KR20140005607A - Pixel circuit, display panel having the same, and organic light emmiting display device - Google Patents

Abstract

A pixel circuit includes an organic light emitting diode, a driving transistor connected to the organic light emitting diode and controlling a current flowing along the organic light emitting diode between a low voltage and a high voltage, and a light emitting control circuit connected to a driving transistor and driving the driving transistor. At this time, the size of the driving transistor is determined based on the distance of a power supply part supplying the high and the lower voltage.

Description

Pixel circuit, display panel and organic light emitting display device including the same {PIXEL CIRCUIT, DISPLAY PANEL HAVING THE SAME, AND ORGANIC LIGHT EMMITING DISPLAY DEVICE}

The present invention relates to a display device. More particularly, the present invention relates to a pixel circuit for displaying an image of uniform luminance, a display panel having the same, and an organic light emitting display device.

The OLED display includes a plurality of pixel circuits defined by vertically intersecting scan lines and data lines, and power lines for supplying power to the pixel circuits. Each pixel circuit includes a driving transistor and exhibits luminance by controlling a current flowing through the organic light emitting diode by the driving transistor.

At this time, the voltage drop (IR-drop) phenomenon is smaller as the power line is closer to the power supply, while the voltage drop phenomenon increases as the power line is farther from the power supply. Conventional organic light emitting diode display has a problem that even if the same data signal is applied due to uneven voltage drop of the power line according to the position of each pixel circuit, the current variation flowing through the organic light emitting diode is different for each pixel circuit, which intensifies the luminance variation. . This is emerging as a bigger problem as the display panel becomes larger.

An object of the present invention is to provide a pixel circuit capable of compensating for a voltage drop by differentially designing a size of a driving transistor based on a distance from a power supply.

Another object of the present invention is to provide a display panel including the pixel circuit.

Another object of the present invention is to provide an organic light emitting display device including the display panel.

It is to be understood, however, that the present invention is not limited to the above-described embodiments and various modifications may be made without departing from the spirit and scope of the invention.

In order to achieve the object of the present invention, a pixel circuit according to an embodiment of the present invention is an organic light emitting diode, a current connected to the organic light emitting diode flowing through the organic light emitting diode between a high power supply voltage and a low power supply voltage And a light emitting control circuit connected to the driving transistor to drive the driving transistor. In this case, the size of the driving transistor may be determined based on a distance between the high power supply voltage and the power supply unit providing the low power supply voltage.

In example embodiments, the size of the driving transistor may increase as the distance from the power supply increases.

According to one embodiment, the distance from the power supply may correspond to the distance from the main power line.

In order to achieve another object of the present invention, the display panel according to the embodiments of the present invention, a plurality of pixel circuits, a plurality of scan lines for transmitting a scan signal provided from the scan driver to the pixel circuits, data driver And a plurality of data lines for transmitting a data signal provided from the plurality of pixel circuits to the pixel circuits, and a plurality of power lines for transmitting the high power voltage and the low power supply voltage provided from the power supply unit to the pixel circuits. In this case, the size of the driving transistor provided in each of the pixel circuits may be determined based on a distance from the power supply unit.

In example embodiments, the size of the driving transistor may increase as the distance from the power supply increases.

In example embodiments, the power lines may include a main power line connected to the power supply unit and sub power lines connected between the pixel circuits and the main power line.

In example embodiments, the distance from the power supply unit may correspond to a distance from the main power line.

In accordance with another aspect of the present invention, an organic light emitting display device includes a display panel including a plurality of pixel circuits and a scan signal provided to the pixel circuits through a plurality of scan lines. A scan driver, a data driver providing a data signal to the pixel circuits through a plurality of data lines, a power supply unit providing a high power voltage and a low power voltage to the pixel circuits through a plurality of power lines, and the scan driver The timing controller may control the data driver and the power supply. In this case, the size of the driving transistor provided in each of the pixel circuits may be determined based on a distance from the power supply unit.

