JPH04229896A - Control method for ac plasma display panel - Google Patents

Abstract

PURPOSE: To adjust the total luminance and intermediate luminance of the AC plasma display panel. CONSTITUTION: The 'write' state or 'erasure' state of cells (C1-C36) arranged in (n) lines (L1-44) is set with a command and then a maintaining signal for placing those cells in the 'write' state is applied to the cells. One feature is that this method inhibits >=1 maintaining signals (SE, SAE) from being transmitted to cells of at least one line (L1-L9) so as to make the luminance of the signal lower than any other line.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to a method for adjusting the brightness of an AC plasma display panel type screen. This method is used to operate in lines or bands to create local features of over- or under-brightness on the screen.

0002

BACKGROUND OF THE INVENTION Alternating current plasma display panels, known as AC PDPs, are designed to separate addressing functions (information write or erase commands) from the maintenance of a photocharge used to generate most of the useful light. It has memory characteristics that make it The method of adjusting the overall brightness of the screen in this way consists of adjusting the frequency of the sustain signal that maintains the discharge. This maintenance causes the cells in the "written" state to emit light.

The operation and structure of AC PDPs are well known. For example, French Patent No. 2,417,848 shows a type of panel with two intersecting electrodes to define a discharge cell. In this panel, address discharge and sustain discharge are set up between two same electrodes. These panels also have, for example, an address discharge and a sustain discharge as described in European patent application no.
It is also of the coplanarity-maintaining type in which one cell is defined by two intersecting electrodes, which can occur between different electrodes, as shown in FR 2 629 265 and FR 2 629 265. In AC PDPs, whether coplanar or not, a cell is addressed (i.e., written and erased) by selecting two corresponding intersecting electrodes; A suitable square wave voltage is applied to create a potential difference that produces a write or erase discharge.

Standard addressing methods use operations one line at a time. In this case, all cells of one line are all in the same state, e.g. "erased" state ("half-selected")
A command is given to perform the action. This operation is then followed by a selection operation during which one or more selected cells of the line are "written." This half-selection and selection operation is performed for each line during the address phase with a time delay corresponding to the duration of one line cycle from one line to the next. In each line cycle, this address phase is generally followed by a particular sustain phase which causes cells in the "write" state to be activated between two consecutive address phases for each line of cells.

Addressing by half-selection and selection operations is generally carried out by superimposing an address square wave on a basic square wave, as shown, for example, in French Patent Application Nos. 8,811,248 and 8,811,247. . Taking coplanar sustain type AC PDPs as an example, these panels generally have an array of column electrodes that have only address states and intersect sustain electrode pairs. Each pair is formed by address-sustain electrodes having address and sustain functions. Each intersection of a column electrode and a pair of electrodes defines one of the cells arranged in a matrix of lines and columns. A pair of sustain electrodes corresponds to each cell line.

Selective addressing occurs between the column electrodes and the address-sustain electrodes. Half-selective addressing (
one entire line) is performed between two electrodes in the same pair. A sustain discharge is obtained by applying a sustain signal to two electrodes in a pair. This maintenance is generally accomplished by causing the voltage signal of one of the electrodes, such as the address-sustain electrode, to rise and the sustain electrode to fall, typically at the same time or at least in close proximity to each other. These are added together to generate a sustaining discharge. This is generally achieved by a periodic voltage square wave applied to two electrodes of a pair. This square wave is of opposite polarity and constitutes the sustain signal.

A voltage square wave is thus permanently applied to all cell lines. These are square waves that form the sustain signal in the sustain phase and the basic square signal in the address phase. Address square waves (which perform write or erase operations) are superimposed on these fundamental square waves only at the address-sustain electrodes of the addressed lines. The fundamental square wave has approximately the same amplitude as the signal sustaining square wave and can at least generate light emission.

[0008]

The address-sustain electrodes are electrically separated into individual units, the sustain electrodes simultaneously receiving the same square wave and generally connected together. A.C.
In PDPs, brightness is generally adjusted in two ways. - Manipulate the frequency of the sustain signal (playing on
) to make it comprehensive (for the entire screen). The brightness of each dot is the same in this case and is proportional to the sustain frequency. or - dot by dot by temporal framing as shown for example in FR 2,519,170 and FR 2,536,565. In this way intermediate brightness levels known as gray shades are obtained. These gray shades give a tonal effect to the displayed image or, for example in the case of computer menus, the display of uniform zones at low brightness. These two methods cannot be used in intermediate cases such as brightness adjustment by band or line packets.

