Patent Abstract:
A plasma display apparatus includes a display panel in which display cells are constituted at least by a set of electrodes including first electrodes extending in a first direction, second electrodes extending in the first direction, and third electrodes extending in a second direction substantially perpendicular to the first direction, a first drive circuit configured to drive the first electrodes, a second drive circuit configured to drive the second electrodes, a third drive circuit configured to drive the third electrodes in conjunction with successive scanning of the first electrodes, and a power-supply circuit configured to generate a DC voltage based on an AC voltage and to supply the DC voltage to the first drive circuit and the second drive circuit, wherein the power-supply circuit and a given drive circuit that is one of the first drive circuit and the second drive circuit are implemented on a single print circuit board.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to an image display apparatus, and particularly relates to a plasma display apparatus. 
         [0003]    2. Description of the Related Art 
         [0004]    A plasma display panel has two glass substrates which have electrodes formed thereon and define a space therebetween that is filled with discharge gas, and generates electric discharge by applying voltages between the electrodes so as to induce light emission from fluorescent substance provided on the substrates in response to the ultraviolet light generated by the electric discharge, thereby displaying an image. Plasma display panels are widely used as large-screen display apparatuses due to the facts that a large-sized screen is easy to make, that the self-light-emission nature ensures high display quality, and that the response speed is high. 
         [0005]    On a display panel, X electrodes and Y electrodes extending in parallel are formed, and address electrodes are provided to run perpendicularly to the X and Y electrodes. The X and Y electrodes serve to generate sustain discharges for display-purpose light emission. The sustain discharges are generated by applying voltage pulses repeatedly between the X electrodes and the Y electrode. The Y electrodes also serve as scan electrodes for use in the writing of display data. The address electrodes serve to select discharge cells that emit light, and apply address-voltage pulses responsive to display data in order to generate write discharge for selecting the discharge cells between the Y electrodes and the address electrodes. 
         [0006]      FIG. 1  is a block diagram showing a main part of a related-art plasma display apparatus. A plasma display apparatus shown in  FIG. 1  includes a plasma display panel  11 , an address-electrode drive circuit  12 , a Y-electrode drive circuit  13 , an X-electrode drive circuit  14 , a scan circuit  15 , a drive control circuit  16 , a signal processing circuit  17 , and an AC/DC power supply circuit  18 . 
         [0007]    The signal processing circuit  17  receives a clock signal, display data, a vertical synchronizing signal, a horizontal synchronizing signal, etc., which are supplied from an external source, and performs various tasks such as the writing of RGB display data to a frame memory in response to the vertical synchronizing signal. The drive control circuit  16  controls the address-electrode drive circuit  12 , the Y-electrode drive circuit  13 , the X-electrode drive circuit  14 , and the scan circuit  15  to display the display data stored in the frame memory on the plasma display panel  11 . 
         [0008]    Specifically, the drive control circuit  16  generates address control signals responsive to the display data in the frame memory in synchronization with the clock signal. The address control signals are supplied to the address-electrode drive circuit  12 . The drive control circuit  16  further generates scan driver control signals for controlling the scan circuit  15  in synchronization with the vertical synchronizing signal and the horizontal synchronizing signal. The scan driver control signals are supplied to the scan circuit  15 . The drive control circuit  16  further drives the Y-electrode drive circuit  13  and the X-electrode drive circuit  14  in synchronization with the vertical synchronizing signal and the horizontal synchronizing signal. 
         [0009]    The address-electrode drive circuit  12  applies address-voltage pulses responsive to the display data to address electrodes A 1  through Am in synchronization with the clock signal. The Y-electrode drive circuit  13  drives Y electrodes Y 1  through Yn independently of each other via the scan circuit  15 . The X-electrode drive circuit  14  drives X electrodes X 1  through Xn all together. 
         [0010]    Through the operations of the address-electrode drive circuit  12 , the Y-electrode drive circuit  13 , the X-electrode drive circuit  14 , and the scan circuit  15 , each display pixel is initialized in a reset period, followed by an address period in which pixels to be displayed are selected, and, in a sustain period that comes last, the selected pixels are caused to emit light. 
         [0011]    In the reset period, a reset/address-voltage generating circuit inside the Y-electrode drive circuit  13  generates a reset voltage, so that the scan circuit  15  applies the reset voltage to all the Y electrodes Y 1  through Yn. Further, a reset voltage generated by a reset/address-voltage generating circuit inside the X-electrode drive circuit  14  is applied to all the X electrodes X 1  through Xn. 
