KR20070073032A - Method for driving display panel and apparatus thereof - Google Patents

Abstract

A method and an apparatus for driving a display panel is provided to reduce EMI(Electro Magnetic Interference) radiation amounts by adjusting the rising slope of an address voltage according to a line load rate. An apparatus for driving a display panel includes a display panel, a load rate calculation unit(26), and a slope adjusting unit(27). The display panel includes discharge cells formed by X, Y, and address electrodes, and drives the discharge cells by applying scan and data signals during reset, address, and sustain periods for every sub-field. The load rate calculation unit calculates a load rate, that is, the ratio of discharge cells generating a display discharge in the discharge cells. The slope adjusting unit adjusts a rising slope, which rises from a first level to a second level, according to the load rate.

Description

Method for driving display panel and driving apparatus thereof

1 is a perspective view illustrating a structure of a plasma display panel of a three-electrode surface discharge method as an embodiment to which a method of driving a plasma display panel according to the present invention is applied.

2 is a block diagram showing a driving apparatus of a plasma display panel as a preferred embodiment of the present invention.

3 is a timing diagram illustrating a driving method of driving a unit frame composed of a plurality of sub-fields in the method of driving a plasma display panel according to the present invention.

4 is a timing diagram illustrating an embodiment of driving signals applied to respective electrode lines with respect to one subfield according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel driving method and a driving apparatus thereof, and more particularly, to a display panel driving method and a driving apparatus for displaying an image by repetitive discharge for a short time by using electrical energy of high voltage and high frequency. It is about.

As flat panel display devices, plasma display panels (PDPs), which are easy to manufacture large panels, have attracted attention. A plasma display panel is a display device that displays an image by using a discharge phenomenon. In general, a plasma display panel can be classified into a direct current type and an alternating current type according to the type of driving voltage. Due to the disadvantages, the development of the AC plasma display panel has been made a lot.

An AC plasma display panel includes a three-electrode AC surface discharge type plasma display panel having three electrodes and driven by an AC voltage. A typical three-electrode surface discharge type plasma display panel is composed of a multi-layered plate, which is spatially advantageous because it can provide a thinner, lighter, and wider screen than a conventional cathode ray tube (CRT).

As an example of a conventional plasma display panel, a three-electrode surface discharge plasma display panel, a driving apparatus thereof, and a driving method thereof are disclosed in US Patent No. 6,744,218 (name: Method of driving a plasma display panel in which the). width of display sustain pulse varies).

The plasma display panel includes a plurality of display cells, and one display cell includes three discharge cells (red, green, and blue), and expresses the gray level of an image by adjusting the discharge state of the discharge cells. .

In the plasma display panel, discharge cells are formed in a region where the sustain electrode pairs and the address electrode of the X and Y electrodes are alternately arranged side by side. A plurality of sub-fields according to gray scale weights exist for each time frame grayscale display, and a reset cycle, an address cycle, and a sustain discharge cycle exist for each sub-field, thereby driving the plasma display panel. do.

At this time, all the discharge cells are initialized in the reset cycle. In the next address period, a scan pulse is sequentially applied to each of the Y electrodes, and an address voltage synchronized with the scan pulse is applied to an address electrode corresponding to the discharge cell to be displayed among the discharge cells, thereby displaying the discharge. Select the cell. In the subsequent sustain discharge cycle, sustain pulses are applied to the X electrode and the Y electrode so that the sustain discharge can occur only in the discharge cells to be displayed, thereby expressing the image.

In the address period, there are rising and falling portions for applying an address voltage, and the slope of the rising address voltage waveform varies with the load ratio. For example, when the load ratio is large, the capacitance of the panel is reduced, and thus the time constant is decreased, and thus the slope of the rising address voltage waveform is increased.

In this case, when the slope of the rising address voltage waveform becomes large, a change in current occurs rapidly, and thus there is a problem in that EMI (Electro-Magnetic Interference) emissions increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a display panel driving method and a driving apparatus thereof capable of reducing the amount of EMI radiation by adjusting the inclination of the address voltage in accordance with the load ratio.

