Plasma display with split electrodes

A method of controlling electrodes of a pixel in a plasma display panel. The method includes applying a first voltage to a first electrode of the pixel during a sustain discharge involving the first electrode, and applying a second voltage to a second electrode of the pixel. The first voltage and the second voltage have a relationship that encourages the sustain discharge to extend to the second electrode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to plasma display panels, and more particularly, to a pixel architecture that controls discharge area to minimize addressing power and vertical crosstalk between pixels and that enhances sustain discharge of the pixels by controlling discharge area as a means to control power and brightness.

2. Description of the Related Art

Color plasma display panels (PDPs) are well known in the art. Visible light is emitted by phosphors within the panel in response to gas plasma discharges between a pixel's sustain and scan electrode. During an addressing period, sustain electrodes are generally driven with a common potential, while scan electrodes are selected individually. Since the electrodes are on an internal surface of a front plate, the light produced must pass through the electrodes. When transparent electrodes, e.g., indium tin oxide (ITO), are employed, the light simply passes through the electrode. Alternatively, non-transparent apertured electrodes may be devised that allow the light to pass through open apertures in the electrode.

An embodiment of an AC color PDP is disclosed in U.S. Pat. No. 6,118,214 to Marcotte (hereinafter “the '214 patent) in which apertured electrodes are employed on a front plate. More particularly, the AC PDP includes horizontal pairs of apertured sustain electrodes that connect to a sustain bus. Pairs of independent scan apertured electrodes, are interdigitated with the pairs of common sustain electrodes. The apertured electrodes are generally produced using opaque metallic electrode materials such as silver or a film stack of chrome-copper-chrome.

Contrast enhancement bars are horizontally situated in inter-pixel gaps between horizontally adjacent pixels to reduce the light reflectivity of the phosphor. The contrast enhancement bars are opaque and may be conductive or non-conductive. For additional description of contrast enhancement bars, see U.S. Pat. No. 5,998,935 to Marcotte.

During processing, the electrodes are covered by a dielectric layer and a magnesium oxide (MgO) layer. A back plate supports vertical barrier ribs and plural vertical column conductors. The individual column conductors are covered with red, green, or blue phosphors, as the case may be, to enable a full color display to be achieved. The front and rear plates are sealed together and a space there between is filled with a dischargeable gas.

A pixel is a region at an intersection of electrodes. For example, a pixel is defined at an intersection of a sustain electrode and an adjacent scan electrode on the front plate and three back plate column electrodes for red, green, and blue. A sub-pixel, or sub-pixel site, refers to an intersection of individual red, green, and blue column electrodes with the front plate scan/sustain electrode pair.

The PDP operating voltage and power are controlled by the space between adjacent sustain and scan electrodes (hereinafter referred to as a sustain gap), the width of the lines making up the apertured electrodes, and the overall width of electrodes. The sustain and scan electrodes are generally placed to provide a relatively narrow sustain gap and a relatively wide inter-pixel gap.

Alternating sustaining discharges form at the sustain gap, and spread out vertically. The discharge forms a positive column region branching a positively charged anode electrode and a negative glow region drifts across a negatively charged cathode electrode. In the case of apertured electrodes, the line widths and spacing are balanced to maximize light transmission and to maximize discharge voltage uniformity. For example, minimizing the line width to 40-60 microns and spacing the horizontal lines at a distance less than or near the sustain gap dimension (e.g., 100 microns) achieves this balance. In the paired electrode configuration the electrodes on each side of the inter-pixel gap are at the same potential, therefore the inter-pixel gap must be made sufficiently large to prevent plasma discharges from spreading and corrupting an ON or OFF state of an adjacent pixel.

The overall width of the apertured electrodes, the line widths, the line spaces and the dielectric glass thickness over the electrode combine to determine the pixel's discharge capacitance, which controls the discharge power and therefore brightness. For a given discharge power and therefore brightness of each discharge, a number of discharges in a predetermined period of time is chosen to meet an overall brightness requirement for the panel.

The paired front plate electrode configuration has the advantage of reduced inter-electrode capacitance, which reduces power dissipation resulting from charging and discharging of the inter-electrode capacitance of each sustain pulse. However, there is a possibility of vertical crosstalk resulting from the electrodes on either side of the inter-pixel gap being driven with the same potential. Vertical crosstalk occurs when a discharge at one discharge site spreads into a vertically adjacent discharge site, i.e., for an adjacent pixel, and affects the ON or OFF state of the adjacent pixel. The '214 patent utilizes a relatively large inter-pixel gap to help increase the vertical pixel to pixel isolation. Note that the back plate barrier ribs provide horizontal pixel isolation but no vertical isolation.

The greatest probability of vertical crosstalk occurs during the addressing period when each row is sequentially addressed to place desired sub-pixels in the ON state. In an addressing discharge, the plasma discharge forms between a selected scan electrode and a data electrode and the discharge's positive column spreads along the back plate data electrode to the sustain electrode. With an adjacent electrode at the same potential, the positive column can cross the inter-pixel gap and deplete the charge on an adjacent sub-pixel's sustain electrode. The presence of the contrast enhancement bar has been shown to have little effect on this address crosstalk mechanism.

SUMMARY OF THE INVENTION

The present invention provides a method and a pixel architecture for plasma display panels. Electrodes of the pixels are controlled to enhance operation of the pixels and to provide a method for controlling power and brightness.

A method embodiment of the present invention controls a discharge in a pixel by providing an electrode topology that is disposed with respect to the pixel to define a first area and a second area of the pixel, the first area being larger than the second area. The brightness of the discharge is controlled by selectively causing the discharge to occur in the first and second areas.

Another embodiment of the method of the present invention additionally controls the brightness by modulating at least one of the voltages in amplitude and/or duration.

In another embodiment of the method, the second area may be centered within the first area of the pixel.

In another embodiment of the method, the discharge may take place in a set up period, an address period or a sustain period.

In another embodiment of the method, the step of controlling controls brightness of the pixel.

In another embodiment of the method, a first sustain period of a first sub-field discharges the second area and a second sustain period of a second sub-field discharges the first area.

In another method embodiment of the present invention, there is applied a first voltage waveform to a first electrode of the pixel, a second voltage waveform to a second electrode of the pixel and a third voltage waveform to a third electrode of the pixel. The first voltage waveform, the second voltage waveform and the third voltage waveform have a relationship that during a sustain period encourages a sustain discharge to extend from the first electrode to the second and third electrodes.

In another embodiment of the method, during at least one sustain cycle of the sustain period, the second voltage waveform has a magnitude that is greater than a magnitude of the first waveform and less than a magnitude of the third waveform.

In another embodiment of the method, the first, second and third electrodes are selected from the group consisting of: sustain and scan. In a more specific embodiment, the first, second and third electrodes are selected from the group consisting of: (a) inner sustain electrode, middle sustain electrode and outer sustain electrode and (b) inner scan electrode, middle scan electrode and outer scan electrode.

In another embodiment of the method, during a set up period and an addressing period the second and third waveforms are substantially identical.

In another embodiment of the method, the first, second and third voltage waveforms are applied independently of one another.

In another embodiment of the method, the first electrode is narrower than the second electrode, which is narrower than the third electrode.

In another embodiment of the method, the sustain discharge involves the first electrode.

In another method embodiment of the present invention there is provided the additional steps of applying a first voltage waveform to an outer sustain electrode of the pixel, a second voltage waveform to a middle sustain electrode of the pixel, a third voltage waveform to an inner sustain electrode of the pixel, a fourth voltage waveform to an inner scan electrode of the pixel, a fifth voltage waveform to a middle scan electrode of the pixel and a sixth voltage waveform to an outer scan electrode of the pixel. The first, second, third, fourth, fifth and sixth voltage waveforms have relationships that (i) discourage an addressing discharge involving the inner sustain electrode and the inner scan electrode from extending to the middle and outer sustain electrodes and to the middle and outer scan electrodes, and (ii) permit a sustaining discharge involving the inner sustain electrode and the inner scan electrode to extend to the middle and outer sustain electrodes and the middle and outer scan electrodes.

In another embodiment of the method, the discharge is discouraged from extending to the first area.

A plasma display panel embodiment of the present invention includes a pixel and an electrode topology that is disposed with respect to the pixel to define a first area and a second area of the pixel, the first area being larger than the second area. A controller applies voltages to the electrode topology to control a brightness of a discharge of the pixel by selectively causing the discharge to occur in the first and second areas.

