KR100902221B1 - Pixel and organic light emitting display using the same - Google Patents

Abstract

A pixel and an organic light emitting display using the same are provided to display a desired brightness of an image by compensating deterioration. A first driving unit(144) compensates for the deterioration of an organic light-emitting diode, and a second driving unit(146) applies a reverse bias voltage to the organic light-emitting diode. An anode electrode of the organic light-emitting diode is connected to a pixel circuit(142), and a cathode electrode of the organic light-emitting diode is connected to a second power(ELVSS). A pixel circuit supplies the current to the organic light-emitting diode and compensates a threshold voltage of the first transistor.

Description

Pixel and Organic Light Emitting Display Using the Same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pixel and an organic light emitting display device using the same. In particular, a pixel, an organic light emitting display device using the same, and a driving thereof to compensate for degradation of the organic light emitting diode and to slow down the degradation of the organic light emitting diode. It is about a method.

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 device displays an image using an organic light emitting diode that generates light by recombination of electrons and holes. Such an organic light emitting display device has an advantage of having a fast response speed and driving with low power consumption.

1 is a circuit diagram illustrating a pixel of a conventional organic light emitting display device.

Referring to FIG. 1, a pixel 4 of a conventional organic light emitting display device is connected to an organic light emitting diode OLED, a data line Dm, and a scanning line Sn to control the organic light emitting diode OLED. The pixel circuit 2 is provided.

The anode electrode of the organic light emitting diode OLED is connected to the pixel circuit 2, and the cathode electrode is connected to the second power source ELVSS. Such an organic light emitting diode (OLED) generates light having a predetermined brightness in response to a current supplied from the pixel circuit 2.

The pixel circuit 2 controls the amount of current supplied to the organic light emitting diode OLED corresponding to the data signal supplied to the data line Dm when the scan signal is supplied to the scan line Sn. To this end, the pixel circuit 2 includes a second transistor M2 connected between the first power supply ELVDD and the organic light emitting diode OLED, the second transistor M2, the data line Dm, and the scan line Sn. And a first capacitor M1 connected between the first transistor M1 and a storage capacitor Cst connected between the gate electrode and the first electrode of the second transistor M2.

The gate electrode of the first transistor M1 is connected to the scan line Sn, and the first electrode is connected to the data line Dm. The second electrode of the first transistor M1 is connected to one terminal of the storage capacitor Cst. 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 first transistor M1 connected to the scan line Sn and the data line Dm is turned on when a scan signal is supplied from the scan line Sn to receive a data signal supplied from the data line Dm to the storage capacitor Cst. ). In this case, the storage capacitor Cst charges a voltage corresponding to the data signal.

The gate electrode of the second transistor M2 is connected to one terminal of the storage capacitor Cst, and the first electrode is connected to the other terminal of the storage capacitor Cst and the first power supply ELVDD. 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 from the first power source ELVDD to the second power source ELVSS via the organic light emitting diode OLED in response to the voltage value stored in the storage capacitor Cst. In this case, the organic light emitting diode OLED generates light corresponding to the amount of current supplied from the second transistor M2.

However, such a conventional pixel 4 has a problem in that an image having a desired luminance cannot be displayed due to a change in efficiency due to deterioration of the organic light emitting diode OLED. In other words, the organic light emitting diode deteriorates with time, and thus an image having a desired brightness cannot be displayed. In fact, as the organic light emitting diode deteriorates, light of low luminance is generated.

In addition, since the voltage applied to the anode electrode of the organic light emitting diode (OLED) is always set higher than the voltage applied to the cathode, the conventional pixel 4 has a problem in that deterioration proceeds quickly.

Accordingly, an object of the present invention is to provide a pixel and an organic light emitting display using the same, which compensate for degradation of the organic light emitting diode and slow down the degradation rate of the organic light emitting diode.

In an embodiment of the present invention, the pixel includes an organic light emitting diode having a cathode electrode connected to a second power source; A pixel circuit including a driving transistor for controlling the amount of current supplied from the first power source to the organic light emitting diode; A first driver connected between the organic light emitting diode and the pixel circuit and adjusting a voltage of a gate electrode of the driving transistor in response to deterioration of the organic light emitting diode; A second driver for applying a reverse bias voltage to the organic light emitting diode; The first driver includes a sixth transistor and a seventh transistor connected between the anode electrode of the organic light emitting diode and the initialization power supply; And a feedback capacitor connected between the common node between the sixth and seventh transistors and the gate electrode of the driving transistor.

