Plasma display paired addressing

There is provided a method for controlling electrodes in a plasma display. The method includes providing addressing signals to (a) a first electrode in a first row, a second electrode in a second row, a fifth electrode in a fifth row and a sixth electrode in a sixth row; and subsequently to (b) a third electrode in a third row and a fourth electrode in a fourth row. The second row is adjacent to the first row, the third row is adjacent to the second row, the fourth row is adjacent to the third row, the fifth row is adjacent to the fourth row and the sixth row is adjacent to the fifth row.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to plasma displays, and more particularly, to a plasma display in which vertical crosstalk between pixels is suppressed without adversely affecting wall charges of electrodes.

2. Description of the Related Art

A plasma display includes a front plate and a rear plate sealed together and having a space therebetween filled with a dischargeable gas. The front plate includes horizontal rows of electrodes, each row being configured with a sustain electrode in parallel with a scan electrode. The scan electrodes and the sustain electrodes are covered by a dielectric layer and a magnesium oxide (MgO) layer. The back plate supports vertical barrier ribs and vertical column electrodes. In a color display, individual column electrodes are covered with red, green, or blue (RGB) phosphors. A pixel is defined as an area proximate to an intersection of (i) a scan electrode and a sustain electrode, and (ii) three column electrodes for colors red, green, and blue, respectively. A subpixel corresponds to an intersection of a red, green or blue column electrode with an electrode pair of a sustain electrode and a scan electrode.

The scan electrodes are driven individually in an addressing period in which each row may be selected such that sub-pixels along that row may be addressed via an addressing discharge triggered by the application of a data voltage on a vertical column electrode. During a sustain period, a common sustain pulse is applied to all scan electrodes to repetitively generate plasma discharges at each sub-pixel site addressed during the addressing period.

The sustain electrodes provide a reference point for the scan electrodes during the addressing operation. During the sustain period, a common sustain pulse is applied to all sustain electrodes out of phase with the sustain pulses applied to the scan electrodes, such that plasma discharges alternate direction between sustain and scan electrodes.

There are plasma displays in which pairs of sustain electrodes are interdigitated with pairs of scan electrodes. In one example, the electrodes are arranged in a sequence of:row1, sustain electrode;row1, scan electrode;row2, scan electrode;row2, sustain electrode;row3, sustain electrode;row3, scan electrode;row4, scan electrode;row4, sustain electrode;etc.
Thus, the scan electrodes of rows1and2form a first pair of scan electrodes, and the scan electrodes of rows3and4form a second pair of scan electrodes. The sustain electrodes of rows2and3form a pair of sustain electrodes that is interdigitated with the first and second pairs of scan electrodes.

The interdigitation of the pairs of electrodes results in a lower inter-electrode capacitance as compared to non-interdigitated electrodes. The lower inter-electrode capacitance is of benefit in a large area plasma display.

An interpixel gap is a region of space between adjacent pixels. In a case where an interpixel gap spacing is made small, a common potential present on a pair of electrodes can result in an erroneous crosstalk discharge and/or wall charge leakage in a neighboring pixel site, particularly in a vertical dimension. Note that for interdigitated pairs of electrodes, as described above, some interpixel gaps fall between adjacent scan electrodes, and some interpixel gaps fall between adjacent sustain electrodes.

A sustain gap is a region of space between a scan electrode and a sustain electrode within which the discharge occurs. A positively charged electrode serves as an anode and a negatively charged electrode serves as a cathode. When a sufficient voltage is applied across the sustain gap, the gas will break down and form a discharge plasma. The discharge plasma has two distinct regions, namely a positive column and a negative glow. The positive column is predominantly composed of fast moving electrons seeking a positive charge on the surface of the anode electrode. Conversely, the negative glow contains slow moving ions drifting toward and across the negatively charged cathode electrode. The duration of the discharge is limited by the amount of charge on the dielectric surfaces of the electrodes.

Each scan electrode is driven by an independently addressable scan driver. During an addressing period for a pixel, the scan driver for the pixel's scan electrode outputs a row select pulse that is coincident with a data pulse being applied to a column electrode of the pixel. Consequently, an address discharge occurs between the pixel's scan electrode and sustain electrode. The address discharge produces a positive column region that can spread across an interpixel gap that separates sustain electrodes, and produces a negative glow region that can reduce the wall charge on the adjacent scan electrode across an interpixel gap that separates a scan electrode pair.

