Display driver IC including dithering circuit capable of adaprively changing threshold grayscale value according to display brightness value, device including same, and method thereof

Abstract

A display driver IC is disclosed that includes a dithering circuit capable of adaptively changing a threshold grayscale value according to a display brightness value. The display driver IC includes a data line driver that drives a first data line connected to a first pixel of a display in response to output image data, and a dithering circuit that receives a brightness value of the display, calculates a first reference grayscale value corresponding to the brightness value using a first group of threshold grayscale values, receives input image data having a first grayscale value corresponding to the first pixel, compares the first grayscale value with the first reference grayscale value, and generates the output image data having an output grayscale value instead of the first grayscale value when the first grayscale value is smaller than the first reference grayscale value.

Description

Technology Field

[0001] An embodiment according to the concept of the present invention relates to a dithering technology, and in particular to a display driver IC including a dithering circuit capable of adaptively changing a threshold grayscale value according to a display brightness value, an apparatus including said display driver IC, and a dithering method. Background Technology

[0002] Various types of flat panel displays have been developed. Examples of flat panel displays include liquid crystal displays, field emission displays, plasma displays, and organic light-emitting displays. Organic light-emitting displays are lighter, thinner, have a wider viewing angle, faster response time, and lower power consumption compared to other displays.

[0003] In organic light-emitting displays, images are generated based on light emitted from organic light-emitting diodes. Each organic light-emitting diode emits light based on the recombination of electrons and holes in the emission layer. The amount of emitted light varies depending on the amount of current flowing through the organic light-emitting diode. When a low-grayscale image is displayed in an organic light-emitting display, mura occurs in the low-grayscale image because it is difficult to finely control the current driving each organic light-emitting diode.

[0004] A dithering algorithm was used to improve the blotches occurring in low-gradation images. The problem to be solved

[0005] The technical problem that the present invention aims to solve is to provide a display driver IC including a dithering circuit capable of adaptively changing a threshold grayscale value according to a display brightness value to remove or improve stains occurring in low-grayscale images, an apparatus including the same, and a method thereof. means of solving the problem

[0006] A display driver IC according to the present invention comprises a data line driver that drives a first data line connected to a first pixel of a display in response to output image data, and a dithering circuit that receives a brightness value of the display, calculates a first reference grayscale value corresponding to the brightness value using threshold grayscale values ​​of a first group, receives input image data having a first grayscale value corresponding to the first pixel, compares the first grayscale value with the first reference grayscale value, and generates the output image data having an output grayscale value instead of the first grayscale value when the first grayscale value is smaller than the first reference grayscale value. The dithering circuit selects one of the threshold grayscale values ​​of the first group as the output grayscale value.

[0007] The dithering circuit further calculates a second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of the first group, further compares the first grayscale value with the second reference grayscale value, and when the first grayscale value is greater than the second reference grayscale value and smaller than the first reference grayscale value, selects one of the threshold grayscale values ​​of the first group and the minimum grayscale values ​​of the first group as the output grayscale value.

[0008] A display device according to the present invention comprises a display including a first data line connected to a first pixel and a display driver IC for driving the first data line, wherein the display driver IC comprises a data line driver for driving the first data line in response to output image data, a reference grayscale value calculation circuit for receiving a brightness value of the display and calculating a first reference grayscale value corresponding to the brightness value using threshold grayscale values ​​of a first group, and a threshold grayscale value change circuit for receiving input image data having a first grayscale value corresponding to the first pixel, comparing the first grayscale value with the first reference grayscale value, changing the first grayscale value to an output grayscale value when the first grayscale value is smaller than the first reference grayscale value, and generating the output image data having the output grayscale value, wherein the output grayscale value is any one of the threshold grayscale values ​​of the first group.

[0009] According to the present invention, a method of operating an IC of a display driver for dithering comprises the steps of: receiving a brightness value of a display and calculating a first reference grayscale value corresponding to the brightness value using threshold grayscale values ​​of a first group; receiving input image data having a first grayscale value and comparing the first grayscale value with the first reference grayscale value; changing the first grayscale value to an output grayscale value when the first grayscale value is smaller than the first reference grayscale value; and driving a first data line connected to a first pixel placed on the display using output image data having the output grayscale value. Effects of the invention

[0010] A display driver IC according to an embodiment of the present invention, an apparatus including the same, and a dithering method can adaptively change a threshold grayscale value according to a display brightness value, thereby having the effect of removing or improving stains occurring in low-grayscale images. Brief explanation of the drawing

[0011] Detailed descriptions of each drawing are provided to help to more fully understand the drawings cited in the detailed description of the present invention. FIG. 1 is a block diagram of a display device including a dithering circuit according to an embodiment of the present invention. FIG. 2 is a block diagram showing an example of the dithering circuit illustrated in FIG. 1. FIG. 3 is an example for explaining the process by which the reference grayscale value calculation circuit illustrated in FIG. 2 determines the first reference grayscale value. Figure 4 is an example of input image data and output image data to explain the operation of the dithering circuit illustrated in Figure 1. FIG. 5 is a block diagram showing an example of the dithering circuit illustrated in FIG. 1. Figure 6 is an example showing the relationship between a count value and a threshold grayscale value to explain the operation of the threshold grayscale value calculation circuit shown in Figure 5. FIG. 7 is a block diagram showing an example of the dithering circuit illustrated in FIG. 1. FIG. 8 is an example for explaining the process by which the reference grayscale value calculation circuit illustrated in FIG. 7 determines a first reference grayscale value and a first reference grayscale value. FIG. 9 is a block diagram showing an example of the dithering circuit illustrated in FIG. 1. FIG. 10 is an example showing the relationship between a count value and a threshold grayscale value to explain the operation of the threshold grayscale value calculation circuit shown in FIG. 9. FIG. 11 is a block diagram showing an example of a dithering circuit illustrated in FIG. 1. FIG. 12 is a flowchart illustrating the operation of a dithering circuit according to an embodiment of the present invention. FIG. 13 is a figure illustrating the operation of a dithering circuit when changing from a first display brightness value to a third display brightness value according to an embodiment of the present invention. Specific details for implementing the invention

[0012] The threshold grayscale value described herein refers to the lowest grayscale value at which no mura appears in an image displayed on an OLED display comprising Organic Light Emitting Diodes (OLEDs).

[0013] The grayscale value (also called the 'grayscale level') indicates the brightness of a pixel. The grayscale value is also called the gray value. The minimum grayscale value is zero, and the maximum grayscale value depends on the digitization depth of the image. For example, in an 8-bit-depth image, the maximum grayscale value is 255.

[0014] Each minimum grayscale value (MIN1_1 and MIN1_3) shown in FIG. 8 may change according to the brightness value of the display, and each minimum grayscale value (MIN2_1, MIN2_2, and MIN2_3) shown in FIG. 10 may change according to the count value, so the corresponding minimum grayscale values ​​(MIN1_1, MIN1_3, MIN2_1, MIN2_2, and MIN2_3) may not be zero.

[0015] In this specification, the low gradation (or low gradation image) is assumed to be 0.8 nit (0.8 cd / m²), but the low gradation is not limited to 0.8 nit.