According to the present invention, for a display panel in which discharge cells are formed by the X electrode, the Y electrode, and the address electrode, there are a plurality of sub-fields according to respective gray weights for time division gray scale display for each frame as a display period. There is a reset period, an address period, and a sustain discharge period in each sub-field, and a scan signal is sequentially applied to the Y electrodes in the address period, and discharge cells to be displayed among the discharge cells. A data signal rising from a first level to a second level is applied to the address electrode of the cell to select and drive a discharge cell to be displayed, and a load ratio, which is a ratio of discharge cells that cause display discharge among the discharge cells, is calculated. Load factor calculation step; And a tilt adjusting step of adjusting a rising slope rising from the first level to the second level according to the load ratio.

In the inclination adjustment step, when the load ratio is large, the rising slope is adjusted to be small, and when the loading ratio is small, the rising slope is preferably adjusted to be large.

Preferably, in the load factor calculation step, the load factor is calculated in subfield units.

In the load factor calculation step, the load factor is calculated in units of respective address electrodes, and in the gradient control step, the rising slope of each of the address electrodes is adjusted.

According to another aspect of the present invention, for a display panel in which discharge cells are formed by the X electrode and the Y electrode and the address electrode, there are a plurality of sub-fields according to respective gray weights for time division gray scale display for each frame as a display period. And a reset period, an address period, and a sustain discharge period exist in each of the sub-fields, and during the address period, a scan signal is sequentially applied to the Y electrodes, and is displayed among the discharge cells. A data signal rising from the first level to the second level is applied to the address electrodes of the discharge cells to select and drive the discharge cells to be displayed, and the load factor which is the ratio of the discharge cells causing the display discharge among the discharge cells. The calculated load factor calculation unit; And a tilt controller configured to adjust a rising slope rising from the first level to the second level according to the load ratio.

According to the present invention, the amount of EMI radiation can be reduced by adjusting the rising slope of the address voltage according to the load ratio.

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

1 is a perspective view showing a structure of a plasma display panel driving method and a driving apparatus thereof according to an embodiment of the present invention.

Referring to the drawings, between the front and rear glass substrates 10 and 13 of the surface discharge plasma display panel 1, the address electrode lines A _{R1 to} A _Bm , the dielectric layers 11 and 15, and the Y electrode line (Y ₁ to Y _n ), X electrode lines (X ₁ to X _n ), fluorescent layer 16, partition wall 17, and magnesium monoxide (MgO) layer 12 as a protective layer are provided.

The address electrode lines A _{R1 to} A _Bm are formed in a predetermined pattern on the front side of the rear glass substrate 13. The lower dielectric layer 15 is applied to the entire surface in front of the address electrode lines A _{R1 to} A _Bm . In front of the lower dielectric layer 15, barrier ribs 17 are formed in a direction parallel to the address electrode lines A _{R1 to} A _Bm . The partition walls 17 function to partition the discharge area of each discharge cell 14 and to prevent optical cross talk between the discharge cells 14. The fluorescent layer 16 is formed on the inner surface of the space formed between the lower dielectric layer 15 and the partition walls 17 formed on the rear glass substrate 13.

The X electrode lines X ₁ to X _n and the Y electrode lines Y ₁ to Y _n have a constant pattern on the rear side of the front glass substrate 10 to be orthogonal to the address electrode lines A _{R1 to} A _Bm . Is formed. Each intersection sets a corresponding discharge cell 14. Each X electrode line (X _{1 to} X _n ) and each Y electrode line (Y _{1 to} Y _n ) are combined with a transparent electrode line made of a transparent conductive material such as indium tin oxide (ITO) and a metal electrode line for increasing conductivity. Is formed. Here, the X electrode lines X ₁ to X _n become sustain electrodes in the respective discharge cells 14, and the Y electrode lines Y ₁ to Y _n correspond to scan electrodes in the respective discharge cells 14. And become an address electrode in the discharge cell 14 of each of the address electrode lines A _{R1 to} A _Bm .

2 is a block diagram showing a driving apparatus of a plasma display panel as a preferred embodiment of the present invention.

Referring to the drawings, the driving device 20 of the plasma display panel 1 includes an image processor 21, a logic controller 22, an address driver 23, an X driver 24, a Y driver 25, and a load factor calculation. A part 26 and the inclination adjustment part 27 are included. The driving device 20 of the display panel according to the present invention is driven by the driving method shown in FIGS. 3 and 4.

The image processor 21 converts an external analog image signal into a digital signal, and thus internal image signals, for example, 8-bit red (R), green (G), and blue (B) image data, clock signals, vertical and horizontal, respectively. Generate sync signals. The logic controller 22 generates driving control signals S _A , S _Y , and S _X according to an internal image signal from the image processor 21.