U.S. patent application Ser. No. 10/305,560 describes a technique of vertical crosstalk suppression coupled with interlaced addressing that minimizes positive column crosstalk. However, when the interlaced addressing addresses at a first scan electrode in a scan electrode pair, some wall charge leakage occurs at the discharge site of the second scan electrode in the scan electrode pair, thus reducing the wall charge of the second scan electrode. More specifically, the slow moving negative glow portion of the address discharge spreads across the first scan electrode and has a tendency to deplete the wall charge on the second scan electrode. Subsequently, when the second scan electrode is addressed, the reduced wall charge requires a higher addressing voltage that would have been required had the wall charge not been reduced. The higher addressing voltage is undesirable because power dissipation is proportional to the square of the voltage, and positive column crosstalk is more likely to occur at higher addressing voltages.

SUMMARY OF THE INVENTION

A method for controlling electrodes in a plasma display includes providing addressing signals to (a) a first electrode in a first row, a second electrode in a second row, a fifth electrode in a fifth row and a sixth electrode in a sixth row; and subsequently to (b) a third electrode in a third row and a fourth electrode in a fourth row. The second row is adjacent to the first row, the third row is adjacent to the second row, the fourth row is adjacent to the third row, the fifth row is adjacent to the fourth row and the sixth row is adjacent to the fifth row.

A plasma display includes a first electrode in a first row, a second electrode in a second row adjacent to the first row, a third electrode in a third row adjacent to the second row, and a fourth electrode in a fourth row adjacent to the third row. The first and second electrodes are enabled and disabled concurrently with one another, and the third and fourth electrodes are enabled and disabled concurrently with one another.

In the plasma display, vertical crosstalk between pixels is suppressed without adversely affecting wall charges of electrodes and without adversely requiring a higher addressing voltage for an adjacent pixel. Also, addressing margin is improved by reducing the minimum addressing voltage required to address the second scan electrode in a pair.

DESCRIPTION OF THE INVENTION

FIG. 1is an illustration of a configuration of electrodes in a plasma display, a portion of which is illustrated and designated with as plasma display100. Plasma display100includes a plurality of sustain electrodes105and a plurality of scan electrodes. Ten individuals of sustain electrodes are shown and designated as sustain electrodes B-1, B-2, . . . , B-10. Similarly, ten individuals of scan electrodes110are shown and designated as scan electrodes A-1, A-2, . . . , A-10.

Pairs of sustain electrodes105are interdigitated with pairs of scan electrodes110. For example, scan electrodes A-1and A-2form a pair of scan electrodes, and scan electrodes A-3and A-4also form a pair of scan electrodes. Sustain electrodes B-2and B-3form a pair of sustain electrodes that is interdigitated with (i) the pair of scan electrodes A-1and A-2, and (ii) the pair of scan electrodes A-3and A-4. Note further that scan electrodes A-1and A-2are between sustain electrodes B-1and B-2, and scan electrodes A-3and A-4are between sustain electrodes B-3and B-4.

Each of the sustain and scan electrodes includes a metal portion and an electrically conductive transparent region. For example, a metal portion204is shown for sustain electrode B-1, and a transparent region203is shown for scan electrode A-1. Transparent region203is made of a material such as indium tin oxide (ITO), through which light can pass. Such materials are only semi-conductive and so the metal portion204provides a highly conductive path to support the low conductivity of the transparent material. As the metal portion204is opaque, a trade off exists between transparency and conductivity.

Vertical barrier ribs prevent a discharge at a discharge site from affecting a horizontally neighboring discharge site. For example, a barrier rib205prevents discharge sites206-1through206-10, which are shown as being on the left side of barrier rib205, from affecting neighboring sites to the right side of barrier rib205.

A pixel is defined as an area proximate to an intersection of (i) a scan electrode and a sustain electrode, and (ii) three column electrodes (not shown) for colors red, green, and blue, respectively. A subpixel corresponds to an intersection of a red, green or blue column electrode with an electrode pair of a sustain electrode and a scan electrode. The operations in the present disclosure are applicable to both a pixels and a subpixels, but for simplicity, describes the operations in the context of a pixel.

