Display driving circuit, display device, and method of operating display driving circuit

Abstract

The present disclosure relates to a display driving circuit, a display apparatus, and an operating method of the display driving circuit. The display driving circuit includes a gray voltage generator configured to generate a plurality of gray voltages by linearly dividing a plurality of gamma tap voltages, a gamma correction module configured to calculate a compensation value for an input pixel value by using a compensation model, and configured to apply the compensation value to the input pixel value to generate a compensated pixel value, and a data driver configured to receive the plurality of gray voltages from the gray voltage generator, and configured to output a data voltage corresponding to the gray voltage to a display panel, the gray voltage being selected from the plurality of gray voltages based on the compensated pixel value.

Description

Technical Field

[0001] The present invention relates to a semiconductor device, and more specifically, to a display driving circuit for driving a display panel to display an image on the display panel, a method of operating the display driving circuit, and a display device including the display driving circuit. Background Technology

[0002] A display device includes a display panel that displays an image, and a display driving circuit that drives the display panel. The display driving circuit can receive image data from an external source and drive the display panel by applying image signals corresponding to the image data to data lines on the display panel. Display panels in which each of the multiple pixels in the pixel array includes an organic light-emitting diode (OLED) are increasingly being used.

[0003] The display driver circuit drives the display panel through the following steps: generating multiple grayscale voltages corresponding to multiple grayscale values ​​using a grayscale voltage generator, selecting one of the grayscale voltages based on the pixel value, and applying the selected grayscale voltage as a data voltage to the pixel. Some of the grayscale voltages generated by the grayscale voltage generator may differ from the ideal grayscale voltage; therefore, the brightness or color of the light signal output from the pixel may be distorted, resulting in gamma error. Summary of the Invention

[0004] The present invention provides a display driving circuit for reducing gamma error based on pixel value compensation, a display device including the display driving circuit, and a method for operating the display driving circuit.

[0005] According to one aspect of the present invention, a display driving circuit is provided, comprising: a grayscale voltage generator configured to generate a plurality of grayscale voltages by linearly dividing a plurality of gamma tap voltages; a gamma correction module configured to calculate a compensation value for an input pixel value using a compensation model, and configured to apply the compensation value to the input pixel value to generate a compensated pixel value; and a data driver configured to receive the plurality of grayscale voltages from the grayscale voltage generator, and configured to output a data voltage corresponding to the grayscale voltages to a display panel, wherein the grayscale voltages are selected from the plurality of grayscale voltages based on the compensated pixel value.

[0006] According to another aspect of the present invention, a method for operating a display driving circuit is provided, the method comprising: calculating a compensation value for a pixel value of input pixel data based on a compensation model; generating a compensated pixel value based on the pixel value and the compensation value; selecting a grayscale voltage from a plurality of grayscale voltages based on output pixel data including the compensated pixel value; and outputting a data voltage corresponding to the selected grayscale voltage to a display panel.

[0007] According to another aspect of the present invention, a display device is provided, comprising: a display panel; and a display driving circuit configured to drive the display panel to display an image, wherein the display driving circuit comprises: a grayscale voltage generator configured to determine a plurality of gamma tap voltages based on a plurality of selection signals, and configured to generate a plurality of grayscale voltages based on the plurality of gamma tap voltages; a gamma correction module configured to calculate a compensation value for an input pixel value using a compensation model, and configured to apply the compensation value to the input pixel value to generate a compensated pixel value; and a data driver configured to output a data voltage corresponding to the grayscale voltage to the display panel, wherein the grayscale voltage is selected from the plurality of grayscale voltages based on the compensated pixel value. Attached Figure Description

[0008] The embodiments of the inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0009] Figure 1 This is a block diagram of a display device and a display system including the display device according to an example embodiment;

[0010] Figure 2 This is a block diagram of the display driving circuit and display panel according to an example embodiment;

[0011] Figure 3 This is a circuit diagram of an example pixel according to an example embodiment;

[0012] Figure 4 This is a schematic block diagram of a display driving circuit according to an example embodiment;

[0013] Figure 5 yes Figure 4 A circuit diagram of an example grayscale voltage generator;

[0014] Figure 6A It is a graph of the grayscale voltage output from the grayscale voltage generator according to the example embodiment;

[0015] Figure 6B This is a diagram used to describe a gamma correction method of a gamma correction module according to an example embodiment;

[0016] Figure 7 This is a block diagram of an example gamma correction module according to an example embodiment;

[0017] Figure 8 An example of input pixel data is shown;

[0018] Figure 9 This is a diagram illustrating a compensation model according to an example embodiment;

[0019] Figure 10This is an operation table applied to the compensation value calculator according to an example embodiment;

[0020] Figure 11 This is a diagram showing the compensated pixel values ​​generated by the compensation value calculator according to an example embodiment;

[0021] Figure 12A and Figure 12B This is a diagram illustrating a compensation model according to an example embodiment;

[0022] Figure 13 This is an operation table applied to the compensation value calculator according to an example embodiment;

[0023] Figure 14 This is a block diagram of an example gamma correction module according to an example embodiment;

[0024] Figure 15 It is a graph used to describe gamma error;

[0025] Figure 16 This is a flowchart of a method for operating a display driving circuit according to an example embodiment;

[0026] Figure 17 This is a schematic block diagram of a display driving circuit according to an example embodiment;

[0027] Figure 18 This is a block diagram of a digital gamma module according to an example embodiment;

[0028] Figure 19 This is a flowchart of a method for operating a display driving circuit according to an example embodiment;

[0029] Figure 20 A diagram illustrating an example display device according to an example embodiment; and

[0030] Figure 21 This is an example diagram of a display device according to an example embodiment. Detailed Implementation

[0031] In the following description, various exemplary embodiments will be described with reference to the accompanying drawings.

[0032] Figure 1 This is a block diagram of a display device and a display system including the display device according to an example embodiment.

[0033] According to an example embodiment, the display system 1 can be installed on an electronic device with image display capabilities. Examples of electronic devices may include, but are not limited to, smartphones, tablet PCs, portable multimedia players (PMPs), cameras, wearable devices, televisions, digital video disc (DVD) players, refrigerators, air conditioners, set-top boxes, robots, drones, medical devices, navigation devices, global positioning system (GPS) receivers, vehicle equipment, furniture, and measuring equipment.

[0034] refer to Figure 1 The display system 1 may include a display device 100 and a host processor 200, and the display device 100 may include a display driver circuit (or display driver integrated circuit (DDI)) 110 and a display panel 120.

[0035] The host processor 200 can generate image data IDT to be displayed on the display panel 120 and send the image data IDT and control commands CMD to the display driver circuit 110. For example, the control commands CMD may include setting information such as brightness, gamma, frame rate, and operation mode of the display driver circuit 110. The host processor 200 can also send clock signals or synchronization signals to the display driver circuit 110.

[0036] The host processor 200 may include a graphics processor. However, embodiments are not limited thereto, and the host processor 200 may include various processors, such as a central processing unit (CPU), a microprocessor, a multimedia processor, and an application processor. In embodiments, the host processor 200 may include an integrated circuit (IC) or a system-on-a-chip (SoC).

[0037] Display device 100 can display image data IDT received from host processor 200. In embodiments, display device 100 can be implemented by integrating display driving circuitry 110 and display panel 120 into a single module. For example, display driving circuitry 110 can be mounted on a substrate of display panel 120, or electrically connected to display panel 120 via a connection member such as a flexible printed circuit board (FPCB).

[0038] Display panel 120 displays images and may include a display that receives electrically transmitted image signals and displays two-dimensional (2D) images, such as an organic light-emitting diode (OLED) display, a thin-film transistor liquid crystal display (TFT-LCD), a field emission display, or a plasma display panel (PDP). Furthermore, display panel 120 may be a flat panel display or a flexible display panel. In the following description, for purposes of description, it is assumed that display panel 120 includes an OLED display panel in which each pixel comprises an OLED. However, embodiments are not limited thereto, and display panel 120 may include different types of display panels.

[0039] The display driving circuit 110 can convert the image data IDT received from the host processor 200 into multiple analog signals, such as data voltages, for driving the display panel 120, and provide the analog signals to the display panel 120. As a result, an image corresponding to the image data IDT can be displayed on the display panel 120.

[0040] The display driving circuit 110 may include a gamma correction module 10. The gamma correction module 10 can generate a compensated pixel value by calculating a compensation value for the input pixel value using a compensation model of the form of a quadratic function and applying the compensation value to the input pixel value. In an embodiment, the gamma correction module 10 can generate a compensated grayscale voltage value by calculating a compensation value based on the received grayscale voltage value using a compensation model and applying the compensation value to the grayscale voltage value. The grayscale voltage value and the compensated grayscale voltage value refer to digital data representing the voltage level of the grayscale voltage.

