Abstract:
A driving circuit for creating sustain waveforms of plasma display panel (PDP) is provided. The driving circuit includes the functions of voltage clamping and energy recovery. The main structure of this driving circuit is composed of 5 switches, two diodes, and an inductor which couple to the panel capacitor of the PDP. The use of more voltage potentials can also be implemented very easily if they are required.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of the filing date of U.S. Provisional Pat. Application No. 60/595,300, filed Jun. 22, 2005, the contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a driving circuit, and more specifically, to a driving circuit for a plasma display panel (PDP).  
         [0004]     2. Description of the Prior Art  
         [0005]     In a plasma display panel (PDP), charges are accumulated in cells according to display data, and a sustaining discharge pulse is applied to paired electrodes of the cells in order to initiate discharge glow to effect display. As far as the PDP display is concerned, a high voltage is required to be applied to the electrodes, and a pulse-duration of several microseconds is usually required. Hence the power consumption of a PDP display is considerable. Energy recovering (power saving) is therefore important. Many designs and patents have been developed for providing methods and apparatuses for energy recovery in PDPs.  
         [0006]     Please refer to  FIG. 1  which illustrates a circuit diagram of a PDP driving circuit  100  according to the prior art. The PDP driving circuit  100  comprises an equivalent panel capacitor Cp having an X side and a Y side, four switches S 1  to S 4  for permitting current to pass as part of a voltage clamp circuit, and a charging/discharging circuit that includes two switches S 5  and S 6  with body diodes, two diodes D 1  and D 2 , and an inductor L 1 . The PDP driving circuit  100  requires the two switches S 5  and S 6  in order to allow two-direction discharge, which is required for energy recovery. That is, the two switches S 5  and S 6  achieve two paths that allow ineffective power from the X side of the panel capacitor Cp to be recovered to the Y side and vice versa.  
         [0007]     In operation, the switches S 1  to S 6  are controlled to provide panel capacitor Cp voltages as shown in  FIG. 2 . In plot  204 , the individual voltages of the X side (dashed line) and Y side (solid line) of the panel capacitor Cp are shown to vary between 0 and Vs. Plot  202  shows the voltage across the panel capacitor Cp, which is the voltage of the Y side minus the voltage of the X side. The voltage across the panel capacitor Cp varies between Vs and −Vs.  
         [0008]     The prior art requires six switches S 1  to S 6 , thereby increasing the space required on a semiconductor integrated circuit.  
       SUMMARY OF THE INVENTION  
       [0009]     It is therefore an objective of the invention to provide a plasma display panel driving circuit that solves the problems of the prior art.  
         [0010]     Briefly summarized, the claimed plasma display panel driving circuit includes a panel capacitor having a first side and a second side, a first switch electrically connected between the first side of the panel capacitor and a first voltage, a second switch electrically connected between the second side of the panel capacitor and the first voltage, a third switch having a first end coupled to the first side of the panel capacitor and a second end, a fourth switch having a first end coupled to the second side of the panel capacitor and a second end, an inductor electrically connected between a second end of the third switch and a second end of the fourth switch, a first diode having a first end coupled to the second end of the third switch and a second end, a second diode having a first end coupled to the second end of the fourth switch and a second end coupled to a second end of the first diode, and a fifth switch electrically connected between a second voltage and the second end of the first diode.  
         [0011]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a circuit diagram of a plasma display panel driving circuit according to the prior art.  
         [0013]      FIG. 2  shows voltage levels in the circuit of  FIG. 1 .  
         [0014]      FIG. 3  is a circuit diagram of a plasma display panel driving circuit according to a first embodiment of the present invention.  
         [0015]      FIG. 4  is a flowchart illustrating the operation of the driving circuit of the first embodiment for creating a sustain waveform.  
         [0016]      FIG. 5  is a circuit diagram of a plasma display panel driving circuit according to a second embodiment of the present invention.  
         [0017]      FIG. 6  is a circuit diagram of a plasma display panel driving circuit according to a third embodiment of the present invention.  
         [0018]      FIG. 7  is a flowchart illustrating the operation of the driving circuit of the third embodiment for creating a sustain waveform.  
