KR20060027027A - Light emitting display and driving method thereof - Google Patents

Abstract

The present invention relates to a light emitting display device and a driving method thereof for preventing afterimages.

According to an exemplary embodiment of the present invention, a light emitting display device includes: an image display unit including a plurality of pixels; and a first power supplying a first power source having a voltage value changed at least twice to an anode electrode of a light emitting element included in each of the pixels. And a second power supply unit supplying a second power source having a voltage value changed at least twice to the cathode electrode of the light emitting device.

By such a configuration, in the present invention, deterioration and afterimage of the light emitting device can be prevented by applying a reverse bias voltage to the light emitting device.

Description

Light Emitting Display and Driving Method Thereof             

1A and 1B are views illustrating a general light emitting device.

2 is a view showing a light emitting display device according to a first embodiment of the present invention;

FIG. 3 is a diagram illustrating a first embodiment of a driving waveform supplied to the light emitting display device shown in FIG. 2.

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

FIG. 5 is an equivalent view of a portion of the pixel shown in FIG. 2; FIG.

FIG. 6 is a circuit diagram illustrating a first power supply unit illustrated in FIG. 2.

FIG. 7 is a circuit diagram illustrating a second power supply unit illustrated in FIG. 2.

FIG. 8 is a waveform diagram illustrating a control signal supplied to the transistors shown in FIGS. 6 and 7.

FIG. 9 illustrates a second embodiment of a driving waveform supplied to the light emitting display shown in FIG.

FIG. 10 is a diagram illustrating a third embodiment of a driving waveform supplied to the light emitting display device shown in FIG. 2.

11 is a view showing a light emitting display device according to a second embodiment of the present invention;

FIG. 12 illustrates a first embodiment of a driving waveform supplied to the light emitting display device shown in FIG.

FIG. 13 illustrates a second embodiment of a driving waveform supplied to the light emitting display shown in FIG.

FIG. 14 is a circuit diagram showing a first embodiment of the pixel shown in FIG.

FIG. 15 is an equivalent view of a portion of the pixel shown in FIG. 14; FIG.

FIG. 16 is a circuit diagram showing a second embodiment of the pixel shown in FIG.

FIG. 17 is an equivalent view of a portion of the pixel shown in FIG. 16; FIG.

18 is a circuit diagram showing a third embodiment of the pixel shown in FIG.

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

20: anode electrode 21: cathode electrode

110,210: scan driver 120: data driver

130: image display unit 140,200: pixel

142,202 pixel circuit 150 timing controller

160: first power supply unit 162, 172: output line

170: second power supply unit 180: control unit

The present invention relates to a light emitting display device and a driving method thereof, and more particularly, to a light emitting display device and a driving method thereof capable of preventing afterimages.

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, a light emitting display, and the like.

Among flat panel display devices, the light emitting display device includes a plurality of light emitting devices, and the light emitting devices generate predetermined light by recombination of electrons and holes. Such a light emitting display device has an advantage in that it has a fast response speed and is driven with low power consumption.

1A and 1B illustrate a conventional general light emitting device.

1A and 1B, the light emitting device includes an emission layer (EL), a hole transfer layer (HTL), and an electron transport layer (Eltctron Transfer) formed between the anode electrode 20 and the cathode electrode 21. Layer: ETL).

The anode electrode 20 is connected to the first power source to supply holes to the light emitting layer EL. The cathode electrode 20 is connected to a second power source lower than the first power source to supply electrons to the light emitting layer EL. That is, the anode electrode 20 has a relatively higher potential of positive polarity (+) than the cathode electrode 21, and the cathode electrode 21 has a relatively low negative polarity (−) than the anode electrode 20. Has a potential of.

The hole transport layer HTL accelerates holes supplied from the anode electrode 20 and supplies them to the light emitting layer EL. The electron transport layer ETL accelerates and supplies electrons supplied from the cathode electrode 21 to the emission layer EL. Holes supplied from the hole transport layer HTL and electrons supplied from the electron transport layer ETL collide in the emission layer EL. In this case, electrons and holes are recombined in the emission layer EL, thereby generating predetermined light. Subsequently, the emission layer EL is formed of an organic material to generate light of one of red (R), green (G), and blue (B) when electrons and holes recombine.

Meanwhile, the light emitting device includes a hole injection layer (HIL) located between the hole transport layer (HTL) and the anode electrode 20, and an electron injection layer located between the electron transport layer (ETL) and the cathode electrode 21. (Electron Injection Layer: EIL) is further included. The hole injection layer HIL supplies holes to the hole transport layer HTL. The electron injection layer EIL supplies electrons to the electron transport layer ETL.

