Abstract:
A plasma display panel driving apparatus that is capable of reducing the number of optical conductive devices. In the plasma display panel driving apparatus, a first controller generates control data for controlling the driving integrated circuits. A second controller drives the first controller. An optical conductive device for transmitting a light signal from the second control to the first control.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a driving apparatus for a plasma display panel, and more particularly to a plasma display panel driving apparatus that is capable of reducing the number of optical conductive devices. 
     2. Description of the Related Art 
     Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of HE+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system. 
     The PDP of AC driving system is expected to be highlighted into a future display device because it has advantages in the low voltage drive and a prolonged life in comparison to the PDP of DC driving system. Also, the PDP of alternating current driving system allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. The AC-type PDP makes a memory effect because it uses a dielectric material into the surface of which a wall charge is accumulated during the discharge. 
     Referring to FIG.  1  and FIG. 2, the AC-type PDP includes a front substrate  1  provided with sustaining electrodes  10 , and a rear substrate  2  provided with address electrodes  4 . The front substrate  1  and the rear substrate  2  are spaced, in parallel to each other, with having a barrier rib  3  therebetween. A mixture gas such as Ne—Xe or He—Xe, etc. is injected into a discharge space defined by the front substrate  1  and the rear substrate  2  and the barrier rib  3 . These sustaining electrodes  10  make a pair by two within a single plasma discharge channel. One of a pair of sustaining electrodes  10  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in the address interval to cause an opposite discharge along with the address electrodes  4 , and responds to a sustaining pulse applied in the sustaining interval to cause a surface discharge along with the adjacent sustaining electrodes  10 . Also, the sustaining electrodes  10  adjacent to the sustaining electrode  10  used as the scanning/sustaining electrode  10  used as a common sustaining electrode to which a sustaining pulse is applied commonly. On a front substrate  1  provided with the sustaining electrodes  10 , a dielectric layer  8  and a protective layer  9  are disposed. The dielectric layer  8  and a responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film  9  prevents a damage of the dielectric layer  8  caused by a sputtering generated during the plasma discharge and improves an emission efficiency of secondary electrons. This protective film is usually made from MgO. Barrier ribs  3  for dividing the discharge space is extended perpendicularly at the rear substrate  2 . On the surfaces of the rear substrate  2  and the barrier ribs  3 , there is provided a fluorescent layer  5  excited by a vacuum ultraviolet lay to generate a visible light. 
     As shown in FIG. 3, the PDP  20  has m×n discharge pixel cells  11  arranged in a matrix pattern. At each of the discharge pixel cells  11 , scanning/sustaining electrode lines Yl to Ym, hereinafter referred to as “Y electrode lines”, and common sustaining electrode lines Z 1  to Zm electrode lines Xl to Xn, hereinafter referred to as “electrode lines ” are crossed with respect to each other. The Y electrode lines Y 1  to Ym and the Z electrode lines Z 1  to Zm consist of the sustaining electrodes  10  making a pair. The X electrode lines X 1  to Xn consist of the address electrodes  4 . 
     FIG. 3 is a schematic view of a PDP driver shown in FIG.  1 . In FIG. 3, the PDP driver includes a scanning/sustaining driver  22  for driving the Y electrode lines Y 1  to Ym, a commons sustaining driver  24  for driving the Z electrode lines Z 1  to Zm, and first and second address drivers  26 A and  26 B for driving the X electrode lines X 1  to Xn. The scanning/sustaining driver  22  is connected to the Y electrode lines Y 1  to Ym to thereby select a scanning line to be displayed and generate a sustaining discharge at the selected scanning line. The common sustaining driver  24  is commonly connected to the Z electrode lines Z 1  to Zm to apply sustaining pulses with same waveform to all the Z electrode lines Z 1  to Zm, thereby causing the sustaining discharge. The first address driver  26 A supplies odd-numbered X electrode lines X 1 , X 3 , . . . , Xn- 3 , Xn- 1  with a video data, whereas the second address driver  26 B supplies even-numbered X electrode lines X 2 , X 4 , . . ., Xn- 2 , Xn with a video data. 
