Patent Application
20050052361
1. Field of the Invention
The present invention relates to a method for driving an address-display separated-type AC (alternating current) plasma display panel and a driving device using the method and more particularly to the method for driving the address-display separated-type AC plasma display panel (PDP) in which display with high definition is made possible and to the driving device using the above method.
The present application claims priority of Japanese Patent Application No. 2003-320461 filed on Sep. 11, 2003, which is hereby incorporated by reference.
2. Description of the Related Art
A plasma display panel (hereinafter may referred simply to as a “PDP”) has, in general, many advantages in that it can be made thin, display on a large screen is made possible with comparative ease, it can provide a wide viewing angle, it can give a quick response, and a like. Therefore, in recent years, the PDP is being widely and increasingly used, as a flat display panel, for wall-hung televisions, public information boards, or a like.
The PDP is roughly classified, depending on its operating method, into two types, one being a DC (Direct Current)-type PDP and another being an AC-type PDP. The DC-type PDP is a PDP whose electrodes are exposed in a discharge space and which is operated in a direct-current discharge state. The AC-type PDP is a PDP whose electrodes are coated with a dielectric layer and are not exposed directly in a discharge gas and which is operated in an alternating-current discharge state. In the DC-type PDP, only while a voltage is being applied, discharge occurs. In the AC-type PDP, discharge is sustained by reversing a polarity of a voltage to be applied. The AC-type PDP is also classified into two types, one being a two-electrode type whose number of electrodes in a display cell is two and another being a three-electrode type whose number of electrodes in the display cell is three.
The three-electrode AC-type PDP will be described below. A plasma display panel 110 of the PDP, as shown in
On each region on the front substrate 120 being placed by the rib apart from the rear substrate 121 at a specified interval and being partitioned by the rib are arranged one scanning electrode 122i and one sustaining electrode 123i (see
A metal layer 132i is stacked on each of the scanning electrodes 122i and each of the sustaining electrodes 123i which are formed on the front substrate 120 made up of a glass substrate or a like (see
A discharge space 126ij in the three-electrode AC-type PDP 110 having such the configurations as above is filled with a mixed gas of He (helium), Ne (neon), Xe (xenon), and a like in a hermetically sealed manner. As a reference material describing such the conventional three-electrode AC-type PDP, “Society for Information Display 98 Digest” (SID 98 DIGEST) (Page 279 to 281, May, 1998) is available.
Next, configurations of a driving circuit for the conventional three-electrode AC-type PDP 110 are described by referring to
The scanning driver 134i, as shown in
The pre-discharge power feeding circuit 142 is used to reset wall charges accumulated in the sustaining period 4 in a previous sub-field by using a sawtooth-like wave signal to be first applied in the pre-discharge period 2 (see
The scanning control circuit 148 operates to receive video signals and to feed each of control pulses described below to the pMOS Ti1 and nMOS Ti2. That is, the scanning control circuit 148 feeds a control pulse to turn ON the pMOS Ti1 to a gate of the pMOS Ti1 and a control pulse to turn OFF the nMOS Ti2 to a gate of the nMOS Ti2 in the pre-discharge period 2 during which the three kinds of sawtooth-like wave signals described above are fed from the pre-discharge power feeding circuit 142.
The scanning control circuit 148 feeds, in a period during which a scanning pulse is applied, a control pulse to turn OFF the PMOS Ti1 to a gate of the PMOS Ti1 and a control pulse to turn ON the nMOS Ti2 to a gate of the nMOS Ti2, while it feeds, in the scanning period 3 other than the period during which a scanning pulse is applied, a control pulse to turn ON the pMOS Ti1 to the gate of the pMOS Ti1 and a control pulse to turn OFF the nMOS Ti2 to the gate of the nMOS Ti2.
The scanning control circuit 148 repeats operations, alternately for every half of a period during which a sustaining pulse is applied in the sustaining period 4, that the PMOS Ti1 is turned ON and the nMOS Ti2 is turned OFF in a first half of a period during which a sustaining pulse is being fed and a control pulse to turn OFF the nMOS Ti2 is fed to the gate of the pMOS Ti1 and a control pulse to turn ON the nMOS Ti2 is fed to the gate of the nMOS Ti2 in a second half of the period during which the sustaining pulse is being fed. These operations drive a sustaining driver 149 on a side in which scanning operations are performed.
The sustaining control circuit 152 making up the sustaining driver 136 operates to receive video signals and to feed each of control pulses described below to the PMOS Ti1 and nMOS Ti2. That is, it feeds a control pulse to turn ON a switch Ts to an ON/OFF control inputting port of the switch Ts and a control pulse to turn OFF a switch Tg to an ON/OFF control inputting port of the switch Tg in a period during which a first sawtooth-like wave signal out of the above three kinds of the sawtooth-like signals fed in the pre-discharge period 2 is fed. Then, it also feeds a control pulse to turn OFF the switch Ts to the ON/OFF control inputting port of the switch Ts and a control pulse to turn ON the switch Tg to the ON/OFF control inputting port of the switch Tg in a period during which a second sawtooth-like wave signal is fed. Further, it also feeds a control pulse to turn ON the switch Ts to the ON/OFF control inputting port of the switch Ts and a control pulse to turn OFF the switch Tg to the ON/OFF control inputting port of the switch Tg both in a period during which a last sawtooth-like wave signal is fed and in the scanning period 3.
Also, the sustaining control circuit 152 repeats operations, in the sustaining period 4, alternately during every half period during which a sustaining pulse is being applied, by which a control pulse to turn OFF the switch Ts is fed to the ON/OFF control inputting port of the switch Ts and a control pulse to turn ON the switch Tg is fed to the ON/OFF control inputting port of the switch Tg in a first half of the period during which the sustaining pulse is being fed and a control pulse to turn ON the switch Ts is fed to the ON/OFF control inputting port of the switch Ts and a control pulse to turn OFF the switch Tg is fed to the ON/OFF control inputting port of the switch Tg in a second half of the period during which the sustaining pulse is being fed. One terminal of the switch Ts is connected to the second power feeding circuit 150 and another terminal of the switch Ts is connected to one terminal of the switch Tg. A connecting point between the switch Ts and switch Tg is connected to the sustaining electrode Ci. Another terminal of the switch Tg is connected to a port for a ground potential.
Next, a method for driving the three-electrode address-display separated-type AC PDP 110 having configurations as described above is explained. Now, let it be assumed for explanation that operations during a sub-field 5 start (see
To solve this problem, conventionally, the scanning driver 134i operates to perform initializing (resetting) operations and priming discharge operations in the pre-discharge period 2 in the sub-field 5. That is, the scanning driver 134i turns ON the PMOS Ti1 and turns OFF the nMOS Ti2 to apply a first sawtooth-like wave signal to the scanning electrode Si and the sustaining driver 136 turns ON the switch Ts and OFF the switch Tg from a second half of a period during which a last sustaining pulse fed in the sustaining period 4 in the previous sub-field is being fed. In the period during which the above first sawtooth-like wave signal is being fed to the scanning electrode Si, a voltage Vs is applied to the sustaining electrode Ci and wall charges formed in the sustaining period 1 in the previous sub-field are reset.
Then, the scanning driver 134i turns ON the PMOS Ti1 and OFF the nMOS Ti2 to apply a second sawtooth-like wave signal to the scanning electrode Si, while the sustaining driver 136 turns OFF the switch Ts and ON the switch Tg to apply a ground potential to the sustaining electrode Ci, causing priming discharge to occur. Further, the scanning driver 134i turns ON the PMOS Ti1 and OFF the nMOS Ti2 to apply a last sawtooth-like wave signal to the scanning electrode Si and the sustaining driver 136 turns ON the switch Ts and OFF the switch Tg to apply the voltage Vs to the sustaining electrode Ci in a period during which the above last sawtooth-like wave signal is being applied and in the scanning period 3, thus causing wall charges occurred by priming discharge to be adjusted. The priming discharge operations and wall charge adjusting operations are performed to achieve easy writing of display data to be done in a one-pass scanning manner according to display data, that is, to realize easy occurrence of discharge in a display cell.
When the pre-discharge period 2 described above ends, operations in the scanning period 3 start. From starting time of the scanning period 3, a voltage “Vbw” begins to be output from the voltage source 145 in the scanning driver 134i to the line 147 and to be applied to the scanning electrode Si and, as described above, from starting time of the application of the last sawtooth-like wave signal in the pre-discharge period 2, the voltage “Vs” begins to be applied to the sustaining electrode Ci from the sustaining driver 136. Time of termination of the application of the voltage “Vbw” to be output by the scanning driver 134i to the line 147 is the same as ending time of the scanning period 3 and time of termination of the application of the voltage Vs to be applied by the sustaining driver 136 to the sustaining electrode Ci is the same as ending time of the scanning period 3.