Since the voltage applied to the anode electrode 20 is always set higher than the voltage applied to the cathode electrode 21 in the light emitting device (LED), as shown in FIG. Carriers are positioned, and positive carriers are positioned on the cathode electrode 21 side. Here, if the carriers of the negative polarity (-) positioned in the anode electrode 20 and the carriers of the positive polarity (+) located in the cathode electrode 21 are maintained for a long time, the amount of movement of electrons and holes contributing to light emission becomes small. As the luminance decreases, an afterimage occurs. In particular, the afterimage phenomenon is more severe when the same image (for example, a still image) is displayed for a long time, and serves as an important factor for degrading display quality. In addition, when the afterimage occurs for a long time, the light emitting device (LED) is deteriorated and the life is shortened.

Accordingly, it is an object of the present invention to provide a light emitting display device and a method of driving the same, which can prevent afterimages.

In order to achieve the above object, the first aspect of the present invention provides an image display unit including a plurality of pixels, and a first power source having a voltage value changed at least twice to an anode electrode of a light emitting element included in each of the pixels. And a second power supply unit supplying a second power source having a voltage value changed at least twice to a cathode electrode of the light emitting device.

Preferably, the first power supply supplies a first voltage and a second voltage having a voltage lower than the first voltage for one frame period. The second power supply unit supplies a third voltage having a voltage lower than the first voltage and a fourth voltage having a voltage higher than the second voltage during the one frame period.

According to a second aspect of the present invention, there is provided an image display device including a plurality of pixels; A first power supply for supplying a first voltage and a second voltage having a voltage lower than the first voltage to an anode of a light emitting element included in each of the pixels; When the first voltage is supplied to the anode of the light emitting device, a third voltage lower than the first voltage is supplied to apply a forward bias to the light emitting device, and the second voltage is supplied to the anode of the light emitting device. The present invention provides a light emitting display device having a second power supply for applying a fourth voltage higher than the second voltage so that a reverse bias is applied to the light emitting device.

Preferably, the second voltage light fourth voltage is supplied for at least a part of one frame.

According to a third aspect of the present invention, a first voltage is supplied to an anode electrode of a light emitting device so that a forward bias voltage is applied, and a third voltage lower than the first voltage is supplied to a cathode electrode of the light emitting device; And supplying a second voltage lower than the first voltage to the anode electrode of the light emitting device so as to be applied, and supplying a fourth voltage higher than the second voltage to the cathode electrode of the light emitting device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIG. 2 to FIG. 18 to which a person skilled in the art may easily implement the present invention.

2 is a diagram illustrating a light emitting display device according to a first embodiment of the present invention. FIG. 3 is a waveform diagram illustrating a driving method according to the first embodiment of the light emitting display device illustrated in FIG. 2.

2 and 3, a light emitting display device according to a first embodiment of the present invention includes pixels 140 formed in an intersection area of scan lines S1 to Sn and data lines D1 to Dm. The image display unit 130, the scan driver 110 for driving the scan lines S1 to Sn, the data driver 120 for driving the data lines D1 to Dm, the scan driver 110 and the data. A timing controller 150 is provided to control the driver 120.

The timing controller 150 uses the data driving control signal DCS by using a synchronization signal (including the vertical signal Vsync, the horizontal signal Hsync, the dot clock DOTCLK, etc.) supplied from the outside. The scan drive control signal SCS is generated. 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 scan driver 110 receives the scan driving control signal SCS from the timing controller 150. The scan driver 110 supplied with the scan drive control signal SCS generates a scan signal every one horizontal period 1H, and sequentially generates the scan signals as the first scan line S1 to the nth scan line Sn. Supply.

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. Here, the data signal is supplied every time the scan signal is supplied.

The image display unit 130 receives the first power from the first power supply unit 160 and the second power from the second power supply unit 170. Here, the first power source and the second power source are supplied to the respective pixels 140.

4 is a circuit diagram illustrating a pixel of the light emitting display device illustrated in FIG. 2.

Referring to FIG. 4, the pixel 140 of the light emitting display according to the exemplary embodiment of the present invention generates light corresponding to the data signal supplied to the data line D when the scan signal is applied to the scan line S. Referring to FIG. . To this end, each pixel 140 is connected to a light emitting device (LED), a light emitting device (LED), a data line (D), and a scanning line (S) to emit light of the light emitting device (LED). It is provided.

