KR100646989B1 - Organic light emitting display and driving method thereof - Google Patents

Abstract

An organic light emitting display device and a driving method thereof are provided to display a uniform image regardless of threshold voltages of transistors formed in each pixel. An organic light emitting display device for driving one frame according to an initialization period, a threshold voltage compensation period, a data write period, and an emission period includes a pixel unit having pixels(140) connected to scan lines(Sn), first and second control lines(CL1,CL2), an emission control line(E), and data lines(Dm); a scan driving unit driving the scan lines formed by a unit of horizontal line and the first and second control lines and the emission control line connected to all pixels in common; and a data driving unit supplying a data signal to the data lines. The pixels emit the light correspondingly to the data signal only during the emission period and do not emit the light during the other periods except for the emission period.

Description

Organic Light Emitting Display and Driving Method Thereof}

1 illustrates a conventional organic light emitting display device.

2 is a diagram illustrating an organic light emitting display device according to an exemplary embodiment of the present invention.

3 is a waveform diagram showing a driving waveform supplied during one frame period in the present invention.

FIG. 4 is a circuit diagram illustrating a first embodiment of the pixel illustrated in FIG. 2.

5A through 5D are diagrams illustrating transistors turned on by the driving waveform shown in FIG. 3.

FIG. 6 is a circuit diagram illustrating a second embodiment of the pixel illustrated in FIG. 2.

FIG. 7 is a circuit diagram illustrating a third embodiment of the pixel illustrated in FIG. 2.

FIG. 8 is a waveform diagram illustrating a driving waveform for driving the pixel illustrated in FIG. 7.

<Explanation of symbols for main parts of the drawings>

10,110: scan driver 20,120: data driver

30,130: pixel portion 40,140: pixel

50,150: timing controller 142,144,146: pixel circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display and a driving method thereof, and more particularly, to an organic light emitting display and a driving method thereof capable of displaying an image of uniform luminance.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. The flat panel display includes a liquid crystal display, a field emission display, a plasma display panel, and an organic light emitting display.

Among flat panel displays, an organic light emitting display displays an image using an organic light emitting diode that generates light by recombination of electrons and holes. Such an organic light emitting diode display has advantages in that it has a fast response speed and is driven with low power consumption. In general, an organic light emitting diode display generates light in an organic light emitting diode by supplying a current corresponding to the data signal to the organic light emitting diode using a transistor formed for each pixel.

1 illustrates a conventional organic light emitting display device.

Referring to FIG. 1, a conventional organic light emitting display device includes a pixel portion 30 including pixels 40 formed at an intersection area of scan lines S1 to Sn and data lines D1 to Dm, and a scan line. For controlling the scans S1 to Sn, the data driver 20 for driving the data lines D1 to Dm, the scan driver 10 and the data driver 20 for controlling the scan drivers 10 and Sn. The timing control part 50 is provided.

The scan driver 10 generates a scan signal in response to the scan drive control signals SCS from the timing controller 50, and sequentially supplies the generated scan signal to the scan lines S1 to Sn.

The data driver 20 generates data signals in response to the data driving control signals DCS from the timing controller 50, and supplies the generated data signals to the data lines D1 to Dm. In this case, the data driver 20 supplies data signals of one horizontal line to the data lines D1 to Dm every one horizontal period.

The timing controller 50 generates a data drive control signal DCS and a scan drive control signal SCS in response to the synchronization signals supplied from the outside. The data drive control signal DCS generated by the timing controller 50 is supplied to the data driver 20, and the scan drive control signal SCS is supplied to the scan driver 10. The timing controller 50 rearranges the data Data supplied from the outside and supplies the data to the data driver 20.

The pixel unit 30 receives the first power source ELVDD and the second power source ELVSS from the outside. Here, the first power source ELVDD and the second power source ELVSS are supplied to the respective pixels 40. Each of the pixels 40 supplied with the first power source ELVDD and the second power source ELVSS displays an image in response to a data signal.

However, in the conventional organic light emitting display device, the pixels 40 positioned on the remaining horizontal lines emit light while the data signal is written to the pixels 40 positioned on a specific horizontal line. As such, when the pixels 40 positioned on the remaining horizontal lines emit light while the data signals are written to the pixels 40 positioned on the specific horizontal line, a voltage drop occurs in the first power supply ELVDD. This causes a problem in that a uniform image cannot be displayed.

