KR20070101545A - Display device - Google Patents

Abstract

A display device is provided to simplify a signal controller and a data driver by generating a data voltage based on a linear conversion of an image signal in the data driver. A display device includes four pixels, a signal controller(600) and a data driver(500). The signal controller executes a gamma conversion on a three color input image signal and generates a four color output image signal according to the gamma conversion. The data driver receives a reference voltage, generates a data voltage based on the output image signal, and supplies the generated data voltage to the pixels. The signal controller executes a gamma conversion on a three color input image signal, generates a four color luminance image signal having bit numbers higher than that of the input image signal, and generates the four color output image signal having bit numbers smaller than that of the input image signal.

Description

Display device {DISPLAY DEVICE}

1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of an organic light emitting diode display according to an exemplary embodiment of the present invention.

3 is a graph illustrating a gamma curve according to an exemplary embodiment of the present invention.

4 is a graph illustrating an operation of a data driver according to an exemplary embodiment of the present invention.

5 is a graph illustrating an operation of a data driver according to another exemplary embodiment of the present invention.

6 is a graph showing a gamma curve according to another exemplary embodiment of the present invention.

The present invention relates to a display device.

Recently, flat panel display devices that can replace cathode ray tubes (CRTs) have been actively researched. In particular, organic light emitting display devices are attracting attention as next-generation flat panel display devices due to their excellent luminance and viewing angle characteristics.

In general, in an active flat panel display, a plurality of pixels are arranged in a matrix form, and an image is displayed by controlling the light intensity of each pixel according to given luminance information. The organic light emitting diode display is a display device that displays an image by electrically exciting the fluorescent organic material. The organic light emitting diode display is self-luminous, has low power consumption, and has a fast response time of pixels, thereby easily displaying high quality video.

The organic light emitting diode display includes an organic light emitting diode (OLED) and a thin film transistor (TFT) driving the organic light emitting diode (OLED). The thin film transistor is classified into a polysilicon thin film transistor and an amorphous silicon thin film transistor according to the type of the active layer. The organic light emitting diode display employing the polysilicon thin film transistor has many advantages, and thus is widely used. However, the manufacturing process of the thin film transistor is complicated and thus the cost increases. In addition, it is difficult to obtain a large screen with such an organic light emitting display device. On the other hand, an organic light emitting diode display employing an amorphous silicon thin film transistor is easy to obtain a large screen and has a relatively smaller manufacturing process than an organic light emitting diode display employing a polysilicon thin film transistor.

The organic light emitting diode display includes a plurality of pixels representing one dot, and the organic light emitting layer of each pixel emits light of different colors, and the color of one dot is determined by the combination of these lights.

However, in a typical display device displaying one dot based on three color pixels of red, green, and blue, light efficiency may be deteriorated.

An object of the present invention is to provide a four-color display device further comprising a white.

According to an exemplary embodiment of the present invention, a display controller includes a signal controller for generating an output image signal of four colors having luminance information by gamma-converting an input image signal of four colors and three colors, and a reference. And a data driver configured to receive a voltage, generate a data voltage based on the output image signal, and supply the data voltage to the pixel.

The signal control unit gamma-converts the input image signals of the three colors to generate a luminance image signal of four colors having a higher number of bits than the input image signal, and reduces the number of bits of the luminance image signal. You can generate a signal.

The gamma conversion may be performed by different gamma functions according to colors of the input image signal.

The data voltage may have linearity with respect to the luminance of the output image signal.

The gamma conversion may include nonlinearity of the data voltage and luminance.

The data driver may output the non-linear data voltage with respect to the luminance of the output image signal.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A display device according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the organic light emitting diode display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, an organic light emitting diode display according to an exemplary embodiment of the present invention includes a display panel 300, a scan driver 400 connected to the display panel 300, a data driver 500, and a data driver 500. ) Includes a gray voltage generator 800 and a signal controller 600 for controlling the gray voltage generator 800.

