KR100688813B1 - Pixel and light emitting display having the same - Google Patents

Abstract

The present invention relates to a pixel and a light emitting display device having the same to prevent luminance unevenness and deterioration of image quality due to variations in threshold voltage of a transistor.

The pixel according to the present invention includes a switching unit for outputting a current corresponding to the data signal supplied to the data line according to the scanning signal supplied to the scanning line, a light emitting element emitting light by the current supplied from the switching unit, and the switching unit And a transistor connected in a diode form between the light emitting element.

By such a configuration, the present invention minimizes the variation of the current supplied to the light emitting device due to the non-uniform threshold voltage of the transistor supplying the current to the light emitting device. Accordingly, the present invention can prevent the deterioration of image quality by making the overall luminance of each pixel uniform.

Description

Pixel and light emitting display device having the same {PIXEL AND LIGHT EMITTING DISPLAY HAVING THE SAME}             

1 is a diagram illustrating a pixel of a general light emitting display device.

2 is a graph illustrating a current supplied to a light emitting device according to a variation of a threshold voltage of a transistor in a general light emitting display device.

3 is a diagram illustrating a light emitting display device according to a first embodiment of the present invention.

4 is a diagram illustrating a pixel illustrated in FIG. 3.

FIG. 5 is a circuit diagram illustrating a pixel having the switching unit illustrated in FIG. 4 including a P-type transistor.

FIG. 6 is an equivalent diagram illustrating resistance components of a second transistor, a diode transistor, and a light emitting device of each pixel illustrated in FIG. 5.

FIG. 7 is a graph illustrating a current supplied to a light emitting device according to a threshold voltage variation of a second transistor in the light emitting display device according to the first embodiment of the present invention.

8 is a diagram illustrating each pixel of a light emitting display device according to a second embodiment of the present invention.

9 is a circuit diagram illustrating a pixel having a switching unit illustrated in FIG. 8 including a P-type transistor.

10 is a diagram illustrating a light emitting display device according to a second embodiment of the present invention.

FIG. 11 is a diagram illustrating a pixel illustrated in FIG. 10.

FIG. 12 is a circuit diagram illustrating a pixel having the switching unit illustrated in FIG. 11 including a P-type transistor.

13 is a diagram illustrating each pixel of a light emitting display device according to a fourth embodiment of the present invention.

FIG. 14 is a circuit diagram illustrating a pixel having the switching unit illustrated in FIG. 13 including a P-type transistor.

15 is a diagram illustrating each pixel of a light emitting display device according to a fifth embodiment of the present invention.

FIG. 16 is a circuit diagram illustrating a pixel having the switching unit illustrated in FIG. 15 including a P-type transistor.

17 is a diagram illustrating each pixel of a light emitting display device according to a sixth embodiment of the present invention.

18 is a diagram illustrating each pixel of a light emitting display device according to a seventh embodiment of the present invention.

19 is a circuit diagram illustrating a pixel having a switching unit illustrated in FIG. 18 including a P-type transistor.

20 is a diagram illustrating each pixel of a light emitting display device according to an eighth embodiment of the present invention.

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

21,121,221,321,421: Pixel 25,125,225,325,425: Switching unit

110: image display unit 130: scan driver

140: data driver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting display device, and more particularly, to a pixel and a light emitting display device having the same so as to prevent luminance unevenness and image quality deterioration due to variations in threshold voltage of a transistor.

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 the flat panel displays, a light emitting display is a self-light emitting device that emits a fluorescent material by recombination of electrons and holes. The organic light emitting display includes an inorganic light emitting display including an organic light emitting layer and an organic light emitting layer according to materials and structures. It is roughly classified as a device. In this case, the light emitting display device may be referred to as an electroluminescent display device.

Such a light emitting display device has an advantage of having a fast response speed, such as a cathode ray tube, compared to a passive light emitting device requiring a separate light source like a liquid crystal display device.

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

Referring to FIG. 1, a pixel 21 of a general light emitting display device includes a light emitting element OLED and a switching unit 25.

The switching unit 25 is electrically connected to the data line D, the scan line S, and the first power supply VDD. In addition, the switching unit 25 includes first and second transistors M1 and M2 and a capacitor C.

The gate electrode of the first transistor M1 is electrically connected to the scan line S. The source electrode of the first transistor M1 is electrically connected to the data line D, and the drain electrode is electrically connected to the first node N1. The first transistor M1 supplies the data signal from the data line D to the first node N1 in response to the scan signal supplied to the scan line S. FIG.

The capacitor C is electrically connected between the first node N1 and the first power source VDD. The capacitor C stores a voltage corresponding to the data signal supplied on the first node N1 through the first transistor M1 in a section in which the scan signal is supplied to the scan line S, and then stores the first voltage. When the transistor M1 is off, the on state of the second transistor M2 is maintained for one frame.

The gate electrode of the second transistor M2 is electrically connected to the first node N1 to which the drain electrode of the first transistor M1 and the capacitor C are commonly connected. The source electrode of the second transistor M2 is electrically connected to the first power supply VDD, and the drain electrode is electrically connected to the anode electrode of the light emitting device OLED. The second transistor M2 adjusts the amount of current supplied from the first power supply VDD to the light emitting device OLED according to the voltage from the capacitor C. FIG.

