JP2006184486A - Display device and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of displaying more luminance levels and its driving method. <P>SOLUTION: A ramp waveform La2 is applied to a scan electrode 12 in a sustaining period of a first sub-field SF1. A total cell initialization waveform Setup2 having ramp waveforms La3, La4 are applied in a total cell initialization period of a second sub-field SF2. The ramp waveform La2 and the ramp waveform La3 are continuously applied. As a result, the voltage of the scan electrode 12 rises gently and linearly from 0V up to Vset. The voltage change rate of the ramp waveform La2 is regulated so that the light emission luminance level of the discharge cell 14 in the sustaining period of the first sub-field SF1 is made into l/4 of the light emission luminance level of the discharge cell 14 in the sustaining period of the second sub-field SF2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device that displays an image by controlling discharge and a driving method thereof.

  A plasma display device using a PDP (plasma display panel) has an advantage that it can be made thin and have a large screen. In this plasma display device, an image is displayed by using light emission during gas discharge.

  FIG. 8 is a diagram for explaining a method of driving a discharge cell in the AC type PDP. As shown in FIG. 8, in the discharge cell of the AC type PDP, the surfaces of the opposing electrodes 301 and 302 are covered with dielectric layers 303 and 304, respectively.

  As shown in FIG. 8A, when a voltage lower than the discharge start voltage is applied between the electrodes 301 and 302, no discharge occurs. As shown in FIG. 8B, when a pulse voltage (writing pulse) higher than the discharge start voltage is applied between the electrodes 301 and 302, discharge occurs. When discharge occurs, negative charges travel in the direction of the electrode 301 and accumulate on the wall surface of the dielectric layer 303, and positive charges travel in the direction of the electrode 302 and accumulate on the wall surface of the dielectric layer 304. The charges accumulated on the wall surfaces of the dielectric layers 303 and 304 are called wall charges. The voltage induced by this wall charge is called a wall voltage.

  As shown in FIG. 8C, negative wall charges are accumulated on the wall surface of the dielectric layer 303, and positive wall charges are accumulated on the wall surface of the dielectric layer 304. In this case, since the polarity of the wall voltage is opposite to the polarity of the externally applied voltage, the effective voltage in the discharge space decreases as the discharge progresses, and the discharge automatically stops.

  As shown in FIG. 8D, when the polarity of the externally applied voltage is reversed, the wall voltage has the same polarity as the polarity of the externally applied voltage, so that the effective voltage in the discharge space increases. When the effective voltage exceeds the discharge start voltage, reverse polarity discharge occurs. As a result, the positive charge proceeds in the direction of the electrode 301, neutralizes the negative wall charge already accumulated in the dielectric layer 303, and the negative charge proceeds in the direction of the electrode 302, and is already accumulated in the dielectric layer 304. Neutralizes positive wall charges.

  As shown in FIG. 8E, positive and negative wall charges are accumulated on the wall surfaces of the dielectric layers 303 and 304, respectively. In this case, since the polarity of the wall voltage is opposite to the polarity of the externally applied voltage, the effective voltage in the discharge space decreases as the discharge progresses, and the discharge stops.

  Further, as shown in FIG. 8 (f), when the polarity of the externally applied voltage is reversed, a discharge of reverse polarity occurs, the negative charge proceeds in the direction of the electrode 301, the positive charge proceeds in the direction of the electrode 302, Returning to the state of FIG.

  In this way, after the discharge is once started by applying an address pulse higher than the discharge start voltage, the polarity of the externally applied voltage (sustain pulse) lower than the discharge start voltage is reversed by the action of wall charges. Thus, the discharge can be sustained. Starting discharge by applying an address pulse is called address discharge, the period during which address discharge is performed is called an address period, and sustaining discharge by applying alternately inverted sustain pulses is called sustain discharge. A period during which sustain discharge is performed is referred to as a sustain period.

  FIG. 9 is a schematic diagram showing a configuration of a PDP (plasma display panel) mainly of a conventional plasma display apparatus.

  As shown in FIG. 9, the PDP 1 includes a plurality of address electrodes 11, a plurality of scan electrodes (scan electrodes) 12, and a plurality of sustain electrodes (sustain electrodes) 13. The plurality of address electrodes 11 are arranged in the vertical direction of the screen, and the plurality of scan electrodes 12 and the plurality of sustain electrodes 13 are arranged in the horizontal direction of the screen. The plurality of sustain electrodes 13 are connected in common.

  A discharge cell is formed at each intersection of the address electrode 11, the scan electrode 12 and the sustain electrode 13. Each discharge cell constitutes a pixel on the screen.

  The data driver 2 drives the plurality of address electrodes 11 according to the image data. The scan driver 3 drives the plurality of scan electrodes 12 in order. The sustain driver 4 drives the plurality of sustain electrodes 13 in common.

  FIG. 10 is a schematic cross-sectional view of a three-electrode surface discharge cell in an AC type PDP.

  In the discharge cell 200 shown in FIG. 10, a pair of scan electrode 12 and sustain electrode 13 are formed on the surface glass substrate 201 in the horizontal direction of the screen, and the scan electrode 12 and sustain electrode 13 are formed of the transparent dielectric layer 202. And a protective layer 203. On the other hand, the address electrode 11 is formed in the vertical direction of the screen on the back glass substrate 204 facing the front glass substrate 201, and the transparent dielectric layer 205 is formed on the address electrode 11. A fluorescent material 206 is applied on the transparent dielectric layer 205.

  In this discharge cell 200, an address discharge is generated between the address electrode 11 and the scan electrode 12 by applying a write pulse between the address electrode 11 and the scan electrode 12, and then the scan electrode 12, the sustain electrode 13, A sustain discharge is performed between the scan electrode 12 and the sustain electrode 13 by applying a periodic sustain pulse that is alternately inverted between the scan electrode 12 and the sustain electrode 13.

  As a gray scale display driving method in the AC type PDP, an address and display-separated (ADS) that separates an address period in which address discharge is performed and a sustain period in which sustain discharge is performed to discharge discharge cells. A method is used (see, for example, Patent Document 1).

  FIG. 11 is a diagram for explaining the ADS system. The vertical axis in FIG. 11 indicates the scanning direction (vertical scanning direction) of the scan electrodes from the first line to the m-th line, and the horizontal axis indicates time.

  In the ADS system, one field (1/60 seconds = 16.67 ms) is temporally divided into a plurality of subfields. For example, when 256 gradation display is performed with 8 bits, one field is divided into eight subfields. Each subfield is divided into an address period in which address discharge for selecting a lighted cell is performed and a sustain period (light emission period) in which sustain discharge for display is performed.

  In the example of FIG. 11, one field is temporally divided into four subfields SF1, SF2, SF3, and SF4. Subfield SF1 is separated into address period AD1 and sustain period SUS1, subfield SF2 is separated into address period AD2 and sustain period SUS2, and subfield SF3 is separated into address period AD3 and sustain period SUS3. SF4 is separated into an address period AD4 and a sustain period SUS4.

  In the ADS system, scanning is performed on the entire surface of the PDP from the first line to the m-th line in each subfield, and sustain discharge is performed at the end of the address discharge on the entire surface of the PDP.

  In the ADS system, gradation display can be performed by selecting a sustain period during which the PDP discharge cells are turned on.

  FIG. 12 is a timing chart showing an example of a drive voltage applied to each electrode of a conventional AC type PDP.

  The timing chart of FIG. 12 shows the drive voltage of one address electrode 11 arranged in the vertical direction of the PDP 1, the drive voltage of one scan electrode 12 intersecting with the address electrode 11, and the drive of one sustain electrode 13. The voltage is shown.

  In the example of FIG. 12, the first and second sub-fields SF1 and SF2 of each field are shown.

  The first subfield SF1 includes a first selective initialization period for generating a weak discharge in the discharge cells discharged in the sustain period of the last subfield of the previous field to uniformly adjust the wall charge. An address period in which an address pulse is applied to the address electrode 11 and the scan electrode 12 to perform an address discharge, a sustain period in which a sustain voltage is applied to the scan electrode 12 and the sustain electrode 13 and a sustain discharge is performed, and the first subfield SF1 The second selective initialization period for generating a weak discharge in the discharge cells discharged in the sustain period to uniformly adjust the wall charge.