[0041] The display driving circuit 110 may include a grayscale voltage generator. Figure 2The grayscale voltage generator 115 (115 in the image) converts the input pixel value into a grayscale voltage corresponding to the grayscale indicated by the input pixel value, and can apply the grayscale voltage corresponding to the input pixel value to the pixel of the display panel 120. Therefore, the pixel can output a light signal with a brightness corresponding to the input pixel value. The grayscale voltage generator 115 can generate multiple grayscale voltages. The grayscale voltage generator 115 may have limitations in accurately generating grayscale voltages corresponding to multiple grayscales respectively. For example, although the increase in grayscale voltage relative to an increase in grayscale needs to be non-linear in order to display an image with a desired gamma value on the display panel 120, the grayscale voltage generator 115 can generate grayscale voltages that increase linearly relative to an increase between specific grayscales. The difference between the ideal grayscale voltage and the grayscale voltage generated by the grayscale voltage generator 115 may cause distortion in the brightness and / or color of the light signal output from the pixel. This distortion can be called gamma error. Due to gamma error, banding artifacts may appear in the image instead of a gradual color transition, thus giving the impression of sharp color banding.

[0042] As described above, the display driving circuit 110 can reduce gamma error by compensating for pixel values ​​or voltage data. Furthermore, instead of storing compensation values ​​corresponding to multiple pixel values ​​in a lookup table and searching for the corresponding compensation value in the lookup table when a pixel value is input, the display driving circuit 110 can calculate the compensation value corresponding to the pixel value using a gamma error compensation model with a quadratic function form to compensate for the pixel. Therefore, a storage area for storing compensation values ​​is not required.

[0043] Figure 2 This is a block diagram of a display driving circuit and a display panel according to an example embodiment.

[0044] refer to Figure 2 The display driving circuit 110 may include an interface circuit 111, control logic 112, memory 113, data driver 114 (or source driver), grayscale voltage generator 115, and scan driver 116 (or gate driver). The display driving circuit 110 may further include elements such as voltage generators and clock generators.

[0045] In this embodiment, the interface circuit 111, control logic 112, memory 113, data driver 114, grayscale voltage generator 115, and scan driver 116 can be integrated into a single semiconductor chip. Alternatively, the interface circuit 111, control logic 112, memory 113, data driver 114, and grayscale voltage generator 115 can be integrated into a single semiconductor chip; and the scan driver 116 can also be formed in the display panel 120.

[0046] Interface circuit 111 can exchange signals or data with host processor 200. Interface circuit 111 may include a serial interface, such as a mobile industrial processor interface. Mobile Display Digital Interface (MDDI), DisplayPort, or Embedded DisplayPort (eDP).

[0047] Memory 113 can store image data received from host processor 200 in units of frames. Memory 113 can be referred to as graphics random access memory (RAM) or a frame buffer. Memory 113 can include volatile memory such as dynamic RAM (DRAM) or static RAM (SRAM), or non-volatile memory such as read-only memory (ROM), flash memory, resistive RAM (ReRAM), or magnetic RAM (MRAM). Image data received from host processor 200 can be stored in memory 113 before or after image processing in control logic 112. In an embodiment, display driving circuitry 110 may not include memory 113. In this case, image data received from host processor 200 can undergo image processing in control logic 112 and then be sent to data driver 114.

[0048] The control logic 112 can control the operation of the display driving circuit 110 and can control the components of the display driving circuit 110, such as the interface circuit 111, memory 113, data driver 114, grayscale voltage generator 115 and scan driver 116, so that the image corresponding to the image data received from the host processor 200 is displayed on the display panel 120.

[0049] Control logic 112 can also perform image processing on the received image data to change the brightness, size, or format of the received image data, or it can generate new image data to be displayed on display panel 120 based on the received image data. For such operations, control logic 112 may include an intellectual property (IP) module for image processing.

[0050] Control logic 112 may include gamma correction module 10. (See above reference.) Figure 2 The gamma correction module 10 can generate compensated pixel values ​​or compensated grayscale voltage values ​​(CIDT) and provide them to the data driver 114. In this embodiment, image data that has already undergone image processing in the IP used for image processing can be input to the gamma correction module 10.

[0051] like Figure 2As shown, the gamma correction module 10 can be implemented as part of the control logic 112. However, the embodiments are not limited thereto, and the gamma correction module 10 can be implemented as a separate control logic independent of the control logic 112.

[0052] The gamma correction module 10 can be implemented by hardware or a combination of software (or firmware) and hardware. The gamma correction module 10 can be implemented by hardware logic such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or complex programmable logic devices (CPLDs); firmware or software running on a processor such as a microcontroller unit (MCU) or a CPU; or a combination of hardware and software.

[0053] The grayscale voltage generator 115 can generate multiple grayscale voltages VG based on a set gamma curve. <n-1:0>(or gamma voltage), for example, "n" gamma voltages VG <n-1:0>(where "n" is an integer of 2 or greater), and the gamma voltage VG <n-1:0>Provided to data driver 114. Grayscale voltage generator 115 can adjust the maximum and / or minimum grayscale voltage and adjust the gamma curve according to the gamma setting value. The gamma curve is a graph showing the brightness of the light signal for multiple grayscale levels output from the pixels PX of the display panel 120. The grayscale voltage VG can be adjusted. <n-1:0>The voltage level is adjusted so that the output light signal has a brightness corresponding to the set gamma curve, or it can be determined based on the grayscale voltage VG. <n-1:0>The gamma curve is adjusted by regulating the voltage level.

[0054] The data driver 114 can convert the compensated image data CIDT received from the control logic 112 into multiple image signals, such as multiple data voltages VD1 to VDm (where "m" is an integer of 2 or greater), and can output the data voltages VD1 to VDm to the display panel 120 through multiple data lines DL.

[0055] The data driver 114 can receive compensated image data CIDT in units of line data, that is, in units of data corresponding to multiple pixels included in a single horizontal line on the display panel. The data driver 114 can be based on the grayscale voltage VG received from the grayscale voltage generator 115. <n-1:0>The line data received from control logic 112 will be converted into data voltages VD1 to VDm.

[0056] Scan driver 116 can be connected to multiple scan lines SL of display panel 120 and can drive the scan lines SL sequentially. Under the control of control logic 112, scan driver 116 can sequentially provide multiple scan signals S1 to Sg (where "g" is a positive integer of 2 or greater) with valid levels (e.g., logic high level) to the scan lines SL. Therefore, scan lines SL can be selected sequentially, and data voltages VD1 to VDm can be applied to multiple pixels PX connected to the selected scan lines SL respectively.

[0057] The display panel 120 may include multiple data lines DL, multiple scan lines SL, and multiple pixels PX, each of the multiple pixels PX being connected to a corresponding one of the multiple scan lines SL and a corresponding one of the multiple data lines DL.

[0058] Each of the pixels PX can output light of a predetermined color, and at least two pixels PX that are adjacent to each other in a row or adjacent rows and output light of different colors respectively (e.g., red, blue, and / or green pixels) can form a single pixel unit. The at least two pixels PX forming a pixel unit can be referred to as a sub-pixel. The display panel 120 may have an RGB structure in which red, blue, and green pixels form a single pixel unit. However, the embodiments are not limited to this, and the display panel 120 may have any alternative structure, such as an RGBW structure in which the pixel unit also includes a white pixel for brightness enhancement. Optionally, the pixel unit of the display panel 120 may include pixels of colors other than red, green, and blue.

[0059] Display panel 120 may include an OLED display panel, wherein each of the pixels PX includes an OLED. However, embodiments are not limited thereto, and display panel 120 may include another type of display panel. Display panel 120 may be a flat panel display panel or a flexible panel display panel.

[0060] In this embodiment, the data driver 114 can sense changes in the electrical characteristics of the pixel PX, such as degradation. The display panel 120 may further include multiple sensing lines and multiple sensing scan lines connected to the pixel PX. When the scan driver 116 drives the sensing scan lines, the electrical characteristics of the pixel PX connected to the sensing scan lines can be transmitted to the data driver 114 through the sensing lines. The data driver 114 can convert the sensed signals into sensed data and provide the sensed data to the control logic 112. The control logic 112 can determine the degradation degree of the pixel PX based on the sensed data and perform degradation compensation on the pixel PX.

[0061] Figure 3 This is a circuit diagram of an example pixel according to an example embodiment.

[0062] refer to Figure 3 A pixel (PX) may include an OLED OD and a pixel circuit PCIR. The anode of the OLED OD may be connected to the pixel circuit PCIR, and the cathode of the OLED OD may be connected to a second driving power supply ELVSS. The OLED OD can emit light with a brightness corresponding to the amount of current supplied from the pixel circuit PCIR.

[0063] The pixel circuit PCIR controls the amount of current flowing from the first driving power supply ELVDD through the OLED OD to the second driving power supply ELVSS in response to the data voltage VD. The pixel circuit PCIR may include a select transistor ST, a drive transistor DT, and a storage capacitor Cst. At least one selected from the select transistor ST and the drive transistor DT may include: an oxide semiconductor thin film transistor including an active layer comprising an oxide semiconductor, or a low-temperature polycrystalline silicon (LTPS) thin film transistor including an active layer comprising polycrystalline silicon.

[0064] The first electrode of the driving transistor DT is connected to the first driving power supply ELVDD, and the second electrode of the driving transistor DT is connected to the anode of the OLED OD (e.g., the second node N2). The gate electrode of the driving transistor DT can be connected to the first node N1. The driving transistor DT can control the amount of current flowing from the first driving power supply ELVDD to the second driving power supply ELVSS via the OLEDOD in response to the voltage of the first node N1.

