KR100370491B1 - Driving Method of Plasma Display Panel Using Radio Frequency - Google Patents

Abstract

The present invention relates to a method of driving a high frequency plasma display panel to minimize pseudo contour noise.

The driving method of the high frequency plasma display panel of the present invention includes a step in which the sustain period is set nonlinearly in a plurality of subfields.

According to the present invention, pseudo contour noise can be minimized by setting the sustain period to non-propagation type.

Description

Driving Method of Plasma Display Panel Using Radio Frequency

The present invention relates to a method of driving a high frequency plasma display panel, and more particularly, to a method of driving a high frequency plasma display panel to minimize pseudo contour noise.

Plasma Display Panels (hereinafter referred to as "PDPs") display an image including characters or graphics by emitting phosphors by 147 nm ultraviolet rays generated upon discharge of He + Xe or Ne + Xe gas. Such a PDP is not only thin and easy to enlarge, but also greatly improved in quality due to recent technology development. These PDPs are largely classified into a DC drive method and an AC drive method.

The AC drive PDP has the advantages of low voltage driving and long life compared to the DC drive method, and thus will be spotlighted as a display device in the future. In addition, the AC drive type PDP displays an image by causing an AC voltage signal to be applied between electrodes arranged with a dielectric interposed therebetween so that discharge occurs every half cycle of the signal. The AC PDP uses a dielectric material in which wall charges are accumulated on the surface during discharge.

Referring to FIG. 1, an AC PDP includes an upper substrate 1 on which a sustain electrode pair 10 is formed, and a lower substrate 2 on which an address electrode 4 is formed. The upper substrate 1 and the lower substrate 2 are spaced in parallel with the partition 3 therebetween. A mixed gas such as Ne-Xe, He-Xe, or the like is injected into the discharge space provided by the upper substrate 1, the lower substrate 2, and the partition wall 3. The pair of sustain electrodes 10 are paired in two in one plasma discharge cell. Any one of the sustain electrode pairs 10 causes an opposite discharge to the address electrode 4 in response to the scan pulse supplied in the address period, and performs surface discharge with the adjacent sustain electrode 10 in response to the sustain pulse supplied in the sustain period. It is used as a scanning / sustaining electrode. In addition, the sustain electrode 10 adjacent to the sustain electrode 10 used as the scan / sustain electrode is used as a common sustain electrode to which a sustain pulse is commonly supplied. The dielectric layer 8 and the passivation layer 9 are stacked on the upper substrate 1 on which the sustain electrode pairs 10 are formed. The dielectric layer 8 serves to limit the plasma discharge current and to accumulate wall charges during discharge. The protective film 9 prevents damage to the dielectric 8 due to sputtering generated during plasma discharge and increases the emission efficiency of secondary electrons. This protective film 9 is usually made of magnesium oxide (MgO). The lower dielectric layer 6 is formed on the lower substrate 2 to cover the address electrode 4, and the partitions 3 for dividing the discharge space extend vertically. On the surfaces of the lower substrate 2 and the partitions 3, a fluorescent layer 5 which is excited by vacuum ultraviolet rays and generates visible light is formed.

In such an AC-type PDP, the sustain electrode pair 10 is alternately supplied with a sustain pulse having a duty ratio of 1, a frequency of 200 to 300 kHz, and a pulse width of about 10 to 20 kHz. The sustain discharge occurring between the sustain electrode pairs 10 in response to the sustain pulse occurs only once in a very short moment. The charged particles generated by the sustain discharges move along the discharge path between the sustain electrode pairs 10 according to the polarity of the sustain electrode pairs 10 and accumulate in the upper dielectric layer 8 to remain as wall charges. This wall charge lowers the driving voltage during the next sustain discharge, but reduces the electric field of the discharge space during the sustain discharge. Accordingly, when the wall charge is formed during the sustain discharge, the discharge is stopped. As such, the sustain discharge is generated only once at a very short time compared to the width of the sustain pulse, and most of the other time is consumed in the preparation of the wall charge and the next sustain discharge. For this reason, in the conventional PDP, since the actual discharge period becomes very short compared to the electric field discharge period, the luminance and discharge efficiency are inevitably low.

In order to solve the problem of low luminance and discharge efficiency of the AC PDP, a high frequency driving PDP (hereinafter referred to as "RFPDP") has been proposed, which generates sustain discharge using high frequency signals of tens to hundreds of MHz. In RFPDP, electrons vibrate in a cell by high frequency discharge.

Referring to FIG. 2, the RFPDP includes a lower substrate 12 having the address electrode 14 and the scan electrode 18 orthogonal to each other, and an upper substrate 30 having the high frequency electrode 28 parallel to the scan electrode 18. ). A first lower dielectric layer 16 is formed between the address electrode 14 and the scan electrode 18 to insulate the electrodes. The second lower dielectric layer 20 and the passivation layer 22 are stacked on the scan electrode 18. A lattice-shaped partition wall 24 is formed on the passivation layer 22. The phosphor 26 is coated on the surface of the lattice partition 24. The upper dielectric layer 29 is formed flat on the upper substrate 30 on which the high frequency electrode 28 is formed.