The anode electrode of the light emitting element OLED is electrically connected to the drain electrode of the second transistor M2, and the cathode electrode is electrically connected to the second power source VSS. Here, when the second transistor M2 is configured as a P-type transistor, the second power source VSS may have a lower voltage level than the first power source VDD and have a ground voltage level.

As such, the light emitting device OLED emits light according to the current supplied from the switching unit 25 to display an image. Here, the light emitting device OLED may be an organic light emitting device. The organic light emitting diode includes an emission layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) of an organic material formed between the anode electrode and the cathode electrode. The organic light emitting diode may further include an electron injection layer (EIL) and a hole injection layer (HIL). In the organic light emitting diode, when a voltage is applied between the anode electrode and the cathode electrode, electrons generated from the cathode electrode move toward the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode electrode are transferred to the hole injection layer and the hole transport layer. It moves to the light emitting layer through. Accordingly, in the light emitting layer, light is generated by collision between electrons and holes supplied from the electron transporting layer and the hole transporting layer and recombination.

In such a light emitting display device, the threshold voltage characteristic of the second transistor M2 for each pixel 21 is changed due to the irradiation direction of the laser used to form the semiconductor layer and the uneven energy distribution of the laser. Accordingly, in the case where the threshold voltage of the second transistor M2 is uneven in each pixel 21, streaks or spots may occur, resulting in uneven luminance and image quality.

2 is a graph illustrating a current supplied to a light emitting device according to a variation of a threshold voltage of a transistor in a general light emitting display device.

Referring to FIG. 2, the current supplied to the light emitting device OLED with respect to a data voltage varying from 3.5V to 1.5V in a typical light emitting display device is rapidly increased when the data signal changes from 3.5V to 1.5V. I can see that. Accordingly, it can be seen that the magnitude of the current supplied to the light emitting device OLED also increases rapidly as the threshold voltage Vth of the second transistor M2 changes. That is, it is seen that the current supplied to the light emitting device OLED rapidly increases as the threshold voltage (Vth: A line) of the second transistor M2 is increased by 0.1V fluctuating B line and -0.1V fluctuating C line. Can be.

Accordingly, an object of the present invention is to provide a pixel and a light emitting display device having the same so as to prevent luminance unevenness and deterioration in image quality due to threshold voltage unevenness of the transistor.

In addition, another object of the present invention is to provide a pixel and a light emitting display device having the same to increase the voltage range of the data signal for gray scale representation.

As a technical means for achieving the above object, the first aspect of the present invention is a switching unit for outputting a current corresponding to the data signal supplied to the data line in accordance with the scan signal supplied to the scan line, the current supplied from the switching unit There is provided a pixel including a light emitting element emitting light by means of a transistor connected between the switching unit and the light emitting element in a diode form.

Preferably, the diode-type transistor is characterized in that any one of the P type and N type. The calcination is controlled by a light emission control signal supplied to a light emission control line, and further includes a switching element electrically connected between the transistor and the light emitting element to form a current path between the transistor and the light emitting element.

A second aspect of the present invention includes a plurality of pixels defined by a plurality of scan lines, a plurality of data lines, and a plurality of power supply lines, each pixel being connected to the data line in accordance with a scan signal supplied to the scan line. A switching unit for outputting a current corresponding to the supplied data signal from the power supply line, a light emitting element emitting light by the current supplied from the switching unit, and a transistor connected in a diode form between the switching unit and the light emitting element Provided is a light emitting display device.

Preferably, the transistor is characterized in that any one of the P type and N type. The light emitting display device further includes a light emission control line for supplying a light emission control signal to each pixel. In addition, each of the pixels is controlled according to the light emission control signal, and further includes a switching device electrically connected between the transistor and the light emitting device to form a current path between the transistor and the light emitting device. The light emitting display further includes a data driver for supplying the data signal to the data line and a scan driver for supplying the scan signal to the scan line.

Hereinafter, a preferred embodiment of the present invention to which the present invention pertains will be described in detail with reference to FIGS. 3 to 20.

3 is a diagram illustrating a light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 3, the light emitting display device according to the first embodiment of the present invention includes an image display unit 110, a scan driver 130, and a data driver 140. In addition, the light emitting display device according to the first embodiment of the present invention further includes a power supply unit (not shown) for supplying a first power source and a second power source different from the first power source to the image display unit 110.

The image display unit 110 includes a plurality of pixels 121 defined by a plurality of scan lines S1 to SN and a plurality of data lines D1 to DM.

Each pixel 121 is selected according to a scan signal supplied to the scan lines S1 to SN, and receives light corresponding to a data signal supplied to the data lines D1 to DM.

The scan driver 130 generates scan signals for sequentially driving the scan lines S1 to SN in response to scan control signals from a controller (not shown), that is, a start pulse and a clock signal, thereby scanning the scan lines S1 to SN. ) Sequentially.

The data driver 130 supplies data signals from the controller to the data lines D1 to DM in response to data control signals supplied from the controller.

4 is a diagram illustrating a pixel of a light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 4, each pixel 121 of the light emitting display device according to the first embodiment of the present invention includes a light emitting element OLED, a switching unit 125, and a diode transistor Md.

The switching unit 125 is electrically connected to the data line D, the scan line S, the first power supply V1, and the diode-type transistor Md. The switching unit 125 outputs a current corresponding to the data signal supplied to the data line D from the first power supply V1 to the diode transistor Md in response to the scan signal supplied to the scan line S. do. In this case, the switching unit 125 includes at least two transistors and at least one capacitor. Here, the transistor may be a P-type or N-type metal oxide semiconductor field effect transistor (MOSFET), which will be described below using an example of a P-type transistor.