[0009]

SUMMARY OF THE INVENTION The method of the present invention is applicable not only to the overall brightness adjustment but also to the brightness adjustment in intermediate cases described above. Furthermore, the method of the present invention is particularly applicable to multicolor AC PDPs for color balance. The method of the invention is for the control of an AC plasma display panel having a plurality of cells arranged in a matrix of lines and columns. This method consists of creating a "written" or "erased" state of cells by a command, and applying a sustain signal to those cells that activates the cells in the "written" state. including inhibiting the transmission of one or more sustain signals toward the cells of at least one line so as to reduce the brightness of that line.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an AC plasma display panel to which the method of the present invention can be applied. In this example, panel 1 is coplanar. It has an array of column electrodes X1-X4,
These electrodes are sustain electrode pairs P1-P arranged in a line.
intersects with 9. Each electrode pair P1-P9 is address sustain electrode Y
1-Y9 and sustain electrodes E1-E9, the address-sustain electrodes Y1-Y9 first satisfy the address function in conjunction with the column electrodes X1-X4, and then perform the sustain function together with the sustain electrodes. As a result, the address-sustain electrodes Y1-Y9 have to be electrically separated into individual units, each connected to a separate output of the line address register 3. This register 3 provides the signal SAE necessary for address and maintenance functions.

Sustain electrodes E1-E9 have only a sustain function. They are therefore all connected to the same output of the panel generator 4 from which they receive the sustain signal SE. Column electrodes X1-X4 have an address function. They are therefore electrically separated into individual units and
Each is connected to a separate output of the column address register 5, which provides an address signal SA. Operating commands and synchronization commands for registers 3 and 5 and generator 4 are provided by control unit 1.
2 will be managed as before. 1 column electrode X1
- The intersection of X4 and the pair of electrodes P1-P9 is the cell C1-C3
6, and these cells form a matrix arrangement of lines L1-L9 and columns.

In this example, a screen of 36 cells is defined by nine pairs of electrodes P1-P9 forming four columns X1-X4 and nine lines L1-L9. The number of these lines and columns is arbitrary, for example 480, 1000
A screen with a book or more lines may be formed. One feature of the first embodiment of the present invention is that the sustain signal SE from the pulse generator 4 is not required;
That is, these sustain signals SE are not applied to at least one line L1-L9. This is achieved by not applying these sustain signals to the corresponding sustain electrodes E1-E9. If these signals are not applied to the sustain electrodes E1-E9 of all lines L1-L9, there will be no sustain discharge and the brightness of the screen will therefore decrease. This brightness is increased by reapplying these signals.

Local effects of under- or over-brightness can be obtained by acting on only a few lines, for example grouped together as packets, rather than on all lines. For example, if no sustain signal is applied to the second, third, seventh, and eighth sustain electrodes E2, E3, E7, and E8, then the pairs P2, P3, P7, and
8, that is, no sustain discharge occurs in the cells formed by lines L2, L3, L7, and L8. The amount of light emitted from the cells in these lines is small, and the cell line L1 receives signals as usual.
, L4, L5, and L8, a zone with lower brightness appears on the screen.

Thus, by removing the sustain signal applied to a particular sustain electrode, coplanar sustain is removed for the corresponding lines L1-L9 and the light generated by the cells of these lines is transferred to the column electrodes X1-X4. This is caused only by the discharge generated between the address and sustain electrodes Y1-Y9. The reverse is done, for example, to obtain local hyperbrightness of lines L2, L3, L7, L8. The sustain signal is applied to these lines L2, L3, L7, L8 and not to the other lines L1, L4, L5, L6, L9. These two levels of brightness can be obtained, for example, simply by actuating the switch I1 between the pulse generator 4 and the sustain electrodes E1-E9. This is extremely simple compared to conventional methods that require complicated methods such as changing the frequency of the sustain signal.

