Method for driving a display panel

1. Field of the Invention

The present invention relates to a method for driving a display panel.

2. Description of the Related Art

A display device having a plasma display panel mounted thereto as the display panel described above is described in JP-A-2000-155557, for example.

FIG. 1 shows a schematic construction of such a display device.

Referring to FIG. 1 , a PDP 1 as the plasma display panel includes row electrodes Y 1 to Yn and row electrodes X 1 to Xn corresponding to rows (first to nth rows) of one screen, whereby each X and each Y form a pair. Column electrodes D 1 to Dm are formed in such a fashion as to correspond columns (first to m-th columns) of one screen and to intersect these row electrodes. In this instance, a discharge cell as a capacitive light emitting device is formed at a point of intersection between one set of row electrode pair and one column electrode. An address driver 2 converts pixel data for each pixel based on an image signal to a pixel data pulse having a voltage value corresponding to a logic level of the pixel data and applies the pixel data pulse to the column electrodes D 1 to Dm for each row. An X-row electrode driver 3 generates a reset pulse for initializing a residual wall charge quantity of each discharge cell and a sustain discharge pulse for sustaining a discharge light emission state of each light-on mode discharge cell to be later described and applies these pulses to the row electrodes X 1 to Xn. A Y-row electrode driver 4 generates a reset pulse for initializing the residual wall charge quantity of each discharge cell and the sustain discharge pulse for sustaining the discharge light emission state of each light-on mode discharge cell and applies these pulses to the row electrodes Y 1 to Yn in the same way as the X-row electrode driver 3 . The Y-row electrode driver 4 further generates a priming pulse for re-forming charge particles generated inside the discharge cells and a scan pulse SP for causing each discharge cell to generate a quantity of charge corresponding to the pixel data pulse and for setting the light-on mode discharge cell or light-off mode discharge cells, and applies these pulses to the row electrodes Y 1 to Yn.

FIG. 2 shows an internal construction of the X-row electrode driver 3 and the Y-row electrode driver 4 . Incidentally, an electrode X 1 in FIG. 2 represents an electrode of a j-th row among the electrodes X 1 to Xn and an electrode Yj represents an electrode of a j-th row among the electrodes Y 1 to Yn.

The X-row electrode driver 3 includes two power sources B 1 and B 2 . The power source B 1 outputs a voltage Vs1 (for example, 170 V) and the power source B 2 outputs a voltage Vr1 (for example, 190 V). A positive terminal of the power source B 1 is connected to a connection line 11 for the electrode Xj through a switching device S 3 and its negative terminal is grounded. A switching device S 4 is interposed between the connection line 11 and the earth. In addition, a series circuit including a switching device S 1 , a diode D 1 and a coil L 1 and a series circuit including a coil L 2 , a diode D 2 and a switching device S 2 are interposed between the connection line 11 and the earth through a capacitor C 1 interposed on the earth side. Incidentally, the diode D 1 is connected with its anode positioned on the side of the capacitor C 1 and the diode D 2 , with its cathode positioned on the side of the capacitor C 1 . A positive terminal of the power source B 2 is connected to the connection line 11 through a switching device S 8 and a resistor R 1 and its negative terminal is grounded. The Y-row electrode driver 4 includes four power sources B 3 to B 6 . The power source B 3 outputs the voltage Vs1 (for example, 170 V) and the power source B 4 outputs the voltage Vr1 (for example, 190 V). The power source B 5 outputs a voltage Voff (for example, 140 V) and the power source B 6 outputs a voltage Vh (for example, 160 V, Vh>Voff). A positive terminal of the power source B 3 is connected to a connection line 12 for a switching device 15 through a switching device S 13 and its negative terminal is grounded. A switching device S 14 is interposed between the connection line 12 and the earth. In addition, a series circuit including a switching device S 11 , a diode D 3 and a coil L 4 and a series circuit including a coil L 4 , a diode D 4 and a switching device S 12 are interposed between the connection line 12 and the earth through a capacitor C 2 interposed on the earth side. Incidentally, the diode D 3 is connected with its anode positioned on the side of the capacitor C 2 and the diode D 4 , with its cathode positioned on the side of the capacitor C 2 . The connection line 12 is connected to a connection line 13 for a positive terminal of the power source B 6 through a switching device S 15 . A positive terminal of the power source B 4 is grounded and its negative terminal is connected to the connection line 13 through a switching device S 16 and a resistor R 2 . A positive terminal of the power source B 5 is connected to the connection line 13 through a switching device S 17 and is negative terminal is grounded. The connection line 13 is connected to a connection line 14 for the electrode Yj through a switching device S 21 . A negative terminal of the power source B 6 is connected to the connection line 14 through a switching device S 22 . A diode D 5 is interposed between the connection lines 13 and 14 and a series circuit of a switching device S 23 and a diode D 6 is interposed between these connection lines 13 and 14 , too. The diode D 5 is connected with its anode positioned on the side of the connection line 14 and the diode D 6 , with its cathode positioned on the side of the connection line 14 .

