KR20220093904A - Display device and operation method thereof - Google Patents

Abstract

The present invention relates to a display device and a driving method which can provide over-driving. A reference gamma voltage generation method of a display device comprises: an operation of determining an internal reference voltage for a normal operation; an operation of determining an over-driving voltage for an over-driving operation; an operation of selecting the internal reference voltage as an AM reference voltage if the difference in an average picture level (APL) between a current frame and a previous frame is smaller than a preset threshold value; an operation of selecting the over-driving voltage as the AM reference voltage if the difference in an APL between a current frame and a previous frame is larger than or equal to a preset threshold value; and an operation of generating n reference gamma voltages based on the AM reference voltage and a second reference voltage.

Description

DISPLAY DEVICE AND OPERATION METHOD THEREOF

The present invention relates to a display device and a driving method thereof, and more particularly, to a method of generating a reference gamma voltage in a display device.

As the information society develops, various types of display devices are being developed. Recently, display devices using various technologies such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting display (OLED) have been commercialized.

A display device includes pixels, and controls a voltage input to each pixel so that the pixels emit light with a corresponding luminance. However, when a specific pixel is changed from black to white, that is, from the lowest to highest luminance, it may not be immediately changed due to characteristics of the output buffer driving the pixel, such as a slew rate. Then, the pixel may not change from black to white immediately, and blur may occur.

This problem can be solved through over driving in which an overvoltage is applied to the corresponding pixel. Conventionally, a data re-scaling method by algorithmic processing has been used. However, this method reduces the maximum luminance and then overdrives using the extra secured accordingly, and there is a problem that the overall luminance is lowered. There is a problem with doing

The present specification intends to propose a new method for providing overdriving in consideration of the problems caused by the above-described conventional algorithm processing.

The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. There will be.

According to various embodiments of the present disclosure, a display device includes a display panel including a plurality of data lines, a plurality of gate lines, and a plurality of pixels disposed at intersections of the plurality of data lines and the plurality of gate lines; A timing controller that processes an image signal and a control signal received from the display panel to generate data, a data driving control signal, and a gate driving control signal for outputting the image signal to the display panel, and a reference gamma voltage generator that generates a reference gamma voltage set a data driver configured to determine a gamma voltage corresponding to a grayscale based on the reference gamma voltage set, and output data voltages for a plurality of data lines of the display panel based on the gamma voltage and data received from the timing controller , a gate driver outputting a gate signal to each of the plurality of gate lines of the display panel, and wherein the reference gamma voltage generator determines that a difference between an average picture level (APL) of a current frame and a previous frame is less than a preset threshold value. generates a reference gamma voltage set based on the internal reference voltage, and when the difference between the APL of the current frame and the previous frame is greater than or equal to a preset threshold value Based on the reference gamma voltage set can be generated.

According to various embodiments of the present disclosure, the reference gamma voltage generating circuit selects the reference gamma voltage set based on the internal reference voltage when the difference between the average picture level (APL) of the current frame and the previous frame is less than a preset threshold value. and, when the difference between the APLs of the current frame and the previous frame is greater than or equal to a preset threshold, a reference gamma voltage set may be generated based on an over driving voltage lower than the internal reference voltage.

According to various embodiments of the present disclosure, the method of generating a reference gamma voltage of a display device includes an operation of determining an internal reference voltage for a normal operation, an operation of determining an overdriving voltage for an overdriving operation, and APL of a current frame and a previous frame. When the difference between (average picture level) is smaller than a preset threshold, selecting the internal reference voltage as the AM reference voltage, when the difference between the APL of the current frame and the previous frame is greater than or equal to the preset threshold, The method may include selecting the overdriving voltage as the AM reference voltage and generating n reference gamma voltages based on the AM reference voltage and a second reference voltage.

Various methods proposed in the present specification provide overdriving even with a sudden change in brightness to prevent brightness degradation and improve blur caused by movement.

Various methods proposed in the present specification provide overdriving by directly controlling the gamma voltage, thereby providing overdriving without a re-optical compensation process.

Effects obtainable in the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present disclosure belongs from the description below. will be.