The display panel 300 includes a plurality of signal lines G ₁ -G _n , D ₁ -D _m , a plurality of voltage lines (not shown), and a plurality of signal lines G-G _n , D ₁ -D _m , which are connected to them and arranged in a substantially matrix form. It includes a number of pixels PX.

Include - (D _m D ₁₎ signal lines _{(G 1 -G n, D 1} -D m) is a data line for transmitting a plurality of scan lines (G ₁ -G _n) and a data signal to pass the scanning signal. The scan lines G ₁ -G _n extend substantially in the row direction and are substantially parallel and separated from each other. The data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other. Each voltage line (not shown) transfers a driving voltage Vdd or the like.

Referring to FIG. 2, one pixel PX of the organic light emitting diode display according to an exemplary embodiment of the present invention, for example, the i th scan line G _i (i = 1, 2, ..., n) and the j th data The pixel PX connected to the line D _j (j = 1, 2, ..., m) includes an organic light emitting diode LD, a driving transistor Qd, a capacitor Cst, and a switching transistor Qs. do.

The switching transistor Qs is a three-terminal element and has a control terminal, an input terminal and an output terminal. Control terminal may be connected to the scanning line (G _i), an input terminal is connected with the data lines (D _j), the output terminal thereof is connected to the control terminal of the driving transistor (Qd). The switching transistor Qs transfers a data voltage in response to a scan signal applied through the scan line G _i .

The driving transistor Qd is also a three-terminal element and has a control terminal, an input terminal, and an output terminal. The control terminal is connected to the switching transistor Qs, the input terminal is connected to the driving voltage Vdd, and the output terminal is connected to the organic light emitting element LD. The driving transistor Qd flows an output current ILD whose magnitude varies depending on the voltage applied between the control terminal and the output terminal.

The capacitor Cst is connected between the control terminal and the input terminal of the driving transistor Qd. The capacitor Cst charges the data voltage applied to the control terminal of the driving transistor Qd through the switching transistor Qs and maintains it even after the switching transistor Qs is turned off.

The organic light emitting diode LD has an anode connected to the output terminal of the driving transistor Qd and a cathode connected to the common voltage Vcom. The organic light emitting element LD displays an image by emitting light at different intensities according to the output current ILD. The organic light emitting element LD emits light of one color or white color of the primary color depending on the material. Examples of the primary colors include three primary colors of red, green, and blue, and the desired color is represented by a spatial sum of these three primary colors. White is included to improve brightness. Pixels emitting red, green, blue, and white light are referred to as red pixels PR, green pixels PG, blue pixels PB, and white pixels PW, respectively.

The four-color pixels PX may be arranged in various forms.

When arranged in a stripe structure, the plurality of pixels PX is arranged in the form of a matrix, and the plurality of pixel rows and the plurality of pixel columns are provided.

Each pixel row includes pixels PX of four colors arranged in sequence, and each pixel column includes only one pixel PX of one of four colors pixels PR, PG, PB, and PW. The order of arrangement within the pixel rows can be reversed.

All the pixels PX may have substantially the same size or may have different sizes. The white pixel PW may be smaller than the red, green, and blue pixels PR, PG, and PB. In this way, a decrease in saturation due to the addition of the white pixel PW may be prevented. The red, green, and blue pixels PR, PG, and PB may have the same size.

The ratio of the sizes of the white pixels PW and the red, green, and blue pixels PR, PG, and PB is determined in consideration of the luminance and the target color temperature. The size of the white pixel PW may be half or one quarter of other pixels PR, PG, and PB.

Meanwhile, when the plurality of pixels PX are arranged in a checkerboard structure, each pixel row and each pixel column include two color pixels PX among four color pixels PX.

Pixel rows including green and red pixels PG and PR and pixel rows including blue and white pixels PB and PW are alternately arranged. From the column point of view, the pixel column including the green and blue pixels PG and PB and the pixel column including the red and white pixels PG and PW are alternately arranged.

The order of arrangement within the pixel rows and pixel columns may also be reversed.