Here, a control circuit, not shown in the drawings, controls ON/OFF switching of the switching devices S 1 to S 4 , S 8 , S 11 to S 17 and S 21 to S 23 .

Incidentally, the power source B 3 , the switching devices S 11 to S 15 , the coil L 3 , the coil L 4 , the diode D 3 , the diode D 4 and the capacitor C 2 constitute a sustain driver portion inside the Y-row electrode driver 4 . The power source B 4 , the resistor R 2 and the switching device S 16 constitute a reset driver portion. The power source B 5 , the power source B 6 , the switching device S 13 , the switching device S 17 , the switching device S 21 , the switching device S 22 , diode D 5 and D 6 constitute a scan driver portion.

Next, operations under such a construction will be explained with reference to the timing chart of FIG. 3 .

Driving of the PDP 1 is divided into a reset period, an address period and a sustain period as shown in FIG. 3 .

First, in the reset period, the switching device S 23 of the Y-row electrode driver 4 is turned ON. The switching device S 23 remains ON during the reset period and the sustain period. At the same time, the switching device S 8 of the X-row electrode driver 3 is turned ON and the switching device 16 of the Y-row electrode driver 4 is turned ON. Other switching devices are OFF. As the switching device S 8 is turned ON, current flows from the positive terminal of the power source B 2 into the electrode Xj through the switching device S 8 and the resistor R 1 . As the switching device S 16 is turned ON, current flows from the electrode Yj into the negative terminal of the power source B 4 through the diode D 5 , the resistor R 2 and the switching device S 16 . In this instance, the potential of the electrode Xj gradually rises depending on the time constant of the load capacitance C 0 of the PDP 1 and the resistor R 1 and a reset pulse RPx shown in FIG. 3 is generated. On the other hand, the potential of the electrode Yj gradually decrease depending on the time constant of the load capacitance C 0 and the resistor R 2 and a reset pulse RPy shown in FIG. 3 is generated. The reset pulse RPx is simultaneously applied to all the electrodes X 1 to Xn and the reset pulse RPy is simultaneously applied to all the electrodes Y 1 to Yn. Because of the simultaneous application of these reset pulses RPx and RPy, reset discharge is induced inside all the discharge cells of the PDP 1 and after this discharge finishes, wall charge of a predetermined quantity is uniformly formed in the dielectric layer of all the discharge cells. The switching devices S 8 and S 16 are turned OFF after the levels of the reset pulses RPx and RPy get into saturation but before the end of the reset period. At this point, the switching devices S 4 , S 14 and S 15 are turned ON and both of the electrodes Xj and Yj are grounded. Consequently, the reset pulses RPx and RPy disappear.

Next, in the address period, the switching devices S 14 and S 15 are turned OFF, the switching device S 23 is turned OFF, the switching device S 17 is turned ON and at the same time, the switching device S 22 is turned ON. As the switching device S 17 is turned ON, the power source B 5 and the power source B 6 enter a series connection state and a negative potential representing the difference between the voltages Vh and Voff occurs at the negative terminal of the power source B 6 and is applied to the electrode Yj. In this address period, the address driver 2 converts pixel data for each pixel based on the image signal to each pixel data pulse DP 1 to DPn having a voltage value corresponding to the logic level of the pixel data and serially applies it to the column electrodes D 1 to Dm for each row. As shown in FIG. 3 , the pixel data pulses DPj and DPj+1 are applied to the electrodes Yj and Yj+1. In the mean time, the Y-row electrode driver 4 serially applies the priming pulse PP of the positive voltage to the row electrodes Y 1 to Yn and serially applies the scan pulse SP of the negative voltage in synchronism with the timing of the group of the pixel data pulses DP 1 to DPn immediately after the application of each priming pulse PP. The explanation will be given on the electrode Yj. When the priming pulse PP is generated, the switching device S 21 is turned ON and the switching device S 22 is turned OFF. The switching device S 17 remains OFF. Consequently, the potential Voff of the positive terminal of the power source B 5 is applied as the priming pulse PP to the electrode Yj through the switching device S 17 and then through the switching device S 21 . After the priming pulse PP is applied, the switching device S 21 is turned OFF in synchronism with the application of the pixel data pulse DPj from the address driver 2 and the switching device S 22 is turned ON. Accordingly, the negative potential representing the difference between the voltage Vh of the negative terminal of the power source B 6 and Voff is applied as the scan pulse SP to the electrode Yj. The switching device S 21 is turned ON in synchronism with the stop of the application of the pixel data pulse DPj from the address driver 2 , the switching device S 22 is turned OFF and the potential Voff of the positive terminal of the power source B 5 is applied to the electrode Yj through the switching device S 17 and then through the switching device S 21 . As for the electrode Yj+1, too, the priming pulse PP is thereafter applied in the same way as the electrode Yj and the scan pulse SP is applied in synchronism with the application of the pixel data pulse DPj+1 from the address driver 2 . Among the discharge cells belonging to the row electrodes to which the scan pulse SP is applied, discharge occurs inside those discharge cells to which the pixel data pulse of the positive voltage is further applied simultaneously, and the majority of their wall discharge is lost. On the other hand, discharge does not occur in the discharge cells to which the scan pulse SP is applied but the pixel data pulse of the positive voltage is not applied and the wall charge remains as such. In this instance, the discharge cells in which the wall charge remains are light-on mode discharge cells and the discharge cells in which the wall charge disappears are light-off mode discharge cells. In the shift from the address period to the sustain period, the switching devices S 17 and S 21 are turned OFF. Instead, the switching devices S 14 and S 15 are turned ON. The ON state of the switching device S 4 is kept.