The anode electrode of the light emitting element (LED) is connected to the pixel circuit 142, and the cathode electrode is connected to the second power source. Such a light emitting device (LED) generates light corresponding to the current supplied from the pixel circuit 142.

The pixel circuit 142 includes a second transistor M2 connected between the first power supply and the light emitting element LED, and a second transistor M2 connected between the second transistor M2, the data line D, and the scan line S. A first transistor M1 and a storage capacitor C connected between the gate terminal and the first terminal of the second transistor M2 are provided.

The gate terminal of the first transistor M1 is connected to the scan line S, and the first terminal is connected to the data line D. The second terminal of the first transistor M1 is connected to one side of the storage capacitor C. Here, the first terminal means any one of a source terminal and a drain terminal. The second terminal is different from the first terminal, for example, when the first terminal means the source terminal, the second terminal is set as the drain terminal, and when the first terminal means the drain terminal, the second terminal is the source terminal. Is set to. The first transistor M1 is turned on when the scan signal is supplied from the scan line S to supply the data signal supplied from the data line D to the storage capacitor C. At this time, the storage capacitor C is charged with a voltage corresponding to the data signal.

The gate terminal of the second transistor M2 is connected to one terminal of the storage capacitor C, and the first terminal is connected to the other terminal of the storage capacitor C and the first power supply. The second terminal of the second transistor M2 is connected to the anode electrode of the light emitting element LED. The second transistor M2 controls the amount of current flowing from the first power supply to the light emitting device LED in response to the voltage value stored in the storage capacitor C. In this case, the organic light emitting diode LED generates light having a luminance corresponding to the amount of current supplied from the second transistor M2.

Meanwhile, as illustrated in FIG. 2, the light emitting display device of the present invention includes a first power supply unit 160, a second power supply unit 170, and a controller 180.

The controller 180 controls the first power supply unit 160 and the second power supply unit 170.

The first power supply unit 160 generates a voltage of the first power supply and supplies the voltage to each of the pixels 140. Here, the voltage value of the first power source supplied from the first power supply unit 160 varies at least twice in one frame 1F period. In detail, the period of one frame 1F is positioned between the second period during which the scan signal and the data signal are supplied so that a predetermined image can be displayed on the image display unit 140, and between the second period and the previous frame. Is divided into a first period, and a third period located between the second period and the next frame.

The first power supply unit 160 supplies the first power having the first voltage V1 so that each of the pixels 140 can be normally driven during the second period. The first power supply unit 160 supplies a second voltage V2 having a voltage lower than the first voltage V1 during the third period after the second period.

The second power supply unit 170 generates a voltage of the second power supply and supplies the voltage to each of the pixels 140. Here, the voltage value of the second power source supplied from the second power supply unit 170 varies at least twice during one frame 1F. In detail, the second power supply unit 170 supplies a second power source having a third voltage V3 so that each of the pixels 140 can be normally driven during the second period. Here, the voltage value of the third voltage V3 is set lower than the voltage of the first voltage V1. The second power supply unit 170 supplies a fourth voltage V4 having a voltage higher than the third voltage V3 during the third period after the second period. Here, the voltage value of the fourth voltage V4 is set higher than the voltage value of the second voltage V2. Then, a reverse bias voltage is applied to the light emitting device LED during the third period to prevent the afterimage from occurring in the image display unit 130.

2 to 4, the scan signals are sequentially supplied during the second period of one frame 1F, and the data signals are simultaneously supplied. In addition, the first power supply unit 160 supplies the first voltage V1 to each of the pixels 140, and the second power supply unit 170 supplies the third voltage V1 to each of the pixels 140. To supply. Then, light corresponding to the data signal is generated in each of the pixels 140.

Thereafter, the first power supply unit 160 supplies the second voltage V2 to each of the pixels 140 for at least a portion of the third period, and the fourth voltage V4 is supplied from the second power supply unit 170. Is supplied to each of the pixels 140. Here, since the voltage value of the fourth voltage V4 is set higher than the voltage value of the second voltage V2, the reverse bias voltage is applied to the light emitting device LED.

In other words, the second transistor M2 and the light emitting device LED included in each of the pixels 140 during the second period may be equivalently represented by the resistors R _M2 and R _LED as shown in FIG. 5. . Therefore, when the second voltage V2 is supplied to the anode electrode side of the light emitting element LED and the fourth voltage V4 is supplied to the cathode electrode during the third period, the voltage applied to the anode electrode of the light emitting element LED is greater than the voltage applied to the anode electrode. The voltage applied to the cathode electrode is set high, thereby applying a reverse bias voltage to the light emitting device (LED).

