KR20070035861A - Electron emission display device and control method of the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission display device and a control method thereof, and more particularly, to an electron emission display device and a method for controlling the maximum current according to the size of the frame data.

In the electron emission display device according to the present invention, a plurality of data lines and a plurality of scan lines are formed to cross each other, and a plurality of pixels are provided in an area where the data lines and the scan lines intersect, and anode electrodes are formed over the entire area. A pixel unit, a data driver for applying a data signal to the data line, a scan driver for sequentially applying a scan signal to the scan line, a power supply unit for applying power to the data driver and the scan driver, and an arbitrary reference current value. And a controller configured to adjust the voltage level so that a current value corresponding to the sum of video data input to the pixel portion does not exceed the reference current value.

Electron emission indicator, maximum current value, control method, frame data, voltage level

Description

Electron emission display device and control method of the same

1 is a view showing a conventional electron emission display device.

2 is a view showing an electron emission display device according to the present invention.

3 is a view showing an example of a control unit employed in the electron emission display device according to the present invention.

4 is a flowchart illustrating a control method of an electron emission display device according to the present invention.

5 is a diagram illustrating luminance characteristics adjusted according to a control method of an electron emission display device according to an exemplary embodiment of the present invention.

*** Description of the main symbols in the drawings ***

400: controller 430: second lookup table

410: data summing unit 440: voltage level control unit

420: First lookup table

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission display device and a control method thereof, and more particularly, to an electron emission display device that calculates a total sum of video data input to a pixel portion during one frame and limits a limit of a current value corresponding to the sum. And a control method thereof.

Recently, a flat panel display such as a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescent display (ELD), an electron emission display (EED), or the like Is actively being researched and developed. Among these, the electron emission display device includes an electron emission area that includes an electron emission device and emits an electron, and an image expression area that emits emitted electrons by colliding with a fluorescent layer to emit light. In particular, an electron emission display device using carbon nanotubes has advantages of a cathode ray tube (CRT) having excellent image characteristics such as high definition, high resolution, and a wide viewing angle, and a flat panel display characterized by light weight, thinness, and low power consumption. It is an ideal display device that combines bays. In general, an electron emission device has a method using a hot cathode and a cold cathode as an electron source. The electron-emitting devices using the cold cathode are Field Emitter Array (FEA), Surface Conduction Emitter (SCE), Metal-Insulator-Metal (MIM), Metal-Insulator-Semiconductor (MIS), and BSE (Ballistic). electron surface emitting) and the like are known.

The FEA type electron emitting device uses a low work function or high β function as an electron emission source and uses the principle that electrons are emitted by electric field difference in vacuum. Or devices that apply electron emission sources to nanomaterials have been developed.

The SCE type electron emission device is a device in which an electron emission portion is formed by providing a conductive thin film between two electrodes disposed to face each other on a substrate and providing a micro crack in the conductive thin film. The device utilizes a principle that electrons are emitted from the electron emission portion, which is the fine gap, by applying a voltage to an electrode to flow a current to the surface of the conductive thin film.

The MIM and MIS type electron emission devices each form an electron emission portion composed of a metal-dielectric layer-metal (MIM) and a metal-dielectric layer-semiconductor (MIS) structure, and are disposed between two metals or metals and semiconductors having a dielectric layer interposed therebetween. When a voltage is applied to the device, a device using the principle of emitting electrons while moving and accelerating from a metal having a high electron potential or a metal having a low electron potential toward the metal.

The BSE type electron emitting device forms an electron supply layer made of a metal or a semiconductor on an ohmic electrode by using the principle that the electrons travel without scattering when the size of the semiconductor is reduced to a dimension region smaller than the average diameter of electrons in the semiconductor. In addition, the insulating layer and the metal thin film are formed on the electron supply layer to emit electrons by applying power to the ohmic electrode and the metal thin film.

In the electron emitting device as described above, the emitted electron collides with the fluorescent layer and the phosphor emits light so that the luminance of the displayed image is changed according to the value of the input video data. Specifically, the value of the video data constitutes 8 bits of RGB data, respectively. That is, the value of the video data can be 0 (000000 ₍₂₎ ) to 255 (11111111 ₍₂₎ ), and the luminance of each pixel is expressed according to this value.