The diode-type transistor Md is a P-type transistor and includes a source electrode electrically connected to the switching unit 125, a drain electrode electrically connected to the light emitting element OLED, and a gate electrically connected to the drain electrode thereof. An electrode is provided. The diode-type transistor Md is a resistor connected in the form of a diode between the switching unit 125 and the light emitting element OLED to limit the current flowing from the switching unit 125 to the light emitting element OLED.

The anode electrode of the light emitting element OLED is electrically connected to the drain electrode of the diode transistor Md, and the cathode electrode is electrically connected to the second power source V2. Here, when the switching unit 125 is configured of a P-type transistor, the second power source V2 may have a lower voltage level than the first power source V1 and may have a ground voltage level.

As such, the light emitting device OLED emits light by a current corresponding to the data signal supplied from the switching unit 125 through the diode-type transistor Md to display an image. Here, the light emitting device OLED may be an organic light emitting device. The organic light emitting diode includes an emission layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) of an organic material formed between the anode electrode and the cathode electrode. The organic light emitting diode may further include an electron injection layer (EIL) and a hole injection layer (HIL). In the organic light emitting diode, when a voltage is applied between the anode electrode and the cathode electrode, electrons generated from the cathode electrode move toward the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode electrode are transferred to the hole injection layer and the hole transport layer. It moves to the light emitting layer through. Accordingly, in the light emitting layer, light is generated by collision between electrons and holes supplied from the electron transporting layer and the hole transporting layer and recombination.

FIG. 5 is a circuit diagram illustrating a pixel 121 having the switching unit 125 illustrated in FIG. 3 including a P-type transistor.

5 and 4, the switching unit 125 of each pixel 121 includes first and second transistors M1 and M2 and a capacitor C. Referring to FIG.

The gate electrode of the first transistor M1 is electrically connected to the scan line Sn. The source electrode of the first transistor M1 is electrically connected to the data line Dm, and the drain electrode is electrically connected to the first node N1. The first transistor M1 supplies the data signal from the data line Dm to the first node N1 in response to the scan signal supplied to the scan line Sn.

The capacitor C is electrically connected between the first node N1 and the first power source VDD. The capacitor C stores a voltage corresponding to the data signal supplied on the first node N1 through the first transistor M1 in a section in which the scan signal is supplied to the scan line Sn, and then the first When the transistor M1 is off, the on state of the second transistor M2 is maintained for one frame.

The gate electrode of the second transistor M2 is electrically connected to the first node N1 to which the drain electrode of the first transistor M1 and the capacitor C are commonly connected. The source electrode of the second transistor M2 is electrically connected to the first power source VDD, and the drain electrode is electrically connected to the source electrode of the diode transistor Md. The second transistor M2 adjusts the amount of current output from the first power supply VDD to the diode-type transistor Md according to the voltage from the capacitor C.

As described above, the switching unit 125 of each pixel 121 uses the first and second transistors M1 and M2 and the capacitor C in accordance with the scan signal supplied to the scan line Sn to the data line Dm. The current corresponding to the data signal supplied to is outputted from the first power supply VDD to the diode transistor Md.

FIG. 6 is an equivalent diagram illustrating resistance components of the second transistor M2, the diode transistor Md, and the light emitting diode OLED of each pixel 121 illustrated in FIG. 5.

Referring to FIG. 6, the voltage applied to the equivalent resistance component Rm2 of the second transistor M2 in each pixel 121 is equivalent to the resistance component Rmd and the light emitting diode OLED of the diode transistor Md. It is limited by the equivalent resistance component (Rled) of. In this case, the absolute value of the threshold voltage of the diode-type transistor Md preferably has a magnitude similar to the absolute value of the threshold voltage of the second transistor M2. Accordingly, even when the threshold voltage Vth of the second transistor M2 changes, the change in the current supplied to the light emitting device OLED is limited by the diode-type transistor Md and minimized.

FIG. 7 is a graph illustrating a current supplied to a light emitting device according to a threshold voltage variation of a second transistor in the light emitting display device according to the first embodiment of the present invention.

Referring to FIG. 7 and FIG. 6, the current supplied to the light emitting device OLED is limited by the diode-type transistor Md to the light emitting device OLED according to the variation of the threshold voltage Vth of the second transistor M2. It can be seen that the magnitude of the supplied current is also reduced. That is, the current curves A, B, and C supplied to the light emitting device OLED are formed on the B line of which the threshold voltage (Vth: A line) of the second transistor M2 is changed by 0.1 V and the C line of which -0.1 V is changed. You can see that it has a gentle slope as

In addition, since the current supplied to the light emitting device OLED is limited by the diode-type transistor Md, the voltage range of the data signal is greatly increased from 3.5V to 1.2V. Accordingly, since the voltage range of the data signal is greatly increased, the number of gray levels of the image due to the light emission of the light emitting element OLED can be increased.

Accordingly, the light emitting display device according to the first embodiment of the present invention is limited in the variation of the threshold voltage Vth of the second transistor M2 by limiting the current supplied to the light emitting device OLED by the diode-type transistor Md. This can minimize the influence of the current supplied to the light emitting device (OLED). As a result, the light emitting display device according to the first embodiment of the present invention can prevent the luminance unevenness and the deterioration of image quality due to the nonuniformity of the threshold voltage Vth of the second transistor M2.

