KR20050004470A - Apparatus and method for driving electro-luminescence display device - Google Patents

Abstract

PURPOSE: A driver apparatus of an electro-luminescence display device and its method are provided to output desired luminance by controlling the intensity of a current constantly flowing to an EL cell. CONSTITUTION: A number of electro-luminescence cells are formed on an EL panel(50). A number of cell driving units drive the cells. A power supply unit(45) supplies power to the panel. The power supply unit supplies a supply voltage to an anode of the cell and also supplies one of a base voltage or a reverse voltage to a cathode of the cell.

Description

Apparatus and method for driving an electroluminescent display device {APPARATUS AND METHOD FOR DRIVING ELECTRO-LUMINESCENCE DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display device, and more particularly, to a method for driving an electroluminescent display device capable of improving the brightness and lifetime of a panel.

Recently, various flat panel display devices that can reduce weight and volume, which are disadvantages of cathode ray tubes, have emerged. Such flat panel displays include a liquid crystal display, a field emission display, a plasma display panel, and an electro-luminescence (hereinafter, referred to as "EL"). Display elements).

Among them, the EL display element is a self-luminous element that emits a phosphor by recombination of electrons and holes, and is classified roughly into an inorganic EL using an inorganic compound and an organic EL using an organic compound as the phosphor. Such EL display elements have many advantages such as low voltage driving, self-luminous, thin film type, wide viewing angle, fast response speed and high contrast, and are expected to be the next generation display devices.

The organic EL display element is usually composed of an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, and a hole injection layer stacked between a cathode and an anode. In the organic EL display device, when a predetermined voltage is applied between the anode and the cathode, electrons generated from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode are transferred to the hole injection layer and the hole transport layer. It moves to the light emitting layer through. Accordingly, the light emitting layer emits light by recombination of electrons and holes supplied from the electron transporting layer and the hole transporting layer.

The driving apparatus of an active matrix EL display device using such an organic EL display device has pixels 28 arranged in regions defined by intersections of scan lines SL and data lines DL, as shown in FIG. The EL panel 20, the scan driver 22 for driving the scan lines SL of the EL panel 20, and the data driver 24 for driving the data lines DL of the EL panel 20. And a gamma voltage generator 26 supplying a plurality of gamma voltages to the data driver 24, a timing controller 27 and pixels 28 for controlling the data driver 24 and the scan driver 22. A power supply unit 15 for supplying power to each is provided.

In the EL panel 20, pixels 28 are arranged in a matrix form. The EL panel 20 is provided with a supply pad 10 that receives the supply voltage VDD from the power supply unit 15 and a base pad 12 that receives the ground voltage GND from the power supply unit 15. The supply voltage VDD supplied to the supply pad 10 is supplied to the respective pixels 28. In addition, the base voltage GND supplied to the base pad 12 is also supplied to the respective pixels 28.

The scan driver 22 sequentially drives the scan lines SL by supplying scan pulses to the scan lines SL.

The gamma voltage generator 26 supplies a gamma voltage having various voltage values to the data driver 24.

The data driver 24 converts the digital data signal input from the timing controller 27 into an analog data signal using the gamma voltage from the gamma voltage generator 26. The data driver 24 supplies the analog data signal to the data lines DL every time a scan pulse is supplied.

The timing controller 27 supplies a data control signal for controlling the data driver 24 and a scan control signal for controlling the scan driver 22 using synchronization signals supplied from an external system (eg, a graphics card). Create The data control signal generated by the timing controller 27 is supplied to the data driver 24 to control the data driver 24. The scan control signal generated by the timing controller 27 is supplied to the scan driver 22 to control the scan driver 22. In addition, the timing controller 27 supplies a digital data signal supplied from an external system to the data driver 24.

Each of the pixels 28 receives a data signal from the data line DL when a scan pulse is supplied to the scan line SL, and generates light corresponding to the data signal.

To this end, each of the pixels 28 includes an EL cell 0EL having a cathode connected to a base pad 12 that receives a base voltage GND from the power supply unit 15 as shown in FIG. SL is connected to the supply pad 10 which receives the supply voltage VDD from the data line DL and the power supply unit 15, and is connected to the anode of the EL cell OEL to drive the EL cell OEL. The cell driver 30 is provided.

The cell driver 30 includes a switching thin film transistor T1 in which a gate terminal is connected to the scan line SL, a source terminal is connected to the data line DL, and a drain terminal is connected to the first node N1, The driving thin film transistor T2 in which the gate terminal is connected to the node N1, the source terminal is connected to the supply pad 10, and the drain terminal is connected to the EL cell EL, the supply pad 10 and the first node ( The capacitor C connected between N1) is provided.

