KR100529074B1 - Plasma display device and driving method thereof - Google Patents

Abstract

The present invention calculates a screen load ratio for an input image signal and maintains gray linearity for each load by having different subfield weight arrays for each APC level determined according to the load ratio, thereby improving gray scale expression and reducing color bands. The present invention provides a plasma display device and a driving method thereof.

Description

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

The present invention relates to a plasma display device and a driving method thereof, and more particularly, to a plasma display device having a different subfield weight corresponding to an APC level and a driving method thereof.

Plasma display devices are flat display devices that display characters or images using plasma generated by gas discharge, and dozens to millions or more of pixels are arranged in a matrix form according to their size.

In general, the driving method of the plasma display device includes a reset period, an addressing period, and a sustain period.

The reset period is a period of initializing the state of each cell in order to perform an addressing operation smoothly on the cell. The addressing period is an address voltage for a cell (addressed cell) turned on to select a cell that is turned on and a cell that is not turned on in a panel. It is a period of time to perform the operation of accumulating wall charge by applying a. The sustain period is a period in which a discharge for actually displaying an image in the addressed cells by applying a sustain discharge pulse is performed.

Meanwhile, in the plasma display device, one frame (1TV field) is divided into a plurality of subfields, and time division control is performed to implement gray scale. Each subfield consists of the reset period, address period, and sustain period described above.

In the plasma display device, power consumption is high due to its driving characteristics, and thus, automatic power control (hereinafter referred to as APC) that controls power consumption according to the load ratio or average signal level of a frame to be displayed. The technique is used. The APC method is a method of varying the APC level according to the load ratio of input image data, and limiting the power consumption to a predetermined level or less while varying the number of sustain discharge pulses for each APC level.

According to this APC technique, the number of sustain discharge pulses applied to each subfield changes according to the load ratio. In general, in a plasma display device in which one frame is divided into a plurality of subfields, the total number of sustain discharge pulses applied to one frame is determined according to the load ratio, and each subfield corresponds to the luminance weight of the subfield. Has the number of sustain discharge pulses.

1 is a diagram showing the number of sustain discharge pulses allocated to each subfield according to a conventional fixed subfield weight arrangement.

As shown in FIG. 1, for example, when one frame is divided into eight subfields to implement 256 gray levels, each subfield SF1 to SF8 weight array corresponds to all APC levels (0 to 255). It has an array of field weights. At this time, for example, in order to implement a gray scale of 3, the discharge cell is discharged in the subfield SF1 having the 1T light emission period and the subfield SF2 having the 2T light emission period so that the sum of the discharge periods is 3T. In this manner, 256 grayscale images are displayed by combining subfields having different light emission periods.

However, when the same subfield weight is applied regardless of the APC level as in the related art, the number of sustain discharge pulses allocated for each APC level has a great influence on the gradation representation. Specifically, in the case of any N gray level, when the number of sustain discharge pulses allocated for each APC level is 2 ^N or less, gray linearity is not maintained and gray level distortion and color bands are caused. In addition, even if the number of sustain discharge pulses is 2 ^N or more, the low gradation linearity and gray scale expression are distorted depending on the number of sustain discharge pulses allocated to each subfield in response to the load ratio unless the number of sustain discharge pulses is a multiple of N. This happens.

Accordingly, the present invention is to solve the above-described problems of the prior art, and by using different subfield weighting arrangements for each APC level, it is possible to maintain the gray scale linearity for each load, thereby improving the gray scale expression and reducing the color band. An apparatus and a driving method thereof are provided.

A driving method of a plasma display device according to an aspect of the present invention for achieving the above object is

A driving method of a plasma display device which drives one frame by dividing a plurality of subfields to represent a gray level of an input image signal.

(a) measuring a screen load ratio for an input video signal;

(b) selecting a subfield weight arrangement corresponding to the screen load ratio measured in step (a) from among a plurality of subfield weight arrangements set differently according to the screen load ratio;

(c) calculating the number of sustain discharge pulses allocated to each subfield using the subfield weight array selected in step (b); And

(d) driving the plasma display device corresponding to the number of sustain discharge pulses calculated in step (c).

In this case, the subfield weight arrangement may be different for each APC level determined according to the load ratio.