Next, in the sustain period, the potential of the electrode Xj reaches the earth potential of about 0 V as the switching device S 4 of the X-row electrode driver 3 is turned ON. Next, when the switching device S 4 is turned OFF and the switching device S 1 is turned ON, current reaches the electrode Xj due to the charge stored in the capacitor C 1 through the coil L 1 , the diode D 1 and the switching device S 1 and charges the load capacitance C 0 of the PDP 1 . At this time, the potential of the electrode Xj gradually rises depending on the time constant of the coil L 1 and the load capacitance C 0 . Next, the switching device S 1 is turned OFF and the switching device S 3 is turned ON. Consequently, the potential Vs1 of the positive terminal of the power source B 1 is applied to the electrode Xj. The switching device S 3 is thereafter turned OFF, the switching device S 2 is turned ON and the current flows from the electrode Xj into the capacitor C 1 due to the charge stored in the load capacitance C 0 through the coil L 2 , the diode D 2 and the switching device S 2 . At this time, the potential of the electrode j gradually decrease depending on the time constant of the coil L 2 and the capacitor C 1 as shown in FIG. 3 . When the potential of the electrode Xj substantially reaches 0 V, the switching device S 2 is turned OFF and the switching device S 4 is turned ON. Due to such an operation, the X-row electrode driver 3 applies the sustain discharge pulse IPx of the positive voltage shown in FIG. 3 to the electrode Xj. At the ON time of the switching device S 4 at which the sustain discharge pulse IPx disappears, the switching device S 11 is simultaneously turned ON and the switching device S 14 is turned OFF in the Y-row electrode driver 4 . When the switching device S 14 remains OFF, the potential of the electrode Yj is at the earth potential of about 0 V but when the switching device S 14 is turned OFF and the switching device S 11 is turned ON, the current reaches the electrode Yj due to the charge stored in the capacitor C 2 through the coil L 3 , the diode D 3 , the switching device S 11 , the switching device S 15 , the switching device S 13 and the diode D 6 and charges the load capacitance C 0 of the PDP 1 . At this time, the potential of the electrode Yj gradually rises as shown in FIG. 3 depending on the time constant of the coil L 3 and the load capacitance C 0 . Next, the switching device S 11 is turned OFF and the switching device S 13 is turned ON. Consequently, the potential VS1 of the positive terminal of the power source B 3 is applied to the electrode Yj. Thereafter the switching device S 13 is turned OFF, the switching device S 12 is turned ON and the current flows from the electrode Yj into the capacitor C 2 due to the charge stored in the load capacitance C 0 through the diode D 5 , the switching device S 15 , the coil L 4 , the diode D 4 and the switching device S 12 . At this time, the potential of the electrode Yj gradually decrease depending on the time constant of the coil L 4 and the capacitor C 2 as shown in FIG. 3 . When the potential of the electrode Yj substantially reaches 0 V, the switching device S 12 is turned OFF and the switching device S 14 is turned ON. Due to such an operation, the Y-row electrode driver 4 applies the sustain discharge pulse IPy of the positive voltage shown in FIG. 3 to the electrode Yj.

Whenever the sustain discharge pulses IPx and IPy are applied in this way to the electrodes X 1 to Xn and to the electrodes Y 1 to Yn during the sustain period, the light-on mode discharge cells in which the wall charge remains repeat discharge light emission and keep the light emission state.

In driving shown in FIG. 3 , however, the voltages of all the row electrodes Y sharply shift all at once to 0 V during the shift from the address period to the sustain period and noise occurs. In this instance, a large current resulting from such a noise flows in some cases into the driver IC and may invite the drop of IC's life.