In the conventional organic light emitting diode display, the voltage drop voltage of the first power source ELVDD is set differently according to whether the interframe pixels 40 emit light, thereby displaying a more non-uniform image. For example, a high load is applied to the first power supply ELVDD in a frame in which the pixels 40 emit light, and a low load is applied to the first power supply ELVDD in a frame in which the pixels 40 emit light. do.

In addition, in the conventional organic light emitting diode display, the threshold voltages of the transistors included in each of the pixels 40 are set differently due to a process deviation or the like. As such, when the threshold voltages of the transistors included in each of the pixels 40 are set differently, an image of uniform luminance cannot be displayed.

Accordingly, an object of the present invention is to provide an organic light emitting display device and a driving method thereof capable of displaying an image of uniform luminance.

In order to achieve the above object, the first aspect of the present invention comprises: a pixel portion having pixels connected to a scanning line, a first control line, a second control line, a light emission control line, and a data line; A scan driver configured to drive scan lines formed in horizontal line units, and the first control line, the second control line, and the light emission control line commonly connected to all pixels; A data driver for supplying a data signal to the data lines; The pixels may emit light in response to the data signal only during the light emitting period, and may not be lighted during other periods.

Preferably, each of the pixels includes an organic light emitting diode, and a cathode of the organic light emitting diode is connected to a second power source. The voltage value of the second power source is set to a first voltage during the initialization period, the threshold voltage compensation period, and a data writing period, and is set to a second voltage lower than the first voltage during the light emitting period. A first transistor connected to each of the data line and the scan line and turned on when the scan signal is supplied; The capacitor for charging a voltage corresponding to the data signal when the first transistor is turned on; The driving transistor for supplying a current corresponding to the voltage charged in the capacitor to the organic light emitting diode; A third transistor connected between the gate electrode and the second electrode of the driving transistor and turned on when the first control signal is supplied to a first control line; And a fourth transistor connected between the capacitor and the first power source and turned off when the emission control signal is supplied to the emission control line.

The second aspect of the present invention is a first step of initializing the gate electrode voltage of the driving transistor included in each of the pixels, the second step of charging the threshold voltage of the driving transistor in the capacitor included in each of the pixels, And a fourth step of additionally charging a voltage corresponding to the data signal to the capacitor, and a fourth step of emitting an organic light emitting diode in response to the voltage charged in the capacitor. Provide a method.

Preferably, the organic light emitting diode is set to a non-light emitting state during the first to third steps. The voltage value of the second power supply connected to the cathode electrode of the organic light emitting diode is set to a first voltage during the first to third steps, and to a second voltage lower than the first voltage during the fourth step. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 to 8 that can be easily implemented by those skilled in the art.

2 is a diagram illustrating an organic light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 2, an organic light emitting diode display according to an exemplary embodiment of the present invention may include scan lines S1 to Sn, data lines D1 to Dm, a first control line CL1, a second control line CL2, and the like. The pixel unit 130 including the pixels 140 connected to the emission control line E, the scan lines S1 to Sn, the first control line CL1, the second control line CL2, and the emission control A timing controller for controlling the scan driver 110 for driving the line E, the data driver 120 for driving the data lines D1 to Dm, the scan driver 110 and the data driver 120. 150.

The scan driver 110 controls the scan lines S1 to Sn, the first control line CL1, the second control line CL2, and the emission control in response to the scan drive control signals SCS from the timing controller 150. Drive line E. In fact, the scan driver 110 sequentially supplies the scan signals to the scan lines S1 to Sn during the data writing period included in one frame as shown in FIG. 3. The scan driver 110 supplies the second control signal to the second control line CL2 during the initialization period included in one frame, and the first control during the initialization period, threshold voltage compensation period, and data writing period included in one frame. The first control signal is supplied to the line CL1. In addition, the scan driver 110 supplies the light emission control signal to the light emission control line E during the data writing period.

Meanwhile, the first control line CL1, the second control line CL2, and the emission control line E are electrically connected to all the pixels included in the pixel unit 130. Therefore, the driving waveform supplied to the first control line CL1, the second control line CL2, and the emission control line E may be implemented by a simple circuit. For example, in the present invention, the first control line CL1, the second control line CL2, and the emission control line E may not be connected to the scan driver 110, but may be connected to a separate circuit additionally installed. .