Plasma display device according to another aspect of the present invention

A plasma panel having a plurality of address electrodes arranged in a column direction and a plurality of scan electrodes and sustain electrodes arranged in a row direction;

A control unit for calculating the number of sustain discharge pulses allocated to each subfield by using different subfield weighting arrangements according to the load ratio of the image signal input from the outside, and generating and outputting a control signal accordingly;

An address driver which receives the control signal from the controller and applies a display data signal to the address electrode to select a discharge cell to be displayed;

A sustain driver which receives the control signal from the controller and drives the sustain electrode; And

And a scan driver configured to receive the control signal from the controller and drive the scan electrode.

In particular, the control unit includes an automatic power control unit for calculating a screen load ratio for the input image signal;

A subfield weight storage unit for storing at least one subfield weight array set differently according to the APC level determined by the automatic power controller in response to the screen load ratio;

A sustain pulse number generator for calculating and outputting a sustain discharge pulse number of each subfield according to an array of subfield weights corresponding to the APC level determined by the automatic power controller;

A scan / maintenance driving controller configured to generate and output a control signal corresponding to the number of sustain pulses of each subfield; And

And a memory unit for rearranging and outputting subfield data generated by using the subfield weight array corresponding to the APC level into address data.

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. Like parts are designated by like reference numerals throughout the specification.

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

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

As shown in Fig. 2, the electrode of the plasma display device has a matrix structure of n_m. In the column direction, address electrodes A ₁ -A _m are arranged, and in the row direction, n rows of scan electrodes Y ₁ -Y _n and sustain electrodes X ₁ -X _n are arranged in pairs.

In the method of driving the plasma display device, each subfield (which explains waveforms in one subfield for convenience) generally includes a reset period, an address period, a sustain period, and an erase period.

The reset period is a period for initializing the state of each cell in order to smoothly perform an addressing operation on the cell, and the address period (or scan period, write period) is a period for selecting on and off cells on the panel. The period is a period in which a sustain discharge pulse is applied to sustain discharge the selected cell in the address period, and the erase period is a period in which the sustain discharge is terminated by reducing the wall charge of the cell.

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

As shown in FIG. 3, a plasma display device according to an exemplary embodiment of the present invention includes a plasma panel 100, an address driver 200, a scan driver 300, a sustain driver 400, and a controller 500. .

The plasma panel 100 includes a plurality of address electrodes A1 to Am arranged in a column direction, scan electrodes Y1 to Yn arranged in a row direction, and sustain electrodes X1 to Xn.

The address driver 200 receives an address driving control signal SA from the controller 500 and applies a display data signal for selecting a discharge cell to be displayed to each address electrode.

The scan driver 300 and the sustain driver 400 receive the Y electrode driving signal SY and the X electrode driving signal SX from the controller 500 and apply them to the X electrode and the Y electrode, respectively.

The controller 500 receives an image signal from an external source, generates an address driving control signal SA, a Y electrode driving signal SY, and an X electrode driving signal SX to generate an address driver 200 and a scan driver 300, respectively. And to the holding driving unit 400.

According to an exemplary embodiment of the present invention, the control unit 500 changes the weight of each subfield for each APC level, and transmits the driving signal to each of the address driver 200, the scan driver 300, and the sustain driver 400. .

4 is a view showing a schematic configuration of a control unit according to an embodiment of the present invention.

As shown in FIG. 4, the control unit 500 according to the embodiment of the present invention includes an inverse gamma correction unit 510, an error diffusion unit 520, an automatic power control unit 530, a subfield weight storage unit 540, The sustain pulse number generation unit 550, the scan / sustain driving control unit 560, the memory control unit 570, and the address driver 580 are configured.

The inverse gamma correction unit 510 maps n-bit R, G, and B image input data, which are currently input image data, to an inverse gamma curve and corrects the m-bit (m ?? n) image signal. In a typical plasma display device, n is 8 and m is 10 or 12.

In this case, the video signal input to the inverse gamma correction unit 510 is a digital signal. When an analog video signal is input to the plasma display device, the analog video signal may be converted into a digital video signal by an analog-to-digital converter (not shown). There is a need. The inverse gamma correction unit 510 may be a logic circuit for generating a lookup table (not shown) or data corresponding to an inverse gamma curve that stores data corresponding to an inverse gamma curve for mapping an image signal. (Not shown).

