KR102274737B1 - Circuit for generating a gamma data voltage and organic light emitting display device including the same - Google Patents

Abstract

A gamma data voltage generation circuit is provided. A first gamma unit for outputting a gamma reference voltage for a preset reference gray based on the brightness control signal, a second gamma unit for outputting a gamma selection voltage for a reference gray based on the brightness control signal, and a gamma reference voltage and a brightness control unit that receives the gamma selection voltage and selects a gamma point voltage for a reference grayscale having a data value between the data value of the gamma reference voltage and the data value of the gamma selection voltage. The gamma data voltage generation circuit according to an embodiment of the present invention may provide a gamma point voltage that is changed to correspond to the rate of change of the data value of the brightness control signal through the first gamma unit, the second gamma unit, and the brightness control unit.

Description

Gamma data voltage generating circuit and organic light emitting display device including same {CIRCUIT FOR GENERATING A GAMMA DATA VOLTAGE AND ORGANIC LIGHT EMITTING DISPLAY DEVICE INCLUDING THE SAME}

The present invention relates to a gamma data voltage generating circuit and an organic light emitting diode display including the same, and more particularly, to a gamma data voltage generating circuit for generating a gamma data voltage that is increased or decreased to correspond to a change in a brightness control signal and includes the same It relates to an organic light emitting display device.

An organic light emitting display device is a self-emissive display device, and unlike a liquid crystal display device, it does not require a separate light source, so it can be manufactured in a light and thin shape. In addition, the organic light emitting diode display is being researched as a next-generation display because it is advantageous in terms of power consumption due to low voltage driving, and also has excellent response speed, viewing angle, and contrast ratio.

In particular, in recent years, as organic light emitting display devices are widely used in mobile devices such as smartphones, tablet PCs, personal digital assistants (PDAs), etc., the brightness of the screen is automatically changed according to the surrounding illuminance, or the user's screen An organic light emitting diode display in which the brightness of a screen is adjusted based on a brightness control command is widely used.

The screen brightness of the organic light emitting diode display may be controlled by adjusting the overall voltage value of the gamma data voltage provided from the data driver of the organic light emitting diode display according to the brightness control signal. For example, when the data value of the brightness control signal is increased, the brightness of the organic light emitting diode display is increased by overall increasing the voltage value of the gamma data voltage so that the organic light emitting diode of the organic light emitting diode display can be driven with bright luminance. brighten up

However, this driving method causes a problem of reducing color reproducibility of the organic light emitting diode display. In general, an organic light emitting diode of an organic light emitting diode display has different efficiencies for each gray level. For example, a gamma data voltage required to realize the same luminance in an organic light emitting diode of a low gray level may be higher than that of an organic light emitting diode of a high gray level. In addition, since the optical compensation to be applied to the organic light emitting diode display varies according to the overall brightness of the organic light emitting diode display, the gamma data voltage corresponding to each gray level may also change. Accordingly, when the overall voltage value of the gamma data voltage is increased to increase the brightness of the organic light emitting diode display, the luminance is different for each gray level. Accordingly, there is a problem that the data value of the brightness control signal and the brightness shown in the actual organic light emitting display do not match each other. As the data value of the brightness control signal changes, the color of the organic light emitting display is also changed to emit light. There is a problem that the color reproducibility of the display device is deteriorated.

Gamma data voltage generator and display device (Patent Application No. 2012-0155443)

The inventors of the present invention have recognized that when the data value of the gamma data voltage is equally increased or decreased for all grayscales, the luminance of the organic light emitting diode is different for each grayscale. Accordingly, the inventor of the present invention can adjust the data value of the gamma data voltage differently for each gray level using a plurality of brightness control units, so that the brightness can be smoothly brightened or darkened according to the brightness control signal without deterioration of color reproducibility. The organic light emitting display device was invented.

Accordingly, an object of the present invention is to provide a gamma data voltage generation circuit that outputs a gamma data voltage that is increased or decreased to correspond to a change rate of a data value of a brightness control signal.

Another object of the present invention is to increase or decrease the data value of the gamma data voltage to correspond to the rate of change of the data value of the brightness control signal, thereby smoothly changing the brightness of the screen and minimizing the degradation of color reproducibility. To provide a display device.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, a gamma data voltage generating circuit according to an embodiment of the present invention includes a first gamma unit, a second gamma unit, a brightness control unit, and a gamma data voltage output unit. The first gamma unit outputs a gamma reference voltage for a preset reference gray level based on the brightness control signal. The second gamma unit outputs a gamma selection voltage for the reference grayscale based on the brightness control signal. The brightness controller receives the gamma reference voltage and the gamma selection voltage, and selects and outputs the gamma point voltage for the reference grayscale having a voltage value between the voltage value of the gamma reference voltage and the voltage value of the gamma selection voltage. The gamma data voltage output unit receives the gamma point voltage and divides the gamma point voltage to output the gamma data voltage. The gamma data voltage generation circuit according to an embodiment of the present invention provides a gamma point voltage that changes to correspond to a rate of change of the brightness control signal through the first gamma unit, the second gamma unit, and the brightness control unit, so that the gamma data voltage is adjusted to the brightness. It may be increased or decreased to correspond to the rate of change of the data value of the signal. Accordingly, the luminance of the organic light emitting diode driven by the gamma data voltage may change in response to a change in the brightness control signal.

According to another feature of the present invention, the voltage value of the gamma point voltage changes to correspond to the rate of change of the data value of the brightness control signal, and the gamma reference voltage is the rate of change of the data value of the brightness control signal in the n-th band to which the brightness control signal belongs. It is the maximum gamma point voltage having the largest voltage value among gamma point voltages that change to correspond to , and the gamma selection voltage is a gamma point that changes to correspond to the rate of change of the data value of the brightness control signal in the n-1 th band adjacent to the n th band. It is characterized in that it is the maximum gamma point voltage having the largest voltage value among voltages.

According to another feature of the present invention, the brightness control unit is a step starting point such that the resistance string is divided by the number of steps between the resistance string to which the gamma reference voltage is applied, and the n-th band and the n-1th band. and a step selector for applying a gamma select voltage to the step start point, and a gamma point voltage output unit for selecting a gamma point voltage having a voltage value corresponding to the data value of the brightness control signal and outputting the gamma point voltage characterized in that

According to another feature of the present invention, the resistor string includes a plurality of resistors connected in series, and the step selector includes a plurality of input terminals receiving the gamma selection voltage and a plurality of voltage division nodes between the plurality of resistors, respectively. It is a demultiplexer (DeMUX) including an output terminal, and the gamma point voltage output part is a multiplexer (MUX) including a plurality of input terminals contacted to a plurality of nodes, respectively, and an output terminal outputting a gamma point voltage .

According to another feature of the present invention, the first gamma unit outputs a gamma reference voltage to which an nth optical compensation corresponding to the nth band is applied, and the second gamma unit outputs an n−1th optical compensation corresponding to the n−1th band. It is characterized in that the applied gamma selection voltage is output.

According to another feature of the present invention, the first gamma unit includes a first gamma resistor string to which a high reference voltage is applied at one end and a low reference voltage to the other end of the first gamma resistor string and the gamma for the reference gray level from the first gamma resistor string. and a gamma reference voltage selector that selects and outputs a reference voltage, wherein the second gamma unit is selected from a second gamma resistor string and a second gamma resistor string to which a high reference voltage is applied to one end and a low reference voltage is applied to the other end. and a gamma selection voltage selection unit for selecting and outputting a gamma selection voltage for a reference grayscale.

In order to solve the above problems, an organic light emitting diode display according to an exemplary embodiment includes a timing controller and a data driver. The timing controller generates a first gamma control signal and a second gamma control signal based on the brightness control signal. The data driver provides a gamma data voltage to the display panel so that an image displayed on the display panel has a brightness corresponding to the data value of the brightness control signal based on the first gamma control signal and the second gamma control signal. The voltage value of the gamma data voltage is increased in proportion to the rate of change of the data value of the brightness control signal or decreased in inverse proportion to the rate of change of the data value of the brightness control signal as the data value of the brightness control signal is increased. Since the organic light emitting diode display according to an embodiment of the present invention includes a data driver that outputs a gamma data voltage that is increased or decreased to correspond to a change rate of a data value of a brightness control signal, the brightness of the organic light emitting diode display can be adjusted to the brightness of the brightness control signal. It may become brighter or darker in response to a change, and the organic light emitting diode display may maintain constant color reproducibility regardless of the brightness.