In another embodiment of the plasma display panel of the present invention, the second area is centered in the first area.

In another embodiment of the plasma display panel, the electrode topology comprises at least four electrodes, of which two define the second area and all of which define the first area.

In another embodiment of the plasma display panel, the discharge may take place in the setup period, address period or sustain period.

In another embodiment of the plasma display panel, the voltages modulate the discharge, thereby controlling the brightness of the pixel.

In another embodiment of the plasma display panel, a first sustain period of a first sub-field the discharge occurs in the second area and in a second sustain period of a second sub-field the discharge occurs in the first area.

In another embodiment of the plasma display panel, electrode topology comprises at least one split electrode set that comprises more than two electrodes.

In another embodiment of the plasma display panel, the discharge of the pixel is limited to the second area.

In another embodiment of the plasma display panel, the electrode topology further defines a third area of the pixel that is within the first area, wherein the second area is within the third area, and wherein the voltages initiate a discharge during a sustain period that spreads to the third area, but not to the first area, thereby confining a light output to the second and third areas of the pixel.

In another embodiment of the plasma display panel, the electrode topology comprises an outer sustain electrode, a middle sustain electrode, an inner sustain electrode, an inner scan electrode, a middle scan electrode and an outer scan electrode.

In another embodiment of the plasma display panel, the controller applies first, second, third, fourth, fifth and sixth voltages to the outer sustain, the middle sustain, the inner sustain, the inner scan, the middle scan and the outer scan electrodes, respectively. During a first cycle of the sustain period, a magnitude of the fifth voltage is greater than a magnitude of the fourth voltage and a magnitude of the sixth voltage. The first, second and third voltages each have a magnitude that is less than the magnitudes of the fourth and sixth voltages.

In another embodiment of the plasma display panel, during a second cycle of the sustain period, a magnitude of the second voltage is greater than a magnitude of the first voltage and a magnitude of the third voltage and the fourth, fifth and sixth voltages each have a magnitude that is less than the magnitudes of the first and third voltages.

In another embodiment of the plasma display panel, the electrode topology comprises a first electrode, a second electrode and a third electrode arranged to control discharge of plasma gas at the pixel. The controller applies a first voltage waveform, a second voltage waveform and a third voltage waveform to the first, second and third electrodes, respectively. The first, second and third voltage waveforms have a relationship that during a sustain period encourages a sustain discharge to extend from the first electrode to the second and third electrodes.

In another embodiment of the plasma display panel, during at least one sustain cycle of the sustain period the second voltage waveform has a magnitude that is greater than a magnitude of the first waveform and less than a magnitude of the third waveform.

In another embodiment of the plasma display panel, the first, second and third electrodes are selected from the group consisting of: sustain and scan.

In another embodiment of the plasma display panel, the first, second and third electrodes are selected from the group consisting of: (a) inner sustain electrode, middle sustain electrode and outer sustain electrode and (b) inner scan electrode, middle scan electrode and outer scan electrode.

In another embodiment of the plasma display panel, during a set up period and an addressing period the second and third waveforms are substantially identical.

In another embodiment of the plasma display panel, the first electrode is narrower than the second electrode and the second electrode is narrower than the third electrode.

In another embodiment of the plasma display panel, the first, second and third waveforms are applied independently of one another.

In another embodiment of the plasma display panel, the third electrode is configured as a loop and also serves as an electrode for an adjacent pixel.

In another embodiment of the plasma display panel, the second electrode is located between the first and third electrodes.

In another embodiment of the plasma display panel, at least one of the first and second electrodes is an apertured electrode.

In another embodiment of the plasma display panel, at least one of the first, second and third electrodes includes an electrically conductive transparent region.

In another embodiment of the plasma display panel, the electrode topology comprises a plurality of electrodes arranged to control a discharge of plasma gas at the pixel, the plurality of electrodes including an inner scan electrode, a middle scan electrode, an outer scan electrode, an inner sustain electrode, a middle sustain electrode and an outer sustain electrode; and wherein the controller applies a first voltage waveform, a second voltage waveform, a third voltage waveform, a fourth voltage waveform, a fifth voltage waveform and a sixth voltage waveform to the inner scan electrode, the middle scan electrode, the outer scan electrode, the inner sustain electrode, the middle sustain electrode and the outer sustain electrode, respectively. The first, second, third, fourth, fifth and sixth voltage waveforms have a relationship that (i) discourage an addressing discharge involving the inner sustain electrode and the inner scan electrode from extending to the middle and outer sustain electrodes and to the middle and outer scan electrodes, and (ii) permit a sustaining discharge involving the inner sustain electrode and the inner scan electrode to extend to the middle and outer sustain electrodes and the middle and outer scan electrodes.

In another embodiment of the plasma display panel, the inner scan electrode and the inner sustain electrode are separated by a first gap, wherein the inner sustain electrode and the middle sustain electrode are separated by a second gap. The inner scan electrode and the middle scan electrode are separated by a third gap. The first gap is smaller than either the second gap or the third gap.

In another embodiment of the plasma display panel, the inner sustain electrode is narrower than the middle sustain electrode and the middle sustain electrode is narrower than the outer sustain electrode. The inner scan electrode is narrower than the middle scan electrode and the middle scan electrode is narrower than the outer scan electrode.

In another embodiment of the plasma display panel, there is provided a pixel and at least one split electrode configured with at least a first electrode and a second electrode arranged to control plasma gas discharge at the pixel. A controller applies a first voltage to the first electrode and a second voltage to the second electrode independently of one another.

In another embodiment of the plasma display panel, the applying the first voltage to the first electrode and the second voltage to the second electrode (a) are performed during a sustaining discharge involving the first electrode and (b) encourage the sustaining discharge to extend to the second electrode.

In another embodiment of the plasma display panel, there is further provided a split electrode comprised of the first and second electrodes.

In another embodiment of the plasma display panel, there is further provided third, fourth, fifth and sixth electrodes. The first, second, third, fourth, fifth and sixth electrodes are an outer sustain electrode, a middle sustain electrode, an inner sustain electrode, an inner scan electrode, a middle scan electrode and an outer scan electrode, respectively. The controller applies voltages to each of the outer sustain electrode, middle sustain electrode, inner sustain electrode, inner scan electrode, middle scan electrode and outer scan electrode independently of one another.

In another embodiment of the plasma display panel, the inner scan electrode and the inner sustain electrode are separated by a first gap. The inner sustain electrode and the middle sustain electrode are separated by a second gap. The inner scan electrode and the middle scan electrode are separated by a third gap. The first gap is smaller than the either the second gap or the third gap.

In another embodiment of the plasma display panel, the applying voltages comprises: applying a first voltage waveform to the outer sustain electrode, applying a second voltage waveform to the middle sustain electrode, applying a third voltage waveform to the inner sustain electrode, applying a fourth voltage waveform to the inner scan electrode, applying a fifth voltage waveform to the middle scan electrode and applying a sixth voltage waveform to the outer scan electrode. The first, second, third, fourth, fifth and sixth voltage waveforms have relationships that (i) discourage an addressing discharge involving the inner sustain electrode and the inner scan electrode from extending to the middle sustain electrode and outer sustain electrode and to the middle scan electrode and the outer scan electrode, and (ii) permit a sustaining discharge involving the inner sustain electrode and the inner scan electrode to extend to the middle scan electrode and the outer sustain electrode and to the middle scan electrode and the outer scan electrode.

In another embodiment of the plasma display panel, the inner scan electrode and the inner sustain electrode are narrower than the middle and outer scan electrodes and the middle and outer sustain electrodes.

In another embodiment of the plasma display panel, the middle scan and middle sustain electrodes are narrower than the outer scan and outer sustain electrodes.

In another embodiment of the plasma display panel, the inner scan and inner sustain electrodes are substantially equal in width.

In another embodiment of the plasma display panel, the middle scan and middle sustain electrodes are substantially equal in width and the outer scan and sustain electrodes are substantially in width.

In another embodiment of the plasma display panel, a first gap separates the inner scan and sustain electrodes, a second gap separates the inner and middle scan electrodes and a third gap separates the inner and middle sustain electrodes. The first gap is narrower than the second and third gaps.