An organic light emitting display device according to an embodiment of the present invention includes: a scan driver for sequentially supplying a scan signal to scan lines and sequentially supplying a light emission control signal to emission control lines; A data driver for supplying a data signal to the data lines; The pixel of any one of Claims 1-4, 6-11, and 13-15 is provided.

According to the pixel of the present invention and the organic light emitting display device using the same, an image having a desired luminance can be displayed by compensating deterioration of the organic light emitting diode. In addition, the present invention has the advantage of slowing the degradation rate of the organic light emitting diode by applying a reverse bias voltage to the organic light emitting diode.

Hereinafter, the present invention will be described in detail with reference to FIG. 2 to FIG. 9 with which preferred embodiments in which the present invention pertains can easily carry out the present invention.

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 display device according to an exemplary embodiment of the present invention includes pixels positioned to be connected to scan lines S1 to Sn, emission control lines E1 to En, and data lines D1 to Dm. Driving the pixel unit 130 including the 140, the scan driver 110 for driving the scan lines S1 to Sn and the emission control lines E1 to En, and the data lines D1 to Dm. And a timing controller 150 for controlling the data driver 120 and the scan driver 110 and the data driver 120.

The scan driver 110 receives the scan driving control signal SCS from the timing controller 150. The scan driver 110 supplied with the scan driving control signal SCS generates a scan signal and sequentially supplies the generated scan signal to the scan lines S1 to Sn. In addition, the scan driver 110 generates an emission control signal in response to the scan driving control signal SCS, and sequentially supplies the generated emission control signal to the emission control lines E1 to En. Here, the width of the light emission control signal is set to the same or wider width than the scan signal. For example, the width of the light emission control signal supplied to the i (i is a natural number) light emission control line is set so as to overlap the scan signal supplied to the i-th scan line. In addition, the width of the light emission control signal supplied to the i-th light emission control line may be set so as to overlap with the i-1th scan line and the scan signal supplied to the i-th scan line.

The data driver 120 receives the data drive control signal DCS from the timing controller 150. The data driver 120 receiving the data driving control signal DCS generates a data signal and supplies the generated data signal to the data lines D1 to Dm in synchronization with the scan signal.

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 supplies the data Data supplied from the outside to the data driver 120.

The pixel unit 130 receives the first power source ELVDD and the second power source ELVSS from the outside and supplies the same to the pixels 140. Each of the pixels 140 supplied with the first power source ELVDD and the second power source ELVSS generates light corresponding to the data signal. Here, the emission time of the pixels 140 is controlled by the emission control signal. Meanwhile, the first power supply ELVDD is set to a higher voltage value than the second power supply ELVSS.

In FIG. 2, the pixels 140 are connected to one scan line S and the emission control line E, but the present invention is not limited thereto. In fact, the pixels 140 may be connected to two or more scan lines S and the emission control line E, corresponding to the structure of the pixel circuit included in the pixels 140. The pixels 140 may additionally receive initialization power from the outside. Here, the initialization power source is used to initialize the gate electrode of the driving transistor included in each of the pixels 140.

3 is a diagram illustrating a pixel according to a first embodiment of the present invention. In FIG. 3, pixels connected to the nth scan line Sn and the mth data line Dm are illustrated for convenience of description.

Referring to FIG. 3, the pixel according to the first exemplary embodiment of the present invention includes an organic light emitting diode (OLED), a pixel circuit 142 for supplying current to the organic light emitting diode (OLED), and an organic light emitting diode (OLED). And a second driver 146 for applying a reverse bias voltage 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. The organic light emitting diode OLED generates light having a predetermined brightness in correspondence with the amount of current supplied from the pixel circuit 142. To this end, the first power supply ELVDD has a higher voltage value than the second power supply ELVSS.

On the other hand, the threshold voltage of the organic light emitting diode (OLED) is changed in response to deterioration of the organic light emitting diode (OLED). In fact, the threshold voltage of the organic light emitting diode OLED increases as the organic light emitting diode OLED deteriorates.

The pixel circuit 142 supplies current to the OLED and compensates for the threshold voltage of the first transistor M1 (ie, the driving transistor). To this end, the pixel circuit 142 includes the first to fifth transistors M5.

The gate electrode of the second transistor M2 is connected to the nth scan line Sn, and the first electrode is connected to the data line Dm. The second electrode of the second transistor M2 is connected to the first node N1 which is a common node of the first capacitor C1 and the second capacitor C2. The second transistor M2 is turned on when the scan signal is supplied to the nth scan line Sn to supply the data signal supplied to the data line Dm to the first node N1.