[0016] When the display brightness value decreases, the driving current of each pixel placed in the display (300) decreases, so the dithering circuit (210) of the present invention increases the threshold grayscale value in which no stains occur in the low-grayscale image displayed on the display (300).

[0017] FIG. 1 is a block diagram of a display device including a dithering circuit according to an embodiment of the present invention. Referring to FIG. 1, the display device (100) includes a display driver IC (display driver IC; 200), a display (also referred to as a 'display panel'; 300), an illuminance sensor (400), and a processor (processor; 500).

[0018] The display device (100) is a display device capable of displaying stains in low-gradation images, and may be a TV or a mobile device, and examples of the mobile device include a smartphone, a laptop computer, a mobile internet device (MID), and / or a wearable computer.

[0019] The display driver IC (200) can perform a dithering operation that adaptively (or automatically) changes a threshold grayscale value according to the brightness value (DBV) of the display (300), an operation that drives a plurality of data lines (Y1 to Yn, where n is a natural number greater than or equal to 4) included in the display (300), and an operation that drives a plurality of gate lines (X1 to Xm, where m is a natural number greater than or equal to 4). For example, the brightness value (DBV) of the display (300) may be a digital code containing a plurality of bits.

[0020] The display driver IC (200) includes a dithering circuit (210), a memory device (230), a gamma voltage generator (235), a data line driver (also called a 'source driver', 240), and a gate driver (250).

[0021] The operation of the dithering circuit (210) will be explained in detail with reference to FIGS. 2 to 13.

[0022] A memory device (230) stores multiple dither patterns (DP1 to DPu, where u is a natural number greater than or equal to 4), and each of the dither patterns (DP1 to DPu) is matched or mapped to each of different grayscale values. A dither pattern is also called a dither mask. For example, the memory device (230) may be a Static Random Access Memory (SRAM), but is not limited thereto.

[0023] The gamma voltage generator (235) generates multiple gamma voltages (GM1 to GMz, where z is a natural number greater than or equal to 2) and outputs them (GM1 to GMz) to the data line driver (240).

[0024] The data line driver (240) selects a corresponding gamma voltage from a plurality of gamma voltages (GM1 to GMz) in response to output image data (OUTi, i is a natural number greater than or equal to 2) having a specific grayscale value (e.g., a specific threshold grayscale value or a specific minimum grayscale value) output from the dithering circuit (210), and outputs a driving voltage corresponding to the selected gamma voltage to a corresponding data line among a plurality of data lines (also referred to as 'source lines', Y1 to Yn) included in the display (300).

[0025] The gate driver (250) can sequentially generate gate signals that drive a plurality of gate lines (X1~Xm) included in the display (300).

[0026] In FIG. 1, for convenience of explanation, one data line driver (240) and one gate driver (250) are shown, but according to embodiments, the data line driver (240) may collectively represent a plurality of data line drivers and the gate driver (250) may collectively represent a plurality of gate drivers.

[0027] Additionally, although the display driver IC (200) in FIG. 1 is shown as including both a data line driver (240) and a gate driver (250), according to embodiments, the gate driver (250) may be placed outside the display driver IC (200).

[0028] The display (300) includes a plurality of data lines (Y1~Yn), a plurality of gate lines (X1~Xm), and a plurality of pixels (PX) arranged in a matrix form, and each of the plurality of pixels (PX) is connected to each of the plurality of data lines (Y1~Yn) and each of the plurality of gate lines (X1~Xm).

[0029] Examples of displays (300) may be displays including organic light-emitting diodes or displays including liquid crystals.

[0030] An illuminance sensor (400) may be placed inside or outside the display (300), detects the brightness (or total brightness) of the display (300) to generate a detection signal, and outputs the detection signal to a processor (500). The processor (500) processes the detection signal to generate a display brightness value (DBV) corresponding to the brightness (or total brightness) of the display (300).

[0031] For example, to adjust the brightness of the display (300), the display driver IC (200) performs a dimming operation for the display (300) using gamma voltages generated by the gamma voltage generator (235). The light sensor (400) detects the brightness (or total brightness) of the display (300) adjusted according to the dimming operation and generates a detection signal, and the processor (500) generates a brightness value (DBV) of the display corresponding to the result of the dimming operation for the display (300) according to the detection signal.

[0032] Dimming refers to an operation that controls the brightness of light emitted from a diode included in a pixel (PX), and the brightness of light emitted from the diode can be controlled by a gamma voltage corresponding to the diode.

[0033] When the display device (100) is a smartphone, the processor (500) may be an application processor (AP). For example, the user of the smartphone may adjust the screen brightness of the smartphone using an automatic function or manually.

[0034] FIG. 2 is a block diagram showing an example of a dithering circuit illustrated in FIG. 1, and FIG. 3 is an example for explaining the process of a reference grayscale value calculation circuit illustrated in FIG. 2 determining a first reference grayscale value.

[0035] The dithering circuit (210A) of FIG. 2 includes a reference grayscale value calculation circuit (211A), a comparison circuit (213A), and a threshold grayscale value calculation circuit (215A). The dithering circuit (210A) of FIG. 2 is an embodiment of the dithering circuit (210) shown in FIG. 1.

[0036] The threshold grayscale value changing circuit includes a comparison circuit (213A or 213B) and a threshold grayscale value calculation circuit (215A, 215B, 215C, 215D, or 215E), and the threshold grayscale value changing circuit receives a first input image data (IID1) having a first grayscale value (GV1) corresponding to a first pixel (301), compares the first grayscale value (GV1) with a first reference grayscale value (HREF), changes the first grayscale value (GV1) to an output grayscale value when the first grayscale value (GV1) is smaller than the first reference grayscale value (HREF), and generates a first output image data (OUT1) having the output grayscale value. The output grayscale value is any one of the first group of threshold grayscale values ​​(TH1_1 and TH1_3).

[0037] The reference grayscale value calculation circuit (211A) may include a memory device that stores first information (TH_TB1) including first group threshold grayscale values ​​(TH1_1 and TH1_3) for display brightness values ​​(DBV1 and DBV3). The reference grayscale value calculation circuit (211A) receives a display brightness value (DBV) representing the brightness of the display (300) (e.g., the total brightness of the display (300)) from the processor (500), and calculates a first reference brightness value (HREF) corresponding to the display brightness value (DBV) using the first information (TH_TB1).

[0038] Each piece of information (TH_TB1~TH_TB6) described in this specification may be stored in a table format and may be input (or set) from an external source.

[0039] Figure 3 shows the relationship between the display brightness value (DBV) and the threshold grayscale value. As shown in Figure 3, when the display brightness value (DBV) decreases, the threshold grayscale value at which no blemishes occur in low-grayscale images increases. For example, when the display brightness value (DBV) changes, the gamma voltage also changes.

[0040] As exemplified in FIG. 3, assuming that when the display brightness value (DBV) is the first brightness value (DBV1), the threshold grayscale value is the first threshold grayscale value (TH1_1), and when the display brightness value (DBV) is the third brightness value (DBV3), the threshold grayscale value is the third threshold grayscale value (TH1_3), the reference grayscale value calculation circuit (211A) calculates the second threshold grayscale value (TH1_2) for the second brightness value (DBV2) using already known values ​​(DBV1, DBV3, TH1_1, and TH1_3), and outputs the second threshold grayscale value (TH1_2) as the first reference grayscale value (HREF) to the comparison circuit (213A).