The data driver 120 generates data signals in response to the data driving control signals DCS from the timing controller 150, and supplies the generated data signals to the data lines D1 to Dm during the data writing period. At this time, the data driver 120 supplies the data signal to the data lines D1 to Dm whenever the scan signal is supplied.

The timing controller 150 generates a data drive control signal DCS and a scan drive control signal SCS in response to external synchronization signals. The data driving control signal DCS generated by the timing controller 150 is supplied to the data driver 120, and the scan driving control signal SCS is supplied to the scan driver 110. The timing controller 150 rearranges the data Data supplied from the outside and supplies the data to the data driver 120.

The pixel unit 130 receives the first power source ELVDD and the second power source ELVSS from the outside. Here, the first power source ELVDD and the second power source ELVSS are supplied to the pixels 140. Each of the pixels 140 supplied with the first power supply ELVDD and the second power supply ELVSS displays a predetermined image during the light emission period in response to a data signal supplied in the data writing period. Here, the voltage of the second power supply ELVSS maintains a high voltage (first voltage) during the initialization period, the threshold voltage compensation period, and the data writing period included in one frame, as shown in FIG. The low voltage (second voltage) is maintained. As such, when the voltage of the second power supply ELVSS is maintained at the low voltage only during the light emitting period, the organic light emitting diode OLED emits light only during the light emitting period, thereby improving contrast.

4 is a diagram illustrating a first embodiment of the pixel illustrated in FIG. 2.

Referring to FIG. 4, the pixel 140 according to the first exemplary embodiment of the present invention includes an organic light emitting diode OLED and a pixel circuit 142 for supplying current to the organic light emitting diode OLED.

The anode electrode of the organic light emitting diode OLED is connected to the pixel circuit 142, and the cathode electrode is connected to the second power source ELVSS. Such an organic light emitting diode (OLED) generates light having a predetermined luminance in response to a current supplied from the pixel circuit 142 during the light emitting period, and light in other periods (initialization period, threshold voltage compensation period, data writing period). Does not generate To this end, the voltage value of the second power supply ELVSS is set to a low voltage during the light emitting period, and is set to a high voltage higher than the low voltage for other periods.

The pixel circuit 142 includes a first transistor M1 connected to the data line Dm and the scan line Sn, and a fourth transistor M4 connected between the first node N1 and the first power source ELVDD. And a capacitor C connected between the sixth transistor M6, the first node N1, and the second node N2, the second node N2, the sixth transistor M6, and the organic light emitting diode ( A second transistor M2 (or driving transistor) connected to the anode electrode of the OLED, a third transistor M3 connected between the second node N2 and the anode electrode of the organic light emitting diode OLED, and A fifth transistor M5 is connected between the third transistor M3 and the second control line CL2.

The first electrode of the first transistor M1 is connected to the data line Dm, and the gate electrode is connected to the scan line Sn. The second electrode of the first transistor M1 is connected to the first node N1. When the scan signal is supplied to the scan line Sn, the first transistor M1 is turned on to transfer the data signal supplied from the data line Dm to the first node N1. Here, the first electrode is set to any one of a source electrode and a drain electrode, and the second electrode is set to an electrode different from the first electrode. For example, when the first electrode is set as the source electrode, the second electrode is set as the drain electrode.

The gate electrode of the second transistor M2 is connected to the second node N2, and the first electrode is connected to the second electrode of the sixth transistor M6. The second electrode of the second transistor M2 is connected to the anode electrode of the organic light emitting diode OLED. The second transistor M2 controls the amount of current flowing to the organic light emitting diode OLED in response to the voltage value stored in the capacitor C. FIG.

The first electrode of the third transistor M3 is connected to the second electrode of the second transistor M2, and the second electrode is connected to the second node N2. The gate electrode of the third transistor M3 is connected to the first control line CL1. The third transistor M3 is turned on when the first control signal is supplied to connect the second transistor M2 in the form of a diode.

The first electrode of the fourth transistor M4 is connected to the second electrode of the sixth transistor M6, and the second electrode is connected to the first node N1. The gate electrode of the fourth transistor M4 is connected to the light emission control line E. The fourth transistor M4 is turned off when the light emission control signal is supplied, and is turned on for the other period. That is, the fourth transistor M4 is turned on during the initialization period, the threshold voltage compensation period, and the light emission period.

The first electrode of the fifth transistor M5 is connected to the second electrode of the third transistor M3, and the second electrode and the gate electrode are connected to the second control line CL2. The fifth transistor M5 is turned on when the second control signal is supplied.