In order to adjust the luminance represented according to the value of the video data, a pulse width modulation (PWM) method or a pulse amplitude modulation (PAM) method is generally used.

The PWM method modulates the pulse width of the driving waveform applied to the data electrode according to the video data input from the data driver. When 255 is input as the video data value within the maximum available on-time, The pulse width is maximized to display the maximum luminance. When 127 is input as the video data value, the pulse width is 1/2 to decrease the luminance. On the other hand, in the PAM method, the pulse width is constant regardless of the input video data, but the luminance is controlled by changing the pulse voltage level of the driving waveform applied to the data electrode, that is, the pulse size, according to the input video data.

In such an electron emission display device, when video data of (R: 11111111 ₍₂₎ , G: 11111111 ₍₂₎ , B: 11111111 ₍₂₎ ) is input, that is, a video data value of 255 is input to the data driver, the input video is inputted. Regardless of the luminance level of the sum of the data, the pulse width or amplitude is modulated according to the video data to determine the luminance.

1 is a view showing a conventional electron emission display device.

Referring to FIG. 1, a conventional electron emission display device includes a pixel unit 10, a scan driver 20, a data driver 30, and a power supply 40.

The pixel portion 10 includes n scan lines S1, S2,... Sn, m data lines D1, D2, ... Dm, and an anode electrode ANODE, and the scan lines S1, S2, Sn is formed in the region where the data lines D1, D2, ... Dm cross each other. In this case, the anode electrode ANODE may be formed over the entire area of the pixel portion 10, and any one of the scan lines S1, S2,... Sn and the data lines D1, D2,... It may be used as a cathode electrode and the other one may be used as a gate electrode.

The scan driver 20 sequentially applies a scan signal to the plurality of scan lines S1, S2, ... Sn.

The data driver 30 applies a data signal corresponding to the input video data DATA to the plurality of data lines D1, D2, ... Dm.

The power supply 40 applies the first power source V1 and the second power source V2 to the data driver 30, and applies the third power source V3 and the fourth power source V4 to the scan driver 20. do.

In the conventional electron emission display as described above, when a large number of pixels 5 emit light with high brightness, the current flowing into the pixel portion 10 increases, and thus the load is applied to the power supply 30. There is a problem of having a high output.

Accordingly, an object of the present invention for solving the above-described conventional problems is to limit the amount of current flowing through the anode electrode according to the size of the frame data, thereby minimizing the capacity of the high-voltage power supply circuit, improving power consumption, and improving lifetime. The present invention provides an electronic emission display device and a control method thereof.

As a technical means for achieving the above-described technical problem, one side of the present invention is formed by crossing a plurality of data lines and a plurality of scanning lines, and having a plurality of pixels in an area where the data lines and the scanning lines cross each other, A pixel portion having an anode electrode formed thereon, a data driver for applying a data signal to the data line, a scan driver for sequentially applying a scan signal to the scan line, a power supply for applying power to the data driver and the scan driver And a controller configured to preset an arbitrary reference current value so as to adjust a voltage level such that a current value corresponding to the sum of video data input to the pixel portion does not exceed the reference current value. It is.

According to another aspect of the present invention, (a) generating frame data obtained by summing up video data input to the pixel portion during one frame period, and (b) presetting a predetermined reference current value, the current corresponding to the frame data. The present invention provides a method of controlling an electron emission display device, the method including adjusting a voltage level so that a value does not exceed the reference current value.

  Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

2 is a view showing an electron emission display device according to the present invention.

Referring to FIG. 2, the electron emission display device according to the present invention includes a pixel unit 100, a scan driver 200, a data driver 300, a controller 400, and a power supply 500.

The pixel unit 100 includes n scan lines S1, S2,... Sn, m data lines D1, D2, ... Dm, and an anode electrode ANODE, and the scan lines S1, S2, The plurality of pixels 50 are formed in an area where ... Sn) and the data lines D1, D2, ... Dm cross each other. In this case, the anode electrode ANODE may be formed over the entire area of the pixel portion 100, and any one of the scan lines S1, S2,... Sn and the data lines D1, D2,... It may be used as a cathode electrode and the other one may be used as a gate electrode.

