Organic light-emitting diode display device and driving method thereof

The invention claims the benefit of Korean Patent Application No. P06-0056566 filed in Korea on Jun. 22, 2006, which is hereby incorporated by reference in its entirety.

1. Field of the Invention

The invention relates to an organic light-emitting diode display device, and more particularly, to an organic light-emitting diode display device and a driving method thereof. Although embodiments of the invention are suitable for a wide scope of applications, they are particularly suitable for reducing a residual image phenomenon and a motion image blurring phenomenon, and for compensating a voltage drop of a driving voltage in an organic light-emitting diode display device.

2. Discussion of the Related Art

Recently, flat display panels with reduced weight and size have been developed to eliminate disadvantages of a cathode ray tube display device. Such flat panel display devices include a liquid crystal display (hereinafter, referred to as “LCD”) device, a field emission display (hereinafter, referred to as “FED”) device, a plasma display panel (hereinafter, referred to as “PDP”) device, and an electro-luminescence (hereinafter, referred to as “EL”) display device.

In general, a PDP has been highlighted among flat panel display devices as advantageous to have light weight, a small size and a large dimension screen because its structure and manufacturing process are simple. However, a PDP has a low light-emission efficiency and requires large power consumption. Likewise, an active matrix LCD device employing a thin film transistor (hereinafter, referred to as “TFT”) as a switching device has experienced drawbacks in that it is difficult to make a large dimension screen because a semiconductor process is used, but has an expanded demand as it is mainly used for a display device of a notebook personal computer. On the other hand, an EL display device is largely classified into an inorganic EL display device and an organic light-emitting diode display device depending upon a material of a light-emitting layer. An EL display device also is advantageous in that it is self-luminous. When compared with the above-mentioned display devices, the EL device generally has a faster response speed, a higher light-emission efficiency, greater brightness and a wider viewing angle.

FIG. 1 is a schematic diagram illustrating a structure of an organic light-emitting diode display device according to the related art. In FIG. 1 , the organic light-emitting diode device includes an anode electrode ANODE made of a transparent conductive material on a glass substrate, and a cathode electrode CATHODE made of an organic compound layer and a conductive metal. The organic light-emitting diode device also includes an organic compound layer. The organic compound layer comprises a hole injection layer HIL, a hole transport layer HTL, an emission layer EML, an electron transport layer ETL, and an electron injection layer EIL.

When a driving voltage is applied to the anode electrode ANODE and the cathode electrode CATHODE, a hole within the hole injection layer and an electron within the electron injection layer respectively move forward the emission layer EML to excite the emission layer EML. As a result, the emission layer EML emits visible rays and the visible rays generated from the emission layer EML display a picture or a motion picture.

The above-described organic light-emitting diode device has been applied to a passive matrix type display device or to an active matrix type display using a TFT as a switching element. The passive matrix type display device crosses the anode electrode ANODE with the cathode electrode CATHODE to select a light-emitting cell in accordance with a current applied to the anode and cathode electrodes ANODE and CATHODE. On the other hand, the active matrix type display device selectively turns-on an active element, such as a TFT, to select a light-emitting cell, and maintains light-emission in the light-emitting cell using a voltage maintained at a storage capacitor.

FIG. 2 is a circuit diagram illustrating a pixel of an active matrix type organic light-emitting diode display device according to the related art. Referring to FIG. 2 , a pixel of an active matrix type organic light-emitting diode display device includes an organic light-emitting diode element OLED, a data line DL and a gate line GL that cross each other, a switch TFT T 2 , a driving TFT T 1 , and a storage capacitor Cst. The driving TFT T 1 and the switch TFT T 2 are made of a p-type MOS-FET.

The switch TFT T 2 is turned-on in response to a gate low-level voltage (or a scanning voltage) from the gate line GL to form a current path between a source electrode and a drain electrode of the switch TFT T 2 , and maintains an off-state when a voltage of the gate line GL is less than a threshold voltage (hereinafter, referred to as “Vth”), that is, a gate high-level voltage. A data voltage from the data line DL is applied, via the source electrode and the drain electrode of the switch TFT T 2 , to a gate electrode and the storage capacitor Cst of the driving TFT T 1 for an on-time period of the switch TFT T 2 . On the other hand, a current path between the source electrode and the drain electrode of the switch TFT T 2 is opened for an off-time period of the switch TFT T 2 . As a result, the data voltage is not applied to the driving TFT T 1 and the storage capacitor Cst.

In addition, the source electrode of the driving TFT T 1 is connected to a driving voltage line VL and the storage capacitor Cst, and the drain electrode of the driving TFT T 1 is connected to an anode electrode of the organic light-emitting diode element OLED. The gate electrode of the driving TFT T 1 is connected to the drain electrode of the switch TFT T 2 . The driving TFT T 1 adjusts a current amount between the source electrode and the drain electrode in accordance with the data voltage supplied to the gate electrode. As a result, the organic light-emitting diode element OLED emits brightness corresponding to the data voltage. Further, the storage capacitor Cst stores a difference voltage between the data voltage and a high-level driving voltage source VDD to maintain a constant voltage applied to the gate electrode of the driving TFT T 1 for one frame period.

The organic light-emitting diode element OLED shown in FIG. 2 has the structure as shown in FIG. 1 , and includes an anode electrode and a cathode electrode. The anode electrode of the organic light-emitting diode element OLED is connected to the drain electrode of the driving TFT T 1 , and the cathode electrode of the organic light-emitting diode element OLED is connected to a ground voltage source GND.

The brightness of a pixel as shown in FIG. 2 is in proportion to a current flowing into the organic light-emitting diode element OLED, and the current is adjusted by a voltage applied to the gate electrode of the driving TFT T 1 . In other words, a gate-source voltage |Vgs| between a gate electrode and a source element of the driving TFT T 1 must be increased in order to improve brightness of a pixel. On the other hand, the gate-source voltage |Vgs| must be decreased in order to darken brightness of a pixel.

FIG. 3A is a graph illustrating a hysteresis characteristic of a thin film transistor according to the related art, FIG. 3B is an amplified graph of a portion of the graph shown in FIG. 3 A, and FIG. 4 is a graph illustrating an example which an operating point of a thin film transistor is changed in accordance with a hysteresis characteristic. The driving TFT T 1 (shown in FIG. 2 ) has a hysteresis characteristic. As shown in FIGS. 3A and 3B , the hysteresis characteristics are generated as a current between a drain electrode and a source electrode I ds changes in accordance with a change of a gate-source voltage |Vgs|. For example, if brightness of a pixel is changed from a white gray scale level to a middle gray scale level, then the gate-source voltage |Vgs| of the driving TFT T 1 is changed from a high value to a low value. In this case, since a relatively high gate-source voltage |Vgs| is formerly applied to the driving TFT T 1 at the white gray scale level, if the gate-source voltage |Vgs| corresponding to the middle gray scale level is applied to the driving TFT T 1 at a state that a threshold voltage |Vth| of the driving TFT T 1 is increased, then an operating point of the driving TFT T 1 is changed as shown in “B” of FIG. 4 .

On the other hand, if brightness of a pixel is changed from a black gray scale level to the middle gray scale level, then the gate-source voltage |Vgs| of the driving TFT T 1 is changed from a low value to a high value. In this case, since a relative low gate-source voltage |Vgs| is formerly applied to the driving TFT T 1 at the black gray scale level, if a gate-source voltage |Vgs| corresponding to the middle gray scale level is applied to the driving TFT T 1 at a state that a threshold voltage |Vth| of the driving TFT T 1 is decreased, then an operating point of the driving TFT T 1 is changed as shown in “A” of FIG. 4 . Accordingly, although the same gate-source voltage |Vgs| is applied to the driving TFT T 1 to represent the same brightness of the middle gray scale level, different currents would flow to the organic light-emitting diode element OLED in accordance with a prior pixel brightness. Thus, a residual image is generated.

FIG. 5A is a diagram illustrating a test data according to the related art, FIG. 5B is a diagram illustrating an example of a residual image phenomenon after the test data shown in FIG. 5A is applied to the device shown in FIG. 2 . FIG. 5A illustrates a test data displayed on a display screen when no residual image is generated. The test data is to display the white gray scale level and the black gray scale level that are arranged in a check pattern corresponding to pixels that are arranged in the matrix type organic light-emitting diode display device shown in FIG. 2 . As shown in FIG. 5B , when a test data is applied to the organic light-emitting diode display device, a middle gray scale level data is instead displayed on the whole screen due to the hysteresis characteristic of the driving TFT.

Moreover, an active-type organic light-emitting diode display device according to the related art has a pixel configuration including TFTs and a storage capacitor as shown in FIG. 2 and is a hold type display. The hold type display device constantly maintains brightness of each pixel for each frame for one frame period as shown in FIG. 6 . Thus, brightness of each pixel for one frame period is maintained, thereby burring an image of a motion picture and causing motion blurring. On the other hand, an impulse type display device, such as a cathode ray tube, emits light from the pixel for a time of one frame period, and does not emit light from the pixel for another frame period. As a result, a motion blurring phenomenon is almost not perceived by the observer.