  The second subfield SF2 includes an all-cell initializing period for generating a weak discharge in all discharge cells to uniformly adjust wall charges, an address period for performing address discharge, and a sustain period for performing sustain discharge. Composed.

  In the example of FIG. 12, first, the selective initialization waveform Setup 10 having the ramp waveform La11 is applied to the scan electrode 12 by the scan driver 3 in the first selective initialization period of the first subfield SF1. Further, the voltage of the address electrode 11 is held at 0 V by the data driver 2, and the voltage of the sustain electrode 13 is held at Ve by the sustain driver 4.

  When the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La11, the discharge cells that have been sustain-discharged in the sustain period of the last subfield of the previous field and between the scan electrode 12 and the address electrode 11 and the scan A weak discharge is generated between the electrode 12 and the sustain electrode 13. As a result, a predetermined amount of positive wall charge is accumulated in the address electrode 11, a predetermined amount of negative wall charge is accumulated in the scan electrode 12, and a predetermined amount of positive wall charge is accumulated in the sustain electrode 13. As a result, the wall charges of all the discharge cells are adjusted almost uniformly.

  Next, in the address period of the first subfield SF1, the data driver 2 applies a positive write pulse Pw to the address electrode 11 corresponding to the discharge cell to be lit. Further, the scan driver 3 applies a negative write pulse Ps to the scan electrode 12 in synchronization with the write pulse Pw.

  In this case, the effective voltage between the address electrode 11 and the scan electrode 12 corresponding to the discharge cell to be lit is the potential difference between the write pulse Pw and the write pulse Ps at the end of the first selective initialization period. This is a value obtained by adding the wall voltage due to the wall charges accumulated in each of the scan electrode 12 and the address electrode 11.

  Accordingly, since the effective voltage between the address electrode 11 and the scan electrode 12 exceeds the discharge start voltage, an address discharge is generated between the address electrode 11 and the scan electrode 12, and the scan electrode 12 and the sustain electrode 13 Discharge occurs between them. As a result, positive wall charges are accumulated in the scan electrode 12 and negative wall charges are accumulated in the address electrode 11. Further, negative wall charges are accumulated in the sustain electrode 13.

  On the other hand, when the write pulse Pw is not applied to the address electrode 11 in the address period, the effective voltage between the address electrode 11 and the scan electrode 12 does not exceed the discharge start voltage. No address discharge occurs in the discharge cell at the intersection.

  Next, in the sustain period of the first subfield SF1, the scan driver 3 raises the voltage of the scan electrode 12 to Vm. At this time, the sustain driver 4 sets the voltage of the sustain electrode 13 to 0V.

  In this case, the effective voltage between the scan electrode 12 and the sustain electrode 13 corresponding to the discharge cell to be lit is the potential difference Vm between the scan electrode 12 and the sustain electrode 13, and the scan electrode 12 and the sustain electrode in the address period. 13 is a value obtained by adding the wall voltage due to the wall charges accumulated in each of 13.

  Accordingly, since the effective voltage between the scan electrode 12 and the sustain electrode 13 exceeds the discharge start voltage, a sustain discharge is generated between the scan electrode 12 and the sustain electrode 13. As a result, negative wall charges are accumulated on the scan electrode 12 and positive wall charges are accumulated on the sustain electrode 13.

  On the other hand, the effective voltage between the scan electrode 12 and the sustain electrode 13 in the discharge cell that did not cause the address discharge because the write pulse Pw is not applied does not exceed the discharge start voltage. Therefore, no sustain discharge occurs between the scan electrode 12 and the sustain electrode 13.

  Next, in the second selective initialization period of the first subfield SF1, the scan driver 3 applies the selective initialization waveform Setup 20 having the ramp waveform La12 to the scan electrode 12. Further, the sustain driver 4 holds the voltage of the sustain electrode 13 at Ve. When the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La12, the discharge cell that has been sustain-discharged in the sustain period of the first subfield SF1 and between the scan electrode 12 and the address electrode 11 and the scan electrode A weak discharge is generated between the electrode 12 and the sustain electrode 13. As a result, the wall charges of all the discharge cells are adjusted almost uniformly.

  Thus, the first subfield SF1 is completed. At the end of the first subfield SF1, negative wall charges are accumulated in the scan electrode 12, and positive wall charges are accumulated in the sustain electrode 13. Further, positive wall charges are accumulated in the address electrode 11.

  Next, in the all-cell initializing period of the second subfield SF2, the scan driver 3 applies the all-cell initializing waveform Setup30 having the ramp waveforms La13 and La14 to the scan electrode 12.

  In the all-cell initialization period, first, the scan driver 3 raises the voltage of the scan electrode 12 to Vm, and the sustain driver 4 sets the voltage of the sustain electrode 13 to the ground voltage 0V.

  Thereafter, the voltage of the scan electrode 12 is gradually increased to Vset by the ramp waveform La13. At this time, the voltage of the sustain electrode 13 is held at 0V. Thereby, a weak discharge is generated between the scan electrode 12 and the address electrode 11 and between the scan electrode 12 and the sustain electrode 13 in all the discharge cells. As a result, negative wall charges are accumulated in the scan electrode 12 and positive wall charges are accumulated in the address electrode 11 and the sustain electrode 13.

  Next, the scan driver 3 decreases the voltage of the scan electrode 12 to Vm, and the sustain driver 4 increases the voltage of the sustain electrode 13 to Ve.

  Thereafter, the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La14. At this time, the voltage of the sustain electrode 13 is held at Ve. Thereby, a weak discharge is generated between the scan electrode 12 and the address electrode 11 and between the scan electrode 12 and the sustain electrode 13 in all the discharge cells. As a result, the negative wall charges of the scan electrode 12 and the positive wall charges of the address electrode 11 and the sustain electrode 13 are reduced.

  In the discharge cell after the all-cell initialization period, a predetermined amount of positive wall charge is accumulated in the address electrode 11, a predetermined amount of negative wall charge is accumulated in the scan electrode 12, and a predetermined amount of positive wall charge is accumulated in the sustain electrode 13. Wall charges are accumulated. As described above, the amount of wall charges of all the discharge cells is adjusted uniformly.

  Next, in the address period of the second subfield SF2, the data driver 2 applies a positive write pulse Pw to the address electrode 11 corresponding to the discharge cell to be lit. Further, the scan driver 3 applies a negative polarity write pulse Ps to the scan electrode 12 in synchronization with the write pulse Pw.

  In this case, the effective voltage between the address electrode 11 and the scan electrode 12 corresponding to the discharge cell to be lit is the potential difference between the write pulse Pw and the write pulse Ps, at the end of the all-cell initialization period. And the wall voltage due to the wall charges accumulated in each of the address electrodes 11 is added.

  Accordingly, since the effective voltage between the address electrode 11 and the scan electrode 12 exceeds the discharge start voltage, an address discharge is generated between the address electrode 11 and the scan electrode 12, and the scan electrode 12 and the sustain electrode 13 Discharge occurs between them. As a result, positive wall charges are accumulated in the scan electrode 12 and negative wall charges are accumulated in the address electrode 11. Further, negative wall charges are accumulated in the sustain electrode 13.

  Next, in the sustain period of the second subfield SF2, first, the scan driver 3 raises the voltage of the scan electrode 12 to Vm, and the sustain driver 4 sets the voltage of the sustain electrode 13 to 0V. As a result, a first sustain discharge occurs between the scan electrode 12 and the sustain electrode 13. As a result, negative wall charges are accumulated on the scan electrode 12 and positive wall charges are accumulated on the sustain electrode 13.

  Next, the scan driver 3 sets the voltage of the scan electrode 12 to the ground voltage 0 V, and the sustain driver 4 raises the voltage of the sustain electrode 13 to Vm. As a result, a second sustain discharge occurs between the scan electrode 12 and the sustain electrode 13. As a result, positive wall charges are accumulated on the scan electrode 12 and negative wall charges are accumulated on the sustain electrode 13.

  Next, the scan driver 3 raises the voltage of the scan electrode 12 to Vm, and the sustain driver 4 sets the voltage of the sustain electrode 13 to 0V. As a result, a third sustain discharge occurs between the scan electrode 12 and the sustain electrode 13. As a result, negative wall charges are accumulated on the scan electrode 12 and positive wall charges are accumulated on the sustain electrode 13. Thus, the second subfield SF2 is completed.

