KR100741977B1 - Organic Electroluminescence Display Device and Driving Method of the same - Google Patents

Abstract

Disclosed are an organic electroluminescent display device in which luminance is automatically adjusted according to an area emitted from a display panel, and a driving method thereof. The organic electroluminescent display adjusts the luminance to adjust the gamma reference voltage or data value of the data driver or to apply a control signal for adjusting the emission duty of the emission control signal of the emission control driver according to the area where a plurality of pixels emit light. Contains wealth. As the light emission area increases, the brightness controller decreases the brightness by increasing the gamma reference voltage or increasing the data value. In addition, as the light emission area is increased, the brightness controller reduces the light emission duty of the light emission control signal to reduce the brightness. Therefore, even if the light emitting area is small, the brightness is increased to improve the contrast ratio, and the power consumption can be reduced by limiting the driving current by adjusting the light emitting duty of the light emitting control signal. The lifetime of the organic EL can be increased due to the reduced power consumption.

Description

Organic electroluminescence display device and driving method thereof

1 is a block diagram illustrating an organic light emitting display device according to a first embodiment of the present invention.

2 is a graph illustrating a relationship between a light emitting area and a luminance of an organic electroluminescent display according to a first exemplary embodiment of the present invention.

3 is a block diagram illustrating a brightness controller of an organic light emitting display device according to a first embodiment of the present invention.

4 is a block diagram illustrating a brightness controller of an organic light emitting display device according to a second embodiment of the present invention.

5 is a block diagram illustrating a brightness controller of an organic light emitting display device according to a third embodiment of the present invention.

6 is a circuit diagram illustrating a representative pixel of an organic electroluminescent display device according to a first embodiment, a second embodiment, and a third embodiment of the present invention.

FIG. 7 is a timing diagram of light emission control signals having different light emission duty according to the light emitting area when the brightness controller shown in FIG. 5 of the third embodiment is operated.

FIG. 8 is a timing diagram illustrating a light emission control signal having a multi light emission duty in accordance with the luminance adjusting unit shown in FIG. 5 according to the third embodiment.

* Description of the main parts of the drawings *

10 display panel 12 pixel portion

14: scan driver 16: light emission control driver

20: data driver 30: luminance control unit

31,31 ', 32: Data counter 33,33', 34: Data adder

35,35 ', 36: Memory 37: Gamma Reference Controller

37 ': data value controller 38: emission duty controller

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display, and more particularly, to an organic electroluminescent display and a method of driving the same, the luminance of which is automatically adjusted according to the area of the display panel.

The flat panel display has been researched and developed due to the advantages of reducing the weight and size of the display device using a cathode ray tube, and as a result, a liquid crystal display (LCD) and a field emission display (Field Emission Display) FED), plasma display panels (PDPs), and organic electroluminescent display devices (hereinafter referred to as organic EL display devices) have been developed and put into practical use. Among them, PDPs have a problem of large screen configuration, but have a problem of large power consumption due to low luminous efficiency and low luminance, and a large power consumption of LCDs because of slow response speed and light emission by the backlight.

On the other hand, the organic EL display device emits light using organic materials, and has a wider viewing angle, faster response speed, better contrast as a self-luminous device, and better visibility than an LCD. In addition, since the backlight is not required, the thickness and weight can be reduced.

However, when the organic EL display device constitutes a large screen, the size of the EL display panel per glass substrate is limited due to limitations in the manufacturing process. In addition, in the case of a large screen, the fall of the yield when a defect arises in a part of a screen cannot be avoided, and securing of in-plane uniformity is also difficult.

A technique developed as one of the solutions to the organic EL display device, which is difficult to form a large screen as described above, is a tiling technique, which is a method of forming one large panel by bonding several small EL display panels.

As described above, there is a problem due to the large area of the display panel, which is an increase in power consumption and a decrease in the life of the EL.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an organic electroluminescent display device and a driving method thereof, in which a luminance may be automatically changed according to an area emitted from a display panel.

