KR20080004779A - Plasma display device and driving method thereof - Google Patents

Abstract

A plasma display apparatus and a driving method thereof are provided to maintain beam shaft constant according to the illumination of a frame by distributing the idle period of a frame after the sustain period of a sub-field is terminated. A plasma display apparatus includes discharge cells(12), a controller(200), and drivers(300,400,500). The controller separates a frame into plural sub-fields having weighted values, allocates address and sustain periods in the sub-fields, and allocates idle periods after the sustain period of the sub-fields. The drivers select discharge cells to be illuminated among the discharge cells during the address period under control of the controller. The controller matches the start times of sustain periods of sub-fields having the same weighted value at respective frames.

Description

Plasma display device and driving method thereof {PLASMA DISPLAY DEVICE AND DRIVING METHOD THEREOF}

1 is a diagram illustrating a gray scale expression method of a conventional plasma display device.

2 is a schematic conceptual diagram of a plasma display device according to an exemplary embodiment of the present invention.

3 is a block diagram of the controller of FIG. 2.

4 is a flowchart illustrating a method of setting an idle period in the controller of FIG. 4.

5 is a diagram illustrating a gray scale representation method of a plasma display device according to an exemplary embodiment of the present invention.

The present invention relates to a plasma display device and a driving method thereof for reducing flicker.

The plasma display device is a flat display device that displays characters or images by using plasma generated by gas discharge. In the display panel of the plasma display device, tens to millions or more of discharge cells (hereinafter, referred to as "cells") are arranged in a matrix form according to their size.

In general, the plasma display device receives image signal data from the outside, divides one frame into a plurality of subfields having respective weights, and expresses gray scale by controlling time division. Each subfield may include a reset period, an address period, and a sustain period. The reset period is a period for initializing the state of each cell in order to perform an address operation smoothly in the cell. The address period is a period for performing an address operation for selecting a cell to be turned on among discharge cells, and the sustain period is a period for sustain discharge of the selected cell to be turned on in the address period by the number of times corresponding to the weight of the subfield to display an image. At this time, the screen load ratio to be expressed for one frame is determined from the image signal data input from the outside, and the number of times the sustain discharge is generated in the plurality of subfields is determined according to the screen load ratio.

On the other hand, since the periods assigned to each frame are the same, the pause period is placed from the end of all subfields of each frame until the next frame starts, and the plasma display device does not operate during the pause period.

1 is a diagram illustrating a gray scale expression method of a conventional plasma display device. In FIG. 1, it is assumed that each of the frames F1, F2, and F3 is composed of four subfields, and the illustration of the reset period is omitted for convenience. In addition, the screen load ratios of the frames F1, F2, and F3 are different, and accordingly, the number of sustain discharge pulses allocated to each of the frames F1, F2, and F3 is also different. In this case, each of the frames F1, F2, and F3 puts the pause periods P1, P2, and P3 after the four subfields are finished, thereby maintaining the same period allocated to each frame.

In general, the smaller the screen load ratio, the greater the number of sustain discharge pulses to be applied, and the sustain period also increases. Therefore, in the third frame F3 having the smallest screen hatching rate, the pause period P3 is shortest, and in the first frame F1 having the largest screen load rate, the pause period P1 is set longest.

On the other hand, as shown in Fig. 1, the starting point of the sustain period of the same subfield in each frame is different, the optical axis according to the light emission in the frame is varied. For example, as the time points at which the sustain period S2 of the second subfield of each frame F1, F2, F3 starts are different from each other, the time points at which the sustain period starts are different from each other and emit light for each frame. Since the viewpoint is different, flicker may occur. That is, the optical axis according to light emission in each frame is not constant, so the screen is recognized as flickering.

As described above, in the related art, by inserting a pause after all subfields of each frame are finished, there is a problem in that the optical axis of light emission changes in each frame according to the screen load ratio, thereby causing a flicker phenomenon.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the problems of the prior art, and to provide a plasma display device and a driving method thereof capable of reducing flicker.

In order to solve this problem, according to an embodiment of the present invention, a frame is divided into a plurality of subfields having respective weights, and the plurality of subfields each include an address period and a sustain period. It provides a driving method. The driving method of the plasma display apparatus may include calculating a screen load ratio of each frame from an input image signal, calculating a remaining period of the frame from the screen load ratio, and making the remaining period proportional to the weight of the subfield. And allocating the subfields as idle periods, wherein a first frame having a first screen load factor and a second frame having a second screen load factor are provided in the plurality of frames constituting the first frame and the second frame. The time points at which the sustain period of the subfields having the same weight among the subfields start are the same.