8 is a diagram illustrating each pixel 121 of the light emitting display device according to the second embodiment of the present invention.

Referring to FIG. 8, each pixel 121 of the light emitting display device according to the second embodiment of the present invention includes a light emitting device OLED, a switching unit 125, and a diode transistor Md. Here, each pixel 121 of the light emitting display according to the second embodiment of the present invention has the same structure as the first embodiment of the present invention shown in FIG. 4 except for the diode-type transistor Md. Accordingly, in the second embodiment of the present invention, the description of the other components except for the diode-type transistor Md will be replaced with the description of the first embodiment.

In each pixel 121 of the light emitting display according to the second exemplary embodiment of the present invention, the diode-type transistor Md is an N-type transistor, a source electrode electrically connected to the switching unit 125, and a light emitting device OLED. And a drain electrode electrically connected to the gate electrode, and a gate electrode electrically connected to its source electrode. The diode-type transistor Md limits the current flowing from the switching unit 125 connected to the light emitting device OLED in the form of a diode between the switching unit 125 and the light emitting device OLED.

FIG. 9 is a circuit diagram illustrating a pixel 121 having the switching unit 125 illustrated in FIG. 8 including a P-type transistor.

9 and 8, the switching unit 125 of each pixel 121 includes first and second transistors M1 and M2 and a capacitor C. Referring to FIG. Here, since the switching unit 125 has the same structure as that of the first embodiment of the present invention shown in FIG. 5, it will be replaced with the description of the first embodiment.

As described above, each pixel 121 of the light emitting display device according to the first and second embodiments of the present invention removes the gate electrode of the diode transistor Md according to the P type and the N type of the diode transistor Md. It is electrically connected to any one of the two transistors M2 and the light emitting element OLED. That is, in the case of a P-type transistor, the gate electrode of the diode-type transistor Md is electrically connected to its drain electrode (or the anode electrode of the light emitting element OLED), and in the case of an N-type transistor, the diode-type transistor Md Gate electrode is electrically connected to its source electrode (or the drain electrode of the second transistor M2).

10 is a diagram illustrating a light emitting display device according to a third embodiment of the present invention.

Referring to FIG. 10, the light emitting display device according to the third exemplary embodiment includes an image display unit 110, a scan driver 130, and a data driver 140. In addition, the light emitting display device according to the third embodiment of the present invention further includes a power supply unit (not shown) for supplying a first power source and a second power source different from the first power source to the image display unit 110.

The image display unit 110 includes a plurality of pixels 221 defined by a plurality of scan lines S1 to SN, a plurality of data lines D1 to DM, and emission control lines E1 to EN.

Each pixel 221 is selected according to the scan signals supplied to the scan lines S1 to SN, and the data signals supplied to the data lines D1 to DM according to the emission control signals supplied to the emission control lines E1 to EN. It emits light by receiving the current corresponding to.

The scan driver 130 generates scan signals for sequentially driving the scan lines S1 to SN in response to scan control signals from a controller (not shown), that is, a start pulse and a clock signal, thereby scanning the scan lines S1 to SN. ) Sequentially. In addition, the scan driver 130 generates light emission control signals for sequentially driving the light emission control lines E1 to EN and sequentially supplies them to the light emission control lines E1 to EN.

The data driver 130 supplies data signals from the controller to the data lines D1 to DM in response to data control signals supplied from the controller.

11 is a diagram illustrating each pixel 221 of a light emitting display device according to a third embodiment of the present invention.

Referring to FIG. 11, each pixel 221 of the light emitting display device according to the third embodiment of the present invention includes a light emitting device OLED, a switching unit 225, a diode-type transistor Md, and a switching device SW. Include.

The light emitting device OLED emits light by a current corresponding to a data signal supplied from the switching unit 225 through the diode-type transistor Md and the switching device SW to display an image.

The switching unit 225 is electrically connected to the data line Dm, the scan line Sn, the first power supply V1, and the diode-type transistor Md. The switching unit 225 outputs a current corresponding to the data signal supplied to the data line Dm from the first power supply V1 to the diode transistor Md in response to the scan signal supplied to the scan line Sn. do. At this time, the switching unit 225 is composed of at least two transistors and at least one capacitor. Here, the transistor may be a P-type or N-type metal oxide semiconductor field effect transistor (MOSFET), which will be described below using the P-type transistor as an example.

The diode-type transistor Md is a P-type transistor, which is a source electrode electrically connected to the switching unit 125, a drain electrode electrically connected to the switching element SW, and a gate electrically connected to the drain electrode thereof. An electrode is provided. The diode-type transistor Md limits the current flowing through the light emitting device OLED from the switching unit 225 connected in a diode form between the switching unit 225 and the switching device SW.

The switching element SW is electrically connected to a gate electrode electrically connected to the emission control line E, a source electrode electrically connected to the drain electrode of the diode-type transistor Md, and an anode electrode of the light emitting element OLED. It is a P type transistor having a drain electrode. The switching element SW supplies the current supplied from the diode-type transistor Md to the anode electrode of the light emitting element OLED according to the light emission control signal supplied to the light emission control line E.

