The present invention relates to a plasma display device. To be more precise, preferred embodiments of the present invention provide a plasma display device, in which a brightness difference caused in a plasma display panel of a large screen is reduced.
In a conventional plasma display device, an inputted video signal is processed in a signal processing circuit 1, and is supplied to a drive control circuit 2 as shown in
In the plasma display device including a large screen of the large-sized plasma display panel 7, it is important to make the brightness of the entire screen uniform so that nonuniformity in brightness does not occur on the screen.
Patent Document 1 discloses a method for reducing a brightness difference by dividing X-electrodes and Y-electrodes into a plurality of blocks and causing the border portions between the blocks to intersect one another.
In
When a pattern shown in
The brightness difference will be called a streaking. A streaking is defined by the following formula.
Streaking=(brightness S1-brightness S2)/brightness S1×100 (%)
The conventional plasma display device has the problem that the value of the above described streaking is large, and it is an important object for improving the image quality to reduce the value of the streaking. In the conventional plasma display device having a large value of a streaking, a voltage drop occurs in the sustain voltage waveform shown in
Further, the conventional plasma display device has the problem of occurrence of a difference in brightness between the two end portions and the central portion of the plasma display panel screen. The reason of the occurrence of the bright difference will be described by using
I1=5*I
I2=4*I
I3=3*I
I4=2*1
I5=I
I6=I
I7=2*I
I8=3*I
I9=4*I
I10=5*I
When resistances Rp between the cells are assumed to be equal and a trial calculation is made, a voltage Vsy of the Y-electrode and a voltage Vsx of the X-electrode in each of cells A to E are expressed as follows:
VAy=Vs
VBy=VAy−Rp*I2=Vs−4RpI
VCy=VBy−Rp*I3=Vs−7RpI
VDy=VCy−Rp*I4=Vs−9RpI
VEy=VDy−Rp*I5=Vs−10RpI
VEx=0
VDx=VEx+Rp*I9=4RpI
VCx=VDx+Rp*I8=7RpI
VBx=VCx+Rp*I7=9RpI
VAx=VAx+Rp*I6=10RpI
From the above, when Vd=10RpI, the difference (Vsy-Vsx) of the voltage Vsy of the Y-electrode and the voltage Vsx of the X-electrode in the cells A to E can be expressed as follows:
VAy−VAx=Vs−10RpI=Vs−Vd
VBy−VBx=Vs−13RpI
VCy−VCx=Vs−14RpI
VDy−VDx=Vs−13RpI
VEy−VEx=Vs−10RpI=Vs−Vd
When the relationship is plotted in a graph, the graph is as shown in
As the conventional example in which the brightness difference on the screen is reduced, the method disclosed in the above described Patent Document 1 is cited, but the above described conventional example has an object to reduce the brightness difference between the lines, and does not have consideration to a solution to the two problems of the above described streaking, and the above described bright difference between the central portion and the two end portions of the screen.
An object of the present invention is to reduce a value of the above described streaking as well as a brightness difference between the central portion and the two end portions of the screen.
In order to attain the above described object, a plasma display device of the present invention has the most main characteristic that current limiting means 8x and 8y is interposed for each X-electrode between the X-electrode and an X-electrode drive circuit 3, and current limiting means 8x and 8y is interposed for each Y-electrode between the Y-electrode and the Y-electrode drive circuit 4.
According to the present invention, a value of a streaking can be reduced, and a brightness difference between the central portion and the two end portions of the screen can be reduced.
1 Signal processing circuit
2 Drive control circuit
3 X-electrode drive circuit
4 Y-electrode drive circuit
5 Address electrode drive circuit
6 Scan circuit
7 Plasma display panel
8 Current limiting means
9 Scan drive module (SDM)
10 X-electrode relay board (X-BB)
Hereinafter, embodiments of the present invention will be described by using the drawings.
In the circuit shown in
By using the above described current limiting means 8x and 8y, the peak value of a sustain current which is passed in a sustain period is reduced, and the voltage drop of a sustain voltage can be reduced.