In this case, the driving unit such as the address driver 23, the X driver 24, and the Y driver 25 receives input from the driving control signals S _A , S _Y , and S _X , and generates respective driving signals. The applied driving signal to each of the electrode lines.

That is, the address driver 23 processes the address signal S _A among the drive control signals S _A , S _Y , and S _X from the logic controller 22 to generate a display data signal, and generates the displayed display. The data signal is applied to the address electrode lines. The X driver 24 processes the X driving control signal S _X from the driving control signals S _A , S _Y , and S _X from the logic controller 22 and applies the X driving control signal S _X to the X electrode lines. The Y driver 25 processes the Y driving control signal S _Y among the driving control signals S _A , S _Y , and S _X from the logic controller 22 and applies the Y driving control signal S _Y to the Y electrode lines.

The load factor calculator 26 calculates the load factor. The load rate may be defined as a ratio of discharge cells that cause display discharges among all discharge cells. At this time, the load ratio is preferably calculated from the video signal from the logic controller 22.

The load ratio is calculated for each address electrode line by calculating the line load ratio obtained by the ratio of the discharge cells causing the address discharge among all the discharge cells, and calculating the arithmetic mean of the line load ratios for all the address electrode lines. Can be obtained from the load factor. However, in the present embodiment, the load ratio is preferably calculated in units of subfields SF in FIG. 3.

In the inclination controller 27, the inclination of the data signal is changed according to the load ratio. In other words, when the load ratio is large, the slope is adjusted small, and when the load ratio is small, the slope is large.

The load factor calculated by the load factor calculator 26 is preferably a line load factor calculated in units of address electrodes. At this time, the tilt adjusting unit 27 adjusts the tilt of each address electrode.

In addition, a data signal rising from the first level V _G to the second level V _A is applied to the address electrode in the address period (PA in FIG. 4). At this time, the tilt adjusting unit 27 adjusts the rising slope rising from the first level (V _G ) to the second level (V _A ) according to the load ratio.

In the inclination controller 27, the rising inclination of the data signal is changed according to the line load ratio. In other words, when the line load ratio is large, the rising slope is adjusted small, and when the line loading ratio is small, the rising slope is large.

Typically, the slope of the data signal applied to the address period is determined by the time constant by the product of the resistance and the capacitance. At this time, the capacitance varies depending on the load factor. In addition, the capacitance is proportional to the dielectric constant and the width of the electrode forming the capacitor, and inversely proportional to the distance between the electrodes forming the capacitor.

Here, the dielectric constant and the distance between the electrodes are constant, and the area for forming the capacitor depends on the number of discharge cells causing the address discharge. That is, in a discharge cell that causes an address discharge, a short state occurs between the electrodes, so that no capacitance is formed between the electrodes. Therefore, when the number of discharge cells causing the address discharge is large, that is, when the load ratio is large, the capacitance is small, and when the load ratio is small, the capacitance is large.

Therefore, the larger the load ratio, the smaller the capacitance, the smaller the time constant, and accordingly, the rising slope increases. In addition, as the load ratio decreases, the capacitance increases, so that the time constant increases, and accordingly the rising slope decreases. Therefore, in the present invention, when the load ratio, preferably the line load ratio becomes large, the rising slope of the address data signal is adjusted small.

Accordingly, in the present invention, even if the load ratio is large, the rising slope becomes large due to the characteristics of the panel, and thus a sudden current change occurs, thereby increasing the amount of EMI radiation.

3 is a timing diagram illustrating a driving method of driving a unit frame composed of a plurality of sub-fields in the method of driving a plasma display panel according to the present invention.

Referring to the drawing, the unit frame FR is divided into eight subfields SF1 to SF8 to realize time division gray scale display. Each subfield SF1 to SF8 is divided into reset periods R1 to R8, address periods A1 to A8, and sustain discharge periods S1 to S8.

The luminance of the plasma display panel is proportional to the length of the sustain discharge periods S1 to S8 occupied in the unit frame. The length of the sustain discharge cycles S1 to S8 occupied in the unit frame is 255T (T is the unit time). At this time, a time corresponding to 2 ⁿ is set in the sustain discharge period Sn of the nth subfield SFn. Accordingly, if the subfield to be displayed among the eight subfields is appropriately selected, 256 gray levels may be displayed including all zero (zero) grays not displayed in any of the subfields.