[0041] For example, the reference grayscale value calculation circuit (211A) can calculate the second threshold grayscale value (TH1_2) for the second brightness value (DBV2) by interpolating the first threshold grayscale value (TH1_1) for the first brightness value (DBV1) and the third threshold grayscale value (TH1_3) for the third brightness value (DBV3).

[0042] For example, the reference grayscale value calculation circuit (211A) can calculate a second threshold grayscale value (TH1_2) for a second brightness value (DBV2) using a first graph (GRP1) of a straight line passing through two points ((DBV1, TH1_1) and (DBV3, TH1_3)).

[0043] The comparison circuit (213A) receives input image data (IIDi) having a grayscale value (GVi), compares the grayscale value (GVi) with a first reference grayscale value (HREF), and when the grayscale value (GVi) is equal to or greater than the first reference grayscale value (HREF), outputs (or bypasses) the input image data (IIDi) having the grayscale value (GVi) as output image data (OUTi) to the data line driver (240).

[0044] However, when the grayscale value (GVi) is smaller than the first reference grayscale value (HREF), the comparison circuit (213A) outputs the input image data (IIDi) having the grayscale value (GVi) to the threshold grayscale value calculation circuit (215A).

[0045] Figure 4 is an example of input image data and output image data to explain the operation of the dithering circuit illustrated in Figure 1.

[0046] Referring to FIGS. 1 and FIGS. 4, it is assumed that a first input image data (IID1) having a first grayscale value (GVi, i=1) corresponds to a first pixel (301), a second input image data (IID2) having a second grayscale value (GVi, i=2) corresponds to a second pixel (302), a third input image data (IID3) having a third grayscale value (GVi, i=3) corresponds to a third pixel (303), a fourth input image data (IID4) having a fourth grayscale value (GVi, i=4) corresponds to a fourth pixel (304), and each grayscale value (GV1, GV3, and GV4) is smaller than a first reference grayscale value (HREF), and a second grayscale value (GV2) is equal to or greater than a first reference grayscale value (HREF).

[0047] 2*2 input image data (IID1~IID4) is part of one frame input image data, and 2*2 output image data (OUT1~OUT4) is part of one frame output image data.

[0048] Since the first grayscale value (GV1) is smaller than the first reference grayscale value (HREF), the comparison circuit (213A) transmits the first input image data (IID1) having the first grayscale value (GV1) to the threshold grayscale value calculation circuit (215A).

[0049] The threshold grayscale value calculation circuit (215A) obtains a first dither pattern (DPj, j=1, 1≤j≤u) corresponding to the first grayscale value (GV1) from the memory device (230) by referring to the lookup table (LUT) stored therein (this is also called 'read').

[0050] When the processing unit (PU) illustrated in FIG. 1 includes 2*2 pixels (301, 302, 303, and 304), each dither pattern (DP1, DP3, and DP4) illustrated in FIG. 4 is a 2*2 data matrix.

[0051] Each dither pattern (DP1, DP3, and DP4) includes at least one first data element having a first value and at least one second data element having a second value. Although in FIG. 4 the first value is represented as logic 1 (or data 1) and the second value is represented as logic 0 (or data 0), the method of representing the first value and the second value may be varied.

[0052] The first data element is also called an on pixel, and the second data element is also called an off pixel. The first data element instructs a change of a specific grayscale value (GVi) to one of the threshold grayscale values, and the second data element instructs a change of a specific grayscale value (GVi) to a minimum grayscale value.

[0053] As exemplified in FIG. 4(a), the first dither pattern (DP1) includes three first data elements and one second data element, the third dither pattern (DP3) includes one first data element and three second data elements, and the fourth dither pattern (DP4) includes two first data elements and two second data elements.

[0054] According to embodiments, when the processing unit includes K*K pixels, each dither pattern (DP1~DPu) stored in the memory device (230) is a K*K data element matrix, and K is a natural number greater than or equal to 3. Therefore, when each dither pattern (DP1~DPu) is a K*K dither pattern, the number of data elements is K 2 It is a dog.

[0055] The threshold grayscale value calculation circuit (215A) selects (also called ‘extraction’) a first data element (DE1=1) that exists at the same location as the first input image data (IID1) corresponding to the first pixel (301) (e.g., top left) from the first pixel pattern (DP1).

[0056] The threshold grayscale value calculation circuit (215A) includes a memory device that stores second information (TH_TB2) including grayscale values ​​(TH1_1, TH1_3, and MIN), and according to embodiments, a lookup table (LUT) may be stored in the memory device.

[0057] As the first data element (DE1=1) matched to the first grayscale value (GV1) is selected in the first dither pattern (DP1), the threshold grayscale value calculation circuit (215A) selects one of the first group of threshold grayscale values ​​(TH1_1 and TH1_3) included in the second information (TH_TB2), generates a first output image data (OUT1) having the selected threshold grayscale value (TH1_1 or TH1_3), and outputs this (OUT1) to the data line driver (240).

[0058] The data line driver (240) selects a gamma voltage corresponding to a threshold grayscale value (TH1_1 or TH1_3) among the gamma voltages (GM1~GMz), supplies the gamma voltage as a first driving voltage to the first data line (Y1) connected to the first pixel (301), and the gate line driver (250) generates a first gate signal to drive the first gate line (X1).

[0059] Depending on the first driving voltage and the first gate signal, the first pixel (301) displays an image corresponding to the first output image data (OUT1) having a threshold grayscale value (TH1_1 or TH1_3).

[0060] As illustrated in FIG. 4(a), since the second grayscale value (GV2) is greater than the first reference grayscale value (HREF), the comparison circuit (213A) outputs (or bypasses) the second input image data (IID2) having the second grayscale value (GV2) as the second output image data (OUT2) to the data line driver (240).

[0061] The data line driver (240) selects a gamma voltage corresponding to a second grayscale value (GV2) among the gamma voltages (GM1~GMz), supplies the gamma voltage as a second driving voltage to a second data line (Y2) connected to a second pixel (302), and the gate line driver (250) generates a first gate signal to drive a first gate line (X1).

[0062] Depending on the second driving voltage and the first gate signal, the second pixel (302) displays an image corresponding to the second output image data (OUT2) having a second grayscale value (GV2).

[0063] As illustrated in FIG. 4(a), since the third grayscale value (GV3) is smaller than the first reference grayscale value (HREF), the comparison circuit (213A) transmits the third input image data (IID3) having the third grayscale value (GV3) to the threshold grayscale value calculation circuit (215A).

[0064] The threshold grayscale value calculation circuit (215A) refers to the lookup table (LUT) stored therein to obtain a third dither pattern (DPj, j=3) corresponding to the third grayscale value (GV3) from the memory device (230).

[0065] The threshold grayscale value calculation circuit (215A) selects a first data element (DE3=1) from the third pixel pattern (DP3) that is located at the same position as the third input image data (IID3) corresponding to the third pixel (303) (e.g., bottom left).

[0066] As the first data element (DE3=1) for the third grayscale value (GV3) is selected from the third grayscale pattern (DP3), the threshold grayscale value calculation circuit (215A) selects one of the first group of threshold grayscale values ​​(TH1_1 and TH1_3) included in the second information (TH_TB2), generates a third output image data (OUT3) having the selected threshold grayscale value (TH1_1 or TH1_3), and outputs this (OUT3) to the data line driver (240).