The gate electrode of the first transistor M1 is connected to the second node N2, and the first electrode is connected to the first power source ELVDD. The second electrode of the first transistor M1 is connected to the first electrode of the fifth transistor M5. The first transistor M1 supplies a current corresponding to the voltage applied to the second node N2 to the organic light emitting diode OLED.

The first electrode of the third transistor M3 is connected to the second electrode of the first transistor M1, and the second electrode is connected to the second node N2. The gate electrode of the third transistor M3 is connected to the n-1 th scan line Sn-1. The third transistor M3 is turned on when the scan signal is supplied to the n-1 th scan line Sn-1 to connect the first transistor M1 in the form of a diode.

The first electrode of the fourth transistor M4 is connected to the first power source ELVDD, and the second electrode is connected to the first node N1. The gate electrode of the fourth transistor M4 is connected to the n-1 th scan line Sn-1. The fourth transistor M4 supplies the voltage of the first power supply ELVDD to the first node N1 when the scan signal is supplied to the n-1 th scan line Sn-1.

The first electrode of the fifth transistor M5 is connected to the second electrode of the first transistor M1, and the second electrode is connected to the anode electrode of the organic light emitting diode OLED. The gate electrode of the fifth transistor M5 is connected to the emission control line En. The fifth transistor M5 is turned on when the emission control signal (high level voltage) is not supplied to the emission control line En (that is, the low level voltage), so that the organic light emitting diode OLED and the first transistor are turned on. (M1) is electrically connected.

The first capacitor C1 is positioned between the first node N1 and the first power source ELVDD. The first capacitor C1 charges a voltage corresponding to the data signal.

The second capacitor C2 is positioned between the first node N1 and the second node N2. The second capacitor C2 charges a voltage corresponding to the threshold voltage of the first transistor M1.

The first driver 144 controls the voltage of the gate electrode of the first transistor M1 (that is, the voltage of the second node N2) in response to the deterioration of the organic light emitting diode OLED. In other words, the first driver 144 compensates the deterioration of the organic light emitting diode OLED by controlling the voltage drop width of the second node N2 in response to the deterioration of the organic light emitting diode OLED.

To this end, the first driving unit 144 includes a sixth transistor M6 and a seventh transistor M7 and a sixth transistor M6 positioned between the emission control line En and the anode electrode of the organic light emitting diode OLED. ) And a feedback capacitor Cfb positioned between the third node N3 and the second node N2, which are common nodes between the second transistor and the seventh transistor M7.

The sixth transistor M6 is positioned between the third node N3 and the organic light emitting diode OLED and is turned on when a scan signal is supplied to the n−1 th scan line Sn−1.

The seventh transistor M7 is positioned between the emission control line En and the third node N3. Here, the second electrode and the gate electrode of the seventh transistor M7 are connected to the emission control line En. That is, the seventh transistor M7 is connected in the form of a diode to supply the voltage of the third node N3 to the emission control line En when the emission control signal is not supplied (that is, a low level voltage). On the other hand, the sixth transistor M6 connected to the n-1 th scan line Sn-1 and the seventh transistor M7 connected to the emission control line En are not turned on at the same time. Time does not overlap.)

The feedback capacitor Cfb transfers the voltage change amount of the third node N3 to the second node N2.

The second driver 146 applies a reverse bias voltage to the OLED. To this end, the second driver 146 includes an eighth transistor M8 positioned between the initialization power supply Vint and the anode electrode of the organic light emitting diode OLED. When the scan signal is supplied to the nth scan line Sn, the eighth transistor M8 is turned on to supply the voltage of the initialization power supply Vint to the anode electrode of the organic light emitting diode OLED. Here, the voltage value of the initialization power supply Vint is set to a voltage lower than the voltage of the second power supply ELVSS. Meanwhile, the turn-on time of the eighth transistor M8 is set not to overlap the turn-on time of the sixth transistor M6.

4 is a diagram illustrating a driving waveform supplied to the pixel illustrated in FIG. 3.

Referring to FIGS. 3 and 4, the operation process is described in detail. First, a scan signal is supplied to the n-th scan line Sn-1, and a light emission control signal is supplied to the emission control line En. When the scan signal is supplied to the n-1 th scan line Sn-1, the third transistor M3, the fourth transistor M4, and the sixth transistor M6 are turned on. When the emission control signal is supplied to the emission control line En, the seventh transistor M7 and the fifth transistor M5 are turned off.

