KR20010035882A - Method of Driving Plasma Display Panel - Google Patents

Abstract

PURPOSE: A method for driving a plasma display panel is provided to improve a contrast by reducing the number of discharges for a reset period. CONSTITUTION: A reset pulse is supplied to discharge cells for a reset period once. A voltage level of the reset pulse maintains for a predetermined time and then is gradually reduced. The first sustain pulse is supplied to the discharge cells at a starting point of a sustain period once. The at least one second sustain pulse following the first sustain pulse is supplied to the discharge cells. A voltage level of the second sustain pulse is different from that of the first sustain pulse. A wall charge is produced in the discharge cells at a starting point of the sustain period. A pulse width of the first sustain pulse is greater than that of the second sustain in order to uniform amount of the wall charge produced in the discharge cells.

Description

Driving Method of Plasma Display Panel {Method of Driving Plasma Display Panel}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a plasma display panel, and more particularly, to a method for driving a plasma display panel in which the contrast of a screen is improved by reducing the number of discharges during a reset period.

A plasma display panel (hereinafter referred to as "PDP") is a display device that uses visible light generated from a phosphor when ultraviolet rays generated by gas discharge excite the phosphor. PDP is thinner and lighter than Cathode Ray Tube (CRT), which has been the mainstay of display means, and has the advantage of being able to realize high definition large screen. PDP is composed of a plurality of discharge cells arranged in a matrix form, one discharge cell constitutes a pixel of the screen. PDPs are roughly classified into a direct current (DC) method for opposing discharge in the discharge cell and an alternating current (AC) method for surface discharge according to the driving method thereof. AC type PDP has the advantages of lower power consumption and longer life than DC type.

1 is a perspective view showing a discharge cell structure of a typical AC surface discharge PDP. Referring to FIG. 1, the upper plate 20 and the lower plate 22 are provided in parallel with a predetermined distance. An AC driving signal is supplied to the rear surface of the upper substrate 24 constituting the upper plate 20 so that the scan electrode 26 and the discharge sustain electrode 27 which form sustain surface discharge are formed side by side. The scan electrode 26 and the discharge sustain electrode 27 are transparent electrodes formed transparently from indium tin oxide (ITO). The bus electrodes 30 are formed side by side on each of the scan electrodes 26 and the discharge sustain electrodes 27. Since ITO has a high resistance value, a uniform voltage is applied to each discharge cell by supplying an AC signal through the bus electrode 30. An upper dielectric layer 28 is formed on the front surface of the upper substrate on which the scan electrodes 26 and the discharge sustain electrodes 27 are formed. The upper dielectric layer 28 has a function of accumulating charges during discharge. The protective layer 31 coated on the entire upper dielectric layer 28 protects the upper dielectric layer 28 from sputtering during discharging, thereby extending the life of the pixel cell and increasing discharge efficiency of secondary electrons to improve discharge efficiency. . On the lower substrate 32 constituting the lower plate 22, a data electrode 34 for address discharge is formed to cross at right angles to the scan electrode 26 and the discharge sustain electrode 27. On the lower substrate 32 and the data electrode 34, a lower dielectric layer 36 is formed on the entire surface to form wall charges during discharge. In addition, the partition wall 42 is vertically formed between the upper plate 20 and the lower plate 22. The partition wall 42 forms the discharge space 38 of the cell together with the upper plate 20 and the lower plate 22, and separates the discharge cells from each other to block mutual interference between neighboring cells. Phosphor 40 is applied to the surfaces of the lower dielectric layer 36 and the partition 42. The discharge space 38 is filled with a mixed gas of He + Xe or Ne + Xe.

The overall structure of the electrode lines and discharge cells of the AC surface discharge PDP is as shown in FIG. Referring to FIG. 2, the discharge cells 44 are positioned at portions where the data electrode line X, the scan electrode line Y, and the discharge sustain electrode line Z cross each other.

Briefly describing the light emission process, an address discharge occurs between the scan electrode 26 and the data electrode 34 to form wall charges in the upper and lower dielectric layers 28 and 36. The formed wall charges lower the discharge voltage required for surface discharge. In the cells selected by the address discharge, a sustain discharge occurs between the two electrodes 26 and 27 by an alternating current signal alternately supplied to the scan electrode 26 and the discharge sustain electrode 27. At this time, ultraviolet rays are generated in the discharge space 38 in the process of transition after the discharge gas is excited. The generated ultraviolet rays excite the phosphor 40 to generate visible light, thereby realizing an image of the PDP.