As described above, when the reverse bias voltage is applied, positive carriers formed on the cathode electrode and negative carriers formed on the anode electrode are removed as shown in FIG. 1B during the second period. That is, in the present invention, the afterimage may be prevented by applying the reverse bias voltage to the light emitting device (LED) during the third period. When the reverse bias voltage is applied to the light emitting device (LED), since the holes (+) and electrons (−) formed in the second period are removed, the amount of movement of the electrons and holes can be prevented from being reduced, and thus the desired luminance is achieved. Can display the image. In addition, when the reverse bias voltage is applied to the light emitting device LED, the degradation of the light emitting device LED may be prevented to improve the lifespan.

FIG. 6 is a circuit diagram schematically illustrating the first power supply unit illustrated in FIG. 2.

Referring to FIG. 6, the first power supply unit 160 of the present invention includes a first transistor MS1 and a second transistor MS2. The first transistor MS1 is provided between the first voltage source V1 and the output line 162. The first transistor MS1 is controlled by the first control signal CS1 and supplies the voltage of the first voltage source V1 to the output line 162.

The second transistor MS2 is provided between the second voltage source V2 and the output line 162. The second transistor MS2 supplies the voltage of the second voltage source V2 to the output line 162 while being controlled by the second control signal CS2.

Herein, the controller 180 controls the first control signal CS1 and the second control signal so that the first transistor MS1 is turned on and the second transistor MS2 is turned off during the second period as shown in FIG. 8. (CS2) is supplied. Then, the first voltage V1 is supplied to the output line 162 during the second period, and the first voltage V1 is supplied to each of the pixels 140. In addition, the controller 180 controls the first control signal CS1 to turn off the first transistor MS1 and to turn on the second transistor MS2 for at least a part of the third period following the second period. And a second control signal CS2. Then, the second voltage V2 is supplied to the output line 162 during the third period, and the second voltage V2 is supplied to each of the pixels 140.

FIG. 7 is a circuit diagram schematically illustrating the second power supply unit illustrated in FIG. 2.

Referring to FIG. 7, the second power supply unit 170 of the present invention includes a third transistor MS3 and a fourth transistor MS4. The third transistor MS3 is provided between the third voltage source V3 and the output line 172. The third transistor MS3 is controlled by the first control signal CS1 and supplies the voltage of the third voltage source V3 to the output line 172.

The fourth transistor MS4 is provided between the fourth voltage source V4 and the output line 172. The fourth transistor MS4 is controlled by the second control signal CS2 and supplies the voltage of the fourth voltage source V4 to the output line 172.

Herein, the controller 180 controls the first control signal CS1 and the second control signal so that the third transistor MS3 is turned on and the fourth transistor MS4 is turned off during the second period as shown in FIG. 8. (CS2) is supplied. Then, the third voltage V3 is supplied to the output line 172 during the second period, and the third voltage V3 is supplied to each of the pixels 140. The controller 180 may turn off the third transistor MS3 and turn on the fourth transistor MS4 for at least a portion of the third period following the second period. And a second control signal CS2. Then, the fourth voltage V4 is supplied to the output line 172 during the third period, and the fourth voltage V4 is supplied to the respective pixels 140.

In the present invention as described above, the supply time of the second voltage V2 supplied from the first power supply unit 160 and the fourth voltage V4 supplied from the second power supply unit 170 may be variously set.

9 is a waveform diagram illustrating a method of driving a light emitting display device according to a second embodiment of the present invention. 9, detailed description of the same parts as in FIG. 3 will be omitted.

Referring to FIG. 9, in the method of driving a light emitting display device according to the second embodiment of the present invention, the second voltage V2 supplied from the first power supply unit 160 is supplied in a first period of one frame. The fourth voltage V2 supplied from the second power supply unit 170 is also supplied in the first period of one frame so as to be synchronized with the second voltage V2. Then, the reverse bias voltage is applied to the light emitting device LED during the first period, thereby preventing the afterimage.

10 is a waveform diagram illustrating a method of driving a light emitting display device according to a third embodiment of the present invention. 10, detailed description of the same parts as in FIG. 3 will be omitted.

Referring to FIG. 10, in the method of driving the light emitting display device according to the third embodiment of the present invention, the second voltage V2 supplied from the first power supply unit 160 is applied in the first period and the third period of one frame. Supplied. In addition, the fourth voltage V2 supplied from the second power supply unit 170 is also supplied in the first period and the third period of one frame to be synchronized with the second voltage V2. Then, the reverse bias voltage is applied to the light emitting device (LED) during the first period and the third period to prevent the afterimage.