In another embodiment of the plasma display panel, a fourth gap separates the middle and outer scan electrodes and a fifth gap separates the middle and outer sustain electrodes. The second and third gaps are narrower than the fourth and fifth gaps.

In another embodiment of the plasma display panel, the second and third gaps are substantially equal and the fourth and fifth gaps are substantially equal.

In another embodiment of the plasma display panel, one or more of the outer sustain electrode, the middle sustain electrode, the inner sustain electrode, the inner scan electrode, the middle scan electrode and the outer scan electrode have a transparent electrode portion.

DESCRIPTION OF THE INVENTION

Elimination or suppression of vertical crosstalk between pixels allows for minimization of the size of an inter-pixel gap to maximize the pixel size, thereby increasing brightness.

FIG. 1is an illustration of a portion of a PDP100, and more particularly a portion of a pixel105located at an intersection of a first electrode115, a second electrode120and a data electrode110. A controller130applies voltages to first electrode115and second electrode120to provide control of first electrode115and second electrode120independently of one another. The first voltage and the second voltage influence whether a discharge involving first electrode115extends to second electrode120. First electrode115and second electrode120may operate as a split electrode.

During an addressing period, an addressing discharge is initiated between data electrode110and first electrode115. During the addressing discharge, controller130applies a first voltage to first electrode115, and applies a second voltage to second electrode120. The first voltage and the second voltage have a relationship that discourages the addressing discharge from extending to second electrode120.

Second electrode120is at an outer perimeter of pixel105, thus first electrode115may be regarded as an inner electrode, and second electrode120may be regarded as an outer electrode. First electrode115may serve as an inner scan electrode where second electrode120serves as an outer scan electrode, such an arrangement being regarded as a split scan electrode. Similarly, first electrode115may serve as an inner sustain electrode where second electrode120serves as an outer sustain electrode, and similarly such an arrangement is regarded as a split sustain electrode.

A pixel125is vertically adjacent to pixel105. As the addressing discharge is discouraged from extending to second electrode120, it is also discouraged from extending to pixel125. Thus, crosstalk from pixel105to pixel125is suppressed.

A pixel is an individually addressable picture element. The term sub-pixel is used herein to mean an individually addressable red, green or blue pixel. As a sub-pixel is individually addressable, it is also a form of pixel. Thus, the term “pixel”, in general, can mean either (a) a sub-pixel of an individual color or (b) a red sub-pixel, a green sub-pixel and a blue sub-pixel in a group.

During a sustaining discharge involving first electrode115, controller130applies a voltage to first electrode115, and applies a voltage to second electrode120to encourage the sustaining discharge to extend to second electrode120.

Although not represented inFIG. 1, first electrode115and second electrode120may be two electrodes of a split electrode pair. Furthermore, pixel105may be configured to have two split electrode pairs, namely, a split sustain electrode and a split scan electrode. The split sustain electrode is configured with an outer sustain electrode and an inner sustain electrode. The split scan electrode is configured with an inner scan electrode and an outer scan electrode.

On alternating sustaining discharges, a voltage is applied to the inner scan electrode or the inner sustain electrode while another voltage is applied to the outer scan electrode or the outer sustain electrode respectively. As the voltage applied to the outer scan electrode or the outer sustain electrode is increased above a minimum required voltage to effectively discharge the outer scan electrode or outer sustain electrode, additional brightness may be achieved as discharge power is increased.

FIG. 2is an illustration of a portion of a PDP200configured with split electrodes. Additionally, as explained below, some of the electrodes of PDP200are also configured as loop electrodes. A loop electrode services two adjacent pixel discharge sites separated by an inter-pixel gap. For further information relating to loop electrodes, see U.S. Pat. No. 5,852,347 to Marcotte. Additionally, an isolated or non-conductive contrast enhancement bar may be placed within the loop electrode to reduce light reflectivity.

PDP200includes outer sustain electrode terminals289and273, an inner sustain electrode terminal279, inner scan electrode terminals230and245, and an outer scan electrode terminal240. Outer sustain electrode terminal289is connected to an outer sustain electrode220. Inner sustain electrode terminal279is connected to inner sustain electrodes225and250. Inner scan electrode terminal230is connected to an inner scan electrode283. Outer scan electrode terminal240is connected to an outer scan electrode280. Inner scan electrode terminal245is connected to an inner scan electrode276. Outer sustain electrode terminal273is connected to an outer sustain electrode255.

Outer sustain electrode220is configured as a loop electrode having an upper portion220U and a lower portion220L. Upper portion220U services a sub-pixel296, and lower portion220L services a sub-pixel292. Outer sustain electrode220has an interior region between upper portion220U and lower portion220L that provides an inter-pixel gap294between sub-pixels296and292.

Outer scan electrode280is configured as a loop electrode having an upper portion280U and a lower portion280L. Upper portion280U services sub-pixel292and lower portion280L services a sub-pixel270. Outer scan electrode280has an interior region between upper portion280U and lower portion280L that provides an inter-pixel gap277between sub-pixels292and270.

Outer sustain electrode255is configured as a loop electrode having an upper portion255U and a lower portion255L. Upper portion255U services sub-pixel270and lower portion255L services an adjacent sub-pixel (not shown).

PDP200also includes a back plate205having vertical barrier ribs260and data electrodes210R,210G, and210B, which are coated with red, green, or blue phosphor, respectively. Barrier ribs260maintain a substrate gap between a front plate (not represented inFIG. 2) and back plate205and also separate data electrodes210R,210G, and210B from one another.

Back plate205may be fabricated either with or without horizontal pixel separators (not shown). Horizontal pixel separators are center aligned within the front plate inter-pixel gaps294and277, to prevent discharge crosstalk between vertically adjacent pixel sites. As the outer scan or sustain electrode voltages are increased for added brightness, such separators become advantageous.

Sub-pixel292is located at the intersection of data electrode210R, outer sustain electrode lower portion220L, inner sustain electrode225, inner scan electrode283, and outer scan electrode upper portion280U. Sub-pixel292is in a row, arbitrarily designated as row N. Sub-pixel292includes a sustain gap286between inner sustain electrode225and inner scan electrode283. It also includes a gap290between outer sustain electrode lower portion220L and inner sustain electrode225, and a gap282between inner scan electrode283and outer scan electrode upper portion280U.

Sub-pixel270is in a row N+1, adjacent to sub-pixel292. Note that sub-pixel270is located at an intersection of data electrode210R, and outer scan electrode lower portion280L, inner scan electrode276, inner sustain electrode250, and outer sustain electrode upper portion255U.

Sub-pixel296, only a portion of which is shown inFIG. 2, is in a row N−1, adjacent to sub-pixel292. Note that sub-pixel296is located at an intersection that includes data electrode210R and outer sustain electrode upper portion220U.

Outer sustain electrode lower portion220L and inner sustain electrode225are collectively referred to as a split sustain electrode. Similarly, inner scan electrode283and outer scan electrode upper portion280U are collectively referred to as a split scan electrode. Gaps290and282are then referred to as split electrode gaps.

Outer sustain electrode lower portion220L is at an upper outer perimeter of sub-pixel292, and outer scan electrode upper portion208U is at a lower outer perimeter of sub-pixel292. During addressing periods, outer sustain electrode220is electrically driven to discourage vertical crosstalk between sub-pixel292and sub-pixel296. Likewise during addressing, outer scan electrode280is driven to discourage, and preferably prevent, crosstalk between sub-pixel292and sub-pixel270. As a result, addressing discharges are limited to an inner electrode area287, reducing addressing discharge current as compared to discharging the entire sub-pixel292. During alternating sustaining discharges of sub-pixel292, outer scan electrode280is driven to encourage the discharge to extend beyond inner scan electrode283, and discharge outer scan electrode upper portion280U. Inter-pixel gap277is sized to prevent vertical crosstalk, and/or horizontal separators are included in the fabrication of barrier ribs260at the center of inter-pixel gap277. Similarly, outer sustain electrode220is driven to encourage the discharge to extend beyond inner sustain electrode225, and discharge outer sustain electrode lower portion220L. Inter-pixel gap255is sized to prevent vertical crosstalk, and/or horizontal separators are included in the fabrication of barrier ribs260at the center of inter-pixel gap294.