According to another aspect of the present invention, the data driver controls the first gamma unit and the second gamma unit to output a plurality of gamma reference voltages respectively corresponding to a plurality of preset reference grayscales based on the first gamma unit control signal. A second gamma unit that outputs a plurality of gamma selection voltages respectively corresponding to a plurality of reference grayscales based on the signal, receives the plurality of gamma reference voltages and the plurality of gamma selection voltages, respectively, and receives the plurality of gamma reference voltages and the plurality of gamma selection voltages Receives a plurality of brightness control units and a plurality of gamma point voltages that select and output a plurality of gamma point voltages respectively corresponding to a plurality of reference grayscales based on the gamma selection voltage of and a gamma data voltage output unit for outputting a data voltage.

According to another feature of the present invention, the first brightness control unit among the plurality of brightness control units receives a first gamma reference voltage from among the plurality of gamma reference voltages and receives a first gamma selection voltage from among the plurality of gamma selection voltages; A first gamma point voltage having a voltage value between the voltage value of the first gamma reference voltage and the voltage value of the first gamma selection voltage is selected, and a second brightness control unit among the plurality of brightness control units is identical to the first brightness control unit. The second gamma point voltage is selected as a method, and the voltage value of the first gamma point voltage and the voltage value of the second gamma point voltage increase in proportion to the rate of change of the brightness control signal as the data value of the brightness control signal increases, or , characterized in that the brightness is reduced in inverse proportion to the control signal.

According to another feature of the present invention, the first gamma unit receives a plurality of reference grayscales from a first gamma resistor string to which a high reference voltage is applied at one end and a low reference voltage to the other end of the first gamma resistor string and the first gamma resistor string. and a plurality of gamma reference voltage selectors for selecting and outputting a plurality of corresponding gamma reference voltages, wherein the second gamma unit includes a second gamma unit to which a high reference voltage is applied to one end and a low reference voltage is applied to the other end of the second gamma unit. and a plurality of gamma selection voltage selectors for selecting and outputting a plurality of gamma selection voltages respectively corresponding to a plurality of reference grayscales from the resistance string and the second gamma resistance string.

According to another feature of the present invention, the plurality of gamma reference voltage selectors are cascaded to each other, and the plurality of gamma select voltage selectors are cascaded to each other.

According to another feature of the present invention, the lowest gamma reference voltage selector configured to select a gamma reference voltage corresponding to the lowest gray level from among a plurality of gamma reference voltage selectors of the first gamma unit is directly connected to the gamma data voltage output unit, The lowest gamma reference voltage selected by the gamma reference voltage selection unit is directly applied to the gamma data voltage output unit.

According to another feature of the present invention, each of the plurality of brightness control string units is 1:1 connected to the remaining gamma reference voltage selectors except for the lowest gamma reference voltage selector of the first gamma unit.

The details of other embodiments are included in the detailed description and drawings.

The present invention uses a gamma data voltage generating circuit that outputs a gamma data voltage that is increased or decreased to correspond to a change rate of a data value of a brightness control signal to smoothly brighten the screen of an organic light emitting diode display according to a user's brightness control command; It may be darkened, and color reproducibility of the organic light emitting diode display is constantly maintained regardless of the brightness of the screen.

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a block diagram illustrating an organic light emitting diode display according to an exemplary embodiment.
2 is a diagram for explaining an example in which a user's brightness control command is input to the organic light emitting display device according to an embodiment of the present invention.
3 is a block diagram illustrating a gamma data voltage generation circuit according to an embodiment of the present invention.
4 is a block diagram illustrating a first gamma unit included in a gamma data voltage generation circuit according to an embodiment of the present invention.
5 is a block diagram illustrating a second gamma unit included in a gamma data voltage generation circuit according to an embodiment of the present invention.
6 is a block diagram illustrating a first brightness control unit included in a gamma data voltage generation circuit according to an embodiment of the present invention.
7A and 7B are waveform diagrams of a gamma data voltage according to a brightness control signal for explaining an effect of a gamma data voltage generating circuit according to an embodiment of the present invention.
8A and 8B are graphs of color coordinates according to a brightness control signal for explaining an effect of a gamma data voltage generating circuit according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between the two parts unless 'directly' is used.

When a device or layer is referred to as 'on' another device or layer, it includes any other layer or layer interposed therebetween or directly on the other device.

Although first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

Like reference numerals refer to like elements throughout.

The size and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

In this specification, the 'data value of a specific signal' means a value that quantitatively indicates the magnitude of a specific signal in a digital format, and the voltage value or current value of an analog signal required to actually implement a specific signal in digital format. doesn't mean For example, in this specification, 'the data value of the brightness control signal is 383' means that the quantified value of the digital type brightness control signal is 383. Also, in the present specification, the 'voltage value of a specific voltage' means a value quantitatively indicating the magnitude of the corresponding voltage in an analog format. For example, in this specification, 'the voltage value of the gamma data voltage is 2V' means that the potential difference of the output gamma data voltage from the ground GND is 2V.

Also, in this specification, the term "resolution" means the number of steps or steps that a data value of a specific signal or a voltage value of a specific voltage can have in a specific section. For example, if the data value of the brightness control signal between the first band and the second band can have 4 steps, the resolution of the brightness control signal between the first band and the second band is 4. In addition, if the gamma data voltage between the first band and the second band can be output as voltages of four stages, the resolution of the gamma data voltage between the first band and the second band is 4.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating an organic light emitting diode display according to an exemplary embodiment. 2 is a diagram for explaining an example in which a user's brightness control command is input to the organic light emitting display device according to an embodiment of the present invention. Referring to FIG. 1 , an organic light emitting diode display according to an exemplary embodiment includes a display panel PN including a plurality of pixels PX, a gate driver GIC, a data driver DIC, and a timing controller TC. ) and system (SYS).

The display panel PN includes an active area (ie, a display area) and an inactive area (ie, a non-display area), and the plurality of pixels PX are arranged in a matrix in the display area. Each of the pixels PX receives various signals from the data driver DIC and the gate driver GIC. For example, each pixel PX receives various signals through a data line DL connected to the data driver DIC and a gate line GL connected to the gate driver GIC, as shown in FIG. 1 . .

The pixels PX display a specific color based on the received signals. For example, the pixels PX may be composed of sub-pixels displaying red, green, blue, and/or white, and colors displayed by the sub-pixels are mixed, so that the pixel PX has various colors. can be displayed. Each sub-pixel displays a specific color with various grayscales and brightnesses. For example, the red sub-pixel may display red as 0 to 255 gradations, the green sub-pixel may display green as 0 to 255 gradations, and the blue sub-pixel may display blue as 0 to 255 gradations. can be displayed However, the gray level of each sub-pixel is not limited to 0 to 255, and each sub-pixel may have a gray level of 255 or more. Hereinafter, for convenience of description, the organic light emitting diode display 1000 including sub-pixels having grayscales of 0 to 255 will be described. The grayscale and luminance of each sub-pixel may be determined by a gamma data voltage provided through the data line DL. Even for two sub-pixels having the same gray level, when the brightness of each sub-pixel is different from each other, each sub-pixel may be driven with different gamma data voltages.

The system SYS may be configured to supply a vertical synchronization signal, a horizontal synchronization signal, a clock signal and image data through a transmitter of the graphics controller to suitable circuits. For example, the system SYS provides a clock signal, a vertical/horizontal synchronization signal Sync, and image data to the timing controller TC.