The switching thin film transistor T1 is turned on when a scan pulse is supplied to the scan line SL to supply a data signal supplied to the data line DL to the first node N1. The data signal supplied to the first node N1 is charged to the capacitor C and supplied to the gate terminal of the driving thin film transistor T2. The driving thin film transistor T2 controls the amount of current I supplied to the EL cell OEL from the power supply 15 supplying the supply voltage VDD in response to the data signal supplied to the gate terminal. ) The amount of light emitted. Since the data signal is discharged from the capacitor C even when the switching thin film transistor T1 is turned off, the driving thin film transistor T2 supplies the supply voltage VDD until the data signal of the next frame is supplied. The current I from the power supply unit 30 is supplied to the EL cell OEL so that the EL cell OEL maintains light emission. (The actual cell driver 30 may be set in various structures).

However, in the EL display element driving apparatus as described above, the current (or voltage) is supplied only to the anode of the EL cell OEL. In this way, when a current (or voltage) is applied only to the anode of the EL cell OEL, a predetermined charge is accumulated in the EL cell OEL, and light having a desired brightness is not generated by the accumulated charge. Indeed, as time passes (i.e., as charge accumulates), the luminance corresponding to the same data is gradually lowered.

Accordingly, an object of the present invention is to provide an apparatus and method for driving an electro-luminescence display device capable of improving luminance.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a driving device of a conventional organic electroluminescent display element.

FIG. 2 is a diagram showing a detailed configuration of the pixel shown in FIG. 1; FIG.

3 is a view showing a driving device of an organic electroluminescent display device according to an embodiment of the present invention.

FIG. 4 is a diagram showing a detailed configuration of the pixel shown in FIG. 3; FIG.

5 is a waveform diagram for supplying a reverse voltage to the cathode of the electro-luminescence cell shown in FIG. 4 at a time when one scan pulse can be supplied.

6A to 6G are waveform diagrams showing reverse voltages which are variously set at a time when one scan pulse shown in FIG. 5 can be supplied.

FIG. 7 is a waveform diagram for supplying a reverse voltage to the cathode of the electro-luminescence cell shown in FIG. 4 at a time when one frame can be supplied.

8A to 8G are waveform diagrams showing reverse voltages which are variously set at a time when one frame shown in FIG. 7 can be supplied.

<Description of Symbols for Main Parts of Drawings>

15,45: power supply 20,50: electro-luminescence panel

22,52: Scan Driver 24,54: Data Driver

26,56: gamma voltage generator 28,58: pixel

30,60: EL cell driver 10,40: supply pad

12,42: Basal Pad

In order to achieve the above object, a driving apparatus of an electro-luminescence display device according to an embodiment of the present invention, a plurality of electro-luminescence cells formed in the panel, a plurality of cell driver for driving the cell, And a power supply unit for supplying power to the panel, wherein the power supply unit supplies a supply voltage to the anode of the cell and supplies any one of a base voltage and a reverse voltage to the cathode of the cell.

In the driving device of the electro-luminescence display device, the power supply unit supplies the base potential to the cathode of the electro-luminescence cell for the time when the scan pulse is supplied to all the scan lines in one frame, and the The reverse voltage is supplied to the cathode of the electroluminescent cell.

In the driving apparatus of the electro-luminescence display device, the remaining time of one frame is a time when a scan pulse is supplied to the one scan line.

In the driving apparatus of the electro-luminescence display device, the remaining time of one frame is set to be shorter than the time when the scan pulse is supplied to the one scan line.

In the driving device of the electro-luminescence display device, a power supply unit supplies the reverse voltage to the cathode of the electro-luminescence cell for at least one of the frames driven for 1 second and the electro-lumines for other periods. The base potential is supplied to the cathode of the sense cell.

The time for supplying the reverse voltage to the cathode of the electro-luminescence cell for at least one frame in the driving device of the electro-luminescence display element is set to be shorter than during the one frame.

According to an embodiment of the present invention, there is provided a method of driving an electro-luminescence display device, in which a voltage is charged to pixels by scan pulses and data pulses supplied to scan lines and data lines, and charged to the pixels. Controlling the current supplied from the supply voltage to the anode of the electro-luminescence cell in response to the voltage, and light is generated in the electro-luminescence cell when the current is supplied to the anode of the electro-luminescence cell. Supplying a base voltage to the cathode of the electro-luminescent cell so as to be capable of removing the charge, and removing the charge remaining in the electro-luminescence cell after light is generated in the electro-luminescence cell. Applying a reverse voltage to the cathode of the luminescence cell.