The calculating of the remaining period may include determining the total number of sustain discharge pulses allocated during the sustain period of the plurality of subfields from the screen load ratio, and the total number of sustain discharge pulses that may be allocated during the frame. Calculating the remaining period from the difference between the maximum number and the total number of sustain discharge pulses applied in the frame. Further, in the method of driving the plasma display device according to the embodiment of the present invention, the rest period is inversely proportional to the number of sustain discharge pulses in the subfield, and the viewpoint of the optical axis due to light emission in the frame is the same.

According to another embodiment of the present invention, a plurality of discharge cells and one frame are divided into a plurality of subfields having respective weights, and an address period and a sustain period are respectively assigned to the plurality of subfields. A control unit for further allocating an idle period after the sustain period of the plurality of subfields, and selecting discharge cells to emit light from among the plurality of discharge cells during the address period under the control of the control unit; And a driving unit for sustain discharge of the discharge cells to emit light by applying a sustain discharge pulse to the discharge cells. In the plasma display device, the controller controls the timings at which the sustain periods of the subfields having the same luminance weight in each frame start to coincide.

In this case, the control unit, the screen load ratio calculation unit for calculating the screen load ratio from the image signal input during the frame, the total number of sustain discharge pulses allocated during the sustain period of the plurality of sub-fields of the frame according to the screen load ratio A sustain period pulse calculating unit configured to calculate a remaining period of the frame from a difference between the maximum number of total sustain discharge pulses and the total number of sustain discharge pulses allocated during the frame, and the remaining period of the frame. And an idle period setting unit for allocating the idle periods of the respective subfields according to the weights of the plurality of divided subfields. The control unit sets the rest period of the subfield having the same weight of each frame to be inversely proportional to the number of sustain discharge pulses of the subfield, and controls the optical axis to emit light in the frame to be the same.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

A plasma display device and a driving method thereof according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

2 is a schematic diagram of a plasma display device according to an exemplary embodiment of the present invention.

As shown in FIG. 2, a plasma display device according to an exemplary embodiment of the present invention includes a plasma display panel 100, a controller 200, an address electrode driver 300, a scan electrode driver 400, and a sustain electrode driver 500. ). The plasma display panel 100 includes a plurality of address electrodes A ₁ -A _m (hereinafter referred to as “A electrodes”) extending in a column direction, and a plurality of sustain electrodes X ₁ -X _n extending in a row direction. (Hereinafter referred to as "X electrode") and a plurality of scan electrodes Y ₁ -Y _n (hereinafter referred to as "Y electrode"). The plurality of Y electrodes Y ₁ -Y _n and the X electrodes X ₁ -X _n are arranged in pairs with each other. A discharge cell is formed where the adjacent Y electrodes Y ₁ -Y _n , the X electrodes X ₁ -X _n , and the A electrodes A ₁ -A _m cross each other.

The controller 200 receives an image signal from the outside, drives one frame into a plurality of subfields having respective weights, and drives the address electrode driving control signal, the sustain electrode driving control signal, and the scan electrode driving control signal accordingly. Output The remaining period of the frame is calculated according to the screen load ratio allocated to each frame, and the remaining period calculated in this way is distributed to each subfield as an idle period.

The address electrode driver 300 receives an address electrode driving control signal from the controller 200 and applies a signal for selecting a discharge cell to be displayed to each A electrode A ₁ -A _m . The sustain electrode driver 500 receives the sustain electrode driving control signal from the controller 200 to apply a driving voltage to the X electrodes X _1- X _n , and the scan electrode driver 400 receives the scan electrode from the controller 200. The driving control signal is received and a driving voltage is applied to the Y electrodes Y ₁ -Y _n .

Next, a method of setting a rest period in each subfield by the control unit according to an embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

3 is a block diagram of the controller of FIG. 2, and FIG. 4 is a flowchart illustrating a method of setting an idle period in the controller of FIG. 3.

As illustrated in FIG. 3, the controller 200 includes a screen load ratio calculator 210, a sustain discharge pulse calculator 220, a remaining period calculator 230, and a pause period setter 240. In FIG. 3, an illustration of a part not related to the description of the calculation of the rest period is omitted in the control unit 200.

The remaining period of a frame is determined by the screen load ratio of the frame.

That is, referring to FIG. 4, the screen load ratio controller 210 calculates a screen load ratio of a corresponding frame from an image signal input for one frame (S410) and outputs an automatic power level corresponding to the screen load ratio (S420). In this case, the screen load ratio calculator 210 may calculate the screen load ratio from an average signal level ASL obtained by averaging the signal levels of the video signal for one frame as shown in Equation 1 below. That is, the screen load factor is proportional to the average signal level ASL of Equation 1.