On the other hand, to the gate of the pMOS Ti1 is applied a pulse to turn OFF the PMOS Ti1 from the scanning control circuit 148 with same timing with which display data (pixel data) existing on the i-th scanning line is applied, which makes up video signals fed in one field, for example, display data to be fed to the data electrode Dj is fed and, at the same time, to the gate of the nMOS Ti2 is applied a pulse to turn on the nMOS Ti2 by the scanning control circuit 148 with same timing as described above.
Therefore, while a scanning pulse (see reference number 6 in
In a display cell (in the intersecting portion between the scanning electrode and data electrode) to which data pulse is fed, since a voltage between the scanning electrode Si and the data electrode Dj is boosted and, after the application of the voltage, writing discharge occurs between the scanning electrode Si and data electrode Dj with some time delay (hereinafter called a discharge delay), positive wall charges are formed on a side of the scanning electrode Si. Also, between the sustaining electrode Ci and scanning electrode Si (between surface electrodes) where a large bias is being applied in a potential state at the discharge time, since movements of electric charges occur by an electric field generated between the electrodes, negative wall charges are formed on the sustaining electrode Ci.
Contrary to the above case, in a display cell (pixel) to which a data pulse 7 is not fed, since a voltage between the scanning electrode Si and data electrode Dj is not boosted, writing discharge does not occur and a wall charge change that may occur in such the case where the data pulse 7 is applied does not occur.
Thus, depending on whether or not the data pulse 7 is applied to a display cell, two types of states of wall charges can be made to occur between the scanning electrode Si and sustaining electrode Ci. When these two states of wall charges are made to continue to exist during the subsequent sustaining period 4, display or no-display of the pixel continues. This operation is explained below.
When the application of a scanning pulse 6 to all the scanning electrodes Si (from i=1 to i=m) is terminated, operations in the sustaining period 4 start. A sustaining pulse is applied, by the sustaining driver 149 and sustaining driver 136 on a side where scanning operations are performed, alternately to all the scanning electrodes Si to Sm and all the sustaining electrodes Ci to Cm in a specified period. To the scanning electrode Si is first applied a positive sustaining pulse and then a negative sustaining pulse. The positive sustaining pulse and negative sustaining pulse are alternately applied. To the sustaining electrode Ci is applied a negative sustaining pulse first and then a positive sustaining pulse. The negative sustaining pulse and positive sustaining pulse are alternately applied. A voltage of each of these sustaining pulses is set at a voltage at which discharge (called surface discharge) between a scanning electrode Sk and a sustaining electrode C1 does not start in a display cell 131K1 (“k” is one of 1, 2, . . . , m and “1” is one of 1, 2, . . . , n). More specifically the set voltage is 170 V.
Contrary to the above case, in a display cell 131OP (“O” is one of 1, 2, . . . , m and other than “k” and “P” is one of 1, 2, . . . , n other than “1”) in which writing discharge has occurred, as described above, since a positive wall charge is formed on the scanning electrode SO and a negative wall charge is formed on the sustaining electrode CP, a voltage to be produced by the positive and negative wall charges is superimposed on a voltage of the first positive sustaining pulse (called a “first sustaining pulse”) to be applied to the scanning electrode SO in a forward direction. This causes a voltage exceeding a surface firing voltage to be applied to discharge space 126OP in the display cell 131OP and sustaining discharge occurs between the scanning electrode SO and the sustaining electrode CP. By this sustaining discharge, negative wall charges are accumulated on the scanning electrode SO and positive wall charges on the sustaining electrode CP, which reverses the accumulated state of wall charges.
When the application of the first sustaining pulse is completed, a voltage pulse to be applied to the scanning electrode SO from the sustaining driver 149 on the side where scanning operations are performed and a voltage pulse to be applied to the sustaining electrode CP from the sustaining driver 136 are reversed in phase and each of the phase-reversed voltage pulses (called a “second sustaining pulse”) is applied to the corresponding scanning electrode SO and sustaining electrode CP. A voltage of negative wall charges accumulated on the scanning electrode SO and a voltage of positive wall charges accumulated on the sustaining electrode CP are superimposed on a voltage of the second sustaining pulse to be applied as above in a forward direction and, as in the case of the first sustaining pulse, wall charges having a polarity being reverse to that of a voltage of the first sustaining pulse, that is, positive wall charges are accumulated on the scanning electrode SO and negative wall charges on the sustaining electrode CP.
Even after the application of the second sustaining pulse has been terminated, since the application of the first sustaining pulse and the second sustaining pulse is repeated, discharge continues to occur between the scanning electrode SO and the sustaining electrode CP. That is, a potential difference produced by wall charges formed on the scanning electrode SO and the sustaining electrode CP by the X-th sustaining discharge is superimposed on a voltage of the “X+1st” sustaining pulse, which causes the sustaining discharge to be sustained.
By operating as above, light-emitting in the display cell 131OP continues. Light-emitting luminance in the display cell 131OP is determined by the number of times of sustaining the sustaining discharge. Moreover, by changing the number of sustaining pulses to be applied in each sub-field, gray levels in the display cell 131OP can be adjusted.
A method is disclosed in Japanese Patent Application Laid-open No. Hei 6-337654 in which, in an address-while-display (AWD) driving method in which scanning operations are performed while a sustaining pulse is being applied, after application of a scanning pulse, a pulse having a polarity being reverse to a scanning pulse is applied to an electrode to which a scanning pulse is not applied, out of two surface electrodes. Also, a method is disclosed in Japanese Patent Application Laid-open No. 2001-117532 in which pulse application time is provided between time for application of a scanning pulse and time for application of a subsequent pulse and, during the pulse application time, a pulse having a polarity being reverse to that of the scanning pulse is applied to a sustaining electrode.
In the conventional method for driving the address-display separated-type AC PDP performing such operations as above, when an image with high definition is to be displayed by increasing the number of scanning lines, the scanning period 3 is lengthened as the number of the scanning lines increases. If a frequency to be used in one field is fixed to be 60 Hz, a length of the sustaining period 4 corresponding to an increased length of the scanning period 3 is decreased. The decrease in the length of the sustaining period 4 causes lowering of light-emitting luminance which degrades a display characteristic.
An available countermeasure to avoid the above degradation includes a method by which the number of sub-fields is decreased and another method by which a width of a scanning pulse is decreased. However, the decrease in the number of sub-fields causes a decrease in the number of gray levels or occurrence of false contouring of moving images.
The decrease in a width of a scanning pulse presents the following problems. That is, as is apparent from above descriptions, in the conventional driving method, when application of a scanning pulse is terminated, a potential of the scanning electrode Si is boosted to become a voltage “Vbw”, a potential difference between the scanning electrode Si and sustaining electrode Ci is reduced to be a voltage of “Vs−Vbw”. This means that amounts of movements of space charges which are formed between the scanning electrode Si and sustaining electrode Ci at time of the application of the scanning pulse 6 and which produce wall charges on each of electrodes rapidly becomes small at the same time when the application of the scanning pulse 6 is terminated, which causes further formation of wall charges to be weakened.
That is, since time before the application of the scanning pulse is terminated after writing discharge has started is shortened, formation of wall charges sufficiently enough to let operations in the scanning period 3 shift to have sustaining discharge occur in the sustaining period 4 on the scanning electrode Si and sustaining electrode Ci becomes difficult.
In such the state in which sufficient wall charges are not formed on the scanning electrode Si and sustaining electrode Ci, even if the first sustaining pulse is applied when operations in the sustaining period 4 start and shift to sustaining discharge and even if a voltage of a wall charge formed by the writing discharge is superimposed on the voltage “Vs” of the first sustaining pulse, since the wall charges are not formed sufficiently as described above, a potential difference between the scanning electrode Si and sustaining electrode Ci does not reach a potential difference required for making sustaining discharge occur, that is, does not reach a surface firing voltage being a minimum voltage required for occurrence of surface discharge.
Therefore, unless sufficiently intense discharge occurs before operations start in the sustaining period and unless, when the first sustaining pulse is applied after the occurrence of the intense discharge, a wall charge having a polarity being reverse to that of the wall charge formed by the above discharge is formed on the scanning electrode Si and sustaining electrode Ci, operations do not shift to have sustaining discharge occur with reliability, thus causing a display cell not to be lit or a flicker to occur in displayed images.
To improve points described above, a voltage of a sustaining pulse or of a data pulse has to be boosted. This causes an increase in power consumption and/or use of an expensive driver that can withstand a high voltage, which leads to high costs.
In the address-while-display (AWD) driving method disclosed in Japanese Patent Application Laid-open No. Hei 6-337654 in which scanning operations are performed while a sustaining pulse is being applied, after the application of a scanning pulse, a pulse having a polarity being reverse to that of the scanning pulse is applied to an electrode, out of two surface electrodes, to which the scanning pulse has not been applied. However, simple application of this method to the address-display separated method does not produce a satisfactory effect. To obtain sufficient effects, optimization of a pulse voltage, a position of a pulse to be applied, and a width of the pulse is necessary.