An organic electroluminescent display device of the present invention for achieving the above object is a pixel portion having a plurality of pixels connected to a plurality of data lines, a plurality of scanning lines and a plurality of light emission control lines to display a predetermined image; A scan driver connected to the plurality of scan lines and configured to apply a scan signal for activating the plurality of pixels; A data driver connected to the plurality of data lines and applying a data signal to the activated pixels; An emission control driver connected to the plurality of emission control lines and configured to apply an emission control signal for controlling emission of pixels to which the data signal is applied; And a luminance adjusting unit configured to adjust a gamma reference voltage of the data driver or to apply a control signal for adjusting the emission duty of the emission control signal of the emission control driver according to an area where the plurality of pixels emit light.

The luminance controller includes a data counter for counting data amount during one frame by receiving red, green, and blue data and a vertical synchronization signal; A data adder for summing gray scales corresponding to the countered data; A memory for outputting luminance information stored in the form of a lookup table according to the sum value; And a gamma reference voltage controller configured to adjust a gamma reference voltage of the data driver based on luminance information output from the memory.

The luminance controller may include: a data counter configured to counter the amount of data during one frame by receiving red, green, and blue data and a vertical synchronization signal; A data adder for summing gray scales corresponding to the countered data; A memory for outputting luminance information stored in the form of a lookup table according to the sum value; And a data value controller for adjusting a data value of the data driver according to the luminance information output from the memory.

The luminance controller may include: a data counter configured to counter the amount of data during one frame by receiving red, green, and blue data and a vertical synchronization signal; A data adder for summing gray scales corresponding to the countered data; A memory for outputting luminance information stored in the form of a lookup table according to the sum value; And a light emission duty controller for adjusting the light emission duty of the light emission control signal of the light emission control driver in accordance with the luminance information output from the memory.

The purpose is to counter the data of each pixel applied; Summing up the gray scale of each of the countered data; Outputting luminance information corresponding to the summed value; And adjusting the gamma reference voltage according to the luminance information.

In addition, the method of driving the organic electroluminescent display device of the present invention for achieving the above object comprises the steps of: counter the data of each pixel applied; Summing up the gray scale of each of the countered data; Outputting luminance information corresponding to the summed value; And adjusting a data value according to the luminance information.

In addition, the method of driving the organic electroluminescent display device of the present invention for achieving the above object comprises the steps of: counter the data of each pixel applied; Summing up the gray scale of each of the countered data; Outputting luminance information corresponding to the summed value; And adjusting the light emission duty of the light emission control signal according to the brightness information.

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

First embodiment

1 is a block diagram illustrating an organic light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 1, an organic EL display device according to an exemplary embodiment of the present invention includes an EL display panel 10, a data driver 20, and a brightness controller 30.

The EL display panel 10 is composed of a pixel portion 12, a scan driver 14, and a light emission control driver 16. The thin film transistors of a plurality of pixels formed in the EL display panel 10 have polysilicon as a channel of the thin film transistors for fast response speed and uniformity. In this case, the polysilicon is formed on the glass substrate, and then crystallized into polysilicon through a low temperature polysilicon (LTPS) process.

A plurality of transistors are formed using polysilicon formed by the LTPS process, and the pixel unit 12 and the respective pixels are selected in the EL display panel 10 by using the plurality of transistors to control light emission. The scan driver 14 and the light emission control driver 16 which generate signals are formed.

The pixel unit 12 includes a plurality of data lines D1 -Dm, a plurality of scan lines S1 -Sn, a plurality of light emission control lines E1 -En, and a plurality of pixels P11 through which the lines intersect. Pnm).

The plurality of data lines D1 to Dm are electrically connected to the data driver 20 to extend in the vertical direction, and transmit data signals to the pixels.

In addition, although the plurality of scan lines S1 -Sn and the plurality of emission control lines E1 -En extend in the vertical direction like the data driver 20 unlike the conventional art, the same scan and In order to transmit the emission control signal, a contact hole is formed for each scan and emission control line S1 -Sn and E1 -En. Therefore, the metal wiring connected through the contact hole extends in the horizontal direction to transmit the scan and emission control signals to the pixels in the horizontal direction.

Each of the pixels P11 to Pnm has three red, green, and blue pixels arranged in rows and columns repeatedly. Each of the red, green, and blue pixels differs only from the organic material of the organic light emitting layer that actually emits light, and the wiring layout and the circuit connection relationship of the driving circuit unit are the same. Therefore, red, green, and blue light are emitted at luminance corresponding to the data signal applied to each pixel, and one color is expressed by a combination of these three colors.

