KR100806818B1 - A Display Apparatus using Electroluminescent Device and A Method for Driving The Same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display device and a method of driving the same, which reduce power consumption due to driving by controlling the amount of charge discharged from the panel when the panel is initialized. An electroluminescent display of a panel comprises: a panel comprising a plurality of scan lines, a plurality of data lines intersecting the scan lines, and a plurality of electroluminescent elements positioned at intersections of the plurality of scan lines and the plurality of data lines; A data signal applying unit for providing data signals to the plurality of data lines; A discharge line for discharging a charge charged in the panel; Switching means for connecting the plurality of data lines to any one of the data signal applying unit and the discharge line; Discharge control means connected to the discharge line to maintain the voltage of the panel at a constant level by controlling the amount of charge discharged from the panel; It includes a coil and a diode connected between the discharge control means and the discharge line.

Electroluminescent Display, Data Line, Scan Line, Discharge Line

Description

A Display Apparatus using Electroluminescent Device and A Method for Driving The Same}

1 is a cross-sectional view of a typical organic light emitting display device

2 is a diagram illustrating a simple matrix electroluminescent display device according to the related art.

3 illustrates driving waveforms of the electroluminescent display of FIG. 2.

4 is a diagram illustrating an electroluminescent display device according to a first embodiment of the present invention.

5a to 5g show a preferred embodiment of the discharge control means of the present invention

6 illustrates driving waveforms of an electroluminescent display device according to a first exemplary embodiment of the present invention.

7 illustrates an electroluminescent display device according to a second embodiment of the present invention.

8 illustrates driving waveforms of an electroluminescent display device according to a second exemplary embodiment of the present invention.

<Description of Symbols in Drawings>

100: panel 200: scan driver

300: data signal applying unit 400: discharge line

500: discharge control means 600: capacitor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display and a driving method thereof, and more particularly, to an electroluminescent display and a driving method thereof capable of significantly reducing power consumption required for driving.

Recently, various flat panel displays capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have been widely used. Such flat panel displays include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), electroluminescent (EL) displays, and the like. There is this.

Among them, electroluminescent display devices are self-luminous devices for emitting phosphors by recombination of electrons and holes, and inorganic electroluminescent devices (also referred to as "LEDs") using inorganic compounds as their phosphors and organic fields using organic compounds. It is roughly referred to as a light emitting element (also referred to as "OLED"). Such an electroluminescent display device has an advantage in that the response speed is remarkably faster than a passive light emitting device requiring a separate light source like a liquid crystal display device. In addition, the electroluminescent display has many advantages such as low voltage driving, self-luminous, thin film type, wide viewing angle, fast response speed, and high contrast, and is expected to be the next generation display device.

1 is a cross-sectional view of a general organic electroluminescent device for explaining the light emission principle of the electroluminescent device. As shown in FIG. 1, an organic light emitting display device includes an electron injection layer 2, an electron transport layer 3, an emission layer 4, a hole transport layer 5, and a hole between a cathode 1 and an anode 7. The injection layer 6 has a laminated structure sequentially.

When a voltage is applied between the anode 7 as the transparent electrode and the cathode 1 as the metal electrode, electrons generated from the cathode 2 are transferred to the light emitting layer 4 through the electron injection layer 2 and the electron transport layer 3. Move. In addition, holes generated from the anode 7 move to the light emitting layer 4 through the hole injection layer 6 and the hole transport layer 5. Accordingly, in the light emitting layer 8, light is generated by collision between electrons and holes supplied from the electron transporting layer 6 and the hole transporting layer 10 and recombination. This light is emitted to the outside through the anode 7, which is a transparent electrode, so that an image is displayed.

The organic EL device may be driven by a simple matrix method and an active matrix method using a thin film transistor (TFT). The simple matrix method is a method in which the anode and the cathode are orthogonal and the cathode line and the anode line are selected and driven. The active matrix method is a driving method in which a thin film transistor and a capacitor are integrated in each pixel to maintain a voltage by capacitor capacity. to be.

FIG. 2 is a diagram illustrating a simple matrix type electroluminescent display device according to the related art, and FIG. 3 is a diagram illustrating a driving waveform of the electroluminescent display device of FIG. 2.