         [0012]    In the address period, the scan circuit  15  drives the Y electrodes Y 1  through Yn successively one by one based on the address voltage generated by the reset/address-voltage generating circuit of the Y-electrode drive circuit  13 , and, in conjunction therewith, the address-electrode drive circuit  12  applies address-voltage pulses for one horizontal line responsive to the display data to the address electrodes A 1  through Am. Cells to be displayed are selected in this manner, thereby controlling the display/non-display (selection/non-selection) of each display cell (pixel). 
         [0013]    In the sustain period, sustain voltage pulses generated by a sustain-pulse circuit of the Y-electrode drive circuit  13  are applied to the Y electrodes Y 1  through Yn via the scan circuit  15 , and sustain voltage pulses generated by a sustain-pulse circuit of the X-electrode drive circuit  14  are applied to the X electrodes X 1  through Xn. The application of these sustain voltage pulses generates sustain discharge between an X electrode and a Y electrode at the cells selected as display cells. These sustain voltage pulses are generated based on a sustain voltage VS 0 . The AC/DC power supply circuit  18  converts a commercial AC power supply voltage into a DC power supply voltage, which is supplied as the sustain voltage VS 0  to the X-electrode drive circuit  14  via an electric cable  18   a . Further, the sustain voltage VS 0  is supplied from the X-electrode drive circuit  14  to the Y-electrode drive circuit  13  via an electric cable  18   b.    
         [0014]      FIG. 2  is a drawing showing an example of the configuration of the related-art AC/DC power supply circuit  18 . The AC/DC power supply circuit  18  includes a rectifying circuit  21 , a pulse generating circuit  22 , a transformer  23 , a diode  24 , a light-emission device  25 , a light-detection device  26 , a smoothing condenser Cvs 0 , and resistors R 1  and R 2  serving as a voltage detection circuit. 
         [0015]    The rectifying circuit  21  rectifies an AC voltage supplied from a commercial AC power supply, and supplies the rectified voltage to the pulse generating circuit  22 . The pulse generating circuit  22  generates a rectangular-pulse voltage waveform based on the rectified voltage supplied from the rectifying circuit  21 . This pulse voltage waveform causes an electric current to be generated at the output terminal of the transformer  23 . This electric current flows into the smoothing condenser Cvs 0  through the diode  24 , thereby charging the smoothing condenser Cvs 0 . A voltage between the opposite ends of the smoothing condenser Cvs 0  is divided by the resistors R 1  and R 2 , so that the light-emission device  25  emits light with intensity responsive to the divided voltage level. The light-detection device  26  receives light from the light-emission device  25 , and supplies a signal responsive to the intensity of the received light to the pulse generating circuit  22 . The pulse generating circuit  22  controls the generation of the pulses in response to the signal from the light-detection device  26 . This feedback control serves to adjust the voltage between the opposite ends of the smoothing condenser Cvs 0  to a predetermined voltage (i.e., to the sustain discharge voltage VS 0 ). 
         [0016]    The transformer  23  transmits an electric power from the primary side to the secondary side via changes in magnetic flux, so that the input side and output side of the transformer  23  are not electrically connected with each other (i.e., not directly connected through an electrical conductor). An optical coupling unit  27  comprised of the light-emission device  25  and the light-detection device  26  transmits information from the input side to the output side via changes in light intensity, so that the input side and output side are not electrically connected with each other (i.e., not directly connected through an electrical conductor). In this manner, the primary side and the secondary side are electrically insulated from each other. 
         [0017]      FIG. 3  is a drawing showing an example of the circuit configuration of the related-art X-electrode drive circuit  14 . The X-electrode drive circuit  14  includes an energy-supply-purpose condenser Cvs 1 , power MOS-field-effect transistors Q 1  through Q 4 , diodes D 1  and D 2 , inductors L 1  and L 2 , and a charge-collection-purpose condenser C 1 . An illustrated capacitance Cp 1  represents the capacitance of the plasma display panel  11 , and, in particular, is the capacitance of the X electrodes of the plasma display panel  11 . What is shown in  FIG. 3  is a portion corresponding to the sustain circuit for generating sustain discharges that is provided in the X-electrode drive circuit  14 . The X-electrode drive circuit  14  further includes circuit portions for supplying the reset voltage and the like, which are omitted in  FIG. 3 . 
         [0018]    At the initial stage of the performing of sustain discharge, the capacitor Cp 1  has no electric charge accumulated therein and is placed at the ground potential while the charge-collection-purpose condenser C 1  has accumulated electric charge and exhibits a voltage of about VS 0 /2. In this state, the power MOS-field-effect transistor Q 3  is turned on to become conductive, so that the electric charge of the charge-collection-purpose condenser C 1  flows into the capacitor Cp 1  via the diode D 1  and the inductor L 1 . As a result, the capacitor Cp 1  exhibits a voltage of about VS 0  through the resonance of the inductor L 1  and the capacitor Cp 1 . Thereafter, in order to maintain the X electrodes of the plasma display panel  11  at a constant voltage, the power MOS-field-effect transistor Q 1  is turned on to supply the voltage VS 0  from the energy-supply-purpose condenser Cvs 1  to the plasma display panel  11 . Consequently, sustain discharge is generated. Here, the energy-supply-purpose condenser Cvs 1  receives the sustain-discharge voltage VS 0  supplied from the AC/DC power supply circuit  18 . 