In example embodiments, the size of the driving transistor may increase as the distance from the power supply increases.

In example embodiments, the power lines may include a main power line connected to the power supply unit and sub power lines connected between the pixel circuits and the main power line.

In example embodiments, the distance from the power supply unit may correspond to a distance from the main power line.

In example embodiments, the main power line may be positioned at one side end of the display panel.

In example embodiments, the main power line may be positioned at a plurality of side ends of the display panel.

In example embodiments, the display panel is divided into two or more pixel regions, and the driving transistors of the pixel circuits positioned in the same pixel region of the display panel may have the same size.

In example embodiments, each of the pixel areas may be divided by grouping the pixel circuits into at least one horizontal line unit.

The pixel circuit according to the embodiments of the present invention compensates the voltage drop by differentially designing the size of the driving transistor based on the distance from the power supply (that is, designing the size of the driving transistor as the distance from the power supply increases). can do.

The display panel according to the exemplary embodiments of the present invention may include the pixel circuit to display an image having uniform luminance by minimizing a voltage drop phenomenon.

The organic light emitting diode display according to the exemplary embodiments of the present invention can output a high quality image by providing the display panel.

However, the effects of the present invention are not limited thereto, and various modifications may be made without departing from the spirit and scope of the present invention.

1 is a diagram illustrating a pixel circuit according to example embodiments.
2 is a diagram illustrating a display panel according to an exemplary embodiment of the present invention.
3 is a diagram illustrating an example in which sizes of driving transistors of pixel circuits are differentially designed in the display panel of FIG. 2.
FIG. 4 is a diagram illustrating another example in which sizes of driving transistors of pixel circuits are differentially designed in the display panel of FIG. 2.
FIG. 5 is a diagram illustrating still another example in which sizes of driving transistors of pixel circuits are differentially designed in the display panel of FIG. 2.
6 is a diagram illustrating an example in which sizes of driving transistors of pixel circuits are differentially designed by grouping pixel circuits in the display panel of FIG. 2.
7 is a block diagram illustrating an organic light emitting display according to embodiments of the present invention.

For the embodiments of the invention disclosed herein, specific structural and functional descriptions are set forth for the purpose of describing an embodiment of the invention only, and it is to be understood that the embodiments of the invention may be practiced in various forms, The present invention should not be construed as limited to the embodiments described in Figs.

As the inventive concept allows for various changes and numerous modifications, particular embodiments will be illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms may be used for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprise", "having", and the like are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed as meaning consistent with meaning in the context of the relevant art and are not to be construed as ideal or overly formal in meaning unless expressly defined in the present application .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1 is a diagram illustrating a pixel circuit according to example embodiments.

Referring to FIG. 1, the pixel circuit 100 may include an organic light emitting diode 110, a driving transistor 120, and a light emission control circuit 130.

The organic light emitting diode 110 is connected between the driving transistor 120 and the low power supply voltage ELVSS. Specifically, the organic light emitting diode 110 includes an anode electrode connected to the driving transistor 120 and a cathode electrode connected to the low power supply voltage ELVSS. The organic light emitting diode 110 generates light having a predetermined luminance based on a current flowing through the organic light emitting diode 110 between the high power supply voltage ELVDD and the low power supply voltage ELVSS.

The driving transistor 120 is connected to the organic light emitting diode 110 to adjust a current flowing through the organic light emitting diode 110 between the high power voltage ELVDD and the low power supply voltage ELVSS. In detail, the driving transistor 120 includes a first electrode and a second electrode, and outputs a driving current according to a voltage applied to the gate electrode. Here, the first electrode is set to any one of a drain electrode and a source electrode, and the second electrode is set to an electrode different from the first electrode. For example, if the first electrode is set as the source electrode, the second electrode is set as the drain electrode. In one embodiment, the gate electrode of the driving transistor 120 is connected to the light emission control circuit 130, the first electrode of the driving transistor 120 is connected to the high power voltage ELVDD, The second electrode may be connected to the anode electrode of the organic light emitting diode 110. The driving transistor 120 controls the current flowing through the organic light emitting diode 110 between the high power supply voltage ELVDD and the low power supply voltage ELVSS based on a data signal applied from the light emission control circuit 130. do.