FIG. 3is a graph of a set of voltage waveforms for driving the electrodes ofFIG. 2. For example, an outer sustain waveform305drives outer sustain electrode220, an inner sustain waveform310drives inner sustain electrode225and250, an inner scan waveform315drives inner scan electrode283, an outer scan waveform320drives outer scan electrode280, and X data waveform325drives data electrode210R. The horizontal axis ofFIG. 3represents time and the vertical axis represents voltage, however, neither of the horizontal nor vertical axis is drawn to scale.

Plasma displays partition a 60 Hz display frame into 8 to 12 pulse width modulated sub-fields. Each sub-field produces a portion of the light required to achieve a proper intensity of each pixel. Each sub-field is partitioned into a setup period, an addressing period and a sustain period. The sustain period is further partitioned into a plurality of sustain cycles. The waveforms ofFIG. 3apply to one such sub-field, and the left hand side ofFIG. 3shows an end of a sustain period of a previous sub-field.

A current sub-field begins with a setup period, which resets any ON sub-pixels to an OFF state, and provides priming to the gas and MgO surface to allow for subsequent addressing. The intent is to place each sub-pixel at a voltage very close to a firing voltage of the gas. For example, when setting up sub-pixel292, during time t5-t15weak discharges are produced such that a resulting voltage, within the panel, between data electrode210R and inner sustain electrode225, relative to a voltage on inner scan electrode283, is the gas mixture's firing voltage.

After each sub-pixel is setup, the addressing period begins. In the addressing period, each row may be sequentially selected via a row select pulse, as shown on inner scan waveform315for a row N at t25-t30. If concurrently, a data voltage is applied to a sub-pixel's data electrode, e.g., a pulse at time t25on the X data waveform, then an addressing discharge will occur, setting the sub-pixel into the ON state.

On inner scan waveform315there is a row select pulse at time t25to select row N, i.e., the row in which inner scan electrode283is located. Note that a row select for inner scan electrode276, which is in row N+1, would be applied at a time other than time t25. Note also that inner scan waveform315and outer scan waveform320are identical to one another, except for the row select pulse at time t25. Also during the addressing period, and more particularly during an interval from time t20to time t35, outer sustain waveform305is at a voltage Viso, while inner sustain waveform310is at a voltage Ve, where Viso is less than Ve.

X data waveform325has a positive going data pulse at time t25. This data pulse being concurrent with the row select pulse on inner scan waveform315at time t25, initiates an addressing discharge in sustain gap286to turn ON sub-pixel292. The addressing discharge forms between data electrode210R and inner scan electrode283. Moments after the addressing discharge is initiated, the positive column of the discharge spreads across sustain gap286to inner sustain electrode225.

During the addressing period, since outer sustain electrode220is driven negatively (Viso) with respect to inner sustain electrode225(Ve), the addressing discharge will not progress across gap290to outer sustain electrode lower portion220L. Similarly, since outer scan electrode280is driven positively to a voltage Vscan, which is the row de-select voltage, the addressing discharge is prevented from progressing across gap282to outer scan electrode upper portion280U. Since the discharge currents are proportional to the discharge electrode area, the addressing discharge currents are greatly diminished as the addressing area287is an area between inner sustain electrode225and inner scan electrode283in sub-pixel292.

After being addressed, a sub-pixel is repetitively discharged in the sustain period to produce a desired brightness.

In the sustain period, if sub-pixel292was addressed during the addressing period, i.e., if an addressing discharge was initiated at time t25, then a number of sustaining discharges are produced in sustain gap286. The number of sustaining discharges produced in the sustain period is related to the desired brightness for sub-pixel292. Each sub-field typically has a different number of sustain pulses within a sustain period.

In the sustain period, outer sustain waveform305and inner sustain waveform310are identical to one anther, and inner scan waveform315and outer scan waveform320are identical to one another. Accordingly, for convenience, when discussing the sustain period, (a) outer and inner sustain waveforms305and310are collectively referred to as the sustain waveform, and (b) inner and outer scan waveforms315and320are collectively referred to as the scan waveform. Pulses of voltage Vs are applied to outer and inner sustain electrodes220and225, and alternated with pulse of voltage Vs being applied to inner and outer scan electrodes283and280, to repetitively discharge sub-pixel292.

A first sustaining discharge occurs between times t42and t45. At times t40and t42, the sustain waveform and scan waveform voltage polarities are reversed with respect to the addressing period so that the first sustaining discharge will produce a current flow from the scan electrode toward the sustain electrode. Between time t42and t45, a sustaining discharge forms at sustain gap286with the positive column spreading across inner scan electrode283, gap282, and outer scan electrode upper portion280U. That is, during the sustain period, the sustaining discharges are permitted to extend to outer scan electrode upper portion280U. The scan waveform provides a high sustain voltage Vs1to inner and outer scan electrodes283and280, thus providing ample voltage for the positive column to spread quickly across gap282. As a result, gap282can be wider than sustain gap286. As the slow moving negative glow expands due to the larger positive column it spreads across inner sustain electrode283, gap290, and outer sustain electrode lower portion220L.

Such an embodiment can be operated with line widths from 40 to 100 microns and with sustain gap and split electrode gaps of 60 to 120 microns. Since the light must pass around opaque electrodes, it is advantageous to have narrower lines and larger spaces.

FIG. 4is an illustration of a portion of a PDP400, similar to that of PDP200, where in place of electrodes220L,225,283and280U, there are non-transparent apertured electrodes415,430,450and440respectively. Each apertured electrode includes two opaque horizontal lines enclosing an aperture. For example, apertured electrode430includes two opaque electrodes420and435enclosing an aperture425. Similarly to PDP200, the outer sustain apertured electrodes405and415and outer scan apertured electrodes are looped about inter-pixel gaps410and445. In such a configuration, each apertured electrode will behave, as a solid electrode provided its aperture is not too large. Typical electrode line widths of 40 microns and apertures of 80 microns provide such a characteristic. Consequently, it is advantageous to make gap455equal to the spacing of aperture425. Additional shorting bars (not shown) may be placed within apertures, e.g., within aperture425, to bypass photolithographic open defects. For example, see U.S. Pat. No. 6,411,035 to Marcotte.

The configuration of two horizontal lines, e.g.,420and435, forming the apertured electrodes of PDP400, can be modified to vary the number of horizontal lines and apertures in either the outer apertured electrodes, e.g., electrodes415or440, or the inner apertured electrodes, e.g., electrodes430or450, to control a ratio of addressing discharge capacitance versus sustaining discharge capacitances. For example, a single horizontal electrode line could be implemented for the inner scan and inner sustain electrodes as inFIG. 2, e.g., inner sustain electrode225and inner scan electrode283, while three or more horizontal electrode lines could be implemented to widen the outer apertured electrodes,415and440.

The apertured electrode configuration of PDP400allows for larger pixels to be fabricated than that of PDP200. Since the operating characteristics are determined by the horizontal line width and spacing, increasing the horizontal line width, the spacing between horizontal lines, or the number of horizontal lines and spaces can extend the pixel size. As the pixel size is extended, it is generally necessary to increase the sustain pulse voltage to ensure that the discharges extend to the outer edges of each sub-pixel.

FIG. 5is an illustration of embodiment of a portion of a PDP500where an electrode includes an electrically conductive transparent region, i.e., a transparent electrode. PDP500has a sub-pixel505at an intersection of an outer sustain electrode512, an inner sustain electrode525, an inner scan electrode555and an outer scan electrode545. Outer sustain electrode512is configured with a transparent electrode515overlaid with a portion of an opaque metallic loop electrode510. Inner sustain electrode525is configured with a transparent electrode530overlaid with a metallic bus electrode520. Inner scan electrode555is configured with a transparent electrode535overlaid with a metallic bus electrode550. Outer scan electrode545is configured with a transparent electrode540overlaid with a portion of an opaque metallic loop electrode542.

This configuration of electrodes, i.e., a transparent electrode overlaid with a metal electrode, provides high brightness and excellent brightness uniformity. The high brightness results from high discharge capacitance. With high discharge capacitance, large discharges are much more apt to over spread and create vertical crosstalk. Additionally, the high capacitance reduces addressing operating margin due to voltage drops caused by high addressing discharge currents. Accordingly, on inner sustain electrode525and inner scan electrode555, the transparent conductor width of transparent electrodes530,535may be reduced or removed to reduce the address currents, and on outer sustain electrode512and outer scan electrode545, transparent electrodes515and540may be widened to supply increased sustaining discharge power.