         [0019]    After this, the power MOS-field-effect transistor Q 1  is turned off, and the power MOS-field-effect transistor Q 4  is turned on, so that electric charge flows into the charge-collection-purpose condenser C 1  from the capacitor Cp 1  via the inductor L 2  and the diode D 2 . With this arrangement, the electric charge that has been used to charge the capacitor Cp 1  of the plasma display panel  11  can be collected. The power MOS-field-effect transistor Q 2  is then turned on to remove the electric charge of Cp 1  remaining after the collection, thereby setting the X electrodes to the ground potential. 
         [0020]      FIG. 4  is a drawing showing a connection between the X-electrode drive circuit  14  and the AC/DC power supply circuit  18  in the related-art configuration. In  FIG. 4 , the same elements as those of  FIGS. 1 through 3  are referred to by the same numerals, and a description thereof will be omitted. 
         [0021]    The AC/DC power supply circuit  18  is implemented on an AC/DC-power-supply circuit board  31 . The X-electrode drive circuit  14  is implemented on an X-electrode-drive circuit board  32 . The AC/DC-power-supply circuit board  31  and the X-electrode-drive circuit board  32  are separate boards, and the AC/DC power supply circuit  18  and the X-electrode drive circuit  14  on the respective boards are connected with each other via the electric cable  18   a.    
         [0022]    In such a configuration, proper handling and storing of the electric cable  18   a  are necessary, and, also, a thick cable is required to supply a high voltage (VS 0 ), which results in a cost increase. Further, since a voltage drop occurs when an electric current runs through the electric cable  18   a , there is a need to provide the energy-supply-purpose condenser Cvs 1  with a large capacity in the X-electrode drive circuit  14 , which results in a need for a large circuit-board area. 
         [0023]      FIG. 5  is a drawing showing the arrangement of circuits of a related-art plasma display apparatus. What is shown in  FIG. 3  is the plasma display panel  11  as viewed from the rear. Various circuits are arranged on the backside (i.e., opposite the display screen side) of the plasma display panel  11 . 
         [0024]    The drive control circuit  16 , the signal processing circuit  17 , and the AC/DC power supply circuit  18  are arranged around the center of the plasma display panel  11 , and the X-electrode drive circuit  14  and the Y-electrode drive circuit  13  are arranged on the opposite sides of the plasma display panel  11  in such a manner as to keep balance. The address-electrode drive circuit  12  is arranged at the bottom of the plasma display panel  11 . The AC/DC power supply circuit  18  positioned at around the center supplies a power supply voltage to the X-electrode drive circuit  14  via the electric cable  18   a . Further, the power supply voltage is supplied from the X-electrode drive circuit  14  to the Y-electrode drive circuit  13  via the electric cable  18   b.    
         [0025]    In the related-art configuration, there is a need to arrange the Y-electrode drive circuit  13 , the X-electrode drive circuit  14 , and the AC/DC power supply circuit  18  in such a manner as to keep proper balance between the left-hand side and the right-hand side as shown in  FIG. 5  because these circuits are large and heavy. To this end, the required arrangement is such that the AC/DC power supply circuit  18  is positioned at the center, and supplies the power supply voltage via electric cables to the Y-electrode drive circuit  13  and the X-electrode drive circuit  14  positioned on the opposite sides, respectively. This arrangement, however, leads to a cost increase since a thick electric cable is necessary for the purpose of supplying a high voltage as previously described, and also requires a large circuit-board area since a voltage drop occurring upon the flowing of an electric current through the electric cable  18   a  necessitates the provision of the energy-supply-purpose condenser Cvs 1  with a large capacity in the X-electrode drive circuit  14 . 
         [0026]    Moreover, there has been a trend in recent years for plasma display panels to have an increased panel size in response to the demand for large-size screen display, which results in a further increase in the length of the electric cable  18   a.    
         [0027]    [Patent Document 1] Japanese Patent Application Publication No. 2003-302932 
         [0028]    Accordingly, there is a need for a plasma display apparatus for which the cost of an electric cable required to supply a power is reduced, and for which the problem of a voltage drop occurring upon the flowing of an electric current through the electric cable is obviated. 