In the method disclosed in Japanese Patent Application Laid-open No. 2001-117532, pulse application time is provided between time for application of a scanning pulse and time for application of a subsequent pulse and, during the pulse application time, a pulse having a polarity being reverse to that of the scanning pulse is applied to a sustaining electrode. Therefore, the pulse application time during which a pulse is applied to a sustaining electrode between time for application of a scanning pulse and time for application of a subsequent pulse is additionally required. As a result, this method enables the scanning pulse to be shortened, however, a scanning period cannot be shortened.
In view of the above, it is an object of the present invention to provide a method for driving an address-display separated-type AC PDP which is capable of, only if writing discharge occurs once, having sequentially and continuously wall charges be formed sufficiently on a scanning electrode and a sustaining electrode and of maintaining a sustaining discharge even when a width of a scanning pulse is shortened and even if the PDP is driven at a low sustaining voltage, and a plasma display device driven by using the driving method.
According to a first aspect of the present invention, there is provided a method for driving an address-display separated-type AC (Alternating Current) plasma display panel in which a first insulating substrate and a second insulating substrate are mounted at a specified interval in a manner to oppose to each other, a first specified number of pairs of a scanning electrode and a sustaining electrode being positioned in parallel to each other is arranged on a face of the first insulating substrate, the face being opposite to the second insulating substrate, and a second specified number of data electrodes being positioned in orthogonal to each of the pairs of the scanning electrode and the sustaining electrode is arranged on a face of the second insulating substrate, the face being opposite to the first insulating substrate, wherein pixel data corresponding to a video signal is sequentially written in a scanning period in each of display cells formed at an intersecting point between each of the pairs of the scanning electrode and sustaining electrode and each of the data electrodes and displaying of written pixels is sustained by sustaining discharge in a sustaining period, the method including:
In the foregoing, a preferable mode is one wherein the first specified time is arbitrary time existing between time of termination of a period during which the scanning pulse is applied and time at which formation of wall charges required for the sustaining discharge is unable to occur and the first period of time is a period of time that can be arbitrarily selected during a period of time existing from the first specified time to time at which, though formation of wall charges is made to continue by movements of space charges between the scanning electrode and the sustaining electrode making up the pair, no erroneous discharge occurs.
Also, a preferable mode is one wherein, by applying a writing wall charge forming pulse, having a polarity reverse to that of the scanning pulse, to the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied during the period of time from the arbitrary time, the potential difference is generated between the scanning electrode and the sustaining electrode making up the pair.
Also, a preferable mode is one, wherein, by dividing the two or more sustaining electrodes into two sustaining electrode groups and by sequentially and alternately applying the scanning pulse to the scanning electrode selected from scanning electrodes being paired with the sustaining electrode making up each of the two sustaining electrode groups and by alternately applying a writing wall charge forming pulse, having a polarity reverse to that of the scanning pulse, to each of the sustaining electrodes in the group to which the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied belongs from time of termination of a period during which the scanning pulse is applied to a period of the first specified period of time in a period of application of the scanning pulse in every group, the potential difference is made to be generated between the scanning electrode and the sustaining electrode making up the pair.
According to a second aspect of the present invention, there is provided a method for driving an address-display separated-type AC (Alternating Current) plasma display panel in which a first insulating substrate and a second insulating substrate are mounted at a specified interval in a manner to oppose to each other, a first specified number of pairs of a scanning electrode and a sustaining electrode being positioned in parallel to each other is arranged on a face of the first insulating substrate, the face being opposite to the second insulating substrate, and a second specified number of data electrodes being positioned in orthogonal to each of the pairs of the scanning electrode and the sustaining electrode is arranged on a face of the second insulating substrate, the face being opposite to the first insulating substrate, wherein pixel data corresponding to a video signal is sequentially written in a scanning period in each of display cells formed at an intersecting point between each of the pairs of the scanning electrode and sustaining electrode and each of the data electrodes and displaying of written pixels is sustained by sustaining discharge,in a sustaining period, the method including:
In the foregoing, a preferable mode is one wherein the second specified time is arbitrary time existing between time after time of termination of a period during which no erroneous discharge occurs when the potential difference is applied between the scanning electrode and the sustaining electrode making up the pair and time of termination of a period during which the scanning pulse is applied and wherein the second period of time is a period of time that can be arbitrarily selected during a period of time existing from the second specified time to time at which, though formation of wall charges is made to continue by movements of space charges between the scanning electrode and the sustaining electrode making up the pair, no erroneous discharge occurs.
Also, a preferable mode is one wherein, by applying a writing wall charge forming pulse, having a polarity reverse to that of the scanning pulse, to the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied during the period of time from the arbitrary time, the potential difference is generated between the scanning electrode and sustaining electrode making up the pair.
According to a third aspect of the present invention, there is provided a method for driving an address-display separated-type AC (Alternating Current) plasma display panel in which a first insulating substrate and a second insulating substrate are mounted at a specified interval in a manner to oppose to each other, a first specified number of pairs of a scanning electrode and a sustaining electrode being positioned in parallel to each other is arranged on a face of the first insulating substrate, the face being opposite to the second insulating substrate, and a second specified number of data electrodes being positioned in orthogonal to each of the pairs of the scanning electrode and the sustaining electrode is arranged on a face of the second insulating substrate, the face being opposite to the first insulating substrate, wherein pixel data corresponding to a video signal is sequentially written in a scanning period in each of display cells formed at an intersecting point between each of the pairs of the scanning electrode and sustaining electrode and each of the data electrodes and displaying of written pixels is sustained by sustaining discharge in a sustaining period, the method including:
In the foregoing, a preferable mode is one wherein, by applying a sustaining base voltage, having a polarity reverse to that of the scanning pulse, in the scanning period during which the scanning pulse is not applied to the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied, the potential difference is produced between the scanning electrode and the sustaining electrode making up the pair.
Also, a preferable mode is one wherein a potential of the scanning pulse is lower by a specified value than a potential of the scanning pulse being applied in the scanning period other than a period during which the scanning pulse is applied.
According to a fourth aspect of the present invention, there is provided a driving device for an address-display separated-type AC plasma display panel including:
In the foregoing, a preferable mode is one wherein the first specified time during which the potential difference is applied by the potential difference applying unit is arbitrary time existing between time of termination of a period during which the scanning pulse is applied and time that no formation of wall charges required for the sustaining discharge occur and wherein the first specified period of time is time that can be arbitrarily selected during a period of time from the first specified time to time at which, though formation of wall charges is made to continue by movements of space charges between the scanning electrode and the sustaining electrode making up the pair, no erroneous discharge occurs.
Also, a preferable mode is one wherein the potential difference applying unit is a sustaining driver which applies a writing wall charge forming pulse, having a polarity reverse to that of the scanning pulse, to the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied during the period of time from the arbitrary time to generate the potential difference between the scanning electrode and the sustaining electrode making up the pair.
Also, a preferable mode is one wherein the potential difference applying unit is a sustaining driver which divides two or more sustaining electrodes into two sustaining electrode groups, applies sequentially and alternately the scanning pulse to the scanning electrode selected from scanning electrodes being paired with the sustaining electrode making up each of the two sustaining electrode groups and applies alternately a writing wall charge forming pulse, having a polarity reverse to that of the scanning pulse, to each of the sustaining electrodes in the group to which the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied belongs from time of termination of a period during which the scanning pulse is applied to a period of the first specified period of time in a period of application of the scanning pulse in every group, the potential difference is made to be generated between the scanning electrode and the sustaining electrode making up the pair.
According to a fifth aspect of the present invention, there is provided a driving device for an address-display separated-type AC plasma display panel including:
In the foregoing, a preferable mode is one wherein the second specified time during which the potential difference applying unit applies the potential difference between the scanning electrode and the sustaining electrode making up the pair is arbitrary time existing between time after time of termination of a period during which no erroneous discharge occurs when the potential difference is applied between the scanning electrode and the sustaining electrode making up the pair and during which the scanning is applied and time of termination of a period during which the scanning pulse is applied and wherein the second period of time is a period of time that can be arbitrarily selected during a period of time from the second specified time to time at which, though formation of wall charges is made to continue by movements of space charges between the scanning electrode and the sustaining electrode making up the pair, no erroneous discharge occurs.
Also, a preferable mode is one wherein the potential difference applying unit is a sustaining driver which applies a writing wall charge forming pulse, having a polarity reverse to that of the scanning pulse, to the sustaining electrode being paired with the scanning electrode to which the scanning pulse is applied during the period of time from the arbitrary time to generate the potential difference between the scanning electrode and the sustaining electrode making up the pair.
According to a sixth aspect of the present invention, there is provided a driving device for an address-display separated-type AC plasma display panel including:
In the foregoing, a preferable mode is one wherein the potential difference applying unit is a sustaining driver which applies a sustaining base voltage, having a polarity reverse to that of the scanning pulse, to the sustaining electrode being paired with the scanning electrode in the scanning period during which the scanning pulse is not applied to generate the potential difference between the scanning electrode and the sustaining electrode making up the pair.