By the way, in the ADS system, when the brightness of the PDP discharge cell is desired to be the lowest, the address discharge and the sustain discharge are performed only in the subfield having the shortest sustain period (the least number of sustain discharges), and the brightness of the PDP discharge cell. When it is desired to make the highest, address discharge and sustain discharge are performed in all subfields. That is, in the example of FIG. 12, the luminance of the discharge cell can be minimized by performing the address discharge and the sustain discharge only in the first subfield SF1.
JP 2002-14652 A

  However, in the conventional driving method as described above, even when the luminance of the discharge cell is the lowest, the discharge cell emits light twice, that is, light emission by address discharge and light emission by sustain discharge. For this reason, it has been difficult to display luminance closer to black.

  An object of the present invention is to provide a display device capable of displaying more luminance and a driving method thereof.

  A display device according to a first invention includes a plurality of first electrodes arranged in a first direction, and a plurality of second electrodes arranged along a second direction intersecting with the first direction. A plurality of third electrodes arranged along the second direction, a plurality of first cells, a plurality of discharge cells provided at intersections of the plurality of second electrodes and the plurality of third electrodes, Subfield dividing means for temporally dividing each field into a plurality of subfields each including an address period and a sustain period; and one or more selected from a plurality of first electrodes in the address period of each subfield A first driving circuit that applies a first driving waveform to the first electrode for address discharge; and a second driving waveform that is applied to each second electrode in the address period of each subfield, and Each in the subsequent maintenance period A second drive circuit for applying one or a plurality of third drive waveforms for sustain discharge to the two electrodes, and a third drive for sustain discharge to each third electrode in the sustain period of each subfield A third drive circuit that applies one or a plurality of fourth drive waveforms having a phase different from the waveform, and the voltage change rate of the third drive waveform of at least one subfield is that of the other subfield. It is smaller than the voltage change rate of each third drive waveform.

  In the display device according to the present invention, the plurality of first electrodes are arranged in the first direction, the plurality of second electrodes are arranged along the second direction intersecting the first direction, The third electrodes are arranged along the second direction, and a plurality of discharge cells are provided at intersections of the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes.

  Each field is temporally divided into a plurality of subfields each including an address period and a sustain period by the subfield dividing means. The first drive waveform is applied to the first electrode selected in the address period of each subfield by the first drive circuit, and the second drive waveform is applied to the second electrode by the second drive circuit. Address discharge occurs.

  In the sustain period, a third drive waveform is applied to the second electrode by the second drive circuit, and a fourth drive waveform having a phase different from that of the third drive waveform by the third drive circuit is applied to the third electrode. Sustain discharge occurs when is applied.

  In this case, since the voltage change rate of the third drive waveform of one of the at least one subfield is smaller than the voltage change rate of the third drive waveform of the other subfield, The sustain discharge due to the drive waveform is weaker than the sustain discharge due to the third drive waveform in the other subfield. Thereby, the luminance of light emission due to the sustain discharge of one subfield is lowered. Therefore, the luminance of light emission in the subfield can be reduced.

  Thus, according to the present invention, it is possible to reduce the luminance of light emission in the subfield by reducing the voltage change rate of the third drive waveform. As a result, more luminance can be displayed.

  The other subfield subsequent to the at least one subfield further includes an initialization period before the address period, and the second driving circuit adjusts the charges of the plurality of discharge cells to each second electrode in the initialization period. The third drive waveform of at least one subfield and the initialization waveform of the other subfield are integrated as a sustain initialization waveform, and the sustain initialization waveform is the first voltage. To the third voltage via the second voltage, then the third voltage drops from the third voltage to the fourth voltage lower than the first voltage, and the third drive waveforms in the other subfields are After the voltage rises from the first voltage to the second voltage, the voltage drops from the second voltage to the first voltage, and the voltage change rate from the first voltage to the second voltage of the sustain initialization waveform is Each third driving wave of the subfield It may be smaller than the first rate of voltage change from the voltage to a second voltage.

  In this case, a weak sustain discharge in one subfield and a discharge cell initialization operation in a subfield subsequent to the subfield can be continuously performed by the sustain initialization waveform. Thereby, the maintenance period and the initialization period can be shortened.

  The other subfield subsequent to the at least one subfield further includes an initialization period before the address period, and the second driving circuit adjusts the charges of the plurality of discharge cells to each second electrode in the initialization period. The third drive waveform of at least one subfield is temporally separated from the third drive waveform of at least one subfield, and the third drive waveform of at least one subfield is After rising from the first voltage to the fifth voltage, the voltage falls from the fifth voltage to the first voltage, and the initialization waveform is the third voltage from the first voltage via the second voltage. Then, the third voltage decreases from the third voltage to the fourth voltage lower than the first voltage, and each third drive waveform in the other subfield increases from the first voltage to the second voltage. After, from the second voltage to the first voltage The voltage change rate from the first voltage to the second voltage of the third drive waveform of the at least one subfield decreases from the first voltage of each third drive waveform of the other subfield to the second voltage. It may be smaller than the voltage change rate up to a voltage of 2.

  In this case, a weak sustain discharge is generated as the third drive waveform rises from the first voltage to the fifth voltage. Thereafter, the wall charges of all the discharge cells are adjusted by applying the initialization waveform.

  The second drive circuit includes a plurality of switching elements and integration circuits that are selectively turned on and off, and the voltage of each second electrode is maintained from the sustain period of at least one subfield to the initialization period of the other subfield. Is increased from the first voltage to the third voltage via the second voltage, and then decreased from the third voltage to the fourth voltage lower than the first voltage to maintain the other subfields. In the period, the voltage of each second electrode may be increased from the first voltage to the second voltage and then decreased from the second voltage to the first voltage.

  In this case, the weak sustain discharge in one subfield and the initializing operation of the discharge cell in the subfield following that subfield can be performed continuously. Thereby, the maintenance period and the initialization period can be shortened.

  In addition, a sustain waveform that generates a weak sustain discharge can be easily created with a simple circuit configuration by a plurality of switching elements and an integration circuit.

  The second drive circuit includes a plurality of switching elements and integration circuits that are selectively turned on and off, and the voltage of each second electrode is changed from the first voltage to the fifth voltage in the sustain period of at least one subfield. After the voltage is increased to the first voltage, the voltage is decreased from the fifth voltage to the first voltage, and the voltage of each second electrode is changed from the first voltage to the third voltage via the second voltage in the initialization period. And then the third voltage is lowered to a fourth voltage lower than the first voltage, and the voltage of each second electrode is changed from the first voltage to the second voltage in the sustain period of the other subfield. Then, the voltage may be lowered from the second voltage to the first voltage.

  In this case, a sustain waveform for generating a weak sustain discharge can be easily created with a simple circuit configuration by a plurality of switching elements and an integration circuit.

  According to a second aspect of the present invention, there is provided a display device driving method comprising: a plurality of first electrodes arranged in a first direction; and a plurality of second electrodes arranged in a second direction intersecting the first direction. A plurality of third electrodes arranged in the second direction, a plurality of first electrodes, a plurality of second electrodes, and a plurality of third electrodes provided at intersections of the plurality of third electrodes. A method of driving a display device including a discharge cell, the step of temporally dividing each field into a plurality of subfields each including an address period and a sustain period, and a plurality of first fields in the address period of each subfield. Applying a first drive waveform for address discharge to one or a plurality of first electrodes selected from among the electrodes, and a second drive waveform for each second electrode in the address period of each subfield Apply the address period Applying one or more third drive waveforms for sustain discharge to each second electrode in the subsequent sustain period; and third for applying sustain discharge to each third electrode in the sustain period of each subfield. Applying one or a plurality of fourth drive waveforms having a phase different from that of the first drive waveform, wherein a voltage change rate of the third drive waveform of one of the at least one subfield has a voltage change rate of each of the other subfields. 3 is smaller than the voltage change rate of the drive waveform.

  In the display device driving method according to the present invention, each field is temporally divided into a plurality of subfields each including an address period and a sustain period. An address discharge occurs when the first drive waveform is applied to the first electrode selected in the address period of each subfield and the second drive waveform is applied to the second electrode.