When the third transistor M3 is turned on, the first transistor M1 is connected in the form of a diode. When the fourth transistor M4 is turned on, the voltage of the first power source ELVDD is supplied to the first node N1. At this time, the second capacitor C2 is charged with a voltage corresponding to the threshold voltage of the first transistor M1.

When the sixth transistor M6 is turned on, the threshold voltage of the organic light emitting diode OLED is supplied to the third node N3. Here, the third node N3 maintains the threshold voltage of the organic light emitting diode OLED during a period in which the first capacitor C1 and the second capacitor C2 are charged with a predetermined voltage.

Subsequently, the scan signal is stopped from the n-th scan line Sn- 1 and the scan signal is supplied to the n-th scan line Sn. When the scan signal is supplied to the n-th scan line Sn, the second transistor M2 is supplied. ) And the eighth transistor M8 are turned on.

When the second transistor M2 is turned on, the data signal supplied to the data line Dm is supplied to the first node N1. At this time, the first capacitor C1 charges a voltage corresponding to the data signal. On the other hand, since the second node N2 is set to the floating state, the voltage charged in the second capacitor C2 does not change even when the data signal is supplied to the first node N1.

When the eighth transistor M8 is turned on, the voltage of the initialization power supply Vint is connected to the anode electrode of the organic light emitting diode OLED. In this case, a reverse bias voltage is applied to the organic light emitting diode OLED. As described above, when the reverse bias voltage is applied to the organic light emitting diode OLED, the degradation progress rate of the organic light emitting diode OLED may be slowed down.

Thereafter, the supply of the scan signal to the nth scan line Sn is stopped, and the supply of the emission control signal to the emission control line En is stopped. When the supply of the emission control signal is stopped, the third voltage V3 is applied to the emission control line En. Here, the third voltage V3 may be supplied with a voltage lower than the threshold voltage of the organic light emitting diode OLED, for example, the same voltage as the initialization power supply Vint.

When the third voltage V3 is applied to the emission control line En, the seventh transistor M7 is turned on. When the seventh transistor M7 is turned on, the voltage of the third node N3 drops to the third voltage V3. When the voltage of the third node N3 falls to the third voltage V3, the voltage of the second node N2 also decreases by the feedback capacitor Cfb. In this case, the first transistor M1 supplies a current corresponding to the lowered voltage to the organic light emitting diode OLED.

On the other hand, the organic light emitting diode OLED deteriorates with time. Here, as the OLED degrades, the threshold voltage of the OLED increases. Therefore, as the organic light emitting diode OLED deteriorates, the voltage drop width of the third node N3 increases. In other words, as the OLED degrades, the voltage of the OLED supplied to the third node N3 increases, so that the voltage drop width of the third node N3 does not deteriorate. It is set higher than the case.

When the voltage drop width (ie, the voltage falling down) of the third node N3 increases, the drop voltage of the second node N2 also increases. That is, the first driver 144 compensates the deterioration of the OLED by controlling the voltage of the second node N2 to decrease as the OLED deteriorates.

Meanwhile, in the present invention, the structures of the first driver 144 and the pixel circuit 142 may be changed in various forms.

5 is a diagram illustrating a pixel according to a second exemplary embodiment of the present invention. 5, the same reference numerals are assigned to the same parts as in FIG. 3, and detailed description thereof will be omitted.

Referring to FIG. 5, the first driver 144 ′ of the pixel 140 according to the second embodiment of the present invention is a sixth transistor positioned between the initialization power supply Vint and the anode electrode of the organic light emitting diode OLED. Feedback located between the third node N3 and the second node N2, which are common nodes between the M6 and the seventh transistors M7 ′, and the sixth transistor M6 and the seventh transistor M7 ′. Capacitor Cfb is provided.

The sixth transistor M6 is positioned between the third node N3 and the organic light emitting diode OLED and is turned on when a scan signal is supplied to the n−1 th scan line Sn−1.

The seventh transistor M7 'is positioned between the initialization power supply Vint and the third node N3. The seventh transistor M7 'is connected to the emission control line En and turned on when the emission control signal is not supplied, and is turned off when the emission control signal is supplied.

