JP2007163736A - Method for driving plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a stable write discharge without increasing a voltage needed to generate a write discharge even when a panel has a large screen and high luminance. <P>SOLUTION: The method for driving the plasma display panel is characterized in that one field period comprises a plurality of sub-fields each having a write period wherein a write discharge is selectively generated by a discharge cell and a sustain period wherein a sustain discharge is generated by the discharge cell having generated the write discharge at a frequency proportional to a luminance weight and a voltage is applied to the display electrode pair at a time interval, corresponding to the turn-on rate of the discharge cell in the sub-fields, after a voltage for generating a final maintenance discharge is applied to the display electrode pair in the maintenance period so that the potential difference between electrodes of a display electrode pair is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  A typical AC surface discharge type panel as a plasma display panel (hereinafter abbreviated as “panel”) has a large number of discharge cells formed between a front plate and a back plate arranged to face each other. In the front plate, a plurality of display electrode pairs each consisting of a pair of scan electrodes and sustain electrodes are formed in parallel with each other on the front glass substrate, and a dielectric layer and a protective layer are formed so as to cover the display electrode pairs. Yes. The back plate has a plurality of parallel data electrodes on the back glass substrate, a dielectric layer so as to cover them, and a plurality of barrier ribs in parallel with the data electrodes formed on the back glass substrate. A phosphor layer is formed on the side walls of the barrier ribs. Then, the front plate and the back plate are arranged opposite to each other so that the display electrode pair and the data electrode are three-dimensionally crossed and sealed, and a discharge gas containing xenon is sealed in the internal discharge space. Here, a discharge cell is formed at a portion where the display electrode pair and the data electrode face each other. In the panel having such a configuration, ultraviolet light is generated by gas discharge in each discharge cell, and phosphors of RGB colors are excited and emitted by the ultraviolet light to perform color display.

  As a method of driving the panel, a subfield method, that is, a method of performing gradation display by combining subfields to emit light after dividing one field period into a plurality of subfields. Each subfield has an initialization period, an address period, and a sustain period. In the initialization period, an initialization discharge is generated, and wall charges necessary for the subsequent address operation are formed on each electrode. In the address period, address discharge is selectively generated in the discharge cells to be displayed to form wall charges. In the sustain period, a sustain pulse is alternately applied to the display electrode pair composed of the scan electrode and the sustain electrode, and a sustain discharge is generated in the discharge cell in which the address discharge is generated, and the phosphor layer of the corresponding discharge cell is caused to emit light. The image is displayed.

  Even in the subfield method, light emission that is not related to gradation display is achieved by performing initializing discharge using a slowly changing voltage waveform and selectively performing initializing discharge on discharge cells that have undergone sustain discharge. A novel driving method is disclosed in which the contrast ratio is improved as much as possible (see, for example, Patent Document 1).

Patent Document 1 also describes a so-called narrow erase discharge in which the pulse width of the last sustain pulse in the sustain period is made shorter than the pulse width of other sustain pulses, and the potential difference due to wall charges between display electrodes is reduced. ing. By stably generating this narrow erase discharge, a reliable address operation can be performed in the address period of the subsequent subfield, and a plasma display device with a high contrast ratio can be realized.
JP 2000-242224 A

  However, along with the recent increase in screen size and brightness, the narrow erase discharge tends to become unstable, so the address discharge becomes unstable and address discharge occurs in the discharge cells to be displayed. Thus, there have been problems such as deterioration of image display quality or increase in voltage necessary for generating address discharge.

  The present invention has been made in view of these problems, and generates a stable address discharge without increasing the voltage necessary for generating the address discharge even in a large screen / high brightness panel, It is an object to provide a method for driving a panel with good display quality.

  The present invention relates to a method for driving a panel having a plurality of discharge cells each having a display electrode pair composed of a scan electrode and a sustain electrode, wherein one field period is an address period in which an address discharge is selectively generated in the discharge cells. A plurality of subfields having a sustain period in which the number of sustain discharges in proportion to the luminance weight is generated in the discharge cell in which the address discharge is generated, and a voltage for generating the last sustain discharge in the sustain period After being applied to the display electrode pair, a voltage is applied to the display electrode pair to relax the potential difference between the electrodes of the display electrode pair at a time interval that can be switched with hysteresis characteristics based on the lighting rate of the discharge cell in the subfield. It is characterized by doing. By this method, even for a large-screen, high-luminance panel, a stable address discharge is generated without increasing the voltage required to generate the address discharge, and a panel driving method with good image display quality is provided. can do.

  Further, the present invention generates an address period in which a discharge cell having a plurality of discharge cells each having a display electrode pair composed of a scan electrode and a sustain electrode and an address discharge are generated selectively in the discharge cell in one field period. And a first sub-field for applying a voltage for generating a sustain discharge to the display electrode pair. A driving method for a panel that is driven using a second switching element that applies a voltage for relaxing a potential difference between the switching element and the electrode of the display electrode pair to the display electrode pair. When generating the discharge, after turning on the first switching element, the hysteresis characteristic based on the lighting rate of the discharge cell in the subfield At a time interval which is switched with, and wherein turning on the second switching element. With this method, even for a large screen / high brightness panel, a stable address discharge is generated without increasing the voltage necessary to generate the address discharge, and a panel driving method with good image display quality is achieved. Can be provided.

  The time interval is switched based on a comparison between the lighting rate of the discharge cells in the current subfield and a predetermined threshold value, and from the first time interval to a second time interval longer than that. The threshold value for switching may be set to a value larger than the threshold value for switching from the second time interval to the first time interval. By this method, the brightness of the display image can be stabilized and the image display quality can be improved.

  Further, the lighting rate of the discharge cells may be compared between subfields having the same luminance weight in the current field and the immediately preceding field, and the threshold value may be changed based on the result. By this method, the brightness of the display image can be stabilized and the image display quality can be further improved.