The scan driver 200 sequentially applies a scan signal to the plurality of scan lines S1, S2,... Sn.

The data driver 300 applies a data signal corresponding to the input video data DATA to the plurality of data lines D1, D2,..., Dm.

The controller 400 presets an arbitrary reference current value and adjusts the voltage level so that a current value corresponding to the sum of video data input to the pixel unit 100 does not become equal to or greater than the reference current value. . Hereinafter, the sum of video data input to each of the plurality of pixels 50 during one frame is referred to as frame data. As an example, first, the reference current value, that is, the maximum current value that can flow to the anode is set to 4 mA. Therefore, if the amount of current flowing to the anode is 2 mA when the size of the frame data is 100, and the amount of current flowing to the anode is 5 mA when the size of the frame data is 200, the size of the frame data is 200. At this time, the amount of current flowing through the anode electrode is adjusted to 4mA, the maximum current value, not 5mA. The controller 400 varies the voltage level between the cathode electrode and the gate electrode in response to a current value that is adjusted differently according to the size of the frame data.

The power supply unit 500 applies the first power source V1 and the second power source V2 to the scan driver 200, and applies the third power source V3 and the fourth power source V4 to the data driver 300. do.

3 is a view showing an example of a control unit employed in the electron emission display device according to the present invention.

Referring to FIG. 3, the controller 400 employed in the electron emission display device according to the present invention includes a data summing unit 410, a first lookup table 420, a second lookup table 430, and a voltage level controller. 440.

The data summing unit 410 generates frame data obtained by summing video data input to each of the plurality of pixels 50 during one frame period. In this case, when the size of the frame data is large, it means that the emission rate of the pixel unit 100 is high or that there are many pixels 50 displaying high gradation images. That is, if the size of the frame data is large, it means that the amount of current flowing through the entire pixel portion 100 is large. If the size of the frame data is greater than or equal to a predetermined value, the amount of current flowing through the pixel portion 100 is controlled to control the total amount of pixels. The brightness of the unit 100 is reduced. The data summing unit 410 generates frame data for R, G, and B, respectively.

The first lookup table 420 stores information about a current value corresponding to the size of the frame data. For example, when a size of the frame data is 100, a current of 2 mA flows, information that a current of 5 mA flows at 150 and a current of 5 mA when the size of the frame data is 200 may be stored. However, if the reference current value, that is, the maximum current value that can flow in the pixel portion is set to 4 mA, the amount of current flowing in the pixel portion is stored as 4 mA, which is the maximum current value, not 5 mA even if the size of the frame data is 200.

The second lookup table 430 stores information about a voltage level corresponding to the current value stored in the first lookup table 420. For example, the voltage level (V _CG ) between the cathode electrode and the gate electrode corresponding to the current value of 2 mA is 5V, and the voltage level between the cathode electrode and the gate electrode corresponding to the current value of 4 mA is 10V. Can be.

The voltage level controller 440 adjusts the voltage level between the cathode electrode and the gate electrode according to the information stored in the first lookup table 420 and the second lookup table 430. That is, when the measured voltage value is detected as 5 mA greater than the maximum value of 4 mA, the voltage level controller 440 adjusts the voltage level between the cathode electrode and the gate electrode, and thus stores the 4 mA current value as stored in the second lookup table 430. It has a voltage level of 10V corresponding to.

4 is a flowchart illustrating a control method of an electron emission display device according to the present invention.

Referring to FIG. 4, the method for controlling the electron emission display device according to the present invention is implemented in the first steps ST100 to ST00.

The first step ST100 is to generate frame data obtained by summing video data input to the pixel unit during one frame period. First, in order to calculate the luminance level of video data in units of frames, R, G, and B video data are added in one frame, that is, the active period of one vertical synchronization signal, and thereafter, an average value of each of the R, G, and B frame data. To calculate. The average value shows the luminance level corresponding to the video data to be displayed. In other words, if the luminance level of the calculated average value is large, the screen is generally bright. If the luminance level of the calculated average value is small, it means that the screen is relatively dark.