An interpixel gap208is shown between scan electrodes A-1and A-2, i.e., between rows1and2. An interpixel gap207is shown between sustain electrode B-2and sustain electrode B-3, i.e., between rows2and3. An interpixel gap209is shown between sustain electrode B-4and sustain electrode B-5, i.e., between rows4and5. Although not designated with reference numbers an interpixel gap also exists between rows3and4, and between each of adjacent rows5–10.

Bus x120may be configured as either a single conductor in common with each of sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10, or it may be configured as a plurality of discrete lines for individually controlling sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10. Similarly, busy115may be configured as either a single conductor in common with each of sustain electrodes B-3, B-4, B-7and B-8, or it may be configured as a plurality of discrete lines for individually controlling sustain electrodes B-3, B-4, B-7and B-8.

An image is displayed by plasma display100by configuring states, i.e., ON or OFF, of pixels of plasma display100. Time is partitioned into frames, and each frame is partitioned into subfields.

FIG. 2is a graph of various signals that are applied to the electrodes ofFIG. 1. The signals include scan electrode drive signals A1through A10, a sustain bus x signal, a sustain bus y signal, and an X data signal.FIG. 2represents a subfield, which is, in turn, partitioned into a setup period, an addresssing period and a sustain period.

During the setup period, any ON pixels are turned OFF, and a weak discharge is generated at each display sub-pixel to prime the magnesium oxide layer in preparation for addressing.

During the addressing period, scan drive signals A1–A10are applied to scan electrodes A-1through A-10, respectively, where a low-going scan drive signal A1–A10(from voltage Vscan to voltage Vselect) enables its corresponding row for addressing. InFIGS. 1 and 2, a sequence for addressing scan electrodes A-1through A-10is represented by addressing sequence201and addressing sequence202.

After a given row is enabled, column drivers (not shown) are loaded with image data. InFIG. 2, the X Data waveform represents an output of a column driver a column driver lines. The column drivers apply column voltage Vx to selected column electrodes. The coincidence, at a pixel site, of a selected row, i.e., a low pulse provided by A1–A10, and an applied column voltage Vx, initiates a weak discharge that cascades into a discharge between the selected scan electrode110and its neighboring sustain electrode105.

At the beginning of the addressing period, the sustain bus y signal reduces the voltage supplied to sustain electrodes B-3, B-4, B-7and B-8(from Ve to Viso). This disables sustain electrodes B-3, B-4, B-7and B-8for the first half of the addressing period. Note that during the first half of the addressing period, the sustain bus x signal is at voltage level Ve, which enables sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10.

InFIG. 2, during the second half of the addressing period, an X data pulse is shown coinciding with a low-going pulse on scan drive signal A4. Assume that this coincidence of signals causes an address discharge at discharge site206-4. Crosstalk between sustain electrode B-4and sustain electrode B-5is minimized by the lower potential (i.e., Viso) on sustain electrode B-5during the second half of the addressing period. This is because the enabling voltage Ve on sustain electrode B-4is referenced to the voltage on scan electrode A-4, and the disabling voltage Viso on sustain electrode B-5, when referenced to the voltage on scan electrode A-4is a lower magnitude than the enabling voltage Ve.

During addressing sequence201, scan electrodes A-1and A-2are addressed sequentially, followed by scan electrodes A-5and A-6, and then scan electrodes A-9and A-10. Sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10are enabled by being driven high by the sustain bus x signal, to initiate address discharges, sequentially, at discharge sites206-1,206-2,206-5,206-6,206-9and206-10. Note that sustain electrodes B-3and B-4are disabled by being driven low, by the sustain bus y signal, to prevent a positive column from spreading across interpixel gaps, e.g., interpixel gap207, between sustain electrodes105. Addressing sequence202occurs subsequently to addressing sequence201.

During addressing sequence202, scan electrodes A-3, A-4, A-7, and A-8are addressed sequentially. Sustain electrodes B-3, B-4, B-7, and B-8are enabled by being driven high by the sustain bus y signal, to initiate address discharges, sequentially, at discharge sites206-3,206-4,206-7and206-8. Note that sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10are disabled by being driven low by the sustain bus x signal.