As shown in FIG. 2, in a typical electroluminescent display, a plurality of light emitting cells composed of the electroluminescent elements 11 are arranged in a matrix at a portion where a plurality of scan lines SL and data lines DL cross each other. The panel 10 includes a scan driver 20 for sequentially applying scan pulses to the plurality of scan lines SL, and a data driver 30 for applying data signals to the data lines DL.

Each of the electroluminescent elements 11 equivalently represented by a diode connected between the data line DL and the scan line SL is selected when a scan pulse is applied to the scan line SL, which is a cathode, and the data line, which is an anode. Light corresponding to the data signal, that is, the current signal, supplied to the DL is emitted. In other words, each electroluminescent element 11 receives a forward voltage by applying a negative scan pulse to a corresponding scan line SL and a positive current according to a data signal to a corresponding data line DL. It will emit light. On the contrary, the reverse voltage is applied to the electroluminescent element 11 corresponding to the scan line SL which is not selected so that the light emission does not occur. That is, the electroluminescent element 11 that emits light is charged in the forward direction, while the electroluminescent element 11 that does not emit light is charged in the reverse direction. In order to discharge the charged charges before applying the scan pulse for the next selection of the scan line SL, each data line DL connected to the power source of the data driver 30 is grounded from the power source. : Discharging the electric charges charged in the panel by switching to Vss).

Accordingly, as shown in FIG. 3, the electroluminescent display of the related art described above has each electroluminescent element 11 having an output voltage of Vss each time the scan line SL is sequentially selected. Swing to the voltage required to drive

Also, the electroluminescent element 11 corresponding to the unselected scan line SL operates like a parasitic capacitor in a state in which a reverse voltage is applied.

Therefore, the electroluminescent display of the prior art consumes a lot of driving power that is used for driving without being used to emit light, and there is a problem in that it takes a loss in response speed as the swing time is long. In addition, since the electric charges charged at the time of initialization of the panel are discharged to the ground portion, waste of power was severe.

The present invention has been made to solve the problems of the prior art, an object of the present invention is to adjust the amount of charge discharged from the panel during initialization of the panel by maintaining the voltage of the panel at a constant level of power consumption according to the driving The present invention provides an electroluminescent display and a driving method thereof capable of reducing the number of pixels.

Another object of the present invention is to minimize the waste of power by recovering and reusing some of the charge discharged from the panel during initialization of the panel, and to adjust the amount of charge discharged from the panel to maintain a constant voltage level of the panel. The present invention provides an electroluminescent display and a driving method thereof capable of reducing power consumption.

In order to achieve the above object, an embodiment of the electroluminescent display device of the present invention comprises a plurality of scan lines, a plurality of data lines intersecting the scan line, and the intersection of the plurality of scan lines and a plurality of data lines. A panel including a plurality of electroluminescent elements positioned in the portion; A data signal applying unit for providing data signals to the plurality of data lines; A discharge line for discharging a charge charged in the panel; Switching means for connecting the plurality of data lines to any one of the data signal applying unit and the discharge line; Discharge control means connected to the discharge line to maintain the voltage of the panel at a constant level by controlling the amount of charge discharged from the panel; It includes a coil and a diode connected between the discharge control means and the discharge line.

Another embodiment of the electroluminescent display of the present invention for achieving the above object is a plurality of scan lines, a plurality of data lines intersecting the scan line, and the intersection of the plurality of scan lines and a plurality of data lines. A panel including a plurality of electroluminescent elements positioned in the portion; A data signal applying unit for providing data signals to the plurality of data lines; A discharge line for discharging a charge charged in the panel; First switching means for connecting the plurality of data lines to any one of the data signal applying unit and the discharge line; Discharge control means for maintaining the voltage of the panel at a constant level by controlling the amount of charge discharged from the panel; A coil and a diode connected between said discharge control means and said discharge line; Charge recovery means for recovering charge discharged from the panel; And a second switching means for connecting the discharge line to any one of the discharge control means and the charge recovery means.

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Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for common configurations.

4 is a diagram illustrating an electroluminescent display device according to a first embodiment of the present invention.

As shown in FIG. 4, the electroluminescent display according to the first embodiment of the present invention includes a plurality of scan lines SL ₁ , SL ₂ ,-, SL _{N -1} , SL _N : SL, and the plurality of scan lines. Data lines DL ₁ , DL ₂ ,-, DL _{M -1} , DL _M : DL, which intersect the scan line SL of, and the plurality of scan lines SL and the data line DL intersect. A panel 100 including a plurality of electroluminescent elements 110 formed in a portion is provided.