1 is a diagram illustrating a schematic configuration of a display device according to an exemplary embodiment.
2 is a diagram illustrating a schematic configuration of the data driver 130 .
3 is a diagram illustrating an example of the DAC unit 230 for one data line DLk.
4 is a diagram illustrating a circuit diagram of a reference gamma voltage generator 250 according to an exemplary embodiment.
5 is a diagram illustrating an example in which blur occurs in the original text area when the text is moved downward.
Fig. 6 is a diagram showing an example of the result of luminance showing the situation of Fig. 5;
7 is a diagram illustrating an example in which a reference gamma voltage generator provides a voltage for overdriving.
8 is a diagram illustrating a luminance result when overdriving is performed.
9 is a diagram illustrating another example in which a reference gamma voltage generator provides a voltage for overdriving.
10 is a flowchart illustrating an operation of a display device for generating a reference gamma voltage.
In connection with the description of the drawings, the same or similar reference numerals may be used for the same or similar components.

Like reference numerals refer to substantially identical elements throughout. In addition, in the drawings, thicknesses, ratios, and dimensions of components may be exaggerated for effective description of technical content.

When a component (or region, layer, portion, etc.) is referred to as being “on,” “connected to,” or “coupled to” another component, it may be directly connected/coupled onto the other component or or a third component may be disposed between them. In addition, terms such as "below", "below", "above", and "upper side" are used to describe the relationship of the components shown in the drawings. The above terms are relative concepts, and are described based on directions indicated in the drawings. Terms such as “comprise” or “have” are intended to designate that a feature, number, step, action, component, part, or combination thereof described in the specification is present, and includes one or more other features, number, or step. , it should be understood that it does not preclude the possibility of the existence or addition of an operation, a component, a part, or a combination thereof.

“and/or” includes any combination of one or more that the associated configurations may define. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the following description, if it is determined that a detailed description of a known technology or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, the component names used in the following description may be selected in consideration of ease of writing the specification, and may be different from the component names of the actual product.

Hereinafter, various embodiments will be described in detail according to the accompanying drawings.

1 is a diagram illustrating a schematic configuration of a display device according to an exemplary embodiment.

Referring to FIG. 1 , a display device 100 according to an embodiment may include a display panel 110 , a gate driver 120 , a data driver 130 , and a timing controller 140 .

The gate driver 120 , the data driver 130 , and the timing controller 140 may constitute a display driver of the display device 100 .

The gate driver 120 is connected to the pixels PX of the display panel 110 through the gate lines GL1 to GLn. The gate driver 120 generates a gate signal based on the gate driving control signal GCS output from the timing controller 140 . The gate driver 120 provides the generated gate signals to the pixels PX through the gate lines GL1 to GLn.

The data driver 130 is connected to the pixels PX of the display panel 110 through the data lines DL1 to DLm. The data driver 130 generates data signals based on the image data DATA and the data driving control signal DCS output from the timing controller 140 . The data driver 130 provides the generated data signals to the pixels PX through the data lines DL1 to DLm.

The timing controller 140 processes an image signal and a control signal (eg, a horizontal synchronization signal, a vertical synchronization signal, and a main clock signal, etc.) received from the outside to suit the operating conditions of the display panel 110 , and thus image data (DATA), the gate driving control signal GCS, and the data driving control signal DCS may be generated and output.

A plurality of pixels PX are disposed on the display panel 110 . The pixels PX may be formed at intersections of the gate lines GL1 to GLn and the data lines DL1 to DLm. For example, the pixels PX may be arranged in a matrix form on the display panel 110 .

Each pixel PX may be connected to a corresponding gate line GL1 to GLn and a data line DL1 to DLm. The pixels PX may emit light with corresponding luminance according to the data signal supplied to the data lines DL1 to DLm in synchronization with the supply timing of the gate signal supplied to the gate lines GL1 to GLn.

Depending on the type of the display device 100 , the pixels PX may include a liquid crystal or a light emitting device. For example, when the display device 100 is a liquid crystal display device, the display device 100 may include a light source (eg, a backlight unit) irradiating light to the display panel 110 , and the pixels PX ) may include a pixel electrode, a common electrode COM, and a liquid crystal. When an electric field is formed between the pixel electrode and the common electrode COM in response to the data voltage applied to the pixel PX, the arrangement of the liquid crystal is adjusted. Accordingly, the transmittance of the light irradiated from the light source is adjusted, so that each pixel PX may emit light with a luminance corresponding to the data signal.

Alternatively, for example, when the display device 100 is an organic light emitting diode display, the pixels PX may include an organic light emitting diode. In this case, each pixel PX may emit light with a luminance corresponding to the data signal by controlling the driving current flowing to the organic light emitting diode according to the voltage of the data signal.