11 is a view showing a light emitting display device according to a second embodiment of the present invention. 12 and 13 are waveform diagrams illustrating a method of driving the light emitting display device illustrated in FIG. 11. 11, the same components as those in FIG. 2 are assigned the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG. 11, the light emitting display device according to the second embodiment of the present invention includes a scan driver 210 for driving the plurality of pixels 200 and the scan lines S1 to Sn positioned in the image display unit 130. ), The data driver 120 for driving the data lines D1 to Dm, the timing controller 150 for controlling the scan driver 210 and the data driver 120, and the pixels 200. The first power supply unit 160 for supplying the first power, the second power supply unit 170 for supplying the second power to the pixels 200, the first power supply unit 160 and the second power supply unit ( And a controller 180 for controlling the 170.

The first power supply unit 160 generates a voltage of the first power supply and supplies it to the anode electrode side of the light emitting device (LED) included in each of the pixels 200. Here, the first power supply unit 160 supplies the first voltage V1 during the second period and the second voltage V2 during the third period.

The second power supply unit 170 generates a voltage of the second power supply and supplies the generated voltage to the cathode electrode side of the light emitting device (LED) included in each of the pixels 200. Here, the second power supply unit 170 supplies the third voltage V3 during the second period and supplies the fourth voltage V4 during the third period. Then, the reverse bias voltage is applied to the light emitting device LED during the third period to prevent the afterimage from occurring in the image display unit 130. In addition, when the reverse bar ice voltage is applied to the light emitting device LED, an image having a desired brightness is displayed, and the life of the light emitting device LED may be prevented from being deteriorated. Meanwhile, the supply time point of the fourth voltage V4 of the second voltage V2 may be variously set. In practice, the second voltage V2 and the fourth voltage V4 may be supplied during at least one of the first period and the third period.

The scan driver 210 receives a scan driving control signal SCS from the timing controller 150. The scan driver 210 supplied with the scan driving control signal SCS generates a scan signal every one horizontal period 1H, and sequentially generates the scan signals as the first scan line S1 to the nth scan line Sn. Supply. 12 and 13, the scan driver 210 generates the emission control signal EMI, and generates the emission control signal EMI from the first emission control line E1 to the nth emission control line. Supply sequentially with (En). Here, the width of the emission control signal EMI supplied to the emission control line E is set in various ways corresponding to the structures of the pixels 200. For example, the width of the emission control signal EMI may be set to correspond to one scan signal as shown in FIG. 12 or to correspond to two scan signals as shown in FIG.

The pixels 200 are positioned to be connected to the scan line S, the data line E, and the emission control line E. FIG. Such pixels 200 emit light corresponding to the data signal from the data line E when the scan signal is supplied to the scan line S. FIG. Here, the emission time of the pixels 200 is controlled by the emission control signal EMI supplied to the emission control line E.

FIG. 14 is a diagram illustrating a first embodiment of the pixel of the light emitting display device illustrated in FIG. 11.

Referring to FIG. 14, the pixel 200 of the present invention is connected to a light emitting device LED, a data line D, a scanning line S, and a light emission control line E to emit light of the light emitting device LED. The pixel circuit 202 is provided.

The anode electrode of the light emitting element (LED) is connected to the pixel circuit 202, and the cathode electrode is connected to the second power source. Such a light emitting device (LED) generates light corresponding to the current supplied from the pixel circuit 202.

The pixel circuit 202 includes a first transistor M1, a second transistor M2, a third transistor M3, and a storage capacitor C.

The first transistor M1 is turned on when the scan signal is supplied to the scan line S. When the first transistor M1 is turned on, the data signal supplied to the data line D is supplied to the storage capacitor C.

The storage capacitor C charges a voltage corresponding to the data signal when the first transistor M1 is turned on.

The second transistor M2 supplies a current corresponding to the voltage charged in the storage capacitor Cst to the third transistor M3.

The gate terminal of the third transistor M3 is connected to the emission control line E, and the first terminal is connected to the second terminal of the second transistor M2. The second terminal of the third transistor M3 is connected to the light emitting element LED. The third transistor M3 controls the supply time of the current flowing from the second transistor M2 to the light emitting device LED in response to the emission control signal EMI supplied to the emission control line E. FIG.

12 and 14, the scan signal and the emission control signal EMI are sequentially supplied during the second period of one frame 1F and the data signals are simultaneously supplied. The first power supply unit 160 supplies the first voltage V1 to each of the pixels 200, and the second power supply unit 170 supplies the third voltage V3 to each of the pixels 200. To supply. Then, light corresponding to the data signal is generated in each of the pixels 200.

