This invention relates to a plasma display (PDP) apparatus, a driving method and a driving IC for the PDP apparatus.
Recently, AC type PDP apparatuses have been rapidly popularized since they are not only thin in structure but also can provide screens greater in size than the conventional TV receivers using cathode ray picture tubes. However, they have disadvantages, too. The large screen needs large power consumption and high production cost.
In the display panel of the AC type PDP apparatus, the X electrodes and the Y electrodes are disposed alternately and in nearly parallel to one another, and the address electrodes (hereafter referred to as A electrodes) are arranged at right angle with respect to the X and Y electrodes to form a two-dimensional matrix.
During the reset period in
During the address period, Vscb+Vsc (circuit for applying this potential is not shown) is then applied to the Y electrode, and the address potential Va is applied to the A electrode of the display cell to be lit. Electric discharge takes place between the Y and A electrodes so that wall charges are formed in the desired display cell.
During the following sustain period, the sustain voltages +Vs and −Vs are alternately applied to the Y electrode, and the display cell in which wall charges were accumulated is lit every time the potential at the Y electrode is switched. At this time, the address electrode drive circuit 12 applies Va or 0 to the A electrode in response to +Vs or −Vs being applied to the Y electrode, respectively. To apply +Vs to the Y electrode, the Y electrode drive circuit 20 is used, and IGBT (T3) and IGBT (T4) are turned off and on, respectively. To apply −Vs to the Y electrode, on the other hand, T3 and T4 are turned on and off, respectively. Further, to apply Va to the A electrode, the address electrode drive circuit 12 causes MOSFET (T2) and MOSFET (T1) to be turned off and on, respectively, whereas to apply 0 volt to the A electrode, the address electrode drive circuit 12 causes MOSFET (T2) and MOSFET (T1) to be turned on and off, respectively. Diodes D1, D2, D3, D4 serve to clamp the potential at the A electrode to the power source voltage Va or the ground potential, or the potential at the Y electrode at +Vs or −Vs.
If, however, such a drive sequence as shown in
The objects of this invention, which has been made to eliminate the above mentioned drawback and to solve the above mentioned problems, are to stabilize the power source voltage Va during the sustain period; to suppress the electric discharge between the Y and A electrodes during the reset period, thereby preventing brightness deterioration and reducing power consumption; and to normally perform the positive sawtooth wave resetting between the Y and X electrodes, thereby preventing erroneous electric discharges and discharge failures, all these objects having not been able to be attained by conventional AC type PDP apparatuses with one-sided sustain drive circuits.
To attain the above mentioned objects, there is provided a plasma display apparatus comprising: a plurality of first electrodes; a plurality of second electrodes disposed approximately in parallel to the first electrodes and forming display cells together with the adjacent first electrodes, electric discharges taking place between the first and second electrodes forming the display cells; a plurality of third electrodes disposed in crisscross to the first and second electrodes; a plurality of first drive circuit boards for supplying current from a first power source to the third electrodes; a plurality of first switching elements located in the first drive circuit boards, for connecting the high-voltage terminals of the first power source with the third electrodes; and a plurality of second switching elements located in the first drive circuit boards, for connecting the low-voltage terminals of the first power source with the third electrodes,
wherein during the period for which the lighting of the plasma display panel is sustained, the first electrodes are maintained at a first fixed potential; the second electrodes (Y) are supplied alternately with a first voltage positive with respect to the potential of the first electrodes and a second voltage negative with respect to the potential of the first electrodes; and the potentials at the third electrodes vary in approximate synchronization with the waveforms of the voltages of the second electrodes; and wherein a means is provided that feeds at least part of power flowing toward the first power source from the third electrodes, into a second power source having a second voltage different from the voltage of the first power source.