  Further, as a result of the comparison, the threshold value when the lighting rate of the discharge cell is increased may be set to a value larger than the threshold value when the lighting rate of the discharge cell is decreased. Good. This method stabilizes the brightness of the displayed image by preventing frequent switching of the time interval even when the lighting rate repeats minute fluctuations near the threshold value. Can be further improved.

  In the panel driving method of the present invention, one subfield is controlled so that the time interval is switched based on the comparison result between the lighting rate of the discharge cells in the current subfield and a predetermined threshold value. It is desirable to include at least one in the period. By this method, the brightness of the display image can be stabilized and the image display quality can be further improved.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a large screen and a high-intensity panel, it is possible to generate a stable address discharge without increasing the voltage necessary for generating the address discharge, and to drive the panel with good image display quality. Can be provided.

  Hereinafter, a panel driving method according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is an exploded perspective view showing a main part of a panel used in the embodiment of the present invention. The panel 10 is configured such that a glass front substrate 21 and a rear substrate 31 are arranged to face each other and a discharge space is formed therebetween. On the front substrate 21, a plurality of scanning electrodes 22 and sustaining electrodes 23 constituting a display electrode pair are formed in parallel with each other. A dielectric layer 24 is formed so as to cover the scan electrodes 22 and the sustain electrodes 23, and a protective layer 25 is formed on the dielectric layer 24. A plurality of data electrodes 32 covered with an insulating layer 33 are provided on the back substrate 31, and a grid-like partition wall 34 is provided on the insulating layer 33. A phosphor layer 35 is provided on the surface of the insulator layer 33 and the side surfaces of the partition walls 34. The front substrate 21 and the rear substrate 31 are arranged to face each other so that the scan electrode 22 and the sustain electrode 23 and the data electrode 32 intersect each other, and in the discharge space formed therebetween, for example, neon And a mixed gas of xenon. Note that the structure of the panel is not limited to the above-described structure, and for example, a structure having a stripe-shaped partition may be used.

  FIG. 2 is an electrode array diagram of the panel used in the embodiment of the present invention. N scan electrodes SC1 to SCn (scan electrode 22 in FIG. 1) and n sustain electrodes SU1 to SUn (sustain electrode 23 in FIG. 1) are arranged in the row direction, and m data electrodes D1 to D1 are arranged in the column direction. Dm (data electrode 32 in FIG. 1) is arranged. A discharge cell is formed at a portion where a pair of scan electrode SCi and sustain electrode SUi (i = 1 to n) and one data electrode Dj (j = 1 to m) intersect, and the discharge cell is in the discharge space. M × n are formed.

  FIG. 3 is a circuit block diagram of a plasma display device using the panel according to the embodiment of the present invention. The plasma display device includes a panel 10, an image signal processing circuit 51, a data electrode drive circuit 52, a scan electrode drive circuit 53, a sustain electrode drive circuit 54, a timing generation circuit 55, a lighting rate calculation circuit 58, and a power supply circuit (not shown). ).

  The image signal processing circuit 51 converts the image signal sig into image data for each subfield. The data electrode driving circuit 52 converts the image data for each subfield into signals corresponding to the data electrodes D1 to Dm, and drives the data electrodes D1 to Dm. The lighting rate calculation circuit 58 is based on the image data for each subfield, and the lighting rate of the discharge cells for each subfield, that is, the ratio of the number of discharge cells to be lit to the total number of discharge cells (hereinafter simply referred to as “lighting rate”). Is calculated. The timing generation circuit 55 generates various timing signals based on the horizontal synchronization signal H, the vertical synchronization signal V, and the lighting rate calculated by the lighting rate calculation circuit 58, and supplies them to each circuit block. Scan electrode drive circuit 53 supplies drive voltage waveforms to scan electrodes SC1 to SCn based on timing signals, and sustain electrode drive circuit 54 supplies drive voltage waveforms to sustain electrodes SU1 to SUn based on timing signals. Here, scan electrode driving circuit 53 includes sustain pulse generating unit 100 for generating a sustain pulse to be described later, and sustain electrode driving circuit 54 includes sustain pulse generating unit 200 in the same manner.

  In the present embodiment, the lighting rate calculation circuit 58 compares the lighting rate between subfields having the same luminance weight in the current field and the immediately preceding field. Timing generation circuit 55 controls the timing signal supplied to sustain electrode drive circuit 54 based on the comparison result in lighting rate calculation circuit 58 and the detected lighting rate.

  Next, a driving voltage waveform for driving the panel and its operation will be described. FIG. 4 is a diagram showing drive voltage waveforms applied to the respective electrodes of the panel used in the embodiment of the present invention. One field is divided into a plurality of subfields, and each subfield has an initialization period and an address period. Have a maintenance period. In this embodiment, one field is divided into 10 subfields (first SF, second SF,..., 10th SF), and each subfield is (1, 2, 3, 6, 11, In the following description, the luminance weights are 18, 30, 44, 60, 81).

  In the initializing period of the first SF, first, in the first half, the data electrodes D1 to Dm and the sustain electrodes SU1 to SUn are held at 0V, and the discharge starts from the voltage Vi1 that is lower than the discharge start voltage with respect to the scan electrodes SC1 to SCn. A ramp voltage that gradually increases toward the voltage Vi2 exceeding the voltage is applied. Then, a weak initializing discharge is caused in all discharge cells, negative wall voltages are accumulated on scan electrodes SC1 to SCn, and positive wall voltages are accumulated on sustain electrodes SU1 to SUn and data electrodes D1 to Dm. The Here, the wall voltage on the electrode refers to a voltage generated by wall charges accumulated on the dielectric layer covering the electrode, the phosphor layer, or the like.