Thereafter, the first power supply unit 160 supplies the second voltage V2 to each of the pixels 200 during the third period, and the fourth voltage V4 is supplied from the second power supply unit 170 to each pixel. To the field 200. Here, since the voltage value of the fourth voltage V4 is set higher than the voltage value of the second voltage V2, the reverse bias voltage is applied to the light emitting device LED.

In other words, the second transistor M2, the third transistor M3, and the light emitting device LED included in each of the pixels 200 during the third period may have the same resistances R _M2 and R as shown in FIG. 15. _M3 , R _LED ). Therefore, when the second voltage V2 is supplied to the anode electrode side of the light emitting element LED and the fourth voltage V4 is supplied to the cathode electrode during the third period, the voltage applied to the anode electrode of the light emitting element LED is greater than the voltage applied to the anode electrode. The voltage applied to the cathode electrode is set high, thereby applying a reverse bias voltage to the light emitting device (LED).

When a reverse bias voltage is applied to the light emitting device (LED), as shown in FIG. 1B, the carriers of the positive polarity (+) formed in the cathode electrode and the carriers of the negative polarity (−) formed in the anode electrode are removed. That is, in the present invention, the afterimage may be prevented by applying the reverse bias voltage to the light emitting device (LED). When the reverse bias voltage is applied to the light emitting device (LED), since the holes (+) and electrons (−) formed in the second period are removed, the amount of movement of the electrons and holes can be prevented from being reduced, and thus the desired luminance is achieved. Can display the image. In addition, when the reverse bias voltage is applied to the light emitting device LED, the degradation of the light emitting device LED may be prevented to improve the lifespan.

FIG. 16 is a diagram illustrating a second embodiment of the pixel of the light emitting display device illustrated in FIG. 11.

Referring to FIG. 16, the pixel 200 of the present invention is connected to a light emitting device LED, a data line D, a scanning line S, and a light emission control line E to emit light of the light emitting device LED. The pixel circuit 202 is provided.

The anode electrode of the light emitting element (LED) is connected to the pixel circuit 202, and the cathode electrode is connected to the second power source. Such a light emitting device (LED) generates light corresponding to the current supplied from the pixel circuit 202.

The pixel circuit 202 is connected between the storage capacitor C and the sixth transistor M6 connected between the first power supply and the n-1 scan line Sn-1, and the first power supply and the data line D. The first transistor M1 and the fourth transistor M4, the fifth transistor M5 connected to the light emitting element LED and the emission control line E, the first node N1 and the fifth transistor A second transistor M2 connected between M5 and a third transistor M3 connected between the gate terminal and the second terminal of the first transistor M1 are provided.

The first terminal of the second transistor M2 is connected to the first node N1, and the second terminal is connected to the first terminal of the fifth transistor M5. The gate terminal of the second transistor M2 is connected to the storage capacitor C. The second transistor M2 supplies a current corresponding to the voltage charged in the storage capacitor C to the light emitting device LED.

The second terminal of the third transistor M3 is connected to the gate terminal of the second transistor M2, and the first terminal is connected to the second terminal of the second transistor M2. The gate terminal of the third transistor M3 is connected to the nth scan line Sn. The third transistor M3 is turned on when a scan signal is supplied to the nth scan line Sn to connect the second transistor M2 in the form of a diode. That is, when the third transistor M3 is turned on, the second transistor M2 is connected in the form of a diode.

The first terminal of the first transistor M1 is connected to the data line D, and the second terminal is connected to the first node N1. The gate terminal of the first transistor M1 is connected to the nth scan line Sn. The first transistor M1 is turned on when the scan signal is supplied to the nth scan line Sn and supplies the data signal supplied to the data line D to the first node N1.

The second terminal of the fourth transistor M4 is connected to the first node N1, and the first terminal is connected to the first power source. The gate terminal of the fourth transistor M4 is connected to the light emission control line E. FIG. The fourth transistor M4 is turned on when the emission control signal EMI is not supplied to electrically connect the first power source and the first node N1.

The first terminal of the fifth transistor M5 is connected to the second terminal of the second transistor M2, and the second terminal is connected to the light emitting element OLED. The gate terminal of the fifth transistor M5 is connected to the light emission control line E. FIG. The fifth transistor M5 is turned on when the emission control signal EMI is not supplied to supply the current supplied from the second transistor M2 to the light emitting device OLED.