  In the sustain period, a third drive waveform is applied to the second electrode and a fourth drive waveform having a phase different from that of the third drive waveform is applied to the third electrode, so that a sustain discharge occurs.

  In this case, since the voltage change rate of the third drive waveform of one of the at least one subfield is smaller than the voltage change rate of the third drive waveform of the other subfield, The sustain discharge due to the drive waveform is weaker than the sustain discharge due to the third drive waveform in the other subfield. Thereby, the luminance of light emission due to the sustain discharge of one subfield is lowered. Therefore, the luminance of light emission in the subfield can be reduced.

  Thus, according to the present invention, it is possible to reduce the luminance of light emission in the subfield by reducing the voltage change rate of the third drive waveform. As a result, more luminance can be displayed.

  According to the present invention, the luminance of subfield emission can be reduced by reducing the voltage change rate of the third drive waveform. As a result, more luminance can be displayed.

  Hereinafter, a plasma display device will be described as an example of a display device according to the present invention.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the plasma display device according to the first embodiment of the present invention.

  A plasma display device of FIG. 1 includes a PDP (plasma display panel) 1, a data driver 2, a scan driver 3, a sustain driver 4, an A / D converter (analog / digital converter) 5, and a video signal / subfield correlator 6. And a subfield processor 7.

  The video signal VD is input to the A / D converter 5. The A / D converter 5 converts the analog video signal VD into digital image data and outputs the digital image data to the video signal-subfield correlator 6. Since the video signal-subfield associating unit 6 displays one field divided into a plurality of subfields, the video signal-subfield associating unit 6 creates image data SP of each subfield from the image data of one field and outputs it to the subfield processor 7. To do.

  The subfield processor 7 creates a data driver drive control signal DS, a scan driver drive control signal CS, and a sustain driver drive control signal US from the image data SP for each subfield, and the data driver 2, the scan driver 3, and the sustain driver, respectively. Output to 4.

  The PDP 1 includes a plurality of address electrodes (data electrodes) 11, a plurality of scan electrodes (scan electrodes) 12, and a plurality of sustain electrodes (sustain electrodes) 13. The plurality of address electrodes 11 are arranged in the vertical direction of the screen, and the plurality of scan electrodes 12 and the plurality of sustain electrodes 13 are arranged in the horizontal direction of the screen. The plurality of sustain electrodes 13 are connected in common. A discharge cell 14 is formed at each intersection of the address electrode 11, the scan electrode 12, and the sustain electrode 13, and each discharge cell 14 constitutes a pixel on the screen.

  The data driver 2 is connected to a plurality of address electrodes 11 of the PDP 1. The scan driver 3 includes a drive circuit provided for each scan electrode 12 inside, and each drive circuit is connected to the corresponding scan electrode 12 of the PDP 1. The sustain driver 4 is connected to the plurality of sustain electrodes 13 of the PDP 1.

  In accordance with the data driver drive control signal DS, the data driver 2 applies a write pulse to the corresponding address electrode 11 of the PDP 1 according to the image data SP during the write period.

  The scan driver 3 sequentially applies the write pulse to the plurality of scan electrodes 12 of the PDP 1 while shifting the shift pulse in the vertical scanning direction in accordance with the scan driver drive control signal CS. As a result, address discharge is performed in the corresponding discharge cell 14.

  Further, the scan driver 3 applies a sustain waveform for performing sustain discharge to the plurality of scan electrodes 12 of the PDP 1 in the sustain period in accordance with the scan driver drive control signal CS. On the other hand, the sustain driver 4 applies a sustain waveform to the plurality of sustain electrodes 13 of the PDP 1 in the sustain period in accordance with the sustain driver drive control signal US. Thereby, the sustain discharge is performed in the corresponding discharge cell 14.

  Next, a method for driving the plasma display device according to the present embodiment will be described.

  FIG. 2 is a timing chart showing an example of a drive voltage applied to each electrode of the plasma display device according to the present embodiment.

  The timing chart of FIG. 2 shows the drive voltage of one address electrode 11 arranged in the vertical direction of the PDP 1, the drive voltage of one scan electrode 12 intersecting with the address electrode 11, and the drive of one sustain electrode 13. The voltage is shown.

  Each field is divided into a plurality of subfields. For example, one field is divided into first to eighth subfields. In the example of FIG. 2, the first to third subfields SF1, SF2, and SF3 of one field are shown.

  The first subfield SF1 includes a selective initialization period for generating a weak discharge in the discharge cells 14 that have been sustain-discharged in the last subfield of the previous field to uniformly adjust wall charges, the address electrodes 11 and An address period in which an address pulse is applied to the scan electrode 12 to perform an address discharge and a sustain period in which a sustain waveform is applied to the scan electrode 12 to perform a sustain discharge are configured.

  The second subfield SF2 includes an all-cell initialization period for generating a weak discharge in all the discharge cells 14 to uniformly adjust wall charges, and an address period for performing address discharge by applying a write pulse. And a sustain period in which sustain discharge is performed by applying a sustain waveform.

  The third subfield SF3 includes a selective initialization period, an address period, and a sustain period.

  First, as shown in FIG. 2, in the selective initialization period of the first subfield SF1, the selective initialization waveform Setup1 having the highest voltage Vm having the ramp waveform La1 is applied to the scan electrode 12 by the scan driver 3. . Further, the address electrode 11 is held at 0 V by the data driver 2, and the voltage of the sustain electrode 13 is held at Ve by the sustain driver 4.

  When the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La1, the discharge cell 14 which has been sustain-discharged in the sustain period of the last subfield of the previous field has a gap between the scan electrode 12 and the address electrode 11. In addition, a weak discharge is generated between the scan electrode 12 and the sustain electrode 13. As a result, a predetermined amount of positive wall charge is accumulated in the address electrode 11, a predetermined amount of negative wall charge is accumulated in the scan electrode 12, and a predetermined amount of positive wall charge is accumulated in the sustain electrode 13. As a result, the wall charges of all the discharge cells 14 are adjusted almost uniformly.

  Next, in the address period of the first subfield SF1, the data driver 2 applies a positive write pulse Pw to the address electrode 11 corresponding to the discharge cell 14 to be lit. Further, the scan driver 3 applies a negative write pulse Ps to the scan electrode 12 in synchronization with the write pulse Pw.

  In this case, the effective voltage between the address electrode 11 and the scan electrode 12 corresponding to the discharge cell 14 to be lit is the potential difference between the write pulse Pw and the write pulse Ps at the end of the selective initialization period. 12 and the wall voltage due to wall charges accumulated in each of the address electrodes 11 are added.

  Accordingly, since the effective voltage between the address electrode 11 and the scan electrode 12 exceeds the discharge start voltage, an address discharge is generated between the address electrode 11 and the scan electrode 12, and the scan electrode 12 and the sustain electrode 13 Discharge occurs between them. As a result, positive wall charges are accumulated in the scan electrode 12, and negative wall charges are accumulated in the address electrode 11 and the sustain electrode 13. By this address discharge, the discharge cell 14 emits light once.

  On the other hand, when the write pulse Pw is not applied to the address electrode 11 in the address period, the effective voltage between the address electrode 11 and the scan electrode 12 does not exceed the discharge start voltage. No address discharge occurs in the discharge cell 14 at the intersection.

  Next, in the sustain period of the first subfield SF1, the scan driver 3 applies a sustain waveform having the ramp waveform La2 to the scan electrode 12, and the voltage of the scan electrode 12 is gradually increased. At this time, the sustain driver 4 keeps the voltage of the sustain electrode 13 at 0V. As a result, a weak sustain discharge (hereinafter referred to as a weak sustain discharge) is generated between the scan electrode 12 and the sustain electrode 13. Although the discharge cell 14 emits light due to the weak sustain discharge, the luminance is lower than the light emission by the address discharge and the light emission by the sustain discharge in other sub-fields described later.

  Here, the luminance of light emission by the weak sustain discharge varies depending on the rise time of the sustain waveform. That is, by adjusting the voltage change (voltage change rate) per unit time of the sustain waveform in the sustain period, the luminance of light emission by the weak sustain discharge can be adjusted. In the present embodiment, for example, the voltage change rate of the ramp waveform La2 is adjusted so that the ratio between the luminance of light emitted by the weak sustain discharge and the luminance of light emitted by the sustain discharge in the other subfield is 1: 4. .