  Subsequently, in the second half of the initialization period, sustain electrodes SU1 to SUn are maintained at positive voltage Ve1, and a ramp voltage that gradually decreases from voltage Vi3 to voltage Vi4 is applied to scan electrodes SC1 to SCn. Then, a weak initializing discharge occurs again in all the discharge cells, the wall voltage between scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn is weakened, and the positive wall voltage on data electrodes D1 to Dm is reduced. Is adjusted to a value suitable for the write operation.

  Thus, in the present embodiment, the initialization operation of the first SF is an all-cell initialization operation in which initialization discharge is performed on all discharge cells.

  In the subsequent address period, sustain electrodes SU1 to SUn are held at voltage Ve2, and scan electrodes SC1 to SCn are held at voltage Vc. Next, a negative scan pulse voltage Va is applied to scan electrode SC1 in the first row, and data electrode Dk (k = 1 to m) of the discharge cell to be displayed in the first row among data electrodes D1 to Dm. A positive address pulse voltage Vd is applied. At this time, the voltage at the intersection of the data electrode Dk and the scan electrode SC1 is obtained by adding the wall voltage on the data electrode Dk and the wall voltage on the scan electrode SC1 to the externally applied voltage (Vd−Va). The starting voltage is exceeded. Then, an address discharge occurs between data electrode Dk and scan electrode SC1 and between sustain electrode SU1 and scan electrode SC1, and a positive wall voltage is accumulated on scan electrode SC1 of this discharge cell, and on sustain electrode SU1. And a negative wall voltage is also accumulated on the data electrode Dk. In this manner, an address operation is performed in which address discharge is caused in the discharge cells to be displayed in the first row and wall voltage is accumulated on each electrode. On the other hand, the voltage at the intersection of the data electrodes D1 to Dm to which the address pulse voltage Vd is not applied and the scan electrode SC1 does not exceed the discharge start voltage, so that address discharge does not occur. The above address operation is sequentially performed until the discharge cell in the nth row, and the address period ends.

  In the subsequent sustain period, driving is performed using a power recovery circuit in order to reduce power consumption. The details of the drive voltage waveform will be described later, and here, the outline of the sustain operation in the sustain period will be described. First, positive sustain pulse voltage Vs is applied to scan electrodes SC1 to SCn, and a ground potential, that is, 0 V is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the address discharge has occurred, the voltage between scan electrode SCi and sustain electrode SUi is the sum of sustain pulse voltage Vs and the wall voltage on scan electrode SCi and the wall voltage on sustain electrode SUi. Exceeding the discharge start voltage. Then, a sustain discharge occurs between scan electrode SCi and sustain electrode SUi, and phosphor layer 35 emits light by the ultraviolet rays generated at this time. Then, a negative wall voltage is accumulated on scan electrode SCi, and a positive wall voltage is accumulated on sustain electrode SUi. Further, a positive wall voltage is accumulated on the data electrode Dk. In the discharge cells in which no address discharge has occurred during the address period, no sustain discharge occurs, and the wall voltage at the end of the initialization period is maintained.

  Subsequently, 0 V is applied to scan electrodes SC1 to SCn, and sustain pulse voltage Vs is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the sustain discharge has occurred, since the voltage between sustain electrode SUi and scan electrode SCi exceeds the discharge start voltage, a sustain discharge occurs again between sustain electrode SUi and scan electrode SCi, and the sustain cell is maintained. Negative wall voltage is accumulated on electrode SUi, and positive wall voltage is accumulated on scan electrode SCi. Thereafter, similarly, the number of sustain pulse voltages corresponding to the luminance weight is alternately applied to scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, and a potential difference is applied between the electrodes of the display electrode pair, thereby writing in the write period. The sustain discharge is continuously performed in the discharge cell that has caused the discharge.

  At the end of the sustain period, a so-called narrow pulse-like potential difference is applied between the scan electrodes SC1 to SCn and the sustain electrodes SU1 to SUn, and the positive wall charges on the data electrode Dk are left while scanning. The wall voltage on the electrode SCi and the sustain electrode SUi is erased. Specifically, after sustain electrodes SU1 to SUn are once returned to 0V, sustain pulse voltage Vs is applied to scan electrodes SC1 to SCn. Then, a sustain discharge occurs between sustain electrode SUi and scan electrode SCi in the discharge cell in which the sustain discharge has occurred. The voltage Ve1 is applied to the sustain electrodes SU1 to SUn before the discharge converges, that is, while charged particles generated by the discharge remain sufficiently in the discharge space. Accordingly, the potential difference between the sustain electrode SUi and the scan electrode SCi is weakened to the extent of (Vs−Ve1). Then, the wall voltage between the scan electrodes SC1 to SCn and the sustain electrodes SU1 to SUn is the difference between the voltages applied to the respective electrodes (Vs−Ve1) while leaving the positive wall charges on the data electrode Dk. It is weakened to the extent of. Hereinafter, this discharge is referred to as “erase discharge”. Further, the potential difference applied between scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn in order to generate erasing discharge is a narrow pulse-shaped potential difference.

  In this way, after applying the voltage Vs for generating the last sustain discharge, that is, the erasing discharge, to the scan electrodes SC1 to SCn, a predetermined time interval (hereinafter referred to as “erasing phase difference Th1”) is set. The voltage Ve1 for reducing the potential difference between the electrodes of the display electrode pair is applied to the sustain electrodes SU1 to SUn. In the sustain period of the first SF, the erase phase difference Th1 is controlled to be 150 nsec regardless of the lighting rate. Thus, the maintenance operation in the maintenance period of the first SF is completed.