     In such a PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. In the reset interval, the entire field is initialized. In the address interval, the discharge pixel cells  11  to be displayed by a data are selected by the address discharge. The selected discharge pixel cells  11  sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2 n  depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eight sub-fields is lengthened at a ratio of 2 0 , 2 1 , 2 3 , 2 4 , 2 5 , 2 6  and 2 7 . To this end, the number of sustaining pulses generated in the sustaining interval also increases into 2 0 , 2 1 , 2 3 , 2 4 , 2 5 , 2 6  and 2 7  depending on the sub-fields . The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields. 
     A method of driving a PDP is largely classified into an address display separated (ADS) system in which the entire field is divided into an address interval and a sustaining interval, and an address while sustaining (AWS) system in which one field is divided into a number of blocks and an address interval and a sustaining interval coexist within one field. 
     FIG. 4 is a block diagram showing the configuration of a PDP driving apparatus of ADS system emphasized on the scanning/sustaining driver. In FIG. 4, the PDP driving apparatus of ADS system includes a PDP  20  having 480 Y electrode lines Y 1  to Y 480 , a scanning/sustaining driver  30  for driving the Y electrode lines Y 1  to Y 480  sequentially, photo-couplers  32 A to  32 D for transmitting a control data Cdata generated from a microcomputer  34  and common control signals CC 1  to CC 3  to the sustaining driver  30 , and first and second waveform generators  36 A and  36 B for applying a scanning pulse and a sustaining pulse to the sustaining driver  30 . The sustaining driver  30  consists of first to eighth driver integrated circuits (ICs)  30 A to  30 H to the first photo-coupler  32 A in cascade. Each of the driver ICs  30 A to  30 H responds to the control data Cdata from the first photo-coupler  32 A to driver  60  Y electrode lines sequentially. In other words, the driver ICs  30 A to  30 H respond to the control data Cdata to be sequentially driven, thereby applying a scanning pulse to the first Y electrode line Yl to the 480th Y electrode line Y 480  sequentially in the address interval. The driver ICs  30 A to  30 H respond to the common control signals CC 1  to CC 3  at the moment of transiting from the address interval into the sustaining interval to drop voltages at the  480  Y electrodes Y 1  to Y 480  simultaneously into a ground level, and thereafter apply a sustaining pulse to the Y electrode lines Y 1  to Y 480  commonly in the sustaining interval. The first photo-coupler  32 A compensates for a ground level of the microcomputer  34  and a ground level of the scanning/sustaining driver different from each other to apply the control data Cdata from the microcomputer  34  to the first driver IC  30 A. Likewise, the second to fourth photo-couplers  32 B to  32 D compensate for a ground level of the microcomputer  34  and a ground level of the scanning/sustaining driver  30  different from each other to apply a control data Cdata from the microcomputer  34  to control terminals of the sustaining driver  30 . To this end, the photo-couplers  32 A to  32 D are insulated between the input and the output thereof, and deliver an input signal to the output in a shape of light signal. As shown in FIG. 5, the photo-couplers  32 A to  32 D include a photo diode PD connected between the microcomputer  34  and a primary ground voltage source GND 1 , and a photo transistor PT connected between a secondary voltage supply VCC 2  and a secondary ground voltage source GND 2 . The phototransistor PD is radiated in accordance with an output signal of the microcomputer  34  applied from a first resistor R 1  for limiting a current to generate a light. The NPN-type photo transistor PT applies a control data Cdata having a contrary phase with respect to an output signal of the microcomputer  34  or the common control signals CC 1  to CC 3  to the driver ICs  30 A to  30 H in an incidient light from the photo diode PD received to its gate terminal. A second resistor R 2  is connected between a collector terminal of the phototransistor PT and a secondary common voltage source VCC 2  coupled with the driver ICs  30 A to  30 D. The first and second waveform generators  36 A and  36 B play a role to apply high-level voltages and low-level voltages of the scanning pulse and the sustaining pulse to the scanning/sustaining driver  30 , respectively. The PDP driving apparatus of ADS system uses one photo-coupler for supplying a control data and three to fifth photo-coupler for supplying common control signals. 