Each of the gate driver 120 , the data driver 130 , and the timing controller 140 may be configured as a separate integrated circuit (IC) or may be configured as at least a part of an integrated circuit. For example, the data driver 130 may be configured as an integrated circuit integrated with the timing controller 140 .

Also, although the gate driver 120 and the data driver 130 are illustrated as separate components from the display panel 110 in FIG. 1 , at least one of the gate driver 120 and the data driver 130 is included in the display panel 110 . ) and may be configured in an in-panel method that is integrally formed. For example, the gate driver 120 may be integrally formed with the display panel 110 according to a gate in panel (GIP) method.

2 is a diagram illustrating a schematic configuration of the data driver 130 .

Referring to FIG. 2 , the data driving unit 130 may include a shift unit 210 , a latch unit 220 , a digital-to-analog converter (DAC) unit 230 , and an output circuit unit 240 . Although it is disclosed that the reference gamma voltage generator 250 is not included in the data driver 130 in FIG. 2 , in another embodiment, the reference gamma voltage generator 250 may be included in the data driver 130 .

The shift unit 210 may output a sampling signal by shifting the pulse signal according to the data sampling clock supplied from the timing control unit 140 .

The latch unit 220 samples the image data DATA input from the timing controller 140 in response to the sampling signal sequentially input from the shift unit 210 , and applies the data to each horizontal line by one horizontal line. After latching, data for one horizontal line can be output simultaneously.

The DAC unit 230 may decode digital data input from the latch unit 220 and output positive/negative gamma compensation voltages corresponding to grayscale values of the data as analog data voltages Vd1 to Vdm.

In general, gradation refers to a step-by-step division of the amount of light perceived by human eyes. Human vision responds non-linearly to the brightness of light. For this reason, when the brightness of light is linearly expressed using digital data of limited bits, such as 8 bits, for each data line, a phenomenon in which the change of the screen is not smooth and disconnected may occur to the human eye. Therefore, in order to show optimal image quality within the limit of the amount of information that a limited bit of given digital data can express, it is necessary to encode it non-linearly. To this end, an operation of matching the difference between the driving characteristics of the display panel and the human visual perception characteristics is performed, which is referred to as gamma correction. In general, the gamma correction method sets a plurality of gamma reference voltage values according to characteristics of a display panel and divides the set gamma reference voltage values to compensate for each gamma value of input digital video data.

Accordingly, the DAC unit 230 generates a gamma voltage corresponding to the grayscale value of digital data, that is, an analog data voltage, using the reference gamma voltage RGV generated by the reference gamma voltage generator 250 . can According to an embodiment, the DAC unit 230 may generate a gamma voltage for each grayscale value using a resistance string. The resistance string may be formed by connecting a plurality of resistors in series between the gamma voltage GV255 when the luminance is highest (white) and the gamma voltage GV0 when the luminance is the lowest (black). For example, when the number of bits of digital data is 8, the grayscale value may range from 0 to 255, and the resistance string may be a series of 256 resistors having the same value connected to generate a gamma voltage corresponding thereto.

3 is a diagram illustrating an example of the DAC unit 230 for one data line DLk.

Referring to FIG. 3 , the DAC unit 230 receives a plurality of reference gamma voltages RGV255, RGV191, RGV127, RGV95, RGV63, RGV47, RGV31, RGV23, RGV15, RGV7, RGV1, RGV0 from the reference gamma voltage generator 250 . ) and connecting resistors in series between the plurality of reference gamma voltages to generate gamma voltages GV0 to GV255 using a resistor string that can be divided.

The DAC unit 230 selects one gamma voltage from among the plurality of gamma voltages GV0 to GV255 based on the data DATAk latched by the latch unit 220 using a multiplexer (MUX) 231k. Thus, the analog data voltage Vdk can be output. In the example of FIG. 3 , it is assumed that the number of gamma voltages is 256 and the number of received reference gamma voltages is 12, but this is not possible in one embodiment. Accordingly, the number of gamma voltages may vary, and the number of reference gamma voltages and input reference gamma voltages may also vary.

The output circuit unit 240 may output the data voltages Vd1 to Vdm to the data lines DL1 to DLm. The output circuit unit 240 includes a plurality of output buffers, and each of the plurality of output buffers receives the analog data voltages Vd1 to Vdm from the DAC unit 230 , and transmits the analog data voltages Vd1 to Vdm to the data lines ( DL1 to DLm) can be output. Each of the output buffers may be an operational amplifier.