In the active-type organic light-emitting diode display device, a current and brightness of the organic light-emitting diode element OLED is differentiated at a data having the same gray scale level in accordance with a screen position by a voltage drop. The voltage drop is generated by a driving voltage line VL supplying the high-level electric driving voltage source to each of the pixels. This phenomenon worsens as the driving voltage line VL becomes longer in a large size panel.

Accordingly, embodiments of the invention is directed to an organic light-emitting diode display device and a driving method thereof employing the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

An object of embodiments of the invention is to provide an organic light-emitting diode display device and a driving method thereof that reduce display deterioration caused by a thin film transistor having a hysteresis characteristic.

Another object of embodiments of the invention is to provide an organic light-emitting diode display device and a driving method thereof that reduce a residual image phenomenon.

Another object of embodiments of the invention is to provide an organic light-emitting diode display device and a driving method thereof that reduce a motion image blurring phenomenon.

Another object of embodiments of the invention is to provide an organic light-emitting diode display device and a driving method thereof that compensate a voltage drop of a driving voltage and a ground voltage supply line.

Additional features and advantages of embodiments of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of embodiments of the invention. The objectives and other advantages of the embodiments of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of embodiments of the invention, as embodied and broadly described, an organic light-emitting diode display device includes a driving voltage source providing a driving voltage, a ground voltage source providing a ground voltage, a first scan line receiving a first scanning signal, a second scan line receiving a second scanning signal, a data line crossing the first and second scan lines, a first switch element turned-on in response to the first scanning signal during a first period to supply a data from the data line to a first node, and then maintaining an off-state during a second period, a driving device adjusting a current through an organic light-emitting diode element in accordance with a voltage of the first node, a reference voltage source providing a reference voltage that is capable of turning-off the driving device, a second switch element maintaining an off-state during the first period, and turned-on during the second period to supply the reference voltage to the first node, and a storage capacitor maintaining a voltage at the first node.

In another aspect, an organic light-emitting diode display device includes a driving voltage source providing a driving voltage, a ground voltage source providing a ground voltage, an organic light-emitting diode element, a scan line receiving a first scanning signal and a second scanning signal sequentially at an interval, a data line crossing the scan line and receiving a data voltage and a reset voltage, a switch element turned-on by the first scanning signal during a first period to supply the data voltage to a first node, and then turned-on by the second scanning signal during a second period to supply the reset voltage to the first node, a driving device allowing a current to flow into the organic light-emitting diode element in accordance with the data voltage supplied to the first node and turned-off by the reset voltage supplied to the first node, and a storage capacitor maintaining the voltage at the first node.

In another aspect, an organic light-emitting diode display device includes a driving voltage source providing a driving voltage, a ground voltage source providing a ground voltage, a reference voltage source providing a reference voltage, an organic light-emitting diode element, a capacitor connected between a first node and a second node, a first scan line receiving a first scanning signal and a second scanning signal, a second scan line receiving a first scanning signal and a second scanning signal sequentially at an interval, a data line crossing the scan lines and receiving a data voltage and a reset voltage, a first a switch element turned-on by a signal of the first scan line during a first period to supply the reference voltage to the second node, and then turned-off during a second period, and turned-on by a signal of the first scan line during a third period to supply the reference voltage to the second node, a first b switch element turned-on by a signal of the first scan line during the first period to supply the data voltage to the first node, and then turned-off by a signal of the first scan line during the second period, and turned-on by a signal of the first scan line during the third period to supply the reset voltage to the first node, a driving device allowing a current to flow into the organic light-emitting diode element in accordance with the data voltage supplied to the first node, and turned-off by the reset voltage supplied to the first node, and a second switch element turned-off by a signal of the second scan line for the first period, and then turned-on for the second time to supply one of the driving voltage and the reference voltage to the second node, and turned-off for the third period.

In another aspect, a method of driving an organic light-emitting diode display device, including an organic light-emitting diode element, a driving voltage source providing a driving voltage, a ground voltage source providing a ground voltage, a driving device adjusting a current of the organic light-emitting diode element in accordance with a voltage of a first node, and to which the driving voltage is supplied via a second node, a storage capacitor connected between the first node and the second node, a data line receiving a data voltage, and a scan line crossing the data line and receiving a scanning signal, the method includes supplying a first scanning signal to a first scan line during a first period to turn-on a first switch element connected between the data line and the first node to supply the data voltage to the first node, and turning-off the first switch element, and supplying a second scanning signal to a second scan line during a second period to turn-on a second switch element connected between a reference voltage source generating a reference voltage that is capable of turning-off the driving device and the first node to supply the reference voltage to the first node.

In another aspect, a method of driving an organic light-emitting diode display device, including an organic light-emitting diode element, a driving voltage source providing a driving voltage, a ground voltage source providing a ground voltage, a driving device adjusting a current of the organic light-emitting diode element in accordance with a voltage of a first node, and to which the driving voltage is supplied via a second node, a storage capacitor connected between the first node and the second node, a data line receiving a data voltage, and a scan line crossing the data line and receiving a scanning signal, the method includes supplying the data voltage to the data line during a first period, and then supplying a reset voltage that is capable of turning-off the driving device to the data line during a second period, supplying a first scanning signal to the scan line during the first period to turn-on a first switch element connected between the data line and the first node to supply the data voltage to a first node, and supplying a second scanning signal to the scan line during the second period to supply the reset voltage to the first node.

In another aspect, a method of driving an organic light-emitting diode display device, including an organic light-emitting diode element, a driving voltage source providing a driving voltage, a ground voltage source providing a ground voltage, a driving device adjusting a current of the organic light-emitting diode element in accordance with a voltage of a first node, and to which the driving voltage is supplied via a second node, and a storage capacitor connected between the first node and the second node, the method includes sequentially supplying a data voltage, and a reset voltage that is capable of turning-off the driving device to the data line, supplying a scanning voltage of a first scanning signal to a first scan line during a first period to turn-on a first a switch element connected between a reference voltage source generating a reference voltage and the second node to charge the reference voltage into the second node and, at the same time turning-on a first b switch element connected between the data line and the first node to charge the data voltage into the first node, and supplying a non-scanned voltage of a first inversed scanning signal generated in a reverse phase against the first scanning signal to a second scan line to turn-off a second switch element connected between the driving voltage source and the second node, supplying a non-scanned voltage of the first scanning signal to the first scan line during a second period to turn-off the first a and first b switch elements and, at the same time supplying a scanning voltage of the first inversed scanning signal to the second scan line to turn-on the second switch element to supply supplying one of the driving voltage and the ground voltage to the second node, and supplying a scanning voltage of a second scanning signal to the first scan line during a third period to turn-on the first a and first b switch elements to supply the reset voltage to the first node, and supplying the reference voltage to the second node and, at the same time supplying a non-scanned voltage of a second inversed scanning signal generated in a reverse phase against the second scanning signal to the second scan line to turn-off the second switch element.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of embodiments of the invention as claimed.

The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of embodiments of the invention. In the drawings:

FIG. 1 is a schematic diagram illustrating a structure of an organic light-emitting diode display device according to the related art;

FIG. 2 is a circuit diagram illustrating a pixel of an active matrix type organic light-emitting diode display device according to the related art;

FIG. 3A is a graph illustrating a hysteresis characteristic of a thin film transistor according to the related art;

FIG. 3B is an amplified graph of a portion of the graph shown in FIG. 3A ;

FIG. 4 is a graph illustrating an example which an operating point of a thin film transistor is changed in accordance with a hysteresis characteristic;

FIG. 5A is a diagram illustrating a test data according to the related art;

FIG. 5B is a diagram illustrating an example of a residual image phenomenon after the test data shown in FIG. 5A is applied to the device shown in FIG. 2 ;

FIG. 6 is a graph illustrating a characteristic of a hold type display according to the related art;

FIG. 7 is a graph illustrating a characteristic of impulse type display according to the related art;

FIG. 8 is a block diagram illustrating an organic light-emitting diode display device according to an embodiment of the invention;

FIG. 9 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to an embodiment of the invention;

FIG. 10 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 9 ;

FIG. 11 is a graph illustrating an operation of the driving thin film transistor shown in FIG. 9 ;

FIG. 12 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to another embodiment of the invention;

FIG. 13 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to another embodiment of the invention;

FIG. 14 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 13 ;

FIGS. 15 to 19 are schematic diagrams illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to embodiments of the invention, respectively;

FIG. 20 is a block diagram illustrating an organic light-emitting diode display device according to another embodiment of the invention;

FIG. 21 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to an embodiment of the invention;

FIG. 22 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 21 ;

FIGS. 23 to 26 are schematic diagrams illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to embodiments of the invention, respectively;

FIG. 27 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 26 ;

FIGS. 28 to 30 are schematic diagrams illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to embodiments of the invention, respectively;

FIG. 31 is a block diagram illustrating an organic light-emitting diode display device according to another embodiment of the invention;

FIG. 32 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 31 according to an embodiment of the invention;

FIG. 33 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 32 ;

FIG. 34 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 31 according to another embodiment of the invention; and

FIG. 35 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 34 .

Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings.