  Subsequently, in the all-cell initializing period of the second subfield SF2, the scan driver 3 applies the all-cell initializing waveform Setup2 having the highest voltage Vset having the ramp waveforms La3 and La4 to the scan electrode 12.

  In the all-cell initialization period, first, the voltage of the scan electrode 12 is gradually increased to Vset by the ramp waveform La3. Further, the voltage of the sustain electrode 13 is held at 0V. At this time, a weak discharge is generated between the scan electrode 12 and the address electrode 11 and between the scan electrode 12 and the sustain electrode 13 in all the discharge cells 14. As a result, negative wall charges are accumulated in the scan electrode 12 and positive wall charges are accumulated in the address electrode 11 and the sustain electrode 13.

  In the present embodiment, the ramp waveform La2 in the sustain period of the first subfield SF1 and the ramp waveform La3 in the all-cell initialization period of the second subfield SF2 change continuously. As a result, the voltage of the scan electrode 12 is gradually increased linearly from 0V to Vset. As a result, the time from the start of the sustain period to the end of the all-cell initialization period can be shortened. A method of applying the ramp waveforms La2 and La3 will be described later.

  Next, the scan driver 3 decreases the voltage of the scan electrode 12 to Vm, and the sustain driver 4 increases the voltage of the sustain driver 13 to Ve.

  Thereafter, the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La4. At this time, the voltage of the sustain electrode 13 is held at Ve. As a result, a weak discharge is generated between the scan electrode 12 and the address electrode 11 and between the scan electrode 12 and the sustain electrode 13 in all the discharge cells 14. As a result, the negative wall charges of the scan electrode 12 and the positive wall charges of the address electrode 11 and the sustain electrode 13 are reduced.

  In the discharge cell 14 after the all-cell initialization period, a predetermined amount of positive wall charges is accumulated in the address electrode 11, a predetermined amount of negative wall charges is accumulated in the scan electrode 12, and a predetermined amount of energy is accumulated in the sustain electrode 13. Positive wall charges are accumulated. As described above, the amount of wall charges of all the discharge cells 14 is adjusted uniformly.

  Next, in the address period of the second subfield SF2, the data driver 2 applies a positive write pulse Pw to the address electrode 11 corresponding to the discharge cell 14 to be lit. Further, the scan driver 3 applies a negative write pulse Ps to the scan electrode 12 in synchronization with the write pulse Pw.

  In this case, the effective voltage between the address electrode 11 and the scan electrode 12 corresponding to the discharge cell 14 to be lit is the potential difference between the write pulse Pw and the write pulse Ps, at the end of the all-cell initialization period. 12 and the wall voltage due to wall charges accumulated in each of the address electrodes 11 are added.

  Accordingly, since the effective voltage between the address electrode 11 and the scan electrode 12 exceeds the discharge start voltage, an address discharge is generated between the address electrode 11 and the scan electrode 12, and the scan electrode 12 and the sustain electrode 13 Discharge occurs between them. As a result, positive wall charges are accumulated in the scan electrode 12 and negative wall charges are accumulated in the address electrode 11. Further, negative wall charges are accumulated in the sustain electrode 13. By this address discharge, the discharge cell 14 emits light once.

  On the other hand, when the write pulse Pw is not applied to the address electrode 11 in the address period, the address discharge does not occur as in the first subfield SF1.

  Next, in the sustain period of the second subfield SF2, a sustain waveform is applied to the scan electrode 12 by the scan driver 3, and the voltage of the scan electrode 12 is increased to Vm. At this time, the sustain driver 4 sets the voltage of the sustain electrode 13 to 0V.

  In this case, the effective voltage between the scan electrode 12 and the sustain electrode 13 corresponding to the discharge cell 14 to be lit is the potential difference Vm between the scan electrode 12 and the sustain electrode 13, and the scan electrode 12 and the sustain electrode in the address period. This is a value obtained by adding the wall voltage due to the wall charges accumulated in each of the electrodes 13.

  Accordingly, since the effective voltage between the scan electrode 12 and the sustain electrode 13 exceeds the discharge start voltage, a sustain discharge is generated between the scan electrode 12 and the sustain electrode 13. By this sustain discharge, the discharge cell 14 emits light once.

  On the other hand, no sustain discharge is generated in the discharge cells 14 in which the address discharge is not caused because the write pulse Pw is not applied.

  Thus, the second subfield SF2 is completed.

  In the third subfield SF3, first, the selective initialization waveform Setup3 having the highest voltage Vm having the ramp waveform La5 is applied to the scan electrode 12 by the scan driver 3 in the selective initialization period. Further, the address electrode 11 is held at 0 V by the data driver 2, and the sustain electrode 13 is held at Ve by the sustain driver 4.

  When the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La5, the discharge cell 14 sustained and discharged in the sustain period of the second subfield SF2 and the scan electrode 12 and the address electrode 11 are scanned. A weak discharge is generated between the electrode 12 and the sustain electrode 13. As a result, a predetermined amount of positive wall charge is accumulated in the address electrode 11, a predetermined amount of negative wall charge is accumulated in the scan electrode 12, and a predetermined amount of positive wall charge is accumulated in the sustain electrode 13. As a result, the wall charges of all the discharge cells 14 are adjusted almost uniformly.

  Next, in the address period, the data driver 2 applies a positive write pulse Pw to the address electrode 11 corresponding to the discharge cell 14 to be lit. Further, the scan driver 3 applies a negative write pulse Ps to the scan electrode 12 in synchronization with the write pulse Pw.

  In this case, the effective voltage between the address electrode 11 and the scan electrode 12 corresponding to the discharge cell 14 to be lit is the potential difference between the write pulse Pw and the write pulse Ps at the end of the selective initialization period. 12 and the wall voltage due to wall charges accumulated in each of the address electrodes 11 are added.

  Accordingly, since the effective voltage between the address electrode 11 and the scan electrode 12 exceeds the discharge start voltage, an address discharge is generated between the address electrode 11 and the scan electrode 12, and the scan electrode 12 and the sustain electrode 13 Discharge occurs between them. As a result, positive wall charges are accumulated in the scan electrode 12, and negative wall charges are accumulated in the address electrode 11 and the sustain electrode 13. By this address discharge, the discharge cell 14 emits light once.

  Next, in the sustain period of the third subfield SF3, a sustain waveform is applied to the scan electrode 12 by the scan driver 3, and the voltage of the scan electrode 12 is raised to Vm. At this time, the sustain driver 4 sets the voltage of the sustain electrode 13 to 0V.

  In this case, the effective voltage between the scan electrode 12 and the sustain electrode 13 corresponding to the discharge cell 14 to be lit is the potential difference Vm between the scan electrode 12 and the sustain electrode 13, and the scan electrode 12 and the sustain electrode in the address period. This is a value obtained by adding the wall voltage due to the wall charges accumulated in each of the electrodes 13.

  Accordingly, since the effective voltage between the scan electrode 12 and the sustain electrode 13 exceeds the discharge start voltage, the first sustain discharge is generated between the scan electrode 12 and the sustain electrode 13, and the discharge cell 14 is discharged once. Emits light.

  Subsequently, the scan driver 3 sets the voltage of the scan electrode 12 to 0 V, and the sustain driver 4 increases the voltage of the sustain electrode 13 to Vm. Accordingly, since the effective voltage between the scan electrode 12 and the sustain electrode 13 exceeds the discharge start voltage, a second sustain discharge is generated between the scan electrode 12 and the sustain electrode 13, and the discharge cell 14 is discharged once. Emits light.

  Subsequently, the scan driver 3 increases the voltage of the scan electrode 12 to Vm, and the sustain driver 4 sets the voltage of the sustain electrode 13 to 0V. Accordingly, since the effective voltage between the scan electrode 12 and the sustain electrode 13 exceeds the discharge start voltage, a third sustain discharge is generated between the scan electrode 12 and the sustain electrode 13, and the discharge cell 14 is discharged once. Emits light. Thus, the third subfield SF3 is completed.