In addition, the system SYS generates the brightness control signal DBS in digital format based on the user's brightness control command. The user's brightness control command may be input in various ways. Referring to FIG. 2 , when the organic light emitting diode display is applied to the smart phone 2000 , the user executes the brightness control mode of the smart phone 2000 , and touches and drags the screen of the smart phone 2000 . The brightness of the organic light emitting diode display may be adjusted by dragging or flicking. In this case, the brightness of the organic light emitting diode display may be variously changed according to the degree of the user's touch, drag, or flicking. Referring to FIG. 1 , in order to variously change the brightness of the organic light emitting diode display 1000 , the brightness control signal DBS has various data values. For example, the brightness control signal DBS has data values of 0 to 1023. The data value of the brightness control signal DBS may correspond to the brightness of the display panel PN. For example, the 0 data value of the brightness control signal DBS may correspond to the darkest brightness of the display panel PN, and the 1023 data value of the brightness control signal DBS is the brightest brightness of the display panel PN. can correspond to However, the present invention is not limited thereto, and as the data value of the brightness control signal DBS increases, the brightness of the display panel PN may be set to become darker. In this case, the 1023 data value of the brightness control signal DBS is the display panel It may correspond to the darkest brightness of PN, and the 0 data value of the brightness control signal DBS may correspond to the brightest brightness of the display panel PN.

The brightness control signal DBS is divided into a preset band according to the data value. A band may be defined as a set of brightness control signals to which the same optical compensation is applied. In general, the data value of the image data and the voltage value of the gamma data voltage generated by the data driver (DIC) are not linear, so that the original image included in the image data and the display panel (PN) according to the brightness of the screen The displayed images displayed on the . have different colors or contrast ratios. Optical compensation is performed to compensate for these differences. The optical compensation compensates the gamma data voltage so that the contrast ratio and color of the display image displayed on the display panel PN match the contrast ratio and color of the original image. Since optical compensation cannot be performed on all the brightness control signals, the brightness control signals are grouped according to data values and the same optical compensation is applied to the corresponding group. A band means a group of brightness control signals to which the same optical compensation is applied.

The configuration of the band may be made in various ways. For example, brightness control signals having data values of 0 to 127 are in the first band, brightness control signals having data values of 128 to 255 are in the second band, and brightness control signals having data values of 256 to 383 are in the third band. , the brightness control signals having data values of 384 to 511 are in the 4th band, the brightness control signals having data values of 512 to 659 are in the 5th band, and the brightness control signals having data values of 660 to 767 are in the 6th band, Brightness control signals having data values of 768 to 895 may be configured as a seventh band, and brightness control signals having data values of 896 to 1023 may be configured as an eighth band. However, the present invention is not limited thereto, and the band may be configured in such a way that data values of the brightness control signals decrease as the band increases. For convenience of explanation, the following description will be made based on a band configured in such a way that the data value of the brightness control signal increases as the band increases. That is, the second band corresponds to a brightness brighter than that of the first band. Meanwhile, the number of brightness control signals included in each band may be different from each other, and may be defined in various ways according to the type and use of the organic light emitting diode display.

The timing controller TC receives a horizontal/vertical synchronization signal Sync, a clock signal, and image data from the system SYS. The vertical synchronization signal indicates the time required to display an image of one frame. The horizontal synchronization signal indicates the time required to display one horizontal line of the image, that is, one pixel line. Accordingly, the horizontal synchronization signal includes the same number of pulses as the number of pixels PX included in one pixel line.

The timing controller TC provides a scan control signal (SCS) to the gate driver GIC and provides a data control signal (DCS) to the data driver DIC.

The scan control signal SCS applied to the gate driver GIC may include a gate start pulse signal, a gate shift clock signal, a gate output enable signal, and the like. have. The gate start pulse signal is a signal for timing control of the first gate signal of the gate driver GIC, the gate shift clock signal is a signal for outputting and sequentially shifting the gate start pulse signal, and the gate output enable signal is the gate It is a signal for controlling the output timing of the driving unit GIC.

The timing controller TC rearranges the image data so that the image data received from the system SYS can be provided to the data driver DIC. For example, the timing controller TC may supply digital data corresponding to text, graphics, video, or other images to be displayed on the display panel PN to the data driver DIC. The data driver DIC applies a gamma data voltage to each data line DL based on the data received from the timing controller TC.

The data control signal DCS provided to the data driver DIC may include a source sampling clock signal, a source output enable signal, a source start pulse signal, and the like. The source sampling clock signal determines a driving frequency of the data driver DIC and is used as a sampling clock for latching image data by the data driver DIC. The source output enable signal is used to transmit image data latched by the source sampling clock signal to appropriate pixels. The source start pulse signal is a signal instructing the start of sampling or latching of image data during one horizontal period.

The timing controller TC generates a first gamma control signal GCS1 and a second gamma control signal GCS2 in digital format based on the brightness control signal DBS received from the system SYS. The first gamma unit control signal GCS1 includes first gamma data. The first gamma data means optical compensation data for compensating the gamma data voltage in the n-th band to which the brightness control signal DBS belongs. For convenience of description, an optical compensation applied to the n-th band is defined as an n-th optical compensation. However, here and there n means an integer greater than or equal to 1. The second gamma unit control signal GCS2 includes second gamma data. The second gamma data are n-1 th optical compensation data for compensating for a gamma data voltage in an n-1 th band adjacent to the n th band. The above-described first gamma data and second gamma data may be stored in a memory provided in the timing controller TC, and the above-described memory may be a nonvolatile memory, for example, an EEPROM (Electrically Erasable Programmable Read Only Memory) and/or or EDID ROM (Extended Display Identification Data ROM).

The timing controller TC determines the n-th band to which the brightness control signal belongs based on the brightness control command received from the system SYS, and includes first gamma data for n-th optical compensation applied to the n-th band and the n-th band. A first gamma control signal GCS1 and a second gamma control signal GCS2 are generated by reading the second gamma data for the n-1 th optical compensation applied to the -1 band from the memory. The generated first gamma control signal GCS1 and the second gamma control signal GCS2 are transferred to the gamma data voltage generation circuit GC of the data driver DIC, and the gamma data voltage generation circuit GC A gamma data voltage is generated based on the first gamma control signal GCS1 and the second gamma control signal GCS2 .

The gate driver GIC receives the scan control signal SCS from the timing controller TC and applies a gate voltage to the gate line GL. The switching thin film transistor included in the pixels PX may be turned on based on the gate voltage.

The data driver DIC receives the data control signal DCS from the timing controller TC and applies a gamma data voltage to the data line DL. The driving thin film transistor included in the pixels PX is turned on based on the gamma data voltage, and the sub-pixel may be turned on by transferring the driving current to the organic light emitting diode.

The data driver DIC includes a gamma data voltage generation circuit GC that generates a gamma data voltage based on the first gamma control signal GCS1 and the second gamma control signal GCS2 and amplifies the generated gamma data voltage. and an output unit SO for applying it to each data line DL. The gamma data voltage generating circuit GC generates a gamma data voltage that increases or decreases in response to a change rate of a data value of the brightness control signal DBS. For example, as the data value of the brightness control signal DBS increases, the voltage value of the gamma data voltage increases as the data value of the brightness control signal DBS changes or decreases as the data value of the brightness control signal DBS changes. do. In this case, the display panel PN may become brighter or darker in response to a change rate of the data value of the brightness control signal DBS. In order to describe this in more detail, reference is also made to FIG. 3 .

3 is a block diagram illustrating a gamma data voltage generation circuit according to an embodiment of the present invention. Referring to FIG. 3 , the gamma data voltage generating circuit GC includes a first gamma unit 100 , a second gamma unit 200 , a brightness control unit 300 , and a gamma data voltage output unit 400 .

The first gamma unit 100 generates a plurality of gamma reference voltages based on the first gamma unit control signal GCS1 . Each of the plurality of gamma reference voltages corresponds to a preset reference grayscale. The reference grayscale may be set as a specific grayscale among various grayscales that can be expressed in the organic light emitting diode display. For example, the first reference gradation may be set to 255 gradations, the second reference gradation may be set to 191 gradations, the third reference gradation may be set to 127 gradations, the fourth reference gradation may be set to 63 gradations, and the fifth reference gradation may be set to 31 gradations. As the grayscale, the sixth reference grayscale may be set as 15 grayscales, the seventh reference grayscale may be set as 1 grayscale, and the eighth reference grayscale may be set as 0 grayscales. However, each reference grayscale is not limited thereto, and 10 or more reference grayscales may be set. For convenience of explanation, the following description is based on a case in which 8 reference grayscales are set.

