images where the on-pixel ratio using the first gamma reference voltage V1 is 10% or lower, most pixels are off pixels, which are represented as black. Using the first gamma reference voltage V1 increases the brightness of the on-pixels compared to using the second gamma reference voltage V2, and also increases the contrast between the on-pixels and off-pixels (i.e., the contrast between black and white). Therefore, when the on-pixel ratio is lower than the reference pixel ratio, for example, the first gamma reference voltage V1 is used to maximize brightness variation and enhance black-and-white contrast.

[0094] When the voltage setting unit 153 separates the second gamma reference voltage generator 152 from the gamma voltage generator 155 and connects the first gamma reference voltage generator 151 and the gamma voltage generator 155, the output unit 154 outputs an initial first gamma reference voltage V1' (S230). The initial first gamma reference voltage V1' includes an initial first higher gamma reference voltage VREG1' and an initial first lower gamma reference voltage VREF1'. The initial first gamma reference voltage V1' is the voltage value for displaying an image with the same brightness as the second gamma reference voltage V2. In this case, the display device 100 is pre-tested to detect the initial first gamma reference voltage V1' according to the second gamma reference voltage V2, which achieves an image with the same brightness as the image displayed on the display panel 110.

[0095] Next, the output unit 154 gradually changes the initial first gamma reference voltage V1' during N frames to output the first gamma reference voltage V1 (S240). For example, in the first frame after connecting the first gamma reference voltage generator 151 and the gamma voltage generator 155, the output unit 154 switches the first gamma reference voltage V1 provided from the first gamma reference voltage generator 151 to output the initial first gamma reference voltage V1'. Next, in subsequent frames, the output unit 154 gradually switches the first gamma reference voltage V1' to approach the first gamma reference voltage V1, thereby outputting the initial first gamma reference voltage V1'. Finally, in the Nth frame (e.g., in the fourth frame), the first gamma reference voltage V1 can be finally output. Therefore, the output unit 154 can gradually output the initial first gamma reference voltage V1' to the first gamma reference voltage V1 to the gamma voltage generator 155 during the Nth frame.

[0096] For example, refer to Figure 7BGiven a first higher gamma reference voltage VREG1 of the first gamma reference voltage V1, in the first frame, the initial first higher gamma reference voltage VREG1' can be output to the gamma voltage generator 155. The initial first higher gamma reference voltage VREG1' gradually increases or decreases during the Nth frame to eventually output the first higher gamma reference voltage VREG1 to the gamma voltage generator 155.

[0097] Even in Figure 7B As not shown, the first lower gamma reference voltage VREF1 of the first gamma reference voltage V1 can also be output to the gamma voltage generator 155 in the same manner as the first higher gamma reference voltage VREG1. For example, in the first frame connected to the first gamma reference voltage generator 151, the initial first lower gamma reference voltage VREF1' is output to the gamma voltage generator 155. During the Nth frame, the initial first lower gamma reference voltage VREF1' is gradually increased or decreased to eventually output the first lower gamma reference voltage VREF1 to the gamma voltage generator 155.

[0098] Meanwhile, the accompanying drawings describe how the output unit 154 modifies the first gamma reference voltage V1 to output an initial first gamma reference voltage V1' to the first gamma reference voltage V1, and modifies the second gamma reference voltage V2 to output an initial second gamma reference voltage V2' to the second gamma reference voltage V2. However, the voltage setting unit 153 can output an initial first gamma reference voltage V1' to the first gamma reference voltage V1, and can output an initial second gamma reference voltage V2' to the second gamma reference voltage V2, but is not limited thereto.

[0099] Therefore, in the display device 100 according to an exemplary embodiment of this disclosure, the use of a first gamma reference voltage V1 or a second gamma reference voltage V2 is selected based on the displayed image. Firstly, in the case of the first gamma reference voltage V1, the first gamma reference voltage V1 is a voltage generated based on a first external power supply AVDDH, which has a constant value and is independent of changes in the high-potential power voltage VDDEL. When the sub-pixel SP includes the first to sixth transistors T6 and the driving transistor DT, the driving current I flowing in the light-emitting element EL... OLEDThe data voltage Vdata and the high-potential power voltage VDDEL can be determined. Therefore, when using the first gamma reference voltage V1, the voltage difference between the data voltage Vdata and the high-potential power voltage VDDEL based on the first gamma reference voltage V1 can be increased further, maximizing the brightness variation. Therefore, in images with a low on-pixel ratio, the first gamma reference voltage V1 is used to enhance black-and-white contrast. In the case of the second gamma reference voltage V2, the second gamma reference voltage V2, which is the voltage generated as the feedback voltage VDDEL' based on the high-potential power voltage VDDEL, and the data voltage Vdata generated therefrom can vary in the same way as the high-potential power voltage VDDEL. Therefore, the second gamma reference voltage V2 is used for images with a high on-pixel ratio to minimize the brightness degradation caused by the voltage drop of the high-potential power voltage VDDEL. Therefore, in the display device 100 according to an exemplary embodiment of the present disclosure, the first gamma reference voltage V1 and the second gamma reference voltage V2 are selectively used according to the characteristics of the image to improve the quality of the displayed image.

