KR20070027791A - Pdp device and its control method for the same - Google Patents

Abstract

A plasma display panel device and a method for driving the same are provided to compensate the brightness difference for the previous frame by increasing the number of sustain pulses in a process for changing an image pattern. A driving device of a plasma display panel includes a sustain pulse number controller(150). The sustain pulse number controller drives discharge cells by increasing the number of sustain pulses at a constant ratio when the change of a screen load exceeds a reference value. A load decision unit(160) decides a load change between the previous frame and the present frame and generates a control signal to the sustain pulse number controller in order to increase the number of sustain pulses during a predetermined time according to the decision result.

Description

Plasma display device and its driving method {PDP device and its control method for the same}

1 is a partial perspective view of an AC plasma display panel;

2 is an arrangement diagram of electrodes of a plasma display panel;

3 is a driving waveform of a conventional plasma display panel,

4 is a block diagram showing the configuration of the plasma display device of the present invention;

5 is a graph showing the relationship between the number of sustain pulses compared to the APL of the present invention;

6 is a graph showing the relationship between the number of sustain pulses versus time of the plasma display device of the present invention;

7 is a flowchart illustrating a method of driving a plasma display device of the present invention.

<Explanation of symbols on main parts of the drawings>

110: reverse gamma correction unit 120: error diffusion unit

130: subfield mapping unit 140: APL calculation unit

150: sustain pulse number adjusting unit 200: address driver

300: sustain drive unit

The present invention relates to an apparatus and method for driving a plasma display panel (PDP). More particularly, the present invention relates to a plasma display panel in which afterimages are improved by changing the number of sustain pulses according to load changes and gray scale expression is improved. A drive system and method are disclosed.

Recently developed flat panel displays include liquid crystal displays (LCDs), field emission displays (FEDs), PDPs, and the like. Among them, PDPs are in the spotlight as large display devices because they have higher luminance and luminous efficiency and wider viewing angles than other flat panel display devices.

The PDP is a flat display device that displays characters or images by using plasma generated by gas discharge, and tens to millions or more pixels are arranged in a matrix form according to their size. Such PDPs are classified into a direct current type (DC type) and an alternating current type (AC type) according to the shape of the driving voltage waveform applied and the structure of the discharge cell.

1 is a partial perspective view of an AC plasma display panel, and FIG. 2 shows an electrode arrangement diagram of the plasma display panel.

As shown in FIG. 1, the scan electrode 4 and the sustain electrode 6 covered with the dielectric layer 2 and the protective film 3 are arranged in parallel in the first substrate 1. At this time, the direction of the scan electrode and the sustain electrode is the horizontal direction on the screen.

The scan electrode 4 and the sustain electrode 6 are each formed of a transparent electrode and a metal electrode, the dielectric layer 2 is formed of low melting glass, and a protective film 3 made of MgO is formed on the surface of the dielectric layer.

The plurality of address electrodes 8 covered with the insulator layer 7 are provided on the second substrate 6. The partition wall 9 is formed on the insulator layer 7 between the address electrodes 8 in parallel with the address electrode 8, and the phosphor 10 is formed on the surface of the insulator layer 7 and on both sides of the partition wall 9. ) Is formed.

In this case, the first substrate 1 and the second substrate 6 are disposed to face each other with the discharge space 11 therebetween so that the scan / sustain electrodes 4 and 5 and the address electrode 8 are perpendicular to each other. The discharge space at the intersection of the scan electrode and the sustain electrode paired with the address electrode forms one discharge cell (P).

The discharge space 11 is filled with a discharge gas in which xenon is mixed with neon as a main component, and the phosphors 10 of R, G and B are excited by ultraviolet rays emitted by xenon during discharge and emit light.

That is, as shown in FIG. 2, the electrodes are arranged in a matrix configuration, and the scan electrodes 4 and the sustain electrodes 5 are alternately arranged in the horizontal direction of the screen to be displayed, and the address electrodes 8 in the vertical direction. ) Is arranged.

In addition, one discharge cell constitutes a sub-pixel as emitting light of one color, and three sub-pixels SP_R, G, and B representing R, G, and B each display one pixel (P). To achieve.

In the plasma display apparatus having such a discharge cell structure, a discharge cell is selected by applying a voltage between the scan electrode 4 and the address electrode 8 to generate an address discharge, and the scan electrode 4 and the sustain electrode 5 are selected. Sustain pulses are alternately applied between each other to generate sustain discharge, thereby causing light emission.