  Each of the fourth to eighth subfields has a selective initialization period, an address period, and a sustain period like the third subfield SF3. However, the number of sustain discharges in the sustain period varies depending on each subfield. In each of the third to eighth subfields, an all-cell initialization period in which the all-cell initialization waveform Setpu2 is applied may be provided instead of the selective initialization period.

  As described above, in the present embodiment, the weak sustain discharge is generated by applying the ramp waveform La2 to the scan electrode 12 in the sustain period of the first subfield SF1. In this case, light emission of the discharge cell 14 due to the weak sustain discharge in the sustain period of the first subfield SF1 (hereinafter referred to as weak light emission) occurs after the address period of the first subfield SF1 and the second subfield SF2 and thereafter. The luminance is lower than light emission in the address period and sustain period in each subfield (hereinafter referred to as strong light emission).

  Here, when the number of strong light emission in the first to third subfields is arranged, the number of strong light emission in the first subfield SF1 is 1, and the number of strong light emission in the second subfield SF2 is 2. The number of times of strong light emission in the third subfield SF3 is four times. In FIG. 2, the timing at which the discharge cell 14 emits strong light is indicated by a dotted circle.

  In the ADS system, gradation display can be performed by selecting and combining subfields to be lit.

  In the present embodiment, the number of strong light emission is adjusted by selecting and combining the subfields to be lit, and gradation display is performed.

  Table 1 shows the relationship between the subfields to be lit to display each gradation level and the number of times of strong light emission at each gradation level. In Table 1, subfields to be lit are indicated by ◯, and subfields that are not lit are indicated by x.

  As shown in Table 1, in the present embodiment, by selecting and combining the subfields to be lit from the first to third subfields SF1, SF2, and SF3, the number of times of strong light emission of the discharge cell 14 is set to 1 to 1. It can be changed by 1 to 7. For example, when the luminance of the discharge cell 14 is desired to be lowest, that is, when the gradation level 1 is desired to be displayed, only the first subfield SF1 is turned on and strong light emission is performed once. Further, when displaying the gradation level 5, the first subfield SF1 and the third subfield SF5 are turned on and strong light emission is performed five times.

  On the other hand, in the conventional driving method described in FIG. 13, in the first subfield SF1, the discharge cell emits strong light once each in the address period and the sustain period. That is, the number of times of strong light emission in the first subfield SF1 is 2.

  In the second subfield SF2, the discharge cell emits strong light once in the address period and strong light three times in the sustain period. That is, the number of times of strong light emission in the second subfield SF2 is four.

  Table 2 shows the relationship between the subfields to be lit to display the gradation in the conventional driving method and the number of times of strong light emission in each gradation. In Table 2, subfields to be lit are indicated by ◯, and subfields not to be lit are indicated by x.

  As shown in Table 2, in the conventional driving method, when the gradations 1 to 3 are displayed, the number of times of strong light emission of the discharge cells changes by 2, 4, and 6. Thus, in the conventional driving method, each gradation level is expressed by the number of times of strong light emission that is a multiple of two. That is, the lowest gradation level is expressed by two strong light emissions.

  In contrast, in the method for driving the plasma display device according to the present embodiment, each gradation level can be expressed by the number of times of strong light emission that is a multiple of 1. Thereby, it becomes possible to display more luminance.

  Further, the ramp waveform La2 is applied so that the ratio of the weak light emission luminance to the strong light emission luminance in the discharge cell 14 is 1: 4. In this case, since the luminance of weak light emission becomes small, the luminance of light emission in the first subfield SF1 is greatly reduced. That is, the luminance at the lowest gradation level can be greatly reduced. Thereby, it is possible to display a luminance closer to black.

  In the present embodiment, the luminance of the lowest gradation level, that is, the luminance due to the light emission of the first subfield SF1 is a value obtained by adding the light emission luminance of weak light emission to the light emission luminance of strong light emission. For example, when the weighting of the luminance of strong light emission is 0.4 and the weighting of the luminance of weak light emission is 0.1, the luminance of gradation level 1 is 0.5 and the luminance of gradation level 2 is 0.9. Thus, the luminance at gradation level 3 is 1.3.

  Here, when the voltage change rate of the ramp waveform La2 is adjusted and the weight of the weak emission luminance is set to 0.2, the luminance of the gradation levels 1 to 3 becomes 0.6, 1.0, and 1.4, respectively. . Thus, in the present embodiment, the brightness of each gradation level can be adjusted by adjusting the voltage change rate of the ramp waveform La2 and adjusting the brightness of weak light emission. Thereby, it is possible to display more luminance.

  Next, a method for applying the ramp waveforms La2 and La3 in the sustain period of the first subfield SF1 and the second subfield SF2 will be described in detail.

  First, the scan driver 3 in FIG. 1 will be described.

  FIG. 3 is a circuit diagram showing a configuration of the scan driver 3 of FIG. In the following description, an example of a positive pulse that discharges when the drive voltage rises is shown, but a negative pulse that discharges when the drive voltage falls may be used.

  The scan driver 3 shown in FIG. 3 includes FETs (field effect transistors, hereinafter abbreviated as transistors) Q11 to Q22, capacitors C11 to C15, a coil L1, power supply terminals V11 to V14, and diodes D11 to D14.

  The transistor Q13 of the scan driver 3 is connected between the power supply terminal V11 and the node N13, and a control signal S13 is input to the gate. A voltage Vm is applied to the power supply terminal V11. The transistor Q14 is connected between the node N13 and the ground terminal, and a control signal S14 is input to a gate.

  Capacitor C11 is connected between node N11 and the ground terminal. Transistor Q11 and diode D11 are connected in series between nodes N11 and N12. Diode D12 and transistor Q12 are connected in series between nodes N12 and N11. A control signal S11 is input to the gate of the transistor Q11, and a control signal S12 is input to the gate of the transistor Q12. Coil L11 is connected between nodes N12 and N13.

  Capacitor C12 is connected between nodes N14 and N13. The diode D13 is connected between the power supply terminal V12 and the node N14. A voltage Vr is applied to the power supply terminal V12.

  The transistor Q15 is connected between the node N14 and the node N15, and a control signal S15 is input to a gate. Capacitor C13 is connected between node N14 and the gate of transistor Q15. The transistor Q16 is connected between the node N15 and the node N13, and a control signal S16 is input to a gate.

  The transistor Q17 is connected between the node N15 and the node N16, and a control signal S17 is input to a gate. The transistor Q18 is connected between the node N16 and the power supply terminal V13, and a control signal S18 is input to a gate. A voltage Vad is applied to the power supply terminal V13. Capacitor C14 is connected between node N16 and the gate of transistor Q18.

  Capacitor C15 is connected between nodes N16 and N17. Diode D14 is connected between power supply terminal V14 and node N17. A voltage Vs is applied to the power supply terminal V14.

  The transistor Q19 is connected between the node N17 and the node N18, and a control signal S19 is input to a gate. The transistor Q20 is connected between the node N18 and the node N16, and a control signal S20 is input to a gate.

  The transistor Q21 is connected between the node N18 and the scan electrode 12, and a control signal S21 is input to a gate. The transistor Q22 is connected between the node N16 and the scan electrode 12, and a control signal S22 is input to a gate.

  Next, control signals S11 to S22 in the sustain period of first subfield SF1 and the all-cell initialization period of second subfield SF2 in FIG. 2 will be described.

  FIG. 4 is a timing chart of control signals S11 to S22 in the sustain period of first subfield SF1 and the all-cell initialization period of second subfield SF2.

  At the start of the sustain period, the control signals S11, S12, S13, S15, S18, S19, and S21 are each at a low level. Thereby, the transistors Q11, Q12, Q13, Q15, Q18, Q19, Q21 are turned off. Further, the control signals S14, S16, S17, S20, and S22 are each at a high level. Thereby, the transistors Q14, Q16, Q17, Q20, and Q22 are turned on. In this case, the voltage of the scan electrode 11 is 0V.

  At the time point t1 of the sustain period, the control signal S15 becomes high level and the transistor Q15 is turned on, and the control signal S16 becomes low level and the transistor Q16 is turned off. At this time, the node N13 is at 0V, and the node N14 is at the voltage Vr. Further, a current gradually flows to the gate of the transistor Q15 due to RC integration by the capacitor C13 and the gate resistance, and a current gradually flows from the power supply terminal V12 to the scan electrode 12. As a result, the voltage of the scan electrode 12 gradually increases.