[0100] In a display device 100 according to an exemplary embodiment of the present disclosure, the gamma reference voltage provided to the gamma voltage generator 155 is gradually changed according to sudden voltage changes to minimize screen flicker. When the first gamma reference voltage V1 and the second gamma reference voltage V2 are changed and used, the contrast between black and white can be enhanced in images with a low on-pixel ratio, and the brightness degradation caused by the voltage drop of the high-potential power voltage VDDEL can be minimized in images with a high on-pixel ratio. However, even in environments with the same on-pixel ratio, the first gamma reference voltage V1 is based on the voltage of the first external power AVDDH, and the second gamma reference voltage V2 is based on the voltage of the feedback voltage VDDEL' of the high-potential power voltage VDDEL, thus there may be differences in voltage and brightness. In this case, when the first gamma reference voltage V1 and the second gamma reference voltage V2 switch directly to each other, the voltage and target brightness change drastically, causing screen flicker. Therefore, when the first gamma reference voltage V1 is switched to the second gamma reference voltage V2, an initial second gamma reference voltage V2' that achieves the brightness corresponding to the first gamma reference voltage V1 is provided to the gamma voltage generator 155. Furthermore, the initial second gamma reference voltage V2' can be gradually changed during the Nth frame. Therefore, finally, in the Nth frame, the second gamma reference voltage V2 can be provided to the gamma voltage generator 155, and errors caused by sudden voltage changes can be minimized. Furthermore, when the second gamma reference voltage V2 is switched to the first gamma reference voltage V1, an initial first gamma reference voltage V1' that achieves the brightness corresponding to the second gamma reference voltage V2 is provided to the gamma voltage generator 155. Furthermore, the initial first gamma reference voltage V1' can be gradually changed during the Nth frame. Therefore, finally, in the Nth frame, the first gamma reference voltage V1 is provided to the gamma voltage generator 155, and errors caused by sudden voltage changes can be minimized. Therefore, in the display device 100 according to an exemplary embodiment of the present disclosure, when the first gamma reference voltage V1 and the second gamma reference voltage V2 switch with each other, the gamma reference voltage output to the gamma voltage generator 155 gradually changes to be output. Thus, flickering and target brightness variations caused by sudden voltage changes can be minimized.

[0101] Exemplary implementations of this disclosure can also be described as follows:

[0102] According to one aspect of this disclosure, a display device is provided. The display device includes: a gamma unit, the gamma unit including a gamma reference voltage generator for generating a plurality of gamma reference voltages and a gamma voltage generator for generating a gamma voltage based on the gamma reference voltages; a data driver for generating a data voltage based on the gamma voltages; and a display panel electrically connected to the data driver. The gamma reference voltage generator includes: a first gamma reference voltage generator for generating a first gamma reference voltage among the plurality of gamma reference voltages based on external power; and a second gamma reference voltage generator for generating a second gamma reference voltage among the plurality of gamma reference voltages based on a feedback voltage from a high-potential power voltage from the display panel.

[0103] The display panel may include multiple pixels, and when the active pixel ratio (OPR), which represents the ratio of active pixels among the multiple pixels, is lower than the reference pixel ratio, a first gamma reference voltage can be output from a first gamma reference voltage generator to a gamma voltage generator.

[0104] When the ratio of active pixels is higher than the ratio of reference pixels, the second gamma reference voltage can be output from the second gamma reference voltage generator to the gamma voltage generator.

[0105] The gamma unit may further include: a voltage setting unit that selectively connects one of the first gamma reference voltage generator and the second gamma reference voltage generator to the gamma voltage generator; and an output unit between the voltage setting unit and the gamma voltage generator, wherein the output unit may gradually change the first gamma reference voltage or the second gamma reference voltage to output the changed voltage to the gamma voltage generator.

[0106] When the second gamma reference voltage generator is separated from the gamma voltage generator through the voltage setting unit and the first gamma reference voltage generator is connected to the gamma voltage generator, the output unit can output an initial first gamma reference voltage corresponding to the second gamma reference voltage in the initial frame, and gradually change the initial first gamma reference voltage during the Nth frame to output the first gamma reference voltage.

[0107] When the first gamma reference voltage generator is separated from the gamma voltage generator through the voltage setting unit and the second gamma reference voltage generator is connected to the gamma voltage generator, the output unit can output an initial second gamma reference voltage corresponding to the first gamma reference voltage in the initial frame, and gradually change the initial second gamma reference voltage during the Nth frame to output the second gamma reference voltage.