3 illustrates a driving waveform of a conventional plasma display panel, and looks at the problems of the conventional PDP driving method.

The driving pulses shown in FIG. 3 illustrate pulses applied to each electrode in the seventh subfield, and the address electrode is represented by the X electrode, the scan electrode is represented by the Y electrode, and the sustain electrode is represented by the Z electrode.

In addition, one frame FF is divided into a plurality of field groups F, and each field is further divided into a plurality of subfields SF. Each subfield F is composed of a reset section R, an address section A, and a sustain section S again.

First, the reset section R is a section for erasing the wall charge state formed by the previous sustain discharge and initializing the state of each cell, and the address section A is a section for selecting a cell to be discharged.

The sustain section S is a section in which discharge is actually performed to display an image in a selected cell. When the sustain section S becomes a sustain section, sustain pulses are alternately applied to the scan electrode 4 and the sustain electrode 5 to perform sustain discharge. Is displayed.

In this case, in order to display 256 gray scales, the sustain period for implementing gray scales according to the number of discharges is different for each subfield SF so that each subfield can express the gray scale of the image. Is displayed.

In addition, in the conventional driving method, the number of discharges in one frame is determined according to an average pixel level (hereinafter referred to as APL). The following equation is used.

[Equation]

 Constant power (W) = discharge count * APL * constant

First, an average luminance, that is, an APL value, is detected in units of frames with respect to an input image signal, and the number of discharges corresponding to the detected APL value, that is, the number of sustain pulses, is calculated based on the above equation.

For example, at the lowest APL value, the number of sustain pulses is maximized to increase the display brightness, thereby increasing the contrast ratio of a dark image, and when a bright image such as full white is input and the maximum APL value is detected, the number of sustain pulses is minimized. To display the image while keeping the power consumption constant.

At this time, if the image having the lowest APL value (the image with a small load) is maintained for a predetermined time or more, and then switched to a full white image (the image with a large load), the phosphor deterioration and ion damage of the discharge cell which are turned on to display the previous frame are shown. In addition, the electrical characteristics or temperature characteristics are changed by impurities, and thus, the recovery capability is lowered and luminance deviation is generated. As a result, afterimages of the previous image frame are displayed, thereby degrading image quality.

As such, an afterimage resulting from a sudden increase in load is referred to as a bright afterimage, in addition to a dark afterimage, complementary afterimage, boundary afterimage, and the like.

The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to increase the number of sustain pulses set for a predetermined time by a predetermined ratio and then to the set number again when displaying an image of a rapidly increasing load. According to the present invention, a plasma display device and a driving method thereof capable of compensating for a difference in luminance according to a pattern change to improve afterimages are provided.

In addition, the present invention is to provide a plasma display device and a method of driving the same which can be reset brightness by increasing the number of sustain pulses to increase the brightness of the display image when the load is high.

Plasma display device according to the present invention for solving the above problems is characterized in that it comprises a control unit for driving the discharge cell by increasing the sustain pulse by a certain ratio, if the screen load change exceeds the reference value.

In addition, the driving method of the plasma display apparatus according to the present invention is characterized in that it comprises the step of determining the screen load change, and if the screen load change exceeds the reference value, increasing the sustain pulse by a certain ratio.

In this case, when the difference between the number of sustain pulses set according to the APL (Average Power Level) of the previous frame and the current frame exceeds 800, it is determined that the screen load change exceeds the reference value.

In the second embodiment, when the difference between the on-cell ratio of the previous frame and the current frame is 90%, it is determined that the screen load change exceeds the reference value.

If it is determined that the screen load change exceeds the reference value, the sustain pulse is increased by 5% to 20% over the number of sustain pulses set according to the APL of the current frame.

In addition, the present invention further includes the step of maintaining the increased sustain pulse for a predetermined time and decreasing the number of sustain pulses set according to the APL of the current frame.

The predetermined time is preferably within 1 minute, and the number of the sustain pulses may be exponentially reduced, cascaded or linearly reduced.

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

4 is a block diagram showing the configuration of the plasma display device of the present invention, with reference to this will be described in detail the configuration of the present invention.

The plasma display apparatus of the present invention includes a control unit 100, an address driver 200, and a sustain driver 300. The control unit 100 includes an inverse gamma adjusting unit 110, an error diffusion unit 120, and a subfield mapping. The unit 130 outputs a signal for driving an address.