     FIG. 6 is a block diagram showing the configuration of a PDP driving apparatus of AWS system emphasized on the scanning/sustaining driver. In FIG. 6, the PDP driving apparatus of AWS system includes a PDP  20  having 480 Y electrode lines Y 1  to Y 480 , a scanning/sustaining driver  40  for making a divisional driving of 60 lines of the Y electrode lines Y 1  to Y 480 , photo-couplers  42 A to  42 K for transmitting control data Cdata 1  to Cdata 8  from a microcomputer  44  and common control signals CC 1  to CC 3  to the sustaining driver  40 , and first and second waveform generators  46 A and  46 B for applying a scanning pulse and a sustaining pulse to the sustaining driver  40 . The sustaining driver  40  consists of first to eight driver ICs  40 A to  40 H connected to each of the photo-couplers  42 A to  42 K in serial. Each of the driver ICs  40 A to  40 H responds to the control data Cdata 1  to Cdata 8  in such a manner that each block on the field including 60 scanning lines is addressed or sustained independently, thereby driving 60 Y electrode lines independently. In other words, each of the driver ICs  40 A to  40 H responds to the control data Cdata 1  to Cdata 8  to be driven independently, thereby applying a scanning pulse from the first and second waveform generators  46 A and  46 B to the Y electrode lines Y 1  to Y 480 . The driver ICs  40 A to  40 H respond to the common control signals CC 1  to CC 3  at the moment of transisting from the address interval into the sustaining interval to drop voltages at the 480 Y electrodes Y 1  to Y 480  simultaneously into a ground level, and thereafter apply sustaining pulses from the first and second waveform generators  46 A and  46 B to the Y electrode lines Y 1  to Y 480  commonly in the sustaining interval. The photo-couplers  42 A to  42 K compensate for a ground level of the microcomputer  44  and a ground level of the scanning/sustaining driver  40  different from each other to apply the control data Cdata 1  to Cdata 8  from the microcomputer  34  and the common control signals CC 1  to CC 3  to the scanning/sustaining driver  40 . As shown in FIG. 5, each of the photo-couplers  42 A to  42 D consists of a photo diode PD and an photo transistor PT that are separated from each other to transmit a light signal. The first and second waveform generators  36 A and  36 B play a role to apply high-level voltages and low-level voltages of the scanning pulse and the sustaining pulse, respectively, under control of the microcomputer  34 . On the other hand, a common sustaining driver for driving the Z electrode lines for each block also consists of a plurality of driver ICs and photo-couplers. For instance, the PDP driving apparatus of AWS system typically uses 16 to 32 photo-couplers. 
     As described above, the conventional PDP driving apparatus must have a number of photo-couplers  32 A to  32 D or  42 A to  42 K so as to apply control data from the microcomputer  34  or  44  or common control signals to the driver ICs  30 A to  30 H or  40 A to  40 H by compensating for ground levels of the microcomputers  34  or  44  and the driver ICs  30 A to  30 H or  40 A to  40 H. Furthermore, as the number of photo-couplers  32 A to  32 D or  42 A to  42 K is larger, the number of output lines in the microcomputer  34  or  44  becomes larger. Accordingly, the conventional PDP driving apparatus causes a cost rise as well as a complicate driving circuit due to a number of photo-couplers  32 A to  32 D or  42 A to  42 K and a number of signal wiring. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a PDP driving apparatus that is capable of reducing the number of optical conductive devices. 