The reference gamma voltage generator 250 may generate a reference gamma voltage RGV necessary for the DAC 230 to generate a gamma voltage. The reference gamma voltage generator 250 generates a gamma voltage of the highest luminance RGV255 and a gamma voltage RGV0 of the lowest luminance as well as a plurality of intermediate luminance gamma voltages RGV191 to generate a nonlinear gamma voltage. , RGV127, etc.).

The reference gamma voltage RGV generated by the reference gamma voltage generator 250 may be different depending on the driving characteristics of the display panel, whether the display panel has a positive polarity or a negative polarity, and whether it is for a red pixel, a green pixel, or a blue pixel.

4 is a diagram illustrating a circuit diagram of a reference gamma voltage generator 250 according to an exemplary embodiment.

Referring to FIG. 4 , the reference gamma voltage generator 250 may include a plurality of resistance strings 410 to 415 , a plurality of multiplexers 420 to 427 , and a plurality of buffers.

Referring to FIG. 4 , the reference gamma voltage generator 250 determines a first reference voltage VREG1_REFS and a second reference voltage VREG1_REFS based on an input VREG1 to determine a reference gamma voltage RGV255 to be used to display the highest luminance. An internal reference voltage VREG1_IREFS may be determined between two reference voltages VREG1_REFE. For example, 4096 voltages are generated using a resistance string 410 in which the same resistance is connected in series between the first reference voltage VREG1_REFS and the second reference voltage VREG1_REFE, and the multiplexer 420 is a control signal It is possible to select one of the divided 4096 voltages using VREG1 and output it through the buffer 430 . The output voltage VREG1_IREFS may be an internal reference voltage for generating a subsequent reference gamma voltage. That is, the reference gamma voltage generator 250 may generate reference gamma voltages between the internal reference voltage VREG1_IREFS and the second reference voltage VREG1_REFE.

According to an embodiment, the reference gamma voltage generator 250 may generate a plurality of reference gamma voltages through two steps. Step 1 generates a plurality of voltages using a resistance string 411 in which the same resistance is connected in series between the internal reference voltage VREG1_IREFS and the second reference voltage VREG1_REFE, and the multiplexer 421 sends the control signal AM2 ), a reference gamma voltage RGV255 for the highest luminance may be generated by selecting one of the plurality of voltages and outputting it through the buffer 431 . In addition, the multiplexer 423 selects one of the plurality of voltages generated by the resistance string 411 using the control signal AM0 and outputs it through the buffer 433, thereby providing a reference gamma voltage RGV0 for the lowest luminance. ) can be created. In addition, the multiplexer 422 may select one of a plurality of voltages generated by the resistance string 411 using the control signal AM1 and output it through the buffer 432 , and the output voltage is an intermediate level luminance. It may be a third reference voltage VREG3_REFE for generating a reference gamma voltage for .

The reference gamma voltage generator 250 may generate reference gamma voltages RGV191, RGV127, RGV95, RGV63, RGV47, RGV31, RGV23, RGV15, RGV7, and RGV1 for intermediate-level luminance in step 2 . The reference gamma voltage for each intermediate stage luminance is a resistor string (412, 413, 414, 415) connected in series with the same resistance between the previously generated reference gamma voltage and the third reference voltage (VREG3_REFE) generated in the first stage. may be generated by selecting and outputting one of a plurality of voltages generated using

For example, the reference gamma voltage RGV191 includes the control signal GR9 and the multiplexer 424 among 512 voltages divided between the reference gamma voltage RGV255 and the third reference voltage VREG3_REFE using the resistance string 412 . ) to select one voltage and output it through the buffer 434 . In addition, the reference gamma voltage RGV127 is a control signal GR8 and a multiplexer 425 from among 512 voltages divided between the reference gamma voltage RGV191 and the third reference voltage VREG3_REFE using the resistance string 413 . It may be generated by selecting one voltage by using and outputting it through the buffer 435 . In addition, the reference gamma voltage RGV7 is a control signal GR1 and a multiplexer 426 from among 512 voltages divided between the reference gamma voltage RGV15 and the third reference voltage VREG3_REFE using the resistance string 414 . may be generated by selecting one voltage using ? and outputting it through the buffer 436 . In addition, the reference gamma voltage RGV1 is a control signal GR0 and a multiplexer 427 from among 512 voltages divided between the reference gamma voltage RGV7 and the third reference voltage VREG3_REFE using the resistance string 415 . It may be generated by selecting one voltage by using and outputting it through the buffer 437 . Other reference gamma voltages may be similarly generated.