In addition, the control unit 100 determines the load change of the current frame compared to the previous frame, the APL calculator 140, the sustain pulse number adjusting unit 150 connected to the error diffusion unit 120, and a load for applying a control signal. The determination unit 160 outputs a signal for driving sustain.

The inverse gamma correction unit 110 maps an n-bit digital video signal RGB from an input line to an inverse gamma curve and corrects the m-bit (m≥n) video signal, thereby correcting the gray level value of the video signal. Linearly convert the luminance

To this end, the inverse gamma correction unit 110 performs logic 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. Circuitry (not shown).

At this time, since the video signal input to the inverse gamma correction unit 110 is a digital signal, when an analog video signal is input, an analog-to-digital converter (A / D converter, not shown) for converting the analog signal into a digital signal is located at the front end. Can be connected.

In addition, a gain adjusting unit (not shown) for adjusting the gain of the inverse gamma corrected digital image signal RGB by an effective gain may be connected to the rear end of the inverse gamma correcting unit 110.

The error diffusion unit 120 finely adjusts the luminance value by diffusing the corrected quantization error of the digital image signal RGB to adjacent cells.

The subfield mapping unit 130 maps the data input from the error diffusion unit 120 to a prestored subfield pattern and supplies the mapping data to the address driver 200.

In the present exemplary embodiment, eight subfields are used to express the gray level of 256 levels, and the number of subfields constituting one frame is different according to the gray level.

The address driver 200 selects a discharge cell to be displayed by applying a digital image signal input from the subfield mapping unit 130 to each address electrode X1-Xm according to an address driving control signal.

The APL calculator 140 detects a load factor (load) using the digital image signal RGB output from the error diffusion unit 120, and detects an average luminance, that is, APL, in units of frames according to the detected load factor. .

In addition, the sustain pulse number Nsus corresponding to the detected APL is read from the memory and output to the sustain pulse number adjusting unit 150 described later. At this time, the sustain pulse number information (Nsus) corresponding to the APL curve shown in FIG. 5 is stored in a look-up table (LUT) in the memory, and determined by the APL calculator 140. The number of sustain pulses to be referred to as "setting sustain pulses" for convenience.

On the other hand, the load determination unit 160 of the present invention determines the load change between the previous frame and the current frame. In more detail, the load determination unit 160 detects an input of a video signal in which load is increased rapidly compared to a previous frame.

To this end, the load determination unit 160 compares the difference between the number of sustain pulses set according to the APL values of the current frame and the previous frame and a reference value, and determines that the load has surged in the image signal of the current frame when the reference value is exceeded. . At this time, the reference value is an example of 800, a value that can be changed by the designer.

In addition, the load determination unit 160 may compare the difference between the on-cell ratio of the current frame and the previous frame and a reference value, and determine that the load has surged in the image signal of the current frame when the reference value is exceeded. . At this time, the reference value exemplifies 90%, and is a value changeable by the designer.

If the load determination unit 160 determines that the load of the video signal of the current frame has rapidly increased, the control signal is applied to the sustain pulse number adjusting unit 150.

The sustain pulse number adjusting unit 150 receiving the control signal from the load determining unit 160 sets the [number of sustain pulses] Nsus determined by the APL calculation unit 140 for a predetermined ratio T for a predetermined time T. By increasing the number of pulses to control, and outputs them to the sustain driver (300).

Of course, when the load of the video signal of the current frame is not changed compared to the previous frame, the set sustain pulse number determined by the APL calculator 140 is output to the sustain driver 300 as it is.

In this case, it is preferable that the predetermined ratio at which the number of sustain pulses is increased is 5% to 20% of the number Nsus of sustain pulses according to the APL of the current frame.

In addition, it is preferable that the period T in which the sustain pulse number is increased is within an initial 1 minute, and is reduced to [the set sustain pulse number, Nsus] by the APL calculator 140 during a subsequent time. This is shown in Figure 6a.

However, the sustain pulse number Nsus' adjusted by the sustain pulse number adjusting unit 150 may be exponentially reduced as shown in FIG. 6B, or may be reduced stepwise as shown in FIG. 6C. , May be linearly reduced as shown in FIG. 6D.

In addition, as shown in FIG. 6E, the increase-decrease may be repeated at predetermined intervals within one frame, and likewise, the decrease in the number of pulses may be in the form of any one of FIGS. 6A to 6D.

That is, the sustain pulse number adjusting unit 150 adjusts the number of sustain pulses according to the load change during each sustain period of the subfield entering one frame and outputs the number of sustain pulses to the sustain driver 300.