In the AC surface discharge PDP, a gray scale of 256 gray scales representing stepwise brightness required for image display is mainly implemented by an ADS (Addressing Display Separated: hereinafter referred to as "ADS") driving method. 3 is a diagram illustrating an ADS driving method for expressing a gray level of one frame in the PDP. One frame for 16.67 ms is time-divided into eight subfields SF1 to SF8 according to the gradation. Each of the subfields SF1 to SF8 is largely divided into a reset and address period in which screen initialization and address discharge are performed, and a sustain period in which sustain discharge is performed. In each subfield, the widths of the preset reset and address periods are the same while the widths of the sustain periods are different. The sustain period is set in advance so as to increase at a rate of 2 ⁿ (n = 0,1,2,3,4,5,6,7) in each subfield according to the luminance relative ratio. In this way, the sustain period is set differently for each subfield so that the gray level of the image is expressed according to the sustain discharge period.

4 is a waveform diagram illustrating driving waveforms supplied to each electrode line of the PDP for each subfield. Referring to FIG. 4, one subfield is divided into a reset period for initializing the full screen, an address period for writing data while scanning the full screen in a sequential manner, and a sustain period for maintaining the light emission state of the cells in which the data is written. Lose. First, in the reset period, all the discharge cells are initialized by causing a discharge by a priming pulse applied to the data electrode line X and the discharge sustain electrode line Z. During priming discharge, charged particles generated in the discharge space 38 accumulate as wall charges in the upper and lower dielectric layers 28 and 36. In order to prevent the disappearance of the charged particles and the wall charges formed as described above, a discharge is generated once again by supplying a sustain pulse to the data electrode line X and the scan electrode line Y. This sustain discharge serves as an auxiliary discharge function for the previously generated priming discharge. An erase pulse is then applied to the data electrode line X and the scan electrode line Y in order to dissipate the charged particles remaining in the discharge space 38. Wall charges formed in the dielectric layers 28 and 36 during the reset period serve to lower the address discharge voltage during the address period. In the address period, scan pulses are sequentially applied to scan electrode lines Y for each scan line of the PDP, and data is supplied to each data electrode line X in synchronization with the scan pulses. At this time, a DC voltage of a predetermined level is supplied to the discharge sustaining electrode lines Z, and this DC voltage enables stable address discharge between the data electrode line X and the scan electrode line Y. In the sustain period, sustain pulses having the same pulse width and voltage are alternately applied to the scan electrode line Y and the discharge sustain electrode line Z to cause sustain surface discharge in discharge cells selected by the address discharge.

In the AC surface discharge PDP driven by this method, the reset and sustain periods are an important period in which various performances such as brightness of the screen, contrast, efficiency, and power consumption are determined. In the conventional driving method, several discharges (priming, sustaining and erasing discharges) occur during the reset period for initializing all discharge cells. That is, the entire cell is stabilized by generating, maintaining and erasing charged particles during the reset period. However, each of the plurality of discharges generated during the reset period is accompanied by micro light emission in all the discharge cells, which serves to reduce the contrast of the screen. In addition, in the conventional driving method, the voltage and pulse width of the sustain pulse supplied during the sustain period are always the same. At the beginning of the sustain period, even though the charged particles and wall charges are formed due to the sustain discharge, the amount is not large. Therefore, only after the sustain pulse is supplied for a certain period after the start of the sustain period, sufficient charged particles and wall charges are formed so that the normal sustain is maintained. You can proceed with the operation. Thus, at the beginning of the sustain period, it is necessary to supply a sufficient amount of charged particles and wall charges in a short time. In addition, during the address period, each scan line of the PDP is sequentially driven by a scan pulse supplied to the scan electrode lines (Y). During the address period, the scan pulses are sequentially supplied to the scan electrode lines Y formed in each scan line starting from the first scan line to the 480th last scan line, and then sustain discharge is generated as a whole at the same time. However, due to the address discharge, the amount of wall charges formed in each of the discharge cells is different for each scan line at the start of the sustain period. This phenomenon occurs due to the time difference between the scan of the first scan line and the scan of the last scan line. In the first scan line, since the period from the injection to the start of the sustain period is longer than that of the last scan line, the amount of wall charge disappeared is larger than that of the last scan line. As described above, since the amount of wall charges formed in each scan line is uneven at the start of the sustain period, unstable operation characteristics such as mis-discharge and mis-discharge of the cell are caused during the sustain period.