In general, driving current characteristics in the driving region of the driving transistor 120 are represented by Equation 1 below.

[Equation 1]

Referring to [Equation 1], the output current of the driving transistor 120 is proportional to the width (W) of the driving transistor 120, and inversely proportional to the length (L). Accordingly, in the present embodiment, the size of the driving transistor 120 is differentially designed based on the distance from the power supply unit providing the high power supply voltage ELVSS and the low power supply voltage ELVSS, thereby providing a voltage of the high power supply voltage ELVDD. You can compensate for the descent. Specifically, the size of the driving transistor 120 included in each of the pixel circuits 100 is designed to increase in the direction of the arrow A (that is, as the distance from the power supply increases), thereby corresponding to the same data signal. The same current is allowed to flow in all the pixel circuits 100. At this time, the distance from the power supply may correspond to the distance from the main power line. Therefore, according to the present invention, the voltage according to the voltage drop generated as the length of the high power voltage ELVDD line becomes longer may be compensated for each pixel circuit 100.

The light emission control circuit 130 may be connected to the driving transistor 120 to drive the driving transistor 120. In detail, the emission control circuit 130 may be connected to a scan line and a data line to receive a scan signal from the scan line and to receive a data signal from the data line.

2 is a diagram illustrating a display panel according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the display panel 200 includes pixel circuits 210, scan lines S1,..., Sn, data lines D1,..., And Dm, and power lines 220. , 230).

Each of the pixel circuits 210 may be formed in an area partitioned by scan lines S1, Sn, and data lines D1, Dm. In detail, the pixel circuits 210 receive a data signal when a scan signal is supplied, and convert a current corresponding to the supplied data signal from the high power supply voltage ELVDD to the low power supply voltage ELVSS via the organic light emitting diode. While supplying, an image having a predetermined brightness is displayed. Each of the pixel circuits 210 may include a driving transistor. In this case, the size of the driving transistor provided in each of the pixel circuits 210 may vary from the power supply unit based on the distance from the power supply unit providing the high power voltage ELVDD and the low power supply voltage ELVSS. It can be designed to grow larger as it increases.

As such, the display panel 200 may include a plurality of pixel circuits 210 that differentially design the size of the driving transistor based on the distance from the power supply unit, thereby minimizing voltage drop, thereby obtaining uniform luminance. .

The scan lines S1,..., Sn may transfer scan signals provided from the scan driver to the pixel circuits 210. The data lines D1,..., And Dm may transfer data signals provided from the data driver to the pixel circuits 210.

The power lines 220 and 230 may transfer the high power voltage ELVDD and the low power voltage ELVSS provided from the power supply to the pixel circuits 210. Here, the power lines 220 and 230 may include a main power line 220 connected to the power supply unit and sub power lines 230 connecting the pixel circuits 210 and the main power line 220. Can be. However, for convenience of description, the power lines 220 and 230 are described as applying the high power voltage ELVDD and the low power voltage ELVSS, but through the power lines 220 and 230. The high power supply voltage ELVDD may be applied, and the low power supply voltage ELVSS may be commonly applied to the cathode electrodes of the organic light emitting diodes respectively provided in the pixel circuits 210.

In detail, the main power line 220 may be located at one side end of the display panel 200. In this case, the distance from the power supply unit may correspond to the distance from the main power line 220.

In FIG. 2, the main power line 220 is illustrated as being positioned at one side end of the display panel 200, but the present invention is not limited thereto. That is, the main power line 220 may be located at one side end of the display panel 200, but may also be located at a plurality of side ends of the display panel 200.