The error diffusion unit 520 is inversely gamma corrected by the inverse gamma correction unit 510 and error-diffuses the lower m-n bit image of the expanded bit m image to surrounding pixels. Error diffusion is a method of displaying an image of a lower bit by separating an image of a lower bit to be diffused into adjacent pixels and a detailed description thereof is described in Korean Patent Laid-Open Publication No. 2002-0014766.

The automatic power control (APC) unit 530 detects a load rate using the image data output from the error diffusion unit 520 and calculates an APC level according to the detected load rate.

The sustain pulse number generator 550 selects a subfield weight array corresponding to the APC level calculated by the automatic power controller 530 from the subfield weight storage unit 540 and calculates the number of sustain discharge pulses corresponding thereto. To print.

The scan / sustain driving control unit 560 generates a control signal corresponding to the number of sustain discharge pulses (sustain pulse number) output from the sustain pulse number generating unit 540 to provide the scan driver 300 and the sustain driver 400 to each. Output

Meanwhile, the memory controller 570 uses the subfield weight array stored in the subfield weight storage unit 540 according to the image data output from the error diffusion unit 520 and the APC level calculated by the automatic power controller 530. Subfield data is generated, and the subfield data is rearranged into address data for driving the plasma display device. At this time, the memory controller 570 separates all the subfields of one frame into each subfield, stores them in the frame memory (not shown in FIG. 4) for each subfield, and stores address data for all pixels for each subfield. The data is read from the memory and transferred to the address driver 580.

Accordingly, the address driver 580 generates a control signal corresponding to the address data and outputs the control signal to the panel 100.

On the other hand, the subfield weight storage unit 540 of the control unit 500 according to an embodiment of the present invention divides the APC level into a plurality of groups and the subfield weight data having different weight arrangements corresponding to each of the groups has a lookup table. It can be stored in the form.

Accordingly, the sustain pulse number generator 550 calculates and allocates the number of sustain discharge pulses of each subfield with reference to the subfield weight data corresponding to the group corresponding to each APC level.

That is, according to an embodiment of the present invention, different subfield weight arrangements may be provided for each APC level according to the load ratio of the input video signal. This will be described below in more detail with reference to FIG. 5.

5 is a diagram illustrating subfield weight data and a sustain pulse number according to an embodiment of the present invention.

As illustrated in FIG. 5, the subfield weight storage unit 540 of the control unit 500 includes three groups (first group G1: APC) having a total of 256 levels of APC levels. 0 to APC 10, second group G2: APC 11 to APC 34, third group G3: APC 35 to APC 255), and the subfield weight array corresponding to each group (subfield weight_ 1, subfield weight_2, and subfield weight_3).

In this case, referring to FIG. 5, when the subfield weight arrays corresponding to each subfield SF1 to SF8 are examined, as the APC level increases, the weight of each subfield SF4 to SF8 decreases. In detail, when the subfield weights_2 corresponding to the second group are based on the subfield weights_1 corresponding to the first group, the weights of the respective subfields may be reduced from the subfield SF4. Similarly, when looking at the subfield weights _3 corresponding to the third group, it can be seen that the weights of the subfields are reduced from the subfield SF5 to the subfield weight_2.

Referring to FIG. 5, when the APC level calculated by the automatic power controller 530 is 30, it belongs to the second group G2 of the APC levels according to the embodiment of the present invention, and the second group G2 It can be seen that the subfield weight array corresponding to is equal to the subfield weight_2 of FIG. 5.

At this time, the number of sustain discharge pulses (APC 30: 2, 4, 8, 14, 30, 61, 122, 256) assigned to each subfield according to the subfield weight arrangement of the subfield weight_2 is shown in FIG. It can be seen that the linearity is compared with the number of sustain discharge pulses (APC 30: 1, 3, 7, 15, 31, 62, 125, 250) allocated to each subfield according to the subfield weighting arrangement according to the technique. . In detail, the linearity is increased in the number of sustain discharge pulses allocated to each subfield in response to the increase in the subfield weight arrangement according to the embodiment of the present invention.