  Next, at the time point t2 of the sustain period, the control signal S11 goes high and the transistor Q11 turns on, the control signal S14 goes low and the transistor Q14 turns off, and the control signal S15 goes low and the transistor Q15 Is turned off, the control signal S16 goes high, and the transistor Q16 is turned on.

  Next, at the time point t3 of the sustain period, the control signal S11 becomes low level, the transistor Q11 turns off, the control signal S13 becomes high level, the transistor Q13 turns on, the control signal S15 becomes high level, and the transistor Q15 Is turned on, the control signal S16 goes low, and the transistor Q16 is turned off. At this time, the node N13 is loaded with the voltage Vm of the power supply terminal V11, and the node N14 has a voltage (Vm + Vr) through the capacitor C12. Further, a current gradually flows to the gate of the transistor Q15 due to RC integration by the capacitor C13 and the gate resistance, and a current gradually flows from the power supply terminal V12 to the scan electrode 12. Thereby, the voltage of the scan electrode 12 rises from Vm to Vset (Vm + Vr).

  Next, at the time point t4 of the all-cell initialization period, the control signal S15 is at a low level, the transistor Q15 is turned off, the control signal S16 is at a high level, and the transistor Q16 is turned on. In this case, the voltage of the scan electrode 12 falls to the voltage Vm of the power supply terminal V11.

  Next, at the time point t5 of the all-cell initialization period, the control signal S13 becomes low level, the transistor Q13 turns off, the control signal S18 becomes high level, the transistor Q18 turns on, and the control signal S19 becomes low level. The transistor Q19 is turned off. In this case, the voltage of the scan electrode 12 gradually decreases to the voltage Vad of the power supply terminal V13.

  Here, in the present embodiment, a capacitor C13 is connected between the drain and gate of the transistor Q15. In this case, by adjusting the capacitance of the capacitor C13, the RC time constant due to the gate resistance of the capacitor C13 and the transistor Q15 changes, and the voltage change rate of the ramp waveforms La2 and La3 can be changed. In the present embodiment, the ramp waveforms La2 and La3 are changed in voltage at a constant voltage change rate. However, the ramp waveforms La2 and La3 that change in a curve as shown in FIG. May be.

(Second Embodiment)
FIG. 6 is a timing chart showing drive voltages applied to the respective electrodes of the plasma display device according to the second embodiment.

  The timing chart of FIG. 6 differs from the timing chart of FIG. 2 in the following points.

  In the timing chart of FIG. 6, in the sustain period of the first subfield SF1, the voltage of the scan electrode 12 is gradually increased to Vr by the ramp waveform La6. At this time, a weak discharge is generated between the scan electrode 12 and the sustain electrode 13, and the discharge cell 14 emits weak light.

  Next, in the all-cell initializing period of the second subfield SF2, the scan driver 3 applies the all-cell initializing waveform Setup4 having the highest voltage Vset having the ramp waveforms La7 and La8 to the scan electrode 12.

  In the all-cell initialization period, first, the scan driver 3 raises the voltage of the scan electrode 12 to Vm, and the sustain driver 4 holds the voltage of the sustain electrode 13 at 0V.

  Thereafter, the voltage of the scan electrode 12 is gradually increased to Vset by the ramp waveform La7. At this time, the voltage of the sustain electrode 13 is held at 0V. As a result, weak discharge is generated between the scan electrode 12 and the address electrode 11 and between the scan electrode 12 and the sustain electrode 13 in all the discharge cells. As a result, negative wall charges are accumulated in the scan electrode 12 and positive wall charges are accumulated in the address electrode 11 and the sustain electrode 13.

  Next, the scan driver 3 decreases the voltage of the scan electrode 12 to Vm, and the sustain driver 4 increases the voltage of the sustain electrode 13 to Ve.

  Thereafter, the voltage of the scan electrode 12 is gradually lowered to Vad by the ramp waveform La8. At this time, the voltage of the sustain electrode 13 is held at Ve. Thereby, a weak discharge is generated between the scan electrode 12 and the address electrode 11 and between the scan electrode 12 and the sustain electrode 13 in all the discharge cells. As a result, the negative wall charges of the scan electrode 12 and the positive wall charges of the address electrode 11 and the sustain electrode 13 are reduced.

  In the discharge cell after the all-cell initialization period, a predetermined amount of positive wall charge is accumulated in the address electrode 11, a predetermined amount of negative wall charge is accumulated in the scan electrode 12, and a predetermined amount of positive wall charge is accumulated in the sustain electrode 13. Wall charges are accumulated. As described above, the amount of wall charges of all the discharge cells is adjusted uniformly.

  Thus, in the driving method of the plasma display device according to the present embodiment, the discharge cell 14 is caused to emit weak light by applying the ramp waveform La6 to the scan electrode 3 in the sustain period of the first subfield SF1. Yes. As a result, the number of times of strong light emission of the discharge cell 14 in the first subfield SF1 is one.

  In this case, each gradation level can be expressed by the number of times of strong light emission that is a multiple of 1. Thereby, it becomes possible to display more luminance.

  In addition, the luminance of light emission in the first subfield SF1 can be significantly reduced. That is, the luminance at the lowest gradation level can be greatly reduced. Thereby, it is possible to display a luminance closer to black.

  Further, the brightness of each gradation level can be adjusted by adjusting the voltage change rate of the ramp waveform La6 and adjusting the brightness of weak light emission. Thereby, it is possible to display more luminance.

  Next, a method of applying a drive voltage applied to scan electrode 12 in the sustain period of first subfield SF1 and the all-cell initialization period of second subfield SF2 will be described.

  FIG. 7 is a timing chart of control signals S11 to S22 in the sustain period of first subfield SF1 and the all-cell initialization period of second subfield SF2.

  At the start of the sustain period, the control signals S11, S12, S13, S15, S18, S19, and S21 are each at a low level. Thereby, the transistors Q11, Q12, Q13, Q15, Q18, Q19, Q21 are turned off. Further, the control signals S14, S16, S17, S20, and S22 are each at a high level. Thereby, the transistors Q14, Q16, Q17, Q20, and Q22 are turned on. In this case, the voltage of the scan electrode 11 is 0V.

  At the time point t1 of the sustain period, the control signal S15 becomes high level and the transistor Q15 is turned on, and the control signal S16 becomes low level and the transistor Q16 is turned off. Thereby, a current flows from the power supply terminal V12 to the scan electrode 12, and the voltage of the scan electrode 12 gradually rises to Vr. At this time, by adjusting the width of the high level of the control signal S15 and the low level of the control signal S16, the voltage of the scan electrode 12 can be freely set from 0 V to the voltage Vr, and the brightness of the weak discharge Can be adjusted.

  Next, at the time point t2 of the sustain period, the control signal S15 becomes low level, the transistor Q15 turns off, the control signal S16 becomes high level, and the transistor Q16 turns on. As a result, the voltage of the scan electrode 12 drops to 0V.

  Next, at time t3 in the all-cell initialization period, the control signal S11 becomes high level, the transistor Q11 is turned on, the control signal S14 becomes low level, and the transistor Q14 is turned off. As a result, a current flows from the capacitor C11 to the scan electrode 12, and the voltage of the scan electrode 12 increases.

  Next, at the time point t4 of the all-cell initialization period, the control signal S11 becomes low level, the transistor Q11 is turned off, the control signal S13 becomes high level, and the transistor Q13 is turned on. Thereby, a current flows from the power supply terminal V11 to the scan electrode 12, and the voltage of the scan electrode 12 rises to Vm.

  Next, at time t5 in the all-cell initialization period, the control signal S15 becomes high level, the transistor Q15 is turned on, the control signal S16 becomes low level, and the transistor Q16 is turned off. In this case, a current flows from the power supply terminal V12 to the scan electrode 12, and a current flows from the power supply terminal V11 to the node N13. Thereby, the voltage of the scan electrode 12 rises to Vset (Vm + Vr).

  Next, at the time point t6 of the all-cell initialization period, the control signal S15 becomes low level, the transistor Q15 is turned off, the control signal S16 becomes high level, and the transistor Q16 is turned on. In this case, the voltage of the scan electrode 12 drops to the voltage Vm of the power supply terminal V11.