3 is a diagram illustrating an example in which sizes of driving transistors of pixel circuits are differentially designed in the display panel of FIG. 2.

Referring to FIG. 3, the high power voltage ELVDD may be applied at the lower end of the display panel 300. In this case, the voltage drop of the high power voltage ELVDD increases as the arrow A reaches the upper end of the display panel 300, thereby reducing the luminous current and lowering the luminance. Accordingly, the display panel 300 of FIG. 3 may include pixel circuits including driving transistors each of which increases in size as the distance from the power supply increases, based on the distance from the power supply providing the high power voltage ELVDD. Include. Accordingly, the display panel 300 illustrated in FIG. 3 may display an image having a uniform brightness by compensating for a pixel circuit in a voltage drop phenomenon of the high power voltage ELVDD generated as the power supply unit moves away from the power supply unit. .

4 is a diagram illustrating another example in which sizes of driving transistors of pixel circuits are differentially designed in the display panel of FIG. 2.

Referring to FIG. 4, the high power voltage ELVDD may be applied at the upper and lower ends of the display panel 400. Since the high power voltage ELVDD is applied at the lower end of the display panel 400, the voltage drop of the high power voltage ELVDD increases as the arrow A goes toward the center of the display panel 400. Since the ELVDD is also applied to the upper end of the display panel 400, the voltage drop of the high power voltage ELVDD increases toward the center of the display panel 400 along the arrow B. FIG. That is, the voltage drop of the high power voltage ELVDD increases as the center portion of the display panel 400 increases, and thus, the luminous current decreases and the luminance decreases. Accordingly, the display panel 400 of FIG. 4 may include pixel circuits including driving transistors each of which increases in size as the distance from the power supply increases, based on the distance from the power supply providing the high power voltage ELVDD. Equipped. Accordingly, the display panel 400 illustrated in FIG. 4 may display an image having a uniform brightness by compensating for a pixel circuit in the voltage drop phenomenon of the high power voltage ELVDD generated as the power supply unit moves away from the power supply unit. .

FIG. 5 is a diagram illustrating another example in which sizes of driving transistors of pixel circuits are differentially designed in the display panel of FIG. 2.

Referring to FIG. 5, the high power voltage ELVDD may be applied on the slope of the display panel 500. Since the high power voltage ELVDD is applied at the lower end of the display panel 500, the voltage drop of the high power voltage ELVDD increases as the arrow A goes toward the center of the display panel 500. Since the ELVDD is applied to the upper end of the display panel 500, the voltage drop of the high power voltage ELVDD increases toward the center of the display panel 400 along the arrow B. FIG. In addition, since the high power supply voltage ELVDD is also applied to the left side of the display panel 500, the voltage drop of the high power supply voltage ELVDD increases toward the center of the display panel 500 along the arrow C. Since the original voltage ELVDD is also applied to the right side of the display panel 500, the voltage drop of the high power voltage ELVDD increases toward the center of the display panel 500 along the arrow D. That is, the voltage drop of the high power voltage ELVDD increases toward the center portion of the display panel 400, and thus, the luminous current is reduced and the luminance is lowered. Accordingly, the display panel 500 of FIG. 5 includes pixel circuits including driving transistors each of which increases in size as the distance from the power supply increases, based on the distance from the power supply providing the high power voltage ELVDD. do. Accordingly, the display panel 500 illustrated in FIG. 5 may display an image having a uniform brightness by compensating for the pixel circuit unit of the voltage drop phenomenon of the high power voltage ELVDD generated as the power supply unit moves away from the power supply unit. .

6 is a diagram illustrating an example in which sizes of driving transistors of pixel circuits are differentially designed by grouping pixel circuits in the display panel of FIG. 2. However, since the remaining components except for the display panel 600 in FIG. 6 are the same as those shown in FIG. 2, the same components and overlapping descriptions will be omitted for convenience of description.