[0065] The first electrode of the selector transistor ST is connected to the data line DL, and the second electrode of the selector transistor ST is connected to the first node Nl. The gate electrode of the selector transistor ST is connected to the scan line SL.

[0066] The storage capacitor Cst is connected between the first node N1 and the second electrode (i.e., the second node N2) of the driving transistor DT. The storage capacitor Cst can store the voltage of the first node N1.

[0067] When a scan signal S at the active level is applied to pixel PX via scan line SL, selection transistor ST can turn on in response to scan signal S and provide data voltage VD, which is provided to first node N1 via data line DL; and storage capacitor Cst can store data voltage VD. Drive transistor DT can provide drive current I to OLED OD in response to data voltage VD. DT .

[0068] In an embodiment, the pixel circuit PCIR may further include a sensing transistor configured to output a sensing signal, such as the voltage of the second node N2, wherein the sensing signal indicates the electrical characteristics of the pixel PX. The sensing transistor may be turned on in response to a sensing scan signal and may output the sensed signal to (e.g., included in...) Figure 2 (The sensing line in the display panel 120).

[0069] Figure 3 The structure of pixel PX is merely an example, and the structure of pixel PX is not limited to this. For example, with Figure 3 Unlike other OLEDs, the OD can be located between the first driving power supply ELVDD and the first electrode of the driving transistor DT. Additionally or alternatively, the pixel PX can further include another transistor to control its emission period or enhance its driving characteristics.

[0070] Figure 4 This is a schematic block diagram of a display driving circuit according to an example embodiment.

[0071] refer to Figure 4 The control logic 112 may include a gamma correction module 10 and a dithering module 20, and the data driver 114 may include a digital-to-analog converter (DAC) 41 and an output buffer 42. Figure 4 The diagram shows a data driver 114 including drive circuitry for a single channel, comprising a DAC 41 and an output buffer 42; this is for ease of description only. The data driver 114 may include drive circuitry for multiple channels.

[0072] The gamma correction module 10 can receive input pixel data IPD, perform gamma correction on the input pixel data IPD, and output compensated pixel data CPD as the gamma correction result. The gamma correction module 10 can generate compensated pixel values ​​by using a compensation model with a quadratic function form to calculate a compensation value for the input pixel value indicated by the input pixel data IPD, and by applying the compensation value to the input pixel value. The gamma correction module 10 can output compensated pixel data CPD with the compensated pixel values. In this way, the gamma correction module 10 can perform gamma correction.

[0073] Reference Figures 5 to 6B Provide a detailed description of gamma correction.

[0074] Figure 5 yes Figure 4 The circuit diagram of an example grayscale voltage generator 115 is shown below. For illustrative purposes, it is assumed that the grayscale voltage generator 115 generates 256 grayscale voltages VG<255:0>.

[0075] refer to Figure 5 The grayscale voltage generator 115 may include a gamma tap voltage generator 51 and a grayscale voltage output unit 52. The gamma tap voltage generator 51 can generate multiple gamma tap voltages corresponding to multiple gamma taps that define a gamma curve, such as the zeroth gamma tap voltage Vgmt0 to the fifth gamma tap voltage Vgmt5. Based on the zeroth gamma tap voltage Vgmt0 to the fifth gamma tap voltage Vgmt5, the grayscale voltage output unit 52 can generate multiple grayscale voltages, such as the zeroth grayscale voltage VG corresponding to multiple grayscale values. <0> Up to the 255th grayscale voltage VG <255> Gamma taps can refer to specific gray levels, such as reference gray levels, to determine the gamma curve within those gray levels, and the zeroth gamma tap voltage Vgmt0 to the fifth gamma tap voltage Vgmt5 can correspond to some of the gray levels, for example, the zeroth gray level voltage VG. <0> Up to the 255th grayscale voltage VG <255> .

[0076] The gamma tap voltage generator 51 may include multiple resistor strings, such as a first resistor string RS1 to a fifth resistor string RS5, and multiple selectors, such as a first selector SLT1 to a sixth selector SLT6. The number of resistor strings and selectors may vary. Although not shown, the gamma tap voltage generator 51 may also include multiple buffers, such as current buffers, to reliably maintain the voltage levels of the zeroth gamma tap voltage Vgmt5 to the fifth gamma tap voltage Vgmt5 output from the first selector SLT1 to the sixth selector SLT6, respectively.

[0077] Each of the first resistor strings RS1 to the fifth resistor string RS5 can generate multiple voltages by dividing the voltage applied across each resistor string using the multiple resistors included in each string, and can output said voltages. Each of the first selectors SLT1 to the sixth selectors SLT6 can select one of the voltages output from the corresponding resistor string based on a corresponding one of a plurality of selection signals (e.g., first selection signal CS1 to sixth selection signal CS6), and output the selected voltage. Therefore, the zeroth gamma tap voltage Vgmt0 to the fifth gamma tap voltage Vgmt5 can be generated.

[0078] For example, the first resistor string RS1 can generate multiple voltages by dividing the high reference voltage VSH and the low reference voltage VSL, and the first selector SLT1 can select one of the multiple voltages received from the first resistor string RS1 in response to the first selection signal CS1, and output the selected voltage as the zeroth gamma tap voltage Vgmt0. The zeroth gamma tap voltage Vgmt0 can be compared with the lowest grayscale voltage (e.g., the zeroth grayscale voltage VG). <0> Corresponding to this, the second selector SLT2 can select one of the voltages received from the first resistor string RS1 in response to the second selection signal CS2, and output the selected voltage as the fifth gamma tap voltage Vgmt5. The fifth gamma tap voltage Vgmt5 can be the highest grayscale voltage (e.g., the 255th grayscale voltage VG). <255> Corresponding to.

[0079] Each of the second resistor strings RS2 to the fifth resistor strings RS5 can use its resistors to divide the fifth gamma tap voltage Vgmt5 between another gamma tap voltage (e.g., one of the zeroth gamma tap voltage Vgmt0 to the third gamma tap voltage Vgmt3) and output multiple voltages. Each of the third selectors SLT3 to the sixth selectors SLT6 can respond to a corresponding third selection signal CS3 to the sixth selection signal CS6 to select one of the voltages received from the corresponding second resistor strings RS2 to the fifth resistor strings RS5, and can output the selected voltage as one of the first gamma tap voltages Vgmt1 to the fourth gamma tap voltage Vgmt4. Each of the first gamma tap voltages Vgmt1 to the fourth gamma tap voltage Vgmt4 can correspond to one of the medium grayscale voltages. For example, the first gamma tap voltage Vgmt1 can be output as the seventh grayscale voltage VG. <7> The second gamma tap voltage Vgmt2 can be output as the 75th grayscale voltage VG. <75> The third gamma tap voltage Vgmt3 can be output as the 151st grayscale voltage VG. <151> Furthermore, the fourth gamma tap voltage Vgmt4 can be output as the 203rd grayscale voltage VG. <203> ,

[0080] Therefore, the gamma tap voltage generator 51 can generate multiple gamma tap voltages corresponding to multiple gamma taps (e.g., multiple reference grayscales), such as the zeroth gamma tap voltage Vgmt0 to the fifth gamma tap voltage Vgmt5. The first selection signal CS1 to the sixth selection signal CS6 can be changed, and the voltage levels of the zeroth gamma tap voltage Vgmt0 to the fifth gamma tap voltage Vgmt5 can be adjusted. Therefore, the highest and lowest grayscale voltages can be adjusted according to the first selection signal CS1 and the second selection signal CS2, respectively, and multiple intermediate grayscale voltages determining the gamma curve can be adjusted according to the third selection signal CS3 to the sixth selection signal CS6.

[0081] The grayscale voltage output unit 52 may include a resistor string, such as a sixth resistor string RS6, to which multiple gamma tap voltages (e.g., zero gamma tap voltage Vgmt0 to fifth gamma tap voltage Vgmt5) are applied. The sixth resistor string RS6 can generate multiple grayscale voltages, such as a zero grayscale voltage VG, by dividing the multiple gamma tap voltages (e.g., zero gamma tap voltages Vgmt0 to fifth gamma tap voltages Vgmt5 applied to multiple nodes ND1 to ND6 respectively). <0> Up to the 255th grayscale voltage VG <255> .

[0082] The resistance between any two adjacent nodes in nodes ND1 to ND6 can have the same resistance value, or all resistors included in the sixth resistor string RS6 can have the same resistance value. Therefore, the difference between adjacent grayscale voltages between adjacent gamma tap voltages can be the same. For example, the zeroth grayscale voltage VG <0> Up to the seventh grayscale voltage VG <7> The difference between two adjacent grayscale voltages can be compared with the zeroth grayscale voltage VG. <0> Up to the seventh grayscale voltage VG <7> The difference between the other two adjacent grayscale voltages is the same. Additionally, the seventh grayscale voltage VG... <7> Up to the 75th grayscale voltage VG <75> The difference between two adjacent grayscale voltages can be compared with the seventh grayscale voltage VG. <7> Up to the 75th grayscale voltage VG <75> The difference between the other two adjacent grayscale voltages is the same. As mentioned above, the grayscale voltage between adjacent gamma tap voltages can increase in a constant increment.