Also, a preferable mode is one wherein the sustaining driver, in the scanning period, after having applied the sustaining base voltage to the sustaining electrode, immediately before the scanning pulse is applied to the scanning electrode, for a period from the time immediately before the application of the scanning pulse to time of termination of the scanning pulse, puts all the sustaining electrodes into a floating state.
Also, a preferable mode is one wherein the sustaining driver, in the scanning period, after having applied the sustaining base voltage to the sustaining electrode, puts all the sustaining electrodes into a floating state and then all the sustaining electrodes are connected through a diode to a port having a specified voltage being lower than that of the sustaining electrode so that the sustaining electrode is operated as a cathode.
Furthermore, a preferable mode is one wherein a potential of the scanning pulse to be applied by the writing unit to the scanning electrode is lower by a specified value than a potential occurring in the scanning period other than the period during which the scanning pulse is applied.
With the above configuration, a potential which is equal to two-thirds or more of a surface firing voltage between a scanning electrode and a sustaining electrode and is equal to a voltage or less at which no discharge starts between the scanning electrode and sustaining electrode is applied between the scanning electrode and the sustaining electrode, after application of a scanning pulse, in a period during which, though formation of wall charges is facilitated by movements of a space charge, no erroneous discharge occurs and, therefore, it is possible to successfully solve technical problems occurring when a method of accommodating an increase in a scanning period associated with display of images with high definition by shortening a pulsing period of a scanning pulse, that is, the technical problems in that prevention of a voltage of a sustaining pulse and data pulse from becoming high cannot be easily achieved and accumulation of sufficient wall charges required for occurrence of sustaining discharge at time of terminating the application of the scanning pulse is difficult.
The prevention of a voltage of a sustaining pulse and data pulse from becoming high can be achieved by suppressing an increase in a minimum sustaining pulse voltage “Vdsmin” at which normal operations can be performed and/or in a minimum data pulse voltage “Vdmin” at which normal operations can be performed. Since such the above effects can be obtained, a shift of operations to have sustaining discharge occur with reliability is made possible, which serves to prevent a display cell from being not lit and/or to avoid occurrence of a flicker in displaying.
With another configuration, two or more sustaining electrodes are commonly driven and, therefore, a sustaining driver can be simplified and costs can be reduced.
Moreover, the present invention can be applied to a driving method for an address-display separated PDP other than three-electrode AC PDP.
The above and other objects, advantages, and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
Best modes of carrying out the present invention will be described in further detail using various embodiments with reference to the accompanying drawings. According to the present invention, when a PDP having a display cell formed at an intersecting point among each of two or more scanning electrodes and sustaining electrodes arranged in a manner to be parallel to one another and to make up pairs and each of two or more data electrodes each being arranged in a manner to be orthogonal to each of the scanning electrodes and sustaining electrodes is driven by an address-display separated method, a method of using a potential difference applying means is employed by which a voltage being equal to two-thirds or more of a surface firing voltage between each of the scanning electrodes and each of the sustaining electrodes and equal to the voltage or less at which no discharge occurs between each of the scanning electrodes and each of the sustaining electrodes is applied to a scanning electrode and a sustaining electrode, after termination of application of a scanning pulse to be sequentially applied, with different timing, to each of the scanning electrodes in a scanning period, from specified time within a first time during which, even if a potential difference occurred by writing on a display cell is applied between each of the scanning electrodes and each of the sustaining electrodes, movements of space charges caused by writing discharge on a display cell are reduced to a degree to which formation of wall charges sufficiently enough to maintain sustaining discharge in a sustaining period becomes impossible and in a first period during which, though formation of wall charges is facilitated by movements of space charges between each of the scanning electrodes and each of the sustaining electrodes, no erroneous discharge occurs.
Also, according to the present invention, when the PDP having a display cell formed at an intersecting point among each of two or more scanning electrodes and sustaining electrodes arranged in a manner to be parallel to one another and to make up pairs and each of two or more data electrodes each being arranged in a manner to be orthogonal to each of the scanning electrodes and sustaining electrodes is driven by an address-display separated method, a method of using a potential difference applying means is employed, by which, for a period from specified time within second time during which, even if the voltage being equal to two-thirds or more of a surface firing voltage between each of the scanning electrodes and each of the sustaining electrodes and being equal to a voltage or less at which no discharge occurs between each of the scanning electrodes and each of the sustaining electrodes is applied between each of the scanning electrodes and each of the sustaining electrodes, no erroneous discharge occurs, before termination of sequential application of a scanning pulse, with different timing, to each of the scanning electrodes in the scanning period, to a second period of time during which, though formation of wall charges is facilitated by movements of space charges between each of the scanning electrodes and each of the sustaining electrodes, no erroneous discharge occurs, the above potential difference is applied to each of the scanning electrodes and each of the sustaining electrodes.
Furthermore, according to the present invention, when the PDP having a display cell formed at an intersecting point among each of two or more scanning electrodes and sustaining electrodes arranged in a manner to be parallel to one another and to make up pairs and each of two or more data electrodes each being arranged in a manner to be orthogonal to each of the scanning electrodes and sustaining electrodes is driven by an address-display separated method, a method of using a potential difference applying means is employed, by which, in the scanning period during which a scanning pulse to be sequentially applied, with different timing, is not applied to each of the scanning electrodes, a potential difference is applied at which no erroneous discharge occurs between each of the scanning electrodes and each of the sustaining electrodes even if a voltage being equal to two-thirds or more of a surface firing voltage between each of the scanning electrodes and each of the sustaining electrodes and being equal to the voltage or less at which no discharge occurs between each of the scanning electrodes and each of the sustaining electrodes is applied between each of the scanning electrodes and each of the sustaining electrodes.
In the driving device 30 of the address-display separated-type AC PDP of the first embodiment, even if a width of a scanning pulse is shortened, only if writing discharge occurs once, sufficient wall charges are sequentially and continuously formed even when the PDP is driven at a low sustaining voltage and sustaining discharge can be sustained. Configurations of the address-display separated-type AC PDP (three-electrode AC-type PDP) of the embodiment are the same as those shown in
The driving device 30, as shown in
Operations of the sustaining driver 36i differ from those of the sustaining driver shown in
That is, the sustaining driver 36i is made up of a pMOS Ti3, an nMOS Ti4 whose drain is connected to a drain of the PMOS Ti3, a switch Ts connected through a line 38 to a source of the nMOS Ti4, and a switch Tg connected through the line 38 to the source of the nMOS Ti4, and a sustaining control circuit 40 connected to a gate of the pMOS Ti3, gate of the nMOS Ti4, ON/OFF control inputting port of the switch Ts, and ON/OFF control inputting port of the switch Tg through each of corresponding lines to exercise ON/OFF control on the pMOS Ti3, nMOS Ti4, switch Ts, and switch Tg.
The sustaining control circuit 40, during a pre-discharge period 2 and a sustaining period 4 in each sub-field, in the same control methods as used in the case of
Also, the sustaining control circuit 40, during a period from ending time of a scanning pulse applying period in the scanning period 3 in each sub-field to ending time of a writing wall charge forming pulse applying period, feeds a control pulse to turn ON the PMOS Ti3 to the gate of the PMOS Ti3, a control pulse to turn OFF the nMOS Ti4 to the gate of the nMOS Ti4 and also feeds, during a period other than a writing wall charge forming pulse applying period, a control pulse to turn OFF the pMOS Ti3 to the gate of the pMOS Ti3 and a control pulse to turn ON the nMOS Ti4 to the gate of the nMOS Ti4.
Next, operations of the AC-type PDP of the embodiment of the present invention are described by referring to FIGS. 1 to 4. As in the case of the conventional operation, when a sustaining period 1 in a previous sub-field ends, the pre-discharge period 2 in the present sub-field starts. The pre-discharge period 2 is used, as in the conventional case, to reset charges (wall charges) accumulated by sustaining discharge in the previous sub-field on a dielectric layer and to make priming discharge occur so that writing discharge occurs easily.
In descriptions below, operations commonly performed by the scanning electrode Si, sustaining electrode Ci, and data electrode Dj are explained by using a scanning electrode Si, a sustaining electrode C1, and a data electrode D1 selected as a typical example. When an operation during the pre-discharge period 2 for the scanning electrode Si in
Wall charges formed during the sustaining period 1 in a previous sub-field are reset by the first sawtooth-like signal to be applied to the scanning electrode S1. Priming discharge occurs by the next sawtooth-like wave signal and wall charges formed by the priming discharge are adjusted.