In Equation 1, R _i , G _i and B _i represent the image signals of the red (R), green (G) and blue (B) discharge cells which are input in the i-th input in one frame, respectively, and N is input for one frame. It indicates the number of red video signals.

The sustain discharge pulse calculator 220 determines the total number of sustain discharge pulses allocated to one frame according to the automatic power control level corresponding to the screen load ratio (S430). At this time, since the sustain discharge pulse calculator 220 has many discharge cells that turn on when the screen load ratio is high, the total number of sustain discharge pulses is reduced to prevent the power consumption from increasing.

The remaining period calculating unit 230 calculates the remaining period ( frame_rest ) in one frame according to the automatic power control level corresponding to the screen load ratio as shown in Equation 2 below (S440).

frame_rest = max_sustain-total_sustain

That is, as in the period calculation unit 230 from the equation (2) remains, a period corresponding to keep the total number of discharge pulses of the time the maximum sustain pulse to the idle period (frame_rest) in a frame allocated (max_sustain) and It is calculated as the difference of the period ( total_sustain ) corresponding to the number of sustain discharge pulses allocated according to the screen load ratio of the frame.

Alternatively, as shown in Equation 3 below, the control unit 200 sets the idle discharge period ( frame_rest ) according to the total address period ( total_address ), the total reset period ( total_reset ) of the frame, and the sustain discharge allocated to the screen load ratio of the frame. It can also be calculated from the difference between the period (frame_period) corresponding to the sum and one frame of the period (total_sustain) corresponding to the number of pulses.

frame_rest = frame_period- (total_address + total_reset + total_sustain)

The remaining period calculated in this way is allocated to the plurality of subfields in which one frame is divided according to weights. That is, among the plurality of subfields, the high weight subfield has a long rest period, and the low weight subfield has a short rest period.

5 is a diagram illustrating a gray scale representation method of a plasma display device according to an exemplary embodiment of the present invention. FIG. 5 assumes that each frame is composed of four subfields, similarly to FIG. 1, and for illustration of the reset period, is omitted. In addition, the screen load ratios expressed in each frame are different, and accordingly, the number of sustain discharge pulses allocated to each frame is also different. In addition, in FIG. 1, each frame allocates a remaining period of a frame to a rest period after all subfields are finished, while FIG. 5 shows that a rest period allocated to each subfield allocates a remaining period after each subfield ends. The period allocated to each frame is kept the same.

In FIG. 5, each frame is divided into a first subfield SF1, a second subfield SF2, a third subfield SF3, and a fourth subfield SF4. Same as the order. That is, it is assumed that the screen load ratio is small in the order of the first frame F1, the second frame F2, and the third frame F3. In general, the larger the screen load ratio, the smaller the number of sustain discharge pulses assigned to the frame, and the smaller the screen load ratio, the greater the number of sustain discharge pulses assigned to the frame.

As shown in Fig. 5, each subfield includes a reset period (not shown), an address period A1-A4, a sustain period S1-S4, and a pause period P1-P4.

3 and 4, the idle period setting unit 240 allocates the remaining period of the frame to the idle period of each subfield according to the weight of the subfield. That is, since each subfield is further allocated a rest period calculated as described above in addition to including a reset period, an address period, and a sustain period, the time allotted to a subfield having the same luminance weight is the same regardless of the screen load ratio of the corresponding frame. Is set to.

That is, as shown in FIG. 5, the first subfield SF1 of the first frame F1 having the same luminance weight, the first subfield SF1 of the second frame F2 and the third frame F3 The time allocated to the first subfield SF1 is the same. Like the first subfield SF1, the second subfield SF2, the third subfield SF3, and the fourth subfield SF4 of each frame F1-F3 are the same with respect to the respective luminance weights. Time is allocated

In general, the number of sustain discharge pulses applied to sustain discharge the light emitting cells during the sustain periods S1-S4 of each subfield is proportional to the screen load ratio of the corresponding frame and the luminance weight of the subfield. That is, since the number of sustain discharge pulses to be applied during the sustain period varies depending on the screen load ratio of the frame, even when the subfields have the same luminance weight, the time for which the sustain discharge pulses are applied may vary. At this time, by appropriately distributing the rest period of a frame calculated in advance by the screen load ratio to each subfield, the same starting point (indicated by the dotted line) at the start of the sustain period of the same subfield of each frame is indicated by the dotted line. Thus, the optical axis according to the light emission is kept constant.