In addition, the scan driver 200 for sequentially applying scan pulses to the plurality of scan lines SL, the data signal applying unit 300 for applying data signals to the data lines DL, and the panel 100. A discharge line 400 for discharging the charged charge. The data signal applying unit 300 and the discharge line 400 are selectively connected to the plurality of data lines DL by the switching means SW1. One end of the discharge line 400 is connected to the discharge control means 500 for maintaining the voltage of the panel at a constant level by adjusting the amount of charge discharged from the panel.

5a to 5g are views showing a preferred embodiment of the discharge control means 500.

As shown in Figure 5a, the discharge control means 500 of the present invention may be a power source (510). That is, by directly connecting the discharge line 400 to the power source 510, the voltage of the panel 100 is controlled to be discharged only to the voltage of the power source 510 and at the same time, the charge charged in the panel 100 is recovered to the power source 510. You can also On the other hand, in order to prevent the instantaneous high voltage is applied to the power supply 510, as shown in FIG. 5B, a resistor 511 and / or a capacitor 512 is provided between the power supply 510 and the discharge line 400. FIG. You can also connect.

In addition, in order to allow the current to flow only in the direction of the power source 510 and to prevent the flow in the opposite direction, as shown in FIG. 5C, the first diode 513 may be connected between the power source 510 and the discharge line 400. In order to increase the rate at which the charge charged in the panel 100 is recovered to the power source 510, a coil 514 is further added between the first diode 513 and the discharge line 400 as shown in FIG. 5D. You can also connect. In this case, in order to prevent reverse current from the coil 550, as shown in FIG. 5E, the second diode 515 may be further connected.

Meanwhile, as illustrated in FIG. 5F, the zener diode 520 may be used as the discharge control means 500 of the present invention. Zener diode 520 has a property of being stable at a constant voltage (V _zener ) when the voltage is applied in the reverse direction. At first, the zener diode 520 lowers the voltage of the panel 100 by discharging a charge charged in the panel 100, and then a constant voltage. When V _zener is reached, the voltage of the panel 100 is maintained by preventing further discharge.

In addition, the discharge control means 500 of the present invention may be implemented using a comparator 531 and a transistor 532, as shown in Figure 5g, the first input terminal of the comparator 531 discharge line 400 The voltage of the panel 100 is applied, a reference voltage V _Ref is applied to the second input terminal of the comparator 532, and a gate of the transistor 532 is connected to an output terminal of the comparator 531. And on / off in accordance with the output signal from the output terminal. That is, the transistor 532 is turned on only when the voltage of the panel 100 is greater than the reference voltage V _Ref . The source of the transistor 532 is connected to the discharge line 400 and the drain is connected to the ground so that the charge of the panel 100 is discharged to the ground only when the transistor 532 is on. As a result, when the voltage of the panel 100 reaches the reference voltage V _Ref , the transistor 532 is turned off so that no further discharge occurs, and the panel 100 maintains the reference voltage V _Ref . Will be done.

Hereinafter, the driving of the electroluminescent display device according to the first embodiment of the present invention described above will be described with reference to FIG. 6.

6 is a diagram illustrating driving waveforms of an electroluminescent display device according to a first exemplary embodiment of the present invention.

First, the scan line SL _n is selected by applying a negative first scan pulse to the n-th scan line SL _n . Each data line DL is connected to the data signal applying unit 300 by the switching means SW1 to receive a data signal while the first scan pulse of the negative polarity is applied, and the selected scan line SL _n is applied. Among the electroluminescent elements 110 corresponding to the electroluminescent element 110 in which the corresponding data line DL receives a positive data signal, the electroluminescent element 110 emits light.

As such, after the selection of the n th scan line SL _n is completed, the panel 100 may be charged to initialize the panel 100 before the selection of the n + 1 th scan line SL _{n + 1} . Discharge the charge. That is, each data line DL is connected by the switching means SW1 to the discharge regulating means 500 of the present invention shown in FIGS. The voltage of 100 is maintained at a constant voltage, for example, a power supply voltage, a zener diode voltage V _zener , or a reference voltage V _Ref . For convenience of description, the constant voltage is represented as a zener diode voltage V _{zener in} FIG. 6.