Referring to FIG. 6, the display panel 600 may be divided into two or more pixel areas 640, 650, and 660. In this case, the size of driving transistors of the pixel circuits 610 positioned in the same pixel area 640, 650, and 660 in the display panel 600 may be the same. Here, each of the pixel areas 640, 650, and 660 may be divided by grouping at least one pixel circuit 610 in units of horizontal lines. Meanwhile, in FIG. 6, although the main power line 620 connected to the power supply unit providing the high power voltage ELVDD and the low power voltage ELVSS is positioned at one side end of the display panel 600, the present invention is illustrated in FIG. This is not limited to this. Accordingly, the main power line 620 may be located at one side end of the display panel 600, but may be located at a plurality of side ends of the display panel 600.

7 is a block diagram illustrating an organic light emitting display according to embodiments of the present invention.

Referring to FIG. 7, the OLED display 700 may include a display panel 710, a scan driver 720, a data driver 730, a power supply (not shown), and a timing controller 760.

The display panel 710 may include a plurality of pixel circuits 770. Specifically, in the display panel 710, scan lines S1,..., Sn that transmit scan signals provided from the scan driver 720, and data that transmits data signals provided by the data driver 730. The plurality of power lines 740 and 750 and the scan lines S1, which transfer the lines D1,..., Dm, the high power voltage ELVDD and the low power voltage ELVSS provided from the power supply. Sn may be provided with a plurality of pixel circuits 770 formed at a position corresponding to an intersection point of the data lines D1 to Dm. In this case, each of the plurality of pixel circuits 770 may include driving transistors. In addition, the size of the driving transistor provided in each of the pixel circuits 770 may be determined based on a distance from the power supply unit. That is, the larger the distance from the power supply, the larger the size of the driving transistor, and the closer the distance from the power supply, the smaller the size of the driving transistor.

As such, the display panel 710 may include a plurality of pixel circuits 770 that differentially design the size of the driving transistor based on the distance from the power supply, thereby minimizing voltage drop and obtaining uniform luminance.

The scan driver 720 may provide a scan signal to the pixel circuits 770 through a plurality of scan lines S1,..., Sn. Here, the scan driver 720 sequentially supplies the scan signals to the scan lines S1,..., Sn by the timing controller 760. When the scan signal is sequentially supplied to the scan lines S1,..., Sn, the pixel circuit 770 is sequentially selected in units of horizontal lines.

The data driver 730 may provide a data signal to the pixel circuits 770 through the data lines D1,..., Dm. Here, the data driver 730 is controlled by the timing controller 760 to supply data signals to the data lines D1,..., Dm. Here, the data signal is supplied to the pixel circuits 770 selected by the scan signal, and each of the pixel circuits 770 stores a voltage corresponding to the data signal supplied thereto, in the storage capacitor of the emission control circuit.

The power supply unit may provide the high power voltage ELVDD and the low power voltage ELVSS to the pixel circuits 770 through the plurality of power lines 740 and 750. Here, the plurality of power lines 740 and 750 may include the main power line 740 connected to the power supply unit and the sub power lines 740 connecting the pixel circuits 770 and the main power line 750. It may include. Here, the distance from the power supply may correspond to the distance from the main power line 740.

Meanwhile, in FIG. 7, the main power line 740 connected to the power supply unit is shown at the lower end of the display panel 710. In this case, as the distance from the power supply unit increases, the size of the driving transistor increases, so that the size of the driving transistor included in each of the pixel circuits 770 increases toward the upper end of the display panel 710. However, the present invention is not limited thereto. That is, according to an exemplary embodiment, the main power line 740 of the present invention may be located at a plurality of side ends of the display panel 710.

The timing controller 760 generates a plurality of control signals and provides the control signals to the scan driver 720, the data driver 730, and the power supply unit, thereby supplying the scan driver 720, the data driver 730, and the power supply. You can control wealth.

