KR20150025395A - Organic light emitting display device and driving method thereof - Google Patents

Abstract

The present invention relates to an organic light emitting display device in order to display an image having desired brightness. The organic light emitting display device according to an embodiment of the present invention comprises: pixels disposed in a pixel unit; and a data driving unit to synchronize first current and second current from the pixels via data lines by corresponding to data from the outside. Each of the pixels is equipped with an organic light emitting diode; and a pixel circuit to store voltage corresponding to current difference between the first current and the second current synchronized via the data lines, and to supply current corresponding to the stored voltage to the organic light emitting diode.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic electroluminescence display device and an organic electroluminescence display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an organic light emitting display and a driving method thereof, and more particularly to an organic light emitting display capable of displaying an image with a desired luminance and a driving method thereof.

As the information technology is developed, the importance of the display device, which is a connection medium between the user and the information, is emphasized. In accordance with this, a flat panel display (LCD) such as a liquid crystal display (LCD), an organic light emitting display (OLED), and a plasma display panel (PDP) FPD) is increasing.

Among the flat panel display devices, the organic light emitting display device displays an image using an organic light emitting diode that generates light by recombination of electrons and holes, and has advantages of fast response speed and low power consumption .

An organic light emitting display includes a plurality of pixels arranged in a matrix at intersections of a plurality of data lines, a plurality of scanning lines, and a plurality of power lines. Each of the pixels stores a voltage corresponding to the data signal and generates light of a predetermined luminance while supplying a current corresponding to the stored voltage to the organic light emitting diode using the driving transistor.

On the other hand, the threshold voltage and the mobility of the driving transistor included in each of the pixels become uneven due to the process variation, and the desired luminance is not displayed accordingly.

In order to overcome such a problem, a method of supplying a current as a data signal has been proposed. When a current is supplied as a data signal, luminance can be realized regardless of the threshold voltage and the mobility deviation of the driving transistor. However, there is a problem that it is difficult to express a low gray level when a current is supplied as a data signal. In other words, when a minute current is supplied for low gradation implementation, a desired voltage can not be charged to a pixel within a predetermined time (for example, one horizontal period (1H)), .

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

An organic light emitting display according to an exemplary embodiment of the present invention includes pixels positioned in a pixel portion; And a data driver for sinking the first current and the second current from the pixels via data lines corresponding to data from the outside; Each of the pixels includes an organic light emitting diode; And a pixel circuit for storing a voltage corresponding to a current difference between a first current and a second current that are sinked via a data line and supplying a current corresponding to the stored voltage to the organic light emitting diode.

The current difference between the first current and the second current according to the embodiment is determined by the data.

The data driver may include a first sink unit for sinking the first current, and a second sink unit for sinking the second current, each channel connected to the data lines.

According to an embodiment, the first current is set to a fixed value, and the current value of the second current is changed by the data.

According to an embodiment, the second current is set to a fixed value, and the current value of the first current is changed by the data.

The current values of the first current and the second current are changed corresponding to the data according to the embodiment.

The first scan line, the second scan line, the third scan line, the fourth scan line, and the fourth scan line, which are formed for each horizontal line and connected to the pixels, A scan driver for supplying a signal; And a light emitting driver formed for each horizontal line to supply a light emission control signal to a light emission control line connected to the pixels.

According to an embodiment, the scan driver sequentially supplies the first scan signal to the first scan line, and during a first period of time during which the first scan signal is supplied to i (i is a natural number) first scan line, the third scan signal is supplied to the i-th third scan line during the second period of the period during which the first scan signal is supplied to the i-th first scan line, And supplies the second scan signal to the i-th second scan line during the remaining period except for the second period.

The data driver, according to an embodiment, sinks the first current during the first period and sinks the second current during the second period.

According to an embodiment, the light emitting driver supplies an emission control signal to an i-th emission control line so as to overlap a first scan signal supplied to an i-th first scan line.

The first scan signal, the second scan signal, the third scan signal, and the fourth scan signal are set to a voltage at which the transistors included in the pixels are turned on, Is set to a voltage at which the transistors included in the transistors are turned off.

According to an embodiment, the pixel circuit is connected between the first power source and the organic light emitting diode connected via the fourth node, and the pixel circuit is connected between the first power source and the fourth node for controlling the amount of current supplied to the organic light emitting diode A first transistor; A first capacitor and a second capacitor serially connected between the first power supply and the first node; A second transistor connected between a second node, which is a common node of the first capacitor and the second capacitor, and the first power source, and having a gate electrode connected to the fourth scan line; And a third transistor connected between the second node and the first node and having a gate electrode connected to the third scan line.