Through the above-described method, the reference gamma voltage generator 250 may generate and output the reference gamma voltage set. According to an embodiment, the reference gamma voltage set includes 12 reference gamma voltages, but is not limited thereto.

According to an embodiment, the reference gamma voltage RGV0 providing the lowest luminance to express black may be 5.49V, and the reference gamma voltage RGV255 providing the highest luminance to express white may be 3.47V. have.

The reference gamma voltage generator shown in FIG. 4 is an example and may be generated in other ways.

5 is a diagram illustrating an example in which blur occurs in the original text area when the text is moved downward.

Referring to FIG. 5 , when the character at the position 510 as shown in FIG. 5(a) moves to the lower position 520 as shown in FIG. 5(b), FIG. 5(c) Alternatively, as shown in (d), blur may occur in which an afterimage remains in the previous position 510 where the letters were. This may mean that the luminance in the corresponding pixel is changed from the lowest luminance to the highest luminance in the first frame in which the luminance is changed. That is, the voltage applied to the data line for the corresponding pixel changes from V0 to V255. However, due to the slew rate of the output buffer, the length of the on period of the gate signal, the minimization of power consumption, etc., the voltage applied to the data line may not decrease enough to indicate the desired luminance. However, after the second frame, the afterimage may disappear as a voltage suitable for the desired luminance may be applied to the data line.

Fig. 6 is a diagram showing an example of the result of luminance showing the situation of Fig. 5;

Referring to FIG. 6 , in frame 0, the voltage V0 for the lowest luminance 610 of black may be applied to operate. And as the letters go down, the corresponding position should be displayed in white color, so the voltage V255 for the highest luminance 620 may be applied. However, due to the above-mentioned various factors, the luminance 630 before reaching the maximum luminance 620 may be maintained in the frame 1, and the desired maximum luminance 620 may also be operated in the frame 2 . As a result, an afterimage as shown in FIG. 5 may remain and blur may occur.

In order to suppress the occurrence of such blur, in the first frame (eg, frame 1) in which the luminance is changed, the luminance is raised by over-driving in which a voltage greater than the voltage V255 is applied to achieve the desired luminance 255G. can However, in the case of white, since the voltage V255 for the highest luminance 255G is already applied, a lower voltage cannot be applied based on FIGS. 3 and 4 . To this end, a re-scaling method of lowering the voltage by a predetermined ratio is used, but this does not reach the desired luminance, and additional re-calibration is required to reach the desired luminance.

Accordingly, the present specification proposes a method in which the reference gamma voltage generator provides the overdriving voltage by changing the reference gamma voltage when overdriving is performed.

7 is a diagram illustrating an example in which a reference gamma voltage generator provides a voltage for overdriving.

For overdriving, a voltage lower than the voltage V255 corresponding to the conventional white luminance should be applied to the data line.

To this end, in the present specification, referring to FIG. 7 , in the structure of the conventional reference gamma voltage generator 250 of FIG. 4 , two multiplexers 720 and 740 and one buffer 730 are added to the circuit, and the two multiplexers Control signals V256_OD and OD_SEL for controlling 720 and 740 may be added.

The multiplexer 720 is for selecting a voltage (V256_ODV) to be applied when overdriving is performed. The multiplexer 720 receives the voltages divided by the resistance string 410 as an input, and among them, a control signal (V256_OD) The voltage V256_ODV selected by ? may be output through the buffer 730 . At this time, the overdriving voltage V256_ODV output from the multiplexer 720 is a voltage that can provide a higher luminance than the internal reference voltage VREG1_IREFS output from the multiplexer 420, and according to an embodiment, the internal reference voltage VREG1_IREFS It may be a lower voltage. For example, the second reference voltage VREG1_REFE may be 5.49V, the internal reference voltage VREG1_IREFS may be 3.47V, and the over driving voltage V256_ODV may be 2V versus a voltage (eg, 2.84V). have. Here, the control signal OD_SEL for controlling the multiplexer 740 may be determined based on an average picture level (APL) of an image. For example, when the APL of the current frame and the APL of the previous frame are compared and larger than a preset threshold value, the overdriving voltage V256_ODV becomes the reference voltage AM2_REF of the resistance string 411, and vice versa, the internal reference The voltage VREG1_IREFS may be the reference voltage AM2_REF of the resistance string 411 . Accordingly, when the average brightness of the image is greater than the threshold value of the previous frame, the overdriving voltage V256_ODV is applied as a reference voltage, and thus the reference gamma voltage RGV may increase as a whole.

8 is a diagram illustrating a luminance result when overdriving is performed.