In order for a pixel of the organic light emitting diode display to emit light with a reference grayscale, a specific gamma data voltage is required. The voltage value of the gamma point voltage varies according to the data value of the brightness control signal. That is, even with the same gray level, the required gamma data voltage may be different according to the luminance of the pixel. Accordingly, the voltage value of the gamma point voltage may change according to the change of the brightness control signal in the n-th band to which the brightness control signal belongs. The gamma reference voltage refers to the maximum gamma point voltage having the largest voltage value among gamma point voltages that change according to the data value of the brightness control signal in the n-th band to which the brightness control signal belongs. For example, assuming that the data value of the brightness control signal is 500 and it belongs to the fourth band, the first gamma reference voltage GRV1 is the maximum first gamma point voltage for the first reference grayscale in the fourth band. it means. If the maximum data value of the brightness control signal in the fourth band is 511 and the data value of the brightness control signal is 511, the gamma data voltage for the first reference gray level output through the gamma data voltage output unit 400 is If the maximum is 2.1V, the first gamma reference voltage GRV1 may be 2.1V. If the first gamma point voltage is the gamma data voltage for the 255 gray scale, the first gamma reference voltage GRV1 is the maximum voltage that the gamma data voltage for the 255 gray scale in the fourth band can have (ie, 2.1 V). ) means Similarly, the second gamma reference voltage GRV2 means a voltage that the gamma data voltage with respect to the second reference grayscale can have the maximum in the fourth band, and the sixth gamma reference voltage GRV6 corresponds to the sixth reference grayscale. It means a voltage that the gamma data voltage can have the maximum in the fourth band.

As shown in FIG. 3 , the first gamma reference voltage GRV1 to the sixth gamma reference voltage GRV6 generated by the first gamma unit 100 are applied to the first brightness control unit 310 to the sixth brightness control unit. 360 , respectively, and the seventh gamma reference voltage GRV7 and the eighth gamma reference voltage GRV8 are directly provided to the gamma data voltage output unit 400 . However, the present invention is not limited thereto, and the seventh gamma reference voltage GRV7 and the eighth gamma reference voltage GRV8 generated by the first gamma unit 100 are provided to the seventh brightness control unit and the eighth brightness control unit, respectively. can be

The second gamma unit 200 generates a plurality of gamma selection voltages based on the second gamma unit control signal GCS2 . Each of the gamma selection voltages corresponds to a plurality of preset reference grayscales. The gamma selection voltage refers to the maximum gamma point voltage having the largest voltage value among gamma point voltages that change according to the data value of the brightness control signal in the n-th band adjacent to the n-th band to which the brightness control signal belongs. For example, assuming that the brightness control signal belongs to the fourth band, the first gamma selection voltage GSV1 may have the maximum gamma data voltage for the first reference grayscale in the third band adjacent to the fourth band. means the voltage. That is, when the maximum data value that the brightness control signal can have in the third band is 383 and the data value of the brightness control signal is 383, the first reference grayscale output through the gamma data voltage output unit 400 is If the gamma data voltage for the gamma data voltage is 2V, the first gamma selection voltage GSV1 may be 2V. If the first gamma point voltage corresponds to the 255 gray scale, the first gamma selection voltage GSV1 means the maximum voltage that the gamma data voltage for the 255 gray scale in the third band can have. Similarly, the second gamma selection voltage GSV2 means a maximum voltage that the gamma data voltage with respect to the second reference grayscale can have a maximum in the third band, and the sixth gamma selection voltage GSV6 corresponds to the sixth reference grayscale. It means the maximum voltage that the gamma data voltage can have the maximum in the third band.

The first gamma selection voltage GSV1 to the sixth gamma selection voltage GSV6 generated by the second gamma unit 200 are provided to the first brightness control unit 310 to the sixth brightness control unit 360 , respectively.

The brightness control unit 300 includes the first gamma reference voltage GRV1 to the sixth gamma reference voltage GRV6 received from the first gamma unit 100 and the first gamma selection voltage received from the second gamma unit 200 . The first gamma point voltages GPV1 to the sixth gamma point voltages GPV6 are generated from the (GSV1) to the sixth gamma selection voltages GSV1. Specifically, the brightness control unit 300 includes a first brightness control unit 310 and a second brightness control unit 320 to a sixth brightness control unit 360 that receive each of the gamma reference voltage and the gamma selection voltage. do. The first brightness controller 310 selects the first gamma point voltage GPV1 having a voltage value between the voltage value of the first gamma reference voltage GRV1 and the voltage value of the first gamma selection voltage GSV1 . Similarly, the second brightness control unit 320 selects the second gamma point voltage GPV2 having a voltage value between the voltage value of the second gamma reference voltage GRV2 and the voltage value of the second gamma selection voltage GSV2 . and the sixth brightness control unit 360 selects the sixth gamma point voltage GPV6 having a voltage value between the voltage value of the sixth gamma reference voltage GRV6 and the voltage value of the sixth gamma selection voltage GSV6 do.

The gamma data voltage output unit 400 divides a plurality of gamma point voltages respectively corresponding to preset reference grayscales to output the gamma data voltage GDV. For example, the gamma data voltage output unit 400 may output a gamma data voltage GDV for displaying a gray level between the first reference gray level and the second reference gray level, and the gamma data voltage GDV is the first reference gray level. It may be selected between the first gamma point voltage GPV1 for the reference grayscale and the second gamma point voltage GPV2 for the second reference grayscale. The display panel may be driven based on the gamma data voltage GDV, and the grayscale and brightness of each pixel of the display panel may be determined according to the voltage value of the gamma data voltage GDV.

As described above, since the brightness of the display panel that is changed according to the brightness control signal is the overall brightness of the display panel, the overall brightness may be adjusted by decreasing or increasing the voltage value of the gamma data voltage GDV as a whole. For example, in order to increase the brightness of the display panel, the overall voltage value of the gamma point voltage corresponding to each reference grayscale may be increased. However, according to this driving method, the overall brightness of the display panel may be discontinuously changed in some sections, and the color of the display panel may be non-uniformly changed. This is because the efficiency of the organic light emitting diode is different for each gray level. Specifically, a gamma data voltage having a high voltage value is required to make the organic light emitting diode emit light with high luminance. However, the voltage values of the gamma data voltages for emitting light with a specific luminance according to the gray level may be different from each other. For example, if the voltage value of the gamma data voltage required for emitting a 255-gradation red organic light-emitting device with a luminance of 15 nits is 2.02V, the gamma data voltage required for emitting a red organic light-emitting device with a 63-gradation with a luminance of 15 nits The voltage value of may be higher than 2.02V. That is, the efficiency of the organic light emitting diode decreases toward a lower gray scale. As described above, when the overall voltage value of the gamma point voltage is reduced or increased, the voltage value of the gamma point voltage is equally reduced or increased for all grayscales, and the voltage values of the gamma data voltage are all the same. decreased or increased. However, the brightness of pixels for each gray level seen in the actual display panel may be different from each other in the pixels of the high gray level and the pixels of the low gray level. That is, since the voltage value of the gamma data voltage to be changed to increase the luminance of the organic light emitting diode is different for each grayscale, the luminance of the high grayscale pixel and the low grayscale pixel are different from each other. For example, the voltage value of the gamma data voltage that needs to be increased in order to increase a 255-gradation red organic light emitting diode from 15 nits to 20 nits and a 63-gray red organic light emitting diode from 15 nits to 20 nits. The voltage values of the gamma data voltages to be increased may be different from each other. Accordingly, when all of the gamma data voltages are increased by the same voltage value, the luminance increased in the 255 gray level red organic light emitting diode and the 63 gray level red organic light emitting diode are different from each other. Accordingly, the overall brightness of the display panel may be discontinuously increased, and the overall color of the display panel may be non-uniformly changed.