A state of wall charges occurring after the resetting during the pre-discharge period 2 has been complete and the priming discharge operations have been performed and the scanning period 3 has started and before a scanning pulse is applied, as in the conventional case, is put into a state in which writing discharge can occur at a potential difference being a data pulse voltage “Vd”. As a result, a state as shown in
Writing operations are the same as those performed in the conventional case. That is, occurrence or non-occurrence of writing discharge is determined depending on whether or not a data pulse 7 is applied while a scanning pulse 6 is being applied. Writing is done when the writing discharge occurs. This operation is described more specifically below. When the scanning period 3 starts, a switch Tbw in the scanning power feeding circuit 144 is turned ON by the scanning control circuit 148 and a voltage “Vbw” is fed from the scanning power feeding circuit 144 and, during a scanning pulse applying period, the pMOS Ti1 is turned OFF and the nMOS T12 is turned ON and the scanning pulse 6 is applied to the scanning electrode S1.
When the scanning pulse 6 is applied to the scanning electrode S1, if the data pulse 7 is not applied to the data electrode D1, even if a voltage of a data pulse for the data electrode D1 is superimposed on a wall voltage being a voltage applied to dielectric layers 125 and 128 by wall charges, since a surface firing voltage or more is not applied to a facing discharge gap portion in discharge space 12611 between the scanning electrode S1 and data electrode D1, writing discharge does not occur.
When the scanning pulse 6 is applied to the scanning electrode S1, if the data pulse 7 is fed to the data electrode D1, since a negative wall voltage at the scanning electrode S1 and a positive wall voltage at the data electrode D1 are further superimposed on a voltage of the data pulse 7, a voltage being applied to the facing discharge gap portion in the discharge space 12611 exceeds the surface firing voltage, thus causing writing discharge to occur in the facing discharge gap portion in the discharge space 12611. When the writing discharge has occurred, as shown in
When images with high definition are displayed on a PDP, a method in which a width of a scanning pulse is shortened is employed, as described above, there appears a tendency in which easy formation of positive wall charges on the scanning electrode S1 and negative wall charges on the sustaining electrode C1 becomes difficult, which causes uncertain sustaining discharge to occur and a display cell to be not lit and/or a flicker to occur. However, according to the present invention, since a writing wall charge forming pulse 8 is applied to the sustaining electrode C1, positive wall charges and negative wall charges can be formed successfully on the scanning electrode S1 and on the sustaining electrode C1 respectively, which enables sustaining discharge to occur in a sustained manner. These operations are explained in detail below.
In the conventional driving method, when application of a scanning pulse is terminated, since a potential of the scanning electrode S1 is boosted to be “Vbw”, a potential difference between the scanning electrode S1 and sustaining electrode C1 decreases greatly from “Vs” to “Vs−Vbw”. However, according to the present invention, during a period from time of termination of the application of a scanning pulse to ending time of the writing wall charge forming pulse applying period, a control pulse is applied from the sustaining control circuit 40 to a gate of a PMOS T13 in the sustaining driver 36i to turn ON the pMOS T13 and, during the writing wall charge forming pulse applying period, a control pulse is fed from the sustaining control circuit 40 to a gate of an nMOS T14 to turn OFF the nMOS T14. The writing wall charge forming pulse applying period during which the writing wall charge forming pulse 8 is applied includes both the period necessary for formation of wall charges at time of writing, that is, a period during which wall charges are formed by movements of space charges after the end of a pulse application period during which a scanning pulse is applied and a period during which no erroneous discharge occurs.
Thus, since the writing wall charge forming pulse 8 is applied to the sustaining electrode C1 during the writing wall charge forming pulse applying period, during a period from the time of termination of the application of a scanning pulse to ending time of the writing wall charge forming pulse applying period, a potential difference between the scanning electrode S1 and sustaining electrode C1 continues to be “Vs+Vsw−Vbw” and a voltage being higher by “Vsw” than that employed in the conventional driving method is applied between the scanning electrode S1 and sustaining electrode C1.
As a result, even after termination of the application of the scanning pulse, movements of space charges between the surface electrodes continue and at time of termination of the application of the writing wall charge forming pulse 8, large amounts of positive wall charges are accumulated on the scanning electrode S1 as shown in
At the time of termination of the application of the writing wall charge forming pulse 8, in a state in which large amounts of positive wall charges have been accumulated on the scanning electrode S1 and large amounts of negative wall charges on the sustaining electrode C1, operations can start in the sustaining period 4. During the sustaining period 4, as in the conventional driving method, only when writing discharge occurs during the scanning period 3, large amounts of positive wall charges are formed in the vicinity of a surface discharge gap of the scanning electrode S1 and negative wall charges are formed in the vicinity of a surface discharge gap of the sustaining electrode C1 and, therefore, sustaining discharge occurs and a display cell is lit. Thus, lighting and non-lighting of the display cells can be controlled.
Next, set values of each of pulse voltages and set application time of each signal are described. During the pre-discharge period, “Vs” and “Vp” are set to be 160 V and 380 V, respectively, and a width of a slope of each sawtooth-like wave is set to be about 50 μsec. During the scanning period, “Vs” and “Vbw” are set to be 160 V and 110 V, respectively, and a width of the scanning pulse is set to be 1 μsec and a ground potential is used as a low voltage.
The writing wall charge forming pulse to be applied during the scanning period is set as follows. That is, when a pulse width of the writing wall charge forming pulse 8 is made longer from 0 μsec and exceeds about 2 μsec, both a voltage value “Vdsmin” being a minimum sustaining pulse that normally operated and a voltage value “Vdmin” being a minimum data pulse that normally operated begin to decrease rapidly and then until the pulse width becomes between 2 μsec to 3 μsec, tend to decrease gradually. Thereafter, even if the pulse width is made further longer, neither the voltage value “Vdsmin” being a minimum sustaining pulse nor the voltage value “Vdmin” being a minimum data pulse changes. When the pulse width of the writing wall charge forming pulse 8 is made longer, erroneous discharge occurs easily. Therefore, if the pulse width of the writing wall charge forming pulse 8 is made longer than necessary, a pulse voltage can not be made high. Thus, in the embodiment of the present invention, the pulse width of the writing wall charge forming pulse 8 is set to be 3 μsec to 5μsec and the pulse voltage is set to be 40 V to 120 V. The pulse voltage reaching about 140 V causes erroneous discharge to occur and, therefore, application of the pulse voltage exceeding the 140 V is not allowed.
A potential of the sustaining electrode C1 occurring when the writing wall charge forming pulse 8 is not applied is not necessarily set to be a sustaining pulse voltage value “Vs”, however, by setting the potential to be a voltage at which erroneous discharge does not occur between the scanning electrode S1 and sustaining electrode C1 at time of writing and to be as high as possible, negative wall charges can be formed easily on the sustaining electrode C1 when writing is done. In the embodiment, in order to use the power source in a shared manner, a potential of the sustaining electrode C1 occurring when the writing wall charge forming pulse 8 is not applied is set to be a sustaining pulse voltage “Vs”.
Next, effects obtained by applying the writing wall charge forming pulse 8 to the sustaining electrode C1 are described more specifically.
This relation is compared with that employed in the conventional driving method. That is, in the conventional driving method, when a pulse width of a scanning pulse is set to be 1 μsec, even if a sustaining pulse of 170 V is applied, lighting in a display cell did not occur. However, according to the driving method employed in the present invention, when the pulse width of the scanning pulse is set to be 1μsec, as in the conventional case, and a voltage value “Vsw” of a writing wall charge forming pulse is set at 80 V, a display cell can be lit at the sustaining pulse voltage “Vs” being 160 V.
As is apparent from the above description, in the driving method of the present invention, a sustaining pulse voltage value “Vs” is allowed to be decreased.
Also, according to the driving method of the present invention, it is possible to let a data pulse voltage value “Vd” be decreased.
This means that, by setting a writing wall charge forming pulse voltage value “Vsw” to be 80 V or more, the effect obtained by applying a pulse can be maximized. Thus, in a display cell of the present invention, if the “Vsw” is lowered to be 80 V, the effect by increasing the voltages “Vdsmin” or “Vdmin” using the writing wall charge forming pulse can be fully obtained. That is, by applying a potential difference exceeding a specified level between the scanning electrode and sustaining electrode for a specified period following termination of application of the scanning pulse, movements of charges are made to continue even after the application of the scanning pulse and, as a result, large amounts of wall charges can be formed between the scanning electrode and sustaining electrode.
This is described by using the concrete examples in the embodiment. That is, in the embodiment, “Vs”=160 V, “Vbw”=110 V, and “Vsw”=80 V and, therefore, after the termination of application of the scanning pulse, a voltage of 130 V is applied between the scanning electrode and sustaining electrode. In the state in which no wall charges exist between surface electrodes of the embodiment, since a surface firing voltage being a minimum potential difference at which discharge starts is about 190 V, the above voltage of 130 V makes up approximately two-thirds of 190 V being the surface firing voltage. Moreover, this voltage, as is apparent from the above description, is applied for a period during which no erroneous discharge occurs between the scanning electrode and sustaining electrode.