FIG. 6is an illustration of a portion of a PDP having a sub-pixel with a three-electrode configuration. A PDP600includes a back plate605having vertical barrier ribs635and data electrodes610R,610G and610B coated with red, green, or blue phosphor, respectively. PDP600also includes a sustain electrode617, an inner scan electrode668, and an outer scan electrode662.

Sustain electrode617is configured with a transparent electrode620overlaid with a metallic electrode615. Inner scan electrode668is configured with a transparent electrode625overlaid with a metallic electrode665. Outer scan electrode662is configured with a transparent electrode630overlaid with a metallic electrode660. The metallic electrode material is an opaque metallic conductor.

A sub-pixel675is in a region at an intersection of data electrode610R, sustain electrode617, inner scan electrode668, and outer scan electrode662. Sub-pixel675is in a row N, and is vertically adjacent to a sub-pixel650in a row N+1. An outer scan electrode680is for a row N−1. A sustain electrode632, an inner scan electrode645and an outer scan electrode640are for row N+1. An inter-pixel gap655lies between sub-pixels675and650.

Sub-pixel675includes a sustain gap670located between sustain electrode617and inner scan electrode668. Outer scan electrode662is at an outer perimeter of sub-pixel675, and thus also borders inter-pixel gap655. Outer scan electrode662is electrically driven to discourage vertical crosstalk from sub-pixel675to sub-pixel650.

During an addressing discharge involving inner scan electrode668, a first voltage is applied to inner scan electrode668, and a second voltage is applied to outer scan electrode662. By selecting appropriate levels for the first and second voltages, the addressing discharge that forms between back plate605and inner scan electrode668is discouraged from extending to outer scan electrode662. The positive column will quickly engulf sustain electrode617while the negative glow will be limited to inner scan electrode668.

Addressing current is limited by capacitance of inner scan electrode668. Since outer scan electrode660is not involved in the discharge, the current is limited. PDP600offers improved brightness over PDP500due to the larger area of transparent electrode620, and less light shading than that caused by metallic bus electrode520.

Although PDP600is shown as being configured with sustain electrode617, inner scan electrode668and outer scan electrode662, the concept of suppressing vertical crosstalk can also be employed with inner and outer sustain electrodes. For example, sustain electrode617can be replaced with an inner sustain electrode and an outer sustain electrode that are controlled independently of one another to further limit the addressing discharge current. Thus, either or both of the sustain electrode and scan electrode can be configured with an outer electrode and an inner electrode.

FIG. 7is a block diagram of a circuit700for producing the waveforms ofFIG. 3. Circuit700is, in turn, composed of smaller circuits for controlling an outer sustain electrode, an inner sustain electrode, and inner scan electrode and an outer scan electrode independently of one another. Circuit700includes a sustain side waveform generator705and a scan side waveform generator710.

Sustain side waveform generator705generates a sustain waveform that serves as a source for inner sustain waveform310. The sustain waveform from sustain side waveform generator705is also routed to a switch701to serve as a source for outer sustain waveform305.

Scan side waveform generator710generates a scan waveform. The scan waveform is presented to row drivers715that drive rows of scan lines, e.g., scan line1through scan line480, and thus serves as a source for inner scan waveform315for row N. The scan waveform from scan side waveform generator710is also routed to a switch702to serve as a source for outer scan waveform320.

Each of switches701and702can be set to either a position A or a position B. InFIG. 7, switches701and702are shown in position A as they would be connected during the addressing period, e.g., from time t20to time t40inFIG. 3, to provide voltages for controlling the outer sustain electrode and the outer scan electrode to restrain the addressing discharge. Referring to the sustain side, the sustain electrodes are driven directly from sustain side waveform generator705. The isolation voltage Viso is a non-grounded voltage, for example, floating 50 to 100 volts below the output voltage of sustain side waveform generator705.

On the scan side, row drivers715are totem pole output row drivers that scan each row during the addressing period. There is a separate output for each display row connected to a respective inner scan electrode through terminals230and245. During the addressing period, the scan side waveform generator710generates a voltage Vscan of 75-150 volts. The outer scan electrodes and the high side of the totem pole outputs within row drivers715are tied to a common point of switch702, which provides a positive voltage relative to the output of scan side waveform generator710. This positive voltage provides a row de-select level during the addressing period.

During the addressing period, each inner scan electrode is sequentially pulsed low, to 0 V, to enable addressing of a selected row. An addressing discharge will then form at each sub-pixel site where an X-data electrode is driven to 50-75 volts.

During time periods other than the addressing period, switches701and702are set to position B so that the outer sustain electrode is driven directly from sustain side waveform generator705, and the outer scan electrode is driven directly from scan side waveform generator710.

Each of the embodiments described herein reduces the peak addressing discharge current, which occurs when all the pixels on a given line are addressed, and so lessens the current requirements of row drivers715. Furthermore, the sustaining discharge currents occurring during the sustain period are channeled from the outer scan electrodes through switch702, around, not through, row drivers715. The sustain currents from the individual inner scan electrodes will flow through the lower transistor of the totem pole outputs of row drivers715. In practice, each switch701and702uses a pair of high current transistors such as metal oxide semiconductor transistors (MOSFETs) or insulated gate bipolar transistors (IGBTs).

When scan and sustain electrodes are configured as split electrodes, (i.e., inner and outer scan electrodes, and inner and outer sustain electrodes), alternate driving techniques may be devised to utilize the split electrode configuration to further improve operating characteristics.

A first driving technique improves dark screen contrast ratio. Background glow light, produced by a setup voltage waveform producing a weak setup discharge, is contained to a center region of each sub-pixel site. Such a setup voltage waveform drives the outer electrodes with lower setup voltages while the prior voltage levels are used to drive the inner electrodes to discourage the setup discharge from extending to the outer regions of each sub-pixel. Reducing the setup discharge area, reduces the setup discharge light, and therefore improves the dark screen contrast ratio.

A second driving technique applies to the sustain time period. The outer electrodes of each split electrode pair are driven with higher sustain pulse voltages providing additional voltage to the outer electrodes to draw the discharge to the outer limits of each sub-pixel site. This allows the sustain voltage itself to be reduced which improves sustain luminous efficiency and also improves operating voltage margin.

For example,FIG. 2details each split electrode pair. Sustain gap286is at the center of sub-pixel292separating inner sustain electrode225and inner scan electrode283. Outer scan electrode280is separated from inner scan electrode283by gap282. Outer sustain electrode220is separated from inner sustain electrode225by gap290. In general, gaps290and282will be the same size as one another.

An improved dark screen contrast ratio is achieved by utilizing the row drivers715during the setup period to create a setup voltage waveform that applies the voltage Vscan to inner scan electrode283during the rising setup ramp (seeFIG. 3, time t5to time t10). The setup voltage waveform for outer scan electrode280does not have this voltage applied, as the scan side waveform generator710at time t10reduces its output from a setup voltage Vw by an amount equal to the voltage Vscan, e.g., 90-120 volts. With a reduced voltage applied to outer scan electrode280, a weak positive resistance setup discharge, which occurs during the rising ramp (time t5to time t10), is contained to inner scan electrode283where the higher voltage is present and is discouraged from extending to outer scan electrode280, thus reducing the light produced by the setup discharge.

Applying a higher voltage to the outer electrodes in each split pair, where higher voltages are required, may optimize sustaining discharge characteristics. A high electric field present at sustain gap286, which is relatively narrow, for example, about 80 microns, offers a relatively low initial firing voltage. However the voltage required for the sustaining discharge to spread fully across sub-pixel292may be 50 to 100 volts higher depending on dimensions of sub-pixel292and gas mixture. As a result, if a single sustain voltage is applied to fully discharge sub-pixel292, the center region of sub-pixel292is over-energized, where as at its extremes it is under-energized. If inner electrodes225and283are driven with the low ignition voltage, and outer electrodes220and280are driven with relatively higher voltage, then improvements in luminous efficiency and lifetime may be achieved.

FIG. 8is a block diagram, similar toFIG. 7, of a circuit800for controlling electrodes of a PDP. Circuit800is, in turn, composed of smaller circuits for controlling the electrodes.FIG. 9, described below in greater detail, shows a set of waveforms produced by circuit800.

Circuit800includes a switch801and a switch802. Each of switches801and802have positions A, B and C.