The invention is completed to solve such problems and aims at providing a driving method of a display panel capable of improving durability of a driving device for driving the display panel.

The invention provides a method for driving a display panel having discharge cells arranged at points of intersection between a plurality of row electrode pairs corresponding to display lines and a plurality of column electrodes so arranged as to intersect the row electrode pairs, for each of a plurality of sub-fields constituting each field of an image signal, wherein each of the sub-fields includes an address period in which a scan pulse is applied in superposition with a base pulse to one of the row electrodes of one of the row electrode pairs while the base pulse is applied to one of the row electrodes of all of the row electrode pairs, and the discharge cells are selectively caused to discharge and are set to either one of a light-on mode and a light-off mode by applying a pixel data pulse corresponding to the image signal at the same application time as that of the scan pulse, and a sustain period in which a sustain pulse is applied the number of times corresponding to weighting of the sub-field to the row electrode pairs so that only the discharge cells set to the light-on mode are allowed to repeatedly cause sustain discharge; and a change ratio of a voltage value in a fall period of the voltage value in the base pulse is smaller than a change value of a voltage value in a fall period in the scan pulse.

FIG. 1 shows a schematic construction of a plasma display device;

FIG. 2 shows an internal construction of an X-row electrode driver 3 and a Y-row electrode driver 4 of the plasma display device shown in FIG. 1 ;

FIG. 3 is a time chart showing the operations of the X-row electrode driver 3 and the Y-row electrode driver 4 ;

FIG. 4 shows a schematic construction of a plasma display device for driving a plasma display panel in accordance with a method for driving a display panel of the invention;

FIG. 5 shows a schematic driving format by a sub-field method;

FIG. 6 shows the internal constructions of the X-row electrode driver 30 and the Y-row electrode driver 40 of the plasma display panel shown in FIG. 4 ; and

FIG. 7 is a time chart showing the operation of each of an X-row electrode driver 30 and a Y-row electrode driver 40 .

Preferred embodiments of the invention will be hereinafter explained in detail with reference to the accompanying drawings.

FIG. 4 shows a schematic construction of a plasma display device having a plasma display panel mounted thereto as a display panel.

Referring to FIG. 4 , a PDP 10 as the plasma display panel includes row electrodes Y 1 to Y n and X 1 to X n each forming a row electrode pair by the X and Y electrodes in such a fashion as to correspond to each of the first to n-th display lines of each screen. The PDP 10 further includes column electrodes D 1 to D m formed in such a fashion as to intersect to the row electrode pairs and to correspond to the first to m-th columns of one screen. A dielectric layer and a discharge space are formed between these row electrode group (Y 1 to Y n , X 1 to X n ) and column electrode group (D 1 to D m ). A discharge cell is formed, as a capacitive light emitting device, at the intersection of a pair of row electrode pair (X, Y) and a column electrode D.

A driving control circuit 50 converts an inputted image signal to pixel data for each pixel, divides this pixel data into bit digits corresponding to bits and acquires pixel data bits. The driving control circuit 50 supplies the pixel data bits for each display line (m bits) in the same bit digit to an address driver 20 . To drive the PDP 10 in accordance with a light emission driving format based on a sub-field method shown in FIG. 5 , the driving control circuit 50 further supplies various switching signals SW (to be later described) to the X-row electrode driver 30 and to the Y-row electrode driver 40 . Incidentally, the sub-field method divides each field in the image signal into N sub-fields SF1 to SF(N) as shown in FIG. 5 , causes light emission driving of each pixel for each sub-field for a period corresponding to weighting of each sub-field and expresses intermediate luminance.

Incidentally, the term “field” used hereby takes the image signal of an interlace system such as an NTSC system into consideration and corresponds to a frame in the image signal of a non-interlace system.

FIG. 6 shows an internal construction of each of the X-row and Y-row electrode drivers 30 and 40 .

As shown in FIG. 6 , a capacitor C 1 in the X-row electrode driver 30 is grounded to a PDP ground potential as a ground potential of the PDP 10 at one of its electrode terminals. A switching device S 1 remains OFF while a switching signal SW 1 having a logic level 0 is supplied from the driving control circuit 50 . The switching device S 1 is turned ON when the switching signal SW 1 is at a logic level 1 and applies a voltage occurring at the other electrode terminal of the capacitor C 1 to the row electrode X of the PDP 10 through a coil L 1 and a diode D 1 . A switching device S 2 remains OFF while a switching signal SW 2 of the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 2 is turned ON when the switching signal SW 2 is at the logic level 1 and supplies the voltage of the row electrode X to the other electrode terminal of the capacitor C 1 through a coil L 2 and a diode D 2 . The capacitor C 1 is charged in this instance. A switching device S 3 remains OFF while a switching signal SW 3 having the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 3 is turned ON when the switching signal SW 3 is at the logic level 1 and applies a voltage Vs generated by a power source B 1 to the row electrode X. Incidentally, the voltage Vs is a pulse voltage of a sustain discharge pulse IPx to be later described. In other words, the power source B 1 is the one that generates the voltage Vs as a pulse voltage value of the sustain discharge pulse IPx. A switching device S 4 remains OFF while a switching signal SW 4 of the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 4 is turned ON when the switching signal SW 4 is at the logic level 1 and sets the row electrode X to the PDP ground potential.