The scan driver 14 is connected to the plurality of scan lines S1 -Sn, and sequentially selects the pixels P11 -Pnm by sequentially applying a scan signal to the pixel unit 12.

The emission control driver 16 is connected to the plurality of emission control lines E1-En to sequentially apply an emission control signal to the pixel unit 12 to control the emission time of each pixel P11 -Pnm. .

As described above, the data driver 20 supplies a data signal to the pixel portion 12 of the EL display panel 10 through a plurality of conductive lines provided on the flexible film. The data driver 20 is designed as an external integrated circuit (IC) using a CMOS forming technology and is electrically connected to each of the EL display panels 10. Electrical connection between one EL display panel 10 and data driver 20 is achieved through a metal pattern printed on the flexible film. That is, the output terminal of the data driver 20 is electrically connected to one end of the metal pattern, and the data line provided on the EL display panel 10 is electrically connected to the other end of the metal pattern. This is called a tape carrier package (TCP) method. Each data driver 20 supplies a data signal to the pixel portion of the EL display panel 10 through a plurality of conductive lines provided on the flexible film.

The brightness controller 30 applies a gamma reference voltage control signal to the data driver 20 or a light emission duty control signal to the light emission control driver 16 according to a data value applied for one frame. Accordingly, the luminance controller 30 adjusts the gamma reference voltage of the data driver 20 or the duty ratio of the emission control signal output from the emission control driver 16 according to the area of light emitted. You can adjust the (Duty Ratio) to automatically adjust the brightness dynamically.

In order to automatically adjust the luminance according to the light emitting area as above, the designer needs to set the desired luminance per the emitting area and store it in the memory.
As used herein, the term "light emitting area" to "light emitting area" refers to an area in the display panel that substantially emits light.

2 is a graph illustrating a relationship between a light emitting area and a luminance of an organic electroluminescent display according to a first exemplary embodiment of the present invention.

Referring to FIG. 2, the horizontal axis represents the area of light emitted from the pixel portion 12 of the display panel 10, and the unit is [%], and the vertical axis represents the luminance per emission area, and the unit is [cd / m. ² ].

In the case of FIG. 2, the luminance is set to decrease from 1000 [cd / m ² ] to 500 [cd / m ² ] as the emission area increases from 0 [%] to 100 [%]. The light emitting area can calculate the light emitting area (%) at which the pixels are turned on by detecting and counting data applied to the brightness controller 30 and counting the data amount for one frame. According to the graph of FIG. 2, a look up table is prepared and stored in a memory. Therefore, the power consumption can be limited by adjusting the luminance according to the light emitting area. The luminance set in FIG. 2 is only one embodiment, and may be set to various luminance according to the designer.

3 is a block diagram illustrating a brightness controller of an organic light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 3, the luminance controller 30 according to the first embodiment is a data counter 31, a data adder 33, a memory 35, and a gamma reference voltage controller 37. It is composed.

The data counter 31 receives R, G, and B data and a vertical synchronization signal Vsync to counter R, G, and B data for one frame. For example, when each of R, G, and B data consisting of 6 bits is applied to emit the entire pixel portion 12 having a resolution of 3 * 3 (R, G, B) * 2, the data counter ( 31) counters 3 * 3 (R, G, B) * 2 * 2 ^ 6 data for one frame.

The data adder 33 calculates gray scales for each of the R, G, and B pixels counted by the data counter 31, and adds the values together.

When the light emitting area is calculated by counting the R, G, and B data applied for one frame as described above, and the respective gray scales of the light emitting pixels are summed, the total gray scale corresponding to the light emitting area can be known.

The memory 35 stores data in the form of a look up table to display luminance corresponding to a graph curve according to the emission area as shown in FIG. 2. That is, the luminance information is stored so that the light emitting area is inversely proportional to the luminance. The memory 35 receives the summed grayscale value and outputs a corresponding control signal by referring to a look up table previously stored according to the value.

The gamma reference voltage controller 37 receives a control signal output from the memory 35 to adjust the gamma reference voltage, and outputs the adjusted gamma reference voltage to the digital-to-analog converter (DAC) of the data driver 20. do. As the emission area increases, the gamma reference voltage is increased to decrease the luminance. On the contrary, as the emission area is smaller, the gamma reference voltage is lowered to increase the luminance. Here, the minimum luminance is preferably 1/2 or more of the maximum luminance in consideration of the contrast ratio.