Thus, according to the embodiment, in the method for driving the address-display separated-type AC PDP, when a scanning pulse applying period starts, by applying a scanning pulse to the scanning electrode to which the voltage of “Vbw”=100 V and by applying a data pulse which is to be applied in synchronization with a scanning pulse to the data electrode, writing discharge occurs between the scanning electrode and data electrode in the display cell of the embodiment and positive wall charges are formed on the scanning electrode and negative wall charges on the sustaining electrode.
By applying, after the termination of application of the scanning pulse, a writing wall charge forming pulse having a voltage being higher by a voltage “Vsw” being 80 V than the voltage “Vs” being 160 V being applied to the sustaining electrode, further movements of space charges between the scanning electrode and sustaining electrode are made to continue so that positive wall charges sufficiently enough to make sustaining discharge occur are accumulated on the scanning electrode and sufficient negative wall charges are accumulated on the sustaining electrode and so that these wall charges having both a positive polarity and negative polarity, as in the conventional case, are exchanged among the scanning electrode, sustaining electrode, and sustaining electrode to turn ON a display cell. Therefore, it is possible to successfully solve technical problems occurring when a method by which an increase in a scanning period occurring when images with high definition are displayed is accommodated by shortening a period of applying a scanning pulse is employed, that is, technical problems that, though an increase in a minimum sustaining pulse voltage value “Vdsmin” at which normal operations can be performed and/or a minimum data pulse voltage value “Vdmin” at which normal operations can be performed can be suppressed, prevention of a voltage of a sustaining pulse and data pulse from becoming high cannot be easily achieved and accumulation of wall charges sufficiently enough to make sustaining discharge occur at time of terminating the application of the scanning pulse is difficult. Since the sustaining pulse and data pulse can be prevented from becoming high in voltage, power consumption can be reduced and a low-cost driver that cannot withstand comparatively high voltages is usable which reduces costs. Since such the effect as described above can be achieved, a shift of operations to reliable occurrence of sustaining discharge is made possible, which prevents no lighting of a display cell and/or occurrence of flickering in displaying.
That is, a sustaining control circuit 40A shown in
Next, operations of the driving device of the embodiment are described by referring to
After a specified period has elapsed following ending time of the scanning pulse applying period, a control pulse is applied from the sustaining control circuit 40A to the gate of the PMOS Ti3 in the sustaining driver 36i for a writing wall charge forming pulse applying period to turn ON the PMOS Ti3 and a control pulse is applied from the sustaining control circuit 40A to the gate of the nMOS Ti4 for a writing wall charge forming pulse applying period to turn OFF the nMOS Ti4.
As a result, a writing wall charge forming pulse 8 (see C1 in
Then, since the writing wall charge forming pulse 8 whose amplitude is “Vs+Vsw” is applied to the sustaining electrode C1 during the writing wall charge forming pulse applying period, a potential difference becomes “Vs+Vsw−Vbw” during the writing wall charge forming pulse applying period following the ending time of the scanning pulse applying period, a voltage being higher by a voltage “Vsw” than that employed in the conventional method is applied to the scanning electrode S1 and sustaining electrode C1.
As a result, even after termination of the application of the scanning pulse, movements of space charges between surface electrodes continue (see
Concrete set values for the writing wall charge forming pulse producing accumulation effects of wall charges are the same as those employed in the first embodiment. The effects produced by the writing wall charge forming pulse in that case are the same as those employed in the first embodiment shown in
In a state in which large amounts of positive wall charges are accumulated on the scanning electrode S1 and large amounts of negative wall charges on the sustaining electrode C1 at time of termination of the application of the writing wall charge forming pulse 8, operations start in the sustaining period 4. In the sustaining period 4, as in the conventional method, only when writing discharge occurred during the scanning period 3, large amounts of positive wall charges have been formed in the vicinity of the surface discharge gap on the scanning electrode S1 and large amounts of negative wall charges in the vicinity of the surface discharge gap on the sustaining electrode C1 and therefore sustaining discharge occurs and a display cell is put into a light-emitting state.
Thus, according to the driving method of the embodiment, by applying, from a lapse of time of less than 2μsec after the ending time of the scanning pulse applying period, a writing wall charge forming pulse to a sustaining electrode in the conventional driving method for the address-display separated-type AC PDP, the same effects as obtained in the first embodiment can be achieved in the present embodiment.
That is, a sustaining control circuit 40B shown in
Next, operations of the driving device are described by referring to
From specified time before ending of the scanning pulse applying period, a control pulse is applied from the sustaining control circuit 40B to the gate of the pMOS Ti3 in the sustaining driver 36, for the writing wall charge forming pulse applying period, to turn ON the PMOS Ti3 and a control pulse is applied from the sustaining control circuit 40B to the gate of the nMOS Ti4, for the writing wall charge forming pulse applying period, to turn OFF the nMOS Ti4. As a result, a writing wall charge forming pulse 8 (see C1 in
Time during which the scanning pulse 6 and the writing wall charge forming pulse 8 overlap is set to be 0.2 μsec to 0.5 μsec (this is specified above). If the above two pulses overlap for a period of time of 0.5 μsec or more, during the overlapped time, a potential difference between the surface electrodes becomes “Vs+Vsw”, erroneous discharge occurs between surface electrodes in some cases. When the overlapped time is made longer, the voltage “Vdsmin” decreases and the voltage drop stops in about 0.5 μsec. The voltage “Vdsmin” occurring when the scanning pulse 6 and writing wall charge forming pulse 8 overlap for0.5 μsec is decreased more by 5 V to 7 V than the voltage “Vdsmin” obtained when no overlapping occurred. The writing wall charge forming pulse applying period during which a writing wall charge forming pulse is applied is the same as employed in the first embodiment.
Then, since the writing wall charge forming pulse 8 whose voltage is “Vs+Vsw” is applied to the sustaining electrode C1 during the writing wall charge forming pulse applying period, a potential difference between the scanning electrode S1 and sustaining electrode C1 becomes “Vs+Vsw−Vbw” at specified time before ending time of the scanning pulse applying period, a voltage being higher by a voltage “Vsw” than that employed in the conventional method is applied to the scanning electrode S1 and sustaining electrode C1.
As a result, even after termination of the application of the scanning pulse, movements of space charges between surface electrodes continue (see
Concrete set values for the writing wall charge forming pulse producing accumulation effects of wall charges are the same as those employed in the first embodiment. The effects produced by the writing wall charge forming pulse in that case are the same as those employed in the first embodiment shown in FIGS. 5 and 6. This indicates that, by applying a potential difference having a specified level or more to the scanning electrode and sustaining electrode at specified time before termination of the application of a scanning pulse, movements of charges continues and large amounts of wall charges are formed on the scanning electrode and the sustaining electrode.
In a state in which large amounts of positive wall charges are accumulated on the scanning electrode S1 and large amounts of negative wall charges on the sustaining electrode C1 at time of termination of the application of the writing wall charge forming pulse 8, operations start in the sustaining period 4. In the sustaining period 4, as in the conventional method, only when writing discharge occurred during the scanning period, large amounts of positive wall charges have been formed in the vicinity of the surface discharge gap on the scanning electrode S1 and large amounts of negative wall charges in the vicinity of the surface discharge gap on the sustaining electrode C1 and, therefore, sustaining discharge occurs and a display cell is put into a light-emitting state.
Thus, according to the driving method of the embodiment, by applying, from 0.2 μsec to 0.5 μsec before ending time of the scanning pulse applying period, a writing wall charge forming pulse to a sustaining electrode in the conventional driving method for the address-display separated-type AC PDP, the same effects as obtained in the first embodiment can be achieved.
A sustaining driver 36 shown in
The sustaining base voltage “Vsw′” is a voltage which is lower than a writing wall charge forming pulse voltage “Vsw” and which can sufficiently form a wall charge even after termination of application of a scanning pulse and which does not cause occurrence of erroneous discharge even if the sustaining base voltage is applied during the scanning period 3. A period during which a voltage value “Vsw′” being the sustaining base voltage is applied to the sustaining electrode Ci is the scanning period 3 from which the scanning pulse applying period is excluded.
The sustaining control circuit 40C feeds, from a last half period (during which a positive pulse is applied) during which a last sustaining pulse is being applied in a specified period to the sustaining electrode S1 during a sustaining period 1 in a previous sub-field to ending time of a period during which a first sawtooth wave signal is applied to the scanning electrode S1, a control pulse to turn ON the switch Ts to the switch Ts and also a control pulse to turn OFF the switches Tn, Tp, Tsw, and Tg to an ON/OFF control inputting port of each of the switches Tn, Tp, Tsw, and Tg. The sustaining control circuit 40C also feeds, from ending time of a period during which a first sawtooth wave signal is applied to the scanning electrode Si to ending time of a period during which a second sawtooth wave signal is applied to the scanning electrode Si, a control pulse to turn OFF the switch Tn, Ts, and Tsw to the ON/OFF control inputting port of each of the switches Tn, Ts, and Tsw and also a control pulse to turn ON the switch Tp and Tg to the ON/OFF control inputting port of each of the switches Tp and Tg.