The X-row electrode driver 30 further has a reset driver portion RSDx including a power source B 7 , a switching device S 5 , a capacitor C 4 and resistors R 41 and R 42 .

One of the electrode terminals of each of the resistors R 41 and R 42 in the reset driver portion RSDx is connected to the row electrode X. The other electrode terminal of the resistor R 41 is connected to one of the electrode terminals of the capacitor C 4 and the other electrode terminal of this capacitor C 4 is connected to the other electrode terminal of the resistor R 42 . In other words, a series circuit of the resistor R 41 and the capacitor C 4 is connected in parallel with both terminals of the resistor R 42 . Incidentally, the resistor R 42 has a higher resistance than the resistor R 41 . A switching device S 5 remains OFF while a switching signal SW 5 is at the logic level 0. On the other hand, the switching device S 5 is turned ON when the switching signal SW 5 is at the logic level 1 and applies a voltage (−Vr) of a power source B 7 to the row electrode X through a circuit including the capacitor C 4 and the resistors R 41 and R 42 .

The Y-row electrode driver 40 includes a sustain driver portion SUD, a reset driver portion RSD y and a scan driver portion SCD as shown in FIG. 6 .

A capacitor C 2 in the sustain driver portion SUD is grounded to the PDP ground potential as the ground potential of the PDP 10 at one of its electrode terminals. A switching device S 11 remains OFF while a switching signal SW 11 having the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 11 is turned ON when the switching signal SW 11 is at the logic level 1 and applies a voltage occurring at the other electrode terminal of the capacitor C 2 to a connection line 12 through a coil L 3 and a diode D 3 . A switching device S 12 remains OFF while a switching signal SW 12 of the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 12 is turned ON when the switching signal SW 12 is at the logic level 1 and applies the voltage of the connection line 12 to the other electrode terminal of the capacitor C 2 through the coil L 4 and the diode D 4 . The capacitor C 2 is charged in this instance by the voltage applied to the connection line 12 . A switching device S 13 remains OFF while a switching signal SW 13 of the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 13 is turned ON when the switching signal SW 13 is at the logic level 1 and applies the voltage Vs generated by a power source B 3 to the connection line 12 . Incidentally, the voltage Vs is a pulse voltage of a sustain discharge pulse IPy to be later described. In other words, the power source B 1 is the one that generates the voltage Vs as a pulse voltage value of the sustain discharge pulse IPy. A switching device S 14 remains OFF while a switching signal SW 14 of the logic level 0 is supplied from the driving control circuit 50 . On the other hand, the switching device S 14 is turned ON when the switching signal SW 14 is at the logic level 1 and sets the connection line 12 to the PDP ground potential. A switching device S 15 is turned ON only when a switching signal SW 15 supplied from the driving control circuit 50 is at the logic level 1, and connects the connection line 12 to a connection line 13 .

One of the electrode terminals of each of the resistors R 11 and R 12 in the reset driver portion RSDy is connected to the connection line 13 . The other electrode terminal of the resistor R 12 is connected to one of the electrode terminals of the capacitor C 11 and the other electrode terminal of this capacitor C 11 is connected to the other electrode terminal of the resistor R 11 . In other words, a series circuit of the resistor R 12 and the capacitor C 11 is connected in parallel with both terminals of the resistor R 11 . Incidentally, the resistor R 11 has a higher resistance than the resistor R 12 . A switching device S 17 remains OFF while a switching signal SW 17 is at the logic level 0. On the other hand, the switching device S 17 is turned ON when the switching signal SW 17 is at the logic level 1 and applies a voltage Vs of a positive terminal of the power source B 3 to the connection line 13 through a circuit including the capacitor C 11 , the resistors R 11 and R 12 . A switching device S 18 remains OFF while a switching signal SW 18 is at the logic level 0. On the other hand, the switching device S 18 is turned ON when the switching signal SW 18 is at the logic level 1 and grounds the connection line 13 through a resistor R 2 and a diode D 7 .