       SUMMARY OF THE INVENTION 
       [0029]    It is a general object of the present invention to provide a plasma display apparatus that substantially obviates one or more problems caused by the limitations and disadvantages of the related art. 
         [0030]    Features and advantages of the present invention will be presented in the description which follows, and in part will become apparent from the description and the accompanying drawings, or may be learned by practice of the invention according to the teachings provided in the description. Objects as well as other features and advantages of the present invention will be realized and attained by a plasma display apparatus particularly pointed out in the specification in such full, clear, concise, and exact terms as to enable a person having ordinary skill in the art to practice the invention. 
         [0031]    To achieve these and other advantages in accordance with the purpose of the invention, the invention provides a plasma display apparatus, which includes a display panel in which display cells are constituted at least by a set of electrodes including first electrodes extending in a first direction, second electrodes extending in the first direction, and third electrodes extending in a second direction substantially perpendicular to the first direction, a first drive circuit configured to drive the first electrodes, a second drive circuit configured to drive the second electrodes, a third drive circuit configured to drive the third electrodes in conjunction with successive scanning of the first electrodes, and a power-supply circuit configured to generate a DC voltage based on an AC voltage and to supply the DC voltage to the first drive circuit and the second drive circuit, wherein the power-supply circuit and a given drive circuit that is one of the first drive circuit and the second drive circuit are implemented on a single print circuit board. 
         [0032]    According to another aspect of the present invention, a plasma display apparatus includes a display panel in which display cells are constituted at least by a set of electrodes including first electrodes extending in a first direction, second electrodes extending in the first direction, and third electrodes extending in a second direction substantially perpendicular to the first direction, a first drive circuit configured to drive the first electrodes, a second drive circuit configured to drive the second electrodes, a third drive circuit configured to drive the third electrodes in conjunction with successive scanning of the first electrodes, and a power-supply circuit configured to generate a DC voltage based on an AC voltage and to supply the DC voltage to the first drive circuit and the second drive circuit, a first print circuit board on which the power-supply circuit is implemented, and a second print circuit board on which a given drive circuit that is one of the first drive circuit and the second drive circuit is implemented, wherein the first print circuit board and the second print circuit board are placed side by side and connected via a circuit-board connector. 
         [0033]    According to at least one embodiment of the present invention, the voltage generated by the power-supply circuit is supplied to the given drive circuit via printed wiring on the circuit board or via a circuit-board connector. The length of the printed wiring or the circuit-board connector is substantially shorter than the length of a related-art electric cable, so that a voltage drop caused by the flowing of an electric current can be ignored. Accordingly, the cost of an electric cable required to supply a power is reduced, and the problem of a voltage drop occurring upon the flowing of an electric current through this electric cable is obviated. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: 
           [0035]      FIG. 1  is a block diagram showing a main part of a related-art plasma display apparatus; 
           [0036]      FIG. 2  is a drawing showing an example of the configuration of a related-art AC/DC power supply circuit; 
           [0037]      FIG. 3  is a drawing showing an example of the circuit configuration of a related-art X-electrode drive circuit; 
           [0038]      FIG. 4  is a drawing showing a connection between the X-electrode drive circuit and the AC/DC power supply circuit in the related-art configuration; 
           [0039]      FIG. 5  is a drawing showing the arrangement of circuits of a related-art plasma display apparatus; 
           [0040]      FIG. 6  is a block diagram showing a main portion of a first embodiment of a plasma display apparatus according to the present invention; 
           [0041]      FIG. 7  is a drawing showing an X-electrode drive circuit and an AC/DC power supply circuit implemented on the same circuit board; 
           [0042]      FIG. 8  is a drawing showing a variation of the first embodiment of the plasma display apparatus according to the present invention; 
           [0043]      FIG. 9  is a block diagram showing a main portion of a second embodiment of the plasma display apparatus according to the present invention; 
           [0044]      FIG. 10  is a drawing showing a Y-electrode drive circuit and an AC/DC power supply circuit implemented on the same circuit board; and 
           [0045]      FIG. 11  is a drawing showing a variation of the second embodiment of the plasma display apparatus according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0046]    In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
         [0047]      FIG. 6  is a block diagram showing a main portion of a first embodiment of a plasma display apparatus according to the present invention. A plasma display apparatus shown in  FIG. 6  includes a plasma display panel  11 , an address-electrode drive circuit  12 , a Y-electrode drive circuit  13 , an X-electrode drive circuit  34 , a scan circuit  15 , a drive control circuit  16 , a signal processing circuit  17 , and an AC/DC power supply circuit  18 . In  FIG. 6 , the same elements as those of  FIG. 1  are referred to by the same numerals, and a description thereof will be omitted. 