In the method according to the invention the sustaining signals SE are not removed, but their transmission to the cell is inhibited. Changing from one brightness level to another can be done for the entire screen. In that case, it is only necessary to stop or set the transmission of the sustaining signal SE, for example, by means of the switch I1. Changes in brightness can also be made as packets of one or more consecutive lines at predetermined locations or at arbitrary locations, as described above. If these lines are intended, they are separated from each other and e.g. by the same packet, e.g. the second switch I2 for each packet as shown in FIG.
The generator 4 may be connected to the maintenance lines E3, E4 by.

In another method, sustain electrodes are used for the lines L1-L9 whose brightness is to be increased. For example, line L
When increasing the brightness of sustain electrodes E2 and L3, only sustain electrodes E2 and E3 are used, and the others are not used. This operation can also be performed by a computer program that can act on all lines L1-L9 or only one of them. To counter this effect, electronic switching elements such as transistors T1-T9 (indicated by dotted blocks) are connected to sustain electrodes E1-E.
9 in series. These elements are the control device 1
2 (conventionally), and by means of this control device 12 the sustain electrodes E1-E9 receiving the sustain signal SE are electronically selected.

Another feature according to the invention is the color adjustment of the multicolor panel. If cells of the same color are grouped into the same packet of sustain electrodes, each packet is given two brightness levels. For example, the cells on lines L1, L4, L7 can correspond to blue B, the cells on lines L2, L5, L8 can correspond to red R, and the cells on lines L3, L6, L9 can correspond to green V. When these three line groups are respectively connected to the generator 4 by switches (not shown), two brightness levels are obtained for each color. Since the sustain signal SE from the generator 4 is not sent to some or one of the sustain electrodes E1-E9, the potential difference generated between the two electrodes of the corresponding pair P1-P9, i.e., the above-mentioned rising or rising edge. The effect is to reduce the amplitude of the falling edge to the point where no discharge occurs between the two electrodes. Therefore, according to another embodiment of the present invention, the above effect can be achieved by using the signal SA which is effective for the sustain operation.
This is obtained by operating at least one level of the address-sustain electrodes Y1-Y9 in sending only a portion of E to this electrode.

FIGS. 2(a), (b), and (c) show the pair P1-P.
Figure 2(a) shows an example of a sustain signal added to 9.
is the signal SA applied to address-sustain electrodes Y1-Y9
E, FIG. 2(b) shows the signal SE applied to the sustain electrodes E1-E9, and FIG. 2(c) shows the potential difference SAE- generated between two electrodes of one and the same pair P1-P9 by application of these signals or one of them. Indicates SE. At time t0, signal SA
E is a stable positive potential +V1 with respect to the reference voltage VR, signal SE is a stable negative potential -V2 with respect to VR, and the potential difference SAE-SE is positive and has a value equal to the sum of voltages V1 and V2. +V3 (V3=V1+V2).

At time t1, signal SAE is at negative potential -
V1, and the value V5 corresponding to V2-V1 (V5=V2
-V1), resulting in a negative change in the potential difference SAE-SE. At time t1' approaching time t1, the signal SE is inverted and changes from negative -V2 to positive voltage +V2, and the difference S becomes -V3.
Generates a new negative change in AE-SE. This change is added to the voltage at time t1 to generate a sustain discharge (not shown). At time t2, the signal SE is inverted and becomes -V2, and V
5 (V5=V2-V1), resulting in a positive change in the difference SAE-SE. At time t2' close to time t2,
The signal SAE goes from -V1 to +V1, resulting in a positive change in the difference SAE-SE to +V3, resulting in a new sustaining discharge. At time t3, the same changes as occurred at time t1 are repeated, the signal SAE goes to -V1, and the difference SAE
-SE becomes V5. In normal operation, a positive square wave signal SE (shown as a dotted line) at time t3' close to time t3
occurs, and at this point in time t3' and point in time t4 the same effect as described for points in time t1' and t2 occurs.