In the method of driving the electro-luminescence display device, applying a reverse voltage to the cathode of the electro-luminescence cell may include a cathode of the electro-luminescence cell during a time when a scan pulse is supplied to all scan lines in one frame. The base potential is supplied, and the reverse voltage is supplied to the cathode of the electro-luminescence cell for the remaining time of the one frame.

In the method of driving the electro-luminescence display device, the remaining time of one frame is a time when a scan pulse is supplied to the one scan line.

In the method of driving the electro-luminescence display device, the remaining time of one frame is set to be shorter than the time when the scan pulse is supplied to the one scan line.

In the method of driving the electro-luminescence display device, applying a reverse voltage to the cathode of the electro-luminescence cell may be performed by applying the reverse voltage to the cathode of the electro-luminescence cell for at least one of the frames driven for 1 second. The reverse voltage is supplied and the base potential is supplied to the cathode of the electro-luminescence cell for another period.

In the method of driving the electro-luminescence display device, the time for supplying the reverse voltage to the cathode of the electro-luminescence cell for at least one frame is set to be shorter than during the one frame.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 3 to 8G.

3 is a view showing a driving device of an active matrix electro-luminescence display device according to an embodiment of the present invention.

Referring to FIG. 3, a driving apparatus of an active matrix EL display device according to an exemplary embodiment of the present invention includes pixels 58 arranged in regions defined by intersections of a scan line SL and a data line DL. The EL panel 50, the scan driver 52 for driving the scan lines SL of the EL panel 50, the data driver 54 for driving the data lines DL of the EL panel 50, and The gamma voltage generator 56 supplies a plurality of gamma voltages to the data driver 54, the timing controller 57 and the pixels 58 for controlling the data driver 54 and the scan driver 52, respectively. It is provided with a power supply unit 45 for supplying power.

In the EL panel 50, pixels 28 are arranged in a matrix form. The EL panel 50 has a supply pad 40 that receives the supply voltage VDD from the power supply unit 45 and a base pad that receives the reverse voltage Vr or the ground voltage GND from the power supply unit 45. 42) is installed. The supply voltage VDD supplied to the supply pad 40 is supplied to the respective pixels 58. The reverse voltage Vr or the base voltage GND supplied to the base pad 42 is also applied to each pixel. Field 58 is supplied. At this time, the base voltage GND is supplied to the base pad 42 while the EL panel 20 is normally driven, and the reverse voltage Vr is supplied to the base pad 42 for a predetermined time other than normal driving. do.

The scan driver 52 sequentially drives the scan lines SL by supplying scan pulses to the scan lines SL.

The gamma voltage generator 56 supplies a gamma voltage having various voltage values to the data driver 54.

The data driver 54 converts the digital data signal input from the timing controller 57 into an analog data signal using the gamma voltage from the gamma voltage generator 56. The data driver 54 supplies the analog data signal to the data lines DL every time a scan pulse is supplied.

The timing controller 57 supplies a data control signal for controlling the data driver 54 and a scan control signal for controlling the scan driver 52 using synchronization signals supplied from an external system (eg, a graphics card). Create The data control signal generated by the timing controller 57 is supplied to the data driver 54 to control the data driver 54. The scan control signal generated by the timing controller 57 is supplied to the scan driver 52 to control the scan driver 52. In addition, the timing controller 57 supplies a digital data signal supplied from an external system to the data driver 54.

Each of the pixels 58 receives a data signal from the data line DL when a scan pulse is supplied to the scan line SL, and generates light corresponding to the data signal.

To this end, each of the pixels 58 has an EL cell 0EL connected to a base pad 42 that receives a reverse voltage Vr and a base voltage GND from the power supply 45 as shown in FIG. 4. ) And a supply pad 40 that receives the supply voltage VDD from the scan line SL, the data line DL, and the power supply unit 45, and is connected to the anode of the EL cell OEL, and the EL cell ( And a cell driver 60 for driving the OEL.

The cell driver 60 includes a switching thin film transistor T1 in which a gate terminal is connected to a scan line SL, a source terminal is connected to a data line DL, and a drain terminal is connected to a first node N1, and a first The driving thin film transistor T2 in which the gate terminal is connected to the node N1, the source terminal is connected to the supply pad 40, and the drain terminal is connected to the EL cell EL, the supply pad 40 and the first node ( The capacitor C connected between N1) is provided.