  In the initialization period of the second SF, the sustain electrodes SU1 to SUn are held at the voltage Ve1, the data electrodes D1 to Dm are held at 0V, and the ramps gradually drop from the voltage Vi3 ′ to the voltage Vi4 at the scan electrodes SC1 to SCn. Apply voltage. Then, a weak initializing discharge is generated in the discharge cell in which the sustain discharge has been performed in the sustain period of the previous subfield, and the wall voltage on scan electrode SCi and sustain electrode SUi is weakened. For data electrode Dk, since the positive wall voltage is sufficiently accumulated on data electrode Dk in the immediately preceding sustain period, an excessive portion of this wall voltage is discharged, and the wall voltage suitable for the write operation is obtained. Adjusted to On the other hand, discharge cells that have not undergone sustain discharge in the previous subfield are not discharged, and the wall charges at the end of the initialization period of the previous subfield are maintained.

  As described above, the initializing operation of the second SF is a selective initializing operation in which initializing discharge is selectively performed on the discharge cells that have undergone the sustain operation in the sustain period of the immediately preceding subfield.

  Since the operation during the writing period of the second SF is the same as that of the first SF, description thereof is omitted. The operation in the subsequent sustain period is the same except for the number of sustain pulses. The operation in the initialization period from the third SF to the tenth SF is a selective initialization operation similar to that in the second SF, and the write operation in the write period is similar to that in the second SF.

  In this embodiment, the erase phase difference Th1 of the voltage applied to each display electrode pair at the end of the sustain period is controlled by the subfield and the lighting rate of the subfield.

  FIG. 5 is a diagram showing a relationship among the subfield, the lighting rate, and the erasing phase difference Th1 in the present embodiment. As shown in the drawing, in the first to fourth SFs, the erase phase difference Th1 is controlled to be 150 nsec regardless of the lighting rate. On the other hand, in the fifth SF to the tenth SF, the erasing phase difference Th1 is switched depending on the lighting rate. Thus, by switching the erasing phase difference Th1 based on the lighting rate, it is possible to generate a stable address discharge without increasing the scan pulse voltage or the data pulse voltage. This reason will be described in detail later. In this embodiment, the lighting rates of subfields having the same luminance weight in the previous field and the current field are compared and erased when the lighting rate increases or decreases. The value of the lighting rate is changed as a threshold value when the phase difference Th1 is switched. Thereby, a hysteresis characteristic is given to the switching of the erase phase difference Th1.

  That is, when the lighting rate increases, the erasing phase difference Th1 is 150 nsec when the lighting rate is less than 46%, 200 nsec when the lighting rate is 46% or more and less than 72%, and 300 nsec when the lighting rate is 72% or more. When the lighting rate is decreasing, the lighting rate is controlled to be 150 nsec when the lighting rate is less than 42%, 200 nsec when the lighting rate is 42% or more and less than 68%, and 300 nsec when the lighting rate is 68% or more.

  This operation is shown in the drawing. FIG. 6 is a diagram showing the relationship between the lighting rate and the erasing phase difference Th1 in the present embodiment, in which the horizontal axis represents time and the vertical axis represents the lighting rate. As described above, in the present embodiment, in the fifth to tenth SFs, the lighting rates of subfields having the same luminance weight in the previous field and the current field are compared, and the lighting rate increases. It is judged whether or not it is decreasing. Therefore, in FIG. 6, the relationship between the lighting rate and the erasing phase difference Th1 in the fifth SF is shown as an example, and the time on the horizontal axis is obtained by extracting only the fifth SF in each field, and the lighting rate on the vertical axis is the fifth SF. It is expressed as the lighting rate at In the sixth SF to the tenth SF, the same operation as in the case of the fifth SF shown in FIG. 6 is performed.

  As shown in FIG. 6, the lighting rate as a threshold when switching the erasing phase difference Th1 is 46% and 72% when the lighting rate is increasing, that is, when the waveform is rising to the right in the drawing, When the lighting rate is decreasing, that is, when the waveform falls to the right in the screen, it becomes 42% and 68%. Therefore, the erasing phase difference Th1 is switched from 150 nsec to 200 nsec when the lighting rate of the fifth SF reaches 46% when the lighting rate increases, and from 200 nsec when the lighting rate reaches 72%. Switch to 300 nsec. Further, the erasing phase difference Th1 is switched from 300 nsec to 200 nsec when the lighting rate of the fifth SF falls below 68% when the lighting rate is reduced, and from 200 nsec when the lighting rate falls below 42%. Switch to 150 nsec. That is, the erase phase difference Th1 is switched from the first time interval of 150 nsec to a longer second time interval of 200 nsec, for example, when the first time interval is 150 nsec and the second time interval is 200 nsec. The threshold value at the time is 46%, which is larger than the threshold value 42% when switching from the second time interval of 200 nsec to the first time interval of 150 nsec. For example, if the first time interval is 200 nsec and the second time interval is 300 nsec, the threshold value when switching from the first time interval of 200 nsec to a longer second time interval of 300 nsec is as follows: 72%, which is larger than the threshold 68% when switching from 300 nsec, which is the second time interval, to 200 nsec, which is the first time interval.

  As described above, in this embodiment, by switching the erasing phase difference Th1 based on the lighting rate, it is possible to generate a stable address discharge without increasing the scan pulse voltage or the data pulse voltage. Furthermore, in the present embodiment, the value of the erasing phase difference Th1 is changed by changing the value of the lighting rate that is a threshold value when switching the erasing phase difference Th1 depending on whether the lighting rate is increasing or decreasing. Has hysteresis characteristics for switching. This prevents the erasure phase difference Th1 from being frequently switched due to minute fluctuations in the lighting rate near the threshold value.