FIG. 8 is a block diagram illustrating an organic light-emitting diode display device according to an embodiment of the invention. In FIG. 8 , an organic light-emitting diode display device includes a display panel 80 , a data driving device 82 , a scan driving device 83 , and a timing controller 81 . The display panel 80 has m data lines DL 1 to DLm, n first scan lines S 1 to Sn, n second scan lines E 1 to En, and m×n pixels 84 . The data driving device 82 supplies a data voltage to the data lines DL 1 to DLm. The scan driving device 83 sequentially supplies a first scanning pulse to the first scan lines S 1 to Sn, and sequentially supplies a second scanning pulse to the second scan lines E 1 to En. The timing controller 81 controls the data driving device 82 and the scan driving device 83 .

In addition, the pixels 84 are formed at pixel areas, defined by an intersection of the first and second scan lines (S 1 to Sn and E 1 to En), and the data lines D 1 to Dm. Signal lines are formed at the display panel 80 , and the signal lines are connected to a reference voltage source Vref, a high-level driving voltage source VDD, and a ground voltage GND and to each of the pixels 84 .

The data driving device 82 converts digital video data RGB from the timing controller 81 into an analog gamma compensation voltage. The data driving device 82 also supplies a data voltage to the data lines DL 1 to DLm in response to a data control signal DDC from the timing controller 81 . The data voltage may be an analog gamma compensation voltage, and the data voltage is synchronized with the first scanning pulse to be supplied to the data lines DL 1 to DLm.

The scan driving device 83 sequentially supplies the first scanning pulse in response to a scan control signal SDC from the timing controller 81 to the first scan lines S 1 to Sn, and sequentially supplies a second scanning pulse delayed from the first scanning pulse to the second scan lines E 1 to En. The first scanning pulse indicates a time that needs to charge a data into the pixels of a selected line. The second scanning pulse restores a characteristic of a driving TFT and indicates an inserting time of a black data. The pixels of the selected line include the driving TFT.

The timing controller 81 generates the control signals DDC and SDC. The timing controller 81 also supplies digital video data RGB to the data driving device 82 and controls an operating time of the scan driving device 83 and the data driving device 82 in accordance with a vertical/horizontal synchronizing signal and a clock signal. Each of the pixels 84 includes the organic light-emitting diode element OLED, three TFTs, and one storage capacitor. Each of the pixels 84 may have a configuration as shown in one of FIG. 9 , FIG. 12 , FIG. 13 , and FIG. 15 to FIG. 19 .

FIG. 9 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to an embodiment of the invention, FIG. 10 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 9 , and FIG. 11 is a graph illustrating an operation of the driving thin film transistor shown in FIG. 9 . Referring to FIG. 9 and FIG. 10 , a pixel includes an organic light-emitting diode element OLED, a storage capacitor Cst, a first TFT PM 1 , a second TFT PM 2 , and a third TFT PM 3 . The storage capacitor Cst is provided between a first node n 1 and a second node n 2 .

The first TFT PM 1 forms a current path between a corresponding one of the data lines D 1 to Dm and the first node n 1 in response to a first scanning signal PSCN. The second TFT PM 2 adjusts a current of the organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 . The third TFT PM 3 forms a current path between a reference voltage supply line Lref and the first node n 1 in response to a second scanning pulse PEM. The first to the third TFTs PM 1 to PM 3 are P-type MOS-FETs and may have an amorphous silicon semiconductor layer or a poly silicon semiconductor layer.

In the organic light-emitting diode element OLED, an anode electrode is connected to a drain electrode of the second TFT PM 2 , a cathode electrode is connected to a ground voltage source GND. A current flowing into the organic light-emitting diode element OLED is constantly maintained by a voltage between a gate electrode and a source electrode of the second TFT PM 2 . In addition, the storage capacitor Cst is connected between the first and second nodes n 1 and n 2 . The storage capacitor Cst charges a voltage between the gate electrode and the source electrode of the second TFT PM 2 for a light emitting period EP of a frame period to maintain a light-emitting amount of the organic light-emitting diode element OLED.

The first TFT PM 1 is turned-on in response to the first scanning pulse PSCN from a corresponding one of the first scan lines S 1 to Sn at an initial scanning time of the light emitting period EP. Thus, the first TFT PM 1 forms a current path between the corresponding one of the data lines D 1 to Dm and the first node n 1 to supply a data voltage to the first node n 1 . A gate electrode of the first TFT PM 1 is connected to the corresponding one of first scan lines S 1 to Sn, and a source electrode of the first TFT PM 1 is connected to the corresponding one of the data lines D 1 to Dm. Further, a drain electrode of the first TFT PM 1 is connected to the first node n 1 .

The second TFT PM 2 is a driving TFT, and allows a current to flow into the organic light-emitting diode element OLED in accordance with a data voltage. Herein, the data voltage is supplied to the first node n 1 during the light emitting period EP. For example, the second TFT PM 2 is turned-off by a reference voltage Vref to cut off a current path between a high-level driving voltage source VDD and the organic light-emitting diode element OLED. The reference voltage Vref is supplied to the first node n 1 during a black data inserting period BP of the frame period. The gate electrode of the second TFT PM 2 is connected to the first node n 1 , and the source electrode of the second TFT PM 2 is connected to the high-level driving voltage source VDD. In addition, a drain electrode of the second TFT PM 2 is connected to the anode electrode of an organic light-emitting diode element OLED.

The third TFT PM 3 supplies a reference voltage Vref to the first node n 1 in response to a second scanning pulse PEM from a corresponding one of the second scan lines E 1 to En during the black data inserting period BP. A gate electrode of the third TFT PM 3 is connected to the corresponding one of the second scan lines E 1 to En, and a source electrode of the third TFT PM 3 is connected to a reference voltage supply line Lref. In addition, a drain electrode of the third TFT PM 3 is connected to the first node n 1 .

A pixel having the above-described configuration reduces a residual image phenomenon and a motion blurring phenomenon. In general, the residual image phenomenon is generated by the driving TFT having a hysteresis, and the motion blurring phenomenon is generated at a motion picture. However, in a pixel having the above-described configuration, for an initial scanning time of the light emitting period EP, the first scanning pulse PSCN is generated by a low-level scanning voltage to drop a potential of the corresponding one of the first scan lines S 1 to Sn to a low-level scanning voltage, and a data voltage is supplied to the corresponding one of the data lines D 1 to Dm by the data driving device 82 (shown in FIG. 8 ). Accordingly, the first TFT PM 1 is turned-on by the low-level scanning voltage during the light emitting period EP to supply an analog data voltage corresponding to a video data to the first node n 1 .

Simultaneously, the storage capacitor Cst stores a difference voltage between a high-level driving voltage source VDD and the first node n 1 , that is, a voltage between the gate electrode and the source electrode of the second TFT PM 2 . The second TFT PM 2 is turned-on by a data voltage to form a current path between the source electrode and the drain electrode. Thus, it becomes possible to flow a current into the organic light-emitting diode element OLED. Herein, the data voltage is applied via the first node n 1 .

During the black data inserting period BP, the first scanning pulse PSCN is maintained as a high-level non-scanned voltage, and the second scanning pulse PEM is generated by a low-level scanning voltage to drop a potential of the corresponding one of the second scan lines E 1 to En to a low-level scanning voltage. During the black data inserting period BP, the first TFT PM 1 is maintained an off-state, and the third TFT PM 3 is turned-on by a low-level scanning voltage of the corresponding one of the second scan lines E 1 to En to supply a reference voltage Vref to the first node n 1 . The reference voltage Vref corresponds to a black data, that is, a voltage that is capable of turning-off the second TFT PM 2 in order not to flow a current into the organic light-emitting diode element OLED. For example, a reference voltage Vref may be a reset voltage and may be generated by a highest-level analog gamma voltage corresponding to a black data. In this case, the reset voltage initializes a gate voltage of the second TFT PM 2 .

Thus, according to an embodiment of the invention, a reference voltage Vref is applied to a gate electrode of a driving TFT of a pixel during a black data inserting period BP of each frame period as a reset voltage to initialize an operating point of the driving TFT to “C” point as shown in FIG. 11 . A data voltage is then applied at the next frame. Accordingly, an operating point of the driving TFT of a pixel moves from “C” point forward “D” point without an effect of a prior data voltage. As a result, a hysteresis characteristic is not generated. Also, according to an embodiment of the invention, a current of an organic light-emitting diode element OLED is cut off during the black data inserting period BP of a frame period to operate an organic light-emitting diode element OLED as an impulse type display. Thus, it becomes possible to prevent a motion blurring phenomenon.

FIG. 12 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to another embodiment of the invention. As shown in FIG. 12 , a pixel according to an embodiment of the invention alternatively may have a configuration having a storage capacitor Cst connected between a first node n 1 and an anode electrode of an organic light-emitting diode element OLED, and the pixel may be driven by the driving waveform shown in FIG. 10 .

FIG. 13 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to another embodiment of the invention, and FIG. 14 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 13 . Referring to FIGS. 13 and 14 , a pixel include an organic light-emitting diode element OLED, a storage capacitor Cst, a first TFT NM 1 , a second TFT NM 2 , and a third TFT NM 3 . The storage capacitor Cst is between a first node n 1 and a second node n 2 . The first TFT NM 1 forms a current path between a corresponding one of data lines D 1 to Dm and the first node n 1 in response to a first scanning signal NSCN. The second TFT NM 2 adjusts a current of the organic light-emitting diode element OLED in accordance with a voltage at the first node nil. The third TFT NM 3 forms a current path between a reference voltage supply line Lref and the first node n 1 in response to a second scanning pulse NEM. The first to the third TFTs NM 1 to NM 3 are N-type MOS-FETs and may have an amorphous silicon semiconductor layer or a poly silicon semiconductor layer.