By providing the brightness controller 30 according to the embodiment of the present invention as described above, the R, G, B data applied to the data driver 20 is the gamma reference voltage adjusted by the gamma reference voltage controller 37 The analog signal corresponding to the signal is applied to each of the R, G, and B pixels. Therefore, the brightness desired by the designer can be expressed according to the light emitting area.

The operation of the brightness controller 30 as described above will be described. First, the resolution of the pixel is 3 * 3 (R, G, B) * 2, and the R, G, B data is 6 bits.

First, when 6-bit R, G, B digital data is applied to the data counter 31, the data counter 31 counters each R, G, B data for one frame. The data adder 33 adds up the gray scale corresponding to the countered data.

The memory 35 that stores information corresponding to the light emitting area and the brightness in advance receives the sum of the gray scale values and applies a control signal corresponding to the values to the gamma reference voltage controller 37. The gamma reference voltage controller 37 adjusts the gamma reference voltage of the digital-analog converter of the data driver 20 according to the input control signal.

Second embodiment

4 is a block diagram illustrating a brightness controller of an organic light emitting display device according to a second embodiment of the present invention.

In this embodiment, the configuration of the organic electroluminescent display is the same as that shown in the first embodiment. Therefore, the organic electroluminescent display device applied to the present embodiment is the same as that of FIG. 1, and the connection relations and operations of the components shown in FIG. 1 are avoided to avoid overlapping descriptions and are omitted for easy understanding of the present invention. . However, in the present embodiment, the configuration and operation of the luminance adjusting unit shown in FIG. 1 have a luminance adjusting unit different from that of FIG. 3 of the first embodiment.

Referring to FIG. 4, the luminance controller 30 according to the first embodiment includes a data counter 31 ′, a data adder 33 ′, a memory 35 ′, and a data value adjuster 37. ').

The data counter 31 ′ receives R, G, and B data and a vertical synchronization signal Vsync to counter R, G, and B data for one frame. For example, when each of R, G, and B data consisting of 6 bits is applied to emit the entire pixel portion 12 having a resolution of 3 * 3 (R, G, B) * 2, the data counter ( 31 ') counters 3 * 3 (R, G, B) * 2 * 2 ^ 6 data for one frame.

The data adder 33 'calculates a gray scale for each of the R, G, and B pixels counted by the data counter 31', and adds the values together.

When the light emitting area is calculated by counting the R, G, and B data applied for one frame as described above, and the respective gray scales of the light emitting pixels are summed, the total gray scale corresponding to the light emitting area can be known.

The memory 35 'stores data in the form of a look up table in advance so as to display luminance corresponding to a graph curve according to the emission area as shown in FIG. That is, the luminance information is stored so that the light emitting area is inversely proportional to the luminance. The memory 35 'receives the summed grayscale value and outputs a corresponding control signal with reference to a look up table previously stored according to the value.

The data value controller 37 ′ receives a control signal output from the memory 35, corrects the data value, and outputs the corrected data value to the digital-to-analog converter (DAC) of the data driver 20. As the light emitting area increases, the luminance increases by increasing the data value. On the contrary, as the light emitting area decreases, the luminance decreases by increasing the data value. Here, the minimum luminance is preferably 1/2 or more of the maximum luminance in consideration of the contrast ratio.

By providing the brightness controller 30 according to the embodiment of the present invention as described above, the R, G, B data applied to the data driver 20 is adjusted by the data value controller 37 'and each R, G Is applied to the B pixel. Therefore, the brightness desired by the designer can be expressed according to the light emitting area.

The operation of the brightness controller 30 as described above will be described. First, the resolution of the pixel is 3 * 3 (R, G, B) * 2, and the R, G, B data is 6 bits.

First, when 6-bit R, G, B digital data is applied to the data counter 31 ', the data counter 31' counters each R, G, B data for one frame. The data adder 33 'adds up the gray scale corresponding to the countered data.