[0067] The data line driver (240) selects a gamma voltage corresponding to a threshold grayscale value (TH1_1 or TH1_3) among the gamma voltages (GM1~GMz), supplies the gamma voltage as a third driving voltage to the first data line (Y1) connected to the third pixel (303), and the gate line driver (250) generates a second gate signal to drive the second gate line (X2).

[0068] Depending on the third driving voltage and the third gate signal, the third pixel (303) displays an image corresponding to the third output image data (OUT3) having a threshold grayscale value (TH1_1 or TH1_3).

[0069] As illustrated in FIG. 4(a), since the fourth grayscale value (GV4) is smaller than the first reference grayscale value (HREF), the comparison circuit (213A) transmits the fourth input image data (IID4) having the fourth grayscale value (GV4) to the threshold grayscale value calculation circuit (215A).

[0070] The threshold grayscale value calculation circuit (215A) obtains a fourth dither pattern (DPj, j=4) corresponding to a fourth grayscale value (GV4) from the memory device (230) by referring to a lookup table (LUT) stored therein.

[0071] The threshold grayscale value calculation circuit (215A) selects a second data element (DE4=0) from the fourth additional pattern (DP4) that is located at the same position as the fourth input image data (IID4) corresponding to the fourth pixel (304) (e.g., bottom right).

[0072] As the second data element (DE4=0) for the fourth grayscale value (GV4) is selected from the fourth dot pattern (DP4), the threshold grayscale value calculation circuit (215A) selects the minimum grayscale value (MIN) included in the second information (TH_TB2), generates the fourth output image data (OUT4) having the minimum grayscale value (MIN), and outputs this (OUT4) to the data line driver (240). For example, the minimum grayscale value (MIN) may be zero.

[0073] The data line driver (240) selects a gamma voltage corresponding to the minimum grayscale value (MIN) among the gamma voltages (GM1~GMz), supplies the gamma voltage as a fourth driving voltage to the second data line (Y2) connected to the fourth pixel (304), and the gate line driver (250) generates a second gate signal to drive the second gate line (X2).

[0074] According to the fourth driving voltage and the second gate signal, the fourth pixel (304) displays an image corresponding to the fourth output image data (OUT4) having a minimum grayscale value (MIN).

[0075] As shown in FIG. 4(b), the grayscale value (THa) of the first output image data (OUT1) is the first threshold grayscale value (TH1_1) or the second threshold grayscale value (TH1_3), the grayscale value (THc) of the third output image data (OUT3) is the first threshold grayscale value (TH1_1) or the second threshold grayscale value (TH1_3), and the grayscale value (THd) of the fourth output image data (OUT4) is the minimum grayscale value (MIN).

[0076] FIG. 5 is a block diagram showing an example of a dithering circuit illustrated in FIG. 1, and FIG. 6 is an example showing the relationship between a count value and a threshold grayscale value to explain the operation of the threshold grayscale value calculation circuit illustrated in FIG. 5.

[0077] Referring to FIG. 2 and FIG. 5, the threshold grayscale value calculation circuit (215B) of FIG. 5 generates a count value (CNT) by counting the number of first data elements included in the corresponding dither patterns (DP1, DP3, and DP4) using a counter (217), and selects one of the second group of threshold grayscales (TH2_1, TH2_2, and TH2_3) using the count value (CNT). For example, the count value (CNT) for each dither pattern (DP1~DPu) may be 0, 1, 2, or 3.

[0078] For example, the threshold grayscale value calculation circuit (215B) can calculate the threshold grayscale value (TH2_2) for the second count value (CNT2) using a second graph (GRP2) defined according to the threshold grayscale value (TH2_1) for the first count value (CNT1) and the threshold grayscale value (TH2_2) for the third count value (CNT3).

[0079] The threshold grayscale value calculation circuit (215B) may include a memory device that stores third information (TH_TB3) including grayscale values ​​(TH2_1, TH2_2, TH2_3, and MIN). The information stored in the lookup table (LUT) of the threshold grayscale value calculation circuit (215B) is the same as the information stored in the lookup table (LUT) of the threshold grayscale value calculation circuit (215A).

[0080] When the first grayscale value (GV1) is smaller than the first reference grayscale value (HREF), the threshold grayscale value calculation circuit (215B) obtains the first dither pattern (DP1) corresponding to the first grayscale value (GV1) from the memory device (230) and generates a count value (CNT) by counting the number of first data elements included in the first dither pattern (DP1). For example, the count value (CNT) for the first dither pattern (DP1) is 3.

[0081] When the count value (CNT) for the number of first data elements (e.g., logic 1) included in the corresponding dither pattern is the first count value (CNT1), the threshold grayscale value calculation circuit (215B) calculates the fourth threshold grayscale value (TH2_1); when the count value (CNT) for the number of first data elements included in the corresponding dither pattern is the second count value (CNT2), the threshold grayscale value calculation circuit (215B) calculates the fifth threshold grayscale value (TH2_2); and when the count value (CNT) for the number of first data elements included in the corresponding dither pattern is the third count value (CNT3), the threshold grayscale value calculation circuit (215B) calculates the sixth threshold grayscale value (TH2_3).

[0082] The threshold grayscale value calculation circuit (215B) calculates a threshold grayscale value (TH2_3) corresponding to a count value (CNT, e.g., CNT3) for the number of first data elements included in the first dither pattern (DP1), generates a first output image data (OUT1) having the threshold grayscale value (TH2_3), and outputs this (OUT1) to a data line driver (240).

[0083] When the third grayscale value (GV3) is smaller than the first reference grayscale value (HREF), the threshold grayscale value calculation circuit (215B) obtains a third dither pattern (DP3) corresponding to the third grayscale value (GV3) from the memory device (230), and counts the number of first data elements included in the third dither pattern (DP3) to generate a count value (CNT, e.g., CNT1).

[0084] The threshold grayscale value calculation circuit (215B) calculates a threshold grayscale value (TH2_1) corresponding to a count value (CNT, e.g., CNT1) for the number of first data elements included in the third dither pattern (DP3), generates a third output image data (OUT3) having the threshold grayscale value (TH2_1), and outputs this (OUT3) to a data line driver (240).

[0085] When the fourth gradation value (GV4) is smaller than the first reference gradation value (HREF), the threshold gradation value calculation circuit (215B) obtains a fourth dither pattern (DP4) corresponding to the fourth gradation value (GV4) from the memory device (230), and counts the number of first data elements included in the fourth dither pattern (DP4) to generate a count value (CNT, e.g., CNT2).

[0086] However, as the second data element (DE4=0) for the fourth grayscale value (GV4) is selected from the fourth dither pattern (DP4), the threshold grayscale value calculation circuit (215B) generates a fourth output image data (OUT4) having a minimum grayscale value (MIN) instead of the fifth threshold grayscale value (TH2_2), and outputs this (OUT4) to the data line driver (240).

[0087] Referring to FIGS. 4 to 6, the grayscale value (THa) of the first output image data (OUT1) in FIG. 4 (b) is the sixth threshold grayscale value (TH2_3), the grayscale value (THc) of the third output image data (OUT3) is the fourth threshold grayscale value (H2_1), and the grayscale value (THd) of the fourth output image data (OUT4) is the minimum grayscale value (MIN).