In the organic light-emitting diode element OLED, an anode electrode is connected to a source electrode of the second TFT NM 2 , and a cathode electrode is connected to a ground voltage source GND. A current flowing into the organic light-emitting diode element OLED is constantly maintained by a voltage between a gate electrode and a source electrode of the second TFT NM 2 . In addition, the storage capacitor Cst is connected between the first and second nodes n 1 and n 2 . The storage capacitor Cst charges a voltage between a gate electrode and a source electrode of the second TFT NM 2 during a light emitting period EP of a frame period to maintain a light-emitting amount of the organic light-emitting diode element OLED.

The first TFT NM 1 is turned-on in response to the first scanning pulse NSCN from the corresponding one of the first scan lines S 1 to Sn at an initial scanning time of the light emitting period EP. Thus, the first TFT NM 1 forms a current path between the corresponding one of the data lines D 1 to Dm and the first node n 1 to supply a data voltage to the first node n 1 . A gate electrode of the first TFT NM 1 is connected to the corresponding one of the first scan lines S 1 to Sn, and a drain electrode of the first TFT NM 1 is connected to the corresponding one of the data lines D 1 to Dm. In addition, a source electrode of the first TFT NM 1 is connected to the first node n 1 .

The second TFT NM 2 is a driving TFT, and allows a current to flow into the organic light-emitting diode element OLED in accordance with a data voltage. Herein, the data voltage is supplied to the first node n 1 during the light emitting period EP. For example, the second TFT NM 2 is turned-off by a reference voltage Vref to cut off a current path between a high-level driving voltage VDD and the organic light-emitting diode element OLED. The reference voltage Vref is supplied to the first node n 1 during a black data inserting period BP of the frame period. A gate electrode of the second TFT NM 2 is connected to the first node n 1 , and a drain electrode of the second TFT NM 2 is connected to the high-level driving voltage source VDD. In addition, a source electrode of the second TFT NM 2 is connected to an anode electrode of the organic light-emitting diode element OLED.

The third TFT NM 3 supplies a reference voltage Vref to the first node n 1 in response to a second scanning pulse NEM from a corresponding one of the second scan lines E 1 to En for a black data inserting period BP. A gate electrode of the third TFT NM 3 is connected to the corresponding one of the second scan lines E 1 to En, and a drain electrode of the third TFT NM 3 is connected to a reference voltage supply line Lref. In addition, a source electrode of the third TFT NM 3 is connected to the first node n 1 .

A gate voltage of a second TFT NM 2 is initialized during the black data inserting period BP. Thus, the pixel 84 can prevent a hysteresis phenomenon of a driving TFT. In addition, the pixel 84 can improve a motion blurring phenomenon generated at a motion picture because of a black data inserting effect.

During an initial scanning time of the light emitting period EP, the first scanning pulse NSCN is generated by a high-level scanning voltage to boost a potential of a selected one of first scan lines S 1 to Sn to a high-level scanning voltage, and a data voltage is supplied to the corresponding one of data lines D 1 to Dm by the data driving device 82 (shown in FIG. 8 ). Accordingly, the first TFT NM 1 is turned-on by a high-level scanning voltage during the light emitting period EP of the frame period to supply an analog data voltage corresponding to a video data to the first node n 1 . Simultaneously, the storage capacitor Cst stores a difference voltage between the high-level driving voltage source VDD and the first node n 1 , and the second TFT NM 2 is turned-on by a data voltage to form a current path between a drain electrode and a source electrode. Herein, a data voltage is applied via the first node n 1 . Thus, it becomes possible to flow a current into the organic light-emitting diode element OLED.

During the black data inserting period BP, the first scanning pulse NSCN is maintained a low-level non-scanned voltage, and the second scanning pulse NEM is generated by a high-level scanning voltage to boost a potential of the corresponding one of the second scan lines E 1 to En to a high-level scanning voltage. During the black data inserting period BP, the first TFT NM 1 is maintained an off-state, and the third TFT NM 3 is turned-on by a high-level scanning voltage of the corresponding one of the second scan lines E 1 to En to supply a reference voltage Vref to the first node n 1 . Herein, the reference voltage Vref is a voltage corresponding to a black data, that is, a voltage that is capable of turning-off the second TFT NM 2 in order not to flow a current into the organic light-emitting diode element OLED. For example, the reference voltage Vref may be a reset voltage, and is generated by a lowest-level analog gamma voltage corresponding to a black data. Herein, the reset voltage initializes a gate voltage of the second TFT NM 2 .

FIGS. 15 to 19 are schematic diagrams illustrating a pixel of the organic light-emitting diode display device shown in FIG. 8 according to embodiments of the invention, respectively. As shown in FIG. 15 , a pixel according to an embodiment of the invention alternatively may have a configuration having a storage capacitor Cst connected between a first node n 1 and an anode electrode of an organic light-emitting diode element OLED, and the pixel may be driven by the driving waveform shown in FIG. 14 .

Alternatively, as shown in FIG. 16 , a pixel according to an embodiment of the invention includes an organic light-emitting diode element OLED, a storage capacitor Cst, and a second TFT PM 2 . An anode electrode of the organic light-emitting diode element OLED is connected, via a second node n 2 , to a high-level driving voltage source VDD, and a cathode electrode of the organic light-emitting diode element OLED is connected to a source electrode of the second TFT PM 2 . The storage capacitor Cst is connected between a first node n 1 and a ground voltage source GND. In addition, the gate electrode of the second TFT PM 2 is connected to the first node n 1 . The source electrode of the second TFT PM 2 is connected to the cathode electrode of the organic light-emitting diode element OLED, and the drain electrode of the second TFT PM 2 is connected to the ground voltage source GND. The pixel may be driven by the driving waveform shown in FIG. 10 .

As shown in FIG. 17 , a pixel according to an embodiment of the invention alternatively may have a configuration having a storage capacitor Cst connected between a first node n 1 and a cathode electrode of an organic light-emitting diode element OLED. That is, the storage capacitor is connected between a gate electrode and a source electrode of a second TFT PM 2 , and the pixel may be driven by the driving waveform shown in FIG. 10 .

Alternatively, as shown in FIG. 18 , a pixel according to an embodiment of the invention includes an organic light-emitting diode element OLED, a storage capacitor Cst, and a second TFT NM 2 . An anode electrode of the organic light-emitting diode element OLED is connected to a high-level driving voltage source VDD, and a cathode electrode of the organic light-emitting diode element OLED is connected to a drain electrode of the second TFT NM 2 . the storage capacitor Cst is connected between a first node n 1 and a ground voltage source GND. In addition, the gate electrode of the second TFT NM 2 is connected to the first node n 1 . The drain electrode of the second TFT NM 2 is connected to the cathode electrode of the organic light-emitting diode element OLED, and the source electrode of the second TFT NM 2 is connected to the ground voltage source GND. The pixel may be driven by the driving waveform shown in FIG. 14 .

As shown in FIG. 19 , a pixel according to an embodiment of the invention alternatively may have a configuration having a storage capacitor Cst connected between a first node n 1 and an anode electrode of an organic light-emitting diode element OLED. That is, the storage capacitor is connected between a gate electrode and a source electrode of a second TFT NM 2 , and the pixel may be driven by the driving waveform shown in FIG. 14 .

FIG. 20 is a block diagram illustrating an organic light-emitting diode display device according to another embodiment of the invention. In FIG. 20 , an organic light-emitting diode display device includes a display panel 200 , a data driving device 202 , a scan driving device 203 , and a timing controller 201 . The display panel 200 has m data lines DL 1 to DLm, n scan lines S 1 to Sn, and m×n pixels 204 . The data driving device 202 alternatively supplies a data voltage and a reset voltage to the data lines DL 1 to DLm. The scan driving device 203 sequentially supplies a first scanning pulse and a second scanning pulse to the scan lines S 1 to Sn. The timing controller 201 controls the data driving device 202 and the scan driving device 203 .

In addition, the pixels 204 are formed at pixel areas, defined by an intersection of the scan lines S 1 to Sn and the data lines D 1 to Dm. Signal lines also are formed at the display panel 200 , and the signal lines are connected to a high-level driving voltage source VDD and a ground voltage GND and to each of the pixels 204 .

The data driving device 202 converts digital video data RGB from the timing controller 201 into an analog gamma compensation voltage. The data driving device 202 also supplies a data voltage to the data lines DL 1 to DLm in response to a data control signal DDC from the timing controller 201 . The data voltage may be an analog gamma compensation voltage, and the data voltage is applied in synchronization with the first scanning pulse to be supplied to the data lines DL 1 to DLm. The data driving device 202 also supplies a reset voltage to the data lines D 1 to Dm. The reset voltage prevents light from being emitting at an organic light-emitting diode element OLED of the pixel 204 , and identically restores an operating point of a driving TFT of the pixel 204 for each frame period.

The scan driving device 203 sequentially supplies the first scanning pulse in response to a scan control signal SDC from the timing controller 201 to the scan lines S 1 to Sn. The first scanning pulse is applied in synchronization with the data voltage. The scan driving device 203 also sequentially supplies the second scanning pulse delayed from the first scanning pulse to the scan lines S 1 to Sn. The second scanning pulse is applied in synchronization the reset voltage. A pulse width of the second scanning pulse may be shorter than that of the first scanning pulse.