[0083] Figure 6A This is a graph of the grayscale voltage output from the grayscale voltage generator, and Figure 6B This is a diagram illustrating a gamma correction method for a gamma correction module according to an example embodiment. Figure 6B Detailed illustration Figure 6A AR in the region.

[0084] refer to Figure 6A and Figure 6B The horizontal axis represents the input pixel value, and the vertical axis represents the voltage, such as grayscale voltage. The input pixel value represents grayscale. The solid line represents the voltage generated by the grayscale voltage generator (e.g., ...). Figure 5 The grayscale voltage generator 115 generates multiple grayscale voltages corresponding to the real grayscale voltage map RGP, while the dashed line represents the ideal grayscale voltage map IGP corresponding to multiple ideal grayscale voltages.

[0085] As referenced above Figure 5 The aforementioned signals can be adjusted according to the first selection signal CS1 to the sixth selection signal CS6, respectively, to the multiple gamma taps GMT. <0> To GMT <5> The corresponding zero-gamma tap voltages are Vgmt0 to Vgmt5. Therefore, the grayscale voltages corresponding to the zero-gamma tap voltages Vgmt0 to Vgmt5 can be the same in both the real grayscale voltage map RGP and the ideal grayscale voltage map IGP. The grayscale voltage between two adjacent gamma tap voltages from the zero-gamma tap voltages Vgmt0 to the fifth gamma tap voltages Vgmt5 can increase linearly in the real grayscale voltage map RGP, but non-linearly in the ideal grayscale voltage map IGP. As a result, gamma error may occur.

[0086] refer to Figure 6B Multiple grayscale voltages between the second gamma tap voltage Vgmt2 and the third gamma tap voltage Vgmt3 can increase linearly in the real grayscale voltage map RGP, but increase nonlinearly in the ideal grayscale voltage map IGP.

[0087] For example, the input pixel value can indicate the k-th gray level, and the k-th gray level voltage VG generated by the gray level voltage generator 115 <k>It can be the first voltage V1. However, the ideal grayscale voltage corresponding to the kth grayscale can be the second voltage V2, and the second voltage V2 can be equal to the (k+3)th grayscale voltage VG generated by the grayscale voltage generator 115 corresponding to the (k+3)th grayscale.<k+3> .

[0088] refer to Figure 4 and Figure 6B The gamma correction module 10 can generate compensated pixel values ​​based on the input pixel values ​​of the input pixel data IPD, and generate compensated pixel data CPD including the compensated pixel values. For example, the gamma correction module 10 can convert an input pixel value indicating the k-th gray level into a compensated pixel value indicating the (k+3)-th gray level corresponding to the ideal gray level voltage (e.g., a second voltage V2 corresponding to the k-th gray level). The gamma correction module 10 can generate compensated pixel values ​​by adding a compensation value to the input pixel value. For example, the gamma correction module 10 can generate the compensated pixel value (k+3) by adding a compensation value "3" to the input pixel value "k".

[0089] The gamma correction module 10 may include a compensation value calculator 11. The compensation value calculator 11 can generate compensation values ​​corresponding to the input pixel values ​​by using a compensation model with a quadratic function form. The compensation value calculator 11 may include at least one arithmetic unit or processor that performs quadratic function calculations.

[0090] refer to Figure 6B The closer the grayscale value corresponding to the true grayscale voltage is to the gamma tap corresponding to the gamma tap voltage (e.g., the second gamma tap voltage Vgmt2 or the third gamma tap voltage Vgmt3), the smaller the difference between the true grayscale voltage and the ideal grayscale voltage. Conversely, the farther the grayscale value corresponding to the true grayscale voltage is from the gamma tap voltage, the larger the difference between the true and ideal grayscale voltages. By reflecting this characteristic of the difference between the true and ideal grayscale voltages, the compensation model can calculate the compensated pixel value. The compensated pixel value increases as the grayscale value indicated by the input pixel value moves further away from the gamma tap, and decreases as the grayscale value indicated by the input pixel value moves closer to the gamma tap. The following will refer to... Figures 7 to 1 2. Describe the compensation model in detail.

[0091] The gamma correction module 10 can generate a compensated pixel value by adding a compensation value to the input pixel value. In an embodiment, the gamma correction module 10 can generate a compensated pixel value by multiplying the compensation value calculated by the compensation value calculator 11 with at least one weight based on the brightness setting and / or color setting of the display panel 120, and adding the multiplication result to the input pixel value.

[0092] The dithering module 20 can perform dithering on the compensated pixel data CPD received from the gamma correction module 10 and generate output pixel data OPD as the dithering result. Dithering methods known to those skilled in the art can be performed by the dithering module 20.

[0093] In this embodiment, the dithering module 20 can perform spatial dithering. The dithering module 20 can generate output pixel data OPD by performing dithering based on at least one compensated pixel data, where the at least one compensated pixel data corresponds to a pixel PX adjacent to the pixel PX corresponding to the output pixel data OPD. For example, the dithering module 20 can generate the output pixel data OPD based on first compensated pixel data and second compensated pixel data, where the first compensated pixel data corresponds to a first pixel and the second compensated pixel data corresponds to a second pixel adjacent to the first pixel. The dithering module 20 can generate the output pixel data OPD by performing specific operations on the first compensated pixel data and the second compensated pixel data.

[0094] In this embodiment, the dithering module 20 can perform time dithering. The dithering module 20 can change the output pixel data OPD during multiple frame periods, causing the pixel PX to output a light signal with an average brightness corresponding to the compensated pixel data CPD during the frame period. For example, when the compensated pixel data CPD indicates a 2.5 gray level, the dithering module 20 can generate an output pixel data OPD indicating a second gray level during a first frame period, wherein a first image is displayed on the display panel 120 during the first frame period, and generate an output pixel data OPD indicating a third gray level during a second frame period, wherein a second image or a first image is displayed on the display panel 120 during the second frame period. Therefore, a light signal with an average brightness corresponding to a 2.5 gray level can be output from the pixel PX during both the first and second frame periods.

[0095] In an embodiment, the dithering module 20 can perform dithering on compensated pixel data CPD, which includes M bits of data (where M is a positive integer of 8 or greater), to generate N bits of data (where N is a positive integer less than or equal to M).

[0096] In this embodiment, the display driving circuit 110 may not include the dithering module 20. In this case, the compensated pixel data CPD can be provided to the data driver 114 as output pixel data OPD.

[0097] DAC 41 can receive multiple grayscale voltages from grayscale voltage generator 115, for example, the zeroth grayscale voltage VG. <0> Up to the 255th grayscale voltage VG <255> Furthermore, the zero-grayscale voltage VG can be selected based on the output pixel data OPD. <0> Up to the 255th grayscale voltage VG <255> One of them. DAC 41 can output the selected grayscale voltage VSG to output buffer 42. The output pixel data OPD can be generated at the zero grayscale voltage VG. <0> Up to the 255th grayscale voltage VG <255> Choose the grayscale voltage that is closest to the ideal grayscale voltage indicated by the input pixel data IPD.

[0098] The output buffer 42 can perform buffering (e.g., voltage or current buffering) on ​​the selected grayscale voltage VSG, and can output the buffered voltage as a data voltage VD to the display panel 120, and more specifically, output to the display panel 120's ( Figure 2 (The data cable DL in the middle)

[0099] As described above, according to the example embodiment, the gamma correction module 10 of the display driving circuit 110 can use a compensation model with a quadratic function form to calculate the compensated pixel value for the input pixel data IPD (i.e., the input pixel value), and provide the output pixel data OPD based on the compensated pixel value to the data driver 114. Therefore, the gamma error caused by the characteristics of the grayscale voltage generator 115 can be reduced.

[0100] Figure 7 This is a block diagram of an example gamma correction module according to an example embodiment. Figure 7 The gamma correction module 10a shown can be applied to Figure 4 The display driver circuit 110.

[0101] refer to Figure 7 The gamma correction module 10a may include a compensation value calculator 11 and an adder 12, and can generate compensated pixel data CPD based on the compensated pixel value "cp" by performing gamma correction based on the pixel value of the input pixel data IPD (i.e., the input pixel value p). The input pixel data IPD and the compensated pixel data CPD may be multi-bit data and may have the same number of bits as each other.

[0102] Figure 8 An example of input pixel data IPD is shown.

[0103] refer to Figure 8 The input pixel data IPD can include M-bit data (e.g., M is a positive integer of 8 or greater), which includes higher-order N-bit data B. <m-1>To B <m-n>(where N is a positive integer less than or equal to M) and low-order (MN) bits of data B <m-n-1>To B <0> The higher-order N-bit data B <m-1>To B <m-n>Includes the most significant bit (MSB) of the M-bit data, and the lower-order (MN) bits of data B <m-n-1>To B <0> This includes the least significant bit (LSB) of the M-bit data. In this embodiment, the higher-order N-bit data B <m-1>To B <m-n>It can represent the integer value of the input pixel data IPD, while the low-order (MN) bit data B <m-n-1>To B <0> The input pixel data IPD can be represented by a decimal value. For example, the input pixel data IPD may include a high-order 8-bit data representing an integer value and a low-order 4-bit data representing a decimal value. However, the embodiments are not limited to this. In another example, M may be equal to N, and the input pixel data IPD may have an integer value.