The anode electrode of the light emitting element OLED is electrically connected to the output terminal of the switching element SW, and the cathode electrode is electrically connected to the second power source V2. In this case, when the switching unit 225 is configured of a P-type transistor, the second power source V2 may have a lower voltage level than the first power source V1 and may have a ground voltage level. The light emitting device OLED emits light by a current supplied from the second transistor M2 through the switching device SW during the period in which the switching device SW is turned on to display an image.

FIG. 12 is a circuit diagram illustrating a pixel 221 having a switching unit 225 shown in FIG. 11 including a P-type transistor.

12, the switching unit 225 of each pixel 221 includes first and second transistors M1 and M2 and a capacitor C. Referring to FIG.

The gate electrode of the first transistor M1 is electrically connected to the scan line Sn. The source electrode of the first transistor M1 is electrically connected to the data line Dm, and the drain electrode is electrically connected to the first node N1. The first transistor M1 supplies the data signal from the data line Dm to the first node N1 in response to the scan signal supplied to the scan line Sn.

The capacitor C is electrically connected between the first node N1 and the first power source VDD. The capacitor C stores a voltage corresponding to the data signal supplied on the first node N1 through the first transistor M1 in a section in which the scan signal is supplied to the scan line Sn, and then the first When the transistor M1 is off, the on state of the second transistor M2 is maintained for one frame.

The gate electrode of the second transistor M2 is electrically connected to the first node N1 to which the drain electrode of the first transistor M1 and the capacitor C are commonly connected. The source electrode of the second transistor M2 is electrically connected to the first power source VDD, and the drain electrode is electrically connected to the source electrode of the diode transistor Md. The second transistor M2 adjusts the amount of current output from the first power supply VDD to the diode-type transistor Md according to the voltage from the capacitor C.

As described above, the switching unit 125 of each pixel 121 uses the first and second transistors M1 and M2 and the capacitor C in accordance with the scan signal supplied to the scan line Sn to the data line Dm. The current corresponding to the data signal supplied to is outputted from the first power supply VDD to the diode transistor Md.

13 is a diagram illustrating each pixel 221 of a light emitting display device according to a fourth embodiment of the present invention.

Referring to FIG. 13, each pixel 221 of the light emitting display device according to the fourth embodiment of the present invention includes a light emitting device OLED, a switching unit 225, a diode-type transistor Md, and a switching device SW. Include. Here, each pixel 221 of the light emitting display according to the fourth embodiment of the present invention has the same structure as the third embodiment of the present invention shown in FIG. 11 except for the diode-type transistor Md. Accordingly, in the fourth embodiment of the present invention, the description of the other components except for the diode-type transistor Md will be replaced with the description of the third embodiment.

In each pixel 221 of the light emitting display according to the fourth embodiment of the present invention, the diode-type transistor Md is an N-type transistor, a source electrode electrically connected to the switching unit 225, and a light emitting element OLED. And a drain electrode electrically connected to the gate electrode, and a gate electrode electrically connected to its source electrode. The diode-type transistor Md limits the current flowing through the light emitting device OLED from the switching unit 225 connected in a diode form between the switching unit 225 and the light emitting device OLED.

FIG. 14 is a circuit diagram illustrating a pixel 221 having the switching unit 225 shown in FIG. 13 including a P-type transistor.

Referring to FIG. 14 and FIG. 13, the switching unit 225 of each pixel 221 includes first and second transistors M1 and M2 and a capacitor C. Referring to FIG. Here, since the switching unit 225 has the same structure as that of the third embodiment of the present invention shown in FIG. 13, it will be replaced with the description of the above-described third embodiment.

As described above, each pixel 221 of the light emitting display device according to the third and fourth exemplary embodiments may remove the gate electrode of the diode transistor Md according to the P type and the N type of the diode transistor Md. It is electrically connected to either of the two transistors M2 and the switching element SW. That is, in the case of a P-type transistor, the gate electrode of the diode-type transistor Md is electrically connected to its drain electrode (or the drain electrode of the switching element SW), and in the case of an N-type transistor, the diode-type transistor Md Gate electrode is electrically connected to its source electrode (or the drain electrode of the second transistor M2).

15 is a diagram illustrating each pixel 321 of the light emitting display device according to the fifth embodiment of the present invention.

Referring to FIG. 15, each pixel 321 of the light emitting display device according to the fifth embodiment of the present invention includes a light emitting element OLED, a switching unit 325, a diode transistor Md, and a switching element SW. Include.

The light emitting device OLED emits light by a current corresponding to a data signal supplied from the switching unit 325 through the diode-type transistor Md and the switching device SW to display an image.

The switching unit 325 is electrically connected to the data line Dm, the first and second scan lines Sn-1 and Sn, the first power supply V1, and the diode transistor Md. The switching unit 325 receives a current corresponding to the data signal supplied to the data line Dm according to the first and second scan signals supplied to the first and second scan lines Sn-1 and Sn. It outputs from the power supply V1 to the diode transistor Md. At this time, the switching unit 325 is composed of at least two transistors and at least one capacitor. Here, the transistor may be a P-type or N-type metal oxide semiconductor field effect transistor (MOSFET), which will be described below using the P-type transistor as an example.

The diode-type transistor Md is a P-type transistor, which is a source electrode electrically connected to the switching unit 325, a drain electrode electrically connected to the switching element SW, and a gate electrically connected to the drain electrode thereof. An electrode is provided. The diode-type transistor Md limits the current flowing through the light emitting device OLED from the switching unit 325 connected in a diode form between the switching unit 325 and the switching device SW.