Accordingly, an object of the present invention is to provide a method of driving a plasma display panel in which the contrast of the screen is improved by reducing the number of discharges during the reset period.

Another object of the present invention is to provide a method of driving a plasma display panel to uniformize the operating characteristics of the initial sustain discharge of each discharge cell to prevent malfunction of the cells.

1 is a perspective view showing a discharge cell structure of a typical AC surface discharge plasma display panel.

2 is a layout structure of entire electrode lines and discharge cells of an AC surface discharge plasma display panel.

3 is a diagram illustrating an ADS driving method for expressing a gray level of one frame in a plasma display panel;

4 is a waveform diagram showing a conventional driving waveform supplied to each electrode line of the plasma display panel for each subfield;

FIG. 5 is a view illustrating a method of driving an AC surface discharge plasma display panel according to an exemplary embodiment of the present invention, wherein a waveform of a driving waveform supplied to each electrode line of a PDP is displayed for each subfield during ADS driving.

<Description of the code | symbol about the principal part of drawing>

20: top plate 22: bottom plate

24: upper substrate 26: scanning electrode

27: discharge sustaining electrode 28: upper dielectric layer

30 bus electrode 31 protective layer

32: lower substrate 34: data electrode

36: lower dielectric layer 38: discharge space

40 fluorescent material 42 partition wall

44: discharge cell 46: PDP

In order to achieve the above object, a method of driving a plasma display panel includes supplying a reset pulse only once to discharge cells during a reset period, and the voltage level of the reset pulse is gradually maintained after being maintained for a predetermined period. Characterized in that it is reduced.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG. 5.

FIG. 5 is a view illustrating a method of driving an AC surface discharge plasma display panel according to an exemplary embodiment of the present invention. FIG. 5 is a waveform diagram illustrating driving waveforms supplied to respective electrode lines of a PDP for each subfield during ADS driving. Referring to FIG. 5, one subfield includes a reset period for initializing the full screen, an address period for writing data into the respective discharge cells while scanning the full screen in a sequential manner as in the conventional case, and a cell in which the data is written. They are divided into sustain periods for maintaining their light emission state. In the drawing, X represents a voltage waveform supplied to the data electrode line X shown in FIG. 2, and Y represents a voltage waveform supplied to the scan electrode line Y. Z represents the voltage waveform supplied to the discharge sustain electrode line (Z).

First, in the reset period, a reset pulse is supplied to the scan electrode line (Y) and the discharge sustain electrode line (Z). The positive reset pulse (+ Vr) is supplied to the scan electrode line (Y), and the negative reset pulse (-Vr) is supplied to the discharge sustain electrode line (Z). The reset pulse voltages supplied to the respective electrode lines Y and Z are maintained for a predetermined period of time. After maintaining the voltage for a period of time, the reset pulse voltage is gradually decreased. In the driving method of the present invention, unlike the conventional case of supplying a plurality of discharge pulses during the reset period, only one discharge pulse is supplied, and the pulse voltage is maintained for a predetermined period and then gradually decreased. In the address period, the negative scanning pulse (-Vs) is sequentially supplied to the scanning electrode lines (Y) for each scanning line of the PDP, and the positive data pulse is applied to each data electrode line (X) so as to be synchronized with the scanning pulse. Supply. Discharge cells are selected to cause sustain discharge during the address period. In the next sustain period, positive sustain pulses are alternately supplied to the scan electrode lines Y and the discharge sustain electrode lines Z. FIG. The difference from the conventional driving method is that the voltage and pulse width of the initial sustain pulse first supplied to the scan electrode line Y at the start of the sustain period are increased. As shown in Fig. 5, the voltage (+ Vw) of the first sustain pulse supplied at the start of the sustain period is made higher than the voltage (+ Vsus) of the subsequent sustain pulses supplied next. + Vw is higher than the voltage of the sustain pulse supplied in the conventional driving method. In addition, the pulse width of the initial sustain pulse is also wider than in the prior art. In the discharge cells selected during the address period, light is emitted while sustaining the discharge by these sustain pulses.