As described above, the organic light emitting diode display 700 may include a display panel 710, a scan driver 720, a data driver 730, a power supply unit, a timing controller 760, and the like. In this case, the display panel 710 may include a plurality of pixel circuits 770, and each of the pixel circuits 770 may include driving transistors having different sizes, respectively, based on a distance from the power supply unit. As such, the organic light emitting diode display 700 includes a pixel circuit capable of compensating for the reduction of the light emission current due to the voltage drop generated according to the distance from the power supply by adjusting the size of the driving transistor, thereby providing uniform luminance. It may have a display panel 710 having a. Accordingly, the organic light emitting diode display 700 may display an image having a uniform luminance (that is, output a high quality image).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, and that various changes and modifications may be made without departing from the scope of the appended claims, It is natural to belong to the scope.

110: organic light emitting diode
120: driving transistor
130: light emission control circuit
200, 300, 400, 500, 600, 710: display panel
100, 210, 610, 770: pixel circuit
220, 620, 740: main power line
230, 630, 750: sub power line
640, 650, 660: pixel area
700: organic light emitting display
720: scan driver
730: data driver
760: timing controller

Claims (15)

Organic light emitting diodes;
A driving transistor connected to the organic light emitting diode to regulate a current flowing through the organic light emitting diode between a high power supply voltage and a low power supply voltage; And
A light emission control circuit connected to the driving transistor to drive the driving transistor;
And the size of the driving transistor is determined based on a distance between the high power supply voltage and a power supply providing the low power supply voltage. The pixel circuit of claim 1, wherein a size of the driving transistor increases as a distance from the power supply increases. The pixel circuit of claim 1, wherein a distance from the power supply unit corresponds to a distance from a main power line. A plurality of pixel circuits;
A plurality of scan lines transferring scan signals provided from a scan driver to the pixel circuits;
A plurality of data lines transferring a data signal provided from a data driver to the pixel circuits; And
A plurality of power lines for delivering a high power supply voltage and a low power supply voltage provided from a power supply to the pixel circuits,
The size of the driving transistor provided in each of the pixel circuits is determined based on a distance from the power supply. The display panel of claim 4, wherein the size of the driving transistor increases as the distance from the power supply increases. The display panel of claim 5, wherein the power lines include a main power line connected to the power supply and sub power lines connected between the pixel circuits and the main power line. The display panel of claim 6, wherein a distance from the power supply unit corresponds to a distance from the main power line. A display panel having a plurality of pixel circuits;
A scan driver configured to provide a scan signal to the pixel circuits through a plurality of scan lines;
A data driver configured to provide a data signal to the pixel circuits through a plurality of data lines;
A power supply unit configured to provide a high power voltage and a low power voltage to the pixel circuits through a plurality of power lines; And
A timing controller to control the scan driver, the data driver, and the power supply unit,
The size of the driving transistor provided in each of the pixel circuits is determined based on a distance from the power supply. The organic light emitting diode display of claim 8, wherein the size of the driving transistor increases as the distance from the power supply increases. The organic light emitting diode display of claim 9, wherein the power lines include a main power line connected to the power supply unit and sub power lines connected between the pixel circuits and the main power line. The organic light emitting diode display of claim 10, wherein the distance from the power supply corresponds to a distance from the main power line. The organic light emitting diode display of claim 11, wherein the main power line is positioned at one side end of the display panel. The organic light emitting diode display of claim 11, wherein the main power line is positioned at a plurality of side ends of the display panel. The organic light emitting diode display of claim 9, wherein the display panel is divided into two or more pixel regions, and the driving transistors of the pixel circuits positioned in the same pixel region of the display panel have the same size. . The organic light emitting diode display of claim 14, wherein each of the pixel areas is divided by grouping the pixel circuits into at least one horizontal line unit.

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