The memory 35 ', which stores information corresponding to the light emitting area and the brightness in advance, receives the summed gray scale value and applies a control signal corresponding to the value to the data value controller 37'. The data value controller 37 'adjusts the data value applied to the data driver 20 according to the input control signal and applies the adjusted data value to each pixel.

Third embodiment

5 is a block diagram illustrating a brightness controller of an organic light emitting display device according to a third embodiment of the present invention.

In this embodiment, the configuration of the organic electroluminescent display is the same as that shown in the first embodiment. Therefore, the organic electroluminescent display device applied to the present embodiment is the same as that of FIG. 1, and the connection relations and operations of the components shown in FIG. 1 are omitted to avoid repeated descriptions and for easy understanding of the present invention. . However, in the present embodiment, the configuration and operation of the luminance adjusting unit shown in FIG. 1 have a luminance adjusting unit different from that of FIG. 3 of the first embodiment.

Referring to FIG. 5, the brightness controller 30 includes a data counter 32, a data adder 34, a memory 36, and a light duty controller 38.

The data counter 32 receives R, G, and B data and a vertical synchronization signal Vsync to counter R, G, and B data for one frame. For example, when each of R, G, and B data consisting of 6 bits is applied to emit the entire pixel portion 12 having a resolution of 3 * 3 (R, G, B) * 2, the data counter ( 32) counters 3 * 3 (R, G, B) * 2 * 2 ^ 6 data for one frame.

The data adder 34 calculates gray scales for each of the R, G, and B pixels countered by the data counter 32, and sums all of the values.

When the light emitting area is calculated by counting the R, G, and B data applied for one frame as described above, and the respective gray scales of the light emitting pixels are summed, the total gray scale corresponding to the light emitting area can be known.

The memory 36 stores data in the form of a look up table in advance so as to display luminance corresponding to a graph curve according to the emission area as shown in FIG. 2. That is, the luminance information is stored so that the light emitting area is inversely proportional to the luminance. The memory 36 receives the summed grayscale value and outputs a corresponding control signal by referring to a look up table stored in advance according to the value.

The light emission duty controller 38 receives a control signal output from the memory 36 and outputs a signal for adjusting the light emission duty to the light emission control driver 16. As the light emission area increases, the light emission duty of the light emission control signal is reduced to decrease the brightness. On the contrary, as the light emission area decreases, the light emission duty of the light emission control signal is increased to increase the brightness. Here, the minimum luminance is preferably 1/2 or more of the maximum luminance in consideration of the contrast ratio.

The operation of the brightness adjusting unit 30 according to the second embodiment of the present invention as described above will be described. First, the resolution of the pixel portion is 3 * 3 (R, G, B) * 2, and the R, G, B data is 6 bits.

First, when 6-bit R, G, B digital data is applied to the data counter 32, the data counter 32 counters each R, G, B data for one frame. Next, the data adder 34 adds up the gray scale corresponding to the countered data.

The memory 36, which stores information corresponding to the light emitting area and the brightness in advance, receives the summed gray scale value and applies a control signal corresponding to the value to the light emission duty controller 38. The light emission duty controller 38 adjusts the duty ratio of the light emission control signal by applying the light emission duty control signal to the light emission control driver 16 according to the input control signal.

The duty ratio of the emission control signal is adjusted in accordance with the luminance adjusting unit 30 shown in FIG. 5 with reference to the pixel circuit and the signal timing diagram applied to the pixel circuit.

6 is a circuit diagram illustrating a representative pixel of an organic electroluminescent display device according to a first embodiment, a second embodiment, and a third embodiment of the present invention.

Referring to FIG. 6, the pixel circuit 18 includes a pixel driver 19 and an organic EL element OLED.

The pixel driver 19 is connected to the data line Dm, the previous scan line Sn-1, the current scan line Sn, the emission control line En, the first power voltage line VDD, and the second power voltage line Vsus. It is. Therefore, a driving current corresponding to the data signal Vdata signal is supplied from the data line Dm to the organic EL element OLED.

The organic EL element OLED is composed of an anode electrode, a cathode electrode and an organic light emitting layer. An anode electrode is connected to the pixel driver 19, and a cathode electrode is connected to a reference power supply voltage line VSS. Therefore, the organic EL element OLED receives the driving current supplied from the pixel driver 19 and emits light with the luminance corresponding to the current amount.