[0088] FIG. 7 is a block diagram showing an example of a dithering circuit illustrated in FIG. 1, and FIG. 8 is an example for explaining the process of a reference grayscale value calculation circuit illustrated in FIG. 7 determining a first reference grayscale value and a first reference grayscale value.

[0089] Referring to FIG. 7, the dithering circuit (210C) includes a reference grayscale value calculation circuit (211B), a comparison circuit (213B), and a threshold grayscale value calculation circuit (215C). The dithering circuit (210C) of FIG. 7 is an embodiment of the dithering circuit (210) shown in FIG. 1.

[0090] The reference grayscale value calculation circuit (211B) includes a memory device that stores fourth information (TH_TB4) including first group threshold grayscale values ​​(TH1_1 and TH1_3) and first group minimum grayscale values ​​(MIN1_1 and MIN1_3) for display brightness values ​​(DBV1 and DBV3).

[0091] As exemplified in FIG. 8, assuming that when the display brightness value (DBV) is the first brightness value (DBV1), the threshold grayscale value is the first threshold grayscale value (TH1_1) and the minimum grayscale value is the first minimum grayscale value (MIN1_1), and when the display brightness value (DBV) is the third brightness value (DBV3), the threshold grayscale value is the third threshold grayscale value (TH1_3) and the minimum grayscale value is the third minimum grayscale value (MIN1_3), the reference grayscale value calculation circuit (211B) calculates the second threshold grayscale value (TH1_2) for the second brightness value (DBV2) using already known values ​​(DBV1, DBV3, TH1_1, and TH1_3), and calculates the second minimum grayscale for the second brightness value (DBV2) using already known values ​​(DBV1, DBV3, MIN1_1, and MIN_3). Calculate the value (MIN1_2), output the second threshold grayscale value (TH1_2) as the first reference grayscale value (HREF) to the comparison circuit (213B), and output the second minimum grayscale value (MIN1_2) as the second reference grayscale value (LREF) to the comparison circuit (213B).

[0092] For example, the reference grayscale value calculation circuit (211B) can calculate the second minimum grayscale value (MIN1_2) for the second brightness value (DBV2) by interpolating the first minimum grayscale value (MIN1_1) for the first brightness value (DBV1) and the third minimum grayscale value (MIN1_3) for the third brightness value (DBV3).

[0093] For example, the reference grayscale value calculation circuit (211B) can calculate the second minimum grayscale value (MIN1_2) for the second brightness value (DBV2) using a third graph (GRP3) of a straight line passing through two points ((DBV1, MIN1_1) and (DBV3, MIN1_3)).

[0094] Referring to the first graph (GRP1) and the third graph (GRP3) of Fig. 8, when the display brightness value (DBV) decreases, the threshold grayscale value at which no stains occur in the low-grayscale image increases, and the minimum grayscale value increases.

[0095] The comparison circuit (213B) receives input image data (IIDi) having a specific grayscale value (GVi), compares the specific grayscale value (GVi) with a second reference grayscale value (LREF), compares the specific grayscale value (GVi) with a first reference grayscale value (HREF), and outputs the input image data (IIDi) having the specific grayscale value (GVi) to the threshold grayscale value calculation circuit (215C) only when the specific grayscale value (GVi) is equal to or greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF).

[0096] However, when a specific grayscale value (GVi) is smaller than a second reference grayscale value (LREF), or when a specific grayscale value (GVi) is equal to or greater than a first reference grayscale value (HREF), the comparison circuit (213B) outputs (or bypasses) the input image data (IIDi) having the specific grayscale value (GVi) directly to the data driver (240).

[0097] It is assumed that each grayscale value (GV1, GV3, and GV4) is greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF), and that the second grayscale value (GV2) is greater than the first reference grayscale value (HREF).

[0098] Since the first grayscale value (GV1) is greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF) (LREF <GV1<HREF), 비교 회로(213B)는 제1계조 값(GV1)을 갖는 제1입력 이미지 데이터(IID1)를 임계 계조 값 계산 회로(215C)로 전송한다.

[0099] The threshold grayscale value calculation circuit (215C) obtains a first dither pattern (DP1) corresponding to a first grayscale value (GV1) from the memory device (230) by referring to a lookup table (LUT) stored therein. The threshold grayscale value calculation circuit (215C) includes a memory device that stores fifth information (TH_TB5) including first group threshold grayscale values ​​(TH1_1 and TH1_3) and first group minimum grayscale values ​​(MIN1_1 and MIN1_3).

[0100] As the first data element (DE1=1) for the first grayscale value (GV1) is selected from the first dither pattern (DP1), the threshold grayscale value calculation circuit (215C) selects one of the first group of threshold grayscale values ​​(TH1_1 and TH1_3), generates a first output image data (OUT1) having the threshold grayscale value (TH1_1 or TH1_3), and outputs this (OUT1) to the data line driver (240).

[0101] Since the second grayscale value (GV2) is greater than the first reference grayscale value (HREF), the comparison circuit (213B) bypasses the second input image data (OUT2) having the second grayscale value (GV2) to the data line driver (240).

[0102] Since the third grayscale value (GV3) is greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF) (LREF <GV3<HREF), 비교 회로(213C)는 제3계조 값(GV3)을 갖는 제3입력 이미지 데이터(OUT3)를 임계 계조 값 계산 회로(215C)로 전송한다.

[0103] The threshold grayscale value calculation circuit (215C) obtains a third dither pattern (DP3) corresponding to a third grayscale value (GV3) from the memory device (230) by referring to a lookup table (LUT) stored therein.

[0104] As the first data element (DE3=1) for the third grayscale value (GV3) is selected from the third dither pattern (DP3), the threshold grayscale value calculation circuit (215C) selects one of the first group of threshold grayscale values ​​(TH1_1 and TH1_3), generates a third output image data (OUT3) having the threshold grayscale value (TH1_1 or TH1_3), and outputs this (OUT3) to the data line driver (240).

[0105] Since the 4th grayscale value (GV4) is greater than the 2nd reference grayscale value (LREF) and smaller than the 1st reference grayscale value (HREF) (LREF <GV4<HREF), 비교 회로(213B)는 제4계조 값(GV4)을 갖는 제4입력 이미지 데이터(OUT4)를 임계 계조 값 계산 회로(215A)로 전송한다.

[0106] The threshold grayscale value calculation circuit (215C) obtains a fourth dither pattern (DP4) corresponding to a fourth grayscale value (GV4) from the memory device (230) by referring to a lookup table (LUT) stored therein.

[0107] As the second data element (DE4=0) for the fourth grayscale value (GV4) is selected from the fourth dither pattern (DP4), the threshold grayscale value calculation circuit (215C) selects one of the minimum grayscale values ​​(MIN1_1 and MIN1_3) of the first group, generates a fourth output image data (OUT4) having the minimum grayscale value (MIN1_1 or MIN1_3), and outputs this (OUT4) to the data line driver (240).