Switch802, during the setup period, is set to position A to allow outer scan electrode280to be driven directly by scan side waveform generator710. During the addressing period, switch802is set to position B to provide an offset voltage Vscan to outer scan electrode280. During the sustain period, an additional offset voltage, Vs3, may be switched ON with each sustain pulse by setting switch802to position C to boost the amplitude of each pulse to outer scan electrode280.

In contrast with circuit700, row drivers715have a voltage Vscan applied constantly for simplicity. “Latching up” is a parasitic condition caused by high currents flowing in a substrate of an integrated circuit. Actual row driver devices may require that Vscan, which is typically a relatively high voltage, be removed during the sustain period to prevent row drivers715from “latching up”.

Voltages Vscan and Vs3are AC coupled from scan side waveform generator710, through capacitors C2and C3, respectively, providing offset voltages that float with the output of scan side waveform generator710. The voltage applied to outer scan electrode280can be switched between the output of scan side waveform generator710, the voltage Vscan, and an additional voltage, Vs3, above the output of scan side waveform generator710. Similarly, row drivers715can switch each row, independently, between the output of scan side waveform generator710and a voltage, Vscan, above the output of scan side waveform generator710.

Switch801, during the setup period, is set to position A to allow outer sustain electrode220to be driven directly by sustain side waveform generator705. During the addressing period, switch801is set to position B to provide an AC coupled isolation voltage, Viso, to suppress vertical crosstalk. During the sustain period, switch801is set to position C to permit an AC coupled voltage, Vs3to be applied to outer sustain electrode220, synchronously with each sustain side sustain pulse, to provide additional amplitude to each pulse.

FIG. 9is a graph, similar to that ofFIG. 3, of a set of voltage waveforms produced by circuit800.FIG. 9shows an outer sustain waveform905, and inner sustain waveform910, an inner scan waveform915and outer scan waveform920, a scan generator waveform925and an X data waveform930.

Outer sustain waveform905is applied to outer sustain electrode220. Inner sustain waveform910is applied to inner sustain electrode225. Inner scan waveform915is applied to inner scan electrode283. Outer scan waveform920is applied to outer scan electrode280. Scan generator waveform925is generated by scan side waveform generator710. X data waveform930is applied to data electrode210R.

Relative toFIG. 3, the scan waveform generator voltage Vw inFIG. 9has been reduced by an amount equal to the Vscan voltage, between 75 and 150V. Since row drivers715are referenced to the output of scan side waveform generator710, row drivers715may be switched to output voltage Vscan during time interval t5to t10to produce the scan N waveform915, which is applied to the inner scan electrode for row N, i.e., inner scan electrode terminal283. During the setup period, t5to t20, switch802is set in position A so that the outer scan electrode280is driven with the outer scan waveform920, which is the same as scan generator waveform925.

At time t5, row drivers715are driven high to the voltage Vscan that is referenced to the output of scan side waveform generator710through a capacitor C2. Since row drivers715are referenced to the output of scan side waveform generator710, and since scan generator waveform925ramps at time t5, inner scan waveform915follows the ramp with an offset of Vscan volts. The slow ramp, coupled with the voltage approaching Vw+Vscan, creates a weak non-avalanching positive resistance discharge with inner scan electrode283discharging to both data electrode210R and inner sustain electrode225. This discharge forms the first half of the background glow intensity of the display. Since inner scan electrode283sources this discharge, a lower voltage ramp on outer scan electrode280from outer scan waveform920does not discharge and thus reduces the size of the physical area being discharged, thereby reducing the background glow intensity.

At time t10, referring to inner scan waveform915, outputs of row drivers715are switched to their low level, which is equal to the output of the scan side waveform generator710(see scan generator waveform925). As scan generator waveform925ramps down during time t10to time t15, inner scan waveform915will follow. Recall that during the setup period, switch802is set to position A, and therefore, outer scan waveform920will also ramp down. As the setup voltage waveform voltage ramps down, a slow positive resistance setup discharge will again occur, this time being sourced by data electrode210R and inner sustain electrode225. Since outer sustain electrode220and outer scan electrode280were not included in the rising ramp's setup discharge between time t5and time t10, they do not have sufficient wall charge to discharge during the falling ramp between time t10and time t15thus the setup discharge is discouraged from extending to outer scan electrode280and outer sustain electrode220. This reduces the light generated by the falling ramp, which accounts for the second half of the background glow's intensity. Outer scan electrode280follows both ramps so as to not affect the setup discharges on inner scan electrode283.

At time t20, the addressing period begins, and referring to inner scan waveform915, row drivers715switch high, bringing inner scan electrode283to the level Vscan. Switch802is set to position B during the addressing period, and so, referring to outer scan waveform920, outer scan electrode280is also driven to voltage Vscan. Thus, outer scan electrode280is excluded from the addressing discharge.

Between times t20and t35, each row is individually selected by a low going pulse on its respective scan electrode. For example, with reference to inner scan waveform915, a low-going pulse starting at time t25corresponds to a selection of row N, i.e., the row containing sub-pixel292. If present, the coincidence of an image data-dependent X data pulse on data electrode210R would trigger an addressing discharge at sustain gap286. The addressing discharge will form between the data electrode210R and inner scan electrode283. The discharge quickly creates a positive column region and a negative glow region. The negative glow will stay at inner scan electrode283whereas the positive column will spread across sustain gap286enveloping inner sustain electrode225, thus discharging area286within sub-pixel292.

Also between times t20and t35, referring to outer sustain waveform905, outer sustain electrode220is driven with an isolation voltage Viso. Referring to inner sustain waveform910, a voltage Ve is applied to inner sustain electrode225. Voltage Viso is less than voltage Ve. By placing outer sustain electrode220at a lower potential than that of inner sustain electrode225, the addressing discharge's positive column is discouraged, i.e., suppressed, from spreading across outer sustain electrode220. By containing the addressing discharge to the smaller area286between inner scan electrode283and inner sustain electrode225, rather than permitting the addressing discharge to extend to either or both of outer sustain electrode220and outer scan electrode280, addressing discharge currents are reduced. As the resistive voltage drop across the inner scan electrode283, and the row driver715's output resistance limits addressing margin, reducing the addressing discharge current improves the addressing margin.

During time t42to time t45, a first sustaining discharge occurs with the sustaining discharge current being sourced from the scan electrode pair, i.e. inner scan electrode283and outer scan electrode280U, to the sustain electrode pair i.e., outer sustain electrode220L and inner sustain electrode225. Referring to scan generator waveform925, scan side waveform generator710generates a voltage Vs1, which may be greater than the sustain voltage Vs. Scan generator waveform925is used to produce both inner scan waveform915and outer scan waveform920, while inner sustain waveform910and outer sustain waveform905are switched to ground (0V). Voltage Vs1is chosen so that the positive column region of the discharge spreads across both inner and outer scan electrodes283and280U. Although not shown inFIG. 9, in some embodiments of the invention, particularly where gap282is larger than sustain gap286, a higher voltage is applied to outer scan electrode280during the first sustaining discharge so that the sustaining discharge spreads across both inner and outer scan electrodes283and280U, thus discharging the full sub-pixel area292.

A second, third, and subsequent sustaining discharges occur with sustain and scan side waveform generators705and710producing sustain pulses of amplitude Vs volts. Synchronously with each sustain pulse edge, switches801and802connect the corresponding outer electrodes220or280to apply voltage Vs3. Specifically at time t45, outer sustain waveform905applies a voltage Vs3to outer sustain electrode220while inner sustain waveform910applies a voltage Vs to the inner sustain electrodes225. Similarly, at time t60, outer scan waveform920applies a voltage Vs3to outer scan electrode280while scan N waveform915applies a voltage Vs to the inner scan electrode283, the inner sustain electrodes are driven to voltage Vs and the outer sustain electrodes are driven to Vs plus Vs3.

Sustaining discharges are intended to extend to outer sustain electrode220and outer scan electrode280, and so, voltages, i.e., Vs3, applied to outer electrodes220and280are higher than voltages, i.e., Vs, applied to inner electrodes225and283. With higher voltages available to outer electrodes220and280, larger split electrode gaps290and282may be realized. For example, split electrode gaps290and282may be 150% the size of sustain gap286. Such an embodiment increases the size of the positive column region of the discharge, which has been shown to provide higher luminous efficiency. For further elaboration, see U.S. Pat. No. 6,184,848 to Weber.