  Next, details of the operation in the sustain period will be described. First, details of sustain pulse generators 100 and 200, which are drive circuits for applying sustain pulses alternately to each of the display electrode pairs to sustain discharge the discharge cells, will be described. FIG. 7 is a circuit diagram of sustain pulse generating units 100 and 200 of the plasma display device in accordance with the exemplary embodiment of the present invention. Sustain pulse generation unit 100 includes power recovery unit 110 and clamp unit 120. The power recovery unit 110 includes a power recovery capacitor C10, switching elements Q11 and Q12, backflow prevention diodes D11 and D12, and a power recovery inductor L10. The clamp unit 120 includes a power source VS having a voltage value Vs, and switching elements Q13 and Q14. The power recovery unit 110 and the clamp unit 120 are connected to the scan electrode 22 which is one end of the interelectrode capacitance Cp of the panel 10 via a scan pulse generation circuit. In FIG. 7, the scan pulse generation circuit is not shown. In addition, the capacitor C10 has a sufficiently large capacity compared to the interelectrode capacity Cp, is charged to a voltage value of approximately Vs / 2, and functions as a power source for the power recovery unit 110.

  Sustain pulse generator 200 has the same circuit configuration as sustain pulse generator 100, and includes power recovery capacitor C20, switching elements Q21 and Q22, backflow prevention diodes D21 and D22, and power recovery inductor L20. The recovery unit 210 and a clamp unit 220 having a power source VS and switching elements Q23 and Q24 are provided, and the output of the sustain pulse generator 200 is connected to the sustain electrode 23 which is the other end of the interelectrode capacitance Cp of the panel 10. . For later explanation, FIG. 7 also shows a power source VE for applying the voltage Ve1 to the sustain electrode 23, and switching elements Q28 and Q29.

  Next, details of the drive voltage waveform will be described. FIG. 8 is a timing chart for explaining the operation of sustain pulse generating units 100 and 200 of the plasma display apparatus according to the embodiment of the present invention, and is a detailed timing chart of a portion surrounded by a broken line in FIG. First, one period of the sustain pulse is divided into six periods indicated by T1 to T6, and each period will be described.

(Period T1)
At time t1, switching element Q12 is turned on. Then, the charge on the scan electrode 22 side starts to flow to the capacitor C10 through the inductor L10, the diode D12, and the switching element Q12, and the voltage of the scan electrode 22 starts to decrease.

(Period T2)
Since the inductor L10 and the interelectrode capacitance Cp form a resonance circuit, the voltage of the scan electrode 22 decreases to around 0 V at time t2 after the time ½ of the resonance period has elapsed. However, the voltage of the scan electrode 22 does not drop to 0V due to power loss due to the resistance component of the resonance circuit. At time t2, switching element Q14 is turned on. Then, since scan electrode 22 is directly grounded through switching element Q14, the voltage of scan electrode 22 is forcibly lowered to 0V.

  Further, switching element Q21 is turned on at time t2. Then, current starts to flow from the power recovery capacitor C20 through the switching element Q21, the diode D21, and the inductor L20, and the voltage of the sustain electrode 23 starts to rise. In the present embodiment, the above-described resonance period is set to about 1200 nsec, and the time from time t1 to time t2, that is, the time period T1 is set to 550 nsec.

(Period T3)
Since the inductor L20 and the interelectrode capacitance Cp also form a resonance circuit, the voltage of the sustain electrode 23 rises to near Vs at time t3 after the time ½ of the resonance period has elapsed, but the resistance component of the resonance circuit, etc. Therefore, the voltage of the sustain electrode 23 does not rise to Vs. At time t3, the switching element Q23 is turned on. Then, since sustain electrode 23 is directly connected to power supply VS through switching element Q23, the voltage of sustain electrode 23 is forcibly increased to Vs. Then, in the discharge cell in which the address discharge has occurred, the voltage between the scan electrode 22 and the sustain electrode 23 exceeds the discharge start voltage, and a sustain discharge occurs.

  Switching element Q12 may be turned off after time t2 and before time t5, and switching element Q21 may be turned off after time t3 and before time t4. In order to lower the output impedance of sustain pulse generating units 100 and 200, switching element Q14 is preferably turned off immediately before time t5, and switching element Q23 is preferably turned off immediately before time t4.

(Period T4-T6)
Since the sustain pulse applied to scan electrode 22 and the sustain pulse applied to sustain electrode 23 have the same waveform, the operation from period T4 to period T6 is the same as operation from period T1 to period T3. Since it is equivalent to the operation of replacing the electrode 23, the description thereof is omitted.

  The operations in the above periods T1 to T6 are repeated according to the required number of pulses. Note that in this embodiment, the time periods T2, T4, and T5 are set to 550 nsec similarly to the time period T1. In addition, the time periods T3 and T6 are set to 1450 nsec.

  Next, the last erasing discharge in the sustain period will be described in detail divided into four periods T7 to T10.

(Period T7)
This period is the fall of the sustain pulse applied to the sustain electrode 23 and is the same as the period T4. That is, by turning on switching element Q22 at time t7, the charge on sustain electrode 23 side begins to flow to capacitor C20 through inductor L20, diode D22, and switching element Q22, and the voltage on sustain electrode 23 begins to drop.

(Period T8)
At time t8, switching element Q24 is turned on to forcibly reduce the voltage of sustain electrode 23 to 0V. Then, the switching element Q11 is turned on. Then, current starts to flow from the power recovery capacitor C10 through the switching element Q11, the diode D11, and the inductor L10, and the voltage of the scan electrode 22 starts to rise.

(Period T9)
Since the inductor L10 and the interelectrode capacitance Cp form a resonance circuit, the voltage of the scan electrode 22 rises to near Vs after a time ½ of the resonance period has elapsed, but here, the resonance of the power recovery unit The switching element Q13 is turned on in a period shorter than ½ of the period, that is, at time t9 before the voltage of the scan electrode 22 rises to near Vs. Then, since the scan electrode 22 is directly connected to the power source VS through the switching element Q13, the voltage of the scan electrode 22 rapidly rises to Vs. Then, in the discharge cell in which the address discharge has occurred, the voltage between the scan electrode 22 and the sustain electrode 23 exceeds the discharge start voltage, and a sustain discharge occurs. Further, the switching element Q24 is turned off immediately before time t10.