The switching thin film transistor T1 is turned on when a scan pulse is supplied to the scan line SL to supply a data signal supplied to the data line DL to the first node N1. The data signal supplied to the first node N1 is charged to the capacitor C and supplied to the gate terminal of the driving thin film transistor T2. The driving thin film transistor T2 controls the amount of current I supplied to the EL cell OEL from the power supply 45 supplying the supply voltage VDD in response to the data signal supplied to the gate terminal. ) The amount of light emitted. Since the data signal is discharged from the capacitor C even when the switching thin film transistor T1 is turned off, the driving thin film transistor T2 supplies the supply voltage VDD until the data signal of the next frame is supplied. The current I from the power supply unit 45 is supplied to the EL cell OEL so that the EL cell OEL maintains light emission. (The actual cell driver 60 can be set in various structures).

At this time, the reverse voltage Vr supplied from the power supply unit 45 is periodically supplied to the base pad 42 connected to the cathode of the EL cell OEL for a predetermined time, and then supplied to the EL cell OEL. The charge remaining in the EL cell OEL is removed. As a result, since the amount of current flowing into the EL cell OEL can be controlled constantly, desired luminance is generated and the life of the panel is improved.

In detail, the EL cell OEL supplies only the current I from the power supply unit 45 that supplies the supply voltage VDD to the anode of the EL cell OEL until the data signal of the next frame is supplied. The EL cell OEL keeps light emission. In this way, when a current (or voltage) is applied only to the anode of the EL cell OEL, a predetermined charge is accumulated in the EL cell OEL, and light having a desired brightness is not generated by the accumulated charge. Accordingly, the reverse voltage Vr generated from the power supply section 45 is supplied to the cathode of the EL cell OEL for a predetermined time other than the normal operation of the EL panel. As a result, the electric charge accumulated in the EL cell OEL is removed and the amount of current flowing into the EL cell OEL can be controlled constantly, so that desired luminance is generated and the life of the panel is improved. During the normal operation of the EL panel, the base voltage GND is supplied from the power supply unit 45 to the base pad 42 connected to the cathode of the EL cell OEL to drive the EL panel normally.

On the other hand, the time that the reverse voltage (Vr) is supplied from the power supply unit 45 may be variously set. First, the power supply unit may apply the ground potential GND during the time when the scan pulse is applied to all the scan lines, and apply the reverse voltage vr at other times. This will be described in detail with reference to FIG. 5. In the present invention, one frame can be driven by dividing the time when the reverse voltage Vr is applied and the time when the scan pulse is applied. Here, the time when the reverse voltage Vr is applied may be set equal to the time when the scan pulse is applied to one scan line.

That is, in the present invention, if the EL panel 50 has i (i is a natural number) scan lines, one frame is driven by being divided by the time that i + 1 scan pulses can be supplied. In addition, the time at which the reverse voltage is applied from the time at which one scan pulse is supplied may be variously set. In detail, as shown in FIG. 6A, the reverse voltage Vr may be supplied during the time when one scan pulse is supplied, and the reverse voltage during the time when 2/4 scan pulse is supplied as shown in FIG. 6B. (Vr) can be supplied. As shown in FIG. 6C, the reverse voltage Vr may be supplied during the 6/8 scan pulse supply period, and as shown in FIG. 6D, the reverse voltage Vr during the 14/16 scan pulse supply period. ) Can be supplied. And, as shown in FIG. 6E, the reverse voltage Vr may be supplied during the time when 1/16 scan pulse is supplied, and as shown in FIG. 6F, the reverse voltage Vr during the time when 1/8 scan pulse is supplied. ) Can be supplied. In addition, as shown in FIG. 6G, the reverse voltage Vr may be supplied during the time when the 1/4 scan pulse is supplied. In this way, the time that the reverse voltage Vr is applied from the time when one scan pulse is supplied can be set in various ways to maximize the effect of supplying the reverse voltage Vr. In addition, even if the size of the EL panel 50 becomes larger or smaller, such a pulse can select a desired pulse, thereby maximizing its effect.

