Abstract:
A plasma display apparatus includes a data driver and a plasma display panel having a first address electrode and a second address electrode. The data driver is configured to initiate a change in a voltage value of a first data signal supplied to the first address electrode at a first initiation time, and to initiate a change in a voltage value of a second data signal supplied to the second address electrode at a second, different initiation time. Each of the data signals gradually changes from a first data voltage to a second data voltage during a respective first period, maintains at the second data voltage during a respective second period, and gradually changes from the second data voltage to a third data voltage during a respective third period.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 10-2006-0043604 filed on May 15, 2006, which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    This document is related to driving a plasma display apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    A plasma display apparatus includes a plasma display panel having electrodes and a driver that supplies driving signals to the electrodes. The plasma display panel includes discharge cells partitioned by a barrier rib. Phosphor is formed within the discharge cells. 
         [0006]    When certain driving signals are supplied to the electrodes of the plasma display panel, a sustain discharge is generated within a discharge cell. As a result of the sustain discharge, discharge gas in the discharge cell generates vacuum ultraviolet rays that cause the phosphor to emit light. 
         [0007]    Before an occurance of the sustain discharge, a reset discharge initializing wall charges of the discharge cell, and an address discharge selecting a discharge cell where a sustain discharge will occur are generated within the discharge cell. 
       SUMMARY 
       [0008]    In one general aspect, a plasma display apparatus includes a data driver and a plasma display panel having first and second address electrodes. The data driver is configured to initiate a change in a voltage value of a first data signal supplied to the first address electrode at a first initiation time, and to initiate a change in a voltage value of a second data signal supplied to the second address electrode at a second, different initiation time. Each of the data signals gradually changes from a first data voltage to a second data voltage during a respective first period, maintains at the second data voltage during a respective second period, and gradually changes from the second data voltage to a third data voltage during a respective third period. 
         [0009]    In another general aspect, driving a plasma display apparatus includes initiating a change in a voltage value of a first data signal supplied to a first address electrode at a first initiation time, and initiating a change in a voltage value of a second data signal supplied to a second address electrode at a second, different initiation time. Each of the data signals gradually changes from a first data voltage to a second data voltage during a respective first period, maintains at the second data voltage during a respective second period, and gradually changes from the second data voltage to a third data voltage during a respective third period. 
         [0010]    Implementations may include one or more of the following features. For example, the first data voltage and the third data voltage may be substantially the same. Also, the first and second address electrodes may be adjacent to each other. The difference between the first initiation time and the second initiation time may range from 0.2 times to 1 times the duration of the first period for the first data signal. The time difference between the first and second initiation times may range from 10 ns to 300 ns. 
         [0011]    The duration of the respective first period may be between 5% and 20% of the duration of the respective second period. In terms of slopes, the slope of each of the data signals during the respective first period may range between 0.1 V/ns and 1 V/ns. 
         [0012]    A scan driver may initiate a change in a voltage value of a scan signal supplied to a scan electrode at a third initiation time. The scan signal may gradually change from a first scan voltage to a second scan voltage during a fourth period, maintain at the second scan voltage during a fifth period, and gradually change from the second scan voltage to a third scan voltage during a sixth period. The slope of the scan signal during the fourth period may be different from the slope of the first data signal during the first period. The third initiation time may be different from the first and second initiation times. 
         [0013]    Other features will be apparent from the following description, including the drawings, and the claims. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a block diagram of a plasma display apparatus; 
           [0015]      FIG. 2  is a perspective view of a plasma display panel of the plasma display apparatus of  FIG. 1 ; 
           [0016]      FIG. 3  is a timing diagram of signals of the plasma display apparatus of  FIG. 1 ; 
           [0017]      FIG. 4   a  is a graph of driving signals of the plasma display apparatus of  FIG. 1 ; 
           [0018]      FIG. 4   b  is a graph of a scan signal and a data signal of the plasma display apparatus of  FIG. 1 ; 
           [0019]      FIG. 5  is a graph of data signals of the plasma display apparatus of  FIG. 1 ; 
           [0020]      FIG. 6  is a schematic diagram of electrodes in the plasma display panel of  FIG. 2 ; 
           [0021]      FIG. 7  is a graph of data signals of the plasma display apparatus of  FIG. 1 ; 
           [0022]      FIG. 8   a  is a circuit diagram of a basic unit of a data driver of the plasma display apparatus of  FIG. 1 ; 
           [0023]      FIG. 8   b  is a switching timing diagram of the data driver of  FIG. 8   a;    
           [0024]      FIG. 9   a  and  FIG. 9   b  are images displayed on the plasma display apparatus of  FIG. 1 ; and 
           [0025]      FIGS. 10   a ,  10   b  and  11  are graphs of data signals. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1  illustrates a plasma display apparatus  100  that includes a plasma display panel  105 , a scan driver  110 , a sustain driver  115 , and a data driver  120 . 