In particular, as the optical compensation applied between the n-th band and the n-1 band adjacent to each other is different from each other, the data value of the brightness control signal increases but the voltage value of the corresponding gamma data voltage decreases. This can happen. In this case, a phenomenon in which the overall luminance of the display panel is rather reduced to oppose the user's brightness control command may occur.

However, the organic light emitting diode display according to an embodiment of the present invention includes a brightness control unit 300 connected to the first gamma unit 100 and the second gamma unit 200, respectively, and the brightness control unit 300 includes A gamma point voltage selected between an n-th band and an n-1 th band adjacent to each other so as to continuously increase the luminance of the pixel and having the same resolution as the resolution of the brightness control signal is applied to each of the gamma points. Accordingly, the gamma data voltage output from the gamma data voltage output unit 400 may have a voltage value that continuously changes so that the luminance of the pixel for each gray level is continuously increased or decreased. In order to describe this in more detail, each component of the gamma data voltage generating circuit will be described in detail with reference to FIGS. 4 to 7 together.

4 is a block diagram illustrating a first gamma unit included in a gamma data voltage generation circuit according to an embodiment of the present invention. Referring to FIG. 4 , the first gamma unit 100 includes a first gamma resistor string 180 and a first gamma reference voltage selector 110 to a seventh gamma reference voltage selector 170 .

The first gamma resistor string 180 includes a plurality of resistors connected in series and a plurality of voltage division nodes disposed between the resistors. If the first gamma data included in the first gamma unit control signal GCS1 is 8 bits, the first gamma resistor string 180 has ²⁸ dividing nodes. A voltage applied to the voltage dividing nodes is determined by a high reference voltage HRV and a low reference voltage LRV across both ends of the first gamma resistor string 180 . The high reference voltage HRV may be a high potential voltage (ie, Vdd voltage) input to the organic light emitting device, and the low reference voltage LRV may be a low potential voltage (ie, Vss voltage) input to the organic light emitting device or ground. (GND). The first gamma reference voltage GRV1 to the eighth gamma reference voltage GRV8 output from the first gamma unit 100 may be determined between the high reference voltage HRV and the low reference voltage LRV. As described above, the first gamma reference voltage GRV1 to the eighth gamma reference voltage GRV8 mean the maximum gamma data voltage corresponding to the first reference grayscale to the eighth reference grayscale in the n-th band.

The first gamma reference voltage selector 110 is configured to select the first gamma reference voltage GRV1 between the high reference voltage HRV and the voltage of the first dividing node of the first gamma resistor string 180 . For example, the first gamma reference voltage selector 110 selects the first gamma reference voltage GRV1 for 255 gray scales. The first gamma reference voltage GRV1 has a voltage value between a voltage value of the high reference voltage HRV and a voltage value of the voltage of the first dividing node.

The first gamma reference voltage selector 110 includes a multiplexer (MUX) 111 and a buffer 112 . The multiplexer 111 selects one voltage divider node from among voltage divider nodes disposed between one end of the first gamma resistance string 180 to which the high reference voltage HRV is applied and the first voltage divider node, and outputs the voltage of the corresponding node. do. The voltage of the first dividing node may be the lowest voltage that the first gamma reference voltage GRV1 can have. The multiplexer 111 selects a specific voltage dividing node based on the first gamma control signal GCS1. For example, based on the first gamma data included in the first gamma control signal GCS1 , the multiplexer 111 sets the maximum gamma data voltage for the first reference grayscale in the nth band to the first gamma reference voltage ( GRV1) can be selected. The buffer 112 prevents the current of the output terminal of the buffer 112 from flowing into the multiplexer 111 and stably maintains the first gamma reference voltage GRV1 output from the multiplexer 111 .

The seventh gamma reference voltage selector 170 is configured to select the seventh gamma reference voltage GRV7 between the low reference voltage LRV and the voltage of the sixth voltage dividing node of the first gamma resistor string 180 . For example, the seventh gamma reference voltage selector 170 selects the seventh gamma reference voltage GRV7 with respect to the seventh reference grayscale (eg, one grayscale). The seventh gamma reference voltage selector 170 includes a multiplexer 171 and a buffer 172 . The multiplexer 171 selects one voltage divider node from among voltage divider nodes disposed between the other end of the first gamma resistance string 180 to which the low reference voltage LRV is applied and the sixth voltage divider node, and outputs the voltage of the corresponding node. do. The voltage of the sixth dividing node may be the maximum voltage that the seventh gamma reference voltage GRV7 can have. The configuration and connection relationship of the multiplexer 171 and the buffer 172 of the seventh gamma reference voltage selector 170 are substantially the same as those of the multiplexer 111 and the buffer 112 of the first gamma reference voltage selector 110 . Therefore, redundant description is omitted.

The second gamma reference voltage selector 120 is cascaded to the first gamma reference voltage selector 110 . That is, the first gamma reference voltage GRV1 output from the first gamma reference voltage selector 110 is applied to the input terminal of the second gamma reference voltage selector 120 . The second gamma reference voltage selector 120 selects and outputs the second gamma reference voltage GRV2 between the first gamma reference voltage GRV1 and the seventh gamma reference voltage GRV7 . The second gamma reference voltage selector 120 includes a resistor string 123 , a multiplexer 121 , and a buffer 122 .

The first gamma reference voltage GRV1 output from the first gamma reference voltage selector 110 is applied to one end of the resistor string 123 of the second gamma reference voltage selector 120 , and the resistance string 123 is applied. The seventh gamma reference voltage GRV7 output from the seventh gamma reference voltage selector 170 is applied to the other end of the . The resistor string 123 of the second gamma reference voltage selector 120 includes a plurality of resistors connected in series and a plurality of voltage division nodes disposed between the resistors. The number of division nodes of the resistor string 123 is less than the number of division nodes of the first gamma resistance string 180 . For example, the resistance string 123 includes a number of division nodes corresponding to the number of division nodes disposed between the first division node and the seventh division node of the first gamma resistance string 180 .

The multiplexer 121 and the buffer 122 of the second gamma reference voltage selector 120 are substantially the same as the multiplexer 111 and the buffer 112 of the first gamma reference voltage selector 110, and thus overlap A description is omitted.

Like the second gamma reference voltage selector 120 , the third gamma reference voltage selector 130 , the fourth gamma reference voltage selector 140 , the fifth gamma reference voltage selector 150 , and the sixth gamma reference The voltage selectors 160 are cascaded to each other, respectively, a third gamma reference voltage GRV3 , a fourth gamma reference voltage GRV4 , a fifth gamma reference voltage GRV5 , and a sixth gamma reference voltage GRV6 , respectively. Select to print. The third gamma reference voltage selector 130 , the fourth gamma reference voltage selector 140 , the fifth gamma reference voltage selector 150 , and the sixth gamma reference voltage selector 160 select the second gamma reference voltage Since it is substantially the same as the unit 120, a redundant description thereof will be omitted.

Although the first gamma unit 100 shown in FIG. 4 includes the first gamma reference voltage selector 110 to the sixth gamma reference voltage selector 160 cascaded to each other, in some embodiments, The first gamma reference voltage selector 110 to the sixth gamma reference voltage selector 160 of the first gamma unit 100 may not be cascaded. For example, the first gamma reference voltage selector 110 to the sixth gamma reference voltage selector 160 may be directly connected to the first gamma resistor string 180 . That is, the first gamma reference voltage selector 110 is connected between one end of the first gamma resistor string 180 and the first voltage dividing node, and the second gamma reference voltage selector 120 is connected to the first gamma resistor string ( 180 is connected between the first voltage dividing node and the second voltage dividing node, and the third gamma reference voltage selector 130 is connected between the second voltage dividing node and the third voltage dividing node of the first gamma resistor string 180 , , the fourth gamma reference voltage selector 140 is connected between the third voltage divider node and the fourth voltage divider node of the first gamma resistor string 180 , and the fifth gamma reference voltage selector 150 has the first gamma resistor It is connected between the fourth voltage dividing node and the fifth voltage dividing node of the string 180 , and the sixth gamma reference voltage selector 160 is connected between the fifth voltage dividing node and the sixth voltage dividing node of the first gamma resistor string 180 . can be connected

As shown in FIG. 4 , the eighth gamma reference voltage GRV8 is the same voltage as the low reference voltage LRV. That is, the eighth reference grayscale may be set to zero grayscale, and the eighth gamma reference voltage GRV8 may be generated by directly outputting the low reference voltage LRV without passing through a separate gamma reference voltage selector. In this case, the eighth gamma reference voltage GRV8 may be directly applied to the gamma data voltage output unit.