The first electrode of the sixth transistor M6 is connected to the first power source ELVDD, and the second electrode is connected to the first electrode of the second transistor M2. The gate electrode of the sixth transistor M6 is connected to the light emission control line E. The sixth transistor M6 is turned off when the emission control signal is supplied, and is turned on for another period. That is, the sixth transistor M6 is turned on during the initialization period, the threshold voltage compensation period, and the light emission period.

The capacitor C charges a voltage corresponding to the threshold voltage of the second transistor M2 during the threshold voltage compensation period, and further charges a voltage corresponding to the data signal during the data writing period. The capacitor C supplies the voltage stored therein to the second transistor M2 during the light emission period so that light of a predetermined luminance is generated in the organic light emitting diode OLED.

3 and 4, the operation process will be described in detail. First, a first control signal and a second control signal are supplied during an initialization period. The voltage value of the second power supply ELVSS is maintained high so that the organic light emitting diode OLED does not emit light during the initialization period.

When the first control signal and the second control signal are supplied, the third transistor M3 and the fifth transistor M5 are turned on as shown in FIG. 5A. Since the light emission control signal is not supplied during the initialization period, the fourth transistor M4 and the sixth transistor M6 are turned on. When the third transistor M3 and the fifth transistor M5 are turned on, the anode electrode of the second node N2 and the organic light emitting diode OLED is connected to the second control line CL2. In this case, the anode electrode of the second node N2 and the organic light emitting diode OLED is converted (or initialized) to the voltage of the second control signal. In other words, the voltage value of the anode electrode of the second node N2 and the organic light emitting diode OLED included in all the pixels 140 is the voltage value of the second control signal regardless of the voltage value maintained in the previous frame. Is initialized to Here, the voltage value of the second control signal is a voltage value capable of turning on the fifth transistor M5 and is set lower than the voltage value of the first power supply ELVDD. On the other hand, since the voltage value of the second power supply ELVSS is maintained at a high voltage during the threshold voltage compensation period, the organic light emitting diode OLED may be prevented from being emitted by unnecessary current.

The first control signal is supplied in the gate voltage compensation period. The voltage value of the second power supply ELVSS is maintained high so that the organic light emitting diode OLED does not emit light during the threshold voltage compensation period.

When the first control signal is supplied, the third transistor M3 is turned on as shown in FIG. 5B. In addition, since the emission control signal is not supplied during the threshold voltage compensation period, the fourth transistor M4 and the sixth transistor M6 are turned on. When the third transistor M3 is turned on, the second transistor M2 is connected in the form of a diode. Here, since the sixth transistor M6 and the fourth transistor M4 are turned on, the voltage of the first node N1 is set to the voltage of the first power source ELVDD and the voltage of the second node N2. Is set to a value obtained by subtracting the threshold voltage of the second transistor M2 from the voltage of the first power source ELVDD.

That is, each of the capacitors C included in all the pixels 140 stores a voltage corresponding to the threshold voltage of the second transistor M2 during the threshold voltage compensation period. On the other hand, since the voltage value of the second power supply ELVSS is maintained at a high voltage during the threshold voltage compensation period, the organic light emitting diode OLED may be prevented from being emitted by unnecessary current.

During the data writing period, the scan signals are sequentially supplied to the first scan line S1 to the nth scan line Sn, and at the same time, the first control signal is supplied. Then, the light emission control signal is supplied during the data writing period. In addition, the voltage value of the second power supply ELVSS is maintained high so that the organic light emitting diode OLED does not emit light during the data writing period.

When the first control signal is supplied, as shown in FIG. 5C, the third transistor M3 included in each of the pixels 140 is turned on. When the emission control signal is supplied, the fourth transistor M4 and the sixth transistor M6 included in each of the pixels 140 are turned off. When the scan signal is supplied to the scan line Sn, the first transistor M1 is turned on.

When the first transistor M1 is turned on, the data signal supplied to the data line Dm is supplied to the first node N1. At this time, the voltage value of the second node N2 is set to a value obtained by subtracting the threshold voltage of the second transistor M2 from the voltage value of the first power source ELVDD.