     In order to achieve these and other objects of the invention, a PDP driving apparatus according to one aspect of the present invention includes first control means for producing control data for controlling the driving integrated circuits; second control means for driving the first control means; and an optical conductive device for transmitting a light signal from the second control means to the first control means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing the structure of a conventional three-electrode, AC-type plasma display panel; 
     FIG. 2 is a sectional view showing the structure of a single discharge pixel cell in the plasma display panel in FIG. 1; 
     FIG. 3 is a schematic plan view showing the plasma display panel in FIG. 1 and a driving apparatus thereof; 
     FIG. 4 is a schematic block diagram showing the configuration of a conventional PDP driving apparatus of ADS system; 
     FIG. 5 is an equivalent circuit diagram of the photo-coupler shown in FIG. 4; 
     FIG. 6 is a schematic block diagram showing the configuration of a conventional PDP driving apparatus of AWS system; 
     FIG. 7 is a schematic block diagram showing the configuration of a PDP driving apparatus of ADS system according to an embodiment of the present invention; and 
     FIG. 8 is a schematic block diagram showing the configuration of A PDP driving apparatus of AWS system according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 7, there is shown a plasma display panel (PDP) driving apparatus of ADS system according to an embodiment of the present invention which is emphasized on a scanning/sustaining driver. The PDP driving apparatus of ADS system includes a PDP  20  having 480 Y electrode lines Y 1  to Y 480 , a scanning/sustaining driver  50  for driving the Y electrode line Y 1  to Y 480  sequentially, A first microcomputer  54  for generating a timing trigger signal, a second microcomputer  58  for responding to the trigger signal to generate a control data Cdata and common control signals CC 1  to CC 3 , a photo-coupler  52  for transmitting the timing trigger signal from the first microcomputer  54  to the second microcomputer  58 , and first and second waveform generator  56 A and  56 B for applying a scanning pulse and a sustaining pulse to the sustaining driver  50 . The sustaining driver  50  consists of first to eight ICs  50 A to  50 H connected in cascade, to the second microcomputer  58 . Each of the driver ICs  50 A to  50 H responds to a control data Cdata from the second microcomputer  58  to drive  60  Y electrode lines sequentially. In other words, the driver ICs  50 A to  50 H respond to the control data to be sequentially driven, thereby applying a scanning pulse to the first to 480th Y electrode line Y 1  to Y 480  sequentially in the address interval. The driver ICs  50 A to  50 H respond to the common control signals CC 1  to CC 3  at the moment of transiting from the address interval in the sustaining interval to drop voltages at the 480 Y electrode lines Y 1  to Y 480  into a ground level, and thereafter apply a sustaining pulse to the Y electrode lines Y 1  to Y 480  commonly in the sustaining interval. A ground voltage GND 2  of the second microcomputer  58  is set in the same value as those of driver ICs  50 A to  50 H. Accordingly, since ground levels of the driver ICs  50 A to  50 H are set in compliance with the sustaining voltage, a ground level of the first microcomputer  54  also is set to have a high value. For instance, a ground level of the first microcomputer  54  and a supply voltage VCC 1  are 0V and 5V, respectively, whereas a ground level of the second microcomputer  58  and a supply voltage VCC 2  may be set to 20V and 25V, respectively. The photo-coupler  52  is connected, via a first resistor R 1 , to the first microcomputer  54  and, at the same time, is connected, via a second resistor R 2 , to a voltage supply VCC 2  of the second microcomputer  58 . The photo-coupler  52  compensates for ground levels of the first and second microcomputers  54  and  58  different from each other to apply a timing trigger signal from the first microcomputer  54  to the second microcomputer  58 . As shown in FIG. 5, the photo-coupler  52  consists of a photo diode PD at the input thereof and a phototransistor PT that are electrically insulated. A collector terminal of the phototransistor PT is connected, via the second resistor R 2 , to an output terminal of the first waveform generator  56 A and the voltage supply VCC 2  of the second microcomputer  58 . An emitter terminal of the phototransistor PT is connected to an output terminal of the second waveform generator  56 A and the second voltage supply VCC 2  of the second microcomputer  58 . The voltage supply VCC 2  applied to the second microcomputer  58  from the photo-coupler  52  and the ground voltage GND 2  maintain a voltage difference of 5V like the first microcomputer. Since a collector voltage and an emitter voltage of the photo transistor  58  change in a similar manner even when an alternating current (AC) pulse signal is generated from the first and second waveform generators  56 A and  56 B, the voltage supply VCC 1  of the second microcomputer  58  and the ground voltage GND 2  always remains at 5V. The second microcomputer  58  supplies the control data Cdata to the first driver IC  50 A and, at the same time, supplies the common control signals CC 1  to CC 3  to common terminals of the driver ICs  50 A to  50 H in accordance with a timing trigger signal from the photo coupler  52 . The first and second waveform generators  56 A and  56 M apply high-level voltages and low-level voltages of the scanning pulse and the sustaining pulse, respectively, to the scanning/sustaining driver  50  under control of the first microcomputer  54 . 