Switching devices S 19 and S 20 in the scan driver portion SCD remain OFF while switching signals SW 19 and SW 20 of the logic level 0 are supplied from the driving control circuit 50 . On the other hand, the switching devices S 19 and S 20 are turned ON when both of the switching signals SW 19 and SW 20 are at the logic level 1 and apply a voltage (−V off ) of a negative terminal of a power source B 5 to the connection line 13 through a resistors R 3 . Incidentally, the voltage (−V off ) is a voltage bearing a pulse voltage value in a scanning pulse SP to be later described. A switching device S 21 remains ON while a switching signal SW 21 supplied from the driving control circuit 50 remains at the logic level 1, and connects the positive terminal of the power source B 6 to the row electrode Y. A switching device S 22 remains ON only while a switching signal SW 22 supplied from the driving control circuit 50 is at the logic level 1, and connects the negative terminal of the power source B 6 and the row electrode Y. Incidentally, the scan driver portion SCD is disposed for each of the row electrodes Y 1 to Y n of the PDP 10 . In other words, the switching devices S 21 and S 22 are individually connected to each of the row electrodes Y 1 to Y n . For example, the switching devices S 21 1 and S 22 1 are connected to the row electrode Y 1 , the switching devices S 21 2 and S 22 2 are connected to the row electrode Y 2 , and so on. Finally, the switching devices S 21 n and S 22 n are connected to the row electrode Y n .

Next, the operation in the construction described above will be explained with reference to the timing chart in FIG. 7 . Incidentally, FIG. 7 shows in extraction the operation inside one sub-field of each of the sub-fields shown in FIG. 5 .

First, in a reset period, the driving control circuit 50 sets the switching device S 17 in the reset driver portion RSD Y of the Y-row electrode driver 40 to ON and the switching device S 22 of the scan driver portion SCD to ON. Consequently, the voltage Vs of the power source B 3 in the sustain driver portion SUD is applied to the row electrode Y through the capacitor C 11 , the resistor R 12 , the connection line 13 and the switching device S 22 . In this instance, the load capacitance C 0 of the PDP 10 is charged and the voltage of the row electrode Y gradually rises from 0 V as shown in FIG. 7 . When the voltage of the row electrode Y reaches the voltage Vs after the passage of a predetermined period, the driving control circuit 50 switches the switching device S 22 to OFF and the switching device S 21 to ON. Consequently, a current path CR 1 including the power source B 3 , the switching device S 17 , the capacitor C 11 , the resistor R 12 , the power source B 6 , the switching device S 21 and the row electrode Y is formed, and an adding voltage (Vs+Vh) of a voltage Vh of the power source B 6 adding with the voltage Vs of the power source B 3 is applied to the row electrode Y. In this instance, the voltage of the row electrode Y rises more gradually than when it reaches the voltage Vs as shown in FIG. 7 . Here, when the voltage of the row electrode Y reaches the voltage (Vs+Vh), the driving control circuit 50 switches the switching devices S 17 and S 21 to OFF and the switching devices S 12 , S 15 and S 22 to ON. Consequently, the current resulting from the charge stored in the load capacitance C 0 of the PDP 10 flows into the capacitor C 2 through the row electrode Y, the switching devices S 22 and S 15 , the coil L 4 , the diode D 4 and the switching device S 12 . In this instance, the capacitor C 2 starts charging and the voltage of the electrode Y gradually decrease depending on the time constant of the capacitor C 2 and the coil L 4 (a first voltage drop period RSY1). The driving control circuit 50 switches the switching device S 18 to ON and the switching devices S 12 and S 15 to OFF. Consequently, a current path CR 2 of the switching devices S 22 and S 18 , the resistor R 2 and the diode D 7 is formed. In this instance, the voltage of the electrode Y lowers more gradually than the change of the voltage in the first voltage drop period RSY1 (a second voltage drop period RSY2) depending on the time constant of the load capacitance C 0 and the resistor R 2 .

As a result of a series of switching controls described above, a reset pulse RP y having a waveform shown in FIG. 7 is generated and is applied to all the row electrodes Y 1 to Y n . The voltage of the reset pulse RP y gradually rises and reaches the maximum voltage (Vs+Vh) with the gradients of two stages and thereafter decrease gradually with the gradients of two stages.

While the switching device S 17 is set to ON in the reset period shown in FIG. 7 , the driving control circuit 50 sets the switching device S 5 in the reset driver portion RSD x of the X-row electrode driver 30 to ON. In consequence, the voltage (−Vr) of the negative terminal of the power source B 7 is applied to the row electrode X through a circuit including the switching device S 5 , the capacitor C 4 and the resistors R 41 and R 42 . In this instance, the voltage of the row electrode X gradually decrease from the state of 0 V as shown in FIG. 7 . When the voltage of the row electrode X reaches the voltage (−Vr) described above, the driving control circuit 50 switches the switching device S 5 to OFF.