Referring to FIG. 8 , as the APL difference between frame 0 and frame 1 becomes larger than the threshold value, overdriving is performed, and the reference voltage AM2_REF of FIG. 7 may be the overdriving voltage V256_ODV output from the mixer 720 . have. The overdriving voltage V256_ODV may be output to the reference gamma voltage RGV255 by selection of the control signal AM2 . In the case of white, digital data has a value of 255 (8'b1111111), and as a result, a corresponding analog voltage V255 may be output to the data line. As overdriving is performed, the voltage V255 may be the overdriving voltage V256_ODV. Accordingly, the luminance may be raised to the luminance 620 rather than the conventional value 630 .

On the other hand, as the difference in APL between frame 1 and frame 2 becomes smaller than the threshold (if frame 1 and frame 2 are the same, the difference in APL may be 0), the voltage (V255) determined by the original internal reference voltage (VREG_IREFS) ) can be returned.

That is, the control signal OD_SEL becomes 'high' in frame 1 to allow overdriving to be performed, and in another frame, the control signal OD_SEL becomes low to 'low' so that overdriving is not performed. Normal operation can be performed without

9 is a diagram illustrating another example in which a reference gamma voltage generator provides a voltage for overdriving.

For overdriving, a voltage lower than the voltage V255 corresponding to the conventional white luminance should be applied to the data line.

To this end, in the present specification, referring to FIG. 9 , in the structure of the conventional reference gamma voltage generator 250 of FIG. 4 , one multiplexer 910 is added to a circuit, and a control signal OD_SEL for controlling the multiplexer 910 . ) and a signal (V256_OD) for overdriving voltage selection can be added.

The multiplexer 910 receives one of a selection signal V256_OD for selecting a voltage to be applied when overdriving is performed or a selection signal VREG1 for selecting a voltage to be applied when performing a normal operation as a control signal ( OD_SEL) can be used to select. In this case, the overdriving voltage selected by the selection signal V256_OD may be lower than the internal reference voltage selected by the selection signal VREG1 . For example, the second reference voltage VREG1_REFE may be 5.49V, the internal reference voltage selected by the selection signal VREG1 may be 3.47V, and the overdriving voltage selected by the selection signal V256_OD is It may be 2V vs. voltage (eg 2.84V). Here, the signal OD_SEL controlling the multiplexer 910 may be determined based on an average picture level (APL) of an image. For example, when the APL of the current frame is compared with the APL of the previous frame and is larger than a preset threshold, the selection signal V256_OD is output from the multiplexer 910 and the selection signal V256_OD is output from the multiplexer 420 by The selected overdriving voltage becomes the reference voltage AM2_REF of the resistance string 411 , and vice versa, the selection signal VREG1 is output from the multiplexer 910 and selected by the selection signal VREG1 from the multiplexer 420 . The internal reference voltage used may be the reference voltage AM2_REF of the resistance string 411 . Accordingly, when the average brightness of the image is greater than the threshold value of the previous frame, the overdriving voltage is applied as a reference voltage for generating the reference gamma voltage, and thus the reference gamma voltage RGV may increase as a whole.

10 is a flowchart illustrating an operation of a display device for generating a reference gamma voltage.

Referring to FIG. 10 , in operation S100 , the display device may determine an internal reference voltage for a normal operation. Here, the normal operation may be a normal operation in a concept opposite to the overdriving operation. When the data line is driven using the gamma voltage generated based on the reference gamma voltage generated based on the internal reference voltage, a normal operation may be performed in a situation where a desired luminance can be obtained.

In operation S200 , the display device may determine an overdriving voltage for the overdriving operation. When the data line is driven using the gamma voltage generated based on the internal reference voltage for normal operation, when the desired luminance cannot be obtained for various reasons, the voltage applied during normal operation to obtain the desired luminance and eliminate blur A lower overdriving voltage may be applied. The operation of applying such an overdriving voltage may be referred to as an overdriving operation, and the overdriving voltage may be determined to obtain a desired luminance through the overdriving operation.

In operations S300 and S400, an average picture level (APL) difference between the current frame and the previous frame may be compared with a preset threshold value. When the APL difference between the current frame and the previous frame is smaller than a preset threshold, desired luminance can be obtained even with a normal operation, so the internal reference voltage can be selected as the AM reference voltage. Conversely, if the APL difference between the current frame and the previous frame is greater than or equal to the preset threshold, it is determined that the desired luminance cannot be obtained through normal operation, so it is decided to perform the overdriving operation, and the overdriving voltage is set as the AM reference voltage. You can choose.