         [0048]    In the plasma display apparatus shown in  FIG. 6 , the X-electrode drive circuit  34  is provided in place of the X-electrode drive circuit  14 , and the X-electrode drive circuit  34  and the AC/DC power supply circuit  18  are implemented on the same circuit board (print circuit board)  35 . The provision of the X-electrode drive circuit  34  and the AC/DC power supply circuit  18  on the same circuit board  35  eliminates the need for an electric cable that connects between these two circuits. 
         [0049]    The configuration and operation of the plasma display panel  11 , the address-electrode drive circuit  12 , the Y-electrode drive circuit  13 , the scan circuit  15 , the drive control circuit  16 , and the signal processing circuit  17  shown in  FIG. 6  are the same as the configuration and operation described in connection with  FIG. 1 . 
         [0050]      FIG. 7  is a drawing showing the X-electrode drive circuit  34  and the AC/DC power supply circuit  18  implemented on the circuit board  35 . In  FIG. 7 , the same elements as those of  FIG. 4  are referred to by the same numerals, and a description thereof will be omitted. 
         [0051]    Since the AC/DC power supply circuit  18  and the X-electrode drive circuit  34  are implemented on the same circuit board  35 , the voltage VS 0  generated by the AC/DC power supply circuit  18  is supplied to the X-electrode drive circuit  34  via printed wiring  41  on the circuit board  35 . The length of the printed wiring  41  is substantially shorter than the length of the related-art electric cable  18   a , so that the voltage drop of the voltage VS 0  caused by an electric current running through the printed wiring  41  can be ignored. 
         [0052]    The X-electrode drive circuit  34  has the same circuit configuration as the X-electrode drive circuit  14 , except that the energy-supply-purpose condenser Cvs 1  is removed. Since the voltage drop along the printed wiring  41  can almost completely be ignored in this case, the condenser Cvs 0  provided in the AC/DC power supply circuit  18  can be utilized as an energy-supply-purpose condenser, so that there is no need to provide another energy-supply-purpose condenser in the X-electrode drive circuit  34 . 
         [0053]    The circuit configuration and operation of the AC/DC power supply circuit  18  are the same as the circuit configuration and operation described in connection with  FIG. 2 . The circuit configuration and operation of the X-electrode drive circuit  34  are the same as the circuit configuration and operation described in connection with  FIG. 3 , except that the condenser Cvs 0  is used as an energy-supply-purpose condenser. 
         [0054]    Further, the transformer  23  transmits an electric power from the primary side to the secondary side via changes in magnetic flux (magnetic coupling), so that the input side and output side of the transformer  23  are not electrically connected with each other (i.e., not directly connected through an electrical conductor). Also, the optical coupling unit  27  comprised of the light-emission device  25  and the light-detection device  26  transmits information from the input side to the output side via changes in light intensity (optical coupling), so that the input side and output side are not electrically connected with each other (i.e., not directly connected through an electrical conductor). In this manner, the primary side (hot side) and the secondary side (cold side) are electrically insulated from each other. 
         [0055]      FIG. 8  is a drawing showing a variation of the first embodiment of the plasma display apparatus according to the present invention. In  FIG. 8 , the same elements as those of  FIG. 7  are referred to by the same numerals, and a description thereof will be omitted. 
         [0056]    In the configuration shown in  FIG. 6  and  FIG. 7 , the AC/DC power supply circuit  18  and the X-electrode drive circuit  34  are implemented on the same circuit board  35 , whereas in the variation shown in  FIG. 8 , an AC/DC power supply circuit  18 A and an X-electrode drive circuit  34 A are implemented separately on an AC/DC-power-supply circuit board  36  and an X-electrode-drive circuit board  37 , respectively. 
         [0057]    The AC/DC-power-supply circuit board  36  and the X-electrode-drive circuit board  37  are placed side by side, and are connected with each other through a circuit-board connector  42  and a circuit-board connector  43 . The voltage VS 0  generated by the AC/DC power supply circuit  18 A is supplied to the X-electrode drive circuit  34 A via the circuit-board connector  42 . The length of the circuit-board connector  42  is substantially shorter than the length of the related-art electric cable  18   a , so that the voltage drop of the voltage VS 0  caused by an electric current running through the circuit-board connector  42  can be ignored. 
         [0058]    The X-electrode drive circuit  34 A has the same circuit configuration as the X-electrode drive circuit  14 , except that the energy-supply-purpose condenser Cvs 1  is removed and that resistors R 3  and R 4  are additionally provided. Since the voltage drop along the circuit-board connector  42  can almost completely be ignored in this case, the condenser Cvs 0  provided in the AC/DC power supply circuit  18 A can be utilized as an energy-supply-purpose condenser, so that there is no need to provide another energy-supply-purpose condenser in the X-electrode drive circuit  34 A. 