[0108] FIG. 9 is a block diagram showing an example of a dithering circuit illustrated in FIG. 1, and FIG. 10 is an example showing the relationship between a count value and a threshold grayscale value to explain the operation of the threshold grayscale value calculation circuit illustrated in FIG. 9.

[0109] Referring to FIG. 9, the dithering circuit (210D) includes a reference grayscale value calculation circuit (211B), a comparison circuit (213B), and a threshold grayscale value calculation circuit (215D). The dithering circuit (210D) of FIG. 9 is an embodiment of the dithering circuit (210) shown in FIG. 1.

[0110] Except for the threshold grayscale value calculation circuit (215D), the structure and operation of the reference grayscale value calculation circuit (211B) and the comparison circuit (213B) of FIG. 9 are identical to the structure and operation of the reference grayscale value calculation circuit (211B) and the comparison circuit (213B) of FIG. 7.

[0111] The threshold grayscale value calculation circuit (215D) includes a counter (217) and a memory device that stores sixth information (TH_TB6) including second group threshold grayscale values ​​(TH2_1, TH2_2, and TH2_3) and second group minimum grayscale values ​​(MIN2_1, MIN2_2, and MIN2_3).

[0112] Referring to FIGS. 4, 9, and 10, the threshold grayscale value calculation circuit (215D) generates a count value (CNT) by counting the number of first data elements included in the corresponding dither pattern (DP1, DP3, and DP4) using a counter (217), selects one of the second group of threshold grayscales (TH2_1, TH2_2, and TH2_3) using the count value (CNT), and selects one of the second group of minimum grayscale values ​​(MIN2_1, MIN2_2, and MIN2_3) using the count value (CNT).

[0113] When the first grayscale value (GV1) is greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF), the threshold grayscale value calculation circuit (215D) obtains the first dither pattern (DP1) corresponding to the first grayscale value (GV1) from the memory device (230), and counts the number of first data elements included in the first dither pattern (DP1) to generate a count value (CNT).

[0114] The threshold grayscale value calculation circuit (215D) calculates a sixth threshold grayscale value (TH2_3) corresponding to a count value (CNT, e.g., CNT3) for the number of first data elements included in the first dither pattern (DP1), generates a first output image data (OUT1) having the sixth threshold grayscale value (TH2_3), and outputs this (OUT1) to a data line driver (240).

[0115] When the third grayscale value (GV3) is greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF), the threshold grayscale value calculation circuit (215D) obtains the third dither pattern (DP3) corresponding to the third grayscale value (GV3) from the memory device (230), and counts the number of first data elements included in the third dither pattern (DP3) to generate a count value (CNT, e.g., CNT1).

[0116] The threshold grayscale value calculation circuit (215D) calculates a fourth threshold grayscale value (TH2_1) corresponding to a count value (CNT, e.g., CNT1) for the number of first data elements included in the third dither pattern (DP3), generates a third output image data (OUT3) having the fourth threshold grayscale value (TH2_1), and outputs this (OUT3) to a data line driver (240).

[0117] When the fourth grayscale value (GV4) is greater than the second reference grayscale value (LREF) and smaller than the first reference grayscale value (HREF), the threshold grayscale value calculation circuit (215D) obtains the fourth dither pattern (DP4) corresponding to the fourth grayscale value (GV4) from the memory device (230), and counts the number of first data elements included in the fourth dither pattern (DP4) to generate a count value (CNT, e.g., CNT2).

[0118] As the second data element (DE4=0) for the fourth grayscale value (GV4) is selected, the threshold grayscale value calculation circuit (215B) calculates a minimum grayscale value (MIN2_2) corresponding to a count value (CNT, e.g., CNT2) for the number of first data elements included in the fourth dither pattern (DP4), generates a fourth output image data (OUT4) having the minimum grayscale value (MIN2_2), and outputs this (OUT4) to the data line driver (240).

[0119] Referring to FIG. 4, the grayscale value (THa) of the first output image data (OUT1) in FIG. 4 (b) is the sixth threshold grayscale value (TH2_3), the grayscale value (THc) of the third output image data (OUT3) is the fourth threshold grayscale value (TH2_1), and the grayscale value (THd) of the fourth output image data (OUT4) is the minimum grayscale value (MIN2_2).

[0120] FIG. 11 is a block diagram showing an example of a dithering circuit illustrated in FIG. 1.

[0121] The dithering circuit (210E) of FIG. 11 includes a reference grayscale value calculation circuit (211A), a comparison circuit (213A), and a threshold grayscale value calculation circuit (215E). The dithering circuit (210E) of FIG. 11 is an embodiment of the dithering circuit (210) shown in FIG. 1.

[0122] Except for the threshold grayscale value calculation circuit (215E), the structure and operation of the reference grayscale value calculation circuit (211A) and the comparison circuit (213A) of FIG. 2 are identical to the structure and operation of the reference grayscale value calculation circuit (211A) and the comparison circuit (213A) of FIG. 11.

[0123] The threshold grayscale value calculation circuit (215E) receives a first input image data (IID1) having a first grayscale value (GV1) transmitted from a comparison circuit (213A) and a display brightness value (DBV), and obtains a dither pattern (DPj) corresponding to the first grayscale value (GV1) for each brightness from a memory device (230) by referring to a lookup table (LUT2) stored therein.

[0124] When the grayscale value is the first grayscale value (GV1) and the display brightness value (DBV) is the first brightness value (DBV1), the threshold grayscale value calculation circuit (215E) obtains the 11th dither pattern (DPu, u=11) from the memory device (230) by referring to the lookup table (LUT2).

[0125] When the grayscale value is the first grayscale value (GV1) and the display brightness value (DBV) is the second brightness value (DBV2), the threshold grayscale value calculation circuit (215E) obtains the 12th dither pattern (DPu, u=12) from the memory device (230) by referring to the lookup table (LUT2).

[0126] When the grayscale value is the first grayscale value (GV1) and the display brightness value (DBV) is the third brightness value (DBV3), the threshold grayscale value calculation circuit (215E) obtains the 13th dither pattern (DPu, u=13) from the memory device (230) by referring to the lookup table (LUT2).

[0127] As the corresponding dither pattern (DP11, DP12, or DP13) is selected, the threshold grayscale value calculation circuit (215E) selects one of the threshold grayscale values ​​(TH1_1, TH1_3, and MIN) included in the second information (TH_TB2), generates a first output image data (OUT1) having the selected threshold grayscale value (TH1_1, TH1_3, or MIN), and outputs this (OUT1) to the data line driver (240). The corresponding dither pattern (DP11, DP12, or DP13) is exemplified for convenience of explanation.

[0128] According to embodiments, the threshold grayscale value calculation circuit (215B, 215C, or 215D) shown in FIG. 5, FIG. 7, or FIG. 9 may be replaced with the threshold grayscale value calculation circuit (215E) of FIG. 11.

[0129] FIG. 12 is a flowchart illustrating the operation of a dithering circuit according to an embodiment of the present invention.

[0130] Referring to FIGS. 1 to 12, a dithering circuit (210, 210A to 210E collectively referred to as '210') of an IC (200) of a display driver receives a brightness value (DBV2) of a display (300) and calculates a first reference grayscale value (HREF) corresponding to the brightness value (DBV2) using (e.g., interpolating) first group threshold grayscale values ​​(TH1_1 and TH1_3) (S110).