[0104] Return to reference Figure 7 The compensation value calculator 11 can generate a compensation value C(p) corresponding to the input pixel value p based on a compensation model with a quadratic function form.

[0105] The compensation value calculator 11 can generate the compensation value C(p) based on Equation 1.

[0106] Equation 1

[0107] C(p) = W cmpn (p)×C model (p)

[0108] Here, C model (p) represents a compensation model with quadratic function form for the input pixel value p, and w cmpn (p) represents the compensation model c model The magnitude and sign of (p) are first weighted and can be determined based on the input pixel value p. Compensation model c model (p) can be represented as Equation 2.

[0109] Equation 2

[0110]

[0111] Here, i is the index corresponding to the input pixel value p, and P i It is a gamma tap with a smaller value between the two gamma taps closest to the input pixel value p, and P i+1 It is the gamma tap with the larger value between the two gamma taps. The two gamma taps can each represent the corresponding gray level. It can be determined based on the input pixel value p. When... Replace with X and change C model When (p) is replaced with Y, equation 2 can be rewritten as equation 3.

[0112] Equation 3

[0113] Y = X × (1 - X)

[0114] Figure 9 This is a diagram illustrating a compensation model according to an example embodiment.

[0115] Figure 9 The compensation model represented by Equation 3 is shown. The horizontal axis represents X in Equation 3, and the vertical axis represents Y, i.e., the compensation model c. model (p). For example... Figure 9 As shown, the compensation model c model (p) can be a quadratic function with respect to the input pixel value p.

[0116] Figure 10 This is an operation table applied to the compensation value calculator according to an example embodiment. The compensation value calculator 11 can be used... Figure 10 Operation table TB1.

[0117] refer to Figure 10 The input pixel value p can be classified into multiple pixel value ranges corresponding to index i, for example, the zero range R0 to the tenth range R10. The zero range R0 to the tenth range R10 can be classified into eleven pixel value groups based on multiple gamma taps (e.g., the zeroth gamma tap to the eleventh gamma tap). For example, the zeroth gamma tap P0 can indicate the zeroth gray level, the first gamma tap P1 can indicate the first gray level, the fourth gamma tap P4 can indicate the 35th gray level, and the tenth gamma tap P... 10 It can indicate the 203rd gray level.

[0118] A first weight w can be set for each of the eleven pixel values. cmpn (p). For example, for the zeroth range R0, the first range R1, and the tenth range R10, the first weight w can be... cmpn (p) is set to 0.0, where, in the first range R1, the input pixel value p indicates a gray level equal to or greater than the zeroth gamma tap P0 and less than the first gamma tap P1 (e.g., equal to or greater than the zeroth gray level and less than the first gray level), the input pixel value p in the first range R1 indicates a gray level equal to or greater than the first gamma tap P1 and less than the second gamma tap P2 (e.g., equal to or greater than the first gray level and less than the seventh gray level), and in the tenth range R10, the input pixel value p indicates a gray level equal to or greater than the tenth gamma tap P10. 10 And less than the eleventh gamma tap P 11 The gray level (e.g., equal to or greater than gray level 203 and less than gray level 255). For the fifth range R5, the first weight w can be... cmpn (p) is set to 1.68. In the fifth range R5, the input pixel value p indicates a gray level that is equal to or greater than the fourth gamma tap P4 and less than the fifth gamma tap P5 (e.g., equal to or greater than the 35th gray level and less than the 51st gray level). For the sixth range R6, the first weight w can be... cmpn (p) is set to 5.94. In the sixth range R6, the input pixel value p indicates a gray level that is equal to or greater than the fifth gamma tap P5 and less than the sixth gamma tap P6 (e.g., equal to or greater than the 51st gray level and less than the 87th gray level). Furthermore, for the seventh range R7, the first weight w can be... cmpn (p) is set to 8.06. In the seventh range R7, the input pixel value p indicates a gray level that is equal to or greater than the sixth gamma tap P6 and less than the seventh gamma tap P7 (e.g., equal to or greater than the 87th gray level and less than the 151st gray level). The first weight w can be set based on the degree of compensation (e.g., the difference between the true gray level voltage and the ideal gray level voltage) for each of the pixel value ranges (e.g., the zero range R0 to the tenth range R10). cmpn (p). For example, the compensation degree for each of the zero range R0 to the tenth range R10 can be determined empirically.

[0119] Figure 11 This is a diagram showing the compensated pixel values ​​generated by the compensation value calculator according to an example embodiment.

[0120] The horizontal axis represents the input pixel value p, and the vertical axis represents the compensation value C(p). A compensation value C(p) of quadratic function form can be generated for the input pixel value p between two adjacent gamma taps. The compensation value C(p) can be "0" when the input pixel value p corresponds to one of the multiple gamma taps, and it can have its maximum value when the input pixel value p corresponds to the median between the first and second gamma taps. The sign and magnitude of the quadratic function can be determined by a first weight w set for the range of pixel values ​​to which the input pixel value p belongs. cmpn (p) to determine, as referenced above. Figure 10 As stated above.

[0121] Refer again Figure 7 Adder 12 adds the compensation value C(p) to the input pixel value "p". The result is a compensated pixel value cp. The compensated pixel data CPD, based on the compensated pixel value "cp", can be output.

[0122] according to Figure 7 The gamma correction module 10a, and the compensated pixel value "cp" corresponding to each of the pixels PX in the display panel 120, can be expressed as Equation 4.

[0123] Equation 4

[0124] CPD(x,y)=IPD(x,y)+C(IPD(x,y))

[0125] Here, IPD(x,y) represents the input pixel value "p" of the input pixel data IPD corresponding to a specific pixel PX (e.g., the pixel PX at row 'x' and column 'y' of display panel 120, where x and y are positive integers); and CPD(x,y) represents the compensated pixel value "cp" of the compensated pixel data CPD corresponding to pixel PX. The gamma correction module 10a can calculate the compensation value C(IPD(x,y)) based on the input pixel value IPD(x,y) of the pixel PX at row 'x' and column 'y', and can generate the compensated pixel value CPD(x,y) of the pixel PX at row 'x' and column 'y' by adding the compensation value C(IPD(x,y)) to the input pixel value IPD(x,y).

[0126] Figure 12A and Figure 12B This is a diagram illustrating a compensation model according to an example embodiment.

[0127] According to the example embodiment, when Figure 7 When calculating the compensation value C(p) using the compensation value calculator 11, the compensation model C represented by Equation 5 can be used. model (p)'.

[0128] Equation 5

[0129]

[0130] Here, β is the adjustment compensation model C model Parameters of the form (p)'. When β is a real number less than 1, the compensation model C model (p)' can have a left-biased quadratic function form, such as Figure 12A As shown. When β is a real number greater than 1, the compensation model C model (p)' can have a right-biased quadratic function form, such as Figure 12B As shown. When β is 1, the compensation model C model (p)' can be compared with the compensation model C in Equation 2. model (p) Same.

[0131] Figure 13 This is an operation table applied to a compensation value calculator according to an example embodiment. According to the example embodiment, the compensation value calculator (e.g., Figure 7 The compensation value calculator 11) can be used Figure 13 Operation table TB2.

[0132] refer to Figure 13 The input pixel value p can be classified into multiple pixel value ranges corresponding to index i, such as eleven pixel value ranges; and a parameter β and a first weight W can be set for each pixel value range. cmpn (p). The first weight W can be set based on the compensation degree for each of multiple pixel value ranges (e.g., the zero range R0 to the tenth range R10). cmpn (p) and parameter β. (See above for reference.) Figure 10 The classification of pixel value ranges and the first weight W are described. cmpn (p), and its redundant description will be omitted.

[0133] For example, for the fifth range R5, β can be set to 0.75, and for the seventh range R7, β can be set to 1.25. Therefore, a compensation model with a left-biased quadratic function form (such as...) can be used in the fifth range R5. Figure 12A (as shown) and by using a compensation model with a right-biased quadratic function form in the 7th range R7 (such as... Figure 12B As shown in the diagram, the compensation value (C(p)) is obtained. For other pixel value ranges, such as the zero range R0, the first range R1, the sixth range R6, and the tenth range R10, β can be set to 1. Therefore, the diagram showing the compensation value (C(p)) can have values ​​in the zero range R0, the first range R1, the sixth range R6, and the tenth range R10. Figure 9 The quadratic function form shown.

[0134] Figure 14 This is a block diagram of an example gamma correction module according to an exemplary embodiment. The gamma correction module 10b can be applied to... Figure 4 The display driver circuit 110.

[0135] refer to Figure 14 The gamma correction module 10b may include a compensation value calculator 11, an adder 12, a weight determiner 13, and a multiplier 14.

[0136] As described above, the compensation value calculator 11 can generate a compensation value corresponding to the input pixel value "p" based on a compensation model with a quadratic function form, for example, a first compensation value C(p)_1.