(Period T10)
At time t10, switching element Q28 and switching element Q29 are turned on. Then, since sustain electrode 23 is directly connected to power supply VE through switching elements Q28 and Q29, the voltage of sustain electrode 23 is forcibly increased to Ve1. The time t10 is a time before the discharge generated in the period T9 converges, that is, the charged particles generated by the discharge sufficiently remain in the discharge space. Since the electric field in the discharge space changes while the charged particles remain sufficiently in the discharge space, the charged particles are rearranged to relax the changed electric field to form wall charges. At this time, since the difference between the voltage Vs applied to scan electrode 22 and voltage Ve1 applied to sustain electrode 23 is small, the wall voltage on scan electrode 22 and sustain electrode 23 is weakened. Thus, the potential difference that generates the last sustain discharge is a narrow pulse-shaped potential difference that is changed so as to reduce the potential difference applied between the electrodes of the display electrode pair before the last sustain discharge converges. The sustain discharge to be performed is an erasing discharge. Further, the data electrode 32 is held at 0 V at this time, and the charged particles caused by the discharge have wall charges so as to reduce the potential difference between the voltage applied to the data electrode 32 and the voltage applied to the scanning electrode 22. As a result, a positive wall voltage is formed on the data electrode 32.

  Here, the erase phase difference Th1 is applied until the voltage Ve1 for reducing the potential difference between the electrodes of the display electrode pair is applied to the sustain electrode 23 after the voltage Vs for generating the erase discharge is applied to the scan electrode 22. In the present embodiment, the control is performed using a switching element. That is, the switching element Q13, which is the first switching element for applying the voltage Vs for generating the sustain discharge to the scan electrode 22, and the voltage Ve1 for relaxing the potential difference between the electrodes of the display electrode pair are maintained. Switching elements Q28 and Q29, which are second switching elements to be applied to, and after turning on the switching element Q13, a time interval corresponding to the lighting rate of the discharge cells in the subfield (hereinafter referred to as “erasing phase difference Th2”). The switching elements Q28 and Q29 are turned on. At this time, the erasing phase difference Th1 and the erasing phase difference Th2 may not be exactly equal, but may be considered to be practically equivalent unless there is a large difference in the delay time of the switching elements. Therefore, hereinafter, the erasure phase difference Th1 and the erasure phase difference Th2 are not distinguished from each other, and are simply referred to as an erasure phase difference Th.

  The time from time t9 to time t10, that is, the time period T9 is the erase phase difference Th. As shown in FIGS. 5 and 6, the subfield, the lighting rate of the subfield, and the immediately preceding field It is controlled depending on whether the lighting rate of the subfield having the same luminance weight as that of the current field is increasing or decreasing. That is, in the first to fourth SFs, the erasure phase difference Th is controlled to be 150 nsec regardless of the lighting rate. Further, the erase phase difference Th1 in the fifth SF to the tenth SF is compared with the lighting rate of the subfield having the same luminance weight in the previous field and the current field, and when the lighting rate is increased, The lighting rate is controlled to be 150 nsec when the lighting rate is less than 46%, 200 nsec when the lighting rate is 46% or more and less than 72%, and 300 nsec when the lighting rate is 72% or more. It is controlled to be 150 nsec, 200 nsec when the lighting rate is 42% or more and less than 68%, and 300 nsec when the lighting rate is 68% or more.

  As described above, after a voltage for generating an erasing discharge, which is the last sustaining discharge, is applied to the display electrode pair in the sustaining period, the erasing phase difference is a time interval corresponding to the lighting rate of the discharge cells in the subfield. A voltage is applied to the display electrode pair so as to reduce the potential difference between the electrodes of the display electrode pair with Th. The potential difference for generating the erasing discharge is a narrow pulse potential difference obtained by changing the potential difference applied between the electrodes of the display electrode pair before the last sustain discharge converges.

  Further, in the present embodiment, as shown in FIGS. 5 and 6, the erasure phase difference Th is equal to the erasure phase difference Th in the subfield with a small luminance weight, as shown in FIGS. The erase phase difference Th when the discharge cell lighting rate is high is controlled to be longer than the erase phase difference Th when the discharge cell lighting rate is low. By controlling in this way, a stable address discharge can be generated without increasing the scan pulse voltage or the data pulse voltage.

  Further, in the present embodiment, the erasing phase difference Th1 is changed by changing the lighting rate value that is a threshold value when the erasing phase difference Th1 is switched between when the lighting rate is increasing and when the lighting rate is decreasing. Hysteresis characteristics are given to the switching. This prevents the erasure phase difference Th1 from being frequently switched due to minute fluctuations in the lighting rate near the threshold value.

  Next, the reason why a stable address discharge can be generated without increasing the scan pulse voltage and the data pulse voltage by the panel driving method in this embodiment will be described.

  As described above, the erasing discharge by the narrow-width pulse changes the electric field in the discharge space while the charged particles generated by the discharge remain sufficiently in the discharge space, and the charging is performed so as to relax the changed electric field. The desired wall charges are formed by rearranging the particles to form wall charges. Therefore, when the erasing phase difference Th is increased, charged particles generated by discharge are recombined, and charged particles for relaxing the electric field are insufficient to form a desired wall charge. As a result, it has been confirmed that the number of address failures (hereinafter referred to as “first-type address failures”) in which no address discharge occurs in the discharge cells to be discharged increases.

  FIG. 9A is a diagram schematically showing the relationship between the address pulse voltage necessary for generating a normal address discharge and the erase phase difference Th, where the horizontal axis represents the erase phase difference Th and the vertical axis represents the erase phase difference Th. An address pulse voltage necessary for generating a normal address discharge is shown. As shown in this drawing, it has been confirmed by experiments that the address pulse voltage required for reliably generating the address discharge in the discharge cells to be discharged increases as the erase phase difference Th increases.