The pixel driver 19 includes five transistors M1-M5 and two capacitors Cst and Cvth. The pixel driver 19 will be described in detail as follows.

The first electrode of the switching transistor M1 is connected with the data line Dm, and the gate terminal is connected with the scan line Sn. In addition, the switching transistor M1 is turned on to the scan signal transmitted through the scan line Sn to transfer the data signal Vdata from the data line Dm through the second electrode to the two capacitors Cst and Cvth. To pass).

The first electrode of the driving transistor M2 is connected to the first power supply voltage line VDD and generates a driving current I _OLED corresponding to a voltage applied to the gate terminal.

The threshold voltage compensating transistor M3 is connected between the gate terminal of the driving transistor M2 and the second electrode, and is turned on by a scan signal applied to a gate terminal connected to a previous scan line Sn- 1 so that the driving transistor is turned on. Compensate for the moon turn voltage at (M2).

The first capacitor Cvth is connected between the second electrode of the switching transistor M1 and the gate terminal of the driving transistor M2 to store the threshold voltage Vth of the driving transistor M2.

The second capacitor Cst is connected between the first power voltage line VDD and one end of the first capacitor and stores the data voltage Vdata transferred to the data line Dm.

In the second power supply voltage applying transistor M4, a first electrode is connected to the second power supply voltage line Vsus, and a second electrode is commonly connected to the first capacitor Cvth and the second capacitor Cst. The second power supply voltage applying transistor M4 is turned on to the previous scan signal Sn- 1 applied to the gate terminal to convert the second power supply voltage Vsus to the first capacitor Cvth and the second capacitor Cst. ) Is applied.

The emission control transistor M5 is connected between the second electrode of the driving transistor M1 and the anode electrode of the organic EL element OLED, and is turned on / off under the control of the emission control signal En applied to the gate terminal. The off operation is performed to supply or to block the driving current supplied from the driving transistor M1 to the organic EL element OLED.

The pixel circuit is only one embodiment, and all pixel circuits having light emission control transistors are included in the scope of the present invention.

Hereinafter, the operation of the pixel circuit 18 will be described.

First, when the low level previous scan signal Sn-1 is applied to the pixel circuit 18 and the high level current scan signal Sn and the emission control signal En are applied, the threshold voltage compensation transistor M3 is applied. ) And the second power supply transistor M3 are turned on, and the remaining transistors M1 and M5 are turned off. Accordingly, the driving transistor M2 is diode-connected to apply the voltage VDD-| Vth | [V] to one electrode B of the first capacitor Cvth, and the second power supply voltage applying transistor M4 is turned on to form the first voltage. The voltage Vsus [V] is applied to the other electrode A of the one capacitor Cvth. Therefore, the voltage of Vsus-VDD + | Vth | [V] is stored in the first capacitor Cvth.

Next, when the current scan signal Sn having a low level is applied to the pixel circuit 18 and the previous scan signal Sn-1 and the light emission control signal En having a high level are applied, the switching transistor M1. Only turns on. At this time, the data voltage Vdata from the data line Dm is applied to the other electrode A of the first capacitor Cvth through the switching transistor M1. Accordingly, the other electrode A of the first capacitor Cvth generates a voltage variation ΔV = Vsus-Vdata by a predetermined voltage difference, and accordingly, one electrode B of the first capacitor Cvth has the same amount. Will cause voltage fluctuations. Therefore, the voltage applied to the first electrode B of the first capacitor and the gate terminal of the driving transistor M1 is VDD-| Vth |-? V = VDD-| Vth | -Vsus + Vdata [v].

Finally, when the previous scan signal Sn-1 and the current scan signal Sn of a high level are applied to the pixel circuit 18, and the emission control signal En of a low level is applied, the emission control transistor M5. ) Is only turned on. In this case, the driving current I _OLED output from the driving transistor M2 is shown in Equation 1 below.

I _OLED = k (Vsg-| Vth |) ² = k {VDD-(VDD- | Vth |-Vsus + Vdata)-| Vth |} ²

= k (Vsus-Vdata) ²

Here, Vth is the threshold voltage of the driving transistor M2, and k is a constant.

As shown in Equation 1, the pixel circuit 18 illustrated in FIG. 3 may exclude the influence of the voltage drop due to the threshold voltage Vth compensation and the first power supply voltage VDD.