The timing controller 201 generates the control signals DDC and SDC. The timing controller 201 also supplies digital video data RGB to the data driving device 202 and controls an operating time of the scan driving device 203 and the data driving device 202 in accordance with a vertical/horizontal synchronizing signal and a clock signal. Each of the pixels 204 includes the organic light-emitting diode element OLED, two TFTs, and one storage capacitor. Each of the pixels 204 may have a configuration as shown in one of FIG. 21 , FIG. 23 to FIG. 26 and FIG. 28 to FIG. 30 .

FIG. 21 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to an embodiment of the invention, and FIG. 22 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 21 . Referring to FIG. 21 and FIG. 22 , a pixel includes an organic light-emitting diode element OLED, a storage capacitor Cst, a first TFT PM 1 , and a second TFT PM 2 . The storage capacitor Cst is provided between a first node n 1 and a second node n 2 .

The first TFT PM 1 forms a current path between a corresponding one of the data lines D 1 to Dm and the first node n 1 in response to a first scanning signal PSCN 1 and a second scanning signal PSCN 2 . The second TFT PM 2 adjusts a current of the organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 . The first and second TFTs PM 1 and PM 2 are P-type MOS-FETs and may have an amorphous silicon semiconductor layer or a poly silicon semiconductor layer.

In the organic light-emitting diode element OLED, an anode electrode is connected to a drain electrode of the second TFT PM 2 , a cathode electrode is connected to a ground voltage source GND. A current flowing into the organic light-emitting diode element OLED is constantly maintained by a voltage between a gate electrode and a source electrode of the second TFT PM 2 . In addition, the storage capacitor Cst is connected between the first and second nodes n 1 and n 2 . The storage capacitor Cst charges a voltage between the gate electrode and the source electrode of the second TFT PM 2 for a light emitting period EP of a frame period to maintain a light-emitting amount of the organic light-emitting diode element OLED.

The first TFT PM 1 is turned-on in response to the first scanning pulse PSCN 1 from a corresponding one of the scan lines S 1 to Sn at an initial scanning time of the light emitting period EP. Thus, the first TFT PM 1 forms a current path between the corresponding one of the data lines D 1 to Dm and the first node n 1 to supply a data voltage Vdata to the first node n 1 . The first TFT PM 1 also is turned-on in response to the second scanning pulse PSCN 2 from the corresponding one of the scan lines S 1 to Sn at an initial scanning period of a black data inserting period BP of the frame period. Thus, the first TFT PM 1 forms a current path between the corresponding one of the data lines D 1 to Dm and the first node n 1 to supply a reset voltage Vrst to the first node n 1 . A gate electrode of the first TFT PM 1 is connected to the corresponding one of first scan lines S 1 to Sn, and a source electrode of the first TFT PM 1 is connected to the corresponding one of the data lines D 1 to Dm. Further, a drain electrode of the first TFT PM 1 is connected to the first node n 1 .

The second TFT PM 2 is a driving TFT, and allows a current to flow into the organic light-emitting diode element OLED in accordance with a data voltage. Herein, the data voltage is supplied to the first node n 1 during the light emitting period EP. For example, the second TFT PM 2 is turned-off by a reset voltage Vrst to cut off a current path between a high-level driving voltage source VDD and the organic light-emitting diode element OLED. The reset voltage Vrst is supplied to the first node n 1 during the black data inserting period BP. The gate electrode of the second TFT PM 2 is connected to the first node n 1 , and the source electrode of the second TFT PM 2 is connected to the high-level driving voltage source VDD. In addition, a drain electrode of the second TFT PM 2 is connected to the anode electrode of an organic light-emitting diode element OLED.

The pixel 204 can improve a residual image phenomenon and a motion blurring phenomenon. In a pixel having the above-described configuration, for an initial scanning time of the light emitting period EP, the first scanning pulse PSCN 1 is generated by a low-level scanning voltage to drop a potential of the corresponding one of the first scan lines S 1 to Sn to a low-level scanning voltage, and the analog data voltage Vdata is supplied to the corresponding one of the data lines D 1 to Dm by the data driving device 202 (shown in FIG. 8 ). Accordingly, the first TFT PM 1 is turned-on by the low-level scanning voltage during the light emitting period EP to supply the analog data voltage Vdata corresponding to a video data to the first node n 1 .

Simultaneously, the storage capacitor Cst stores a difference voltage between a high-level driving voltage source VDD and the first node n 1 , that is, a voltage between the gate electrode and the source electrode of the second TFT PM 2 . The second TFT PM 2 is turned-on by a data voltage to form a current path between the source electrode and the drain electrode. Thus, it becomes possible to flow a current into the organic light-emitting diode element OLED. Herein, the data voltage is applied via the first node n 1 .

During an initial scanning period of the black data inserting period BP, the second scanning pulse PSCN 2 of a low-level scanning voltage is supplied to the corresponding one of the scan lines S 1 to Sn and, at the same time a high-level reset voltage Vrst corresponding to a black data is supplied to the corresponding one of the data lines D 1 to Dm. Thus, the first TFT PM 1 is turned-on by the second scanning pulse PSCN 2 to supply the high-level reset voltage Vrst to the first node n 1 . In addition, the second TFT PM 2 is turned-off and initialized by the high-level reset voltage Vrst. The high-level reset voltage Vrst is applied to the gate electrode of the second TFT PM 2 . Thus, a current and a light-emitting amount of an organic light-emitting diode element OLED become ‘0’.

Thus, according to an embodiment of the invention, a reset voltage Vrst is applied to a gate electrode of a driving TFT of a pixel during a black data inserting period BP of each frame period to initialize an operating point of the driving TFT to “C” point as shown in FIG. 11 . A data voltage is then applied at the next frame. Accordingly, an operating point of the driving TFT moves from “C” point forward “D” point without an effect of a prior data voltage. As a result, a hysteresis characteristic is not generated. Also, according to an embodiment of the invention, a current of an organic light-emitting diode element OLED is cut off during the black data inserting period BP to operate an organic light-emitting diode element OLED as an impulse type display. Thus, it becomes possible to prevent a motion blurring phenomenon.

FIGS. 23 to 26 are schematic diagrams illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to embodiments of the invention, respectively. As shown in FIG. 23 , a pixel according to an embodiment of the invention alternatively may have a configuration having a storage capacitor Cst connected between a first node n 1 and an anode electrode of an organic light-emitting diode element OLED, and the pixel may be driven by the driving waveform shown in FIG. 22 .

Alternatively, as shown in FIG. 24 , a pixel according to an embodiment of the invention includes an organic light-emitting diode element OLED, a storage capacitor Cst, and a second TFT PM 2 . An anode electrode of the organic light-emitting diode element OLED is connected, via a second node n 2 , to a high-level driving voltage source VDD, and a cathode electrode of the organic light-emitting diode element OLED is connected to a source electrode of the second TFT PM 2 . The storage capacitor Cst is connected between a first node n 1 and a ground voltage source GND. In addition, the gate electrode of the second TFT PM 2 is connected to the first node n 1 . The source electrode of the second TFT PM 2 is connected to the cathode electrode of the organic light-emitting diode element OLED, and the drain electrode of the second TFT PM 2 is connected to the ground voltage source GND. The pixel may be driven by the driving waveform shown in FIG. 22 .

As shown in FIG. 25 , a pixel according to an embodiment of the invention alternatively may have a configuration having a storage capacitor Cst connected between a first node n 1 and a cathode electrode of an organic light-emitting diode element OLED. That is, the storage capacitor is connected between a gate electrode and a source electrode of a second TFT PM 2 , and the pixel may be driven by the driving waveform shown in FIG. 22 .

FIG. 26 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to another embodiment of the invention, and FIG. 27 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 26 . Referring to FIGS. 26 and 27 , a pixel include an organic light-emitting diode element OLED, a storage capacitor Cst, a first TFT NM 1 , and a second TFT NM 2 . The storage capacitor Cst is between a first node n 1 and a ground voltage source GND. The first TFT NM 1 forms a current path between a corresponding one of data lines D 1 to Dm and the first node n 1 in response to first and second scanning signals NSCN 1 and NSCN 2 . The second TFT NM 2 adjusts a current of the organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 . The first and second TFTs NM 1 and NM 2 are N-type MOS-FETs and may have an amorphous silicon semiconductor layer or a poly silicon semiconductor layer.

In the organic light-emitting diode element OLED, an anode electrode is connected, via a second node n 2 , to a high-level driving voltage source VDD, and a cathode electrode is connected to a drain electrode of the second TFT NM 2 . A current flowing into the organic light-emitting diode element OLED is constantly maintained by a voltage between a gate and a source of the second TFT NM 2 .

The storage capacitor Cst is connected between the first node n 1 and the ground voltage source GND. The storage capacitor Cst charges a voltage between a gate and a source of the second TFT NM 2 for a light emitting period EP to maintain a light-emitting amount of the organic light-emitting diode element OLED. In addition, a gate electrode of the first TFT NM 1 is connected to the corresponding one of the scan lines S 1 to Sn, and a drain electrode of the first TFT NM 1 is connected to the corresponding one of the data lines D 1 to Dm. A source electrode of the first TFT NM 1 is connected to the first node n 1 .