On the other hand, when the desired pulse is made at the time that one scan pulse can be supplied, when the pulse width is too short to see the effect, a pulse as shown in FIG. 7 may be used. That is, if the frame output for one second is 60 frames to supply the reverse voltage Vr generated from the power supply unit 45 to the cathode of the EL cell OEL without affecting the driving of the EL panel, up to 59 frames Normal operation is performed, and then a desired pulse is generated and output at a time when one frame can be supplied. The electric charge remaining in the EL cell OEL is removed by supplying the reverse voltage Vr to the cathode of the EL cell OEL at such a time that one frame can be supplied. In this case, one or more frames may be set. Here, the time when the reverse voltage is applied from the time that one frame can be supplied may be variously set. In detail, as shown in FIG. 8A, the reverse voltage Vr may be supplied during the time when one frame may be supplied, and during the time when 2/4 frames may be supplied as shown in FIG. 8B. The reverse voltage Vr can be supplied. Then, as shown in FIG. 8C, the reverse voltage Vr may be supplied during the time that 6/8 frames can be supplied, and as shown in FIG. 8D, the reverse voltage during the time when the 14/16 frames can be supplied. (Vr) can be supplied. Then, as shown in FIG. 8E, the reverse voltage Vr may be supplied for a time when 1/16 frame can be supplied, and as shown in FIG. 8F, a reverse voltage during the time when 1/8 frame can be supplied. (Vr) can be supplied. In addition, as shown in FIG. 8G, the reverse voltage Vr may be supplied for a quarter frame time. In this way, the time when the reverse voltage Vr is applied from the time when one frame is supplied may be variously set to maximize the effect of supplying the reverse voltage Vr. In addition, even if the size of the EL panel 50 increases or decreases, such a pulse can select a desired waveform to maximize its effect.

As described above, the driving apparatus and method of the electro-luminescence display element according to the present invention remove the electric charge accumulated by supplying a reverse voltage to the cathode of the EL cell for a period other than the normal operation of the panel. Since the amount of current flowing into the cell can be controlled constantly, the desired brightness can be output.

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 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.

Claims (12)

A plurality of electro-luminescence cells formed in the panel, A plurality of cell drivers for driving the cells; A power supply unit for supplying power to the panel; And the power supply unit supplies a supply voltage to the anode of the cell and supplies any one of a base voltage and a reverse voltage to the cathode of the cell. The method of claim 1, The power supply unit supplies the base potential to the cathode of the electro-luminescence cell for the time that the scan pulse is supplied to all the scan lines in one frame, and the reverse to the cathode of the electro-luminescence cell for the remaining time of the frame. A drive device for an electroluminescent display device, characterized by supplying a voltage. The method of claim 2, And a remaining time of the one frame is a time at which a scan pulse is supplied to the one scan line. The method of claim 2, The remaining time of the one frame is set to be shorter than the time that the scan pulse is supplied to the one scan line, the driving device of the electro-luminescence display device. The method of claim 1, The power supply unit supplies the reverse voltage to the cathode of the electro-luminescence cell for at least one of the frames driven for 1 second and supplies the base potential to the cathode of the electro-luminescence cell for another period. A drive device for an electroluminescent display device characterized by the above-mentioned. The method of claim 5, wherein And the time for supplying the reverse voltage to the cathode of the electroluminescent cell during the at least one frame is set shorter than during the one frame. A voltage is charged to the pixels by the scan pulse and the data pulse supplied to the scan line and the data line; Controlling a current supplied from the supply voltage to the anode of the electro-luminescence cell in response to the voltage charged in the pixels; Supplying a ground voltage to the cathode of the electro-luminescence cell so that light is generated in the electro-luminescence cell when a current is supplied to the anode of the electro-luminescence cell; And applying a reverse voltage to the cathode of the electro-luminescence cell to remove the charge remaining in the electro-luminescence cell after the light is generated in the electro-luminescence cell. A method of driving an electroluminescent display device. The method of claim 7, wherein The applying of the reverse voltage to the cathode of the electro-luminescence cell may supply the base potential to the cathode of the electro-luminescence cell during the time that the scan pulse is supplied to all the scan lines in one frame, and And driving the reverse voltage to the cathode of the electroluminescent cell for the remaining time. The method of claim 8, The remaining time of the one frame is a time for which the scan pulse is supplied to the one scan line. The method of claim 8, The remaining time of the one frame is set to be shorter than the time that the scan pulse is supplied to the one scan line, the method of driving an electro-luminescence display device. The method of claim 7, wherein The step of applying a reverse voltage to the cathode of the electro-luminescence cell comprises supplying the reverse voltage to the cathode of the electro-luminescence cell for at least one frame of a frame driven for 1 second and the electro for other periods. A method of driving an electro-luminescence display device, characterized by supplying a ground potential to the cathode of a luminescence cell. The method of claim 11, And the time for supplying the reverse voltage to the cathode of the electroluminescent cell during the at least one frame is set shorter than during the one frame.