Referring to the operation process, first, when the scan signal is supplied to the n-th scan line Sn-1, the sixth transistor M6 is turned on and the threshold voltage of the organic light emitting diode OLED is turned on to the third node N3. Is supplied. Subsequently, the supply of the emission control signal to the emission control line En is stopped so that the seventh transistor M7 'is turned on. When the seventh transistor M7 'is turned on, the voltage of the third node N3 drops to the voltage of the initialization power supply Vint. At this time, the voltage of the second node N2 is changed by the feedback capacitor Cfb to correspond to the voltage change amount of the third node N3.

6 is a diagram illustrating a pixel according to a third exemplary embodiment of the present invention. 6, the same reference numerals are assigned to the same parts as in FIG. 3, and detailed description thereof will be omitted.

Referring to FIG. 6, the first driver 144 ″ of the pixel 140 according to the third exemplary embodiment of the present invention is positioned between the initialization power supply Vint and the anode electrode of the organic light emitting diode OLED. Between the transistor M6 and the seventh transistor M7 ″, and between the third node N3 and the second node N2 which are common nodes between the sixth transistor M6 and the seventh transistor M7 ″. With a feedback capacitor Cfb positioned.

The sixth transistor M6 is positioned between the third node N3 and the organic light emitting diode OLED and is turned on when a scan signal is supplied to the n−1 th scan line Sn−1.

The seventh transistor M7 ″ is positioned between the initialization power supply Vint and the third node N3. The seventh transistor M7 ″ is connected to the nth scan line Sn and is turned on when the scan signal is supplied, and is turned off when the scan signal is not supplied.

Referring to the operation process, first, when the scan signal is supplied to the n-th scan line Sn-1, the sixth transistor M6 is turned on and the threshold voltage of the organic light emitting diode OLED is turned on to the third node N3. Is supplied. Thereafter, the scan signal is supplied to the nth scan line Sn to turn on the seventh transistor M7 ″. When the seventh transistor M7 'is turned on, the voltage of the third node N3 drops to the voltage of the initialization power supply Vint. At this time, the voltage of the second node N2 is changed by the feedback capacitor Cfb to correspond to the voltage change amount of the third node N3.

7 is a diagram illustrating a pixel according to a fourth exemplary embodiment of the present invention. In FIG. 7, the pixel structure is changed compared to the pixel illustrated in FIG. 3.

Referring to FIG. 7, a pixel according to a fourth embodiment of the present invention includes an organic light emitting diode (OLED), a pixel circuit 142 ′ for supplying current to the organic light emitting diode (OLED), and an organic light emitting diode (OLED). ) And a second driver 146 ′ for applying a reverse bias voltage 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. The organic light emitting diode OLED generates light having a predetermined luminance in correspondence with the amount of current supplied from the pixel circuit 142 '.

The pixel circuit 142 ′ supplies current to the organic light emitting diode OLED and compensates for the threshold voltage of the first transistor M1 ′ (ie, the driving transistor). To this end, the pixel circuit 142 'includes a first transistor M1', a second transistor M2 ', a third transistor M3', a fourth transistor M4 ', a tenth transistor M10, and a first transistor. 11 transistors M11 are provided.

The first electrode of the first transistor M1 'is connected to the first power supply ELVDD via the tenth transistor M10, and the second electrode is connected to the organic light emitting diode OLED through the eleventh transistor M11. Is connected to the anode electrode. The gate electrode of the first transistor M1 'is connected to the second node N2'. The first transistor M1 'supplies a current corresponding to the voltage applied to the first capacitor C1', that is, the voltage applied to the second node N2 ', to the organic light emitting diode OLED.

The first electrode of the third transistor M3 'is connected to the second electrode of the first transistor M1, and the second electrode is connected to the gate electrode of the first transistor M1'. The gate electrode of the third transistor M3 'is connected to the nth scan line Sn. When the scan signal is supplied to the nth scan line Sn, the third transistor M3 'is turned on to connect the first transistor M1' in the form of a diode. That is, when the third transistor M3 'is turned on, the first transistor M1' is connected in the form of a diode.

The first electrode of the second transistor M2 'is connected to the data line Dm, and the second electrode is connected to the first electrode of the first transistor M1. The gate electrode of the second transistor M2 'is connected to the nth scan line Sn. The second transistor M2 'is turned on when the scan signal is supplied to the nth scan line Sn to supply the data signal supplied to the data line D to the first electrode of the first transistor M1'. Supply.

The first electrode of the fourth transistor M4 'is connected to the second node N2', and the second electrode is connected to the initialization power supply Vint. The gate electrode of the fourth transistor M4 'is connected to the n-th scan line Sn-1. The fourth transistor M4 'is turned on when the scan signal is supplied to the n-th scan line Sn-1 to initialize the second node N2'.