The pixel circuit of the above operation has been described with respect to the general scanning signal and the emission control signal.

A change in the duty ratio of the emission control signal when the luminance controller 30 according to the third embodiment of the present invention is operated will be described with reference to FIG. 7.

FIG. 7 is a timing diagram of light emission control signals having different light emission duty according to the light emitting area when the brightness controller shown in FIG. 5 is operated.

Referring to FIG. 7, when the previous scan signal Sn−1 and the current scan signal Sn are applied for one frame, an emission control signal having a different duty ratio according to each luminance value is illustrated. That is, the light emission control signal En which the pixels emit light 100%, the light emission control signal En 'that the pixels emit light 75%, and the light emission control signal En " ) Is shown.

First, the emission control signal En having the emission duty 100% represents a case where the emission area of the R, G, and B data of one frame applied to the brightness controller 30 is small. For example, when the light emitting area is about 20%, the light emission control signal En is converted to a low level immediately after the scan signal Sn to turn on the light emission control transistor M5 to emit light for almost one frame, thereby achieving high luminance. To indicate.

Next, the light emission control signal En 'having a light emission duty of 75% represents a case where the light emission area of the R, G, and B data of one frame applied to the brightness controller 30 is about medium. For example, when the emission area is about 50%, the emission control signal En 'is converted to a low level after a predetermined time after the scan signal Sn to turn on the emission control transistor M5 to turn on the emission control transistor M5 to about 75 of one frame. Luminance is reduced by about 25% by emitting only%.

 Next, the emission control signal En ″ having the emission duty of 50% shows a case where the emission area of the R, G, and B data of one frame applied to the brightness controller 30 is large. For example, when the emission area is about 100%, only about 50% of the emission control signal En ″ is converted to the low level, thereby reducing the luminance by about half.

 As described above, the brightness controller 30 according to the third embodiment of the present invention adjusts the light emission duty of the light emission control signal En to adjust the brightness according to the light emission area.

However, in the process of adjusting the light emission duty of the light emission control signal En, flicker may occur.

FIG. 8 is a timing diagram illustrating a light emission control signal having a multi light emission duty according to the luminance adjuster illustrated in FIG. 5.

Referring to FIG. 8, the emission control signal En ″ ′ has a light emission duty of 75% and has the same emission duty as that of the emission control signal En ′ of FIG. 7. The signal En "'has a light emission duty of about 25% three times in one frame. Here, the number of emission duty of the emission control signal is not fixed, and any one having at least two times (hereinafter, referred to as "multi-emission duty") during one frame may be included. As described above, the flickering phenomenon that may be generated in the emission control signal En ′ illustrated in FIG. 7 may be prevented by having the multi emission duty.

As described above, by adjusting the gamma reference voltage or data value of the data driver or adjusting the emission duty of the emission control signal, including the luminance controller of the organic light emitting display device according to the embodiments of the present invention, You can adjust the brightness accordingly.

The present invention can improve the contrast ratio by adjusting the luminance according to the light emitting area, and by adjusting the light emitting duty of the light emitting control signal for adjusting the brightness, the power consumption can be reduced by limiting the driving current. In addition, it is possible to increase the life of the organic EL due to the reduced power consumption.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the following specific claims. I can understand that you can.

The present invention can improve the contrast ratio by adjusting the luminance according to the light emitting area.

In addition, by adjusting the light emission duty of the light emission control signal, the power consumption can be reduced by limiting the driving current.

In addition, it is possible to increase the life of the organic EL due to the reduced power consumption.

Claims (27)