According to an embodiment, the pixel circuit may include a fourth transistor connected between the fourth node and the data line, and having a gate electrode connected to the first scanning line; A fifth transistor connected between the first node and the fourth node and having a gate electrode connected to the first scan line; A sixth transistor connected between the second capacitor and the first node, and having a gate electrode connected to the second scan line; And a seventh transistor connected between the fourth node and the organic light emitting diode.

A method of driving an organic light emitting display according to an exemplary embodiment of the present invention includes sequentially driving a first current and a second current from a pixel via a data line so that a voltage corresponding to a current difference between a first current and a second current is stored A step of sinking; And causing the pixel to emit light by a voltage corresponding to the current difference.

According to the embodiment, the current value of at least one of the first current and the second current is changed corresponding to the data.

The voltage corresponding to the current difference between the first current and the second current is stored in the pixel according to the organic light emitting display device and the driving method thereof according to the embodiment of the present invention. In this case, the current values of the first current and the second current can be set high, and the desired voltage can be charged to the pixel within a predetermined time. In the present invention, since the voltage charged in the pixel is determined by the current, a desired luminance can be realized regardless of the threshold voltage and the mobility of the driving transistor.

1 is a view illustrating an organic light emitting display according to an embodiment of the present invention.
2 is a diagram illustrating a data driver according to an embodiment of the present invention.
3 is a circuit diagram showing a pixel according to an embodiment of the present invention.
4 is a waveform diagram showing an embodiment of a driving waveform supplied to the pixel shown in Fig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4, which will be readily apparent to those skilled in the art.

1 is a view illustrating an organic light emitting display according to an embodiment of the present invention.

1, an organic light emitting display according to an exemplary embodiment of the present invention includes first scan lines S11 to S1n, second scan lines S21 to S2n, third scan lines S31 to S3n, A pixel portion 130 including pixels 140 positioned in a region partitioned by the four scan lines S41 to S4n, the emission control lines E1 to En and the data lines D1 to Dm, A scan driver 110 for driving the scan lines S11 to S1n to the fourth scan lines S41 to S4n, a data driver 120 for driving the data lines D1 to Dm, And a timing controller 160 for controlling the scan driver 110, the data driver 120, and the light emitting driver 150. The scan driver 110, the data driver 120,

The scan driver 110 supplies a first scan signal to the first scan lines S11 to S1n, a second scan signal to the second scan lines S21 to S2n, a third scan signal to the third scan lines S31 to S3n, , And supplies the fourth scan signal to the fourth scan lines S41 to S4n.

For example, the scan driver 110 sequentially supplies the first scan signals to the first scan lines S11 to S1n. 4, during the first period T1 during which the first scan signal is supplied to the n-th (n is a natural number) first scan line S1n, the scan driver 110 supplies the n- Supplies the fourth scan signal to the third scan line S4n and supplies the third scan signal to the nth third scan line S3n during the second period T2. The scan driver 110 may apply a second scan signal to the n-th second scan line S2n during a period other than the second period T2 during the period when the first scan signal is supplied to the n-th first scan line S1n. Supply.

The light emission driving unit 150 sequentially supplies the light emission control signals to the emission control lines E1 to En. For example, the light emitting driver 150 supplies the emission control signal to the nth emission control line En so as to overlap the first scan signal supplied to the nth first scan line S1n. Here, the first scan signal, the second scan signal, the third scan signal, and the fourth scan signal are set to a voltage (for example, a low voltage) at which the transistors included in each of the pixels 140 are turned on, The control signal is set to a voltage (for example, a high voltage) at which the transistors included in each of the pixels 140 are turned off.

The data driver 120 sinks the first current I1 from the pixels 140 via the data lines D1 to Dm to be synchronized with the fourth scan signal, And sinks the second current I2 from the pixels 140 via the lines D1 to Dm. To this end, the data driver 120 includes a first sink unit (not shown) for sinking a first current I1 for each channel and a second sink unit (not shown) for sinking a second current I2, Respectively. In addition, the first current I1 and the second current I2 are set to have a predetermined current difference corresponding to the data. A detailed description thereof will be described later.

The pixel unit 130 receives a first power ELVDD and a second power ELVSS set to a voltage lower than the first power ELVDD from the outside. The first power ELVDD and the second power ELVSS supplied to the pixel portion 130 are supplied to the pixels 140. [

The pixels 140 charge the voltage corresponding to the current difference between the first current I1 and the second current I2 and are emitted at a luminance corresponding to the charged voltage. Here, the voltage charged in the pixels 140 is determined by the current difference between the first current I1 and the second current I2, thereby charging the desired voltage regardless of the threshold voltage and the mobility of the driving transistor .