The first electrode of the tenth transistor M10 is connected to the first power source ELVDD, and the second electrode is connected to the first electrode of the first transistor M1 '. The gate electrode of the tenth transistor M10 is connected to the emission control line En. The tenth transistor M10 is turned on when the emission control signal is not supplied to electrically connect the first power source ELVDD and the first transistor M1 ′.

The first electrode of the eleventh transistor M11 is connected to the first transistor M1 ', and the second electrode is connected to the organic light emitting diode OLED. The gate electrode of the eleventh transistor M11 is connected to the emission control line En. The eleventh transistor M11 is turned on when the emission control signal is not supplied to electrically connect the first transistor M1 ′ to the organic light emitting diode OLED.

The second capacitor C2 'is connected between the second node N2' and the nth scan line Sn. The second capacitor C2 ′ increases the voltage of the second node N2 when the supply of the scan signal is stopped.

The first capacitor C1 'is connected between the first power source ELVDD and the second node N2'. The first capacitor C1 ′ stores a voltage corresponding to the data signal.

The first driver 144 ′ ″ controls the voltage of the gate electrode of the first transistor M1 ′ (ie, the voltage of the second node N2 ′) in response to deterioration of the organic light emitting diode OLED. In other words, the first driver 144 ′ ″ compensates for the deterioration of the organic light emitting diode OLED while controlling the voltage drop width of the second node N2 ′ in response to the deterioration of the organic light emitting diode OLED. .

To this end, the first driver 144 ′ ″ includes a sixth transistor M6 ′ and a seventh transistor M7 ′ positioned between the initialization power supply Vint and the anode electrode of the OLED. A feedback capacitor Cfb is disposed between the third node N3 'and the second node N2', which are common nodes between the sixth transistor M6 'and the seventh transistor M7'.

The sixth transistor M6 'is positioned between the third node N3' and the organic light emitting diode OLED, and is turned on when the scan signal is supplied to the nth scan line Sn.

The seventh transistor M7 'is positioned between the initialization power supply Vint and the third node N3'. The seventh transistor M7 'is turned on when the emission control signal is not supplied to supply the initialization power supply Vint to the third node N3. Here, the sixth transistor M6 'and the seventh transistor M7' are turned on for different times.

 The feedback capacitor Cfb transfers the voltage change amount of the third node N3 'to the second node N2'.

The second driver 146 ′ applies a reverse bias voltage to the OLED. To this end, the second driver 146 ′ includes an eighth transistor M8 ′ positioned between the initialization power supply Vint and the anode electrode of the organic light emitting diode OLED. The eighth transistor M8 ′ is turned on when the scan signal is supplied to the n−1 th scan line Sn−1 to supply the voltage of the initialization power supply Vint to the anode electrode of the organic light emitting diode OLED.

Referring to FIG. 4, the scan signal is first supplied to the n-th scan line Sn- 1 so that the fourth transistor M4 'and the eighth transistor M8' are turned on. The emission control signal is supplied to the emission control line En to turn off the seventh transistor M7 ′, the tenth transistor M10, and the eleventh transistor M11.

When the fourth transistor M4 'is turned on, the voltage of the initialization power supply Vint is supplied to the second node N2'. Then, the voltage of the second node N2 'is initialized to the voltage of the initialization power supply Vint.

When the eighth transistor M8 'is turned on, a reverse bias voltage is applied to the organic light emitting diode OLED.

Thereafter, the scan signal is supplied to the nth scan line Sn. When the scan signal is supplied to the nth scan line Sn, the second transistor M2 ', the third transistor M3', and the sixth transistor M6 'are turned on.

When the third transistor M3 'is turned on, the first transistor M1' is connected in the form of a diode. When the second transistor M2 'is turned on, the data signal supplied to the data line Dm is supplied to the first electrode of the first transistor M1'. Here, since the gate electrode of the first transistor M1 'is initialized to the voltage of the initialization power supply Vint, the data signal supplied to the first electrode of the first transistor M1' passes through the third transistor M3 '. Is supplied to the gate electrode of the first transistor M1 '. In this case, the first capacitor C1 ′ charges a voltage corresponding to the data signal.

When the sixth transistor M6 'is turned on, the threshold voltage of the organic light emitting diode OLED is applied to the third node N3'.