C = Vdata-ELVDD + Vth

In Equation 1, Vdata represents a voltage value of a data signal, and Vth represents a threshold voltage of the second transistor M2. That is, during the data writing period, the capacitor C included in each of the pixels 140 is charged with a voltage corresponding to the data signal. Meanwhile, in the present invention, the organic light emitting diode OLED does not emit light during the data writing period. As such, when the organic light emitting diode OLED does not emit light during the data writing period, the voltage drop of the first power supply ELVDD can be prevented (that is, since no current flows), thereby providing a desired voltage to the capacitor C. You can charge it correctly.

In practice, the voltage drop of the first power supply ELVDD occurs because the pixels located in the remaining horizontal lines emit light during a period of charging the capacitor included in the pixels located in the specific horizontal line. It was difficult to charge the correct voltage corresponding to the data signal. However, in the present invention, since all the pixels 140 maintain the non-emission state during the data writing period, the capacitor included in each of the pixels 140 may be charged with the correct voltage corresponding to the data signal.

During the light emission period, the voltage of the second power supply ELVSS is switched to a low voltage (for example, a voltage lower than the first power supply ELVSS). Then, the supply of the light emission control signal is stopped.

When supply of the emission control signal is stopped, the fourth transistor M4 and the sixth transistor M6 are turned on as shown in FIG. 5D. When the fourth transistor M4 and the sixth transistor M6 are turned on, the first electrodes of the first node N1 and the second transistor M2 are connected to the first power source ELVDD. Then, the second transistor M2 supplies a current corresponding to the voltage value stored in the capacitor C from the first power supply ELVDD to the organic light emitting diode OLED, and accordingly, a predetermined luminance in the organic light emitting diode OLED. Light is generated. In fact, the current flowing in the second transistor M2 may be expressed as in Equation 2.

In Equation 2, I _M2 represents a current flowing to the second transistor M2. Referring to Equation 2, the current flowing to the second transistor M2 is independent of the threshold voltage of the second transistor M2. Therefore, in the present invention, a uniform image can be displayed regardless of the threshold voltage of the second transistor M2.

Meanwhile, since the plurality of pixels 140 emit light during the emission period, a predetermined voltage drop may occur in the first power supply ELVDD. However, even if a voltage drop occurs in the first power supply ELVDD, each pixel 140 may display an accurate image corresponding to the voltage value stored in the capacitor C. FIG. In detail, the voltage of the first power supply ELVDD in which the voltage drop occurs during the light emission period is supplied to the first node N1. At this time, the voltage of the second node (N2) is changed by the voltage of the voltage of the first node (N1) by the capacitor (C). Accordingly, the voltage charged in the capacitor C does not change during the light emission period, and accordingly, the present invention may display a uniform image.

In the present invention, the voltage of the second power supply ELVSS is kept high for the period except the light emission period. As such, when the voltage of the second power supply ELVSS is kept high, the organic light emitting diode OLED does not emit light due to unnecessary current for a period except for the light emission period, thereby improving contrast.

FIG. 6 is a diagram illustrating a second embodiment of the pixel illustrated in FIG. 2. 6, the same parts as in FIG. 4 are assigned the same reference numerals and detailed descriptions thereof will be omitted.

Referring to FIG. 6, a pixel according to a second embodiment of the present invention includes an organic light emitting diode OLED and a pixel circuit 144 for supplying current to the organic light emitting diode OLED.

When the pixel according to the second embodiment of the present invention is compared with the pixel of the first embodiment of the present invention shown in FIG. 4, the sixth transistor M6 is removed from the pixel according to the second embodiment of the present invention. As described above, even if the sixth transistor M6 is removed, the pixel according to the second embodiment of the present invention can be stably driven.

Referring to FIG. 3 and FIG. 6, the operation process will be briefly described. First, a first control signal and a second control signal are supplied during an initialization period so that a second node N2 and an organic light emitting diode OLED are included in all pixels. The voltage value of the anode electrode of is initialized to the voltage of the second control signal.

The first control signal is supplied during the threshold voltage compensation period, and a voltage corresponding to the threshold voltage of the second transistor M2 is stored in the capacitor C included in all the pixels 140.

Thereafter, the emission control signal is supplied during the data writing period and the scan signal is sequentially supplied to the scan lines S1 to Sn. Then, the first control signal is supplied during the data writing period.

When the emission control signal is supplied to the emission control line E, the fourth transistor M4 included in each of the pixels is turned off. When the first control signal is supplied, the third transistor M3 included in each of the pixels is turned on. In addition, the first transistor M1 included in the pixels is sequentially turned on by the sequentially supplied scan signals.