The switching element SW is electrically connected to a gate electrode electrically connected to the emission control line E, a source electrode electrically connected to the drain electrode of the diode-type transistor Md, and an anode electrode of the light emitting element OLED. It is a P type transistor having a drain electrode. The switching element SW supplies the current supplied from the diode-type transistor Md to the anode electrode of the light emitting element OLED in accordance with the light emission control signal supplied to the light emission control line E.

The anode electrode of the light emitting element OLED is electrically connected to the output terminal of the switching element SW, and the cathode electrode is electrically connected to the second power source V2. In this case, when the switching unit 325 is configured of a P-type transistor, the second power source V2 may have a lower voltage level than the first power source V1 and may have a ground voltage level. The light emitting device OLED emits light by a current supplied from the second transistor M2 through the switching device SW during the period in which the switching device SW is turned on to display an image.

FIG. 16 is a circuit diagram illustrating a pixel 321 having the switching unit 325 illustrated in FIG. 15 including a P-type transistor.

Referring to FIG. 16 and FIG. 15, the switching unit 325 of each pixel 321 includes first to fourth transistors M1 to M4 and first and second capacitors C1 and C2.

The gate electrode of the first transistor M1 is electrically connected to the Nth scan line Sn. The source electrode of the first transistor M1 is electrically connected to the data line Dm, and the drain electrode is electrically connected to the first node N1. The first transistor M1 supplies the data signal from the data line Dm to the first node N1 in response to the first scan signal supplied to the Nth scan line Sn.

The gate electrode of the second transistor M2 is electrically connected to the second node N2. The source electrode of the second transistor M2 is electrically connected to the first power supply VDD, and the drain electrode is electrically connected to the diode transistor Md through the third node N3. The second transistor M2 outputs a current corresponding to the voltage between its gate and source from the first power supply VDD to the diode transistor Md.

The gate electrode of the third transistor M3 is electrically connected to the N-1th scan line Sn-1. The source electrode of the third transistor is electrically connected to the second node N2, and the drain electrode is electrically connected to the third node N3. The third transistor M3 connects the second transistor M2 in the form of a diode in response to the second scan signal supplied to the N-1 scan line Sn-1.

The gate electrode of the fourth transistor M4 is electrically connected to the N-th scan line Sn-1. The source electrode of the fourth transistor M4 is electrically connected to the first power supply VDD, and the drain electrode is electrically connected to the first node N1. The fourth transistor M4 supplies the voltage from the first power supply VDD to the first node N1 in response to the second scan signal supplied to the N-1 scan line Sn-1.

The first capacitor C1 includes a first electrode electrically connected to the first power supply VDD and a second electrode electrically connected to the first node N1. The first capacitor C1 stores a data signal supplied on the first node N1 through the first transistor M1 in a section in which the first scan signal is supplied to the Nth scan line Sn. When the first transistor M1 is turned off, the stored voltage is supplied to the gate electrode of the second transistor M2.

The second capacitor C2 corresponds to the threshold voltage Vth of the second transistor M2 from the first power supply VDD in a period where the second scan signal is supplied to the N-1 scan line Sn-1. Save it. That is, the second capacitor C2 stores a compensation voltage for compensating the threshold voltage Vth of the second transistor M2 according to the switching of the third and fourth transistors M3 and M4.

As described above, the switching unit 325 of each pixel 321 uses the first to fourth transistors M1 to M4 and the first and second capacitors C1 and C2 to provide the first and second scan lines Sn, The current corresponding to the data signal supplied to the data line Dm is output from the first power supply VDD to the diode transistor Md in accordance with the first and second scan signals supplied to Sn-1.

17 is a diagram illustrating each pixel 321 of a light emitting display device according to a sixth embodiment of the present invention.

Referring to FIG. 17, each pixel 321 of the light emitting display device according to the sixth exemplary embodiment of the present invention includes a light emitting device OLED, a switching unit 325, a diode transistor Md, and a switching device SW. Include. Here, each pixel 321 of the light emitting display according to the sixth embodiment of the present invention has the same structure as the fifth embodiment of the present invention shown in FIG. 15 except for the diode-type transistor Md. Accordingly, in the sixth embodiment of the present invention, the description of other components except for the diode-type transistor Md will be replaced with the description of the fifth embodiment.

In each pixel 321 of the light emitting display according to the sixth exemplary embodiment, the diode-type transistor Md is an N-type transistor, a source electrode electrically connected to the switching unit 325, and a light emitting device OLED. And a drain electrode electrically connected to the gate electrode, and a gate electrode electrically connected to its source electrode. Such a diode-type transistor Md restricts a current flowing through the light emitting device OLED from the switching unit 325 connected in a diode form between the switching unit 325 and the light emitting device OLED.

Meanwhile, in each pixel 321 of the light emitting display device according to the sixth exemplary embodiment, the switching unit 325 includes four transistors and two capacitors, as shown in FIG. 16. The detailed description of the switching unit 325 will be replaced with the description of FIG. 16.

18 is a diagram illustrating each pixel 421 of the light emitting display device according to the seventh exemplary embodiment.

Referring to FIG. 18, each pixel 421 of the light emitting display device according to the seventh embodiment of the present invention includes a light emitting device OLED, a switching unit 425, a diode-type transistor Md, and a switching device SW. Include.

The light emitting device OLED emits light by a current corresponding to a data signal supplied from the switching unit 425 through the diode-type transistor Md and the switching device SW to display an image.