         [0059]    The AC/DC power supply circuit  18 A has the same circuit configuration as the AC/DC power supply circuit  18 , except that a switching circuit  44  is provided. The function and operation of the switching circuit  44  will later be described. 
         [0060]    The basic circuit configuration and operation of the AC/DC power supply circuit  18 A are the same as the circuit configuration and operation described in connection with  FIG. 2 , except that the switching circuit  44  is provided. The basic circuit configuration and operation of the X-electrode drive circuit  34 A are the same as the circuit configuration and operation described in connection with  FIG. 3 , except that the condenser Cvs 0  is used as an energy-supply-purpose condenser. 
         [0061]    In the configuration shown in  FIG. 7 , the AC/DC power supply circuit  18  and the X-electrode drive circuit  34  are implemented on the same circuit board  35 , whereas in the configuration shown in  FIG. 8 , the AC/DC power supply circuit  18 A and the X-electrode drive circuit  34 A are implemented separately on the AC/DC-power-supply circuit board  36  and the X-electrode-drive circuit board  37 , respectively. With the provision of the AC/DC power supply circuit  18 A and the X-electrode drive circuit  34 A on the respective separate circuit boards, there is a merit in that no modification is necessary to the AC/DC-power-supply circuit board  36  carrying the AC/DC power supply circuit  18 A even when modification is made to the X-electrode drive circuit  34 A. 
         [0062]    Various standards are defined for industrial products. The UL standard, for example, is provided by the UL that is a safety testing organization in the United States that performs an inspection and test relating to the safety of commercial products for the benefit of the public. The UL sets a standard relating to the danger of fire and electric shock caused by products, performs inspections and tests for individual products, and allows a UL mark to be attached to the products that passed its inspections and tests. In order to obtain a UL-standard approval for the AC/DC power supply circuit  18  that is implemented on the circuit board  35 , there is a need to submit the entirety of the circuit board  35  for inspection and to request inspections and tests to be conducted. If modification is made to the X-electrode drive circuit  34  on the circuit board  35  after the approval is obtained, such modification is considered as a modification to the circuit board  35 , so that a further inspection will need to be conducted for the entirety of the circuit board  35 . 
         [0063]    With the configuration shown in  FIG. 8 , on the other hand, the AC/DC power supply circuit  18 A and the X-electrode drive circuit  34 A are provided separately on the AC/DC-power-supply circuit board  36  and the X-electrode-drive circuit board  37 , respectively, so that no modification is necessary to the AC/DC-power-supply circuit board  36  carrying the AC/DC power supply circuit  18 A even when modification is made to the X-electrode drive circuit  34 A. Accordingly, once an approval is obtained for the AC/DC-power-supply circuit board  36 , there is no need to request an approval again, no matter what modification is thereafter made to the X-electrode drive circuit. 
         [0064]    Moreover, the configuration shown in  FIG. 8  is provided with the resistors R 3  and R 4 , which serve as a voltage detection circuit in the X-electrode drive circuit  34 A. The voltage VS 0  that appears between the opposite ends of the smoothing condenser Cvs 0  is divided by the resistors R 3  and R 4 . The divided voltage is supplied to the optical coupling unit  27  via the circuit-board connector  43  and the switching circuit  44 . In the optical coupling unit  27 , the light-emission device  25  emits light with the intensity responsive to the divided voltage level. The light-detection device  26  receives light from the light-emission device  25 , and supplies a signal responsive to the intensity of the received light to the pulse generating circuit  22 . The pulse generating circuit  22  controls the generation of the pulses in response to the signal from the light-detection device  26 . This feedback control serves to adjust the voltage between the opposite ends of the smoothing condenser Cvs 0  to a predetermined voltage (i.e., to the sustain discharge voltage VS 0 ). 
         [0065]    Since the voltage VS 0  to be controlled is used in the X-electrode drive circuit  34 A, it is preferable to perform the feedback control based on the voltage level that is detected on the X-electrode-drive circuit board  37  where the X-electrode drive circuit  34 A is implemented (i.e., where the controlled voltage is actually used). Through such feedback control, it becomes possible to set the voltage VS 0  more accurately. The resistors R 3  and R 4  described above are provided to detect the voltage level of the voltage VS 0  (or, more accurately, the divided voltage level) on the X-electrode-drive circuit board  37 . 