When the first transistor M1 is turned on, the data signal supplied to the data line Dm is supplied to the first node N1. At this time, the voltage value of the second node N2 is set to a value obtained by subtracting the threshold voltage of the second transistor M2 from the voltage value of the first power supply ELVDD. Is charged. On the other hand, since the voltage of the first power supply ELVDD is supplied to the first electrode of the second transistor M2, the voltage value of the second node N2 is stably at the voltage value of the first power supply ELVDD. The threshold voltage of M2 is maintained by subtracting the value.

During the light emission period, the voltage of the second power supply ELVSS is switched to the low voltage and the supply of the light emission control signal is stopped to turn on the fourth transistor M4. Then, a current corresponding to the voltage charged in the capacitor C is supplied to the organic light emitting diode OLED during the light emission period to generate light having a predetermined brightness.

FIG. 7 is a diagram illustrating a third embodiment of the pixel illustrated in FIG. 2. 7, the same parts as in FIG. 4 are assigned the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG. 7, a pixel according to a third embodiment of the present invention includes an organic light emitting diode OLED and a pixel circuit 146 for supplying current to the organic light emitting diode OLED.

When the pixel according to the third embodiment of the present invention is compared with the pixel of the first embodiment of the present invention shown in FIG. 4, the fifth transistor M5 is removed from the pixel according to the third embodiment of the present invention. That is, in the pixel according to the third exemplary embodiment of the present invention, the fifth transistor M5 for initializing the second node N2 is turned on during the initialization period. Meanwhile, in the present invention, as shown in FIG. 8 for initializing the second node N2 during the initialization period, the voltage value of the second power supply ELVSS is kept low during the initialization period.

Referring to FIGS. 7 and 8, the operation process will be described. First, the first control signal is supplied during the initialization period. The voltage of the second power supply ELVSS maintains a low voltage during the initialization period. Here, the low voltage of the second power supply ELVSS is set lower than the voltage of the data signal.

When the first control signal is supplied, the third transistor M3 is turned on. When the third transistor M3 is turned on, the second node N2 and the organic light emitting diode OLED are electrically connected to each other. At this time, when the voltage of the second power supply ELVSS connected to the cathode electrode of the organic light emitting diode OLED is maintained at a low voltage, the voltage value of the second node N2 is converted into the low voltage of the second power supply ELVSS. . In other words, the second node N2 holding the voltage corresponding to the data signal of the previous frame period during the initialization period is initialized to the low voltage of the second power supply ELVSS.

During the threshold voltage compensation period, the first control signal is supplied to turn on the third transistor M3 included in each of the pixels. Then, the voltage corresponding to the threshold voltage of the second transistor M2 is stored in the capacitor C included in each of the pixels 140. Meanwhile, the organic light emitting diode OLED is prevented from emitting unnecessary light while maintaining the high voltage of the second power supply ELVSS during the threshold voltage compensation period.

The light emission control signal is supplied during the data writing period to turn off the fourth transistor M4 and the sixth transistor M6. In addition, the scan signals are sequentially supplied to the scan lines S1 to Sn during the data writing period to sequentially turn on the first transistor M1 included in the pixels, and the first control signal is supplied to the third transistor. Transistor M3 is turned on.

When the scan signal is supplied to the nth scan line Sn and the first transistor M1 is turned on, the data signal supplied to the data line Dm is supplied to the first node N1. In this case, since the voltage of the second node N2 is set to a value obtained by subtracting the threshold voltage of the second transistor M2 from the voltage of the first power source ELVDD, the voltage of the capacitor C is charged. .

During the light emission period, the voltage of the second power supply ELVSS is switched to the low voltage and the supply of the light emission control signal is stopped to turn on the fourth transistor M4 and the sixth transistor M4. Then, a current corresponding to the voltage charged in the capacitor C is supplied to the organic light emitting diode OLED during the light emission period to generate light having a predetermined brightness.

The above detailed description and drawings are merely exemplary of the present invention, but are used only for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention as defined in the meaning or claims. Accordingly, those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical protection scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

As described above, according to the organic light emitting diode display and the driving method thereof, a uniform image may be displayed regardless of the threshold voltage of the transistor included in each pixel. In the present invention, one frame is driven by dividing the initialization period, the threshold voltage compensation period, the data writing period and the light emission period. Here, the contrast can be improved because the organic light emitting diode is set to the non-light emitting state for a period except for the light emitting period in which the pixels emit light. Further, since the data writing period and the light emitting period do not overlap with each other, a uniform image can be displayed regardless of the voltage drop of the first power supply.