All of the pixels PX may have substantially the same size and may have different sizes. The white pixels PW may be smaller than the red, green, and blue pixels PR, PG, and PB, and the red, green, and blue pixels PR, PG, and PB may have the same size and may have different sizes. have.

In the arrangement of the pixel PX of the checkered structure, the red, green, and blue pixels PR, PG, and PB cannot be equally large.

Since the human eye is relatively less sensitive to the change in the amount of blue light than the changes in the amount of red and green light, and therefore, the effect of the enlargement of the area of the blue pixel on the image quality is relatively small. It is preferable to make the stretched area larger than the stretched area of the red pixel PR and the green pixel PG.

In addition, if the area of the white pixel PW is reduced, it is possible to prevent deterioration of color level (color level, color saturation, chromaticity) that may appear due to an increase in luminance.

The switching transistor Qs and the driving transistor Qd are n-channel metal oxide semiconductor field effect transistors (FETs) made of amorphous silicon or polycrystalline silicon. However, at least one of these transistors Qs and Qd may be a p-channel MOSFET. In addition, the connection relationship between the transistors Qs and Qd, the capacitor Cst, and the organic light emitting diode LD may be changed.

Referring back to FIG. 1, the scan driver 400 is connected to the scan lines G ₁ -G _n of the display panel 300 to turn off the high voltage Von that can turn on the switching transistor Qs. Scan signals composed of a combination of the low voltages Voff are applied to the scan lines G ₁ -G _n , respectively.

The gray voltage generator 800 generates a gray voltage and outputs the gray voltage to the data driver 500.

The data driver 500 is connected to the data lines D ₁ -D _m of the display panel 300 to apply a data voltage representing the output image signal DAT ′ to the data lines D ₁ -D _m .

The data driver 500 includes at least one data driving integrated circuit (IC) connected to the data lines D ₁ -D _m .

The data driving IC includes a shift register, a latch, a digital-to-analog converter, and an output buffer, which are connected in turn.

The shift register transfers the output image signal DAT 'to the latch in response to the data clock signal HCLK when the horizontal synchronization start signal STH (or the shift clock signal) is input. When the data driver 500 includes a plurality of data driver ICs, the shift register of one driver IC sends the shift clock signal to the shift register of the next driver IC.

The latch stores the output video signal DAT 'and sends the stored output video signal DAT' to the digital-analog converter according to the load signal LOAD.

The digital-analog converter receives the gray voltage from the gray voltage generator 800, selects the gray voltage according to the output image signal DAT ', and sends the gray voltage to the output buffer.

The output buffer outputs the output voltage from the digital-analog converter as a data voltage to the data lines D ₁ -D _m , and maintains it for one horizontal period 1H.

The signal controller 600 controls operations of the scan driver 400, the data driver 500, the gray voltage generator 800, and the like. The signal controller 600 also includes a signal converter 650 for gamma-converting the input image signals R, G, and B to generate an output image signal DAT '. The operation of the signal converter 650 will be described in detail later.

Each of the driving devices 400, 500, 600, and 800 may be mounted directly on the display panel 300 in the form of at least one integrated circuit chip, or mounted on a flexible printed circuit film (not shown). And may be attached to the display panel 300 in the form of a tape carrier package (TCP) or mounted on a separate printed circuit board (not shown). Alternatively, these driving devices 400, 500, 600, and 800 may be integrated in the display panel 300 along with the signal lines G ₁ -G _n , D ₁ -D _m and the thin film transistor switching elements Qs and Qd. It may be. In addition, the driving devices 400, 500, 600, and 800 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside the single chip.

3 and 4, a gamma conversion according to an embodiment of the present invention will be described.

3 is a graph illustrating a gamma transformation according to an exemplary embodiment of the present invention, and FIG. 4 is a graph illustrating an operation of a data driver according to an exemplary embodiment of the present invention.