         [0027]    The plasma display panel  105  includes discharge cells  125 , scan electrodes Y 1 , . . . , Yn, sustain electrodes Z 1 , . . . , Zn, and address electrodes X 1 , . . . , Xm, including first and second address electrodes X 1  and X 2  that are adjacent to each other. 
         [0028]    The scan driver  110  supplies, to the scan electrodes Y 1 , . . . , Yn, a reset signal initializing the wall charge state of discharge cells, a scan signal selecting discharge cells to emit light, and a sustain signal that causes the emission of light from the selected discharge cells. 
         [0029]    The sustain driver  115  supplies, to the sustain electrodes Z 1 , . . . , Zn, a sustain bias signal that helps the selection of the discharge cells and a sustain signal that causes emission of light from the selected discharge cells. 
         [0030]    The data driver  120  supplies data signals to the address electrodes X 1 , . . . , Xm at different supply time points. The data signals gradually rise to a data voltage during a first period, are maintained at the data voltage during a second period, and gradually fall from the data voltage during a third period. The address electrodes include a first address electrode and a second address electrode. The data driver  120  supplies a first data signal to the first address electrode, and a second data signal to the second address electrode. The supply start time point of the second data signal, which is the point in time when the first data signal starts to rise in the first period, is different from the supply start time point of the first data signal. The first data signal or the second data signal gradually rises to the data voltage during a first period, is maintained at the data voltage during a second period, and gradually falls from the data voltage during a third period. 
         [0031]    The scan driver  110  supplies a scan signal corresponding to the first data signal and the second data signal. 
         [0032]      FIG. 2  illustrates a perspective view of an exemplary plasma display panel of a plasma display apparatus. As illustrated in  FIG. 2 , the plasma display panel  105  includes a front panel  200  and a rear panel  210 . The front panel  200  includes a front substrate  201  on which a scan electrode  202  and a sustain electrode  203  are formed. The rear panel  210  includes a rear substrate on which address electrodes  213  crossing the scan electrode  202  and the sustain electrode  203  are formed. 
         [0033]    An upper dielectric layer  204  covers the scan electrode  202  and the sustain electrode  203 . 
         [0034]    The scan electrode  202  and the sustain electrode  203  may include transparent electrodes  202   a  and  203   a  and bus electrodes  202   b  and  203   b . The transparent electrodes  202   a  and  203   a  are made of Indium Tin Oxide. The bus electrodes  202   b  and  203   b  improve the electric conductivity. 
         [0035]    Alternatively, the scan electrode  202  and the sustain electrode  203  of  FIG. 2  may includes only the bus electrodes  202   b  and  203   b.    
         [0036]    The upper dielectric layer  204  limits a discharge current of the scan electrode  202  and the sustain electrode  203 , and insulates the scan electrode  202  and the sustain electrode  203 . The upper dielectric layer  204  comprises a glass material including R 2 O and metal oxide MO 2 . 
         [0037]    The metal oxide MO 2  includes at least one of MnO 2 , CeO 2 , SnO 2 , or SbO 2 , each of which has 3 or 4 valence. R 2 O includes at least one of Li 2 O, Na 2 O, K 2 O, Rb 2 O, Cs 2 O, Cu 2 O, or Ag 2 O. MO 2  prevents Ag ions or Cu ions of the scan electrode  202  or the sustain electrode  203  from diffusing throughout the upper dielectric layer  204 . Accordingly, a discoloration of the upper dielectric layer  204   204  is prevented. MO 2  may range from 0.5 wt % to 10 wt % of the total weight of the dielectric layer. When MO 2  ranges from 0.5 wt % to 10 wt % of the total weight of the dielectric layer, R 2 O decreases the softening point of a glass, and improves the liquidity of the glass. 
         [0038]    A protective layer  205  is positioned on the upper dielectric layer  204 , and improves a discharge condition. The protective layer is formed by the diposition of magnecium oxide MgO. 
         [0039]    The address electrodes  213  supply data signals to discharge cells. A lower dielectric layer  215  covers the address electrodes  213 , and insulates the address electrodes  213 . 