The first TFT NM 1 is turned-on in response to the first scanning pulse NSCN 1 from the corresponding one of the scan lines S 1 to Sn at an initial scanning period of a light emitting period EP of a frame period. Thus, the first TFT NM 1 forms a current path between the corresponding one of the data lines D 1 to Dm and the first node n 1 to supply a data voltage Vdata to the first node n 1 . In addition, the first TFT NM 1 is turned-on in response to the second scanning pulse NSCN 2 from the corresponding one of the scan lines S 1 to Sn at an initial scanning period of a black data inserting period BP of the frame period. Thus, the first TFT NM 1 forms a current path between the corresponding one of data lines D 1 to Dm and the first node n 1 to supply a reset voltage Vrst to the first node n 1 .

The second TFT NM 2 is a driving TFT, and allows a current to flow into an organic light-emitting diode element OLED in accordance with a data voltage. The data voltage is supplied to the first node n 1 during the light emitting period EP. On the other hands, the second TFT NM 2 is turned-off by a reset voltage Vrst to cut off a current of the organic light-emitting diode element OLED. Herein, the reset voltage Vrst is supplied to the first node n 1 during the black data inserting period BP. A gate electrode of the second TFT NM 2 is connected to the first node n 1 , and a drain electrode of the second TFT NM 2 is connected to a cathode electrode of the organic light-emitting diode element OLED. A source electrode of the second TFT NM 2 is connected to the ground voltage source GND.

During an initial scanning time of the light emitting period EP, the first scanning pulse NSCN 1 is generated by a high-level scanning voltage to boost a potential of a selected one of first scan lines S 1 to Sn to a high-level scanning voltage, and a data voltage is supplied to the corresponding one of data lines D 1 to Dm by the data driving device 202 (shown in FIG. 8 ). Accordingly, the first TFT NM 1 is turned-on by a high-level scanning voltage during the light emitting period EP of the frame period to supply an analog data voltage Vdata corresponding to a video data to the first node n 1 . Simultaneously, the storage capacitor Cst stores a voltage of the first node N 1 , that is, the data voltage Vdata, and the second TFT NM 2 is turned-on by a data voltage at the first node n 1 . Thus, it becomes possible to flow a current into the organic light-emitting diode element OLED.

During the black data inserting period BP, the second scanning pulse NSCN 2 of a high-level scanning voltage is supplied to the selected one of the scan lines S 1 to Sn, and, at the same time a lowest-level analog gamma voltage corresponding to a black data or a low-level reset voltage Vrst less than thereof is supplied to the corresponding one of the data lines D 1 to Dm. Thus, the first TFT NM 1 is turned-on by the second scanning pulse NSCN 2 to supply the low-level reset voltage Vrst to the first node n 1 . As a result, the second TFT NM 2 is turned-off and initialized by the low-level reset voltage Vrst. Herein, the low-level reset voltage Vrst is applied to the gate electrode of the second TFT NM 2 . Thus, a current and a light-emitting amount of an organic light-emitting diode element OLED become ‘0’.

FIGS. 28 to 30 are schematic diagrams illustrating a pixel of the organic light-emitting diode display device shown in FIG. 20 according to embodiments of the invention, respectively. As shown in FIG. 28 , a pixel according to an embodiment of the invention alternatively may have a configuration having an anode electrode of the organic light-emitting diode element OLED connected to a source electrode of the second TFT NM 2 , and a cathode electrode thereof connected to a ground voltage source GND. The storage capacitor Cst is connected between a first node n 1 and a second node n 2 . A gate electrode of the second TFT NM 2 is connected to the first node n 1 , and a drain electrode of the second TFT NM 2 is connected to the second node n 2 . The pixel may be driven by the driving waveform shown in FIG. 27 .

Alternatively, as shown in FIG. 29 , a pixel according to an embodiment of the invention may have a configuration having a storage capacitor Cst connected between a first node n 1 and an anode electrode of the organic light-emitting diode element OLED. The pixel also may be driven by the driving waveform shown in FIG. 27 .

As shown in FIG. 30 , a pixel according to an embodiment of the invention alternatively may have a storage capacitor Cst connected between a first node n 1 and an cathode electrode of an organic light-emitting diode element OLED. Such a pixel also may be driven by the driving waveform shown in FIG. 27 .

Accordingly, according to an embodiment of the invention, a current flowing into an organic light-emitting diode element OLED is only defined by a voltage between a gate electrode and a source electrode of a driving TFT. For example, in a pixel driving circuit shown in one of FIG. 9 , FIG. 12 , FIG. 18 , FIG. 19 , FIG. 21 , FIG. 23 , FIG. 26 , and FIG. 30 , a current flowing into the organic light-emitting diode element OLED is only defined by a voltage between a gate electrode and a source electrode of a driving TFT. Thus, such a pixel driving circuit is a current source circuit that is capable of constantly flowing a current of the organic light-emitting diode element OLED irregardless of characteristics of the organic light-emitting diode element OLED (for example, a threshold voltage).

In addition, in a pixel driving circuit shown in one of FIG. 13 , FIG. 15 , FIG. 16 , FIG. 17 , FIG. 24 , FIG. 25 , FIG. 28 , and FIG. 29 , a voltage is generated at a source electrode of a TFT (source follower) and is in proportion to a gate voltage. Such a pixel driving circuit allows a current to flow into the organic light-emitting diode element OLED by a difference voltage between a voltage and a high-level driving voltage source VDD, or by a difference voltage between the voltage and a ground voltage GND.

FIG. 31 is a block diagram illustrating an organic light-emitting diode display device according to another embodiment of the invention. In FIG. 31 , an organic light-emitting diode display device includes a display panel 290 , a data driving device 292 , a scan driving device 293 , and a timing controller 291 . The display panel 290 has m data lines DL 1 to DLm, n non-inverted scan lines S 1 to Sn, n inverted scan lines SB 1 to SBn, and m×n pixels 294 . The data driving device 292 alternatively supplies a data voltage and a reset voltage to the data lines DL 1 to DLm. The scan driving device 293 sequentially supplies first and second non-inverted scanning pulses to the non-inverted scan lines S 1 to Sn, and sequentially supplies first and second inverted scanning pulses to the inverted scan lines SB 1 to SBn. The timing controller 291 controls the data driving device 292 and the scan driving device 293 .

In addition, the pixels 294 are formed at pixel areas, defined by an intersection of the scan lines (S 1 to Sn and SB 1 to SBn) and the data lines D 1 to Dm. Signal lines also are formed at the display panel 290 , and the signal lines are connected to a reference voltage source Vref, a high-level driving voltage source VDD and a ground voltage GND and to each of the pixels 294 .

The data driving device 292 converts digital video data RGB from the timing controller 291 into an analog gamma compensation voltage. The data driving device 292 also supplies a data voltage to the data lines DL 1 to DLm in response to a data control signal DDC from the timing controller 291 during a scanning period of a programming period. The data voltage may be an analog gamma compensation voltage, and the data voltage is in synchronization with the first non-inverting scanning pulse and the first inverted scanning pulse. The data driving device 292 also supplies a reset voltage to the data lines D 1 to Dm during a scanning period of a reset period. The reset voltage is applied in synchronization with the second non-inverted pulse and the second inverted scanning pulse.

During a scanning period of a programming period, the scan driving device 293 sequentially supplies the first non-inverted scanning pulse in response to a scan control signal SDC from the timing controller 291 to the non-inverted scan lines S 1 to Sn. The scan driving device 293 also at the same time, sequentially supplies the first inverted scanning pulse to the inverted scan lines SB 1 and SBn. In particular, the first non-inverted scanning pulse and the first inverted scanning pulse are applied in synchronization with the data voltage. The first inverted scanning pulse may be inversed in a reverse phase or by 180 degrees against the first non-inverted scanning pulse.

Moreover, during a scanning period of a reset period, the scan driving device 293 sequentially supplies the second non-inverted scanning pulse to the non-inverted scan lines S 1 to Sn and, at the same time, supplies the second inverted scanning pulse to the inverted scan lines SB 1 to SBn. The second non-inverted scanning pulse and the second inverted scanning pulse are applied in synchronization with the reset voltage. The second inverted scanning pulse may be inversed in a reverse phase or by 180 degrees against the second non-inverted scanning pulse.

The timing controller 291 generates the control signals DDC and SDC. The timing controller 291 also supplies digital video data RGB to the data driving device 292 and controls an operating time of the scan driving device 293 and the data driving device 292 in accordance with a vertical/horizontal synchronizing signal and a clock signal. Each of the pixels 294 includes the organic light-emitting diode element OLED, four TFTs, and one storage capacitor. Each of the pixels 294 may have a configuration as shown in one of FIG. 32 and FIG. 34 .