Referring toFIG. 10, another embodiment of the present invention comprises a PDP1000, of which only a portion is shown. PDP1000includes a sub-pixel1092that includes a plurality of back plate barrier ribs1060, a back plate data electrode1010, three or more front plate sustain electrodes1015,1020and1025forming a split sustain electrode, which is driven by a sustain side controller1030. PDP1000also includes three or more front plate scan electrodes1035,1040and1045forming a split scan electrode connected to a scan side controller1050, which is driven by a scan side controller1050.

Sustain side controller1030provides independent control of at least three sustain electrodes1015,1020and1025. Scan side controller1050provides independent control of at least three scan electrodes1035,1040and1045. Independent control of each electrode provides the ability to control a subset of each split electrode to contain discharges to an inner most sub-pixel area1087bounded horizontally by barrier ribs1060and vertically by at least one sustain electrode1020and at least one scan electrode1040. Furthermore, independent control allows ascending voltages to be optionally applied to each electrode set (sustain or scan) during a sustain discharge to optionally allow the sustain discharge to discharge beyond the inner most area1087. PDP1000provides increased power and therefore brightness for each sustain discharge, while reducing the power and brightness of setup and addressing discharges.

For a given sustain discharge wherein the entire sub-pixel area is to be discharged, the sustain electrodes are the positively charged anode and the scan electrodes are the negatively charged cathode, separate voltages may be applied to sustain electrodes1025,1020and1015, such that the voltage applied to sustain electrode1015, typically 250 Volts, is greater than the voltage applied to sustain electrode1020, typically 220V, which is greater than the voltage applied to sustain electrode1025, typically 200V, while the scan electrodes are driven negative relative to the sustain electrodes to a common potential, which typically may be 0 Volt. As the sustain discharge forms, the discharge's positive column region will quickly spread across sustain electrodes1025,1020and1015, while the negative glow region will drift slowly across scan electrodes1035,1040and1045. On the next alternating sustain discharge, ascending voltages are applied to scan electrodes1035,1040and1045respectively, while sustain electrodes are driven to a common potential of 0 volt.

Subsequent to the given sustain discharge, removing the ascending voltages applied to sustain electrodes1025,1020and1015results in an ascending negative voltage across the gas when such electrodes become a cathode for the next alternating sustain discharge. That is, the outer most sustain electrode1015becomes the most negative due to the wall charge of the last discharge. This ascending negative voltage aids in the drift of the negative glow across the sustain (now acting as a cathode) electrodes1025,1020and1015, drawing the negative glow outward without requiring that additional voltages be applied to each cathode electrode.

The ability to control voltages independently allows reduced areas1087and1090to be discharged compared to the full sub-pixel area1092. Such an embodiment of the invention allows for controllable discharge areas. It is desirable to make sustain gap1086between inner sustain electrode1025and inner scan electrode1035small, typically 50 to 100 microns to reduce the firing voltage of the gas. It is also desirable to make a gap1022between split electrodes1020and1025and a gap1017between split electrodes1015and1020larger, for example, 100 to 200 microns to improve the luminous efficiency of the display. Similarly, a gap1037between split electrodes1035is smaller than a gap1042between split electrodes1040and1045.

FIG. 10also shows varied electrode widths among the electrodes within each split electrode. It is typically desirable to minimize the widths of opaque metallic electrodes within the discharge area, to reduce the amount of light blocked by the conductor. Additionally, the narrow innermost electrodes reduce the power and brightness of setup and addressing discharges. The power applied during the sustain discharges is proportional to the electrode area, therefore wider middle and outer electrodes provide greater discharge power and therefore brightness. A compromise must be made with regard to the opaque conductor width to maximize luminous efficiency. Since less light is produced at the extremity of the discharge cell, the outermost electrode may be the widest.

As plasma displays increase in size, it is desirable to increase the size of the pixel.FIG. 10may be expanded to include additional middle sustain electrodes1020in the space1017, and including an additional matching scan electrodes in the space1042. In this case, additional driving circuits may be added to sustain controller1030and scan controller1050. Independent control of each electrode allows sufficient voltage to be applied to each electrode to allow the discharge to spread across each split electrode set. Also, independent control allows the discharge to be contained to an additional area within the sub-pixel area. For example, the additional area could be contained within sub-pixel area1092with area1090contained within the additional area and an additional sustain electrode and an additional scan electrode positioned within gaps1017and1042, respectively.

For a configuration of four or more split electrodes as shown inFIG. 16, the pixel may be extended in size by adding additional scan and sustain electrodes in pairs, and applying the ascending voltage scheme as demonstrated inFIG. 13. In such an embodiment of the invention, it is contemplated that applying additional negative voltages to the sustain electrodes during the first sustain discharge could be beneficial to further draw the negative glow across the split sustain electrode set.

Referring toFIG. 11, another embodiment of the present invention comprises a PDP1100, of which only a portion is shown. PDP1100generally comprises three split electrodes (sustain and scan) as compared to the two split electrodes of PDP200(FIG. 2). PDP1100comprises a middle sustain electrode1101placed between an inner sustain electrode1125and an outer sustain electrode loop1120. Similarly, a middle scan electrode1181is placed between an inner scan row N electrode1183and an outer scan electrode loop1180.

When photolithographic processes are employed to manufacture the electrodes ofFIG. 11, it is possible to have small breaks in the electrodes forming an electrical open circuit. To provide a redundant current path in the event of an electrode open circuit within the display area, middle scan electrodes may be connected on the sustain side by shorting electrode1190similar to outer sustain electrode1120and outer scan electrode1180constructed as loop electrodes. Similarly, inner sustain electrodes may be connected by shorting electrode1191and middle sustain electrodes may be connected by shorting electrode1192.

Referring toFIG. 13, the waveforms applied to the three electrode PDP1100ofFIG. 11are those ofFIG. 9with minor changes to the sustain period.FIG. 13corresponds withFIG. 11such that outer sustain electrode1120is driven with outer sustain waveform1305, middle sustain electrode1101is driven with middle sustain waveform1307etc.

For the first sustain discharge, which occurs between times t42and t45, sustain electrodes1101,1120and1125are driven to a common potential of 0 volts, while ascending voltages are applied to each of the scan electrodes. Scan N electrode1183is driven to a voltage Vs1, middle scan electrode1181is driven to a voltage Vs4, and outer scan electrode1180is driven to a voltage Vs3, where Vs3is greater than Vs4, which is greater than Vs1. Vs1may be at or above voltage Vs as required to improve operating margin. With ascending voltages applied to the split scan electrode set1183,1181and1180respectively, the positive column of the first sustain discharge will spread from a sustain gap1186across the split scan electrode set discharging the lower half of an area1192. With equal voltages applied to sustain electrodes1101,1120and1125, the negative glow may or may not fully spread across the split sustain electrode set.

For the second sustain discharge, ascending voltages are applied to the split sustain electrode set1125,1101and1120respectively, while the split scan electrode set11831181and1180is returned to 0V. While the voltages applied to each scan electrode are equal, the wall charge on the dielectric surface from the previous discharge in combination with the drop in voltage applied to the electrode, results in an ascending negative voltage across the split scan electrode set. Thus, the second sustain discharge yields a positive column spreading across the split sustain electrode set, while the negative glow spreads across the split scan electrode set, and the entire cell area1192is discharged.

Similarly, subsequent sustain discharges occur wherein the ascending voltages are alternately applied to the scan and sustain electrode sets while scan and sustain electrodes are driven to 0V respectively.

Referring toFIG. 12, relative toFIG. 8switch circuits801and802are replicated as switch pair1255supplied by a voltage V3where V3is greater than V4to create an additional ascending voltage level necessary to drive the third and outer most sustain and scan electrodes1205and1220respectively which correspond to outer sustain electrode1120and outer scan electrode1180. Capacitors C5and C6create floating versions of V4, and capacitors C3and C4create floating versions of V3. Thus, when the sustain or scan generator outputs Vs to the inner scan or sustain electrodes1183and1125, Vs4equal to Vs+V4may be applied to the middle scan or sustain electrodes1181and1101, and Vs3equal to Vs+V3may be applied to the outer scan or sustain electrodes1180and1120. Similarly, voltages Vscan and Viso float on output of the scan and sustain waveform generators respectively.