The result is shown in
As a result of the experiment, it was confirmed that in the case of using the large-sized plasma display panel 7 of the 55-model class, by setting the value of the resistance of the above described current limiting means 8x and 8y at 10 to 20 106 , the value of a streaking of about 8% was reduced to about 4%, and the improvement effect by about 4% was confirmed.
The resistance of each of the X-electrode and Y-electrode in the above described plasma display panel 7 is about 50 Ω, and therefore, the resistance value which is used as the above described current limiting means 8x and 8y corresponds to 20% to 40% of the resistance value of each of the X-electrode and Y-electrode.
As the above described current limiting means 8x and 8y, any means that limit the current such as a semiconductor can be replaced with the resistor, and for example, a diode or the like may be used. The diode for limiting a current may be formed inside the plasma display panel 7.
By using the above described current limiting means 8x and 8y, the voltage drop in the central portion of the screen which is caused by the above described sustain current can be reduced. As shown in
In this embodiment, the case of using the resistors having the same value as the current limiting means 8x and 8y is described, but the invention of the present application is not limited to this, and it is obvious that in the case of using the resistors having different values, the effect of reducing a streaking can also be obtained.
Considering the balance of disposition relationship of the current routes to the X-electrode and the Y-electrode of the plasma display panel 7 in the X-electrode drive circuit 3 and the Y-electrode drive circuit 4, in the case of providing the current limiting means 8x and 8y for each electrode, the current routes in the upper and the lower portions of the screen become longer as compared with the current route in the central portion of the screen, and therefore, the voltage drop of the sustain voltage in the upper and lower portions of the screen becomes large, as a result of which, a brightness difference is likely to occur between the upper and lower portions of the screen, and the central portion of the screen.
In this case, the current limit value of each of the current limiting means 8x and 8y is set at a different value in each of the electrode. For example, the current limit values of the current limiting means 8x and 8y are made smaller toward the upper and lower portions, and a difference in voltage drop in accordance with the difference in the length of the above described current route can be corrected.
Therefore, in the plasma display device of the present invention, the brightness difference between the central portion of the screen and the two ends of the screen is reduced, and the brightness difference between the upper and lower portions of the screen and the central portion of the screen can be reduced.
Hereinafter, configuration examples of the present invention are described in additions.
An AC-type plasma display device including a plasma display panel, an X-electrode drive circuit which drives a plurality of X-electrodes of the plasma display panel, a Y-electrode drive circuit which drives a plurality of Y-electrodes of the plasma display panel, and an address electrode drive circuit 5 which drives a plurality of address electrodes of the plasma display panel, characterized by including:
The AC-type plasma display device according to the addition 1, characterized in that the X-electrode drive circuit is divided into an odd-numbered X-electrode drive circuit which drives odd-numbered X-electrodes, and an even-numbered X-electrode drive circuit which drives even-numbered X-electrodes, and the Y-electrode drive circuit is divided into an odd-numbered Y-electrode drive circuit which drives odd-numbered Y-electrodes, and an even-numbered Y-electrode drive circuit which drives even-numbered Y-electrodes.
The plasma display device according to the additions and 2, characterized in that
The plasma display device according to the additions and 2, characterized in that
The plasma display device according to the addition 4, characterized in that
The plasma display device according to the addition 5, characterized in that
The plasma display device according to the additions to 3, characterized in that
The plasma display device according to the addition 7, characterized in that
The plasma display device according to the additions to 3, characterized in that
The plasma display device according to the additions to 3, characterized in that
The plasma display device according to the additions 1 to 10, characterized in that
The plasma display device according to the addition 3, characterized in that
The plasma display device according to the addition 11, characterized in that
The plasma display device according to the additions 4 and 5, characterized in that
The plasma display device according to the addition 14, characterized in that
The plasma display device according to the addition 9, characterized in that
The plasma display device according to the addition 10, characterized in that
The plasma display device according to the addition 2, characterized in that
The plasma display device according to the addition 2, characterized in that
The plasma display device according to the addition 19, characterized in that
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2005/014347 | 8/4/2005 | WO | 00 | 10/31/2007 |