In addition, as described above, the seventh gamma reference voltage GRV7 means a gamma reference voltage for the seventh reference grayscale (ie, one grayscale), and the first gamma reference voltage GRV1 to the seventh gamma reference voltage ( It is the gamma reference voltage for the lowest gray level in GRV1). That is, the seventh gamma reference voltage selector 170 selects the gamma reference voltage for the lowest gray level. For convenience of explanation, the seventh gamma reference voltage selector 170 is defined as the lowest gamma reference voltage selector, and the seventh gamma reference voltage GRV7 output from the seventh gamma reference voltage selector 170 is the gamma data voltage. It can be applied directly to the output.

5 is a block diagram illustrating a second gamma unit included in a gamma data voltage generation circuit according to an embodiment of the present invention. The second gamma unit 200 shown in FIG. 5 is compared to the first gamma unit 100 shown in FIG. 4 , except that the first gamma unit 200 shown in FIG. 4 includes six gamma selection voltage selectors. 100), and thus a redundant description thereof will be omitted. Referring to FIG. 5 , the second gamma unit 200 includes a second gamma resistor string 280 and a first gamma selection voltage selection unit 210 to a sixth gamma selection voltage selection unit 260 .

The second gamma resistor string 280 includes a plurality of resistors connected in series and a plurality of voltage division nodes disposed between the resistors. A high reference voltage HRV is applied to one end of the second gamma resistor string 280 , and a low reference voltage LRV is applied to the other end of the second gamma resistor string 280 . The first gamma selection voltage GSV1 to the sixth gamma selection voltage GSV6 are selected between the high reference voltage HRV and the low reference voltage LRV. As described above, the first gamma selection voltage GSV1 to the sixth gamma selection voltage GSV6 mean the maximum gamma data voltage for the first reference grayscale to the sixth reference grayscale in the n-1 th band. Since the second gamma resistor string 280 is substantially the same as the first gamma resistor string 200 , a redundant description thereof will be omitted.

The first gamma selection voltage selector 210 is configured to select the first gamma selection voltage GSV1 between the high reference voltage HRV and the voltage of the first dividing node of the second gamma resistor string 280 . For example, the first gamma selection voltage selection unit 210 selects the first gamma selection voltage GSV1 for 255 grayscales based on the second gamma control signal GCS2 . The first gamma selection voltage selector 210 includes a multiplexer and a buffer, and the first gamma selection voltage selector 210 is substantially the same as the first gamma reference voltage selector of the first gamma unit, so a redundant description will be omitted. do.

The second gamma selection voltage selection unit 220 , the third gamma selection voltage selection unit 230 , the fourth gamma selection voltage selection unit 240 , the fifth gamma selection voltage selection unit 250 , and the sixth gamma selection voltage selection unit The unit 260 is cascade-connected, and includes a second gamma selection voltage GSV2 , a third gamma selection voltage GSV3 , a fourth gamma selection voltage GSV4 , a fifth gamma selection voltage GSV5 , and a sixth gamma selection voltage GSV5 , respectively. The gamma selection voltage GSV6 is selected and output. The second gamma selection voltage selection unit 220 , the third gamma selection voltage selection unit 230 , the fourth gamma selection voltage selection unit 240 , the fifth gamma selection voltage selection unit 250 , and the sixth gamma selection voltage selection unit Since the unit 260 is substantially the same as the second gamma reference voltage selector to the sixth gamma reference voltage selector of the first gamma unit, a redundant description thereof will be omitted.

In some embodiments, the first gamma selection voltage selection unit 210 to the sixth gamma selection voltage selection unit 260 may not be cascaded, and the first gamma selection voltage selection unit 210 to the sixth gamma selection voltage selection unit 210 . The selection voltage selection unit 260 may be directly connected to the second gamma resistance string 280 .

6 is a block diagram illustrating a first brightness control unit included in a gamma data voltage generation circuit according to an embodiment of the present invention. Although the second brightness control unit to the sixth brightness control unit are not illustrated in FIG. 6 , the second brightness control unit to the sixth brightness control unit are the same as the first brightness control unit 310 , so hereinafter, the first brightness control unit is the same as the first brightness control unit 310 . It will be described with reference to the part 310 . Referring to FIG. 6 , the first brightness control unit 310 includes a step selector 311 , a resistor string 312 , and a gamma point voltage output unit 313 .

The resistor string 312 of the first brightness control unit 310 includes a plurality of resistors connected in series and a plurality of voltage division nodes disposed between the resistors. The first brightness control unit 310 includes the same number of voltage division nodes as the first gamma resistor string of the first gamma unit. For example, resistor string 312 has 2 ⁸ voltage dividing nodes. The first gamma reference voltage GRV1 is applied to one end of the resistor string 312 of the first brightness control unit 310 , and the low reference voltage LRV is applied to the other end.

The step selector 311 of the first brightness control unit 310 selects a voltage dividing node to which the first gamma selection voltage GSV1 is to be applied based on the brightness control unit control signal RCS. For example, if there are four data values of the brightness control signal that may exist between the n-th band and the n-1 th band, the number of steps between the n-th band and the n-1 th band is four. That is, the resolution of the brightness control signal between the n-th band and the n-1 th band is 4. In this case, the step selector 311 may apply the first gamma selection voltage GSV1 to a fourth voltage dividing node from one end of the resistor string 312 to which the first gamma reference voltage GRV1 is applied. For convenience of description, a dividing node selected by the step selector 311 is defined as a step starting point SSP. Accordingly, four steps are determined between the first gamma reference voltage GRV1 and the first gamma selection voltage GSV1, and the resolution of the first gamma point voltage GPV1 between the n-th band and the n-1 th band is It may be determined to be 4 in the same way as the resolution of the brightness control signal.

The step selection unit 311 of the first brightness control unit 310 is a demultiplexer including a plurality of output terminals connected to a plurality of voltage division nodes of the resistor string 312 and an input terminal for receiving the first gamma selection voltage GSV1 . (Demultiplexer: DeMUX) may be configured. The step selector 311 outputs the first gamma selection voltage GSV1 to one of the plurality of output terminals based on the brightness controller control signal RCS.

The gamma point voltage output unit 313 of the first brightness control unit 310 selects and outputs the first gamma point voltage GPV1 between the first gamma reference voltage GRV1 and the first gamma selection voltage GSV1 . . The first gamma point voltage GPV1 has a voltage value between the voltage value of the first gamma reference voltage GRV1 and the voltage value of the first gamma selection voltage GSV1 . The gamma point voltage output unit 313 selects the first gamma point voltage GPV1 corresponding to the data value of the brightness control signal based on the brightness control signal RCS. As described above, since the first gamma point voltage GPV1 has the same resolution as the brightness control signal between the n-th band and the n-1 band, the voltage value of the first gamma point voltage GPV1 and the brightness control signal The data value of may correspond to 1:1. Accordingly, when the data value of the brightness control signal is changed, the voltage value of the first gamma point voltage GPV1 may also be changed to correspond to the rate of change of the data value of the brightness control signal. That is, the voltage value of the first gamma point voltage GPV1 may be increased or decreased in proportion to the rate of change of the data value of the brightness control signal as the data value of the brightness control signal is increased. In particular, even if the optical compensation applied to each band is changed between the n-th band and the n-1 band, the first gamma point voltage GPV1 has the same resolution as the brightness control signal, so that the first gamma point voltage GPV1 may be flexibly changed according to the brightness control signal. The gamma point voltage output unit 313 may be configured as a multiplexer including a plurality of input terminals connected to a plurality of voltage division nodes of the resistor string 312 and an output terminal outputting the first gamma point voltage GPV1 .