2 is a diagram illustrating a data driver according to an embodiment of the present invention. In FIG. 2, only one channel is shown for convenience of explanation.

2, the data driver 120 includes a first sink unit 122 for sinking a first current I1 for each channel, a second sink unit 122 for sinking a second current I2, (124).

The first sync section 122 generates the first current I1 in accordance with the data and supplies the generated first current I1 to the data line D in synchronization with the fourth scan signal. Here, the supply of the first current I1 means that the current is sinked from the pixel 140 selected by the fourth scan signal.

The second sync section 124 generates the second current I2 corresponding to the data and supplies the generated second current I2 to the data line D in synchronization with the third scan signal. Here, the supply of the second current I2 means that the current is sinked from the pixel 140 selected by the third scan signal.

At least one of the first sync section 122 and the second sync section 124 changes the current value of the first current and / or the second current in accordance with the gradation of the data Data. For example, the first sync section 122 generates a first current I1 having a constant current value, and the second sync section 124 generates a first current I1 corresponding to the data Data, The current value of the second current I2 can be changed so as to have the current difference. The second sync section 124 generates a second current I2 having a constant current value and the first sync section 122 generates a predetermined current I2 of the second current I2 corresponding to the data Data, The current value of the first current I1 can be changed so as to have the difference. The first sync section 122 and the second sync section 122 may change the first current I1 and the second current I2 to have a predetermined current difference corresponding to the data Data.

In the present invention, the first current I1 and the second current I2 are set to have a current value large enough to charge a desired voltage to the pixel 140 during a predetermined period. Then, the voltage can be stably charged in the pixel 140 corresponding to the first current I1 and the second current I2, thereby realizing a desired luminance regardless of the threshold voltage and the mobility of the driving transistor .

3 is a circuit diagram showing a pixel according to an embodiment of the present invention. For convenience of explanation, FIG. 3 shows pixels connected to the m-th data line Dm located on the n-th horizontal line.

Referring to FIG. 3, a pixel 140 according to an embodiment of the present invention includes an organic light emitting diode (OLED) and a pixel circuit 142 for controlling an amount of current supplied to the organic light emitting diode (OLED).

The organic light emitting diode OLED generates light having a predetermined luminance corresponding to the amount of current supplied from the pixel circuit 142.

The pixel circuit 142 charges a predetermined voltage corresponding to the current difference between the first current I1 and the second current I2 and supplies a current corresponding to the charged voltage to the organic light emitting diode OLED. To this end, the pixel circuit 142 includes a first transistor M1 to a seventh transistor M7, a first capacitor C1, and a second capacitor C2.

The first transistor (driving transistor: M1) is connected between the first power source ELVDD and the fourth node N4, and the gate electrode is connected to the first node N1. The first transistor M1 controls the amount of current supplied to the organic light emitting diode OLED corresponding to the voltage applied to the first node N1.

The second transistor M2 is connected between the first power source ELVDD and the second node N2 and the gate electrode is connected to the fourth scan line S4n. The second transistor M2 is turned on when the fourth scan signal is supplied to the fourth scan line S4n and supplies the voltage of the first power ELVDD to the second node N2.

The third transistor M3 is connected between the second node N2 and the first node N1 and the gate electrode is connected to the third scan line S3n. The third transistor M3 is turned on when the third scan signal is supplied to the third scan line S3n to electrically connect the second node N2 and the first node N1.

The fourth transistor M4 is connected between the fourth node N4 and the data line Dm and the gate electrode is connected to the first scan line S1n. The fourth transistor M4 is turned on when the first scan signal is supplied to the first scan line S1n to electrically connect the data line Dm and the fourth node N4.

The fifth transistor M5 is connected between the first node N1 and the fourth node N4, and the gate electrode is connected to the first scan line S1n. The fifth transistor M5 is turned on when the first scan signal is supplied to the first scan line S1n to electrically connect the first node N1 and the fourth node N4. When the first node N1 and the fourth node N4 are electrically connected, the first transistor M1 is formed in a diode form.

The sixth transistor M6 is connected between the third node N3 and the first node N1 and the gate electrode is connected to the second scan line S2n. The sixth transistor M6 is turned on when the second scan signal is supplied to the second scan line S2n to electrically connect the third node N3 and the first node N1.