Owing to the operation described above, a reset pulse RP x having a wave shape shown in FIG. 7 is generated and is applied to all the row electrodes X 1 to X n . The voltage of the reset pulse RP gradually decrease from 0 V and reaches the minimum voltage (−Vr).

During the reset period, the reset pulse RPy having the positive polarity and the reset pulse RPx having the negative polarity are simultaneously applied as shown in FIG. 7 and reset discharge is induced inside all the discharge cells so that a wall charge having a desired quantity is formed inside each discharge cell. Consequently, all the discharge cells are initialized to a light-on mode in which sustain discharge can be made during sustain period to be described later.

Incidentally, in the embodiment shown in FIG. 7 , the drop waveform of the reset pulse RP y is gentle but it may be sharp, too. For example, both switching devices S 14 and S 15 are set to ON instead of setting the switching device S 18 to ON. Consequently, the drop waveform of the reset pulse RP y describes a waveform sharply changing from the maximum voltage (Vs+Vh) to 0 V.

During address period, the driving control circuit 50 sets the switching devices S 19 to S 21 of all the scan driver portions SCD disposed for each row electrode Y 1 to Y n to ON. Therefore, a voltage (V h −V off ) of the positive polarity as the sum of the voltage (−V off ) of the negative terminal of the power source B 5 and the voltage V h of the positive terminal of the power source B 6 is applied to the row electrode Y. In consequence, a base pulse BP having the pulse voltage value (V h −V off ) of the positive polarity shown in FIG. 7 is generated and is simultaneously applied to all the row electrodes Y 1 to Y n . Here, the driving control circuit 50 switches selectively and serially the switching device S 21 connected to each row electrode Y 1 to Y n to OFF and the switching device S 22 connected to each row electrode Y 1 to Y n to ON. Consequently, the voltage of the row electrode Y serially and sharply changes from the voltage V h of the positive polarity to the voltage (−V off ) of the negative polarity. After the passage of a predetermined period, the driving control circuit 50 switches the switching device S 21 to ON and the switching device S 22 to OFF. In consequence, the voltage of the row electrode Y sharply changes from the voltage (−V off ) of the negative polarity to the voltage (V h −V off ) of the positive polarity. As a result of a series of switching controls described above, a voltage is generated in the form in which the scan pulse SP having the voltage (−V off ) of the negative polarity overlaps with the base pulse BP having the voltage (V h −V off ) of the positive polarity shown in FIG. 7 is generated and is applied selectively and serially to each row electrode Y 1 to Y n . In the meantime, the address driver 2 applies the pixel data pulse DP corresponding to the pixel data for each pixel to the electrodes D 1 to Dm by each display line (m lines) on the basis of the image signal. In this instance, discharge (selective erase discharge) is selectively induced inside the discharge cell to which the pixel data pulse DP of the high voltage simultaneously with the scan pulse SP described above and the wall discharge formed inside this discharge cell disappears. In this instance, therefore, the discharge cell is set to a light-off mode. On the other hand, the selective erase discharge is not induced inside the discharge cells to which the scan pulse SP is applied but the pixel data pulse of the high voltage is not applied. Therefore, each discharge cell keeps the state immediately before. In other words, the discharge cell in which the wall charge remains keeps the light-on mode and the discharge cell in which the wall charge does not exist keeps the light-off mode.

As described above, each discharge cell is set to either one of the light-on mode and the light-off mode during the address period in accordance with the pixel data corresponding to the input image signal.

When the application of the scan pulse SP to each row electrode Y 1 to Y n is finished during the address period described above, the driving control circuit 50 switches each switching device S 19 to S 21 from ON to OFF and each switching device S 12 , S 15 , S 22 from OFF to ON. Consequently, the current resulting from the charge stored in the load capacitance C 0 of the PDP 10 flows into the capacitor C 2 through the row electrode Y, the switching devices S 22 and S 15 , the coil L 4 , the diode D 4 and the switching device S 12 . In this instance, the capacitor C 2 starts charging and the voltage of the electrode Y gradually decrease depending on the time constant of the capacitor C 2 and the coil L 4 as shown in FIG. 7 (a first voltage drop period ASY1). The driving control circuit 50 switches the switching device S 18 to ON and the switching devices S 12 and S 15 to OFF. Consequently, a current path CR 2 including the switching devices S 22 and S 18 , the resistor R 2 and the diode D 7 is formed. In this instance, the voltage of the electrode Y decrease more gradually than the change in the first voltage drop period ASY1 depending on the time constant of the load capacitance C 0 and the resistor R 2 (a second voltage drop period ASY2). In other words, the fall period of the voltage value of the base pulse BP applied to all the row electrodes Y during the address period shown in FIG. 7 includes the first voltage drop period ASY1 and the second voltage drop period ASY2. This means that the change ratio of the voltage value of the base pulse BP in the fall period is smaller than the change ratio of the voltage value in the fall period in the scan pulse SP.