In the present invention, it is preferable that the load ratio is calculated in subfield units.

4 is a timing diagram illustrating an embodiment of driving signals applied to respective electrode lines with respect to one subfield according to an exemplary embodiment of the present invention.

In the drawings, reference numeral S _AR1..ABm denotes a driving signal applied to each address electrode line (A _R1 to A _Bm of FIG. 1), and S _X1..Xn denotes X electrode lines (X ₁ to X _n of FIG. 1). ), And S _Y1 to S _Yn indicate a drive signal applied to each Y electrode line (Y ₁ to Y _{n in} FIG. 1).

Referring to the drawing, in the reset period PR of the unit subfield SF, first, the voltage applied to the X electrode lines X ₁ to X _n is converted from the ground voltage V _G to the second voltage V _S. For example, it continuously rises to 155 volts (V). Here, the ground voltage V _G is applied to the Y electrode lines Y ₁ to Y _n and the address electrode lines A _R1 to A _Bm . Accordingly, between the X electrode lines X ₁ to X _n and the Y electrode lines Y ₁ to Y _n , and the X electrode lines X ₁ to X _n and the address electrode lines A ₁ to A _A weak discharge occurs between _m ) and negative wall charges are formed around the X electrode lines X ₁ to X _n .

The Next, Y electrode lines (Y ₁ ~ Y _n) voltage to the second voltage applied to the (V _S), for example, the third voltage (V _SET than the second voltage (V _S) from 155 volt (V) The maximum voltage (V _SET + V _S ), which is as high as), continues to rise to, for example, 355 volts (V). Here, the ground voltage V _G is applied to the X electrode lines X ₁ to X _n and the address electrode lines A _R1 to A _Bm . Accordingly, a weak discharge occurs between the Y electrode lines Y ₁ to Y _n and the X electrode lines X ₁ to X _n , while the Y electrode lines Y ₁ to Y _n and the address electrode lines are formed. Weak discharge occurs between (A _R1 and A _Bm ).

Next, while the voltage applied to the X electrode lines X ₁ to X _n is maintained at the second voltage V _S , the voltage applied to the Y electrode lines Y ₁ to Y _n is second. It continues to fall from voltage V _S to ground voltage V _G. Here, the ground voltage V _G is applied to the address electrode lines A _R1 to A _Bm .

In the subsequent address period PA, the scan pulse of the ground voltage V _G is applied to the Y electrode lines Y ₁ to Y _n biased to the fourth voltage V _SCAN lower than the second voltage V _S. The scan signals are sequentially applied, and the display data signal of the address voltage V _A is applied to the address electrode lines of the discharge cells to cause the display discharge.

At this time, the display data signal applied to each of the address electrode lines A _R1 to A _{Bm is} supplied with the positive address voltage V _A when the discharge cell is selected and the ground voltage V _G when the discharge cell is not selected. Accordingly, when the display data signal of the positive address voltage V _A is applied while the scan pulse of the ground voltage V _G is applied, wall charges are formed by the address discharge in the corresponding discharge cell. Wall charges do not form. In addition, the second voltage V _S is applied to the X electrode lines X ₁ to X _{n for} more accurate and efficient address discharge.

In this way, after the wall charge state suitable for the address discharge is formed for all the discharge cells in the reset period PR, in the direction from one end of the panel to the other end, that is, the Y electrode at the other end from one end of the Y electrode Y ₁ . (Y _n ), the scan pulses are sequentially applied in the order of Y ₁ , Y ₂ , ..., Y _n , and to the Y electrodes Y ₁ , ..., Y _{n to} which each scan pulse is applied. for the address electrodes that form discharge cells to be displayed it is the address voltage is applied through the _{(a 1, ..., a m} ).

In the sustain discharge period PS, the display sustain pulse of the second voltage V _S is alternately applied to all the Y electrode lines Y ₁ to Y _n and the X electrode lines X ₁ to X _n . In the corresponding address period PA, a discharge for maintaining the display occurs in discharge cells in which wall charges are formed.

The driving method of the display panel according to the present invention includes a load factor calculation step and a tilt adjustment step. In the load factor calculation step, the load factor, which is the ratio of the discharge cells causing the display discharge among the discharge cells, is calculated. In addition, in the inclination adjustment step, the inclination to which the data signal is applied is changed according to the load ratio.