The first terminal of the sixth transistor M6 is connected to the storage capacitor C, and the second terminal and the gate terminal are connected to the n−1 th scan line Sn−1. The sixth transistor M6 is turned on when the scan signal is supplied to the n-1 th scan line Sn-1 to initialize the gate terminal of the storage capacitor Cst and the first transistor M1.

13 and 16, the scan signal and the emission control signal EMI are sequentially supplied during the second period of one frame 1F, and the data signals are simultaneously supplied. The first power supply unit 160 supplies the first voltage V1 to each of the pixels 200, and the second power supply unit 170 supplies the third voltage V3 to each of the pixels 200. To supply. Then, light corresponding to the data signal is generated in each of the pixels 200.

Thereafter, the first power supply unit 160 supplies the second voltage V2 to each of the pixels 200 during the third period, and the fourth voltage V4 is supplied from the second power supply unit 170 to each pixel. To the field 200. Here, since the voltage value of the fourth voltage V4 is set higher than the voltage value of the second voltage V2, the reverse bias voltage is applied to the light emitting device LED.

In other words, the fourth transistor M4, the first transistor M1, the fifth transistor M5, and the light emitting device LED included in each of the pixels 200 during the third period are equivalent to each other as shown in FIG. 17. It can be represented by the resistor (R _M4 , R _M1 , R _M5 , R _LED ). Therefore, when the second voltage V2 is supplied to the anode electrode side of the light emitting device LED and the fourth voltage V4 is supplied to the cathode electrode for the third period, it is higher than the voltage applied to the anode electrode of the light emitting device LED. The voltage applied to the cathode electrode is set high, thereby applying a reverse bias voltage to the light emitting device (LED).

When a reverse bias voltage is applied to the light emitting device (LED), as shown in FIG. 1B, the carriers of the positive polarity (+) formed in the cathode electrode and the carriers of the negative polarity (−) formed in the anode electrode are removed. That is, in the present invention, the afterimage may be prevented by applying the reverse bias voltage to the light emitting device (LED). When the reverse bias voltage is applied to the light emitting device (LED), since the holes (+) and electrons (−) formed in the second period are removed, the amount of movement of the electrons and holes can be prevented from being reduced, and thus the desired luminance is achieved. Can display the image. In addition, when the reverse bias voltage is applied to the light emitting device LED, the degradation of the light emitting device LED may be prevented to improve the lifespan.

In the present invention, the structure of the pixel may be variously set. And, although the pixels shown in FIGS. 4, 14 and 16 are implemented with P type transistors, the pixels may be implemented with N type transistors in the present invention. For example, the pixel illustrated in FIG. 4 may be implemented with an N type transistor as shown in FIG. 18.

The above detailed description and drawings are merely exemplary of the present invention, which 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 claims or the 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 light emitting display device and the driving method thereof, the afterimage may be prevented by applying a reverse bias voltage to the light emitting device. In addition, in the present invention, by applying a reverse bias voltage to the light emitting device, it is possible to prevent the movement amount of holes and electrons from being reduced, thereby displaying an image having a desired luminance. When the reverse bias voltage is applied to the light emitting device, the light emitting device can be prevented from being deteriorated, thereby improving the lifespan.

Claims (23)