In some embodiments, the first brightness control unit 310 may further include a buffer connected to an output terminal of the gamma point voltage output unit 313 . The buffer prevents the current output from the gamma point voltage output unit 313 from flowing into the gamma point voltage output unit 313 and receives the first gamma point voltage GPV1 output from the gamma point voltage output unit 313 . keeps it stable.

The first gamma point voltages GPV1 to the sixth gamma point voltages respectively output from the first brightness control unit 310 to the sixth brightness control unit are applied to the gamma data voltage output unit. As described above, the first gamma point voltage GPV1 corresponds to 255 gray levels, the second gamma point voltage corresponds to 191 gray levels, the third gamma point voltage corresponds to 127 gray levels, and the fourth gamma point voltage is Corresponds to 63 gradations, the fifth gamma point voltage corresponds to 31 gradations, and the sixth gamma point voltage corresponds to 15 gradations. Each of the first gamma point voltages GPV1 to the sixth gamma point voltage has the same resolution as the brightness control signal, and each voltage value of the first gamma point voltage GPV1 to the sixth gamma point voltage is the data value of the brightness control signal. It may be increased or decreased in proportion to the rate of change of the data value of the brightness control signal by the increased amount.

Meanwhile, the seventh gamma reference voltage output from the seventh gamma reference voltage selector of the first gamma unit may be applied as the seventh gamma point voltage, and the low reference voltage may be applied as the eighth gamma point voltage. The seventh gamma point voltage and the eighth gamma point voltage correspond to grayscale 1 and grayscale 0, respectively. In the case of grayscale 1 and grayscale 0, the change in the voltage value of the gamma data voltage according to the data value of the brightness control signal is not large, so even without a separate brightness control unit, the change in luminance between grayscale 1 and 0 is easily noticeable to the human eye. may not be recognized. Accordingly, the seventh gamma point voltage and the eighth gamma point voltage may be directly provided from the first gamma unit without going through a separate brightness control unit, and the number of the brightness control units may be reduced by two.

The gamma data voltage output unit may include a resistance string and a multiplexer, and the resistance string of the gamma data voltage output unit includes the same number of resistors and voltage dividing nodes as the first gamma resistance string of the first gamma unit. Also, the multiplexer of the gamma data voltage output unit may divide the plurality of gamma point voltages to output the gamma data voltage, and the gamma data voltage output from the multiplexer may be provided to each data line through the output unit.

Since the organic light emitting diode display according to an embodiment of the present invention includes a brightness control unit that outputs a gamma point voltage having the same resolution as the data value of the brightness control signal, gamma data that changes to correspond to the rate of change of the data value of the brightness control signal A voltage may be provided to the display panel. Accordingly, the overall brightness of the display panel may be brightened or darkened in proportion to a change in the data value of the brightness control signal, and even if the data value of the brightness control signal is changed, color reproducibility of the display panel may be maintained constant. 7A to 8B will be referred to together to describe an improved effect of the organic light emitting diode display according to an exemplary embodiment.

7A and 7B are waveform diagrams of a gamma data voltage according to a brightness control signal for explaining an effect of a gamma data voltage generating circuit according to an embodiment of the present invention. Specifically, FIG. 7A is a graph illustrating a change in a gamma data voltage according to a data value of a brightness control signal in an organic light emitting diode display according to a comparative example, and FIG. 7B is a graph illustrating brightness in the organic light emitting diode display according to an embodiment of the present invention. It is a graph showing the change of the gamma data voltage according to the data value of the control signal. 7A and 7B , the horizontal axis of the graph indicates the data value DBV_Lv of the brightness control signal, and the vertical axis of the graph indicates the voltage value of each gamma data voltage for the red, green, and blue sub-pixels. The gamma data voltages shown in FIGS. 7A and 7B all represent gamma data voltages for red, green, and blue sub-pixels for 63 grayscales.

In FIG. 7A , the organic light emitting diode display according to the comparative example includes the same components as the organic light emitting diode display according to the exemplary embodiment of FIG. 7B except for the gamma data voltage generation circuit. The gamma data voltage generation circuit of the organic light emitting diode display according to the comparative example of FIG. 7A generates a gamma data voltage through one gamma unit, and is driven by changing the voltage value of the gamma data voltage as a whole according to the brightness control signal. On the other hand, the gamma data voltage generation circuit of the organic light emitting diode display according to the embodiment of FIG. 7B includes a first gamma unit, a second gamma unit, and a brightness control unit, and generates a gamma data voltage having the same resolution as that of the brightness control signal. print out

Referring to FIG. 7A , the gamma data voltage generation circuit provided in the organic light emitting diode display according to the comparative example outputs a gamma data voltage discontinuously changing according to the data value DBV_Lv of the brightness control signal, and the output gamma data voltage showed a reverse phenomenon. That is, when the brightness control signal in FIG. 7A has a data value of 847, the red gamma data voltage for driving the red sub-pixel is discontinuously changed. That is, the brightness of the organic light emitting diode display according to the comparative example is discontinuously increased or decreased according to the brightness control signal.

On the other hand, referring to FIG. 7B , the gamma data voltage generation circuit provided in the organic light emitting diode display according to an embodiment of the present invention outputs a gamma data voltage that smoothly decreases or increases according to the data value DBV_Lv of the brightness control signal. did. The output gamma data voltage did not show an inversion phenomenon, and a discontinuously changing section was not observed. That is, the brightness of the organic light emitting diode display according to an embodiment of the present invention is increased or decreased in proportion to the change in the brightness control signal.

8A and 8B are graphs of color coordinates according to a brightness control signal for explaining an effect of a gamma data voltage generating circuit according to an embodiment of the present invention. Specifically, FIG. 8A is a graph illustrating a color coordinate change according to a data value of a brightness control signal in an organic light emitting diode display according to a comparative example, and FIG. 8B is a graph illustrating a brightness control signal in the organic light emitting diode display according to an embodiment of the present invention. It is a graph showing the color coordinate change according to the data value. In FIGS. 8A and 8B , the horizontal axis of the graph indicates the data value (DBV_Lv) of the brightness control signal, and the vertical axis of the graph indicates the x and y color coordinate values of the chromaticity diagram for 63 grayscale white and the luminance (Lv) of the white sub-pixel. represent each. Specifically, the left vertical axis of the graph represents the luminance Lv of the white sub-pixel, and the right vertical axis represents the x and y color coordinate values of the chromaticity diagram for white. The organic light emitting display device according to the comparative example of FIG. 8A and the organic light emitting display device according to the embodiment of FIG. 8B are the same as the organic light emitting display device according to the comparative example of FIG. 7A and the organic light emitting display device according to the embodiment of FIG. 7B , respectively Do.

Referring to FIG. 8A , the color coordinates and luminance of the organic light emitting diode display according to the comparative example are discontinuously changed according to the data value DBV_Lv of the brightness control signal. That is, in the organic light emitting diode display according to the comparative example, as the data value (DBV_Lv) of the brightness control signal was changed, the color coordinate of white was discontinuously and severely fluctuated, and the luminance of the white sub-pixel was discontinuously fluctuated in some sections. , it was confirmed that the color reproducibility of the organic light emitting diode display was significantly changed.

On the other hand, referring to FIG. 8B , the color coordinates of the organic light emitting diode display according to an exemplary embodiment are kept constant according to the data value DBV_Lv of the brightness control signal, and the luminance of the organic light emitting display device is continuously increased or decreased. That is, in the organic light emitting diode display according to an embodiment of the present invention, the x and y color coordinates for white are maintained uniformly as the data value DBV_Lv of the brightness control signal is changed, and the luminance of the white sub-pixel is controlled by the brightness. It was confirmed that the signal data value (DBV_Lv) was continuously increased or decreased as the data value (DBV_Lv) was changed. That is, the organic light emitting diode display according to the embodiment maintained constant color reproducibility regardless of the brightness control of the screen, and it was confirmed that the brightness of the organic light emitting display screen was smoothly brightened or darkened according to the brightness control signal.