Also, the sustaining control circuit 40C feeds, until ending time of a period during which a second sawtooth wave signal is applied to the sustaining electrode Ci, that is, until ending time of the scanning period 3 from starting time of a period during which a last sawtooth wave signal is applied to the sustaining electrode Ci, a control pulse to turn ON the switch Ts to the ON/OFF control inputting port of the switch Ts and also a control pulse to turn ON the switch Tsw to the ON/OFF control inputting port of the Tsw during the scanning period 3. On the other hand, the sustaining control circuit 40C feeds, at starting time of the scanning period 3, a control pulse to turn ON the switches Tn and Tp to the ON/OFF control inputting port of each of the switches Tn and Tp and also feeds, immediately before a scanning pulse is applied to any one of scanning electrodes, a control pulse to turn OFF the switches Tn and Tp to the ON/OFF control inputting port of each of the switches Tn and Tp and, at time of termination of the application of a scanning pulse, a control pulse to turn ON the switches Tn and Tp to the ON/OFF control inputting port of each of the switches Tn and Tp.
Also, the sustaining control circuit 40C feeds, for a period from ending time of the scanning period 3 through the sustaining period 4, a control pulse to turn OFF the switches Tn and Tsw to the ON/OFF control inputting port and, during the sustaining period 4, a control pulse to turn ON the switch Tp to the ON/OFF control inputting port of the switch Tp and, from starting time of the sustaining period 4 and for a first half of a period during which a sustaining pulse is being applied, a control pulse to turn ON the switch Tg and a control pulse to turn OFF the switch Ts and for a second half of a period during which the sustaining pulse is being applied, a control pulse to turn OFF the switch Tg and a control pulse to turn ON the switch Ts to the ON/OFF control inputting port of the switch Tg and the ON/OFF control inputting port of the switch Ts alternately for every half of the period during which the sustaining pulse is being applied. Configurations of each component of the fourth embodiment are the same as those in the first embodiment except the difference described above and same reference numbers are assigned to components having the same function as those in the first embodiment and their descriptions are omitted accordingly.
Next, operations of the driving device of the embodiment are described by referring to
In this state, let it be assumed that an operation for the first scanning line of a video signal is started. Immediately before the scanning pulse 6 is applied, as in the conventional method, to the scanning electrode S1 corresponding to the scanning line, the sustaining control circuit 40C feeds a control pulse to turn OFF the switches Tn and Tp to the switches Tn and Tp (see Tn and Tp in
Immediately after that, when a scanning pulse is applied to the scanning electrode S1 (see S1 in
Then, at termination time of the application of the above scanning pulse 6, the sustaining control circuit 40C feeds a control pulse to turn ON the switches Tn and Tp to the switches Tn and Tp (see Tn and Tp in
As in the case of the first embodiment, by the application of the sustaining base voltage 9 to the sustaining electrode C1, sufficient positive wall charges are accumulated on the scanning electrode corresponding to every display cell in which the above writing discharge has occurred, out of the display cells 13111, to 1311n, and sufficient negative wall charges are accumulated on the sustaining electrode of the display cell.
In the similar manner, an operation for the second scanning line starts and immediately before the scanning pulse 6 is applied to the scanning electrode S2, the sustaining control circuit 40C feeds a control pulse to turn OFF the switches Tn and Tp to the switches Tn and Tp (see Tn and Tp in
As in the first embodiment, a scanning pulse is applied to the scanning electrode S2 and in a state that the potential of the sustaining electrode C2 is lowered to be “Vs”, a data pulse corresponding to a pixel is sequentially applied to data electrodes D1 to Dn and writing discharge corresponding to a data pulse occurs in each of display cells 13121 to 1312n.
Then, at time of termination of the application of the scanning pulse 6 that was applied to the scanning electrode S2, the sustaining control circuit 40C feeds a control pulse to turn ON the switches Tn and Tp to the switches Tn and Tp (see Tn and Tp in
As in the case of the first embodiment, by the application of the sustaining base voltage 9 to the sustaining electrode C2, sufficient positive wall charges are accumulated on the scanning electrode corresponding to every display cell in which the above writing discharge has occurred, out of the display cells 13121 to 1312n, and sufficient negative wall charges are accumulated on the sustaining electrode of the display cell.
Hereinafter, same operations as above are repeated for every scanning line. In any one of the operations, before the scanning pulse 6 is applied to the scanning electrode corresponding to the scanning line, when each of the sustaining electrodes is put into a floating state and the scanning pulse 6 is applied to the scanning electrode corresponding to the scanning line, a potential of the scanning electrode being paired with the scanning electrode corresponding to the scanning line is lowered to be “Vs”.
Furthermore, as in the case of the first embodiment in the operations repeated as above, a scanning pulse is applied to the scanning electrode and a potential of the sustaining electrode corresponding to the scanning electrode is lowered to be “Vs”. In this state, a data pulse corresponding to a pixel is fed sequentially to data electrodes D1 to Dn and writing discharge corresponding to the data pulse occurs in each of display cells 131il to 13in. (here, “i”, denotes a scanning line on which an operation is performed). Then, at termination time of the application of the scanning pulse 6, the potential of the sustaining electrode corresponding to the above scanning electrode again becomes “Vsw′+Vs” and, by the application of the sustaining base voltage 9 to the sustaining electrode, sufficient positive wall charges are accumulated on the scanning electrode for every display cell, out of the display cells 131il, to 131in, in which the above writing discharge occurs and sufficient negative wall charges are accumulated on the sustaining electrode for the display cell.
As described above, in the fourth embodiment, unlike in the case of the above first to third embodiments, the sustaining base voltage 9 to be applied to any sustaining electrodes Ci has been fed to the sustaining electrode also before the application of the scanning pulse. In the fourth embodiment, the sustaining base voltage 9 (Vsw′) is set to be 20 V to 100 V. When the sustaining base voltage 9 is set to be 120 V, erroneous discharge occurred. Even if the sustaining base voltage 9 is applied before the application of the scanning pulse 6, an increase in the voltage value “Vdsmin” of the sustaining pulse voltage. “Vs” at which normal operations can be performed could not be suppressed. However, when the sustaining base voltage 9 is fed after the application of the scanning pulse 6 and the sustaining base voltage 9 is set to be high, as in the case of the first to third embodiments, there was a tendency that the sustaining pulse voltage “Vdsmin” at which normal operations can be performed and the voltage “Vdmin” of the data pulse at which normal operations can be performed were decreased.
That is, it can be thought that, in the scanning period other than a period during which a scanning pulse is not applied, when a potential which has a voltage exceeding a specified voltage level and at which no erroneous discharge occurs is applied between the scanning electrode and sustaining electrode, movements of charges continue ever after the application of a scanning pulse and large amounts of wall charges are formed on the scanning electrode and sustaining electrode.
Thus, according to the driving method of the fourth embodiment, in the conventional driving method for the address-display separated-type AC plasma display panel, also by applying a sustaining base voltage to a sustaining electrode to which a scanning pulse is being applied, the same effects as obtained in the first embodiment can be achieved. Moreover, in the first embodiment, the sustaining driver corresponding to the number of the sustaining electrodes is required, however, in the fourth embodiment, since the switches Tsw, Tn, and Tp can be used commonly for each of the sustaining electrodes, it is made possible to simplify configurations of the sustaining driver and to reduce related costs.
That is, a sustaining driver 360 drives the odd-numbered sustaining electrodes C2K-1(k is one of 1, 2, . . . , m) and a sustaining driver 36E drives the even-numbered sustaining electrodes C2k. The sustaining driver 360 has a pMOS Tc1 and an nMOS Tc2 and the sustaining driver 36E has a pMOS Tc3 and an nMOS Tc4. Switches Ts and Tg are used commonly for the sustaining driver 360 and the sustaining driver 36E, which exercise ON/OFF control on the PMOS Tc1 and nMOS Tc2 for the sustaining driver 360 and on the pMOS T3 and the nMOS T4 for the sustaining driver 36E. A sustaining control circuit 40D exercises ON/OFF control on the switches Ts and Tg.
The sustaining control circuit 40D feeds, from a last half of a period during which a last sustaining pulse is applied to the odd-numbered and even-numbered sustaining electrodes in a sustaining period in a previous sub-field to time at which a scanning pulse is applied to the odd-numbered and even-numbered scanning electrodes, a control pulse to turn ON the nMOS Tc2 and nMOS Tc4 to the nMOS Tc2 and nMOS Tc4. The sustaining control circuit 40D also feeds, from a last half of a period during which a last sustaining pulse is applied to the odd-numbered and even-numbered sustaining electrodes in a sustaining period in a previous sub-field to ending time of a period during which a first sawtooth-like wave signal is applied to the odd-numbered and even-numbered scanning electrodes, a control pulse to turn ON the switch Ts to an ON/OFF control inputting port of the switch Ts and a control pulse to turn ON the switch Tg to an ON/OFF control inputting port of the switch Tg and, from a last half of a period during which the above last sustaining pulse is applied to time at which a scanning pulse is applied to the odd-numbered and even-numbered scanning electrodes, a control pulse to turn ON the pMOS Tc1 and pMOS Tc3 to a gate of each of the pMOS Tc1 and the pMOS Tc3.