Also, to attain the above mentioned objects, there is provided a plasma display apparatus comprising: a plurality of first electrodes; a plurality of second electrodes disposed approximately in parallel to the first electrodes and forming display cells together with the adjacent first electrodes, electric discharges taking place between the first and second electrodes forming the display cells; a plurality of third electrodes disposed in crisscross to the first and second electrodes; a plurality of first drive circuit boards for supplying current from a first power source to the third electrodes; a plurality of first switching elements located in the first drive circuit boards, for connecting the high-voltage terminals of the first power source with the third electrodes; and a plurality of second switching elements located in the first drive circuit boards, for connecting the low-voltage terminals of the first power source with the third electrodes,
wherein during the period for which the lighting of the plasma display panel is sustained, the first electrodes are maintained at a first fixed potential; the second electrodes are supplied alternately with a first voltage positive with respect to the potential of the first electrodes and a second voltage negative with respect to the potential of the first electrodes; and the breakdown voltage of the second switching elements is higher than that of the first switching elements.
Further, to attain the above mentioned objects, there is provided a plasma display apparatus comprising: a plurality of first electrodes; a plurality of second electrodes disposed approximately in parallel to the first electrodes and forming display cells together with the adjacent first electrodes, electric discharges taking place between the first and second electrodes forming the display cells; a plurality of third electrodes disposed in crisscross to the first and second electrodes; a plurality of first drive circuit boards for supplying current from a first power source to the third electrodes; a plurality of first switching elements located in the first drive circuit boards, for connecting the high-voltage terminals of the first power source with the third electrodes; and a plurality of second switching elements located in the first drive circuit boards, for connecting the low-voltage terminals of the first power source with the third electrodes,
wherein during the period for which the lighting of the plasma display panel is sustained, the first electrodes are maintained at a first fixed potential; the second electrodes are supplied alternately with a first voltage positive with respect to the potential of the first electrodes and a second voltage negative with respect to the potential of the first electrodes; and at least the second switching elements are IGBTs (Insulated Gate Bipolar Transistors).
Still further, to attain the above mentioned objects, there is provided a plasma display apparatus comprising: a plurality of first electrodes; a plurality of second electrodes disposed approximately in parallel to the first electrodes and forming display cells together with the adjacent first electrodes, electric discharges taking place between the first and second electrodes forming the display cells; a plurality of third electrodes disposed in crisscross to the first and second electrodes; a plurality of first drive circuit boards for supplying current from a first power source to the third electrodes; a plurality of first switching elements located in the first drive circuit boards, for connecting the high-voltage terminals of the first power source with the third electrodes; and a plurality of second switching elements located in the first drive circuit boards, for connecting the low-voltage terminals of the first power source with the third electrodes,
wherein during the period for which the lighting of the plasma display panel is sustained, the first electrodes are maintained at a first fixed potential; the second electrodes are supplied alternately with a first voltage positive with respect to the potential of the first electrodes and a second voltage negative with respect to the potential of the first electrodes; and the maximum voltage applied to the third electrodes during the reset period is higher than the maximum voltage applied to the third electrodes at the time of addressing during the address period.
Moreover, to attain the above mentioned objects, there is provided a method for driving the plasma display apparatus mentioned above.
Furthermore, to attain the above mentioned objects, there is provided an IC for driving the plasma display apparatus mentioned above.
By providing a means for feeding the power flowing from the Y electrodes to the A electrodes during the sustain period, into a separate power source having a voltage different from the voltage of the power source Va, several advantages can be obtained as folllows. Namely, the potential at the power source Va is stabilized, the formation of wall charges due to Va during the address period is made uniform, and unevenness in brightness is eliminated. Moreover, by effectively reusing the power retrieved into the separate power sources, it is possible to reduce the power consumption in the PDP apparatus. Furthermore, by making the maximum voltage applied to the A electrodes during the reset period, higher than the maximum voltage applied to the A electrodes during the address period, the electric discharges taking place between the Y and A electrodes during the reset period are suppressed so that positive sawtooth wave resetting can be normally performed between the Y and X electrodes and that erroneous discharges or discharge failures during the sustain period can be prevented. Additionally, by suppressing electric discharges between the Y and A electrodes, deterioration of brightness is lessened so that the lifetime of the PDP apparatus can be prolonged.