After the threshold voltage of the organic light emitting diode OLED is applied to the third node N3 ′, the supply of the scan signal to the nth scan line Sn is stopped and the emission control signal is supplied to the emission control line En. It stops.

When the supply of the scan signal to the nth scan line Sn is stopped, the second transistor M2 ', the third transistor M3', and the sixth transistor M6 'are turned off. When the supply of the emission control signal to the emission control line En is stopped, the seventh transistor M7 ′, the tenth transistor M10, and the eleventh transistor M11 are turned on.

When the seventh transistor M7 'is turned on, the voltage of the third node N3' drops to the voltage of the initialization power supply Vint. At this time, the voltage of the second node N2 'is also lowered by the feedback capacitor Cfb by a voltage corresponding to the voltage drop amount of the third node N3'. Here, deterioration of the organic light emitting diode OLED is compensated for in response to the voltage drop amount of the third node N3 '.

When the supply of the scan signal to the nth scan line Sn is stopped, the voltage of the second node N2 'is increased by the second capacitor C2'. Here, when the voltage of the second node N2 'rises, the voltage drop of the data signal due to the line resistance component is compensated. Here, the voltage increase amount of the second node N2 'by the second capacitor C2' is always set constant, and the voltage drop amount of the second node N2 'by the feedback capacitor Cfb is organic. It is determined by the deterioration of the light emitting diode OLED.

When the tenth transistor M10 and the eleventh transistor M11 are turned on, a current path is formed from the first power source ELVDD to the organic light emitting diode OLED. In this case, the first transistor M1 ′ supplies a current corresponding to the voltage of the second node N2 ′ to the organic light emitting diode OLED.

8 is a diagram illustrating a pixel according to a fifth exemplary embodiment of the present invention. In the pixel circuit 142 ″ shown in FIG. 8, the fourth transistor M4 ′ is removed, the second transistor M2 ″, the third transistor M3 ″, and the second capacitor C2 ″. Is set to be the same as the pixel circuit 142 'shown in FIG. 7 except that is connected to the n-th scan line Sn-1. Since the configuration and operation of the first driving unit 144 ′ and the second driving unit 146 of FIG. 8 have been described above, a detailed description thereof will be omitted.

An operation process of the pixel circuit 142 ″ of FIG. 8 will be described with reference to the waveform diagram of FIG. 9. In FIG. 9, the emission control signal supplied to the emission control line En is supplied after the n−1 th scan line Sn is supplied.

When the scan signal is supplied to the n−1 th scan line Sn−1, the second transistor M2 ″, the third transistor M3 ″, and the sixth transistor M6 are turned on.

When the third transistor M3 ″ is turned on, the voltage of the second node N2 ′ is supplied to the second power supply ELVSS via the eleventh transistor M11 and the organic light emitting diode OLED. . That is, the voltage of the second node N2 'is initialized during the period in which the scan signal is supplied to the n-th scan line Sn-1 and the emission control signal is not supplied to the emission control line En.

Thereafter, the emission control signal is supplied to the emission control line En so that the tenth transistor M10 and the eleventh transistor M11 are turned off. Then, the data signal supplied to the data line Dm is supplied to the second node N2 ', and a voltage corresponding to the data signal is charged in the first capacitor C1'.

After the light emission control signal is supplied to the first capacitor C1 ′, a scan signal is supplied to the nth scan line Sn to apply a reverse bias voltage to the organic light emitting diode OLED. Subsequently, the supply of the emission control signal to the scan signal supplied to the nth scan line Sn and the emission control line En is stopped. Then, the seventh transistor M7 'is turned on so that the voltage of the initialization power supply Vint is supplied to the third node N3', thereby degrading the organic light emitting diode OLED. The voltage at the node N2 'is changed.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various modifications are possible within the scope of the technical idea of the present invention.

1 is a diagram illustrating a general pixel.

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

FIG. 3 is a diagram illustrating a first embodiment of the pixel illustrated in FIG. 2.

4 is a waveform diagram illustrating a method of driving the pixel illustrated in FIG. 3.

FIG. 5 is a diagram illustrating a second embodiment of the pixel illustrated in FIG. 2.

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

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

FIG. 8 is a diagram illustrating a fifth embodiment of the pixel illustrated in FIG. 2.

9 is a waveform diagram illustrating a method of driving the pixel illustrated in FIG. 8.