A pixel portion having a plurality of pixels connected to a plurality of data lines, a plurality of scan lines, and a plurality of light emission control lines to display a predetermined image; A scan driver connected to the plurality of scan lines and configured to apply a scan signal for activating the plurality of pixels; A data driver connected to the plurality of data lines and applying a data signal to the activated pixels; An emission control driver connected to the plurality of emission control lines and configured to apply an emission control signal for controlling emission of pixels to which the data signal is applied; And And a luminance controller configured to adjust a gamma reference voltage or a data value of the data driver or an emission duty of an emission control signal of the emission control driver according to an area at which the plurality of pixels emit light. The method of claim 1, The brightness control unit, A data counter which receives red, green and blue data and a vertical synchronization signal and counts the amount of data for one frame; A data adder for summing gray scales corresponding to the countered data; A memory for outputting luminance information stored in the form of a lookup table according to the sum value; And And a gamma reference voltage controller configured to adjust the gamma reference voltage of the data driver in accordance with the luminance information output from the memory. The method of claim 2, The memory, An organic electroluminescence display device for storing luminance information such that the emission area is inversely proportional to the luminance. The method of claim 3, wherein The gamma reference voltage controller, An organic electroluminescent display device characterized by increasing a gamma reference voltage as the emission area increases. The method of claim 4, wherein The gamma reference voltage controller, And a gamma reference voltage is controlled such that the luminance of the maximum light emitting area of the pixel portion is equal to or greater than 1/2 of the luminance of the minimum light emitting area. The method of claim 1, The brightness control unit, A data counter which receives red, green and blue data and a vertical synchronization signal and counts the amount of data for one frame; A data adder for summing gray scales corresponding to the countered data; A memory for outputting luminance information stored in the form of a lookup table according to the sum value; And And a data value adjuster for adjusting a data value of the data driver in accordance with the luminance information output from the memory. The method of claim 6, The memory, An organic electroluminescence display device for storing luminance information such that the emission area is inversely proportional to the luminance. The method of claim 7, wherein The data value controller, An organic electroluminescent display device characterized by increasing the data value as the light emitting area increases. The method of claim 8, The data value controller, And the data value is adjusted such that the luminance of the maximum light emitting area of the pixel portion is equal to or greater than 1/2 of the luminance of the minimum light emitting area. The method of claim 1, The brightness control unit, A data counter which receives red, green and blue data and a vertical synchronization signal and counts the amount of data for one frame; A data adder for summing gray scales corresponding to the countered data; A memory for outputting luminance information stored in the form of a lookup table according to the sum value; And And a light emission duty controller for adjusting the light emission duty of the light emission control signal of the light emission control driver in accordance with the luminance information output from the memory. The method of claim 10, The memory, An organic electroluminescence display device for storing luminance information such that the emission area is inversely proportional to the luminance. The method of claim 11, The light emission duty controller, And an emission duty of the emission control signal is reduced as the emission area increases. The method of claim 12, The light emission duty controller, And at least two or more emission duty cycles of the emission control signal during one frame. The method of claim 13, The light emission duty controller, And the light emission duty is controlled so that the luminance of the maximum light emitting area of the pixel portion is equal to or greater than 1/2 of the luminance of the minimum light emitting area. Counting data of respective pixels applied; Summing up the gray scale of each of the countered data; Outputting luminance information corresponding to the summed value; And And adjusting a gamma reference voltage according to the luminance information. The method of claim 15, And the luminance information is set such that the light emitting area and the luminance are inversely proportional to each other. The method of claim 16, And the gamma reference voltage increases as the emission area increases. The method of claim 17, And the gamma reference voltage is adjusted such that the brightness of the maximum light emitting area of the pixel portion is equal to or greater than 1/2 of the brightness of the minimum light emitting area. Counting data of respective pixels applied; Summing up the gray scale of each of the countered data; Outputting luminance information corresponding to the summed value; And And adjusting a data value according to the luminance information. The method of claim 19, And the luminance information is set such that the light emitting area and the luminance are inversely proportional to each other. The method of claim 20, And the data value increases as the emission area increases. The method of claim 21, And the data value is adjusted such that the luminance of the maximum light emitting area of the pixel portion is equal to or greater than 1/2 of the luminance of the minimum light emitting area. Counting data of respective pixels applied; Summing up the gray scale of each of the countered data; Outputting luminance information corresponding to the summed value; And And adjusting the light emission duty of the light emission control signal according to the brightness information. The method of claim 23, And the luminance information is set such that the light emitting area and the luminance are inversely proportional to each other. The method of claim 24, And a light emission duty of the light emission control signal decreases as the light emission area increases. The method of claim 25, And a light emission duty of the light emission control signal is generated at least twice during one frame. The method of claim 26, And a light emission duty of the light emission control signal is adjusted such that the brightness of the maximum light emitting area of the pixel portion is equal to or greater than 1/2 of the brightness of the minimum light emitting area.

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