While each address discharge at scan electrodes A-1, A-3, and A-5, for example, will deplete some charge from scan electrodes A-2, A-4, and A-6, respectively, the same address discharge energizes the gas that produces priming for the discharges at scan electrodes A-2, A-4, and A-6. This priming is a stronger benefit to addressing than the wall charge depletion is a deterrent, and thus, improves the overall addressing margin. Addressing margin is an operating window between the minimum voltages required to address all the sub-pixels in the display and the maximum voltages which may be applied before vertical crosstalk occurs.

The address discharge at discharge site206-3will form between scan electrode A-3and an intersecting vertical column electrode driven with the data voltage. As the address discharge progresses, a fast moving positive column extends towards sustain electrode B-3driven with the enabling voltage Ve. The positive column will not extend across interpixel gap207due to the lower isolation voltage Viso applied to sustain electrode B-2. Concurrent with the positive column growth, the negative glow region of the address discharge will spread slowly across the scan electrode A-3. Although retarded from spreading across interpixel gap209to scan electrode A-4by the application of voltage Vscan on scan electrode A-4, the negative glow will reduce the wall charge on the vertical column electrode and scan electrode A-4in the area surrounding interpixel gap209.

As the address discharge at scan electrode A-3completes, the MgO surface and the gas volume are highly energized, and so if discharge site206-4is addressed immediately following the addressing of discharge site206-3, the addressing of discharge site206-3serves as a priming to facilitate the formation of an address discharge at discharge site206-4. As the discharge progresses, a fast moving positive column extends towards sustain electrode B-4, which is driven with the enabling voltage Ve. Because of the lower isolation voltage Viso applied to sustain electrode B-5, the positive column will not extend across interpixel gap209to sustain electrode B-5.

Note that the electrode configuration, particularity with the arrangement of bus y115and bus x120, allows sustain electrodes B-3and B-4to be driven with the enabling voltage Ve, through bus y115, for the addressing of scan electrodes A-3and A-4, while bus x120is driven with the isolation voltage Viso, to limit the growth of the positive column. In partnership, the paired addressing sequence allows bus x120and bus y115to be switched once, mid-way through the addressing period, to minimize the power dissipation consumed by switching sustain electrodes105from the enabling voltage Ve to the isolation voltage Viso.

FIG. 3is a block diagram of a controller300for providing the sustain bus x signal to bus x, the sustain bus y signal to bus y, and the scan drive signals A1–A10to scan electrodes A-1through A-10, respectively. Note that the sustain bus x signal is a single signal, and the sustain bus y signal is a single signal. Thus, controller300is suitable for a configuration of plasma display100in which bus x120is a single conductor in common with each of sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10, and bus y115is a single conductor in common with each of sustain electrodes B-3, B-4, B-7and B-8.

FIG. 4is a block diagram of a controller400that may serve as an alternative to controller300. In controller400, discrete signals B1, B2, b5, B6, B9and B10, for driving sustain electrodes B-1, B-2, B-5, B-6, B-9and B-10, respectively, and discrete signals B3, B4, B7and B8are for driving sustain electrodes B-3, B-4, B-7and B-8, respectively, Thus, controller400is suitable for a configuration of plasma display100in which bus x120and bus y115are configured as a plurality of discrete lines.

Once completed, the address discharge places the addressed pixel in the ON state. Any column not driven will remain in the OFF state. While the address discharge does produce visible light, it is not of sufficient brightness to represent the image properly. Accordingly, a sustain period follows the addressing period after the last row has been addressed.

During the sustain period, the scan generator and a sustain generator (not shown) supply alternating sustain pulses so that a momentary ac-plasma sustain discharge occurs on an application of each sustain pulse. Each sustain discharge produces ultra violet light that excites surrounding phosphor to produce visible light. Each subfield within a frame contains a sufficient number of sustain pulses and, in-turn, discharges, to achieve a desired brightness for each subfield. Since each pixel can be addressed independently in each subfield, a large color palate is obtainable.

It should be understood that the foregoing description is only illustrative, and that various alternatives, combinations and modifications of the teachings described herein could be devised by those skilled in the art. For instance, the teachings are applicable to other AC plasma displays and waveform configurations, where an address discharge could potentially extend across a pixel and spread across an inter-pixel gap, affecting the address ability of an adjacent sub-pixel. The present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.