That is, in FIG. 5, the first frame F1 has a large screen load factor, and the number of sustain discharge pulses to be applied during the sustain periods S1-S4 of each subfield SF1-SF4 is small. The idle periods P1-P4 assigned to SF1-SF4) are relatively long. On the other hand, the second frame F2 has a lower screen load ratio than the first frame F1, so that the number of sustain discharge pulses applied during the sustain periods S1-S4 of each subfield SF1-SF4 is the first frame F1. ), The rest period P1-P4 of the second frame F2 is shorter than the rest period P1-P4 of the first frame. Therefore, when the rest periods are appropriately allocated to each subfield, sustain discharges occur at the same time points between the subfields having the same luminance weight as shown by the dotted lines.

As a result, starting points of the subfields having the same luminance weight are the same in each frame, and the time required for the reset period and the address period is constant. Therefore, if the subfields have the same luminance weight, the starting points of the sustain period are the same. As a result, the optical axis according to the light emission of the frame may be kept constant.

Accordingly, the flicker may be reduced because the optical axis according to the emission of the frame is constant regardless of the screen load ratio.

Although one frame is described and illustrated as being divided into four subfields, this is for the sake of brevity of description and drawings, and one frame may be divided into a plurality of subfields having respective weights. It may be divided into subfields.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the embodiment of the present invention, by appropriately distributing the rest period of the frame after the end of the sustain period of each subfield, the time allocated to the subfields having the same luminance weight regardless of the screen load ratio is fixed. The optical axis according to the light emission of the frame can be kept constant, thereby reducing flicker caused by sustain discharge.

Claims (13)

In a driving method of a plasma display device, a frame is divided into a plurality of subfields having respective weights, and each of the plurality of subfields includes an address period and a sustain period. Calculating a screen load ratio of each frame from an input video signal; Calculating a time period remaining in the frame from the screen load rate, and Allocating the remaining period as the idle period of each subfield to be proportional to the weight of the subfield; In a first frame having a first screen load ratio and a second frame having a second screen load ratio, a sustain period of a subfield having the same weight among a plurality of subfields constituting the first frame and the second frame starts. A driving method of a plasma display device having the same viewpoint. The method of claim 1, The plurality of subfields, Selecting a light emitting cell among the plurality of discharge cells during each address period; And sustain discharge of the light emitting cells by applying sustain discharge pulses of the number of times corresponding to the weights of the corresponding subfields during the sustain periods to sustain the discharge cells. The method of claim 1, And the first screen load factor and the second screen load factor are different in size from each other. The method of claim 1, Computing the remaining period of time, Determining the total number of sustain discharge pulses allocated during the sustain period of the plurality of subfields from the screen load ratio; and And calculating the remaining period from the difference between the maximum number of total sustain discharge pulses that can be allocated during the frame and the total number of sustain discharge pulses applied in the frame. The method of claim 4, wherein And the remaining period is inversely proportional to the screen load ratio of the corresponding frame. The method of claim 1, In a subfield having the same weight of each frame, And said rest period is inversely proportional to the number of sustain discharge pulses in said subfield. The method according to any one of claims 1 to 6, In the frame, the viewpoint of the optical axis according to the light emission is the same driving method of the plasma display device. A plurality of discharge cells, A frame is divided into a plurality of subfields having respective weights, an address period and a sustain period are respectively assigned to the plurality of subfields, and a rest period is further allocated after the sustain period of the plurality of subfields. Control unit, and A driving unit configured to select discharge cells to emit light among the plurality of discharge cells during the address period and to sustain discharge the discharge cells to emit light by applying a sustain discharge pulse to the plurality of discharge cells during the sustain period under the control of the controller; Including; The control unit controls the plasma display apparatus to coincide with a start point of the sustain period of the subfield having the same luminance weight in each frame. The method of claim 8, The driving unit, And a sustain discharge pulse of the number of times corresponding to the weight of the subfield corresponding to each of the sustain periods to the plurality of discharge cells. The method of claim 8, The control unit, 10. A plasma display device in which a sustain period of a subfield having the same luminance weight is started at the same time in two frames having different screen load rates. The method of claim 8, The control unit, A screen load ratio calculator for calculating a screen load ratio from an image signal input during the frame; A sustain discharge pulse calculator configured to calculate the total number of sustain discharge pulses allocated during the sustain period of the plurality of subfields of the frame according to the screen load ratio; A remaining period calculating unit for calculating a remaining period of the frame from a difference between the maximum number of the total sustain discharge pulses allocated during the frame and the number of the total sustain discharge pulses, and And an idle period setting unit for allocating the remaining periods to idle periods of each subfield according to weights of the plurality of subfields in which the frames are divided. The method of claim 8, The control unit, And a rest period of a subfield having the same weight of each frame in inverse proportion to the number of sustain discharge pulses of the subfield. The method according to any one of claims 8 to 12, The control unit controls the plasma display device so that the viewpoints of the optical axes corresponding to the light emission in the frame are the same.

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