         [0019]      FIG. 8  is a circuit diagram of a plasma display panel driving circuit according to a fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]     The present invention provides a new driving circuit for the PDP. Please refer to  FIG. 3 .  FIG. 3  is a circuit diagram of a plasma display panel driving circuit  300  according to a first embodiment of the present invention. The driving circuit  300  comprises five switches S 31 , S 32 , S 33 , S 34 , and S 35 , two diodes D 31  and D 32 , and an inductor L 31 , coupled to an equivalent panel capacitor C p  of a plasma display panel. The driving circuit  300  is electrically connected to a voltage source V 1 , wherein the voltage potential output by voltage source V 1  is greater than the voltage potential output by voltage source V 6 . The voltage V 1  is a voltage, whereas the voltage V 6  can be ground or a negative voltage.  
         [0021]     The switch S 31  is electrically connected at one end to the voltage source V 1  and is electrically connected at the other end to anodes of diodes D 31  and D 32 . The inductor L 31  is electrically connected between cathodes of diodes D 31  and D 32 . The switch S 32  is electrically connected between the cathode of diode D 31  and an X side of the panel capacitor C p , whereas the switch S 33  is electrically connected between the cathode of diode D 32  and a Y side of the panel capacitor C p . The switch S 34  is electrically connected between the X side of the panel capacitor C p  and voltage source V 6 , and the switch S 35  is electrically connected between the Y side of the panel capacitor C p  and voltage source V 6 . The switches S 31  to S 35  can be N-type or P-type metal oxide semiconductor (MOS) transistors, other types of transistors, or other switching devices.  
         [0022]     Please refer to  FIG. 4 , which illustrates the operation of the driving circuit  300  of the first embodiment for creating a sustain waveform. Steps contained in the flowchart will be explained as follows.  
         [0023]     Step  400 : Start.  
         [0024]     Step  410 : Keep the voltage potential at the X side of the panel capacitor C p  at voltage source V 6  by turning on the switch S 34 . Keep the voltage potential at the Y side of the panel capacitor C p  at V 1  by turning on the switches S 31  and S 33 , where the current path is through S 31 , D 32 , and S 33 .  
         [0025]     Step  420 : Discharge the panel capacitor C p  from the Y side to the X side by turning on the switches S 32  and S 33 . The voltage potential at the X side of the panel capacitor C p  goes up to V 1  and the voltage potential at the Y side of the panel capacitor C p  goes down to voltage source V 6  accordingly, and the current path is through S 33 , L 31 , and S 32 .  
         [0026]     Step  430 : Keep the voltage potential at the X side of the panel capacitor C p  at V 1  by turning on the switches S 31  and S 32 , where the current path is through S 31 , D 31 , and S 32 . Keep the voltage potential at the Y side of the panel capacitor C p  at voltage source V 6  by turning on the switch S 35 .  
         [0027]     Step  440 : Discharge the panel capacitor C p  from the X side to the Y side by turning on the switches S 32  and S 33 . The voltage potential at the X side of the panel capacitor C p  goes down to voltage source V 6  and the voltage potential at the Y side of the panel capacitor C p  goes up to V 1  accordingly, and the current path is through S 32 , L 31 , and S 33 .  
         [0028]     Step  450 : Keep the voltage potential at the X side of the panel capacitor C p  at voltage source V 6  by turning on the switch S 34 . Keep the voltage potential at the Y side of the panel capacitor C p  at V 1  by turning on the switches S 31  and S 33 , where the current path is through S 31 , D 32 , and S 33 .  
         [0029]     Step  460 : End.  
         [0030]     Please refer to  FIG. 5 .  FIG. 5  is a circuit diagram of a plasma display panel driving circuit  500  according to a second embodiment of the present invention. The driving circuit  500  is similar to the driving circuit  300  shown in  FIG. 3 , and also comprises the five switches S 31 , S 32 , S 33 , S 34 , and S 35 , two diodes D 31  and D 32 , and the inductor L 31  coupled to the equivalent panel capacitor C p . The driving circuit  500  additionally includes switches S 36  and S 37  and voltage sources V 2  and V 3 . Switch S 36  is electrically connected between voltage source V 2  and the X side of the panel capacitor C p . Switch S 37  is electrically connected between voltage source V 3  and the Y side of the panel capacitor C p . Voltage potentials output from voltage sources V 2  and V 3  are both greater than the voltage potential output from voltage source V 1 . The voltage potential output by voltage source V 1  is greater than the voltage potential output by voltage source V 6 . The voltage V 1  is a voltage, whereas the voltage V 6  can be ground or a negative voltage.  