         [0066]    The switching circuit  44  selects an input from the X-electrode-drive circuit board  37  during the normal operation in which the plasma display apparatus is used by a user, and the selected input is supplied to the optical coupling unit  27 . The setting of the switching circuit  44  may be changed in response to a control signal applied to the switching circuit  44  according to need, so that the voltage level divided by the resistors R 1  and R 2  is selected for provision to the optical coupling unit  27 . The resistors R 1  and R 2  are not necessary for the purpose of the normal operation in which the plasma display apparatus is used by a user. Unless the resistors R 1  and R 2  are provided, however, an operation test cannot be conducted with the AC/DC-power-supply circuit board  36  alone. 
         [0067]    In the AC/DC power supply circuit  18 A of  FIG. 8 , the resistors R 1  and R 2  are provided on the AC/DC-power-supply circuit board  36 , and provision is made such that the switching circuit  44  allows feedback control to be performed based on the voltage detected by the resistors R 1  and R 2 . With this provision, it is possible to perform an operation test for the AC/DC power supply circuit  18 A even if the AC/DC-power-supply circuit board  36  is provided alone without a connection to the X-electrode-drive circuit board  37 . 
         [0068]      FIG. 9  is a block diagram showing a main portion of a second embodiment of the plasma display apparatus according to the present invention. A plasma display apparatus shown in  FIG. 9  includes a plasma display panel  11 , an address-electrode drive circuit  12 , a Y-electrode drive circuit  33 , an X-electrode drive circuit  14 , a scan circuit  15 , a drive control circuit  16 , a signal processing circuit  17 , and an AC/DC power supply circuit  18 . In  FIG. 9 , the same elements as those of  FIG. 1  are referred to by the same numerals, and a description thereof will be omitted. 
         [0069]    In the plasma display apparatus shown in  FIG. 9 , a Y-electrode drive circuit  33  is provided in place of the Y-electrode drive circuit  13 , and the Y-electrode drive circuit  33  and the AC/DC power supply circuit  18  are implemented on the same circuit board (print circuit board)  38 . The provision of the Y-electrode drive circuit  33  and the AC/DC power supply circuit  18  on the same circuit board  38  eliminates the need to handle and store an electric cable that supplies the sustain discharge voltage VS 0  to the Y-electrode drive circuit  33 . 
         [0070]    In the configuration shown in  FIG. 1 , the voltage VS 0  is supplied from the AC/DC power supply circuit  18  to the X-electrode drive circuit  14  via the electric cable  18   a , and is further supplied from the X-electrode drive circuit  14  to the Y-electrode drive circuit  13  via the electric cable  18   b . In the configuration shown in  FIG. 9 , the voltage VS 0  is first supplied from the AC/DC power supply circuit  18  to the Y-electrode drive circuit  33 , and is then supplied from the Y-electrode drive circuit  33  to the X-electrode drive circuit  14  via the electric cable  18   b.    
         [0071]    The configuration and operation of the plasma display panel  11 , the address-electrode drive circuit  12 , the X-electrode drive circuit  14 , the scan circuit  15 , the drive control circuit  16 , and the signal processing circuit  17  shown in  FIG. 9  are the same as the configuration and operation described in connection with  FIG. 1 . 
         [0072]      FIG. 10  is a drawing showing the Y-electrode drive circuit  33  and the AC/DC power supply circuit  18  implemented on the circuit board  38 . In  FIG. 10 , the same elements as those of  FIG. 4  are referred to by the same numerals, and a description thereof will be omitted. 
         [0073]    Since the AC/DC power supply circuit  18  and the Y-electrode drive circuit  33  are implemented on the same circuit board  38 , the voltage VS 0  generated by the AC/DC power supply circuit  18  is supplied to the Y-electrode drive circuit  33  via printed wiring on the circuit board  38 . The length of the printed wiring is short, so that the voltage drop of the voltage VS 0  caused by an electric current running through the printed wiring can be ignored. 
         [0074]    In the related-art configuration shown in  FIG. 1 , the Y-electrode drive circuit  13  and the X-electrode drive circuit  14  have the same circuit configuration for their sustain circuit portions for performing sustain discharge. Namely, the circuit configuration shown in  FIG. 3  that shows a portion corresponding to the sustain circuit for generating sustain discharge that is included in the X-electrode drive circuit  14  is identical to the configuration of the sustain circuit of the Y-electrode drive circuit  13 . 
         [0075]    The Y-electrode drive circuit  33  shown in  FIG. 10  according to the present invention has the same circuit configuration as the related-art Y-electrode drive circuit  13 , except that the energy-supply-purpose condenser Cvs 1  is removed. Since the voltage drop along the printed wiring can almost completely be ignored in this case, the condenser Cvs 0  provided in the AC/DC power supply circuit  18  can be utilized as an energy-supply-purpose condenser, so that there is no need to provide another energy-supply-purpose condenser in the Y-electrode drive circuit  33 . 