As in PDP200(FIG. 2) with the waveforms ofFIG. 9, an inner electrode area1187of PDP1100ofFIG. 11is discharged for setup and addressing operations, while the outer areas above and below area1187in sub-pixel1192are discharged for sustain operations. Operation of switch1204is the same as that of switch802and is operated in tandem with switch1203so that during the setup and addressing periods the middle and outer scan electrodes are driven through terminal B to isolate discharge activity to area1087occurring on inner scan electrode1183from the middle and outer scan electrodes1181and1180. During the sustain period, switch1203and1204toggle between terminals A and C so that when the scan side waveform generator produces a sustain pulse of voltage Vs, switches1203and1204select terminal C.

Similarly, Switch1202is operated in tandem with Switch1201so that during the setup period terminal A is selected to operate the middle and outer sustain electrodes1101and1120with the inner sustain electrode1125and during the addressing period, the middle and outer sustain electrodes1101and1120are connected through terminal B to the isolation voltage, Viso so that addressing discharges involving the inner sustain electrodes do not extend to the middle and outer sustain electrodes. During the sustain period, switches1202and1205toggle between terminals A and C so that when the sustain side waveform generator produces a sustain pulse of voltage Vs, switches1202and1201select terminal C. The total voltage applied to the outer sustain and middle sustain electrodes is Vs3and Vs4, respectively.

For embodiments including four or more split electrodes, additional switch circuit pairs1255may be added, each circuit requiring a voltage greater than V3.

Referring toFIG. 14, another embodiment of the present invention comprises a PDP1400with electrodes that have varying electrode widths and varied electrode spacing. Specifically, from the center of the pixel a sustain gap1435, an electrode1401exhibits a width, which that is narrower than that of an electrode1405, which is narrower than electrode1410. The respective electrodes1450,1455, and1460also exhibit the same width variation. Additionally, electrodes1405,1410,1455,1460, each have a transparent electrode portion1415,1420,1465, and1470, respectively. Electrode gap or space1435is smaller than an electrode space1430, which is less than an electrode space1425.

Respective electrode spaces1440and1445also exhibit the same electrode spacing as spaces1430and1425, respectively. Electrodes1401,1405and1410are connected to a waveform generator1475while electrodes1450,1455and1460are connected to waveform generator1480.

Each waveform generator1475and1480controls its respective electrodes such that setup and addressing operations are performed about sustain gap1435, affecting wall charges in a center pixel area1490. During a sustain period, independent control of the voltages allows the sustain discharge to be controlled to the center of pixel area1490, or the discharge may be extended to a middle pixel area1493, or to a full pixel area1495. The sustain discharge area is controlled by each waveform generator1475and1480by the voltages applied to each of its electrodes. Each waveform generator1475and1480in turn applies voltages to its respective electrodes to create discharges alternating in opposite directions. For each voltage application, the waveform generates successively increasing voltages to its respective electrodes to expand the discharge area, and conversely successively decreasing voltages to contain the discharge within a region.

Referring toFIG. 14, in a preferred embodiment, the inner scan and inner sustain electrodes have widths narrower than that of the middle or outer electrodes. Scan electrode widths should be matched with an equal width sustain electrode counter part. That is, a narrow, typically 40-80 micron wide inner scan electrode should be matched with an equal width inner sustain electrode. Narrow inner electrodes reduce the power and, therefore, brightness of the background light produced by setup discharges. Narrow inner electrodes also minimize the amount of light blocked by opaque metallic conductors. The middle and outer electrodes may be fabricated with wider electrodes either of the transparent type1420with metallic bus electrodes1410, or with apertured electrodes as in U.S. Pat. No. 6,411,035 to Marcotte. Wider middle and outer transparent electrodes, typically 100 to 250 microns allow for large pixel areas, high power levels and therefore high brightness to be achieved. The width of the bus electrodes1410,1405,1455,1460is minimized and chosen to meet electrode resistance and manufacturability requirements while blocking as little light as possible.

The waveforms shown inFIGS. 3 and 9, and the circuits ofFIGS. 7 and 8are described herein as being used with the PDP ofFIG. 2. However, the concepts ofFIGS. 3 and 9, and7and8are also applicable to the PDPs ofFIGS. 1,4-6,10and11.

In another embodiment of the invention, PDP1400can be operated to provide controllable brightness. The power and brightness of low order sub-fields can be reduced by limiting the pixel area discharged with each sustain pulse within a sustain period of a sub-field. For low brightness sub-fields, an inner pixel area is sustained, while for high brightness sub-fields, the entire pixel area may be discharged. The number of split electrodes determines the number of brightness levels obtainable, while the individual electrode widths and spaces determine the brightness of each level.

Referring toFIG. 15, there is provided a set of waveforms for operating PDP1400with the circuitry ofFIG. 12to contain the sustain discharges to the region1493. This method of operation is desirable to reduce the light output when sustain discharges of low intensity are required. Since ascending voltages are required to cause the discharge to spread across the split electrode set, the omission of such ascending voltages will not allow the discharge to spread: Consequently, during the first sustain discharge t42-t45, the outer scan electrode switch1203, selects terminal A, the output of the scan generator. Concurrently, switch1204selects terminal C, the floating voltage V4, while the output of the sustain generator is at 0 volts. As a result, the voltage required for the positive column portion of the discharge to spread, Vs3, is not applied, so the positive column will be contained to the split scan electrode area of1493. Similarly, the negative glow portion of the discharge requires the application of a negative voltage on the outer sustain electrode1410relative to the middle sustain electrode1405for the negative glow to spread. With switch1202applying voltage V3, during t42-t45, there is insufficient voltage for the negative glow to spread beyond the middle sustain electrode1405of area1493. With the second and subsequent discharges, each outer electrode applies voltage Vs in the high state, and voltage V3in the low state, and the discharges are contained within area1493.

The same methodology may be applied to additional middle scan and sustain electrode pairs, to provide brightness control based upon a variable discharge area.

FIG. 16shows the frame timing of a very generic 8 sub-field PDP addressing implementation. Recent PDP displays use more sub-fields and different weightings to achieve 256 or more gray levels. To achieve 256 gray levels at a given pixel site, one or more sub-fields are addressed to activate the desired sustain periods. For example, to achieve a brightness at a pixel at gray level20, the pixel needs to be addressed and sustained in sub-fields SF3and SF5. SF3produces a relative ratio of the sustain period of 4 and SF5produces a relative ratio of the sustain period of 16. The summation therefore makes 20. As shown, each sustain period is weighted by powers of 2 so that the summation of all 8 sub-fields is 256 levels.

Individual sub-field brightness has traditionally only been performed by controlling the number of sustain pulses. As PDP's have improved, the brightness per discharge has increased and this trend will continue into the future. As the brightness per discharge increases, the number of sustain discharges required for a given brightness will decrease. Also, power reduction schemes involve limiting the number of sustain pulses to reduce power dissipation. These conditions can result in the low order sub-field requiring a brightness of less than one sustain cycle. Therefore, a new method is required to control the brightness of a single discharge.

With the PDP ofFIG. 14, and the methodology ofFIG. 15both of these conditions can be accommodated. For example if the total brightness is to be divided by 4, then the weighting of each sub-field must be divided by 4. Hence, SF8's relative ratio of the sustain period would be reduced from 128 to 32. The relative brightness of SF1must be 1/128 of the brightness of SF8, requiring a relative ration of ¼, SF2would be ½ and SF3would be 1. If the per discharge brightness of the PDP is such that a single sustain cycle comprising 2 discharges, produces more light than is required, then a fractional area may be employed to produced the lower light requirement.

To achieve these fractional relative ratio's, the areas1490,1493and1495must be operated such that the brightness of area1490is half of the brightness of area1493, which is half the brightness of area1495. Two methods are available to meet this requirement. Firstly, the areas may be chosen, giving consideration to the fact that greater light is produced in the center area of a pixel, than at the extremes. Therefore, area1493will be greater than 2× area1490. Likewise, area1495will need to be greater than 2× the area1493. Secondly, in selecting the voltages to be applied to the middle and outer electrodes sets, higher voltages will produce more light, and so increased light may be produced at the outer areas by increasing voltages Vs3and Vs4to apply more power to the extremities.

It should be understood that various alternatives and modifications of the present invention could be devised by those skilled in the art. Nevertheless, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.