         [0040]    The lower dielectric layer  215  includes PbO, SiO2, B2O3, Al 2 O 3  and CuO. CuO may range from 0.2 wt % to 0.4 wt % of the total weight of the lower dielectric layer  215 . CuO decreases the viscosity of a dielectric paste. Accordingly, when CuO ranges from 0.2 wt % to 0.4 wt % of the total weight of the lower dielectric layer  215 , CuO prevents the generation of bubbles inside the lower dielectric layer  215 , and thereby decreases the necessary driving voltage. As a result of the decrease of the driving voltage, noise and electromagnetic interference are reduced. 
         [0041]    A stripe type barrier rip or a well type barrier rib  212  is formed on the lower dielectric layer  215 . The barrier rib partitions discharge cells. A discharge gas is filled in the discharge cells. A phosphor  214  is formed within the discharge cells. 
         [0042]      FIG. 3  explains an exemplary method of implementing gray scales in the plasma display apparatus. 
         [0043]    As shown in  FIG. 3 , in order to implement the gray scale, each image frame is divided into sub-fields SF 1  to SF 8 . Each sub-field is also divided into a reset period for initializing all of the discharge cells, an address period for selecting discharge cells to emit light, and a sustain period for emitting light from the selected discharge cells. The sub-fields have different durations of the sustain periods. The grey scale of each discharge cell is implemented by selecting some sub-fields to emit light with proper durations of the sustain periods. For example, if it is desired to display an image with 256 gray scales, a frame period (16.67 ms) corresponding to 1/60 of a second is divided into eight sub-fields SF 1  to SF 8 . 
         [0044]    The time duration and the number of sustain pulses that are associated with each sustain period increase by the ratio of 2n (where, n=0,1,2,3,4,5,6,7) for each sub-field SF 1  to SF 8 . For example, the duration of the sustaion period of sub-field SF 2  is twice the duration of the sustaion period of sub-field SF 1 . As such, since the duration of the sustain period varies from one sub-field to the next, the gray scale of a discharge cell is achieved by controlling which sustain periods are to be used to emit light from the discharge cell, i.e., by controlling the number of the sustain discharges that are realized in the discharge cell. 
         [0045]      FIG. 4   a  illustrates driving signals of the plasma display apparatus. 
         [0046]    The scan driver  110  supplies, to the scan electrode, a rising ramp signal gradually rising to a sum voltage Vs+Vsetup, which is the summation of a sustain voltage Vs and a setup voltage Vsetup, during a setup period of a reset period. The sustain voltage Vs is the highest voltage of a sustain signal. 
         [0047]    The rising ramp signal generates a weak dark discharge, i.e., a setup discharge, in the discharge cells. As a result of the setup discharge, wall charges sufficient for the generation of an address discharge are accumulated within the discharge cells. The slope of the rising ramp signal may range between 0.0005V/nsec and 0.005V/nsec. 
         [0048]    The scan driver supplies a falling ramp signal gradually falling from a positive voltage, which is lower than the sum voltage Vs+Vsetup, during a setdown period. The falling ramp signal generates a weak erase discharge, i.e., a setdown discharge, within the discharge cells. As a result of the setdown discharge, some of the wall charges accumulated within the discharge cells are erased. The slope of the falling ramp signal may range between −0.0005V/nsec and −0.005V/nsec. 
         [0049]    The scan driver  110  supplies to the scan electrode a scan signal which falls from a scan reference voltage Vsc to a scan voltage −Vy, is maintained at the scan voltage −Vy, and rises to the scan reference voltage Vsc. 
         [0050]    The data driver  120  supplies a first data signal and a second data signal, which correspond to the scan signal, to the first address electrode and the second address electrode respectively. The first and second address electrodes are adjacent to each other. The first data signal and the second data signal are supplied at different supply time points t 1 , t 2 . The first data signal or the second data signal gradually rises to a data voltage Vd during a first period, is maintained at the data voltage Vd during a second period, and gradually falls from the data voltage Vd during a third period. 
         [0051]    The durations of the first and the third periods may be between 5% and 20% of the duration of the second period. The durations of the first and the third periods may be between between 50 nsec and 200 nsec. The slope of the data signal during the first period may range between 0.1V/nsec and 1V/nsec. The slope of the data signal during the third period may range between −0.1 V/nsec and −1 V/sec. 
         [0052]    When the first data signal or the second data signal as above is supplied, noise and Electro Magnetic Interference due to a voltage variation are reduced because the voltage on the first address electrode and the second address electrode varies gradually. 