If according to the invention this square voltage signal SE is not sent to one or more of the sustain electrodes E1-E9, then
The sustaining discharge from time t3' to t4 corresponds to the pair P1-P9.
removed. Therefore, from time t3' to t4, signal SAE is -V1, maintenance is discontinued, and if these voltages are properly adjusted, no light emission occurs. Thus, the difference signal SAE-SE is maintained at V5 (V5 = V2 - V1) from time t3 to t4', and at time t4',
After the positive change of the signal SAE which is +V1, it becomes +V3. This does not reduce the functional efficiency of the discharge cell in the next cycle (memory necessary for efficient functioning is saved) and the same functional level is maintained at times t1, t1', t2.
, t2' as at time t5, t5', t6, t6
′ is obtained. However, it is possible to cause the same effect on one or more of these address-sustain electrodes Y1-Y9 by not sending the signal SAE to one or more of these electrodes to cause one or more sustain abort operations as described above. Possibly, this inhibition of the transmission of signal SAE takes place directly in the line address register 3, for example.

Thus, in the prior art, time t8' corresponds to a positive change of signal SAE from -V1 to +V1, and the next time t9 corresponds to its negative change from +V1 to -V1. These changes are shown by dotted lines in FIG. 2(a). However, according to the invention, this signal is not applied to at least one of the address-sustain electrodes Y1-Y9, and therefore sustain abort is applied for the corresponding pair P1-P9. At time t8', no light is emitted, that is, the difference SAE-SE remains at V5=V2-V1 from time t8 to t10 even if there is a change in signal SE at time t8. Of course, the principle of sustain abort with the signal SAE applied to the address-sustain electrodes can be applied to all panels. However, it can be applied selectively per electrode or per electrode packet. All the previously mentioned possibilities for sustain electrodes are available here as well, but finer tuning is significantly facilitated by varying the number of edges removed.

FIGS. 3A to 3E show that, for example, three pairs of electrodes P1, P2, and P3 are maintained by sustain electrodes E1 and E2.
, E3 in a different manner for each pair. FIG. 3(a) shows the address signal SA applied to column electrodes X1-X9.
(b) shows the signal SAE applied simultaneously and identically to all address-sustain electrodes Y1-Y9. Figure 3 (
c), (d), and (e) are signals SE1, SE2, and S applied to the first, second, and third sustain electrodes E1, E2, and E3, respectively.
Shows E3. Transmission of sustain electrode SE1 to electrode E1 is totally prohibited. In this case, the light emission of line L1 is reduced to such a level that it occurs only between the column electrode and the address-sustain electrode, and the luminance of this line is, for example, 30 cd/m
The minimum value Lmin is 2. The sustain signal SE2 sent to the sustain electrode E2 is the maximum number, so the brightness of the second line L2 is the maximum value Lmax, which is, for example, 100 cd/m2. The number of sustain signals SE3 sent to the sustain electrodes E3 is, for example, 5.
2, in which case the third line L3
The brightness of is the minimum brightness Lmin +2・(Lmax −Lm
in)/5, which is 58 cd/m2.

The invention is also applicable to non-coplanar panels, ie panels that use only two electrodes that intersect to form one cell. Such a plasma panel is equivalent to FIG. 1 minus all of the sustain electrodes. For such plasma panels in which the line electrodes are grouped, for example, into two packets, one of which receives the maximum number of sustain signals and the other receives two out of five signals, the maximum brightness For example, the line is 30 cd/m2, and the minimum brightness is about 12 cd/m2. However, in the case of these panels with two electrodes per cell, the linear adjustment of brightness interferes with the addressing function, unlike in the case of coplanar panels. If this addressing function is provided by the same type of electrode from which the sustain edge is removed, adjustment of the sustain signal must necessarily take place outside the address cycle. In practice, the address cycle represents a large portion of the frame time; for example, for a 480 line screen refreshed every 20 ms, the addressing will be approximately 480 x 20 μs/line, or 9.6 ms, which is a fraction of the total time. That's 48%. As a result, the possibilities for adjusting the sustain signal are relatively limited. This constraint can be removed by intervening sustain cycles of limited duration between address stages.