The seventh transistor M7 is connected between the fourth node N4 and the anode electrode of the organic light emitting diode OLED, and the gate electrode thereof is connected to the emission control line En. The seventh transistor M7 is turned off when the emission control signal is supplied to the emission control line En, and is turned on in other cases.

The first capacitor C1 is connected between the first power source ELVDD and the second node N2. That is, the first capacitor C1 is connected in parallel with the second transistor M2 to charge the voltage applied to the second node N2.

And the second capacitor C2 is connected between the second node N2 and the third node N3. The second capacitor C2 charges a predetermined voltage corresponding to the voltages of the second node N2 and the third node N3.

4 is a waveform diagram showing an embodiment of a driving waveform supplied to the pixel shown in Fig.

Referring to FIG. 4, the emission control signal is supplied to the emission control line En and the seventh transistor M7 is turned off. When the seventh transistor M7 is turned off, the organic light emitting diode OLED and the fourth node N4 are electrically disconnected, thereby setting the pixel 140 to the non-emission state.

Thereafter, the first scanning signal is supplied to the first scanning line S1n. The second scan signal is supplied to the second scan line S2n and the fourth scan signal is supplied to the fourth scan line S4n during the first period T1 of the period during which the first scan signal is supplied. The first current I1 is synchronized from the data driver 120 during the first period T1 of the period during which the first scan signal is supplied.

When the fourth scan signal is supplied to the fourth scan line S4n, the second transistor M2 is turned on. When the second transistor M2 is turned on, the voltage of the first power ELVDD is supplied to the second node N2. When the second scan signal is supplied to the second scan line S2n, the sixth transistor M6 is turned on. When the sixth transistor M6 is turned on, the third node N3 and the first node N1 are electrically connected.

When the first scan signal is supplied to the first scan line S1n, the fourth transistor M4 and the fifth transistor M5 are turned on. When the fourth transistor M4 is turned on, the data line Dm and the fourth node N4 are electrically connected. When the fifth transistor M5 is turned on, the first node N1 and the fourth node N4 are electrically connected, so that the first transistor M1 is connected in a diode form.

When the data line Dm and the fourth node N4 are electrically connected to each other through the first power source ELVDD, the first transistor M1, the fourth transistor M4 and the data line Dm, Lt; RTI ID = 0.0 > I1 < / RTI > At this time, the first voltage is applied to the gate electrode of the first transistor M1 connected in the diode-type, that is, the first node N1 corresponding to the first current I1. Then, the second capacitor C2 stores the voltage corresponding to the difference between the voltage of the first power source ELVDD applied to the second node N2 and the first voltage applied to the first node N1.

The third scan signal is supplied to the third scan line S3n during the second period T2 of the period during which the first scan signal is supplied. The second current I2 is synchronized from the data driver 120 during the second period T2 of the period during which the first scan signal is supplied.

When the third scan signal is supplied to the third scan line S3n, the third transistor M3 is turned on. When the third transistor M3 is turned on, the second node N2 and the first node N1 are electrically connected.

Since the fourth transistor M4 and the fifth transistor M5 are maintained in the turned-on state by the first scan signal, the first power ELVDD, the first transistor M1, The fourth transistor M4 and the data line Dm are synchronized with the data driver 120. [ At this time, the second voltage is applied to the gate electrode of the first transistor M1 connected in the diode form, that is, the first node N1 corresponding to the second current I2. Here, since the first node N1 and the second node N2 are electrically connected, the voltage of the second node N2 is changed from the voltage of the first power source ELVDD to the second voltage. When the voltage of the second node N2 is changed, the voltage of the third node N3 is also changed by the coupling of the second capacitor C2.

Thereafter, the second scan signal is supplied to the second scan line S2n, and the supply of the emission control signal to the emission control line En is stopped. When the supply of the emission control signal to the emission control line En is interrupted, the seventh transistor M7 is turned on. When the seventh transistor M7 is turned on, the fourth node N4 and the anode electrode of the organic light emitting diode OLED are electrically connected.

When the second scan signal is supplied to the second scan line S2n, the sixth transistor M6 is turned on. When the sixth transistor M6 is turned on, the third node N3 and the first node N1 are electrically connected to each other, so that the voltage of the third node N3 is supplied to the first node N1 . At this time, the first transistor M1 controls the amount of current flowing from the first power source ELVDD to the second power source ELVSS via the organic light emitting diode OLED in response to the voltage of the first node N1, The light emitting diode OLED generates light of a predetermined luminance corresponding to the amount of current.