During sustain period, the driving control circuit 50 first switches the switching device S 14 of the sustain driver portion SUD from OFF to ON and after the passage of a predetermined period, switches the switching device S 15 of the sustain driver portion SUD from OFF to ON. The driving control circuit 50 interruptedly repeats switching setting SSY shown in FIG. 7 for each of the switching devices S 11 to S 14 of the sustain driver portion SUD. Furthermore, the driving control circuit 50 interruptedly repeats switching setting SSX shown in FIG. 7 for each of the switching devices S 1 to S 4 of the X-row electrode driver 30 . Incidentally, the driving control circuit 50 repeatedly executes switching setting SSY and SSX the number of times corresponding to weighting of each sub-field during the sustain period of each sub-field.

In switching setting SSX, only the switching device S 1 among the switching devices S 1 to S 4 is turned ON and the current resulting from the charge stored in the capacitor C 1 flows into the discharge cell through the coil L 1 , the diode D 1 and the row electrode X. Consequently, the voltage of the row electrode X gradually rises as shown in FIG. 7 . Next, the switching device S 3 is turned ON with the switching device S 1 and the voltage V s of the power source B 1 is as such applied to the row electrode X, so that the voltage of the row electrode X is fixed at the voltage V s . Then, only the switching device S 2 among the switching devices S 1 to S 4 is turned ON and the current resulting from the charge stored in the load capacitance C 0 between the row electrodes X and Y flows into the capacitor C 1 through the row electrode X, the coil L 2 and the diode D 2 . In consequence, the voltage of the row electrode X gradually decrease as shown in FIG. 7 . As this switching setting SSX is interruptedly repeated, a sustain discharge pulse IPx having the voltage Vs shown in FIG. 7 as the pulse voltage value is generated and is repeatedly applied to the row electrode X.

In switching setting SSY, only the switching device S 11 among the switching devices S 11 to S 14 and S 17 to S 22 is first turned ON and the current resulting from the charge stored in the capacitor C 2 flows into the discharge cell through the coil L 3 , the diode D 3 , the switching device S 15 , the switching device S 22 and the row electrode Y. Consequently, the voltage of the row electrode Y gradually rises as shown in FIG. 7 . Next, the switching device S 13 is turned ON with the switching device S 11 and the voltage V s of the power source B 3 is applied to the row electrode Y through the switching device S 15 and the switching device S 22 . Consequently, the voltage of the row electrode Y is fixed at the voltage V s as shown in FIG. 7 . Then, only the switching device S 12 among the switching devices S 11 to S 14 and only the switching device S 22 among the switching devices S 17 to S 22 are turned ON and the current resulting from the charge stored in the load capacitance C 0 between the row electrodes X and Y flows into the capacitor C 1 through the row electrode Y, the switching devices S 22 and S 15 , the coil L 4 and the diode D 4 . In consequence, the voltage of the row electrode Y gradually decrease as shown in FIG. 7 . As this switching setting SSY is interruptedly repeated, a sustain discharge pulse IP y having the voltage Vs shown in FIG. 7 as the pulse voltage value is generated and is repeatedly applied to the row electrode Y.

During the sustain period, only the discharge cell in which the wall charge exists, that is, only the discharge cell set to the light-on mode as described above, causes discharge (sustain discharge) whenever the sustain discharge pulses IP x and IP y are applied thereto, and repeats emission of light with the discharge. In other words, only the discharge cell set to the light-on mode repeats light emission the number of times corresponding to weighting of the sub-field during the sustain period of each sub-field.

In the driving operation shown in FIG. 7 , the base pulse BP having the same polarity as the pixel data pulse is applied to all the row electrodes Y 1 to Y n during the address period. In this way, so-called “erroneous discharge” in which discharge is erroneously induced between the row electrode Y to which the scan pulse SP is not applied and the column electrode D is prevented. In this instance, the change ratio of the voltage value in the base pulse BP in the fall period is set to a smaller value than the change ratio of the voltage value in the fall period in the scan pulse SP in the driving operation shown in FIG. 7 . In other words, the change of the voltage value at the rear edge portion in the base pulse BP is set to be more gentle than the change of the voltage value at the edge portion in the scan pulse SP. In comparison with the case where the change of the voltage value at the rear edge portion in the base pulse BP is sharp, therefore, the amount of noise occurring at this rear edge portion much more decreases. In this instance, because also the quantity of the current flowing into the driver IC with such a noise becomes smaller, durability of the driver IC can be improved to a higher level.

This application is based on a Japanese patent application No. 2003-199874 which is hereby incorporated by reference.