The RFPDP displays an image as a combination of a plurality of subfields including a reset period, an address period, and a sustain period as shown in FIG. In the reset period, the reset pulse RS is supplied to the scan electrode 18 to generate a reset discharge for forming uniform wall charges in the discharge cells of the full screen. In the address period, the scan pulse S is sequentially supplied to the scan electrode 18, and the data pulse D synchronized with the scan pulse S is supplied to the address electrode 14. At this time, an address discharge occurs in the discharge cell supplied with the data pulse D, and wall charges are formed on the surface of the second lower dielectric layer 20 by the address discharge. In the sustain period, the trigger pulse T is supplied to the scan electrode 18 and the address electrode 14 for a predetermined period. When the trigger pulse T is supplied to the scan electrode 18 and the address electrode 14, wall charges formed on the surface of the second lower dielectric layer 20 of the discharge cell selected in the address period are activated as space charges. In addition, trigger discharge is generated between the scan electrode 18 and the address electrode 14 to generate space charge. Such space charges vibrate in the discharge space according to the polarity of the high frequency signal R supplied to the high frequency electrode 28. The discharge gas is continuously ionized by the vibrating motion of the electrons. The vacuum ultraviolet rays generated by this discharge excite the phosphor 26 and generate visible light as the phosphor 26 transitions. In this way, RFPDP generates a discharge continuously during a sustain period by using a high frequency signal, thereby increasing luminance and discharge efficiency as compared with an AC PDP.

In the case where 256 gray levels are to be realized in the RFPDP, one frame period is time-divided into eight subfields. The reset period and the address period included in the subfields are allocated the same time for each subfield, while the sustain period is longer by 2 ⁿ depending on the weight of each subfield. In other words, the sustain periods included in each of the first to eighth subfields, that is, the period of the high frequency pulse R applied to the high frequency electrode 28 are 2 ⁰ , 2 ¹ , 2 ² , 2 as shown in FIG. 4. ³ , 2 ⁴ , 2 ⁵ , 2 ⁶ , 2 ⁷ . However, contour noise is generated in a moving image due to the characteristic of realizing the gray level of the image by the combination of the subfields. If pseudo contour noise occurs, pseudo contour appears on the screen, and thus the display quality is deteriorated. For example, if the left half of the screen is displayed with a gradation value of 128 and the right half of the screen is displayed with a gradation value of 127, and then the screen is moved to the left side, peak white (Peak White) is displayed at the boundary between the gradation values 128 and 127. That is, a white band appears. Conversely, if the left half of the screen is displayed with 128 gradation values and the right half of the screen is displayed with 127 gradation values, the screen moves to the right. A band will appear. This pseudo contour noise is a high frequency pulse (R) is supplied only in the eighth sustain period when expressing the gray scale of 128, and a high frequency pulse (R) is supplied only during the first to seventh sustain period when the gray scale of 127 is expressed. Will occur. In other words, when representing 128 gray scales, no discharge is generated by the time of 127 gray scales.

Accordingly, an object of the present invention is to provide a method for driving a high frequency plasma display panel which can minimize pseudo contour noise.

1 is a perspective view showing a conventional three-electrode AC surface discharge type plasma display panel.

2 is a perspective view showing a conventional high frequency plasma display panel.

FIG. 3 is a waveform diagram illustrating a driving waveform of the high frequency plasma display panel shown in FIG. 2.

4 is a diagram showing high frequency pulses allocated to the sustain period of the plasma display panel shown in FIG. 2; FIG.

Fig. 5 is a diagram showing high frequency pulses allocated to the sustain period of the high frequency plasma display panel of the present invention.

<Description of Symbols for Main Parts of Drawings>

1,30: upper substrate 2,12: lower substrate

3, 24: partition 4: address electrode

5,26 fluorescent layer 6,8,16,20,29 dielectric layer

9,22: protective film 10: sustain electrode pair

14: address electrode 18: scan electrode

28: high frequency electrode

In order to achieve the above object, the driving method of the high frequency plasma display panel according to the present invention includes a step in which a sustain period is set nonlinearly in a plurality of subfields.

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

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIG. 5.

5 illustrates harmonic pulses applied to the first to eighth subfields according to an embodiment of the present invention.

Referring to FIG. 5, in the present invention, when one frame gray scale is to be realized, one frame period is time-divided into eight subfields.

The sustain period included in each of the first to eighth subfields, that is, the period of the high frequency pulse applied to the high frequency electrode, is set nonlinearly. That is, in the present invention, the period of the high frequency pulse is allocated at the ratio of 2 ⁵ , 2 ⁰ , 2 ¹ , 2 ² , 2 ³ , 2 ⁴ , 2 ^7, 2 ⁶ .

In this manner, when the high frequency pulses are allocated, the harmonic pulses are supplied only in the seventh subfield period to express the gray level of 128. In order to express the gray level of 127, high frequency pulses are supplied only in the first to sixth subfields and the eighth subfields. In other words, when expressing 128 gray levels, no discharge is generated for the time of 63 gray levels.

Further, after expressing 128 gray levels, no discharge is generated for the time of 64 gray levels. Compared with the conventional driving method, when the 128 gray scales are represented, the discharge is not generated for the time of 127 gray scales.

However, in the present invention, no discharge is generated for the time of 63 gradations. That is, in the present invention, since the 128 gray levels are represented in the seventh subfield, the time for which no discharge occurs is shortened.

As described above, according to the driving method of the high frequency plasma display panel according to the present invention, the time allotted to the sustain period in each subfield is set nonlinearly. In this manner, the pseudo contour noise can be minimized by setting the sustain period to the non-propagation type.

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 (2)

In a driving method of a high frequency plasma display panel in which one frame includes a plurality of subfields, and the subfields are divided into a reset period, an address period, and a sustain period. And the sustain period is set non-linearly in the plurality of subfields. The method of claim 1, And the sustain period is set to a period of 2 ⁵ , 2 ⁰ , 2 ¹ , 2 ² , 2 ³ , 2 ⁴ , 2 ^7, 2 ⁶ .