  On the other hand, it has been clarified through experiments that the scan pulse voltage necessary for generating a normal address discharge increases when the erase phase difference Th becomes too small. The magnitude of the scan pulse voltage is a voltage for distinguishing between discharge cells in a selected row and discharge cells in a non-selected row. Actually, when this scan pulse voltage is reduced, the wall charge of the discharge cells in the unselected row is taken away while the address discharge is being generated in any of the discharge cells in any row, so that the address discharge is originally generated. Address failure (hereinafter referred to as “second type address failure”) occurs in which the wall voltage is insufficient and address discharge does not occur.

  FIG. 9B schematically shows the relationship between the scan pulse voltage necessary for generating a normal address discharge and the erase phase difference Th. The horizontal axis represents the erase phase difference Th, and the vertical axis represents the erase phase difference Th. The scan pulse voltage necessary for generating a normal address discharge is shown. As shown in this figure, it has been clarified through experiments that the scan pulse voltage necessary for generating a normal address discharge increases as the erase phase difference Th decreases. When the scan pulse voltage necessary for generating a normal address discharge is increased, the above-described second type of address failure is liable to occur. To prevent this, the scan pulse voltage must be increased. As described above, since the first type of write failure and the second type of write failure are opposite to the erase phase difference Th, the erase phase difference Th is practically prevented from generating either write failure. It was found that it was desirable to set a proper value.

  As a result of further detailed examination, it has been clarified that the optimum erase phase difference Th becomes longer as the lighting rate of the subfield becomes higher. FIG. 9C is a diagram schematically showing the relationship between the scan pulse voltage necessary for generating a normal address discharge and the lighting rate, where the horizontal axis indicates the lighting rate and the vertical axis indicates the normal address discharge. The scan pulse voltage required to generate As shown in the drawing, it has been found that as the lighting rate increases, the scan pulse voltage required to generate a normal address discharge increases. Therefore, it was found that when the scan pulse voltage is constant, the generation of discharge tends to be delayed. This is because the discharge current increases as the lighting rate increases, the voltage drop associated therewith increases, the effective voltage applied to the discharge cells decreases, and the scan pulse voltage required to generate a normal address discharge. Can be considered high. Therefore, it is considered that when the scan pulse voltage is constant, the effective voltage applied to the discharge cell is lowered and the generation of discharge is delayed.

  When the discharge is delayed, the width of the narrow potential difference that causes the erasing discharge is equivalently narrowed, that is, the discharge is the same as the erasing phase difference Th is shortened. FIG. 10 is a diagram schematically showing the relationship between the scan pulse voltage necessary for generating a normal address discharge, the erase phase difference Th, and the lighting rate. As shown in FIG. 10, the smaller the erase phase difference Th, the higher the scan pulse voltage required to generate a normal address discharge, and the higher the lighting rate, the more necessary to generate a normal address discharge. The scan pulse voltage becomes high. Therefore, the optimum erasure phase difference Th is longer in the subfield with a high lighting rate than in the subfield with a low lighting rate.

  As described above, in the present embodiment, when the lighting rate is small, the erasing phase difference Th is controlled to the above-described predetermined value, and the erasing phase difference Th is increased as the lighting rate increases. Optimize narrow pulse width. As a result, the optimum erasing phase difference Th can always be maintained regardless of the lighting rate, and optimum driving can be performed.

  In the present embodiment, in addition to this, the control of the erase phase difference Th is changed for each subfield. FIG. 11 is a diagram showing the lower limit value of the scan pulse voltage at which the second type of write failure does not occur when the erase phase difference Th in each subfield is set to 150 nsec. As described above, when the erasing phase difference Th is shortened, the scanning pulse voltage increases. However, as shown in FIG. 11, the degree becomes more remarkable as the luminance weight of the subfield increases. This is because, in a subfield with a large luminance weight, priming due to sustain discharge increases, so that the discharge cell walls of the unselected rows are generated while the address discharge is generated in the discharge cells of the selected row in the address period. It can be considered that the rate at which the wall voltage for address discharge decreases increases because charges are easily taken away.

  On the contrary, in the subfield having a small luminance weight, the rate at which the wall voltage for the address discharge decreases becomes small, and the scan pulse voltage can be set lower than that in the subfield having a large luminance weight. Therefore, in the subfield having a small luminance weight, even if the lighting rate increases and the scanning pulse voltage for preventing the second type of writing failure increases to some extent, the scanning pulse voltage required in the subfield having a large luminance weight does not exceed. It is not necessary to perform control according to the lighting rate as long as possible.

  As described above, in the present embodiment, the erasure phase difference Th in the subfield with a small luminance weight is controlled to be equal to or shorter than the erasure phase difference Th in the subfield with a large luminance weight, so that the discharge cell The erase phase difference Th when the lighting rate is high is controlled to be longer than the erase phase difference Th when the discharge rate of the discharge cells is low. By adopting such control, stable address discharge can be generated without increasing the scan pulse voltage and data pulse voltage.

  In general, when the erase phase difference Th is changed, the light emission luminance accompanying the erase discharge also changes. Therefore, if the erase phase difference Th is changed frequently, the brightness of the display image may become unstable. However, in the present embodiment, by fixing the erasing phase difference Th in a subfield having a small luminance weight, the emission luminance associated with the erasing discharge is made constant, and fluctuations in luminance are prevented to improve image display quality. .

  Further, in the present embodiment, as described above, by changing the value of the lighting rate that is a threshold value when switching the erasing phase difference Th1 between when the lighting rate is increasing and when it is decreasing. The hysteresis characteristic is given to the switching of the erase phase difference Th1. This prevents frequent switching of the erasing phase difference Th1 due to minute fluctuations in the lighting rate in the vicinity of the threshold value, thereby realizing a display image with higher quality.