         [0053]    Also, the supply of the first and second data signals at different supply start time points t 1  and t 2  reduces noise. When the data signals are supplied at the same supply start time point, the voltage difference between the data signals and the scan signal increases noise. On the other hand, when the data signals are supplied at the different supply start time points t 1  and t 2 , noises generated by the voltage difference of the data signals and the scan signal are spread in time, and the whole noise is reduced. 
         [0054]    When the difference Δt between the supply start time points t 1  and t 2  of the data signals may range from 0.2 times to 1 times the duration of the first period, the noise and the electro magnetic interference are effectively reduced. 
         [0055]    When the difference Δt between the supply start time points t 1  and t 2  of the data signals ranges from 0.4 times to 0.8 times the duration of the first period, the scan signal and the data signals sufficiently overlap for a stable address discharge, and at the same time, the noise and the electro magnetic interference are reduced. 
         [0056]    When the difference Δt between the supply start time points t 1  and t 2  ranges from 10 ns to 300 ns, the noise and the electro magnetic interference are reduced, while preventing an excessive increase of the address period. 
         [0057]    The supply start time points t 1  and t 2  of the data signals may be different from the supply start time point t 3  of the scan signal. Then, the noise generated between the scan electrode and the first address electrode or the second electrode is reduced. 
         [0058]    The sustain driver  115  supplies a sustain bias voltage Vzb to the sustain electrode during the address period. The sustain bias voltage Vzb prevents the occurrence of an erroneous discharge generated by the interference between the sustain electrode and the scan electrode during the address period. 
         [0059]    The scan driver  110  and the sustain driver  115  supply sustain signals to the scan electrode and the sustain electrode during the sustain period. As a result of the supply of the sustain signals, the discharge cells selected during the address period emit light. In another implementation, the scan driver  110  may supply a sustain signal swinging from a positive sustain voltage to a negative sustain voltage to the scan electrode and the sustain driver  115  may supply a ground level voltage to the sustain electrode during the sustain period. 
         [0060]      FIG. 4   b  illustrates exemplary waveforms of the scan signal and the data signal. As illustrated in  FIG. 4   b , the scan signal may gradually fall from the scan reference voltage Vsc to the scan voltage −Vy during a fourth period. The slope of the data signal during the first period may be different from that of the scan signal during the fourth period. 
         [0061]    When the voltage on the scan electrode and the voltage on the address electrode change gradually and the slope of the scan signal during the fourth period is different from the slope of the data signal during the first period, noise is reduced. 
         [0062]      FIG. 5  illustrates supply start time points of data signals supplied to address electrodes. As illustrated in  FIG. 5 , data signals are applied to address electrodes X 1 , X 2 , X 3  and X 4  at different supply start time points t 0 , t 1 , t 2  and t 3 , respectively. As a result, the noise is reduced. 
         [0063]    The plasma display panel of the plasma display apparatus may include address electrodes which are divided into address electrode groups. Dada signals are supplied simultaneously to address electrodes in the same address electrode group. However, data signals are supplied at different times to address electrodes in different address electrode groups.  FIG. 6  illustrates an exemplary grouping of address electrodes. The plasma display panel of  FIG. 6  includes 4 address electrode groups AEG 1  to AEG 4 . The number of address electrodes in each address electrode group may be same or different. 
         [0064]      FIG. 7  illustrates first and second data signals. As illustrated in  FIG. 7 , a first data signal is supplied to address electrodes of address electrode group AEG 1  at a supply start time point t 1 , and a second data signal is supplied to address electrodes of address electrode group AEG 2  at a supply start time point t 2 . By supplying the data signals at different times to address electrodes of different address electrode groups, the noise generated between the scan electrodes and the address electrodes is reduced. 
         [0065]      FIG. 8   a  illustrates an exemplary structure of the basic unit  500  of the data driver of the plasma display apparatus and  FIG. 8   b  illustrates a switching timing diagram of the data driver of  FIG. 8   a . The data driver includes basic units for each address electrode. 
         [0066]    As illustrated in  FIG. 8   a , the basic unit  500  of the data driver of the plasma display apparatus includes a data drive integrated circuit  530  connected to the first address electrode or the second address electrode, a data voltage supply unit  510  for supplying a data voltage Vd to the first address electrode or the second address electrode through the data drive integrated circuit  530 , and an energy recovery unit  520  for gradually increasing a voltage of the first address electrode or the second address electrode to the data voltage Vd or decreasing the voltage of the first address electrode or the second address electrode from the data voltage Vd. 