The signal controller 600 receives three color input image signals R, G, and B and an input control signal for controlling the display thereof from an external graphic controller (not shown). The input image signals R, G, and B have 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 (= 2 ⁶ ) gray levels of each pixel PX based on three colors. . Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

Referring to FIG. 3, the signal converter 650 converts three color input image signals R, G, and B into luminance image signals DAT having luminance information according to a gamma function Γ (x). The gamma function Γ (x) is an increase function and a one-to-one function in which the luminance increases as the gray level increases.

When the input image signals R, G, and B are 256-bit 8-bit digital data, the luminance image signal DAT may be digital data having a higher number of bits, for example, 15 bits. Since the luminance can be added or decreased as a physical quantity indicating the amount of light per unit area, the white luminance image signal DAT can be extracted from the luminance image signal DAT of three colors. Therefore, the signal converter 650 extracts the white luminance image signal DAT from the three-color luminance image signal DAT, and the three-color luminance image signal DAT according to the extracted white luminance image signal DAT. ) In this case, a method of extracting the white luminance image signal DAT and correcting the three luminance image signals DAT may be implemented in various ways. For example, the luminance of the red, green, and blue luminance image signals DAT may be different. In the case of (10, 25, 30), the luminance of the white luminance image signal DAT has the minimum value of 10 among the three colors, and the luminance image signal DAT of the three colors is (0, 15) which is the value obtained by subtracting the luminance of white. , 20) may be implemented.

Next, the signal converter 650 generates a four-color output image signal DAT ′ having a lower number of bits of the white luminance image signal DAT and the corrected three-color luminance image signal DAT. This can be implemented simply by discarding the upper bits or the lower bits. Therefore, the four-color output image signal DAT 'may have a number of bits that is equivalent to the input image signals R, G, and B, such as 8 bits or 10 bits.

Finally, the signal converter 650 arranges the output image signals DAT 'of four colors according to the control of the signal controller 600, and outputs them to the data driver 500. Therefore, the four-color output video signal DAT 'is input to the data driver 500 without changing the gamma information (the brightness to the gray scale) without the luminance information.

The signal converter 650 may include a frame memory (not shown) or a lookup table (not shown) for generating such an output image signal DAT '.

In this case, the signal converter 650 may perform independent gamma conversion according to different gamma functions Γ (x) according to the lifespans of the red, green, and blue organic light emitting diodes LD. However, when the organic light emitting diode display includes only the white organic light emitting diode LD and displays various colors through the color filter, the gamma function using the gamma function Γ (x) of the white organic light emitting diode LD is used. You can perform the conversion.

The signal controller 600 also generates the scan control signal CONT1, the data control signal CONT2, the gray scale control signal CONT3, and the like, and then sends the scan control signal CONT1 to the scan driver 400 and controls the data. The signal CONT2 and the processed output image signal DAT 'are sent to the data driver 500.

The scan control signal CONT1 includes a scan start signal STV indicating a scan start and at least one clock signal for controlling an output period of the high voltage Von. The scan control signal CONT1 may further include an output enable signal OE that defines the duration of the high voltage Von.

The data control signal CONT2 is an analog data voltage applied to the horizontal synchronization start signal STH and the data lines D ₁ -D _m indicating the start of transmission of the digital output image signal DAT 'for one row of pixels PX. It includes a load signal LOAD and a data clock signal HCLK to apply (Vdat).

The signal controller 600 outputs a four-color output image signal DAT 'of red, green, blue, and white, a scan control signal CONT1, and a data control signal CONT2.

The data driver 500 receives the output image signal DAT ″ from the signal controller 600, and receives the upper voltage V _H and the lower voltage V _L from the gray voltage generator 800.

As shown in FIG. 4, when the linearity of the data voltage Vdat is guaranteed with respect to the luminance of the output image signal DAT ', the data driver 500 determines the upper voltage V _H according to the luminance of the output image signal DAT'. The voltage difference between the and lower voltage V _L is divided into equal parts and the corresponding voltage is output as an analog data voltage Vdat.

The scan driver 400 converts the scan signal applied to the scan signal lines G ₁ -G _n into a high voltage Von according to the scan control signal CONT1 supplied from the signal controller 600.