In the second step ST200, an arbitrary reference current value is preset, and the voltage level is adjusted so that the current value corresponding to the frame data does not become equal to or greater than the reference current value. First, information about a current value corresponding to the size of the frame data is stored in the first lookup table. For example, when a size of the frame data is 100, a current of 2 mA flows, information that a current of 5 mA flows at 150 and a current of 5 mA when the size of the frame data is 200 may be stored. However, if the reference current value, that is, the maximum current value that can flow in the pixel portion is set to 4 mA, the amount of current flowing through the anode electrode is stored as 4 mA, which is the maximum current value, not 5 mA even when the size of the frame data is 200. The second lookup table stores information about a voltage level corresponding to the current value stored in the first lookup table. For example, the voltage level V _CG between the cathode electrode and the gate electrode corresponding to the current value of 2 mA is 5 V, and the voltage level between the cathode electrode and the gate electrode corresponding to the current value of 4 mA is 10 V, and the like. do. The voltage level between the cathode electrode and the gate electrode is adjusted according to the information stored in the first lookup table and the second lookup table. That is, if the measured current value is detected as 5mA greater than the maximum value of 4mA, the voltage level between the cathode electrode and the gate electrode is adjusted to have a voltage level of 10V corresponding to the 4mA current value.

5 is a diagram illustrating luminance characteristics adjusted according to a control method of an electron emission display device according to an exemplary embodiment of the present invention.

Referring to FIG. 5, reference numeral L1 denotes a luminance characteristic of a conventional electron emission display device. That is, the current value increases in response to the video data input without limiting the current. Therefore, when a large number of pixels emit light with high brightness, the amount of current flowing into the pixel portion becomes large, and a load is applied to the power supply portion, which causes a problem that the power supply portion has a high output.

Reference numeral L2 denotes a luminance characteristic of the electron emission display device according to the present invention. That is, the reference current to limit the maximum value of the current is set in advance so that even if the sum of the frame data, i.e., the video data input during one frame, is larger than or equal to the predetermined size, the current higher than the reference current does not flow. In this case, the reference current may be changed in proportion to the passage of time when the same image is continuously displayed in the pixel portion as shown by reference numerals L4 to L6.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, it will be understood by those skilled in the art that various modifications are possible within the scope of the technical idea of the present invention.

According to the electron emission display device and the control method thereof according to the present invention, by limiting the amount of current flowing in the pixel portion corresponding to the size of the frame data, it is possible to minimize the capacity of the high-voltage power supply circuit, improve power consumption and lifespan It can be improved, thereby obtaining the effect of ensuring stability.

Claims (7)

A pixel portion in which a plurality of data lines and a plurality of scan lines are formed to cross each other, and a plurality of pixels are provided in an area where the data lines and the scan lines intersect, and an anode electrode is formed over the entire area; A data driver for applying a data signal to the data line; A scan driver which sequentially applies a scan signal to the scan line; A power supply unit applying power to the data driver and the scan driver; And And a controller configured to preset an arbitrary reference current value so as to adjust a voltage level so that a current value corresponding to the sum of video data input to the pixel portion is not greater than or equal to the reference current value. The method of claim 1, The control unit A data adder configured to generate frame data obtained by adding the video data input to each of the plurality of pixels during one frame period; A first lookup table for storing information about the current value corresponding to the size of the frame data; A second lookup table for storing information about the voltage level corresponding to the current value; And And a voltage level controller configured to adjust the voltage level between the cathode electrode and the gate electrode according to information stored in the first lookup table and the second lookup table. The method of claim 2, And the cathode electrode is connected to any one of the data line and the scan line, and the gate electrode is connected to the other of the data line and the scan line. The method of claim 2, The data summing unit An electron emission display device for generating the frame data for each of R, G, and B. (a) generating frame data obtained by summing video data input to the pixel unit during one frame period; And and (b) setting a predetermined reference current value to adjust a voltage level so that a current value corresponding to the frame data does not become equal to or greater than the reference current value. The method of claim 5, And the reference current value is set differently according to a time when the same image is continuously displayed on the pixel portion. The method of claim 6, And the reference current value is set lower as the time for which the same image is continuously displayed in the pixel portion is long.

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