[0137] The weight determiner 13 can determine the second weight Wdbv based on the brightness setting DBV of the display panel 120. For example, the weight determiner 13 can store the second weight Wdbv for gamma correction for each of a plurality of brightness ranges, the second weight Wdbv can be set for the display panel 120, and can output the second weight Wdbv corresponding to the brightness setting DBV.

[0138] Multiplier 14 can generate a second compensation value C(p)_2 by multiplying the first compensation value C(p)_1 with the second weight Wdbv.

[0139] In an embodiment, a third weight Wc can be determined for each color. For example, the third weight Wc can be set differently for each of red, green, and blue. Multiplier 14 can multiply the first compensation value C(p)_1 with the second weight Wdbv and the third weight Wc, or it can multiply the first compensation value C(p)_1 with the third weight Wc. In other words, the first compensation value C(p)_1 can be multiplied with at least one selected from the second weight Wdbv and the third weight Wc, and a second compensation value C(p)_2 can be generated as the multiplication result.

[0140] Adder 12 adds the second compensation value C(p)_2 output from multiplier 14 to the input pixel value "p". As a result, a compensated pixel value cp is generated. Compensated pixel data including the compensated pixel value cp can be output.

[0141] according to Figure 14 The gamma correction module 10b, and the compensated pixel value cp corresponding to each of the pixels PX in the display panel 120, can be expressed as Equation 6.

[0142] Equation 6

[0143] CPD(x,y)=IPD(x,y)+Wdbv×Wc×C(IPD(x,y))_1

[0144] The gamma correction module 10b can calculate a first compensation value C(IPD(x,y))_1 based on the input pixel value IPD(x,y) of the pixel PX at row 'x' and column 'y', and can generate a second compensation value by multiplying the first compensation value C(IPD(x,y))_1 with at least one selected from the second weight Wdbv and the third weight Wc. Any unselected weight from the second weight Wdbv and the third weight Wc can be set to "1". The gamma correction module 10b can generate the compensated pixel value CPD(x,y) of the pixel PX at row 'x' and column 'y' by adding the second compensation value (i.e., Wdbv × Wc × C(IPD(x,y))_1) to the input pixel value IPD(x,y).

[0145] Figure 15 It is a graph used to describe gamma error. Figure 15 The ideal gamma curve IGC and the measured gamma curve RGC are shown.

[0146] The brightness at each gray level can be represented by an ideal gamma curve IGC based on the ideal gray level voltage. However, as referenced above... Figure 6A and Figure 6B The gray voltage corresponding to the gray level between two adjacent gamma taps among the plurality of gray voltages generated by the gray voltage generator 115 may be different from the ideal gray voltage corresponding to that gray level. Furthermore, as the gray level moves further away from the adjacent gamma taps, the difference between the gray voltage generated by the gray voltage generator 115 and the ideal gray voltage may increase.

[0147] Therefore, as Figure 15 As shown, between adjacent gamma taps, for example, at the k-th gamma tap GMT... <k>and the (K+1)th gamma tap GMT<K+1> Between (where K is 0 or a positive integer), there may be a first gamma error GMerr1 and a second gamma error GMerr2. The gamma error occurring at a gray level relatively far from the gamma tap, such as the second gamma error GMerr2, can be greater than the gamma error occurring at a gray level relatively close to the gamma tap, such as the first gamma error GMerr1.

[0148] To address this issue, according to an example embodiment, Figure 1 The display driving circuit 110 generates a compensation value for the input pixel value based on a compensation model with a quadratic function form using the gamma correction module 10. Based on the compensated pixel data including the compensation value, it selects one of a plurality of grayscale voltages generated by the grayscale voltage generator 115, thereby selecting a grayscale voltage close to the ideal grayscale voltage. Therefore, the display driving circuit 110 can reduce the gamma error caused by the characteristics of the grayscale voltage generator.

[0149] Figure 16 This is a flowchart of an operation method of a display driving circuit according to an example embodiment. Figure 16 The operation method can be provided by Figures 1 to 3 The display driver circuit 110 in the middle is executed.

[0150] refer to Figure 16 In operation S110, the display driving circuit 110 can receive image data, which includes multiple pixel data corresponding to multiple pixels respectively. For example, Figure 2 The interface circuit 111 can receive image data from the host processor 200, and the image data can be stored in the memory 113 or provided to the control logic 112.

[0151] In operation S120, control logic 112, more specifically, allows gamma correction module 10 to calculate a compensation value for each pixel data based on a compensation model having a quadratic function form. (See above reference...) Figure 7 The compensation value calculator 11 can calculate the compensation value for the pixel value based on the compensation model according to equations 1 and 2.

[0152] In operation S130, the gamma correction module 10 can generate a compensated pixel value based on the pixel value and a compensation value. In an embodiment, the gamma correction module 10 can generate the compensated pixel value by adding the compensation value to the pixel value. In an embodiment, the gamma correction module 10 can generate the compensated pixel value by adding the compensation value output from the compensation value calculator 11 to a weight set based on the brightness of the display panel 120 (e.g., ...). Figure 14 The second weight (Wdbv) and the weight based on color settings (e.g., Figure 14 The second compensation value is generated by multiplying at least one of the third weights (Wc) selected in the third weights, and the compensated pixel value can be generated by adding the second compensation value to the pixel value.

[0153] In operation S140, data driver 114 can select a grayscale voltage from a plurality of grayscale voltages provided by grayscale voltage generator 115 based on output pixel data having compensated pixel values. In an embodiment, control logic 112 can provide compensated pixel data having compensated pixel values ​​as output pixel data to data driver 114. In an embodiment, control logic 112 can perform dithering on the compensated pixel data having compensated pixel values ​​and provide output pixel data having dithered compensated pixel values ​​to data driver 114. Data driver 114 can select a grayscale voltage corresponding to the output pixel data from the grayscale voltages based on the output pixel data received from control logic 112.

[0154] In operation S150, the data driver 114 can output a data voltage corresponding to the selected grayscale voltage to the display panel 120. For example, Figure 4 The output buffer 42 can buffer the selected grayscale voltage and output the buffered voltage as a data voltage to the data line DL of the display panel 120.

[0155] According to the above example embodiments, gamma correction can also be applied to display driving circuits using digital gamma methods and display driving circuits using analog gamma methods. The analog gamma method refers to a method of converting a pixel value into a grayscale voltage based on multiple grayscale voltages reflecting a gamma curve. The digital gamma method refers to a method in which a pixel value is converted into a grayscale voltage value corresponding to the pixel value based on multiple grayscale voltage values ​​(where the voltage value is digital data representing the voltage level) that respectively represent multiple grayscale voltages reflecting a gamma curve; then, based on multiple grayscale voltages whose voltage levels increase linearly, the digital data corresponding to the grayscale voltage values ​​is converted into grayscale voltages, i.e., the analog signal to be provided to the display panel.

[0156] In the following text, reference will be made to Figures 17 to 19 This describes gamma correction applied to a display driver circuit using a digital gamma method, according to an example embodiment.

[0157] Figure 17 This is a schematic block diagram of a display driving circuit according to an example embodiment, and Figure 18 This is a block diagram of a digital gamma module according to an example embodiment.

[0158] refer to Figure 17 The display driving circuit 110c may include control logic 112c, grayscale voltage generator 115c, and data driver 114c. The control logic 112c may include digital gamma module 30c, pixel degradation compensation module 40c, and dithering module 20c.

[0159] The grayscale voltage generator 115c can generate multiple grayscale voltages, for example, grayscale voltage VG. <n-1:0>Grayscale voltage VG <n-1:0>The difference between two adjacent grayscale voltages can be related to the grayscale voltage VG. <n-1:0>The difference between the other two adjacent grayscale voltages is the same. Grayscale voltage VG <n-1:0>It may not reflect the gamma curve of the 120c display panel, and the grayscale voltage VG <n-1:0>The increase in voltage level can be linear. The gamma curve can be reflected in the digital gamma module 30c.

[0160] Taking into account the gamma curve of the display panel 120c, the digital gamma module 30c can convert the pixel value of the input pixel data IPD into grayscale voltage data GD. The grayscale voltage data GD is a digital value indicating the grayscale voltage corresponding to the pixel value.

[0161] refer to Figure 18 The digital gamma module 30c may include a grayscale voltage data generator 31c and a gamma correction module 32c.

[0162] The grayscale voltage data generator 31c can convert the input pixel data IPD into first grayscale voltage data GD1, which indicates the grayscale voltage corresponding to the pixel value of the input pixel data IPD.

[0163] The grayscale voltage data generator 31c may include a gamma lookup table (GLUT), which may include multiple gamma tap voltage values ​​(referred to as reference gamma data values) corresponding to multiple gamma tap voltages (referred to as reference gamma voltages). For example, the gamma lookup table (GLUT) may include multiple gamma taps (e.g., reference grayscale) and multiple gamma tap voltage values ​​corresponding to the gamma taps. The gamma tap voltage values ​​may be set taking into account the gamma curve.

[0164] The grayscale voltage data generator 31c can generate multiple grayscale voltage values ​​corresponding to multiple grayscale values ​​based on multiple gamma tap voltage values. For example, the grayscale voltage data generator 31c can generate multiple grayscale voltage values ​​by performing linear data allocation on two adjacent gamma tap voltage values. The grayscale voltage data generator 31c can output the grayscale voltage value corresponding to the pixel value of the input pixel data IPD as the first grayscale voltage data GD1.