Accordingly, when an image frame in which load is increased compared to the previous frame is input, the number of sustain pulses is increased during the initial predetermined time when the frame is switched, so that the luminance is increased and the afterimage of the previous frame is improved.

 The sustain driver 300 generates a timing control signal in response to [set sustain pulse number] Nsus or [adjusted sustain pulse number] Nsus' output from the sustain pulse number adjuster 150. The timing control signal is alternately applied to the scan electrodes Y1-Yn and the sustain electrodes Z1-Zn to cause discharge to the selected discharge cells.

In this case, although the sustain pulse number adjusting unit 150 and the load determining unit 160 have been described separately, the two may be simultaneously implemented in one block.

Looking at the driving method of the plasma display device of the present invention configured as described above with reference to FIG.

First, when an image is input, the APL calculator detects an APL value for the image and calculates the number of sustain pulses corresponding to the APL value. This is called [set sustain pulse number]. (S1 to S3)

The load determination unit determines the load change of the current frame compared to the previous frame. When the difference in the number of sustain pulses from the previous frame exceeds the reference value, the load determination unit determines that the load has surged in the video signal of the current frame. At this time, the reference value illustrates that 800.

As another determination method, when the difference between the on-cell ratio of the current frame and the previous frame exceeds the reference value, it is determined that the load is rapidly increased in the video signal of the current frame. In this case, the reference value exemplifies that it is 90% (S4).

When it is determined that the load is suddenly increased (increasing the APL value) of the video signal of the current frame, the control signal is applied to the sustain pulse number adjusting unit.

According to the control signal, the sustain pulse number adjusting unit increases the [set sustain pulse number] determined by the APL calculation unit by a predetermined ratio for a predetermined time as shown in FIGS. 6A, B, C, D, and E. FIG. Then, the number of pulses is adjusted by decreasing it again (S5).

When the control signal is not applied by the load determination unit, the number of sustain pulses is not adjusted and a drive pulse having [the set number of sustain pulses] is applied.

That is, the sustain driver applies the sustain pulse to the scan electrode and the sustain electrode in response to the [set sustain pulse number] or the [adjusted sustain pulse number] output from the sustain pulse number adjuster. (S6)

As described above, the plasma display device and the driving method thereof according to the present invention have been described with reference to the illustrated drawings. It is possible to apply within the scope of protection of the technical idea of the present invention by those skilled in the art.

The plasma display device and the driving method thereof according to the present invention configured as described above can improve the image quality by compensating for the luminance difference from the previous frame by increasing the number of sustain pulses when switching the image pattern in which the load increases rapidly. You can.

In addition, since the luminance of the display image is uniformly distributed during the increase in the number of sustain pulses, the effect of the luminance reset can be expected.

Claims (15)

Determining the screen load change, And if the screen load change exceeds a reference value, increasing the number of sustain pulses by a predetermined ratio. In claim 1, The reference value is a plasma display driving method, characterized in that the difference between the number of the sustain pulse according to the APL (Average Power Level) of the previous frame and the current frame is 800. In claim 1, The reference value is a plasma display driving method, characterized in that the difference between the on-cell ratio of the previous frame and the current frame (90%). In claim 1, And a predetermined ratio at which the sustain pulse is increased is 5% to 20% of the number of sustain pulses according to the APL of the current frame. In claim 1, The increased sustain pulse is maintained for a predetermined time; And reducing the sustain pulse to the number of sustain pulses according to the APL of the current frame. In claim 5, And said predetermined time is within 1 minute. In claim 5, And the number of sustain pulses is exponentially reduced. In claim 5, And the number of the sustain pulses is reduced stepwise. In claim 5, And the number of the sustain pulses is linearly reduced. And a sustain pulse number adjusting unit for driving the discharge cells by increasing the number of sustain pulses by a predetermined ratio when the screen load change exceeds the reference value. In claim 10, And determining a load change between a previous frame and a current frame and issuing a control signal to the sustain pulse number adjusting unit so as to increase the number of sustain pulses during a predetermined period of initial frame switching according to a determination result. Plasma display driving device characterized in that. In claim 11, The load determination unit compares the difference between the number of sustain pulses set according to the APL values of the current frame and the previous frame and the first reference value, and issues the control signal when the first reference value is exceeded. . In claim 12, And said first reference value is 800. In claim 11, And the load determination unit compares a difference between an on-cell ratio between a current frame and a previous frame and a second reference value and issues the control signal when the second reference value is exceeded. In claim 14, And said second reference value is 90%.

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