According to this invention, the potential Va of the address power source, i.e. first power source, can be stabilized, the unevenness of wall charges formed in the display cells during the address period can be lessened, and overall display can be uniform and stabilized. Also, since Vas can be set high, the deterioration of brightness can be lessened, the lifetime of the PDP apparatus can be prolonged, and power consumption by the PDP apparatus can be reduced. Additionally, since Var can be set high at the time of positive sawtooth wave resetting during the reset period, electric discharges between the Y and A electrodes become hard to take place and the positive sawtooth wave resetting between the desired Y and X electrodes can be performed normally. Accordingly, it becomes possible to provide a plasma display apparatus free from erroneous electric discharges and failures in electric discharge, a method and an IC for driving such a plasma display apparatus.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with accompanying drawings.
Embodiments of this invention will now be described in detail with reference to the attached drawings.
During the reset period, a voltage Vset is gradually superposed on the voltage +Vs which has been already applied to the Y electrode for positive sawtooth wave resetting. At this time, the transistors T1, T2 of the address electrode drive circuit 10 are both turned off. With increasing potential at the Y electrode, the potential Var at the A electrode increases as a result of displacement current flowing between the Y and A electrodes so that the potential Var at the A electrode is clamped at a voltage Vac through the diodes D1, D6. Or, alternatively, the potential Var is kept at a voltage somewhere between Vac and Va. Then, when the potentials +Vs and Vset are removed from the Y electrode, the potential Var at the A electrode during the reset period is clamped to the ground potential via the diode D2.
In the address period that follows, a voltage Vsc, which is supplied from a scanning IC (not shown in
In the sustain period reached finally, voltages +Vs and −Vs are alternately applied to the Y electrode, electric discharge takes place between the Y electrode and the associated X electrode, and the associated display cell emits light. At this time, the transistors T1 and T2 of the address electrode drive circuit 10 are both turned off. Accordingly, +Vs is applied to the Y electrode and when the electric discharge takes place, the potential Vas at the A electrode during the sustain period is clamped via the diodes D1, D6 at Vac in the drive circuit 10 shown in
The configuration proposed according to this invention and described above has three principal advantages.
The first advantage is as follows. Power flowing into the A electrode during the sustain period can be transferred to the power source Vac other than the power source Va so that the power source Va to be used during the address period can be stabilized. As a result, the unevenness of wall charges formed in the display cells during the address period is lessened, contributing to the advantage that uniform and stabilized display can be obtained. Power consumption can be effective if the power transferred to the power source Vac can be utilized to energize, for example, other ICs in the PDP apparatus.
The power that can be retrieved and reused according to this embodiment of the invention, caused the instability of the power source voltage Va, the uneven brightness and the erroneous discharges in the conventional configuration shown in
The second advantage is as follows. If Vas is set high, the deterioration of brightness is lessened and the lifetime of the plasma panel becomes longer.
The third advantage is as follows. If the A electrode potential Var during the reset period is set higher than the A electrode potential Va during the address period, the electric discharge between the Y and A electrodes is suppressed at the time of positive sawtooth wave resetting during the reset period so that the desired positive sawtooth wave resetting can be performed normally. Accordingly, along with the ensuing negative sawtooth wave resetting, the wall charges of respective display cells can be eliminated or lessened so that the respective display cells can be uniformly initialized. Thus, wall charges are stably formed in the respective display cells during the address period and, as a result, errors and failures in electric discharge during the sustain period can be prevented.
In order to control the driving waveform in such a manner as shown in
If Vac is allowed to be a potential equal to Vs (about 170 V), the breakdown voltage of the switching element T2 must be higher than 200 V. On the other hand, if Va is set at 70 V, the breakdown voltage of T1 can be about 100 V. It is to be noted that the breakdown voltages of D1 and D2 must also be equal to those of T1 and T2, respectively. Further, it is needless to say that D5 and D6 must have withstand voltages not less than the voltage difference between Vac and Va (i.e. 100 V=170 V−70 V).
Even in the case of a drive IC wherein a plurality of address electrode drive circuits 10 are integrated, the concept of the above described embodiment can be well implemented. Such an IC configuration enables each address electrode drive circuit 10 to be miniaturized.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
Number | Date | Country | Kind |
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2007-335519 | Dec 2007 | JP | national |