[0165] When the grayscale voltage data generator 31c stores multiple grayscale voltage values ​​corresponding to multiple grayscale values ​​in a gamma lookup table (GLUT), and converts a pixel value into a grayscale voltage value by searching for the grayscale voltage value corresponding to the pixel value of the input pixel data IPD in the GLUT, a large storage capacity is required to store the GLUT. However, according to the embodiment, the grayscale voltage data generator 31c stores multiple gamma tap voltage values ​​corresponding to some grayscale values ​​(i.e., multiple gamma taps) in the GLUT, and uses the gamma tap voltage values ​​to generate multiple grayscale voltage values, some of which are reference grayscale values ​​among the multiple grayscale values. Therefore, a large storage capacity is not required to store the GLUT.

[0166] The grayscale voltage value generated by the grayscale voltage data generator 31c can increase linearly between two adjacent gamma tap voltage values. However, as mentioned above... Figure 6A The increase in voltage level in the ideal grayscale voltage may not be linear. Therefore, the ideal grayscale voltage may differ from the grayscale voltage indicated by the grayscale voltage value generated by the grayscale voltage data generator 31c.

[0167] The gamma correction module 32c can perform gamma correction on the first grayscale voltage data GD1 received from the grayscale voltage data generator 31c, thereby compensating for the difference between the ideal grayscale voltage and the grayscale voltage indicated by the grayscale voltage value.

[0168] The gamma correction module 32c can generate a compensated grayscale voltage value by calculating the compensation value of the grayscale voltage value for the first grayscale voltage data GD1 using a compensation model with a quadratic function form, and applying the compensation value to the grayscale voltage value. The gamma correction module 32c can output the compensated grayscale voltage value as the grayscale voltage data GD.

[0169] The gamma correction module 32c may include a compensation value calculator 11c, which can calculate the compensation value based on equations 1 and 2. In other words, the compensation value calculator 11c can calculate the compensation value for the grayscale voltage value using a compensation model with a quadratic function form.

[0170] In Equations 1 and 2, the grayscale voltage value of the first grayscale voltage data GD1 can be used to replace the input pixel value "p", and a first weight can be set based on the range of grayscale voltage values. For example, the range of grayscale voltage values ​​can be classified into one of multiple voltage value ranges defined based on multiple gamma voltage tap voltages, and a first weight can be set for each of the voltage value ranges.

[0171] Similar to the above references Figure 14 As described above, the gamma correction module 32c can multiply a compensation value (e.g., a first compensation value) output from the compensation value calculator 11c with at least one selected from a second weight and a third weight (the second weight is based on the brightness setting DBV of the display panel 120, and the third weight is set for each color), and add the weighted compensation value (e.g., the second compensation value) to the input grayscale voltage value to generate a compensated grayscale voltage value. As described above, according to the above embodiment, the gamma correction module 32c can perform gamma compensation.

[0172] Return to reference Figure 17 The pixel degradation compensation module 40c can generate degradation compensation data DCD by performing compensation processing (hereinafter referred to as degradation compensation) on the grayscale voltage data GD to compensate for pixel degradation.

[0173] The pixels PX of the display panel 120c may degrade over time or due to stress applied to the pixels PX, thus changing factors such as the threshold voltage of the driving transistor DT. Figure 3 The data driver 114c can receive a sensed signal SS from the display panel 120c, the sensed signal SS indicating changes in the electrical characteristics of the pixel PX, such as degradation. The data driver 114c can generate sensed data SDT by performing analog-to-digital conversion on the sensed signal SS, and can provide the sensed data SDT to the pixel degradation compensation module 40c.

[0174] The pixel degradation compensation module 40c can determine the degradation degree of pixel PX based on the sensed data SDT, and generate a degradation compensation value based on the degradation degree. The pixel degradation compensation module 40c can generate degradation compensation data DCD by applying the degradation compensation value to the grayscale voltage data GD. For example, the pixel degradation compensation module 40c can add the degradation compensation value to the grayscale voltage data GD and output the sum as the degradation compensation data DCD.

[0175] The dithering module 20c can perform dithering on the degradation compensation data DCD and output the dithering result as the output pixel data OPD. (See above reference.) Figure 4 The jitter module 20c can perform time jitter or spatial jitter.

[0176] Data driver 114c can obtain grayscale voltage VG from grayscale voltage generator 115c. <n-1:0>Select the grayscale voltage corresponding to the output pixel data OPD, buffer the selected grayscale voltage, and output the buffered voltage as the data voltage VD to the display panel 120c.

[0177] As mentioned above, grayscale voltage VG <n-1:0>The increase in voltage level can be linear. However, since the output pixel data OPD includes grayscale voltage values ​​corresponding to the grayscale of the input pixel data IPD, the grayscale voltage selected corresponding to the output pixel data OPD can reflect the gamma curve of the display panel 120c.

[0178] As described above, according to the embodiment, when a data voltage reflecting a gamma curve is generated using a digital gamma method, the display drive circuit 110c can perform gamma correction using a compensation model with a quadratic function form. Therefore, gamma error can be reduced.

[0179] Figure 19 This is a flowchart of an operation method of a display driving circuit according to an example embodiment. Figure 19 The operation method can be provided by Figure 1 , Figure 2 and Figure 17 One or more of the display driver circuits 110 and 110c are executed.

[0180] refer to Figure 17 and Figure 19 In operation S210, the display driving circuit 110c can receive image data, which includes multiple pixel data corresponding to multiple pixels respectively. For example, Figure 2 The interface circuit 111 can receive image data from the host processor 200, and the image data can be stored in the memory 113 or provided to the control logic 112c.

[0181] In operation S220, control logic 112c, more specifically, allows the digital gamma module 30c to generate multiple grayscale voltage values ​​based on a gamma lookup table that includes multiple gamma tap voltage values. The digital gamma module 30c can linearly distribute two adjacent gamma tap voltage values ​​among the multiple gamma tap voltage values, and therefore can generate multiple grayscale voltage values ​​that linearly increase among the gamma tap voltage values. The digital gamma module 30c does not need to store the multiple grayscale voltage values ​​corresponding to the multiple grayscale values ​​in the gamma lookup table, thus reducing the storage capacity required to store the gamma lookup table.

[0182] In operation S230, the digital gamma module 30c can select a grayscale voltage value that corresponds to the pixel value of the input pixel data from the grayscale voltage value.

[0183] In operation S240, based on a compensation model with a quadratic function form, the gamma correction module 32c can calculate the gamma compensation value, i.e., the compensation value for the selected grayscale voltage value. The gamma correction module 32c can calculate the compensation value for the pixel value based on the compensation model according to equations 1 and 2.

[0184] In operation S250, the gamma correction module 32c can generate a compensated grayscale voltage value based on the grayscale voltage value and the compensation value. In an embodiment, the gamma correction module 32c can generate a compensated grayscale voltage value by adding the compensation value to the grayscale voltage value. In an embodiment, the gamma correction module 32c can generate a second compensation value by multiplying the compensation value (e.g., a first compensation value calculated based on a compensation model having a quadratic function form) with at least one selected from a weight based on the brightness setting of the display panel 120c and a weight based on the color setting, and can generate a compensated grayscale voltage value by adding the second compensation value to the grayscale voltage value.

[0185] In operation S260, the data driver 114c can select a grayscale voltage from a plurality of grayscale voltages provided by the grayscale voltage generator 115c based on the output pixel data having a compensated grayscale voltage value. In an embodiment, the control logic 112c can provide the grayscale data having the compensated grayscale voltage value as output pixel data to the data driver 114c. In an embodiment, the control logic 112c can perform degradation compensation and jitter on the grayscale data having the compensated grayscale voltage value, as referenced above. Figure 17 Furthermore, the output pixel data with degradation compensation and jitter grayscale values ​​can be provided to the data driver 114c. The data driver 114c can select a grayscale voltage corresponding to the output pixel data from the grayscale voltages based on the output pixel data received from the control logic 112c.

[0186] In operation S270, the data driver 114c can output a data voltage corresponding to the selected grayscale voltage to the display panel 120c. For example, the data driver 114c can buffer the selected grayscale voltage and output the buffered voltage as a data voltage to the data line DL of the display panel 120c.

[0187] Figure 20 This is an example diagram of a display device according to an example embodiment. Figure 20 The display device 1000 may include a small display panel 1200 and can be applied to mobile devices such as smartphones and tablet PCs.

[0188] refer to Figure 20 The display device 1000 may include a display driving circuit 1100 and a display panel 1200. The display driving circuit 1100 may include at least one IC and may be mounted on a circuit film such as a tap carrier package (TCP), chip on film (COF), or flexible printed circuit (FPC), and attached to the display panel 1200 by using tape auto-adhesion (TAB), or may be mounted on a non-display area of ​​the display panel 1200 (e.g., an area where no image is displayed) by using a chip on glass (COG) method.

[0189] The display driving circuit 1100 may include a data driver 1110 and control logic 1120, and may further include a gate driver. In an embodiment, the gate driver may be mounted on the display panel 1200.