  Next, at the time point t7 of the all-cell initialization period, the control signal S13 becomes low level, the transistor Q13 turns off, the control signal S18 becomes high level, the transistor Q18 turns on, and the control signal S19 becomes low level. The transistor Q19 is turned off. In this case, the voltage of the scan electrode 12 gradually decreases to the voltage Vad of the power supply terminal V13.

  In the present embodiment, similarly to the first embodiment, the voltage change rate of the ramp waveform La6 can be changed by adjusting the capacitance of the capacitor C13. In the present embodiment, the ramp waveform La6 changes in voltage at a constant voltage change rate, but a ramp waveform La6 (not shown) that changes in a curved line may be applied to the scan electrode 12.

(Correspondence between each component of claim and each part of embodiment)
In the above embodiment, the address electrode 11 corresponds to the first electrode, the scan electrode 12 corresponds to the second electrode, the sustain electrode 13 corresponds to the third electrode, and the subfield processor 7 is the sub-field processor 7. The write pulse Pw corresponds to the first drive waveform, the data driver 2 corresponds to the first drive circuit, the write pulse Ps corresponds to the second drive waveform, and the sustain waveform corresponds to the field dividing means. 3, the scan driver 3 corresponds to the second drive circuit, 0V corresponds to the first voltage, the voltage Vm corresponds to the second voltage, and the voltage Vset corresponds to the third voltage. The voltage Vad corresponds to the fourth voltage, the voltage Vr corresponds to the fifth voltage, the transistors Q11 to Q22 correspond to the switching elements, and the capacitor C13 and the transistor Q15 correspond to the integrating circuit. To.

(Other embodiments)
As the switching element, various other transistors such as a bipolar transistor may be used instead of the field effect transistor. In addition, the first to sixth voltages are not limited to those described in the above embodiment, and other arbitrarily set voltages may be used.

  The present invention can be used to display various videos.

The block diagram which shows the structure of the plasma display apparatus which concerns on 1st Embodiment. Timing chart showing an example of drive voltage applied to each electrode of the plasma display device Circuit diagram showing the configuration of the scan driver of FIG. Timing chart of control signals S11 to S22 in the sustain period of first subfield SF1 and the all-cell initialization period of second subfield SF2 The figure which shows an example of ramp waveform La2, La3 Timing chart showing drive voltage applied to each electrode of plasma display device according to second embodiment Timing chart of control signals S11-S22 in the sustain period of the first subfield SF1, the second selective initialization period, and the all-cell initialization period of the second subfield SF2. The figure for demonstrating the drive method of the discharge cell in AC type PDP Schematic diagram mainly showing the configuration of a PDP of a conventional plasma display device Schematic sectional view of three-electrode surface discharge cell in AC type PDP Diagram for explaining the ADS system Timing chart showing an example of drive voltage applied to each electrode of a conventional AC type PDP

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma display panel 2 Data driver 3 Scan driver 4 Sustain driver 5 A / D converter 6 Video signal-subfield matching device 7 Subfield processor 11 Address electrode 12 Scan electrode 13 Sustain electrode 14 Discharge cell C11-C15 Capacitor CS scan Driver drive control signal D11 to D14 Diode DS Data driver drive control signal L1 Coil La1 to La8 Ramp waveform Pw, Ps Write pulse Q11 to Q22 Transistor SP Image data SF1 to SF8 First to eighth subfields US Sustain driver drive control signal V11 to V14 Power supply terminal

Claims (6)

A plurality of first electrodes arranged in a first direction;
A plurality of second electrodes arranged along a second direction intersecting the first direction;
A plurality of third electrodes arranged along the second direction;
A plurality of discharge cells provided at intersections of the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes;
Subfield dividing means for temporally dividing each field into a plurality of subfields each including an address period and a sustain period;
A first drive circuit for applying a first drive waveform for address discharge to one or a plurality of first electrodes selected from the plurality of first electrodes in an address period of each subfield;
A second drive waveform is applied to each second electrode in the address period of each subfield, and one or more third drive waveforms are applied to each second electrode for sustain discharge in the sustain period following the address period. A second drive circuit for applying
A third drive circuit that applies one or a plurality of fourth drive waveforms having a phase different from that of the third drive waveform to each third electrode for the sustain discharge in the sustain period of each subfield. ,
A display device, wherein a voltage change rate of a third drive waveform of one of at least one subfield is smaller than a voltage change rate of each third drive waveform of another subfield. The other subfield following the at least one subfield further includes an initialization period before the address period;
The second drive circuit applies an initialization waveform for adjusting charges of the plurality of discharge cells to each second electrode in the initialization period,
The third drive waveform of the at least one subfield and the initialization waveform of the other subfield are integrated as a sustain initialization waveform,
The sustain initialization waveform rises from the first voltage to the third voltage via the second voltage, and then falls from the third voltage to a fourth voltage lower than the first voltage. ,
Each third driving waveform of the other subfield rises from the first voltage to the second voltage, and then falls from the second voltage to the first voltage,
The voltage change rate from the first voltage to the second voltage of the sustain initialization waveform is based on the voltage change rate from the first voltage to the second voltage of each third drive waveform of the other subfield. The display device according to claim 1, wherein the display device is also small. The other subfield following the at least one subfield further includes an initialization period before the address period;
The second drive circuit applies an initialization waveform for adjusting charges of the plurality of discharge cells to each second electrode in the initialization period,
The third drive waveform of the at least one subfield and the initialization waveform of the other subfield are temporally separated,
The third drive waveform of the at least one subfield rises from the first voltage to the fifth voltage, then falls from the fifth voltage to the first voltage, and the initialization waveform has the first waveform From the first voltage to the third voltage via the second voltage, and then from the third voltage to the fourth voltage lower than the first voltage,
Each third driving waveform of the other subfield rises from the first voltage to the second voltage, and then falls from the second voltage to the first voltage,
The voltage change rate from the first voltage to the second voltage of the third drive waveform of the at least one subfield is the second voltage from the first voltage of each third drive waveform of the other subfield. The display device according to claim 1, wherein the display device is smaller than a voltage change rate up to a voltage. The second driving circuit includes a plurality of switching elements and integration circuits that are selectively turned on and off, and each of the second driving circuits from the sustain period of the at least one subfield to the initialization period of the other subfield. The voltage of the second electrode is increased from the first voltage to the third voltage via the second voltage, and then decreased from the third voltage to the fourth voltage lower than the first voltage. The voltage of each second electrode is increased from the first voltage to the second voltage and then decreased from the second voltage to the first voltage in the sustain period of the other subfield. The display device according to claim 2, characterized in that: The second drive circuit includes a plurality of switching elements and integration circuits that are selectively turned on and off, and the voltage of each second electrode is changed from the first voltage in the sustain period of the at least one subfield. After raising the voltage to the fifth voltage, the voltage is lowered from the fifth voltage to the first voltage, and the voltage of each second electrode is passed from the first voltage to the second voltage in the initialization period. The third voltage is raised to a third voltage, and then lowered from the third voltage to a fourth voltage lower than the first voltage. In the sustain period of the other subfield, each second electrode 4. The display device according to claim 3, wherein the voltage is increased from the first voltage to the second voltage and then decreased from the second voltage to the first voltage. A plurality of first electrodes arranged in a first direction, a plurality of second electrodes arranged along a second direction intersecting the first direction, and along the second direction A display device comprising: a plurality of arranged third electrodes; and a plurality of discharge cells provided at intersections of the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes. Driving method,
Temporally dividing each field into a plurality of subfields each including an address period and a sustain period;
Applying a first driving waveform for address discharge to one or a plurality of first electrodes selected from the plurality of first electrodes in an address period of each subfield;
A second drive waveform is applied to each second electrode in the address period of each subfield, and one or more third drive waveforms are applied to each second electrode for sustain discharge in the sustain period following the address period. Applying, and
Applying one or more fourth drive waveforms having a phase different from that of the third drive waveform for sustain discharge to each third electrode in the sustain period of each subfield,
A display device driving method, wherein a voltage change rate of a third drive waveform of one of at least one subfield is smaller than a voltage change rate of each third drive waveform of another subfield.

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