The load ratio is calculated for each address electrode line by calculating the line load ratio obtained by the ratio of the discharge cells causing the address discharge among all the discharge cells, and calculating the arithmetic mean of the line load ratios for all the address electrode lines. Can be obtained from the average load factor. However, in the present embodiment, the load ratio is preferably calculated in units of subfields SF in FIG. 3.

In the inclination adjustment step, the inclination to which the data signal is applied is changed according to the load ratio. In other words, when the load ratio is large, the slope is adjusted small, and when the load ratio is small, the slope is large.

The load factor calculated in the load factor calculation step is preferably a line load factor calculated for each address electrode. At this time, the inclination adjustment step is adjusted the inclination for each address electrode.

In addition, a data signal rising from the first level V _G to the second level V _A is applied to the address electrode in the address period (PA in FIG. 4). At this time, in the inclination adjustment step, the rising inclination rising from the first level V _G to the second level V _A is adjusted according to the load ratio.

In the slope adjustment step, the rising slope to which the data signal is applied is changed according to the line load ratio. In other words, when the line load ratio is large, the rising slope is adjusted small, and when the line loading ratio is small, the rising slope is large.

As the load factor increases, the capacitance decreases, resulting in a small time constant, and thus a rising slope. In addition, as the load ratio decreases, the capacitance increases, so that the time constant increases, and accordingly the rising slope decreases. Therefore, in the present invention, when the load ratio, preferably the line load ratio becomes large, the rising slope of the address data signal is adjusted small.

Accordingly, in the present invention, even if the load ratio is large, the rising slope becomes large due to the characteristics of the panel, and thus a sudden current change occurs, thereby increasing the amount of EMI radiation.

According to the driving method of the display panel and the driving apparatus thereof according to the present invention, the amount of EMI radiation can be reduced by adjusting the rising slope of the address voltage according to the load ratio.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, it is merely an example, and those skilled in the art may realize various modifications and equivalent other embodiments therefrom. I can understand. Accordingly, the true scope of protection of the invention should be defined only by the appended claims.

Claims (10)

For the display panel in which the discharge cells are formed by the X electrode and the Y electrode and the address electrode, there are a plurality of sub-fields according to respective gray weights for time division gray scale display for each frame as the display period, and the respective sub- There is a reset period, an address period, and a sustain discharge period for each field, In the address period, a scan signal is sequentially applied to the Y electrodes, and a data signal rising from a first level to a second level is applied to the address electrodes of discharge cells to be displayed among the discharge cells. Select and drive the discharge cells to display, A load factor calculation step of calculating a load factor which is a ratio of discharge cells causing display discharge among the discharge cells; And And a tilt adjusting step of adjusting a rising slope rising from the first level to the second level according to the load ratio. The method of claim 1, In the inclination adjustment step, when the load ratio is increased, the rising inclination is adjusted small, and when the load ratio is small, the driving method of the display panel. The method of claim 1, And in the load factor calculation step, the load factor is calculated in subfield units. The method of claim 1, And in the load factor calculation step, the load factor is calculated for each address electrode. The method of claim 4, wherein And adjusting the rising slope of each of the address electrodes in the tilt adjusting step. For the display panel in which the discharge cells are formed by the X electrode and the Y electrode and the address electrode, there are a plurality of sub-fields according to respective gray weights for time division gray scale display for each frame as the display period, and the respective sub- There is a reset period, an address period, and a sustain discharge period for each field, and in the address period, a scan signal is sequentially applied to the Y electrodes, and among the discharge cells, the address electrode of the discharge cell to be displayed. A data signal rising from the first level to the second level is applied to select and drive the discharge cells to be displayed. A load factor calculation unit for calculating a load factor which is a ratio of discharge cells causing display discharge among the discharge cells; And And a tilt controller configured to adjust a rising slope rising from the first level to the second level according to the load ratio. The method of claim 6, In the inclination control unit, a driving device of a display panel to adjust the rising inclination is small when the load ratio is large, and to increase the rising inclination when the load ratio is small. The method of claim 6, And the load ratio calculator is configured to calculate the load ratio in subfield units. The method of claim 6, And the load factor is calculated in units of address electrodes in the load factor calculator. The method of claim 9, And the rising slope of each of the address electrodes is adjusted by the tilt adjusting part.

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