Since the organic light emitting diode display according to an embodiment of the present invention includes a gamma data voltage generation circuit including a first gamma unit, a second gamma unit, and a brightness control unit, the brightness of the organic light emitting diode display is a data value of the brightness control signal. It can be softly lightened or darkened depending on the setting. As described above, the gamma point voltage output from the brightness control unit of the gamma data voltage generating circuit has the same resolution as the brightness control signal, and may be increased or decreased to correspond to the rate of change of the data value of the brightness control signal. That is, as the data value of the brightness control signal increases, the voltage value of the gamma point voltage output from the brightness control unit may increase or decrease at the same rate of change. Since the gamma point voltage is applied to the gamma data voltage output unit and the gamma point voltage is divided and output as the gamma data voltage, the brightness of the display panel driven based on the gamma data voltage can be smoothly increased or decreased, and Color reproducibility may be kept constant.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the technical spirit of the present invention. . Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

1000: organic light emitting display device
2000: Smartphone
PN: display panel
PX: Pixel
GL: gate wiring
DL: data wiring
SYS: system
TC: Timing Control
GIC: gate driver
DIC: data driver
GC: Gamma Data Voltage Generation Circuit
SO: output
100: first gamma part
110: first gamma reference voltage selector
111: multiplexer of the first gamma reference voltage selector
112: buffer of the first gamma reference voltage selector
120: second gamma reference voltage selector
121: multiplexer of the second gamma reference voltage selector
122: buffer of the second gamma reference voltage selector
123: resistance string of the second gamma reference voltage selector
130: third gamma reference voltage selector
140: fourth gamma reference voltage selector
150: fifth gamma reference voltage selector
160: sixth gamma reference voltage selector
170: seventh gamma reference voltage selector
171: multiplexer of the seventh gamma reference voltage selector
172: Buffer of the seventh gamma reference voltage selection unit
180: first gamma resistance string
200: second gamma part
210: first gamma selection voltage selection unit
220: second gamma selection voltage selection unit
230: third gamma selection voltage selection unit
240: fourth gamma selection voltage selection unit
250: fifth gamma selection voltage selection unit
260: sixth gamma selection voltage selection unit
280: second gamma resistance string
300: brightness control unit
310: first brightness control unit
311: staff selection unit of the first brightness control unit
312: resistance string of the first brightness control unit
313: gamma point voltage output unit of the first brightness control unit
320: second brightness control unit
360: sixth brightness control unit
400: gamma data voltage output unit

Claims (13)

a first gamma unit for outputting a gamma reference voltage for a preset reference gray level based on the brightness control signal;
a second gamma unit for outputting a gamma selection voltage for the reference grayscale based on the brightness control signal;
a brightness control unit receiving the gamma reference voltage and the gamma selection voltage, and selecting and outputting a gamma point voltage with respect to the reference grayscale having a voltage value between a voltage value of the gamma reference voltage and a voltage value of the gamma selection voltage ; and
and a gamma data voltage output unit receiving the gamma point voltage and outputting a gamma data voltage by dividing the gamma point voltage. According to claim 1,
The voltage value of the gamma point voltage is changed to correspond to the rate of change of the data value of the brightness control signal,
The gamma reference voltage is a maximum gamma point voltage having a largest voltage value among the gamma point voltages that change to correspond to a rate of change of a data value of the brightness control signal in an n-th band to which the brightness control signal belongs;
The gamma selection voltage is a maximum gamma point voltage having a largest voltage value among the gamma point voltages that change to correspond to a change rate of the data value of the brightness control signal in an n-1 th band adjacent to the n th band which is a gamma data voltage generation circuit. 3. The method of claim 2,
The brightness control unit,
a resistor string to which the gamma reference voltage is applied at one end;
a step selector configured to select a step start point such that the resistor string is divided by the number of steps between the n-th band and the n-1 th band, and apply the gamma selection voltage to the step start point; and
and a gamma point voltage output unit for selecting a gamma point voltage having a voltage value corresponding to the data value of the brightness control signal and outputting the gamma point voltage. 4. The method of claim 3,
The resistor string includes a plurality of resistors connected in series,
The step selector is a demultiplexer (DeMUX) including an input terminal for receiving the gamma selection voltage and a plurality of output terminals respectively contacted to a plurality of voltage dividing nodes between the plurality of resistors,
The gamma point voltage output unit is a multiplexer (MUX) including a plurality of input terminals respectively contacted to the plurality of nodes and an output terminal outputting the gamma point voltages. 3. The method of claim 2,
the first gamma unit outputs a gamma reference voltage to which an n-th optical compensation corresponding to the n-th band is applied;
and the second gamma unit outputs a gamma selection voltage to which an n-1 th optical compensation corresponding to the n-1 th band is applied. 6. The method of claim 5,
The first gamma unit,
a first gamma resistor string to which a high reference voltage is applied to one end and a low reference voltage is applied to the other end; and
and a gamma reference voltage selector for selecting and outputting the gamma reference voltage for the reference grayscale from the first gamma resistance string;
The second gamma unit,
a second gamma resistor string to which the high reference voltage is applied to one end and the low reference voltage is applied to the other end; and
and a gamma selection voltage selection unit for selecting and outputting the gamma selection voltage for the reference grayscale from the second gamma resistance string. a timing controller configured to generate a first gamma control signal and a second gamma control signal based on the brightness control signal; and
a data driver configured to provide a gamma data voltage to the display panel so that an image displayed on the display panel has a brightness corresponding to the data value of the brightness control signal based on the first gamma control signal and the second gamma control signal including,
The data driver,
a first gamma unit outputting a plurality of gamma reference voltages respectively corresponding to a plurality of preset reference grayscales based on the first gamma unit control signal;
a second gamma unit outputting a plurality of gamma selection voltages respectively corresponding to the plurality of reference grayscales based on the second gamma unit control signal;
Receive the plurality of gamma reference voltages and the plurality of gamma selection voltages, respectively, and a plurality of gamma point voltages respectively corresponding to the plurality of reference grayscales based on the plurality of gamma reference voltages and the plurality of gamma selection voltages a plurality of brightness control units to select and output; and
a gamma data voltage output unit receiving the plurality of gamma point voltages and dividing the plurality of gamma point voltages to output a gamma data voltage;
The voltage value of the gamma data voltage is increased or decreased to correspond to a rate of change of the data value of the brightness control signal as the data value of the brightness control signal increases. delete 8. The method of claim 7,
A first brightness control unit among the plurality of brightness control units receives a first gamma reference voltage among the plurality of gamma reference voltages, receives a first gamma selection voltage among the plurality of gamma selection voltages, and the first gamma reference voltage selecting a first gamma point voltage having a voltage value between a voltage value of
a second brightness control unit among the plurality of brightness control units selects a second gamma point voltage in the same manner as the first brightness control unit;
The voltage value of the first gamma point voltage and the voltage value of the second gamma point voltage increase in proportion to the brightness control signal as the data value of the brightness control signal increases, respectively, or decrease in inverse proportion to the brightness control signal An organic light emitting display device, characterized in that it becomes. 10. The method of claim 9,
The first gamma unit,
a first gamma resistor string to which a high reference voltage is applied to one end and a low reference voltage is applied to the other end; and
a plurality of gamma reference voltage selectors for selecting and outputting the plurality of gamma reference voltages respectively corresponding to the plurality of reference grayscales from the first gamma resistance string;
The second gamma unit,
a second gamma resistor string to which the high reference voltage is applied to one end and the low reference voltage is applied to the other end; and
and a plurality of gamma selection voltage selectors for selecting and outputting the plurality of gamma selection voltages respectively corresponding to the plurality of reference grayscales from the second gamma resistance string. 11. The method of claim 10,
The plurality of gamma reference voltage selectors are cascaded to each other,
and the plurality of gamma selection voltage selectors are cascaded to each other. 11. The method of claim 10,
a lowest gamma reference voltage selector configured to select a gamma reference voltage corresponding to a lowest gray level from among the plurality of gamma reference voltage selectors of the first gamma unit is directly connected to the gamma data voltage output unit;
and the lowest gamma reference voltage selected by the lowest gamma reference voltage selector is directly applied to the gamma data voltage output unit. 13. The method of claim 12,
Each of the plurality of brightness control string units is 1:1 connected to the remaining gamma reference voltage selectors except for the lowest gamma reference voltage selector of the first gamma unit.

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