Then, select the type of scan lines (SL _{n +1)} by applying a second scan pulse of a negative polarity to the n + 1 th scan line (SL _{n +1).} While the second scan pulse of the negative polarity is applied, each data line DL is connected to the data signal applying unit 300 again by the switching means SW1 to receive the data signal.

In the conventional electroluminescent display, since the output voltage of the data driver has to swing from the ground (Vss) to a voltage required for driving each electroluminescent device, the consumption of driving power is great, but according to the first embodiment of the present invention, Since the voltage of the panel 100 is maintained at a constant voltage, for example, a power supply voltage, a zener diode voltage (V _zener ), or a reference voltage (V _Ref ) even after discharge with respect to the charge charged in the panel 100, the data signal The output voltage of the applying unit 300 only needs to swing from the predetermined voltage to a voltage required for driving the electroluminescent elements 110, and as a result, power consumption required for driving the panel can be reduced.

7 is a diagram illustrating an electroluminescent display device according to a second embodiment of the present invention.

As shown in FIG. 7, the electroluminescent display device according to the second embodiment of the present invention includes a plurality of scan lines SL ₁ , SL ₂ ,-, SL _{N -1} , SL _N : SL, and the plurality of scan lines. Data lines DL ₁ , DL ₂ ,-, DL _{M -1} , DL _M : DL, which intersect the scan line SL of, and the plurality of scan lines SL and the data line DL intersect. A panel 100 including a plurality of electroluminescent elements 110 formed in a portion is provided. In addition, the scan driver 200 for sequentially applying scan pulses to the plurality of scan lines SL, the data signal applying unit 300 for applying data signals to the data lines DL, and the panel 100. A discharge line 400 for discharging the charged charge. The data signal applying unit 300 and the discharge line 400 are selectively connected to the plurality of data lines DL by the first switching means SW1. The configuration so far is the same as in the first embodiment of the present invention.

The second embodiment of the present invention differs from the first embodiment in that it includes a capacitor 600 as a charge recovery means for recovering the charge discharged from the panel 100, and the capacitor 600 and the first embodiment. The discharge control means 500 of the example is selectively connected to the discharge line 400 by the second switching means (SW2).

The driving of the electroluminescent display device according to the second embodiment of the present invention described above will be described with reference to FIG. 8. 8 illustrates driving waveforms of an electroluminescent display according to a second exemplary embodiment of the present invention.

First, the scan line SL _n is selected by applying a negative first scan pulse to the n-th scan line SL _n . Among the electroluminescent devices 110 corresponding to the selected scan line SL _n , the corresponding data line DL is turned on to emit light when the electroluminescent device 110 receiving the positive data signal is turned on.

As such, after the selection of the n th scan line SL _n is completed, the panel 100 may be charged to initialize the panel 100 before the selection of the n + 1 th scan line SL _{n + 1} . The process of discharging the charge is as follows.

Each data line DL is connected to the discharge line 400 by the first switching means SW1, and the discharge line 400 is connected to the capacitor 600 as the charge recovery means by the second switching means SW2. By being connected, the charge charged in the panel 100 is recovered to the capacitor 600, and as a result, the voltage of the data line DL is lowered. When a certain amount of charge is accumulated in the capacitor 600, the connection between the capacitor 600 and the discharge line 400 is disconnected by the second switching means SW2. Instead, the discharge line 400 is connected to the discharge control means 500 of the present invention shown in FIGS. 5A to 5G to continue the discharge of the charge charged in the panel 100, and the voltage of the data line DL. When this constant voltage, for example, the power supply voltage, the zener diode voltage V _zener , or the reference voltage V _Ref is reached, the discharge is stopped. In FIG. 8, a zener diode voltage V _zener is shown for convenience of description, but others are not excluded.