An image display unit including a plurality of pixels, A first power supply unit supplying a first power source having a voltage value changed at least twice to an anode electrode of a light emitting device included in each of the pixels; And a second power supply unit supplying a second power source having a voltage value changed at least twice to a cathode of the light emitting device. The method of claim 1, The first power supply unit supplies a first voltage and a second voltage having a lower voltage than the first voltage during one frame period, and the second power supply unit has a voltage lower than the first voltage during the one frame period. And a fourth voltage having a third voltage and a voltage higher than the second voltage. The method of claim 2, The one frame is divided into a second period in which a data signal is supplied to the pixels, a first period located between the second period and the previous frame, and a third period located between the second period and the next frame. Driven light emitting display device. The method of claim 3, wherein The first power supply unit and the second power supply unit supply the second voltage and the fourth voltage during at least a part of the first period, and supply the first voltage and the third voltage during the second and third periods. Light emitting display device. The method of claim 3, wherein The first power supply unit and the second power supply unit supply the second voltage and the fourth voltage during at least some of the third period, and supply the first voltage and the third voltage during the first period and the second period. Light emitting display device. The method of claim 3, wherein The first power supply unit and the second power supply unit supply the second voltage and the fourth voltage during at least some of the first period and the third period, and supply the first voltage and the third voltage during the second period. Light emitting display device. The method of claim 2, The first power supply unit includes a first transistor provided between a first voltage source for supplying the first voltage and an output line, and a second transistor provided between an output line and a second voltage source for supplying the second voltage. A light emitting display device having a. The method of claim 7, wherein The second power supply unit includes a third transistor provided between the third voltage source for supplying the third voltage and the output line, and a fourth transistor installed between the fourth voltage source for supplying the fourth voltage and the output line. A light emitting display device having a. The method of claim 8, And a control unit for controlling turn-on and turn-off timings of the first to fourth transistors. The method of claim 1, Each of the pixels A first transistor connected to the scan line and the data line; A storage capacitor for charging a voltage corresponding to a data signal supplied from the data line when the first transistor is turned on; And a second transistor for controlling a current supplied to the light emitting device in response to the voltage charged in the storage capacitor. The method of claim 10, Each of the pixels further includes a third transistor having a gate terminal connected to an emission control line, a first terminal connected to the second transistor, and a second terminal connected to the light emitting element. The method of claim 10, Each of the pixels A third transistor connected between the gate terminal and the second terminal of the second transistor and controlled by a scan signal supplied from an n (n is a natural number) scan line; A fourth transistor connected between the second transistor and the first power source and controlled by an emission control signal supplied from an emission control line; A fifth transistor connected between the second transistor and the light emitting element and controlled by the light emission control signal; and a sixth transistor having a gate terminal and a second terminal connected to the n−1 th scan line, and a first terminal connected to the gate terminal of the second transistor. The method of claim 1, A scan driver for driving a plurality of scan lines formed to be connected to the pixels; A data driver for driving a plurality of data lines formed to be connected to the pixels; And a timing controller for controlling the scan driver and the data driver. An image display unit having a plurality of pixels; A first power supply for supplying a second voltage having a first voltage and a voltage lower than the first voltage to an anode of a light emitting element included in each of the pixels; When the first voltage is supplied to the anode of the light emitting device, a third voltage lower than the first voltage is supplied to apply a forward bias to the light emitting device, and the second voltage is supplied to the anode of the light emitting device. And a second power supply for applying a fourth voltage higher than the second voltage so that a reverse bias is applied to the light emitting device. The method of claim 14, The second voltage light fourth voltage is supplied for at least a portion of one frame. The method of claim 14, Each of the pixels A first transistor connected to the scan line and the data line; A storage capacitor for charging a voltage corresponding to a data signal supplied from the data line when the first transistor is turned on; And a second transistor for controlling a current supplied to the light emitting device in response to the voltage charged in the storage capacitor. The method of claim 16, Each of the pixels further includes a third transistor having a gate terminal connected to an emission control line, a first terminal connected to the second transistor, and a second terminal connected to the light emitting element. The method of claim 16, Each of the pixels A third transistor connected between the gate terminal and the second terminal of the second transistor and controlled by a scan signal supplied from an n (n is a natural number) scan line; A fourth transistor connected between the second transistor and the first power source and controlled by an emission control signal supplied from an emission control line; A fifth transistor connected between the second transistor and the light emitting element and controlled by the light emission control signal; and a sixth transistor having a gate terminal and a second terminal connected to the n−1 th scan line, and a first terminal connected to the gate terminal of the second transistor. Supplying a first voltage to an anode electrode of the light emitting device such that a forward bias voltage is applied, and supplying a third voltage lower than the first voltage to the cathode electrode of the light emitting device; And supplying a second voltage lower than the first voltage to the anode electrode of the light emitting device so that a reverse bias voltage is applied, and supplying a fourth voltage higher than the second voltage to the cathode electrode of the light emitting device. Method of driving the device. The method of claim 19, One frame includes a second period during which a data signal is supplied to the pixels including the light emitting element, a first period located between the second period and the previous frame, and a second period located between the second period and the next frame. A method of driving a light emitting display device which is divided into third periods. The method of claim 20, A light emitting display in which the second voltage and the fourth voltage are supplied to the light emitting element for at least a part of the first period, and the first voltage and the third voltage are supplied to the light emitting element during the second and third periods. Method of driving the device. The method of claim 20, A light emitting display in which the second voltage and the fourth voltage are supplied to the light emitting element for at least a part of the third period, and the first voltage and the third voltage are supplied to the light emitting element during the first and second periods. Method of driving the device. The method of claim 20, A light emitting display in which the second voltage and the fourth voltage are supplied to the light emitting element during at least a part of the first and third periods, and the first voltage and the third voltage are supplied to the light emitting element during a second period. Method of driving the device.

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