The switching unit 425 is electrically connected to the data line Dm, the first and second scan lines Sn-1 and Sn, the light emission control line En, the first power supply V1, and the diode-type transistor Md. do. The switching unit 425 may include the first and second scan signals supplied to the first and second scan lines Sn-1 and Sn and the emission control signal supplied to the emission control line En. A current corresponding to the data signal supplied to Dm) is output from the first power supply V1 to the diode transistor Md. In this case, the switching unit 425 is composed of at least two transistors and at least one capacitor. Here, the transistor may be a P-type or N-type metal oxide semiconductor field effect transistor (MOSFET), which will be described below using the P-type transistor as an example.

The diode-type transistor Md is a P-type transistor, which is electrically connected to a source electrode electrically connected to the switching unit 425, a drain electrode electrically connected to the switching element SW, and a drain electrode thereof. A gate electrode is provided. The diode-type transistor Md limits the current flowing through the light emitting device OLED from the switching unit 425 which is connected in a diode form between the switching unit 425 and the switching device SW.

The switching element SW is electrically connected to a gate electrode electrically connected to the emission control line E, a source electrode electrically connected to the drain electrode of the diode-type transistor Md, and an anode electrode of the light emitting element OLED. It is a P type transistor having a drain electrode. The switching element SW supplies a current supplied from the diode-type transistor Md to the anode electrode of the light emitting element OLED according to the light emission control signal supplied to the light emission control line En.

The anode electrode of the light emitting element OLED is electrically connected to the output terminal of the switching element SW, and the cathode electrode is electrically connected to the second power source V2. In this case, when the switching unit 425 is configured of a P-type transistor, the second power source V2 may have a lower voltage level than the first power source V1 and may have a ground voltage level. The light emitting device OLED emits light by a current supplied from the second transistor M2 through the switching device SW during the period in which the switching device SW is turned on to display an image.

19 is a circuit diagram illustrating a pixel 421 having a switching unit 425 shown in FIG. 18 including a P-type transistor.

Referring to FIG. 19 and FIG. 18, the switching unit 425 of each pixel 421 includes first to fifth transistors M1 to M5 and a capacitor C1.

The gate electrode of the first transistor M1 is electrically connected to the first scan line Sn. The source electrode of the first transistor M1 is electrically connected to the data line Dm, and the drain electrode is electrically connected to the first node N1. The first transistor M1 is turned on when the first scan signal is supplied to the first scan line Sn and supplies the data signal supplied from the data line Dm to the first node N1.

It is electrically connected to the first electrode of the capacitor C through the second node N2 of the second transistor M2. The source electrode of the second transistor M2 is electrically connected to the first node N1, and the drain electrode is electrically connected to the source electrode of the diode transistor Md. The second transistor M2 supplies a current corresponding to the voltage charged in the capacitor C to the diode-type transistor Md.

The gate electrode of the third transistor M3 is electrically connected to the first scan line Sn. The source electrode of the third transistor M3 is electrically connected to the second node N2, that is, the gate electrode of the second transistor M2, and the drain electrode is a drain electrode and a diode type of the second transistor M2. It is commonly connected to the source electrode of the transistor Md. The third transistor M3 is turned on when the first scan signal is supplied to the first 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 gate electrode of the fourth transistor M4 is electrically connected to the light emission control line E. FIG. The source electrode of the fourth transistor M4 is electrically connected to the first power source VDD, and the drain electrode is electrically connected to the first node N1. The fourth transistor M4 electrically connects the first power source VDD to the first node N1 according to the emission control signal supplied to the emission control line En.

The gate electrode of the fifth transistor M5 is electrically connected to the second scan line Sn-1. The source electrode of the fifth transistor M5 is electrically connected to the first electrode of the capacitor C, and the drain electrode is electrically connected to the second scan line Sn-1. That is, the gate electrode and the drain electrode of the fifth transistor M5 are connected to the second scan line Sn-1 in common, thereby being in a diode-type connection state. The fifth transistor M5 is turned on when the second scan signal is supplied to the second scan line Sn- 1 to supply the second scan signal to the second node N2. Accordingly, the fifth transistor M6 initializes the gate electrodes of the capacitor C and the second transistor M2 using the second scan signal supplied to the second scan line Sn-1.

The capacitor C has a first electrode electrically connected to the second node N2 and a second electrode electrically connected to the first power source VDD. The capacitor C is initialized by the second scan signal supplied to the second scan line Sn-1. The capacitor C receives a voltage corresponding to the data signal from the data line Dm through the first and second transistors M1 and M2 in a section in which the first scan signal is supplied to the first scan line Sn. After storing, when the first transistor M1 is turned off, the second transistor M2 is maintained in the on state by using the stored voltage.

As described above, the switching unit 425 of each pixel 421 is supplied to the first and second scan lines Sn-1 and Sn by using the first to fifth transistors M1 to M5 and the capacitor C. In response to the light emission control signal supplied to the first and second scan signals and the light emission control line En, a current corresponding to the data signal supplied to the data line Dm is supplied from the first power source V1 to the diode transistor Md. Will be printed.

20 is a diagram illustrating each pixel 421 of the light emitting display device according to the eighth embodiment.