The voltage corresponding to the current difference between the first current I1 and the second current I2 is applied to the first node N1 in the present invention. That is, the voltage applied to the first node N1 is determined by the first current I1 and the second current I2, and accordingly, the threshold voltage of the first transistor M1 and the threshold voltage Can be implemented.

In addition, in the present invention, since the voltage is charged in the pixel 142 using the current difference between the first current I1 and the second current I2, the current value of the first current I1 and the second current I2 Can be set to be high, and thus the stability of driving can be ensured.

In the present invention, the transistors are shown as PMOS for convenience of description, but the present invention is not limited thereto. In other words, the transistors may be formed of NMOS.

Also, in the present invention, the organic light emitting diode (OLED) may generate red, green or blue light or produce white light according to the amount of current. When the organic light emitting diode (OLED) generates white light, a color image can be implemented using a separate color filter or the like.

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. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the present invention.

110: scan driver 120:
122: first sync section 124: second sync section
130: pixel portion 140: pixel
142: pixel circuit 150:
160:

Claims (15)

Pixels located in the pixel portion;
And a data driver for sinking the first current and the second current from the pixels via data lines corresponding to data from the outside;
Each of the pixels
An organic light emitting diode;
And a pixel circuit for storing a voltage corresponding to a current difference between a first current and a second current sinked via a data line and supplying a current corresponding to the stored voltage to the organic light emitting diode An electroluminescent display device. The method according to claim 1,
Wherein the current difference between the first current and the second current is determined by the data. 3. The method of claim 2,
The data driver may be configured such that each channel connected to the data lines
A first sink unit for sinking the first current,
And a second sink unit for sinking the second current. 3. The method of claim 2,
Wherein the first current is set to a fixed value, and the current value of the second current is changed by the data. 3. The method of claim 2,
Wherein the second current is set to a fixed value, and the current value of the first current is changed by the data. 3. The method of claim 2,
And the current values of the first current and the second current are changed corresponding to the data. The method according to claim 1,
A second scan line, a third scan line as a third scan line, and a fourth scan line as a fourth scan line, the first scan line being connected to the pixels and the fourth scan line being connected to the pixels, A scan driver;
And a light emitting driver for supplying a light emitting control signal to each of the emission control lines connected to the pixels, the emission control signal being formed for each horizontal line. 8. The method of claim 7,
The scan driver
Sequentially supplying the first scan signal to the first scan line,
supplies the fourth scan signal to an i-th fourth scan line during a first period of time during which the first scan signal is supplied to the i-th (i is a natural number) first scan line,
Supplying the third scan signal to an i-th third scan line during a second period of the period during which the first scan signal is supplied to the i-th first scan line,
And supplies the second scan signal to the i-th second scan line during the remaining period except for the second period. 9. The method of claim 8,
The data driver
And sinks the first current during the first period and sinks the second current during the second period. 9. The method of claim 8,
Wherein the light emitting driver supplies a light emission control signal to an i < th > emission control line so as to overlap a first scan signal supplied to an i < th > first scan line. 8. The method of claim 7,
The first scan signal, the second scan signal, the third scan signal, and the fourth scan signal are set to a voltage at which the transistors included in the pixels are turned on,
Wherein the emission control signal is set to a voltage at which the transistor included in the pixels is turned off. 8. The method of claim 7,
The pixel circuit
A first transistor connected between the first power source and the organic light emitting diode connected via a fourth node and controlling an amount of current supplied to the organic light emitting diode corresponding to a voltage of the first node;
A first capacitor and a second capacitor serially connected between the first power supply and the first node;
A second transistor connected between a second node, which is a common node of the first capacitor and the second capacitor, and the first power source, and having a gate electrode connected to the fourth scan line;
And a third transistor connected between the second node and the first node and having a gate electrode connected to the third scan line. 13. The method of claim 12,
The pixel circuit
A fourth transistor connected between the fourth node and the data line and having a gate electrode connected to the first scan line;
A fifth transistor connected between the first node and the fourth node and having a gate electrode connected to the first scan line;
A sixth transistor connected between the second capacitor and the first node, and having a gate electrode connected to the second scan line;
And a seventh transistor connected between the fourth node and the organic light emitting diode. Sinking a first current and a second current sequentially from a pixel via a data line so that a voltage corresponding to a current difference between the first current and the second current is stored;
And the pixel emits light by a voltage corresponding to the current difference. 15. The method of claim 14,
Wherein the current value of at least one of the first current and the second current is changed corresponding to the data.

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