     Referring to FIG. 8, there is shown a PDP driving apparatus of AWS system according to an embodiment of the present invention, which is emphasized, on a scanning/sustaining driver. The PDP driving apparatus of AWS system includes a PDP  20  having 480 Y electrode lines Y 1  to Y 480 , a scanning/sustaining driver  60  for making a divisional driving of 60 lines of the Y electrode lines Y 1  to Y 480 , a first microcomputer  64  for generating a timing trigger signal, a second microcomputer  68  for responding to the timing trigger signal to generate a control data Cdata and common control signals CC 1  to CC 3 , a photo-coupler  62  for transmitting the timing trigger signal from the first microcomputer  65  to the second microcomputer  68 , and first and second waveform generators  66 A and  66 B for applying a scanning pulse and a sustaining pulse to the sustaining driver  60 . The sustaining driver  60  consists of first to eighth driver ICs  60 A to  60 H connected, in serial, to the output terminal of the second microcomputer  68 . Each of the driver ICs  60 A to  60 H responds to a control data Cdata from the second microcomputer  58  to driver  60  Y electrode lines sequentially. In other words, the respective driver ICs  50 A to  50 H respond to control data Cdata 1  to Cdata  8  in such a manner that each block in the field including 60 scanning lines can be addressed and sustained independently, thereby driving 60 Y electrode lines independently. In other words, the respective driver ICs  60 A to  60 H respond to the control data Cdata 1  to Cdata 8  to be driven independently, thereby applying a scanning pulse to the Y electrode lines Y 1  to Y 480  in the address interval. The driver ICs  60 A to  60 H respond to the common control signals CC 1  to CC 3  at the moment of transiting from the address interval into the sustaining interval to drop voltages at the 480 Y electrode lines Y 1  to Y 480  into a ground level simultaneously, and thereafter apply a sustaining pulse to the Y electrode lines Y 1  to Y 480  commonly in the sustaining interval. A ground voltage GND 2  of the second microcomputer  58  is set in the same value as those of the driver ICs  60 A to  60 H. Accordingly, since ground levels of the driver ICs  60 A to  60 H are set in compliance with the sustaining voltage, a ground level of the second microcomputer  68  also is set to have a high value. The photo-coupler  62  is connected, via a first resistor R 1 , to the first microcomputer  64  and, at the same time, is connected, via a second resistor R 2 , to a voltage supply VCC 2  of the second microcomputer  68 . The photo-coupler  62  compensates for ground levels of the first and second microcomputers  64  and  68  different from each other to apply a timing trigger signal from the first microcomputer  64  to the second microcomputer  68 . As shown in FIG. 5, the photo-coupler  52  consists of a photo diode PD at the input thereof and a phototransistor PT that are electrically insulated. The voltage supply VCC 2  applied to the second microcomputer  68  from the photo-coupler  62  and the ground voltage GND 2  maintain a voltage difference of 5V like the first microcomputer  64 . The second microcomputer  68  supplies the control data CData 1  to Cdata 8  to the driver ICs  60 A to  60 H, respectively and, at the same time, supplies the common control signals CC 1  to CC 3  to common terminals of the driver ICs  60 A to  60 H in accordance with a timing trigger signal from the photo coupler  52 . The first and second waveform generators  66 A and  66 B apply high-level voltages and low-level voltages of the scanning pulse and the sustaining pulse, respectively, to the scanning/sustaining driver  60  under control of the first microcomputer  65 . 
     As described above, the PDP driving apparatus according to the present invention is provided with the microcomputers having the same ground level as those of the driver ICs and controlling the driver ICs directly. In the PDO driving apparatus, the optical conductive device for compensating for a ground level difference between two microcomputers with a different ground level to transmit a signal is installed between the two microcomputers. 
     Accordingly, the PDP driving apparatus according to the present invention can minimize the number of optical conductive devices by providing a single optical conductive device between two microcomputers with a different ground level instead of removing a number of optical conductive devices installed between the microcomputer and the driver ICs. Also, since the number of optical conductive devices installed between the microcomputer and the driver ICs is reduced, the number of output terminals of the microcomputer and signal wiring can be reduced to that extent. As a result, the PDP driving apparatus according to the present invention is capable of lowering the cost as well as simplifying the driving circuit. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.