For example, as shown in FIG. 5, when the subfield weight doubles from SF1 (1) to SF2 (2), the number of sustain discharge pulses allocated to each subfield is doubled from 2 to 4. Similarly, it can be seen that the number of sustain discharge pulses allocated to the subfield SF3 is doubled in the subfield SF2 when it is doubled from SF2 (2) to SF3 (4). In contrast, in the related art, when the subfield weight is doubled to 1, 2, and 4, the number of sustain discharge pulses allocated to each subfield increases as SF1 (1), SF2 (3), and SF3 (7). Therefore, it can be seen that the linearity is inferior.

On the other hand, the sustain pulse number generation unit 550, the number of sustain discharge pulses N (S) assigned to each subfield according to the subfield weight arrangement of the subfield weight_2 corresponding to the APC 30 in accordance with an embodiment of the present invention Calculate and output

By doing so, it is possible to reduce the low grayscale linearity and the distortion of the gray scale expression according to the number of sustain discharge pulses allocated to each subfield according to the APC level.

Here, the subfield weight array stored in the subfield weight generator 540 according to the embodiment of the present invention has been described as an example of an experimental value for maintaining the gray scale linearity for each load in the embodiment of the present invention. Is not limited thereto and may be appropriately changed by those skilled in the art.

In addition, according to an embodiment of the present invention, it is divided into three groups for each APC level, and subfield weight arrangements corresponding to each group are described as being different. However, the present invention is not limited thereto, and many more groups are provided for each APC level. It may be divided into and may have a plurality of subfield weight arrays corresponding thereto.

Although the preferred 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 invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the present invention, by having different subfield weighting arrangements for each APC level calculated according to the load ratio, gray scale linearity for each load can be maintained, and gray scale power and color band can be reduced accordingly.

1 is a diagram showing a subfield weighting arrangement of the prior art and the number of sustain pulses allocated to each subfield accordingly.

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

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

4 is a view showing a schematic configuration of a control unit according to an embodiment of the present invention.

5 is a diagram illustrating subfield weight data and a sustain pulse number according to an embodiment of the present invention.

Claims (8)

A driving method of a plasma display device which drives one frame by dividing a plurality of subfields to represent a gray level of an input image signal. (a) measuring a screen load ratio for an input video signal; (b) selecting a subfield weight arrangement corresponding to the screen load ratio measured in step (a) from among a plurality of subfield weight arrangements set differently according to the screen load ratio; (c) calculating the number of sustain discharge pulses allocated to each subfield using the subfield weight array selected in step (b); And (d) driving the plasma display device corresponding to the number of sustain discharge pulses calculated in step (c); Method of driving a plasma display device comprising a. The method of claim 1, And the subfield weight arrangement is different for each APC level determined according to the load factor. The method of claim 1, And wherein each of the subfield weight arrays corresponds to at least two different APC levels. The method of claim 1, And the larger the APC level, the lower the subfield weight of the subfield weight array corresponding to the APC level. A plasma panel having a plurality of address electrodes arranged in a column direction and a plurality of scan electrodes and sustain electrodes arranged in a row direction; A control unit for calculating the number of sustain discharge pulses allocated to each subfield by using different subfield weighting arrangements according to the load ratio of the image signal input from the outside, and generating and outputting a control signal accordingly; An address driver which receives the control signal from the controller and applies a display data signal to the address electrode to select a discharge cell to be displayed; A sustain driver which receives the control signal from the controller and drives the sustain electrode; And A scan driver which receives the control signal from the controller and drives the scan electrode Plasma display device comprising a. The method of claim 5, An automatic power controller for calculating a screen load ratio for the input video signal; A subfield weight storage unit for storing at least one subfield weight array set differently according to the APC level determined by the automatic power controller in response to the screen load ratio; A sustain pulse number generator for calculating and outputting a sustain discharge pulse number of each subfield according to an array of subfield weights corresponding to the APC level determined by the automatic power controller; A scan / maintenance driving controller configured to generate and output a control signal corresponding to the number of sustain pulses of each subfield; And A memory unit for rearranging and outputting the subfield data generated by using the subfield weight array corresponding to the APC level into address data Plasma display device comprising a. The method of claim 5, And the subfield weight arrangement is different for each APC level determined according to the load factor. The method of claim 5, Wherein each of the subfield weight arrays corresponds to at least two different APC levels.