FIG. 32 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 31 according to an embodiment of the invention, and FIG. 33 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 32 . Referring to FIG. 32 and FIG. 33 , a pixel includes an organic light-emitting diode element OLED, a storage capacitor Cst, a first a TFT PM 1 a , a first b TFT PM 1 b , a second TFT PM 2 , and a third TFT PM 3 . The storage capacitor is provided between a first node n 1 and a second node n 2 . The first a TFT PM 1 a is turned-on by the non-inverted first and second scanning pulses PSCN 1 and PSCN 2 to form a current path between a reference voltage supply line and the second node n 2 . The first b TFT PM 1 b forms a current path between data lines D 1 to Dm and the first node n 1 in response to the non-inverted scanning pulses PSCN 1 and PSCN 2 . The second TFT PM 2 adjusts a current of an organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 . The third TFT PM 3 is turned-off by the inverted scanning pulses PSCB 1 and PSCB 2 to cut off a current path between a high-level driving voltage supply line and the second node n 2 . The first to the third TFTs PM 1 a to PM 3 are P-type MOS-FETs, and have an amorphous silicon semiconductor layer or a poly silicon semiconductor layer.

In the organic light-emitting diode element OLED, an anode electrode is connected to a drain electrode of second TFT PM 2 , and a cathode electrode is connected to a ground voltage source GND. In addition, the storage capacitor Cst is connected between the first node n 1 and the second node n 2 . The first a TFT PM 1 a is turned-on by the first non-inverted scanning pulse PSCN 1 during a programming period PP of a frame period to supply a reference voltage Vref to the second node n 2 , and then the first a TFT PM 1 a is turned-off during a light emitting period EP of the frame period. Further, the first a TFT PM 1 a is again turned-on by the second non-inverted scanning pulse PSCN 2 during a black data inserting period BP to supply a reset voltage Vrst to the second node n 2 . A gate electrode of the first a TFT PM 1 a is connected to a corresponding one of the non-inverted scan lines S 1 to Sn, and a source electrode of the first a TFT PM 1 a is connected to a reference voltage supply line. A drain electrode of the first a TFT PM 1 a is connected to the second node n 2 .

The first b TFT PM 1 b is simultaneously turned-on/turned-off with the first a TFT PM 1 a by the first and second non-inverted scanning pulses PSCN 1 and PSCN 2 to alternately supply the data voltage Vdata and the reset voltage Vrst from the corresponding one of the data lines D 1 to Dm to the first node n 1 . The gate electrode of the first b TFT PM 1 b is connected to the corresponding one of the non-inverted scan lines S 1 to Sn, and a source electrode of the first b TFT PM 1 b is connected to the corresponding one of the data lines D 1 to Dm. A drain electrode of the first b TFT PM 1 b is connected to the first node n 1 .

The second TFT PM 2 allows a current to flow into an organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 during the light emitting period EP. The second TFT PM 2 is turned-off by the reset voltage Vrst during the black data inserting period BP to cut off a current path of the organic light-emitting diode element OLED. The reset voltage Vrst is applied to the first node n 1 . A gate electrode of the second TFT PM 2 is connected to the first node n 1 , and a source electrode of the second TFT PM 2 is connected to a high-level driving voltage source VDD. A drain electrode of the second TFT PM 2 is connected to the anode electrode of the organic light-emitting diode element OLED.

The third TFT PM 3 is turned-off by the first inverted scanning pulse PSCB 1 during the programming period PP to cut off a current path between the high-level driving voltage source VDD and the second node n 2 . The third TFT PM 3 is turned-on by a low-level scanning voltage from the corresponding one of the inverted scan lines SB 1 and SBn during a light emitting period EP to supply the high-level driving voltage source VDD to the second node n 2 . Next, the third TFT PM 3 is turned-off by the second inverted scanning pulse PSCB 2 during the black data inserting period BP. The third TFT PM 3 is turned-on when a voltage of the second inverted scanning pulse PSCB 2 is changed into the low-level scanning voltage to convert a voltage of the inverted scan lines SB 1 and SBn into the low-level scanning voltage. As a result, the third TFT PM 3 supplies the high-level driving voltage source VDD to the second node n 2 .

The pixel 294 can reduce a residual image phenomenon and a motion blurring phenomenon caused by a driving TFT having a hysteresis characteristic. In addition, the pixel 294 minimizes an effect of a high-level driving voltage source VDD at a current of an organic light-emitting diode element OLED to prevent a picture quality deterioration.

During the programming period PP of a frame period, the first non-inverted scanning pulse PSCN 1 of a low-level scanning voltage is supplied to the selected one of the non-inverted scan lines S 1 to Sn, and a first inverted scanning pulse PSCB 1 of a high-level non-scanned voltage is supplied to the selected one of inverted scan lines SB 1 to SBn. The data voltage Vdata is supplied to data lines D 1 to Dm. Thus, the data voltage Vdata is applied in synchronization with the first non-inverted scanning pulse PSCN 1 .

Thus, during the programming period PP, the first a and first b TFTs PM 1 a and PM 1 b are turned-on by the low-level scanning voltage of the non-inverted scan lines S 1 to Sn, and the third TFT PM 3 is turned-off by the high-level non-scanned voltage of the inverted scan lines SB 1 to SBn. Accordingly, the second node n 2 is charged with a reference voltage Vref, and the first node n 1 is charged with the data voltage Vdata. As a result, a voltage of the first node and the second node n 1 and n 2 for the programming period is Vn 1 =Vdata and Vn 2 =Vref, respectively, where ‘Vn 1 ’ representing a voltage of the first node n 1 and ‘Vn 2 ’ representing a voltage of the second node n 2 . In addition, the storage capacitor Cst charges a difference voltage between the data voltage Vdata and the reference voltage Vref.

During the light emitting period EP, a potential of the non-inverted scan lines S 1 to Sn is inversed into a high-level non-scanned voltage, and a potential of the inverted scan lines SB 1 to SBn is inversed into a low-level scanning voltage. Thus, during light emitting period EP, the first a and first b TFTs PM 1 a and PM 1 b are turned-off by the high-level non-scanned voltage of the non-inverted scan lines S 1 to Sn, and the third TFT PM 3 is turned-on by the low-level scanning voltage of the inverted scan lines SB 1 to SBn. Accordingly, a high-level driving voltage source VDD is supplied to the second node n 2 , and a voltage of the storage capacitor Cst is boot-strapped. Accordingly, voltages at the first node and the second node are Vn 1 =VDD+Vdata−Vref and Vn 2 =VDD, respectively, during the light emitting period EP. As a result, a current I OLED of an organic light-emitting diode element OLED is as the following Equation 1. Herein, the flow of the current I OLED is controlled by the second TFT PM 2 .

I OLED = k 2 ⁢ W L ⁢ ( Vref - Vdata -  Vth  ) 2 [ Equation ⁢ ⁢ 1 ]

‘Vth’ represents a threshold voltage of the second TFT PM 2 , ‘k’ represents a constant defined by mobility and a parasitic capacitance of the second TFT PM 2 , ‘L’ represents a channel length of the second TFT PM 2 , and ‘W’ represents a channel width of the second TFT PM 2 .

Referring to the Equation 1, in the organic light-emitting diode display according to an embodiment of the invention, a current I OLED flowing into an organic light-emitting diode element OLED is not dependent on a high-level driving voltage source VDD. Thus, the current I OLED flowing into the organic light-emitting diode element OLED for a light emitting period EP is not affected by the high-level driving voltage source VDD.

During an initial scanning period of a black data inserting period BP, a potential of the non-inverted scan lines S 1 to Sn is again inversed into a low-level scanning voltage by a second non-inverted scanning pulse PSCN 2 , and a potential of the inverted scan lines SB 1 to SBn is again inversed into a high-level non-scanned voltage by the second non-inverted scanning pulse PSCN 2 . In addition, data lines are supplied with a reset voltage Vrst.

Thus, during the initial scanning period of the black data inserting period BP, the first a and first b TFTs PM 1 a and PM 1 b are turned-on by the low-level scanning voltage, and the third TFT PM 3 is turned-off by the high-level non-scanned voltage. The low-level scanning voltage is applied to the gate electrode of the first a and first b TFTs PM 1 a and PM 1 b , and the high-level non-scanned voltage is applied to the gate electrode of the third TFT PM 3 . Accordingly, a voltage at the first node n 1 becomes Vn 1 =Vrst, and a voltage at the second node n 2 becomes Vn 2 =Vref during the initial scanning period of the black data inserting period BP.

Next, during the black data inserting period BP, a voltage at the first node n 1 is changed to Vn 1 =Vrst+VDD−Vref by a potential inversion of the non-inverted scan lines S 1 to Sn and the inverted scan lines SB 1 to SBn, and a voltage at the second node n 2 is changed into Vn 2 =VDD by a potential inversion of the non-inverted scan lines S 1 to Sn and the inverted scan lines SB 1 to SBn. Thus, the second TFT PM 2 is turn-off because of “Vrst+VDD−Vref,” with “Vrst+VDD−Vref” being increased enough not to cause a light emission at the organic light-emitting diode element OLED.

FIG. 34 is a schematic diagram illustrating a pixel of the organic light-emitting diode display device shown in FIG. 31 according to another embodiment of the invention, and FIG. 35 is a waveform diagram illustrating an exemplary driving waveform for the pixel shown in FIG. 34 . Referring to FIG. 34 and FIG. 35 , the pixel 294 includes an organic light-emitting diode element OLED, a storage capacitor Cst, a first a TFT NM 1 a , a first b TFT NM 1 b , a second TFT NM 2 , and a third TFT NM 3 .