[0131] The dithering circuit (210) receives first input image data (IID1) having a first grayscale value (GV1) and compares the first grayscale value (GV1) with a first reference grayscale value (HREF) (S120). When the first grayscale value (GV1) is equal to or greater than the first reference grayscale value (HREF), the dithering circuit (210) does not dither the first input image data (IID1) having the first grayscale value (GV1) and bypasses it to the data line driver (240) (S125).

[0132] When the first grayscale value (GV1) is smaller than the first reference grayscale value (HREF), the dithering circuit (210) obtains a first dither pattern (DP1) corresponding to the first grayscale value (GV1) from the memory device (230), and extracts a data element that matches the first grayscale value (GV1) from among the four data elements included in the first dither pattern (DP1) (S130).

[0133] When the extracted data element is the first data element (YES of S140), the dithering circuit (210) selects one of the first group of threshold grayscale values ​​(TH1_1 and TH1_3) as the output grayscale value and outputs the first output image data (OUT1) having the output grayscale value to the data line driver (240) (S150).

[0134] However, when the extracted data element is the second data element (NO of S140), the dithering circuit (210) selects the minimum grayscale value (MIN) as the output grayscale value and outputs the first output image data (OUT1) having the output grayscale value to the data line driver (240) (S155).

[0135] FIG. 13 is a figure illustrating the operation of a dithering circuit when changing from a first display brightness value to a third display brightness value according to an embodiment of the present invention.

[0136] Referring to FIG. 13, when the brightness value of the display (300) changes from a first brightness value (DBV1) to a third brightness value (DBV3), a viewer looking at the display (300) can experience various threshold grayscale values ​​for a period of 5 frames.

[0137] As illustrated in FIG. 3, when the first brightness value (DBV1) is the output grayscale value of the output image data, the output grayscale value is the first threshold grayscale value (TH1_1), and when the third brightness value (DBV3) is the output grayscale value of the output image data, the output grayscale value is the third threshold grayscale value (TH1_3).

[0138] It is assumed that the grayscale values ​​of the 2*2 input image data (i.e., processing unit) are identical, and that the data element matched to the grayscale value of each input image data in the dither pattern corresponding to the grayscale value of each input image data is the first data element, and that in an 8-bit-depth image, the first threshold grayscale value (TH1_1) is 17 and the third threshold grayscale value (TH1_3) is 16.

[0139] Since the output grayscale value of each 2*2 output image data corresponding to the 2*2 input image data in the first frame (1ST FRAME) is 17, the grayscale value of the 2*2 output image data corresponding to the processing unit is 17.

[0140] In the 2nd frame (2ND FRAME), among the 2*2 output image data, the output grayscale value of each of the three output image data is 17, and the output grayscale value of each of the one output image data is 16, so the grayscale value of the 2*2 output image data corresponding to the processing unit is 16.75.

[0141] In the 3rd frame (3RD FRAME), among the 2*2 output image data, the output grayscale value of each of the two output image data is 17, and the output grayscale value of each of the two output image data is 16, so the grayscale value of the 2*2 output image data corresponding to the processing unit is 16.50.

[0142] In the 4th frame (4TH FRAME), the output grayscale value of one output image data among the 2*2 output image data is 17, and the output grayscale value of each of the three output image data is 16, so the grayscale value of the 2*2 output image data corresponding to the processing unit is 16.25.

[0143] In the 5th frame (5TH FRAME), since the output grayscale value of each of the four output image data in the 2*2 output image data is 16, the grayscale value of the 2*2 output image data corresponding to the processing unit is 16.00.

[0144] When the brightness value of the display (300) changes from the first brightness value (DBV1) to the third brightness value (DBV3), the grayscale value of the processing unit can be expressed more precisely at 16 and 17 by the dithering circuit (210) according to the present invention. That is, grayscale values ​​smaller than 1 can be expressed for the processing unit.

[0145] The present invention has been described with reference to embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. Explanation of the symbols

[0146] 100: Display device 200: Display driver IC 210: Dithering circuit 211A, 211B: Reference grayscale value calculation circuit 213A, 213B: Comparison circuit 215A, 215B, 215C, and 215D: Critical Gradient Value Calculation Circuits 230: Memory device 240: Data line driver 250: Gate Driver 300: Display