Then, select the type of scan lines (SL _{n +1)} by applying a second scan pulse of a negative polarity to the n + 1 th scan line (SL _{n +1).}

While the negative first scan pulse is applied, each data line DL is still connected to the discharge line 400 by the first switching means SW1 and the discharge line 400 is connected to the second switching means ( SW2) is again connected to the capacitor 600 which is a charge recovery means. As a result, each data line DL is electrically connected to the capacitor 600, and the voltage applied to the panel is raised to the capacitor voltage V _cap by receiving charge from the capacitor 600. Subsequently, the data line DL is connected to the data signal applying unit 300 to receive the data signal instead of being disconnected from the discharge line 400 by the first switching means SW1. A voltage having a magnitude required to drive 110 is applied to the panel 100 through the data line DL.

According to the second embodiment of the present invention, the voltage of the panel 100 remains constant even after discharge with respect to the charge charged in the panel 100, for example, a power supply voltage, a zener diode voltage V _zener , or a reference voltage V _Ref. In addition, since the capacitor voltage V _cap is already applied to the panel 100 by reusing the charge that has been recovered to the capacitor 600, the output voltage of the data signal applying unit 300 is the capacitor voltage ( V from the _cap), and only when the swing voltage required for driving the respective light emitting element 110, it is possible as a result to reduce the power consumption required for driving the panel.

As described above, according to the present invention, the voltage of the data line is set to a constant voltage, for example, a power supply voltage, a zener diode voltage (V _zener ), or a reference voltage (V _Ref ) even after discharging the charges charged in the data line. Since it is maintained, the output voltage of the data signal applying unit 300 only needs to swing from such a constant voltage to a voltage necessary for driving each electroluminescent element. Therefore, it has the effect of reducing the power consumption required for driving the panel.

In addition, it has an effect of reducing the overall power consumption in that the discharged charge is recovered and recycled.

As a result, assuming that the same battery is used, it has the effect of increasing the use time of the product to which the electroluminescent display is applied, for example, a portable device.

Claims (19)

A panel including a plurality of scan lines, a plurality of data lines crossing the scan lines, and a plurality of electroluminescent elements positioned at intersections of the plurality of scan lines and the plurality of data lines; A data signal applying unit for providing a data signal to the plurality of data lines; A discharge line for discharging a charge charged in the panel; Switching means for connecting the plurality of data lines to any one of the data signal applying unit and the discharge line; Discharge control means connected to the discharge line to maintain the voltage of the panel by controlling an amount of charge discharged from the panel; And And a coil and a diode connected between the discharge control means and the discharge line. The method of claim 1, And the discharge control means is a power source. The method of claim 2, And a resistor and a capacitor are connected between the power supply and the discharge line, respectively. The method of claim 2, And a diode is connected between the power supply and the discharge line. delete The method of claim 2, And a first diode and a second diode connected between the power supply and the discharge line, and further connecting a coil between the first and second diodes. The method of claim 1, And the discharge control means is a zener diode. The method of claim 1, And the discharge control means comprises a comparator and a transistor. The method of claim 8, wherein the first input terminal of the comparator is connected to the discharge line, the reference voltage V _Ref is applied to the second input terminal of the comparator, and the gate of the transistor is connected to the output terminal of the comparator. And connected on / off according to an output signal from the output terminal, a source of the transistor is connected to the discharge line, and a drain is connected to the ground. A panel including a plurality of scan lines, a plurality of data lines crossing the scan lines, and a plurality of electroluminescent elements positioned at intersections of the plurality of scan lines and the plurality of data lines; A data signal applying unit for providing a data signal to the plurality of data lines; A discharge line for discharging a charge charged in the panel; First switching means for connecting the plurality of data lines to any one of the data signal applying unit and the discharge line; Discharge control means for maintaining the voltage of the panel at a constant level by controlling the amount of charge discharged from the panel; A coil and a diode connected between the discharge control means and the discharge line; Charge recovery means for recovering charge discharged from the panel; And And a second switching means for connecting the discharge line to any one of the discharge control means and the charge recovery means. The method of claim 10, And the charge recovery means is a capacitor. The method of claim 10, And the discharge control means is a zener diode. The method of claim 10, And said discharge control means comprises a comparator and a transistor. The gate of the transistor of claim 13, wherein the first input terminal of the comparator is connected to the discharge line through the second switching means, and the reference voltage V _Ref is applied to the second input terminal of the comparator. Is connected to an output terminal of the comparator and on / off according to an output signal from the output terminal, a source of the transistor is connected to the discharge line, and a drain is connected to the ground. The method of claim 10, And the discharge control means is a power source. delete delete delete delete

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