Also, the sustaining control circuit 40D feeds, from ending time of a period during which a first sawtooth-like wave signal is applied to the odd-numbered and even-numbered scanning electrodes to ending time a period during which a second sawtooth-wave signal is applied, a control pulse to turn OFF the switch Ts to an ON/OFF control inputting port of the switch Ts and a control pulse to turn ON the switch Tg to an ON/OFF control inputting port of the switch Tg.
Also, the sustaining control circuit 40D feeds, from ending time of a period during which the second sawtooth-like wave signal to ending time of the scanning period 3, a control pulse to turn ON the switch Ts to the ON/OFF control inputting port of the switch Ts and a control pulse to turn OFF the switch Tg to the ON/OFF control inputting port of the switch Tg.
Also, the sustaining control circuit 40D feeds, in a period during which odd-numbered sustaining electrodes C2k-1 in the scanning period are driven, a control pulse to turn OFF the pMOS Tc3 of the sustaining driver 36E to a gate of the pMOS Tc3 and a control pulse to turn OFF the nMOS Tc4 to a gate of the nMOS Tc4.
Also, the sustaining control circuit 40D feeds, every time when a writing wall charge forming pulse is applied to the odd-numbered sustaining electrode C2k-1 whenever the application of a scanning pulse to the odd-numbered scanning electrode ends, a control pulse to turn ON the PMOS Tc1 of the sustaining driver 360 to a gate of the PMOS Tc1 and a control pulse to turn OFF the nMOS Tc2 to a gate of the nMOS Tc2.
Also, the sustaining control circuit 40D feeds, from ending time of a period during which a last writing wall charge forming pulse is applied to the odd-numbered sustaining electrode C2k-1 to ending time of the scanning period, a control pulse to turn OFF the PMOS Tc1 of the sustaining driver 360 to the gate of the PMOS Tc1 and a control pulse to turn ON the nMOS Tc2 to the gate of the nMOS Tc2.
Also, the sustaining control circuit 40D feeds, for a period during which the even-numbered sustaining electrode C2k in the scanning period is driven, a control pulse to turn OFF the PMOS Tc1 of the sustaining driver 360 to the gate of the PMOS Tc1 and a control pulse to turn OFF the nMOS Tc2 to the gate of the nMOS Tc2.
Also, the sustaining control circuit 40D feeds, every time when a writing wall charge forming pulse is applied to the even-numbered sustaining electrode C2k whenever the application of a scanning pulse to the even-numbered scanning electrode ends, a control pulse to turn ON the PMOS Tc3 of the sustaining driver 36E to the gate of the pMOS Tc3 and a control pulse to turn OFF the nMOS Tc4 to the gate of the nMOS Tc4.
Also, the sustaining control circuit 40D feeds, from ending time of a period during which a last writing wall charge forming pulse is applied to the even-numbered sustaining electrodes C2k to ending time of the scanning period, a control pulse to turn OFF the pMOS Tc3 of the sustaining driver 36E to the gate of the pMOS Tc3 and a control pulse to turn ON the nMOS Tc4 to the gate of the nMOS Tc4.
Moreover, the sustaining control circuit 40D repeats operations, alternately in every half of a period during which a sustaining pulse is applied, that it feeds, for a first half of the period during which a sustaining pulse (negative pulse) is applied to a sustaining electrode in a certain period in a sustaining period, a control pulse to turn OFF the switch Ts to the ON/OFF control inputting port of the switch Ts and a control pulse to turn ON the switch Tg to the ON/OFF control inputting port of the switch Tg and that it feeds, for a last half of the period during which a sustaining pulse (positive pulse) is applied, a control pulse to turn ON the switch Ts to the ON/OFF control inputting port of the switch Ts and a control pulse to turn OFF the switch Tg to the ON/OFF control inputting port of the switch Tg. Configurations of each component of the fifth embodiment are the same as those in the first embodiment except the difference described above and same reference numbers are assigned to components having the same function as those in the first embodiment and their descriptions are omitted accordingly.
Next, operations of the driving method employed in the fifth embodiment are described by referring to
That is, the sustaining control circuit 40D, from ending time of a period during which a scanning pulse is applied to the odd-numbered scanning electrodes C2k-1 and for a period during which a writing wall charge forming pulse is applied, feeds a control pulse to the gate of the PMOS Tc1 to turn ON the pMOS Tc1 and a control pulse to the gate of the nMOS Tc2 to turn OFF the nMOS Tc2. Also, the sustaining control circuit 40D, as in the case of the first embodiment, from time at which application of a last sawtooth-wave signal starts to ending time of the scanning period 3, feeds a control pulse to turn ON the switch Ts to the switch Ts.
Then, the sustaining control circuit 40D, at time of termination of a period during which the writing wall charge forming pulse is applied, feeds a control pulse to the gate of the PMOS Tc1 to turn OFF the PMOS Tc1 of the sustaining driver 360 and another control pulse to the gate of the nMOS Tc2 to turn ON the nMOS Tc2.
Similarly, the sustaining control circuit 40D, from ending time of a period during which a scanning pulse is applied to the even-numbered scanning electrodes C2k-1 and for a period during which a writing wall charge forming pulse is applied, feeds a control pulse to the gate of the pMOS Tc3 to turn ON the PMOS Tc3 of the sustaining driver 36E and a control pulse to the gate of the nMOS Tc4 to turn OFF the nMOS Tc4.
Then, the sustaining control circuit 40D, at ending time of a period during which the writing wall charge forming pulse is applied, feeds a control pulse to the gate of the pMOS Tc3 to turn OFF the pMOS Tc3 of the sustaining driver 36E and another control pulse to the gate of the nMOS Tc4 to turn ON the nMOS Tc4.
Therefore, from ending time of a period during which a scanning pulse is applied to the sustaining electrode corresponding to the scanning line for a video signal, a writing wall charge forming pulse is applied to the sustaining electrode (hereafter called a sustaining electrode being scanned) being paired with the scanning electrode to which a scanning pulse has been applied (hereafter called a scanning electrode being scanned). When a data pulse was applied to the data electrode corresponding to the above scanning electrode being scanned prior to the application of the writing wall charge forming pulse to the sustaining electrode being scanned and if writing charge occurred then in the display cell, as in the case of the first embodiment, even after the time of termination of the application of the scanning pulse, movements of space charges between surface electrodes continue in the display cell (see
As a result, operations can be started in the sustaining period 4 in a state in which, at time of termination time of application of the writing wall charge forming pulse 8, large amounts of positive wall charges are accumulated on the scanning electrode being scanned and large amounts of negative wall charges are accumulated on the sustaining electrode being scanned and, therefore, in the sustaining period 4, as in the conventional case, discharge occurs and the display cell is put into a lit state. By operating as above, control on lighting and non-lighting of the display cell can be exercised.
Thus, according to the driving method of the fourth embodiment, in the conventional driving method for the address-display separated-type AC plasma display panel, by driving an odd-numbered sustaining electrode using the sustaining driver being commonly used in each of the odd-numbered sustaining electrodes and by driving an even-numbered sustaining electrode using the sustaining driver being commonly used in each of the even-numbered sustaining electrodes, the same effects as obtained in the first embodiment can be achieved. Also, in the first embodiment, the sustaining drivers corresponding to the number of sustaining electrodes are required, however, in the fifth embodiment, the sustaining driver being commonly used in the odd-numbered sustaining electrodes and the sustaining driver being commonly used in the even-numbered sustaining electrodes may be mounted and, therefore, the sustaining driver can be greatly simplified and costs of the sustaining driver can be reduced.
It is apparent that the present invention is not limited to the above embodiments but may be changed and modified without departing from the scope and spirit of the invention. For example, the surface firing voltage varies depending on dimensions of an electrode, interval of an electrode, discharge gas, dielectric layer, or a like and, therefore, a value other than those shown in the above embodiments may be used. Similarly, a width of a writing wall charge forming pulse, relation of application time between the scanning pulse and writing wall charge forming pulse, overlapping of the scanning pulse and writing wall charge forming pulse while being applied, sustaining base voltage also vary depending on conditions such as a kind of gas, gas pressure and, therefore, a value other than those described in the embodiments may be employed. Any switch, so long as it is of an electronic type, may be used. In the first, second, third and fifth embodiments, an amplitude of the writing wall charge forming pulse and of the sustaining pulse are set to be the same, however, if common use of the power source is not considered, the amplitudes may be different from each other. Moreover, in order to facilitate of formation of wall charges, the amplitude of the sustaining pulse is preferably made large.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-320461 | Sep 2002 | JP | national |