[0190] As referenced above Figures 1 to 18 The control logic 1120 may include a gamma correction module 10 (in... Figure 1 The gamma correction module 10 generates compensated pixel values ​​by calculating a compensation value for the input pixel value using a compensation model with a quadratic function form and applying the compensation value to the input pixel value. As described above, the gamma correction module 10 performs gamma compensation by converting the input pixel value into a compensated pixel value based on the compensation model. The data driver 1110 can drive the display panel 1200 based on the compensated pixel values. Therefore, the quality of the image displayed on the display panel 1200 can be improved.

[0191] Figure 21 This is an example diagram of a display device according to an example embodiment. Figure 21 The display device 2000 may include a medium-sized or large-sized display panel 2200 and may be applied to, for example, televisions and monitors.

[0192] refer to Figure 21 The display device 2000 may include a data driver 2110, a timing controller 2120, a gate driver 2130, and a display panel 2200.

[0193] The timing controller 2120 may include at least one IC or module. The timing controller 2120 can communicate with multiple data driver ICs (DDICs) and multiple gate driver ICs (GDICs) through a preset interface.

[0194] The timing controller 2120 can generate control signals for controlling the drive timing of the data driver IC DDIC and the gate driver IC GDIC, and can provide the control signals to the data driver IC DDIC and the gate driver IC GDIC.

[0195] The data driver 2110 includes a data driver IC DDIC, which can be mounted on a circuit film such as TCP, COF, or FPC and attached to the display panel 2200 by means of a TAB, or mounted on a non-display area of ​​the display panel 2200 by means of a COG method.

[0196] The gate driver 2130 includes a gate driver IC GDIC, which can be mounted on a circuit film and attached to the display panel 2200 via a TAB, or mounted on a non-display area of ​​the display panel 2200 using a COG method. Alternatively, the gate driver 2130 can be formed directly on the lower substrate of the display panel 2200 using an in-panel gate driver (GIP) method. The gate driver 2130 can be formed in a non-display area of ​​the display panel 2200 outside the pixel array where the sub-pixels PX are formed, using the same TFT process as the sub-pixels PX.

[0197] The timing controller 2120 may include the above references Figures 1 to 19 The described gamma correction module 10 (in) Figure 1 (In the middle). The gamma correction module 10 generates compensated pixel values ​​by calculating a compensation value for the input pixel values ​​using a compensation model with a quadratic function form and applying the compensation value to the input pixel values. The timing controller 2120 can provide compensated image data, including the compensated pixel values, to the data driver 2110. The data driver IC DDIC can drive the display panel 2200 based on the compensated image data. Therefore, the quality of the image displayed on the display panel 2200 can be improved.

[0198] According to exemplary embodiments, at least one of the components, elements, modules, or units described herein can be embodied in various numbers of hardware, software, and / or firmware structures that perform the functions described above. For example, at least one of these components, elements, or units can use a direct circuit structure, such as a memory, processor, logic circuit, lookup table, etc., that can operate the corresponding function under the control of one or more microprocessors or other control devices. Furthermore, at least one of these components, elements, or units can be embodied as a portion of a module, program, or code containing one or more executable instructions for performing a specified logical function and executed by one or more microprocessors or other control devices. Moreover, at least one of these components, elements, or units can further include or be implemented by a processor, such as a central processing unit (CPU), microprocessor, etc., that performs the corresponding function. Two or more of these components, elements, or units can be combined into a single component, element, or unit that performs all the operations or functions of the elements of the combined two or more components or units. Furthermore, at least a portion of the function of at least one of these components, elements, or units can be performed by another of these components, elements, or units. Furthermore, although a bus is not shown in the block diagram, communication between components, elements, or units can be performed via a bus. The functional aspects of the above example embodiments can be implemented using algorithms executed on one or more processors. Moreover, the components, elements, or units or processing operations represented by the blocks can employ any number of techniques from the relevant art for electronic configuration, signal processing and / or control, data processing, etc.

[0199] Although the inventive concept has been specifically shown and described with reference to exemplary embodiments thereof, it should be understood that various changes in form and detail may be made without departing from the spirit and scope of the appended claims. < / k> < / k>

Claims

1. A display driving circuit, comprising: The grayscale voltage generator is configured to generate multiple grayscale voltages by linearly dividing multiple gamma tap voltages. The gamma correction module is configured to calculate a compensation value for an input pixel value by using a first gamma tap and a second gamma tap, the first gamma tap and the second gamma tap being close to the input pixel value, and is configured to apply the compensation value to the input pixel value to generate a compensated pixel value. and The data driver is configured to receive multiple grayscale voltages from a grayscale voltage generator and output data voltages corresponding to the grayscale voltages to the display panel. The grayscale voltages are selected from the multiple grayscale voltages based on compensated pixel values. The gamma correction module includes a compensation value calculator, which is configured to calculate the compensation value by performing a quadratic function of the compensation model based on the input pixel value, a first gamma tap, and a second gamma tap.

2. The display driving circuit according to claim 1, wherein, The compensation value calculator is also configured to multiply the result of a quadratic function by a weight and output the result of the multiplication as the compensation value. The weight is set for a range of pixel values ​​that includes the input pixel value.

3. The display driving circuit according to claim 1, wherein, The compensation value calculator is also configured to calculate a compensation value of zero when the input pixel value corresponds to one of the first gamma tap and the second gamma tap.

4. The display driving circuit according to claim 1, wherein, The compensation value calculator is also configured to calculate a compensation value with the maximum value when the input pixel value corresponds to the median between the first gamma tap and the second gamma tap.

5. The display driving circuit according to claim 1, wherein, The gamma correction module is also configured to generate compensated pixel values ​​by adding the compensation value to the input pixel value.

6. The display driving circuit according to claim 1, wherein, The gamma correction module is also configured to determine a weight based on at least one selected from the brightness setting of the display panel and the color of the pixel corresponding to the input pixel value, and is configured to generate a compensated pixel value by multiplying the compensation value by the weight and adding the result of the multiplication to the input pixel value.

7. The display driving circuit according to claim 1, wherein, Compensation model c model (p) is expressed by the following equation: Where p is the input pixel value, P i P is the first gamma tap with the smaller value between the two gamma taps that are closest to the input pixel value. i+1 It is the second gamma tap with the larger value between the two gamma taps.

8. The display driving circuit according to claim 1, wherein, Compensation model c model (p)′ is represented by the following equation: Where p is the input pixel value, P i P is the first gamma tap with the smaller value between the two gamma taps that are closest to the input pixel value. i+1 It is the second gamma tap with the larger value between the two gamma taps, and β is a parameter set for the range of pixel values ​​that includes the input pixel values.

9. The display driving circuit according to claim 1, further comprising: The dithering module is configured to receive the compensated pixel value from the gamma correction module, dither the compensated pixel value, and provide the dithered pixel value as the output pixel to the data driver. The output pixel value corresponds to the selected grayscale voltage.

10. The display driving circuit according to claim 1, wherein, The input pixel value and the compensated pixel value consist of M bits of data (M is a positive integer of 8 or greater), the higher-order N bits of the M bits of data including the most significant bit represent an integer (N is a positive integer less than or equal to M), and the lower-order (MN) bits of the M bits of data including the least significant bit represent a decimal number.

11. A method of operating a display driving circuit, the method comprising: The compensation value for the pixel value of the input pixel data is calculated based on the first gamma tap and the second gamma tap, which are close to the input pixel value. Generate compensated pixel values ​​based on pixel values ​​and compensation values; Based on the output pixel data including the compensated pixel values, a grayscale voltage is selected from multiple grayscale voltages; and The data voltage corresponding to the selected grayscale voltage is output to the display panel. The calculation of the compensation value includes using a compensation model to calculate the compensation value. The compensation model includes a quadratic function based on the pixel value, the first gamma tap, and the second gamma tap.

12. The method of claim 11, further comprising: Multiple gamma tap voltages are determined based on a selection signal; and Multiple grayscale voltages are generated by linearly dividing multiple gamma tap voltages.

13. The method according to claim 11, wherein, The calculation of the compensation value includes: Multiply the result of the quadratic function by the weight.

14. The method according to claim 13, wherein, The weights are set according to the range of pixel values ​​that include the pixel values, among multiple weights that are set differently for multiple ranges of pixel values.

15. The method according to claim 13, wherein, The weights are set based on at least one of the brightness settings of the display panel and the color of the pixel corresponding to the input pixel data.

16. A display device, comprising: Display panel; and The display driver circuit is configured to drive the display panel to display images. The display driving circuit includes: A grayscale voltage generator is configured to determine multiple gamma tap voltages based on multiple selection signals, and is configured to generate multiple grayscale voltages based on the multiple gamma tap voltages. A gamma correction module is configured to calculate a compensation value for an input pixel value by performing a quadratic function of a compensation model based on the input pixel value, a first gamma tap, and a second gamma tap, the first and second gamma taps being close to the input pixel value, and is configured to apply the compensation value to the input pixel value to generate a compensated pixel value; and The data driver is configured to output a data voltage corresponding to the grayscale voltage to the display panel, the grayscale voltage being selected from a plurality of grayscale voltages based on the compensated pixel values.

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