In operation S500, the display device may generate n reference gamma voltages based on the AM reference voltage and the second reference voltage corresponding to the lowest luminance.

As described above, the present invention proposes a method of increasing the reference gamma voltage in order to supply the overdriving voltage to the data line. That is, by increasing the reference gamma voltage, the gamma voltage applied to the data line may increase according to the gray level. Accordingly, it is possible to solve the problems of reducing luminance and re-calibration of the conventional overdriving method.

100: display device
110: display pixel
120: gate driver
130: data driving unit
140: timing control
210: shift unit
220: letchibu
230: DAC unit
240: output circuit unit
250: reference gamma voltage generator

Claims (13)

In the display device,
a display panel including a plurality of data lines, a plurality of gate lines, and a plurality of pixels disposed at intersections of the plurality of data lines and the plurality of gate lines;
a timing controller for processing an image signal and a control signal received from the outside to generate data for outputting the image signal to the display panel, a data driving control signal, and a gate driving control signal;
a reference gamma voltage generator generating a reference gamma voltage set;
a data driver determining a gamma voltage corresponding to a grayscale based on the reference gamma voltage set and outputting data voltages for a plurality of data lines of the display panel based on the gamma voltage and data received from the timing controller;
a gate driver outputting a gate signal to each of the plurality of gate lines of the display panel;
The reference gamma voltage generator,
When the difference between the average picture level (APL) of the current frame and the previous frame is less than a preset threshold, a reference gamma voltage set is generated based on the internal reference voltage;
When a difference between the APL of the current frame and the previous frame is greater than or equal to a preset threshold, the display device generates a reference gamma voltage set based on an over driving voltage lower than the internal reference voltage.
According to claim 1,
The reference gamma voltage generator,
a first resistance string for generating a plurality of voltages between the first reference voltage and the second reference voltage;
a first multiplexer for selecting one voltage from among a plurality of voltages generated by the first resistor string and outputting it as an internal reference voltage;
a second multiplexer for selecting one voltage from among a plurality of voltages generated by the first resistor string and outputting it as an overdriving voltage;
a third multiplexer selecting one of the internal reference voltage and the over-driving voltage and outputting it as an AM reference voltage;
a second resistance string for generating a plurality of voltages between the second reference voltage and the AM reference voltage;
a reference gamma voltage generating module for generating n reference gamma voltages based on the plurality of voltages generated by the second resistance string;
The third multiplexer,
When the difference between the average picture level (APL) between the current frame and the previous frame is less than a preset threshold, the internal reference voltage is selected and output as the AM reference voltage, and the difference between the APL between the current frame and the previous frame is set in advance. When it is greater than or equal to a set threshold value, the overdriving voltage is selected and output as the AM reference voltage.
According to claim 1,
The reference gamma voltage generator,
a first resistance string for generating a plurality of voltages between the first reference voltage and the second reference voltage;
a first multiplexer that selects one voltage from among a plurality of voltages generated by the first resistor string based on an input control signal and outputs the selected voltage as an AM reference voltage;
a fourth multiplexer for selecting one selection signal from among a first selection signal for determining an overdriving voltage and a second selection signal for determining an internal reference voltage and outputting the selected signal as the control signal of the first multiplexer;
a second resistance string for generating a plurality of voltages between the second reference voltage and the AM reference voltage;
a reference gamma voltage generating module for generating n reference gamma voltages based on the plurality of voltages generated by the second resistance string;
The fourth multiplexer,
When the difference between the average picture level (APL) of the current frame and the previous frame is less than a preset threshold, the second selection signal is selected and output, and the difference between the APL of the current frame and the previous frame is greater than the preset threshold. If greater than or equal to, the display device selects and outputs the first selection signal.
4. The method of claim 2 or 3,
The reference gamma voltage generating module includes:
a fifth multiplexer for selecting one of a plurality of voltages generated by the second resistance string and outputting it as a first reference gamma voltage;
a sixth multiplexer that selects one of a plurality of voltages generated by the second resistance string and outputs an nth reference gamma voltage;
a seventh multiplexer for outputting a third reference voltage by selecting one of a plurality of voltages generated by the second resistance string;
a k+1th resistance string generating a plurality of voltages between the k+1th reference gamma voltage and the third reference voltage, wherein k is a natural number from n-1 to 2; and
and a k+6th multiplexer that selects one voltage from among a plurality of voltages generated by the k+1th resistance string and outputs it as a kth reference gamma voltage.