Claims (19)

An organic light emitting display device in which one frame is driven by being divided into an initialization period, a threshold voltage compensation period, a data writing period, and an emission period; A pixel portion including pixels connected to the scan line, the first control line, the second control line, the light emission control line, and the data line; A scan driver configured to drive scan lines formed in horizontal line units, and the first control line, the second control line, and the light emission control line commonly connected to all pixels; A data driver for supplying a data signal to the data lines; And the pixels emit light in response to the data signal only during the light emitting period, and are not lighted during other periods. The method of claim 1, Each of the pixels includes an organic light emitting diode, and a cathode of the organic light emitting diode is connected to a second power source. The method of claim 2, Wherein the voltage value of the second power supply is set to a first voltage during the initialization period, the threshold voltage compensation period, and a data writing period, and is set to a second voltage lower than the first voltage during the light emission period. Light emitting display. The method of claim 3, wherein The first voltage is set to a voltage value so that no current flows to the organic light emitting diode, and the second voltage is set to a voltage value so that current can flow to the organic light emitting diode. The method of claim 2, The scan driver is included in each of the pixels to supply a first control signal to the first control line during the initialization period to control a gate electrode voltage of a driving transistor for supplying current to the organic light emitting diode. And a second control signal supplied to the second control line. The method of claim 5, And the scan driver supplies the second control signal during the threshold voltage compensation period so that the threshold voltage of the driving transistor can be charged in a capacitor included in each of the pixels. The method of claim 6, And the scan driver sequentially supplies a scan signal to the scan lines during the data writing period, and supplies a light emission control signal to the light emission control line. The method of claim 7, wherein And the data driver supplies a data signal to the data lines during the data writing period. The method of claim 8, And each of the pixels generates light corresponding to a data signal supplied during the data writing period during the light emitting period. The method of claim 9, Each of the pixels A first transistor connected to the data line and the scan line and turned on when the scan signal is supplied; The capacitor for charging a voltage corresponding to the data signal when the first transistor is turned on; The driving transistor for supplying a current corresponding to the voltage charged in the capacitor to the organic light emitting diode; A third transistor connected between the gate electrode and the second electrode of the driving transistor and turned on when the first control signal is supplied to a first control line; And a fourth transistor connected between the capacitor and the first power source and turned off when the emission control signal is supplied to the emission control line. The method of claim 10, And a fifth transistor connected between the second electrode of the third transistor and the second control line and turned on when the second control signal is supplied. The method of claim 11, And a sixth transistor connected between the common terminal of the second electrode of the fourth transistor and the first electrode of the driving transistor and the first power supply and turned off when the emission control signal is supplied. Device. The method of claim 12, And the third to sixth transistors are turned on during the initialization period so that the gate electrode of the driving transistor is lowered to the voltage of the second control signal. The method of claim 2, Wherein the voltage value of the second power supply is set to a first voltage during the threshold voltage compensation period and a data writing period, and is set to a second voltage lower than the first voltage during the initialization period and the light emission period. Light emitting display. The method of claim 14, And the driving transistor and the organic light emitting diode are electrically connected during the initialization period, and the gate electrode voltage of the driving transistor is changed to the second voltage value. A first step of initializing a gate electrode voltage of the driving transistor included in each of the pixels; Charging a threshold voltage of the driving transistor to a capacitor included in each of the pixels; A third step of additionally charging a voltage corresponding to the data signal to the capacitor; And driving the organic light emitting diode to emit light in response to the voltage charged in the capacitor. The method of claim 16, And the organic light emitting diode is set in a non-light emitting state during the first to third steps. The method of claim 17, The voltage value of the second power supply connected to the cathode electrode of the organic light emitting diode is set to a first voltage during the first to third steps, and to a second voltage lower than the first voltage during the fourth step. A method of driving an organic light emitting display device, characterized in that. The method of claim 17, The voltage value of the second power supply connected to the cathode electrode of the organic light emitting diode is set to the first voltage during the second and third steps, and the second voltage lower than the first voltage during the first and fourth steps. A method of driving an organic light emitting display device, characterized in that the voltage is set.

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