         [0067]    The operation of the data driver basic unit  500  in  FIG. 8   a  to generate a data signal is explained below with reference to  FIG. 8   b . As illustrated in  FIG. 8   b , when a switch Q 2  and a switch Qt are turned on during the first period, an energy stored at a capacitor C is supplied to the first address electrode or the second address electrode through the switch Q 2 , an inductor L and the switch Qt. The inductor L forms a resonance, and the voltage on the first address electrode or the second address electrode gradually rises from a ground level voltage GND to a data voltage Vd. 
         [0068]    When a switch Q 1  and the switch Qt are turned on and the other switches are turned off during the second period, the data voltage Vd is supplied to the first address electrode or the second address electrode. A voltage on the first address electrode or the second address electrode is maintained at the data voltage Vd. 
         [0069]    When a switch Q 3  and the switch Qt are turned on and the other switches are turned off during the third period, the capacitor C recovers the energy from the first address electrode or the second address electrode through the switch Qt, the inductor L, and the switch Q 3 . The inductor L forms a resonance, and the voltage on the first address electrode or the second address electrode gradually falls from the data voltage Vd to the ground level voltage GND. 
         [0070]    When the switch Qb is turned on and the other electrodes are turned off at the end of the third period, the ground level voltage GND is supplied to the first address electrode or the second address electrode. 
         [0071]    Diodes D 1 , D 2 , D 3 , Dt and Db of  FIG. 8   a  are body diodes of the switches Q 1 , Q 2 , Q 3  Qt and Qb respectively. Diodes D 5  and D 6  cut off a reverse current. 
         [0072]      FIG. 9   a  and  FIG. 9   b  are screen images displayed by the plasma display apparatus to explain the relationship between the switching operation and the load of the data driver basic unit. 
         [0073]      FIG. 9   a  illustrates a full black image displayed by the plasma display apparatus. In order to display the full black image of  FIG. 9   a , the switches Qb and Qt of the data drive integrated circuit  530  in  FIG. 8   a  respectively maintains a turn-on state and a turn-off state. Thus, the switching operation of the data driver basic unit is not performed, and the load substantially is equal to 0. That is to say, a switching frequency is substantially equal to 0, and the load substantially is equal to 0. 
         [0074]      FIG. 9   b  illustrates a lattice pattern image displayed by the plasma display apparatus. In order to display the lattice pattern image, the switching frequency of the switch Qt and the switch Qb of  FIG. 8   a  and the load of the data driver basic unit  500  become the maximum. The load is proportional to the switching frequency. 
         [0075]    As the switching frequency increases, a noise and an electro magnetic interference increase. In order to decrease the noise and the electro magnetic interference, the data driver  120  may supply the data signals to the first address electrode and the second address electrode at different supply time points according to the load of each address electrode, which is proportional to the switching frequency of the data driver basic unit for each address electrode. 
         [0076]    The supply time point of the data signal may be adjusted based on the load. For example, as illustrated in  FIG. 10   a , when the load is less than a threshold, a supply start time point t 1  of the first data signal for the first address electrode is substantially the same as a supply start time point t 2  of the second data signal for the second address electrode.  FIG. 10   a  may correspond to  FIG. 9   a.    
         [0077]    For example, as illustrated in  FIG. 10   b , when the load is greater than the threshold, a supply start time point t 1  of the first data signal for the first address electrode is earlier than a supply start time point t 2  of the second data signal for the second address electrode. When the difference of the supply start time points t 1  and t 2  ranges from 10 ns to 300 ns, the noise and the electro magnetic interference are reduced. To implement this, the data driver basic unit  500  of  FIG. 8   a  may further include a detection circuit to detect the load of the electrode and adjust the supply start time point accordingly.  FIG. 10   b  may correspond to  FIG. 9   b.    
         [0078]      FIG. 11  illustrates an exemplary relationship between the first period of the data signal and the load. The duration and the supply start time point of the data signal may be adjusted based on the load. For example, as illustrated in  FIG. 11 , the first period of the data signal for a high load is shorter than that for a low load. When the duration of the first period of a data signal for the lowest load ranges from 1.5 times to 5 times the duration of the first period of a data signal for the highest load, the noise and the electro magnetic interference are reduced. Therefore, a stable address discharge is generated and a driving efficiency improves. When the duration of the first period for the lowest load ranges from 2 times to 4 times the duration of the first period for the highest load, an excessive increase of the address period is prevented. In order to implement these features, the data driver basic unit  500  of  FIG. 8   a  may further include a detection circuit to detect the load and adjust the duration of the first period of the data signal accordingly. 
         [0079]    Other implementations are within the scope of the following claims.