         [0076]    The circuit configuration and operation of the AC/DC power supply circuit  18  are the same as the circuit configuration and operation described in connection with  FIG. 2 . The circuit configuration and operation of the Y-electrode drive circuit  33  relating to the sustain discharge are the same as the circuit configuration and operation described in connection with  FIG. 3 , except that the condenser Cvs 0  is used as an energy-supply-purpose condenser. 
         [0077]    Further, the transformer  23  transmits an electric power from the primary side to the secondary side via changes in magnetic flux, so that the input side and output side of the transformer  23  are not electrically connected with each other (i.e., not directly connected through an electrical conductor). Also, the optical coupling unit  27  comprised of the light-emission device  25  and the light-detection device  26  transmits information from the input side to the output side via changes in light intensity, so that the input side and output side are not electrically connected with each other (i.e., not directly connected through an electrical conductor). In this manner, the primary side (hot side) and the secondary side (cold side) are electrically insulated from each other. 
         [0078]      FIG. 11  is a drawing showing a variation of the second embodiment of the plasma display apparatus according to the present invention. In  FIG. 11 , the same elements as those of  FIG. 10  are referred to by the same numerals, and a description thereof will be omitted. 
         [0079]    In the configuration shown in  FIG. 9  and  FIG. 10 , the Y-electrode drive circuit  33  and the AC/DC power supply circuit  18  are implemented on the same circuit board  38 , whereas in the variation shown in  FIG. 11 , an AC/DC power supply circuit  18 A and a Y-electrode drive circuit  33 A are implemented separately on an AC/DC-power-supply circuit board  36  and a Y-electrode-drive circuit board  39 , respectively. 
         [0080]    The AC/DC-power-supply circuit board  36  and the Y-electrode-drive circuit board  39  are placed side by side, and are connected with each other through a circuit-board connector  46  and a circuit-board connector  47 . The voltage VS 0  generated by the AC/DC power supply circuit  18 A is supplied to the Y-electrode drive circuit  33 A via the circuit-board connector  46 . The length of the circuit-board connector  46  is short, so that the voltage drop of the voltage VS 0  caused by an electric current running through the circuit-board connector  46  can be ignored. 
         [0081]    The Y-electrode drive circuit  33 A has the same circuit configuration as the Y-electrode drive circuit  13 , except that the energy-supply-purpose condenser Cvs 1  is removed and that resistors R 3  and R 4  are additionally provided. Since the voltage drop along the circuit-board connector  46  can almost completely be ignored in this case, the condenser Cvs 0  provided in the AC/DC power supply circuit  18 A can be utilized as an energy-supply-purpose condenser, so that there is no need to provide another energy-supply-purpose condenser in the Y-electrode drive circuit  33 A. 
         [0082]    The AC/DC power supply circuit  18 A is the same circuit as the AC/DC power supply circuit  18 A described in connection with  FIG. 8 , and has the same circuit configuration as the related-art AC/DC power supply circuit  18 , except that the switching circuit  44  is provided. The basic circuit configuration and operation of the sustain circuit of the Y-electrode drive circuit  33 A are the same as the circuit configuration and operation described in connection with  FIG. 3 , except that the condenser Cvs 0  is used as an energy-supply-purpose condenser. 
         [0083]    In the configuration shown in  FIG. 10 , the AC/DC power supply circuit  18  and the Y-electrode drive circuit  33  are implemented on the same circuit board  38 , whereas in the configuration shown in  FIG. 11 , the AC/DC power supply circuit  18 A and the Y-electrode drive circuit  33 A are implemented separately on the AC/DC-power-supply circuit board  36  and the Y-electrode-drive circuit board  39 , respectively. Accordingly, the same merits as those described in connection with  FIG. 8  are provided with respect to circuit modification and standard approvals. 
         [0084]    Further, in the configuration shown in  FIG. 11 , the resistors R 3  and R 4  are provided to detect the voltage level of the voltage VS 0  (or, more accurately, the divided voltage level) on the Y-electrode-drive circuit board  39 . The switching circuit  44  selects a voltage from the Y-electrode-drive circuit board  39  during the normal operation in which the plasma display apparatus is used by a user, and the selected voltage is supplied to the optical coupling unit  27 . On the other hand, the switching circuit  44  selects a voltage level from the resistors R 1  and R 2  in the situation in which the AC/DC-power-supply circuit board  36  is provided alone without a connection to the Y-electrode-drive circuit board  39 , thereby making it possible to perform an operation test on the AC/DC power supply circuit  18 A alone. These advantages are the same as the merits described with respect to the configuration shown in  FIG. 8 . 
         [0085]    Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. 
         [0086]    The present application is based on Japanese priority application No. 2006-187100 filed on Jul. 6, 2006, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.

Technology Classification (CPC): 6