FIGS. 4(a), 4(b) and 4(c) show such an arrangement which is particularly suitable for the case of another plasma panel in which one cell is formed by two intersecting electrodes. FIG. 4(a) shows the address signal SX applied to the column electrode, and FIG. 4(b) shows the address signal SX applied to the column electrode.
denotes an address signal and a sustain signal applied to the line electrode corresponding to the line Li having maximum brightness. Figure 4(c)
) indicates the address and sustain signals applied to the line electrodes of the next line Li+1 whose brightness needs to be reduced. In these signals applied to each of these lines,
There is an address phase PA between which there is a maintenance phase PE.

As before, each address phase has a basic erase square wave CBe in the erase cycle CE, followed by a write cycle CI with a basic write square wave CBi. The width of address phases PA1 and PA2 is about 20 μs, and 48
In the 0 line panel, the time available for maintenance phase PE is 2
It is 1.6 μs. This allows at most four consecutive sustain cycles, each of which is smaller in width than the erase or write cycle CE, C1, thus allowing five brightness levels. In the case of a line Li (FIG. 4b), the first address phase PA1 is used for addressing that line and therefore, as before, first the erase pulse Ie
It is assumed that the write pulse Ii is superimposed on the erase square wave CBe, and then the write pulse Ii is superimposed on the basic write square wave CBi. Following the first address phase PA1, four sustain cycles CS1-CS4 occur for the line Li. Next, the maintenance phase PE1
is followed by a second address phase PA2, and so on.

In the example of FIG. 4(c), the line Li+1 also passes through an address phase PA1, followed by a sustain phase PE1, followed by a second sustain phase PA2, etc., and the addressing of the line Li+1 is in this second address phase PA2. It will be held in According to the invention, the number of sustain cycles CS1-CS4 sent to reduce the brightness of line Li+1 is
less than the number sent about. This example can also be applied to multicolor plasma panels for electronic color balancing. The terms "line" and "column" with respect to electrodes do not indicate the horizontal or vertical orientation of the electrodes, although horizontal rows of cells are commonly referred to as "lines."

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of an AC plasma display panel to which the method of the present invention can be applied.

FIG. 2 is a diagram showing the operation of a coplanar plasma display panel according to the method of the present invention.

FIG. 3 shows the possibilities according to the invention.

FIG. 4 is a diagram showing the application of the method of the invention to the control of a plasma panel in which one cell is defined by two intersecting electrodes.

[Explanation of symbols]

X1-X4 Column electrodes P1-P9 Sustain electrode pair E1-E9 Sustain electrodes Y1-Y9 Address-sustain electrode 1 Display panel 3 Line address device (register) 4 Pulse generator 5 Column address device (register) 12 Control device I1, I2 Switch T1-T9 Transistor L1-L9 Line C1-C36 Cell SE Maintain signal

Claims (10)

[Claims] 1. A method for controlling an AC plasma display panel having a plurality of cells arranged in lines and columns, comprising the steps of setting up the "write" or "erase" states of the cells by commands. applying a sustain signal to the cells to activate the cells in the "write"state; and inhibiting transmission of one or more maintenance signals. 2. A method as claimed in claim 1, comprising the step of inhibiting the transmission of said sustaining signal on several lines or line packets so as to constitute zones with different brightness values. 3. The method of claim 2, further comprising the step of inhibiting the transmission of said signals simultaneously onto several lines and separately between at least two lines. 4. The method of claim 1, further comprising the step of inhibiting transmission of said sustain signal in the same manner for all lines of said panel. 5. The method of claim 1, wherein the plasma panel is of a coplanar sustain type having address sustain electrodes and sustain electrodes, and the plasma panel is operable to transmit the sustain signal applied to the address sustain electrodes. 6. The method of claim 1, wherein the plasma panel is of a coplanar sustain type including a column electrode intersecting an address-sustain electrode and a sustain electrode, and the plasma panel affects the transmission of the sustain signal applied to the sustain electrode. . 7. The method of claim 6, wherein at least one line has low brightness and only one address-sustain electrode intersecting the column electrode is formed in that line. 8. Claim 6, wherein at least one switch element is arranged in series with the sustain signal source of at least one sustain electrode.
Method described. 9. The method of claim 1, wherein the plasma panel is of a type having two electrodes that intersect to define one cell. 10. The plasma panel is of a multicolor type, and includes cells having at least two different colors, and each line of these cells is formed of cells of the same color. 9. The method according to any one of 9.