Referring to FIG. 20, each pixel 421 of the light emitting display device according to the eighth exemplary embodiment may include a light emitting device OLED, a switching unit 425, a diode transistor Md, and a switching device SW. Include. Here, each pixel 421 of the light emitting display device according to the eighth exemplary embodiment has the same structure as the seventh exemplary embodiment of the present invention illustrated in FIG. 18 except for the diode-type transistor Md. Accordingly, in the eighth embodiment of the present invention, the description of other components except for the diode-type transistor Md will be replaced with the description of the seventh embodiment.

In each pixel 421 of the light emitting display according to the eighth embodiment, the diode-type transistor Md is an N-type transistor, a source electrode electrically connected to the switching unit 425, and a light emitting element OLED. And a drain electrode electrically connected to the gate electrode, and a gate electrode electrically connected to its source electrode. The diode-type transistor Md limits the current flowing through the light emitting device OLED from the switching unit 425 which is connected in a diode form between the switching unit 425 and the light emitting device OLED.

On the other hand, in each pixel 421 of the light emitting display device according to the eighth embodiment of the present invention, the switching unit 425 is composed of five transistors M1 to M5 and one capacitor C as shown in FIG. 19. It is composed. Such a detailed description of the switching unit 425 will be replaced with the description of FIG. 19.

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, the pixel and the light emitting display device having the same according to the exemplary embodiment of the present invention can change the current supplied to the light emitting device due to the non-uniform threshold voltage of the transistor supplying the current to the light emitting device. Will be minimized. Accordingly, the present invention can prevent the deterioration of image quality by making the overall luminance of each pixel uniform.

Claims (14)

A switching unit for outputting a current corresponding to the data signal supplied to the data line according to the scan signal supplied to the scan line; A light emitting device that emits light by a current supplied from the switching unit, A transistor connected in a diode form between the switching unit and the light emitting element, The switching unit, A first transistor controlled by a first scan signal supplied to a first scan line and supplying the data signal to a first node; A second transistor driven by a voltage between its gate and source and outputting the current to the transistor; A third transistor controlled by a second scan signal supplied to a second scan line and connecting the second transistor in the form of a diode; A fourth transistor controlled by the second scan signal and supplying a first power source to the first node; A first capacitor connected between the first node and the first power source to store a voltage corresponding to the data signal; And a second capacitor connected between the first node and the gate electrode of the second transistor to store the threshold voltage of the second transistor. A switching unit for outputting a current corresponding to the data signal supplied to the data line according to the scan signal supplied to the scan line; A light emitting device that emits light by a current supplied from the switching unit, A transistor connected in a diode form between the switching unit and the light emitting element; A switching element controlled by an emission control signal supplied to an emission control line, the switching element being electrically connected between the transistor and the light emitting element to form a current path between the transistor and the light emitting element, The switching unit, A first transistor controlled by a first scan signal supplied to a first scan line and supplying the data signal to a first node; A second transistor driven by a voltage between its gate and source and outputting the current to the transistor; A third transistor controlled by the first scan signal and connecting the second transistor in the form of a diode; A fourth transistor controlled by the light emission control signal and supplying a first power source to the first node; A capacitor electrically connected between a second node connected to the gate electrode of the second transistor and the first power source to store a voltage corresponding to the data signal; And a fifth transistor controlled by a second scan signal supplied to a second scan line and connected to the second scan line in the form of a diode to supply the second scan signal to the second node. The method according to claim 1 or 2, And the transistor connected in the form of a diode is one of a P type and an N type. delete delete delete A plurality of pixels defined by a plurality of scanning lines, a plurality of data lines, and a plurality of power lines; Each pixel, A switching unit for outputting a current corresponding to the data signal supplied to the data line from the power supply line according to the scan signal supplied to the scan line; A light emitting element emitting light by the current supplied from the switching unit; A transistor connected in a diode form between the switching unit and the light emitting element, The switching unit, A first transistor controlled by a first scan signal supplied to a first scan line and supplying the data signal to a first node; A second transistor driven by a voltage between its gate and source and outputting the current to the transistor; A third transistor controlled by a second scan signal supplied to a second scan line and connecting the second transistor in the form of a diode; A fourth transistor controlled by the second scan signal and supplying a first power source to the first node; A first capacitor connected between the first node and the first power source to store a voltage corresponding to the data signal; And a second capacitor connected between the first node and the gate electrode of the second transistor to store the threshold voltage of the second transistor. A plurality of pixels defined by a plurality of scan lines, a plurality of data lines, and a plurality of power lines; An emission control line for supplying an emission control signal to each pixel; Each pixel, A switching unit for outputting a current corresponding to the data signal supplied to the data line from the power supply line according to the scan signal supplied to the scan line; A light emitting element emitting light by the current supplied from the switching unit; Comprising a transistor connected in the form of a diode between the switching unit and the light emitting element, The switching unit, A first transistor controlled by a first scan signal supplied to a first scan line and supplying the data signal to a first node; A second transistor driven by a voltage between its gate and source and outputting the current to the transistor; A third transistor controlled by the first scan signal and connecting the second transistor in the form of a diode; A fourth transistor controlled by the light emission control signal and supplying a first power source to the first node; A capacitor electrically connected between a second node connected to the gate electrode of the second transistor and the first power source to store a voltage corresponding to the data signal; And a fifth transistor controlled by a second scan signal supplied to a second scan line and connected to the second scan line in the form of a diode to supply the second scan signal to the second node. The method according to claim 7 or 8, And the transistor connected in the form of a diode is one of a P type and an N type. delete delete delete delete delete

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