[0108] When the change in feedback voltage increases, the change in the second gamma reference voltage can also increase.

[0109] When the change in feedback voltage increases, the first gamma reference voltage can remain constant.

[0110] According to another aspect of this disclosure, a display device is provided. The display device includes: a gamma unit, the gamma unit including a first gamma reference voltage generator for generating a first gamma reference voltage, a second gamma reference voltage generator for generating a second gamma reference voltage, and a gamma voltage generator for generating a gamma voltage based on the first gamma reference voltage or the second gamma reference voltage; a data driver for generating a data voltage based on the gamma voltage; and a display panel including a plurality of pixels driven by a high-potential electrical voltage and the data voltage. When an active pixel ratio, representing the ratio of active pixels among the plurality of pixels, is lower than a reference pixel ratio, the gamma reference voltage generator generates a gamma voltage based on the first gamma reference voltage; and when the active pixel ratio is higher than the reference pixel ratio, the gamma voltage generator generates a gamma voltage based on the second gamma reference voltage.

[0111] The first gamma reference voltage generator can generate a first gamma reference voltage with a constant value based on external power.

[0112] The second gamma reference voltage can be coupled to a feedback voltage from the high-potential power voltage of the display panel.

[0113] The gamma unit may further include: a voltage setting unit connected between the first gamma reference voltage generator and the gamma voltage generator and between the second gamma reference voltage generator and the gamma voltage generator; and an output unit connected between the voltage setting unit and the gamma voltage generator, wherein the voltage setting unit may connect either the first gamma reference voltage generator or the second gamma reference voltage generator to the output unit and the gamma voltage generator.

[0114] When the voltage setting unit separates the second gamma reference voltage generator from the output unit and connects the first gamma reference voltage generator to the output unit, the output unit can gradually change the initial first gamma reference voltage frame by frame, so as to send the first gamma reference voltage to the gamma voltage generator after N frames. Furthermore, the image displayed on the display panel based on the initial first gamma reference voltage and the image displayed on the display panel based on the second gamma reference voltage can have the same brightness.

[0115] When the voltage setting unit separates the first gamma reference voltage generator from the output unit and connects the second gamma reference voltage generator to the output unit, the output unit can gradually change the initial second gamma reference voltage in frames so that the second gamma reference voltage is sent to the gamma voltage generator after the Nth frame. The image displayed on the display panel based on the initial second gamma reference voltage and the image displayed on the display panel based on the first gamma reference voltage can have the same brightness.

[0116] Although exemplary embodiments of this disclosure have been described in detail with reference to the accompanying drawings, this disclosure is not limited thereto and can be implemented in many different forms without departing from the technical concept of this disclosure. Therefore, the exemplary embodiments of this disclosure are provided for illustrative purposes only and are not intended to limit the technical concept of this disclosure. The scope of the technical concept of this disclosure is not limited thereto. Therefore, it should be understood that the above exemplary embodiments are illustrative in all respects and do not limit this disclosure. The scope of protection of this disclosure should be interpreted based on the following claims, and all technical concepts within their equivalents should be interpreted as falling within the scope of this disclosure.

Claims

1. A display device, comprising: A gamma unit, the gamma unit comprising: a gamma reference voltage generator for generating a plurality of gamma reference voltages; and a gamma voltage generator for generating gamma voltages based on the gamma reference voltages; A data driver that generates a data voltage based on the gamma voltage; and The display panel includes a plurality of pixels and is electrically connected to the data driver. The gamma reference voltage generator includes: A first gamma reference voltage generator that generates the first gamma reference voltage from the plurality of gamma reference voltages based on external power; and A second gamma reference voltage generator generates a second gamma reference voltage from among the plurality of gamma reference voltages based on a feedback voltage from a high-potential power voltage from the display panel. The gamma unit further includes: A voltage setting unit selectively connects one of the first gamma reference voltage generator and the second gamma reference voltage generator to the gamma voltage generator based on a comparison between an on-pixel ratio representing the ratio of on-pixels among the plurality of pixels and a reference pixel ratio.

2. The display device according to claim 1, wherein When the active pixel ratio is lower than the reference pixel ratio, the voltage setting unit connects the first gamma reference voltage generator to the gamma voltage generator.

3. The display device according to claim 2, wherein When the ratio of active pixels is higher than the ratio of reference pixels, the voltage setting unit connects the second gamma reference voltage generator to the gamma voltage generator.

4. The display device according to claim 1, wherein The gamma unit also includes: The output unit between the voltage setting unit and the gamma voltage generator, and The output unit gradually changes the first gamma reference voltage or the second gamma reference voltage to output the changed voltage to the gamma voltage generator.