  Note that the time values of the periods T1 to T10 illustrated in the present embodiment are examples, and the present invention is not limited to these values, and is preferably set according to the discharge characteristics of the panel. .

  In the present embodiment, it has been described that the all-cell initialization operation is performed during the initialization period of the first SF, and the selective initialization operation is performed during the initialization period of the second SF. The present invention is not limited, and all cell initialization and selective initialization operations may be arbitrarily performed in each subfield.

  Further, in the present embodiment, one field is divided into 10 subfields (first SF, second SF,..., 10th SF), and each subfield is (1, 2, 3, 6, 11, 18, 30, 44, 60, 81). However, in the present invention, the number of subfields and the luminance weight of each subfield are not limited to the above values.

  Further, in the present embodiment, the erasing phase difference Th is controlled to be 150 nsec regardless of the lighting rate in the first SF to the fourth SF, and when the lighting rate is increased in the fifth SF to 10th SF, When the lighting rate reaches 46%, control is performed from 150 nsec to 200 nsec, and when the lighting rate reaches 72%, from 200 nsec to 300 nsec. When the lighting rate decreases, the lighting rate decreases to 68%. Although it has been described that the control is performed from 300 nsec to 200 nsec when it falls below and from 200 nsec to 150 nsec when the lighting rate falls below 42%, the present invention is not limited to this. It may be switched at an appropriate lighting rate. Further, the erasing phase difference Th may be controlled to change substantially continuously according to the lighting rate. By controlling in this way, the influence of the change in the erase phase difference Th on the display image also changes continuously, so that the image display quality is also improved.

  The panel driving method of the present invention can perform an address operation with a low address pulse voltage even for a high-luminance and high-definition panel, and is useful as a plasma display device using the panel.

The disassembled perspective view which shows the principal part of the panel used for embodiment of this invention. Electrode arrangement of the panel Circuit block diagram of plasma display device using the panel The figure which shows the drive voltage waveform impressed to each electrode of the panel The figure which shows the relationship between the subfield in the embodiment of this invention, a lighting rate, and an erasing phase difference The figure which showed the relationship between the lighting rate and erasure | elimination phase difference in embodiment of this invention The circuit diagram of the sustain pulse generation part of the plasma display apparatus in embodiment of this invention Timing chart for explaining the operation of the sustain pulse generator of the plasma display device in accordance with the exemplary embodiment of the present invention. FIG. 5A is a diagram schematically showing the relationship between the address pulse voltage necessary for generating a normal address discharge and the erase phase difference. FIG. 5B shows a scan pulse required for generating a normal address discharge. FIG. 5C schematically showing the relationship between the voltage and the erase phase difference schematically shows the relationship between the scan pulse voltage and the lighting rate necessary for generating a normal address discharge. A diagram schematically showing the relationship between the scan pulse voltage necessary for generating a normal address discharge, the erase phase difference, and the lighting rate The figure which shows the lower limit of the scanning pulse voltage which a 2nd type write failure does not generate | occur | produce

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Panel 22 Scan electrode 23 Sustain electrode 32 Data electrode 51 Image signal processing circuit 52 Data electrode drive circuit 53 Scan electrode drive circuit 54 Sustain electrode drive circuit 55 Timing generation circuit 58 Lighting rate calculation circuit 100,200 Sustain pulse generation part 110,210 Power recovery unit 120,220 Clamp unit

Claims (6)

A method of driving a plasma display panel comprising a plurality of discharge cells having a display electrode pair consisting of a scan electrode and a sustain electrode,
One field period includes a plurality of address periods in which an address discharge is selectively generated in the discharge cells, and a sustain period in which the number of sustain discharges is generated in proportion to a luminance weight in the discharge cells in which the address discharge is generated. Consisting of subfields,
In the sustain period, after the voltage for generating the last sustain discharge is applied to the display electrode pair, the display electrode is spaced at a time interval that is switched with hysteresis characteristics based on the lighting rate of the discharge cells in the subfield. A driving method of a plasma display panel, wherein a voltage for relaxing a potential difference between a pair of electrodes is applied to the display electrode pair. A plasma display panel having a plurality of discharge cells each having a display electrode pair consisting of a scan electrode and a sustain electrode, wherein an address period for selectively generating an address discharge in the discharge cells and an address discharge are generated in one field period. A plurality of subfields having a sustain period in which the number of sustain discharges in proportion to the luminance weight is generated in the discharge cell, and a first voltage for applying a voltage for generating the sustain discharge to the display electrode pair A plasma display panel driving method for driving using a switching element and a second switching element for applying a voltage for relaxing a potential difference between electrodes of the display electrode pair to the display electrode pair,
When the last sustain discharge is generated in the sustain period, after the first switching element is turned on, the first switching element is turned on at a time interval that is switched with a hysteresis characteristic based on the lighting rate of the discharge cells in the subfield. 2. A driving method of a plasma display panel, wherein the switching element is turned on. The time interval is switched based on a comparison between the lighting rate of the discharge cells in the current subfield and a predetermined threshold value, and when switching from the first time interval to a second time interval longer than that. The threshold value of is set to a value larger than a threshold value when switching from the second time interval to the first time interval. Driving method of plasma display panel. 4. The lighting ratio of a discharge cell is compared between subfields having the same luminance weight in the current field and the immediately preceding field, and the threshold value is changed based on the result. Driving method of plasma display panel. As a result of the comparison, the threshold value when the lighting rate of the discharge cell is increased is set to a value larger than the threshold value when the lighting rate of the discharge cell is decreased. The method of driving a plasma display panel according to claim 4, wherein: At least one subfield controlled to switch the time interval based on the result of comparison between the lighting rate of the discharge cells in the current subfield and a predetermined threshold value is included in one field period. The method for driving a plasma display panel according to claim 3.

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