Claims

Claim 1 A display driver IC comprising: a data line driver that drives a first data line connected to a first pixel of a display in response to output image data; and a dithering circuit that receives a brightness value of the display, calculates a first reference grayscale value corresponding to the brightness value using threshold grayscale values ​​of a first group, receives input image data having a first grayscale value corresponding to the first pixel, compares the first grayscale value with the first reference grayscale value, and generates output image data having an output grayscale value instead of the first grayscale value when the first grayscale value is smaller than the first reference grayscale value. Claim 2 In claim 1, the dithering circuit is a display driver IC that selects one of the first group of threshold grayscale values ​​as the output grayscale value. Claim 3 A display driver IC according to claim 1, wherein the dithering circuit further calculates a second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of a first group, further compares the first grayscale value with the second reference grayscale value, and selects one of the threshold grayscale values ​​of the first group and the minimum grayscale values ​​of the first group as the output grayscale value when the first grayscale value is greater than the second reference grayscale value and smaller than the first reference grayscale value. Claim 4 In paragraph 3, the dithering circuit comprises K, which corresponds to the first grayscale value and includes at least one first data element and at least one second data element. 2 Read a K*K-dither pattern containing - data elements from a memory device, and said K 2 - Among the data elements, when the data element matched to the first grayscale value is the first data element, one of the threshold grayscale values ​​of the first group is selected as the output grayscale value, and the K 2 A display driver IC in which, among the data elements, the data element matched to the first grayscale value is the second data element, and one of the minimum grayscale values ​​of the first group is selected as the output grayscale value, and K is a natural number greater than or equal to 2. Claim 5 In paragraph 3, the dithering circuit is a display driver IC that calculates the first reference grayscale value by interpolating the threshold grayscale values ​​of the first group and calculates the second reference grayscale value by interpolating the minimum grayscale values ​​of the first group. Claim 6 In claim 1, the dithering circuit comprises K, which corresponds to the first grayscale value and includes at least one first data element and at least one second data element. 2 - Read a K*K-dither pattern containing data elements from a memory device, and the K 2 - Among the data elements, when the data element matched to the first grayscale value is the first data element, one of the threshold grayscale values ​​of the first group is selected as the output grayscale value, and the K 2 A display driver IC in which, among the data elements, the minimum grayscale value is selected as the output grayscale value when the data element matched to the first grayscale value is the second data element, and K is a natural number greater than or equal to 2. Claim 7 In claim 1, the dithering circuit comprises K, which corresponds to the first grayscale value and includes at least one first data element and at least one second data element. 2 - Read a K*K-dither pattern containing data elements from a memory device, and the K 2 A display driver IC that calculates a count value by counting the number of the first data element among the data elements, selects one of the threshold grayscale values ​​of the second group corresponding to the count value as the output grayscale value, and wherein K is a natural number greater than or equal to 2. Claim 8 In claim 7, the dithering circuit is, the above K 2 - Among the data elements, when the data element matched to the first grayscale value is the first data element, select any one corresponding to the count value as the output grayscale value, and the K 2 A display driver IC that selects the minimum grayscale value as the output grayscale value when the data element matched to the first grayscale value among the data elements is the second data element. Claim 9 In claim 1, the dithering circuit further calculates a second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of a first group, further compares the first grayscale value with the second reference grayscale value, and when the first grayscale value is greater than the second reference grayscale value and less than the first threshold grayscale value, the dithering circuit comprises K, which corresponds to the first grayscale value and includes at least one first data element and at least one second data element. 2 - Read a K*K-dither pattern containing data elements from a memory device, and the K 2 - Calculate a count value by counting the number of the first data element among the data elements, and the K 2 - Among the data elements, when the data element matched to the first grayscale value is the first data element, select one of the second group of threshold grayscale values ​​related to the first data element that corresponds to the count value as the output grayscale value, and the K 2 A display driver IC in which, when the data element matched to the first grayscale value among the data elements is the second data element, one of the minimum grayscale values ​​of the second group related to the second data element is selected as the output grayscale value corresponding to the count value, and K is a natural number greater than or equal to 2. Claim 10 A display driver IC according to claim 1, wherein the dithering circuit comprises: a reference grayscale value calculation circuit for calculating the first reference grayscale value; a threshold grayscale value calculation circuit; and a comparison circuit that compares the first grayscale value with the first reference grayscale value, bypasses the input image data as the output image data to the data line driver when the first grayscale value is equal to or greater than the first reference grayscale value, and outputs the input image data to the threshold grayscale value calculation circuit when the first grayscale value is smaller than the first reference grayscale value. Claim 11 In claim 10, the threshold grayscale value calculation circuit comprises K, which corresponds to the first grayscale value and includes at least one first data element and at least one second data element. 2 - Read a K*K-dither pattern containing data elements from a memory device, and the K 2 - Among the data elements, when the data element matched to the first grayscale value is the first data element, one of the threshold grayscale values ​​of the first group is selected as the output grayscale value, and the K 2 A display driver IC that selects the minimum grayscale value as the output grayscale value when the data element matched to the first grayscale value among the data elements is the second data element. Claim 12 In claim 1, the dithering circuit comprises: a reference grayscale value calculation circuit that calculates the first reference grayscale value and calculates the second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of the first group; a threshold grayscale value calculation circuit; and a comparison circuit that compares the first grayscale value with the first reference grayscale value, compares the first grayscale value with the second reference grayscale value, bypasses the input image data to the data line driver as the output image data when the first grayscale value is less than the second reference grayscale value or equal to or greater than the first reference grayscale value, and outputs the input image data to the threshold grayscale value calculation circuit when the first grayscale value is greater than the second reference grayscale value and less than the first reference grayscale value, wherein the threshold grayscale value calculation circuit receives the input image data and selects one of the threshold grayscale values ​​of the first group and the minimum grayscale values ​​of the first group as the output grayscale value. Claim 13 A display device comprising: a display including a first data line connected to a first pixel; and a display driver IC for driving the first data line, wherein the display driver IC comprises: a data line driver that drives the first data line in response to output image data; a reference grayscale value calculation circuit that receives a brightness value of the display and calculates a first reference grayscale value corresponding to the brightness value using threshold grayscale values ​​of a first group; and a threshold grayscale value change circuit that receives input image data having a first grayscale value corresponding to the first pixel, compares the first grayscale value with the first reference grayscale value, changes the first grayscale value to an output grayscale value when the first grayscale value is smaller than the first reference grayscale value, and generates the output image data having the output grayscale value, wherein the output grayscale value is any one of the threshold grayscale values ​​of the first group. Claim 14 A display device according to claim 13, wherein the reference grayscale value calculation circuit further calculates a second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of the first group, and the threshold grayscale value change circuit further compares the first grayscale value and the second reference grayscale value, and selects one of the threshold grayscale values ​​of the first group and the minimum grayscale values ​​of the first group as the output grayscale value when the first grayscale value is greater than the second reference grayscale value and smaller than the first reference grayscale value. Claim 15 In claim 13, the threshold grayscale value changing circuit comprises: a threshold grayscale value calculation circuit; and a comparison circuit that bypasses the input image data as output image data to the data line driver when the first grayscale value is greater than the first reference grayscale value, and transmits the input image data to the threshold grayscale value calculation circuit when the first grayscale value is less than the first reference grayscale value, wherein the threshold grayscale value calculation circuit reads a K*K-dither pattern corresponding to the first grayscale value among a plurality of dither patterns stored in a memory device, and K included in the K*K-dither pattern 2 When the data element matched to the first grayscale value among the - data elements is the first data element, one of the threshold grayscale values ​​of the first group is selected as the output grayscale value, and the K 2 A display device in which, among - data elements, when the data element matched to the first grayscale value is the second data element, the minimum grayscale value is selected as the output grayscale value, and K is a natural number greater than or equal to 2. Claim 16 In claim 13. The reference grayscale value calculation circuit further calculates a second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of the first group, and the threshold grayscale value change circuit includes: a threshold grayscale value calculation circuit; and a comparison circuit that further compares the first grayscale value and the second reference grayscale value, bypasses the input image data to the data line driver as the output image data when the first grayscale value is smaller than the second reference grayscale value or when the first grayscale value is larger than the first reference grayscale value, and transmits the input image data to the threshold grayscale value calculation circuit when the first grayscale value is larger than the second reference grayscale value and smaller than the first reference grayscale value, and the threshold grayscale value calculation circuit reads a K*K-dither pattern corresponding to the first grayscale value among a plurality of dither patterns stored in a memory device, and K included in the K*K-dither pattern 2 Among - data elements, when the data element matched to the first grayscale value is the first data element, one of the threshold grayscale values ​​of the first group is selected as the output grayscale value, and the K 2 A display device in which, among - data elements, when the data element matched to the first grayscale value is the second data element, one of the minimum grayscale values ​​of the first group is selected as the output grayscale value, and K is a natural number greater than or equal to 2. Claim 17 In Clause 13, the display is a display device that is an organic light-emitting diode display or an LCD. Claim 18 A method of operating an IC of a display driver for dithering, comprising: receiving a brightness value of a display and calculating a first reference grayscale value corresponding to the brightness value using threshold grayscale values ​​of a first group; receiving input image data having a first grayscale value and comparing the first grayscale value with the first reference grayscale value; changing the first grayscale value to an output grayscale value when the first grayscale value is smaller than the first reference grayscale value; and driving a first data line connected to a first pixel placed on the display using output image data having the output grayscale value. Claim 19 A method of operation of an IC of a display driver for dithering, wherein, in claim 18, the method further comprises the step of calculating a second reference grayscale value corresponding to the brightness value using the minimum grayscale values ​​of the first group; and the step of comparing the first grayscale value and the second reference grayscale value, wherein the step of changing the first grayscale value to an output grayscale value comprises the step of selecting one of the threshold grayscale values ​​of the first group and the minimum grayscale values ​​of the first group as the output grayscale value when the first grayscale value is greater than the second reference grayscale value and smaller than the first reference grayscale value. Claim 20 A method of operating an IC of a display driver according to claim 18, further comprising the steps of: performing a dimming operation for the display using gamma voltages to control the brightness of the display; and generating a brightness value of the display corresponding to the result of the dimming operation.

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