5. The method of claim 4,
the third reference voltage is smaller than the first reference gamma voltage;
and the nth reference voltage is selected to be smaller than the third reference voltage.
6. The method of claim 5,
the fifth multiplexer selects the second reference voltage as the first reference gamma voltage;
and the sixth multiplexer selects the AM reference voltage as the nth reference gamma voltage.
In the reference gamma voltage generation circuit,
When the difference between the average picture level (APL) of the current frame and the previous frame is less than a preset threshold, a reference gamma voltage set is generated based on the internal reference voltage;
A reference gamma voltage generating circuit configured to generate a reference gamma voltage set based on an over driving voltage lower than the internal reference voltage when a difference between APLs of the current frame and the previous frame is greater than or equal to a preset threshold.
8. The method of claim 7,
a first resistance string for generating a plurality of voltages between the first reference voltage and the second reference voltage;
a first multiplexer for selecting one voltage from among a plurality of voltages generated by the first resistor string and outputting it as an internal reference voltage;
a second multiplexer for selecting one voltage from among a plurality of voltages generated by the first resistor string and outputting it as an overdriving voltage;
a third multiplexer selecting one of the internal reference voltage and the over-driving voltage and outputting it as an AM reference voltage;
a second resistance string for generating a plurality of voltages between the second reference voltage and the AM reference voltage;
a reference gamma voltage generating module for generating n reference gamma voltages based on the plurality of voltages generated by the second resistance string;
The third multiplexer,
When the difference between the average picture level (APL) between the current frame and the previous frame is less than a preset threshold, the internal reference voltage is selected and output as the AM reference voltage, and the difference between the APL between the current frame and the previous frame is set in advance. The reference gamma voltage generation circuit, wherein the overdriving voltage is selected and output as the AM reference voltage when it is greater than or equal to a set threshold value.
8. The method of claim 7,
a first resistance string for generating a plurality of voltages between the first reference voltage and the second reference voltage;
a first multiplexer that selects one voltage from among a plurality of voltages generated by the first resistor string based on an input control signal and outputs the selected voltage as an AM reference voltage;
a fourth multiplexer for selecting one selection signal from among a first selection signal for determining an overdriving voltage and a second selection signal for determining an internal reference voltage and outputting the selected signal as the control signal of the first multiplexer;
a second resistance string for generating a plurality of voltages between the second reference voltage and the AM reference voltage;
a reference gamma voltage generating module for generating n reference gamma voltages based on the plurality of voltages generated by the second resistance string;
The fourth multiplexer,
When the difference between the average picture level (APL) of the current frame and the previous frame is less than a preset threshold, the second selection signal is selected and output, and the difference between the APL of the current frame and the previous frame is greater than the preset threshold. A reference gamma voltage generating circuit that selects and outputs the first selection signal when it is greater than or equal to.
10. The method according to claim 8 or 9,
The reference gamma voltage generating module includes:
a fifth multiplexer for selecting one of a plurality of voltages generated by the second resistance string and outputting it as a first reference gamma voltage;
a sixth multiplexer that selects one of a plurality of voltages generated by the second resistance string and outputs an nth reference gamma voltage;
a seventh multiplexer for outputting a third reference voltage by selecting one of a plurality of voltages generated by the second resistance string;
a k+1th resistance string generating a plurality of voltages between the k+1th reference gamma voltage and the third reference voltage, wherein k is a natural number from n-1 to 2; and
and a k+6th multiplexer for selecting one voltage from among a plurality of voltages generated by the k+1th resistance string and outputting it as a kth reference gamma voltage.
11. The method of claim 10,
the third reference voltage is smaller than the first reference gamma voltage;
and the nth reference voltage is selected to be smaller than the third reference voltage.
12. The method of claim 11,
the fifth multiplexer selects the second reference voltage as the first reference gamma voltage;
and the sixth multiplexer selects the AM reference voltage as the nth reference gamma voltage.
A method of generating a reference gamma voltage for a display device, the method comprising:
determining an internal reference voltage for normal operation;
determining an over-driving voltage for an over-driving operation;
selecting the internal reference voltage as the AM reference voltage when the difference between the average picture level (APL) of the current frame and the previous frame is less than a preset threshold;
selecting the overdriving voltage as the AM reference voltage when a difference between the APLs of the current frame and the previous frame is greater than or equal to a preset threshold; and
and generating n reference gamma voltages based on the AM reference voltage and a second reference voltage.

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