Then, the switching transistor Qs of the pixel PX is turned on according to the high voltage Von supplied to the pixel PX. Then, the driving transistor Qd of each pixel PX receives the corresponding data voltage Vdat through the turned-on switching transistor Qs. Each driving transistor Qd outputs a driving current I _LD corresponding to the applied data voltage Vdat to the organic light emitting diode LD. Accordingly, the organic light emitting diode LD emits light having a size corresponding to the driving current I _LD .

As such, the four pixels PX emit light to display the color of one dot, and the white pixel PW is further included to maintain high luminance as a whole.

This operation proceeds to the pixel PX of the nth row in order to display one image.

The organic light emitting diode display according to the present invention generates a white output image signal DAT 'by gamma-converting grayscale to luminance, and converts the output image signal DAT' having luminance information into a data voltage Vdat without degamma conversion. Linear conversion simplifies the operation of the signal controller 600 and the digital-to-analog conversion of the data driver 500.

On the other hand, the organic light emitting diode display has a nonlinear relationship in which luminance and data voltage Vdat are not linear because the operating characteristics of the driving transistor Qd and the operating characteristics of the organic light emitting diode LD are flexible according to environmental conditions and device conditions. Can have a relationship.

Hereinafter, another embodiment of the present invention will be described with reference to FIGS. 5 and 6.

5 is a graph illustrating an operation of a data driver according to another exemplary embodiment of the present invention, and FIG. 6 is a graph illustrating a gamma curve according to another exemplary embodiment of the present invention.

The data driver 500 according to another exemplary embodiment of the present invention receives the four-color output image signal DAT ′ having luminance information from the signal controller 600 as shown in FIG. 3.

In addition, as shown in FIG. 5, the data driver 500 includes a plurality of gray voltage sets having a plurality of levels, for example, gray voltages including six levels of gray voltages Vga0, Vga1, Vga2, Vga3, Vga4, Vga5, and Vga6. Get a set.

The data driver 500 outputs a nonlinear data voltage Vdat with respect to the luminance of the output image signal DAT ', and the nonlinear function f (x) includes information about environmental conditions and device conditions.

Meanwhile, in the gamma conversion performed by the signal converter 650, as shown in FIG. 6, the nonlinear function f (x) between the luminance and the data voltage Vdat is combined with the gamma function Γ (x) of the luminance and the gray scale. The luminance image signal DAT may be generated using one correction gamma function Γ '(x). In this case, the output image signal DAT 'based on the luminance image signal DAT also includes luminance information and non-linear information between the luminance and the data voltage Vdat. The data voltage Vdat may be generated by supplying only (V _H ) and the lower voltage V _L and dividing them linearly according to the luminance of the output image signal DAT ′.

Therefore, while simplifying the digital-to-analog conversion of the data driver 500, non-linearity between luminance and data voltage may also be reflected.

The logic of the signal controller 600 and the data driver 500 may be applied not only to the organic light emitting display but also to a liquid crystal display including white pixels.

As described above, according to the present invention, since the gamma conversion is performed to generate an image signal having luminance information, and the data driver linearly converts the image signal to generate a data voltage, the signal controller and the data driver of the display device including white pixels are generated. The logic can be simplified.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (6)

4 colored pixels, A signal controller which gamma-converts the input video signal of three colors to generate an output video signal of four colors having luminance information; and A data driver configured to receive a reference voltage and generate a data voltage based on the output image signal and supply the data voltage to the pixel Display device comprising a. In claim 1, The signal control unit gamma-converts the input image signals of the three colors to generate a luminance image signal of four colors having a higher number of bits than the input image signal, and reduces the number of bits of the luminance image signal. Display device for generating signals. In claim 2, The gamma conversion is performed by different gamma functions according to colors of the input image signal. In claim 2, And the data voltage is linear with respect to the luminance of the output image signal. The method according to any one of claims 1 to 4, And the gamma conversion comprises nonlinearity of the data voltage and luminance. In claim 2, And the data driver outputs the non-linear data voltage with respect to the luminance of the output image signal.

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