The discharge is formed between the scan electrode 26 and the discharge sustain electrode 27 of each discharge cell by the reset pulses + Vr and -Vr supplied during the reset period. At this time, charged particles are generated in the discharge space 38, and these charged particles are formed as wall charges in the upper and lower dielectric layers 28 and 36. In order to prevent the charged particles from recombining and disappearing in this process, the voltage of the reset pulse (+ Vr, -Vr) is maintained for a certain period of time. By providing the voltage sustain period as described above, the charged particles and the wall charges generated during the reset discharge can be continuously maintained. Electrons are mainly formed of wall charges near the scan electrode 26, and positive wall charges are formed near the discharge sustain electrode 27. The wall charges formed during the reset period serve to lower the address discharge voltage during the next address period. That is, since the positive pulse is applied to the data electrode line X and the negative pulse is applied to the scan electrode line Y in the address period, due to the voltage difference between the pulses and the wall charges formed during the reset period. The sum of the voltages and the voltage applied to the discharge cells during the actual address period appear as the sum of the driving voltage and the wall voltage supplied to each electrode. Accordingly, it is possible to lower the driving voltage to be supplied externally during address discharge. As described above, after the period in which the wall charges can be sufficiently formed in the respective discharge cells, the voltage of the reset pulse is gradually decreased to erase the discharge. At this time, the charged particles in the discharge space 38 are recombined to disappear. In the present invention, only one discharge pulse is supplied during the reset period, but the same procedure of initializing the discharge cells and forming the wall charges performed through the conventional priming, sustain, and erase discharges is performed through this process. By this method, the discharge occurs only once during the reset period, so that the number of minute light emission occurs is reduced, and the contrast of the screen is improved as compared with the conventional method.

In addition, in the present invention, the sustain pulse (+ Vw) first supplied at the start of the sustain period serves to supply a sufficient amount of charged particles and wall charges to the discharge cells at the beginning of the sustain period. By increasing the width of the first sustain pulse (+ Vw) supplied to the scan electrode line (Y) and increasing the voltage, a sufficient amount of wall charge is formed at the beginning of the sustain period for each discharge cell. In addition, due to the difference in scanning time during the address period, the amount of wall charges formed non-uniformly in each scan line becomes uniform for each discharge cell. In the present invention, since the wall charges are sufficiently formed in each discharge cell at the beginning of the sustain period, the response speed to the following sustain pulses (+ Vsus) is increased, and the efficiency and the screen brightness can be improved. In addition, the wall charge amount is uniform for each scan line during the address period, so that uniform operating characteristics are displayed for each cell during the sustain period. This uniformity of operating characteristics makes it possible to prevent malfunctions such as miss discharge and mis-discharge of the discharge cells during the sustain period, thereby obtaining stable operating characteristics.

As described above, in the method of driving the plasma display panel according to the present invention, the voltage of the reset pulse supplied during the reset period is maintained for a predetermined period and then gradually decreased. Accordingly, as a process of generating, maintaining and dissipating the charged particles through only one discharge during the reset period, wall charges are formed in the discharge cells, and the number of minute light emission occurs during the reset period is reduced compared to the conventional method. The contrast of the screen is improved. In the present invention, the voltage and pulse width of the sustain pulse supplied first at the start of the sustain period are increased. As a result, a sufficient amount of wall charges are uniformly formed in each discharge cell at the initial point of the sustain period, so that the brightness of the screen is improved and the operation characteristics of each cell are uniform, thereby preventing malfunction.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (3)

A method of driving a plasma display panel comprising: a reset period for initializing discharge cells, an address period for addressing the discharge cells, and a sustain period for sustaining discharge of the addressed discharge cells; Supplying a reset pulse only once to the discharge cells during the reset period; And the voltage level of the reset pulse is gradually decreased after being maintained for a predetermined period of time. The method of claim 1, Supplying the first sustain pulse only once to the discharge cells at the start of the sustain period; And supplying at least one second sustain pulse having a different voltage level and pulse width from the first sustain pulse to the discharge cells following the first sustain pulse. The method of claim 2, In order to generate wall charges in the discharge cells at the start of the sustain period and to equalize the amount of wall charges formed in the discharge cells, the voltage level and the pulse width of the first sustain pulse are determined by the second sustain. A method of driving a plasma display panel characterized in that it is larger than those of pulses.