The storage capacitor Cst is provided between a first node n 1 and a second node n 2 . The first a TFT NM 1 a is turned-on by non-inverted first and second scanning pulses NSCN 1 and NSCN 2 to form a current path between a reference voltage supply line and the second node n 2 . The first b TFT NM 1 b forms a current path between data lines D 1 to Dm and the first node n 1 in response to the non-inverted first and second scanning pulses NSCN 1 and NSCN 2 . The second TFT NM 2 adjusts a current of the organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 . The third TFT NM 3 is turned-off by first and second inverted scanning pulses NSCB 1 and NSCB 2 to cut off a current path between a ground voltage source GND and the second node n 2 . The first to third TFTs NM 1 a to NM 3 are N-type MOS-FETs and may have an amorphous silicon semiconductor layer or a poly silicon semiconductor layer.

In the organic light-emitting diode element OLED, an anode electrode is connected to a high-level driving voltage source VDD, and a cathode electrode is connected to a drain electrode of the second TFT NM 2 . The first a TFT NM 1 a is turned-on by the first non-inverted scanning pulse NSCN 1 during a programming period PP of a frame period to supply a reference voltage Vref to the second node n 2 , and then the first a TFT NM 1 a is turned-off during a light emitting period EP. The first a TFT NM 1 a is again turned-on by the second non-inverted scanning pulse NSCN 2 during a black data inserting period BP to supply a reset voltage Vrst to the second node n 2 . A gate electrode of the first a TFT NM 1 a is connected to non-inverted scan lines S 1 to Sn, and a drain electrode of the first a TFT NM 1 a is connected to a reference voltage supply line. A source electrode of the first a TFT NM 1 a is connected to the second node n 2 .

The first b TFT NM 1 b is simultaneously turned-on/turned-off with the first a TFT NM 1 a by the first and second non-inverted scanning pulses NSCN 1 and NSCN 2 to alternately supply a data voltage Vdata and the reset voltage Vrst from data lines D 1 to Dm to the first node n 1 . A gate electrode of the first b TFT NM 1 b is connected to the non-inverted scan lines S 1 to Sn, and a drain electrode of the first b TFT NM 1 b is connected to data lines D 1 to Dm. A source electrode of the first b TFT NM 1 b is connected to the first node n 1 .

The second TFT NM 2 allows a current to flow into the organic light-emitting diode element OLED in accordance with a voltage at the first node n 1 during a light emitting period EP. The second TFT NM 2 is turned-off by the reset voltage Vrst to cut off a current path of the organic light-emitting diode element OLED. The reset voltage Vrst is applied to the first node n 1 during the black data inserting period BP. A gate electrode of the second TFT NM 2 is connected to the first node n 1 , and a drain electrode of the second TFT NM 2 is connected to the cathode electrode of the organic light-emitting diode element OLED. A source electrode of the second TFT NM 2 is connected to a ground voltage source GND.

The third TFT NM 3 is turned-off by the first inverted scanning pulse NSCB 1 during the programming period PP to cut off a current path between a ground voltage source GND and the second node n 2 . The third TFT NM 3 is turned-on by a high-level scanning voltage from the inverted scan lines SB 1 and SBn during the light emitting period EP to supply the ground voltage GND to the second node n 2 . Next, the third TFT NM 3 is turned-off by the second inverted scanning pulse NSCB 2 during the black data inserting period BP, and then the third TFT NM 3 is turned-on when a voltage of the second inverted scanning pulse NSCB 2 is changed into a high-level scanning voltage to convert a voltage of the inverted scan lines SB 1 and SBn into the high-level scanning voltage. As a result, the third TFT NM 3 supplies the ground voltage GND to the second node n 2 .

The pixel 294 can reduce a residual image phenomenon and a motion blurring phenomenon. In this case, the residual image phenomenon is generated by a driving TFT having a hysteresis, and the motion blurring phenomenon is generated at a motion picture. Also, the pixel 294 minimizes an effect of a ground voltage GND at a current of an organic light-emitting diode element OLED to prevent a picture quality deterioration. Herein, the picture quality deterioration is generated by a change of the ground voltage GND.

During a programming period PP, the first non-inverted scanning pulse NSCN 1 of a high-level scanning voltage is supplied to the non-inverted scan lines S 1 to Sn, and the first inverted scanning pulse NSCB 1 of a low-level non-scanned voltage is supplied to the inverted scan lines SB 1 to SBn. In addition, the data voltage Vdata is supplied to the data lines D 1 to Dm. Thus, the data voltage is applied in synchronization with the first non-inverted scanning pulse NSCN 1 . Thus, during the programming period PP, the first a and first b TFTs NM 1 a and NM 1 b are turned-on by the high-level scanning voltage of the non-inverted scan lines S 1 to Sn, and the third TFT NM 3 is turned-off by the low-level electric non-scanned voltage of the inverted scan lines SB 1 to SBn. Accordingly, the second node n 2 is charged with a reference voltage Vref, and the first node n 1 is charged with the data voltage Vdata. Herein, the reference voltage Vref is less than a ground voltage GND.

During a light emitting period EP, a potential of the non-inverted scan lines S 1 to Sn is inversed into a low-level non-scanned voltage, and a potential of the inverted scan lines SB 1 to SBn is inversed into a high-level scanning voltage. During the light emitting period EP, the first a and first b TFTs NM 1 a and NM 1 b are turned-off by the low-level non-scanned voltage of the non-inverted scan lines S 1 to Sn, and the third TFT NM 3 is turned-on by the high-level scanning voltage of the inverted scan lines SB 1 to SBn. Accordingly, the ground voltage GND is supplied to the second node n 2 , and a voltage of the storage capacitor Cst is boot-strapped. Voltages at the first and second nodes n 1 and n 2 are Vn 1 =Vdata+GND+Vref and Vn 2 =GND, respectively, during the light emitting period EP. As a result, a current I OLED of an organic light-emitting diode element OLED is as the following Equation 2. Herein, the flow of the current I OLED is controlled by the second TFT PM 2 .

I OLED = k 2 ⁢ W L ⁢ ( Vdata - Vref -  Vth  ) 2 [ Equation ⁢ ⁢ 2 ]

‘Vth’ represents a threshold voltage of the second TFT NM 2 , ‘k’ represents a constant defined by mobility and a parasitic capacitance of the second TFT NM 2 , ‘L’ represents a channel length of the second TFT NM 2 , and ‘W’ represents a channel width of the second TFT NM 2 .

Referring to the Equation 2, in the organic light-emitting diode display according to an embodiment of the invention, a current I OLED flowing into an organic light-emitting diode element OLED is not dependent on a ground voltage GND. Thus, the current I OLED flowing into the organic light-emitting diode element OLED for a light emitting period EP is not affected by the ground voltage GND.

During an initial scanning period of the black data inserting period BP, a potential of the non-inverted scan lines S 1 to Sn is again inversed into a high-level scanning voltage by the second non-inverted scanning pulse NSCN 2 , and a potential of the inverted scan lines SB 1 to SBn is again inversed into a low-level non-scanned voltage by the second non-inverted scanning pulse NSCN 2 . In addition, data lines are supplied with a reset voltage Vrst. During the initial scanning period of the black data inserting period BP, the first a and first b TFTs NM 1 a and NM 1 b are turned-on by the high-level scanning voltage, and the third TFT NM 3 is turned-off by the low-level non-scanned voltage. Thus, the high-level scanning voltage is applied to the gate electrode of the first a and first b TFTs NM 1 a and NM 1 b , and the low-level non-scanned voltage is applied to the third TFT NM 3 . Accordingly, during the initial scanning period of the black data inserting period BP, a voltage at the first node n 1 becomes the reset voltage Vrst, and a voltage at the second node n 2 becomes the reference voltage Vref.

Next, during anther period of the black data inserting period BP, a voltage at the first node n 1 is changed into Vn 1 =Vrst−Vref by a potential inversion of the scan lines S 1 to Sn and the inverted scan lines SB 1 to SBn, and a voltage at the second node n 2 is changed into Vn 2 =GND by a potential inversion of the scan lines S 1 to Sn and the inverted scan lines SB 1 to SBn. Thus, the second TFT NM 2 is turn-off because of “Vrst−Vref,” with “Vrst−Vref” being decreased enough not to cause a light emission at the organic light-emitting diode element OLED.

In each of the above-described pixel configurations, the TFTs of one pixel have the same channel characteristics. Alternatively, although not shown, the TFTs of one pixel may have different channel characteristics from one another and may be formed at one pixel by a complementary metal oxide semiconductor (“CMOS”) process. In addition, a voltage of scanning pulses may be changed in accordance with a channel characteristics of the N-type MOS-FET and the P-type MOS-FET if an N-type MOS-FET and a P-type MOS-FET are simultaneously formed at one pixel.

Hence, an organic light-emitting diode display device and a driving method thereof according to an embodiment of the invention reduce a residual image phenomenon and a motion blurring phenomenon using switch elements more than two. As a result, an organic light-emitting diode display device and a driving method thereof according to an embodiment of the invention improve brightness uniformity at a large size panel.

It will be apparent to those skilled in the art that various modifications and variations can be made in the organic light-emitting diode display device and the driving method thereof employing the same of embodiments of the invention without departing from the spirit or scope of the invention. Thus, it is intended that embodiments of the invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.