<Description of the symbols for the main parts of the drawings>

2: pixel circuit 4: pixel

110: scan driver 120: data driver

130: pixel portion 140: pixel

142: pixel circuit 144, 146: driver

150: timing controller

Claims (17)

An organic light emitting diode having a cathode electrode connected to the second power source; A pixel circuit including a driving transistor for controlling the amount of current supplied from the first power source to the organic light emitting diode; A first driver connected between the organic light emitting diode and the pixel circuit and adjusting a voltage of a gate electrode of the driving transistor in response to deterioration of the organic light emitting diode; A second driver for applying a reverse bias voltage to the organic light emitting diode; The first driving unit A sixth transistor and a seventh transistor connected between the anode electrode of the organic light emitting diode and the initialization power supply; And a feedback capacitor connected between the common node between the sixth and seventh transistors and a gate electrode of the driving transistor. The method of claim 1, The pixel circuit A first capacitor and a second capacitor connected between the first electrode of the driving transistor connected to the first power source and the gate electrode of the driving transistor; A second transistor connected between the first node and the data line between the first capacitor and the second capacitor and turned on when a scan signal is supplied to an i (i is a natural number) scan line; A third transistor connected between the gate electrode and the second electrode of the driving transistor and turned on when the scan signal is supplied to the i-1th scan line; A fourth transistor connected between the first node and the first power source and turned on when a scan signal is supplied to the i-1th scan line; And a fifth transistor connected between the second electrode of the driving transistor and the organic light emitting diode and turned off when the emission control signal is supplied to the i-th emission control line. The method of claim 1, The pixel circuit A second transistor connected between a data line and a first electrode of the driving transistor and turned on when a scan signal is supplied to an i (i is a natural number) scan line; A third transistor connected between the gate electrode and the second electrode of the driving transistor and turned on when a scan signal is supplied to the i-th scan line; A fourth transistor connected between an initialization power supply having a voltage lower than the second power supply and a gate electrode of the driving transistor and turned on when a scan signal is supplied to an i-1th scan line; A tenth transistor connected between the first power supply and the first electrode of the driving transistor and turned off when an emission control signal is supplied to an i-th emission control line; And an eleventh transistor connected between the second electrode of the driving transistor and the organic light emitting diode and turned off when an emission control signal is supplied to the i th emission control line. The method of claim 1, The pixel circuit A second transistor connected between a data line and a first electrode of the driving transistor and turned on when a scan signal is supplied to an i-1 (i is a natural number) scan line; A third transistor connected between the gate electrode and the second electrode of the driving transistor and turned on when a scan signal is supplied to the i-1th scan line; A tenth transistor connected between the first power supply and the first electrode of the driving transistor and turned off when an emission control signal is supplied to an i-th emission control line; And an eleventh transistor connected between the second electrode of the driving transistor and the organic light emitting diode and turned off when an emission control signal is supplied to the i th emission control line. delete The method of claim 1, And the sixth and seventh transistors do not overlap in turn-on time. The method of claim 1, And the initialization power supply is set to a lower voltage than the second power supply. The method of claim 1, And the sixth transistor is turned on when a scan signal is supplied to an i (i is a natural number) -1 th scan line to connect the common node and the organic light emitting diode. The method of claim 8, And the seventh transistor is turned on when a scan signal is supplied to an i-th scan line to supply the voltage of the initialization power supply to the common node. The method of claim 8, And the seventh transistor is turned on when the emission control signal is not supplied to the i-th emission control line to supply the voltage of the initialization power supply to the common node. The method of claim 1, The sixth transistor is turned on when the scan signal is supplied to the i (i is a natural number) scan line, and the seventh transistor is turned on when the emission control signal is not supplied to the i th emission control line. Pixel made. delete The method of claim 1, The second driving unit And an eighth transistor connected between the initialization power supply having a voltage value lower than the second power supply and the anode electrode of the organic light emitting diode. The method of claim 13, The turn-on time of the eighth transistor is set so as not to overlap the turn-on time of the sixth transistor. The method of claim 14, And the eighth transistor is turned on when a scan signal is supplied to an i (i is a natural number) scan line or an i-1 th scan line. A scan driver for sequentially supplying scan signals to scan lines and sequentially supplying light emission control signals to light emission control lines; A data driver for supplying a data signal to the data lines; An organic light emitting display device comprising the pixel according to any one of claims 1 to 4, 6 to 11, and 13 to 15. The method of claim 16, And the scan driver supplies the light emission control signal supplied to the i-th light emission control line to overlap the scan signal supplied to the i-1th scan line and the i-th scan line.

Images