5. The display device of claim 4, wherein, When the second gamma reference voltage generator is separated from the gamma voltage generator through the voltage setting unit, and the first gamma reference voltage generator is connected to the gamma voltage generator, the output unit outputs an initial first gamma reference voltage corresponding to the second gamma reference voltage in the initial frame, and gradually changes the initial first gamma reference voltage during the Nth frame to output the first gamma reference voltage.

6. The display device according to claim 4, wherein When the first gamma reference voltage generator is separated from the gamma voltage generator through the voltage setting unit, and the second gamma reference voltage generator is connected to the gamma voltage generator, the output unit outputs an initial second gamma reference voltage corresponding to the first gamma reference voltage in the initial frame, and gradually changes the initial second gamma reference voltage during the Nth frame to output the second gamma reference voltage.

7. The display device according to claim 1, wherein When the change in feedback voltage increases, the change in the second gamma reference voltage also increases.

8. The display device according to claim 1, wherein The first gamma reference voltage remains constant as the change in feedback voltage increases.

9. A display device, comprising: A gamma unit, the gamma unit comprising: a first gamma reference voltage generator for generating a first gamma reference voltage; a second gamma reference voltage generator for generating a second gamma reference voltage; and a gamma voltage generator for generating a gamma voltage based on the first gamma reference voltage or the second gamma reference voltage; A data driver that generates a data voltage based on the gamma voltage; and The display panel includes a plurality of pixels driven by a high-potential electrical voltage and the data voltage. Specifically, when the ratio of active pixels, which represents the ratio of active pixels among the plurality of pixels, is lower than the reference pixel ratio, the gamma voltage generator generates the gamma voltage based on the first gamma reference voltage; and when the ratio of active pixels is higher than the reference pixel ratio, the gamma voltage generator generates the gamma voltage based on the second gamma reference voltage.

10. The display device of claim 9, wherein, The first gamma reference voltage generator generates a first gamma reference voltage with a constant value based on external power.

11. The display device of claim 9, wherein, The second gamma reference voltage is coupled to a feedback voltage from the high-potential power voltage of the display panel.

12. The display device of claim 9, wherein, The gamma unit also includes: A voltage setting unit connected between the first gamma reference voltage generator and the gamma voltage generator, and between the second gamma reference voltage generator and the gamma voltage generator; and An output unit connected between the voltage setting unit and the gamma voltage generator, and The voltage setting unit connects either the first gamma reference voltage generator or the second gamma reference voltage generator to the output unit and the gamma voltage generator.

13. The display device of claim 12, wherein, When the voltage setting unit separates the second gamma reference voltage generator from the output unit and connects the first gamma reference voltage generator to the output unit, the output unit gradually changes the initial first gamma reference voltage frame by frame, so as to send the first gamma reference voltage to the gamma voltage generator after the Nth frame, and The image displayed on the display panel based on the initial first gamma reference voltage and the image displayed on the display panel based on the second gamma reference voltage have the same brightness.

14. The display device of claim 13, wherein, When the voltage setting unit separates the first gamma reference voltage generator from the output unit and connects the second gamma reference voltage generator to the output unit, the output unit gradually changes the initial second gamma reference voltage frame by frame, so as to send the second gamma reference voltage to the gamma voltage generator after the Nth frame. The image displayed on the display panel based on the initial second gamma reference voltage has the same brightness as the image displayed on the display panel based on the first gamma reference voltage.

15. A gamma unit for a display panel comprising a plurality of pixels, comprising: A gamma reference voltage generator that generates multiple gamma reference voltages; as well as A gamma voltage generator that generates a gamma voltage based on the gamma reference voltage. The gamma reference voltage generator includes: A first gamma reference voltage generator that generates the first gamma reference voltage from the plurality of gamma reference voltages based on external power; and A second gamma reference voltage generator generates a second gamma reference voltage from among the plurality of gamma reference voltages based on a feedback voltage from a high-potential power voltage from the display panel. The gamma unit further includes: A voltage setting unit selectively connects one of the first gamma reference voltage generator and the second gamma reference voltage generator to the gamma voltage generator based on a comparison of an on-pixel ratio, which represents the ratio of on-pixels among the plurality of pixels, and a reference pixel ratio.

16. The gamma cell of claim 15, wherein, When the active pixel ratio is lower than the reference pixel ratio, the voltage setting unit connects the first gamma reference voltage generator to the gamma voltage generator, and When the ratio of active pixels is higher than the ratio of reference pixels, the voltage setting unit connects the second gamma reference voltage generator to the gamma voltage generator.

17. The gamma unit according to claim 15, further comprising: The output unit between the voltage setting unit and the gamma voltage generator The output unit gradually changes the first gamma reference voltage or the second gamma reference voltage to output the changed voltage to the gamma voltage generator.

Images