         [0031]     Please refer to  FIG. 6 .  FIG. 6  is a circuit diagram of a plasma display panel driving circuit  600  according to a third embodiment of the present invention. The driving circuit  600  comprises five switches S 61 , S 62 , S 63 , S 64 , and S 65 , two diodes D 61  and D 62 , and an inductor L 61 , coupled to an equivalent panel capacitor C p  of a plasma display panel. The driving circuit  600  is electrically connected to a voltage source V 1 , wherein the voltage potential output by voltage source V 1  is greater than the voltage potential output by voltage source V 6 . The voltage V 1  is a voltage, whereas the voltage V 6  can be ground or a negative voltage.  
         [0032]     The switch S 61  is electrically connected between an X side of the panel capacitor C p  and the voltage source V 1 , and the switch S 62  is electrically connected between a Y side of the panel capacitor C p  and the voltage source V 1 . The switch S 63  is electrically connected between the X side of the panel capacitor C p  and an anode of diode D 61 , and the switch S 64  is electrically connected between the Y side of the panel capacitor C p  and an anode of diode D 62 . Inductor L 61  is electrically connected between the anode of diode D 61  and the anode of diode D 62 . Switch S 65  is electrically connected between voltage source V 6  and the cathodes of diodes D 61  and D 62 .  
         [0033]     Please refer to  FIG. 7 , which illustrates the operation of the driving circuit  600  of the third embodiment for creating a sustain waveform. Steps contained in the flowchart will be explained as follows.  
         [0034]     Step  700 : Start.  
         [0035]     Step  710 : Keep the voltage potential at the X side of the panel capacitor C p  at voltage source V 6  by turning on the switches S 63  and S 65 , where the current path is through S 63 , D 61 , and S 65 . Keep the voltage potential at the Y side of the panel capacitor C p  at V 1  by turning on the switch S 62 .  
         [0036]     Step  720 : Discharge the panel capacitor C p  from the Y side to the X side by turning on the switches S 63  and S 64 . The voltage potential at the X side of the panel capacitor C p  goes up to V 1  and the voltage potential at the Y side of the panel capacitor C p  goes down to voltage source V 6  accordingly, and the current path is through S 64 , L 61 , and S 63 .  
         [0037]     Step  730 : Keep the voltage potential at the X side of the panel capacitor C p  at V 1  by turning on the switch S 61 . Keep the voltage potential at the Y side of the panel capacitor C p  at voltage source V 6  by turning on the switches S 64  and S 65 , where the current path is through S 64 , D 62 , and S 65 .  
         [0038]     Step  740 : Discharge the panel capacitor C p  from the X side to the Y side by turning on the switches S 63  and S 64 . The voltage potential at the X side of the panel capacitor C p  goes down to voltage source V 6  and the voltage potential at the Y side of the panel capacitor C p  goes up to V 1  accordingly, and the current path is through S 63 , L 61 , and S 64 .  
         [0039]     Step  750 : Keep the voltage potential at the X side of the panel capacitor C p  at voltage source V 6  by turning on the switches S 63  and S 65 , where the current path is through S 63 , D 61 , and S 65 . Keep the voltage potential at the Y side of the panel capacitor C p  at V 1  by turning on the switch S 62 .  
         [0040]     Step  760 : End.  
         [0041]     Please refer to  FIG. 8 .  FIG. 8  is a circuit diagram of a plasma display panel driving circuit  800  according to a fourth embodiment of the present invention. The driving circuit  800  is similar to the driving circuit  600  shown in  FIG. 6 , and also comprises the five switches S 61 , S 62 , S 63 , S 64 , and S 65 , two diodes D 61  and D 62 , and the inductor L 61  coupled to the panel capacitor C p . The driving circuit  800  additionally includes switches S 66  and S 67  and voltage sources V 4  and V 5 . Switch S 66  is electrically connected between voltage source V 4  and the Y side of the panel capacitor C p . Switch S 67  is electrically connected between voltage source V 5  and the X side of the panel capacitor C p . Voltage potentials output from voltage sources V 4  and V 5  are both negative, and are lower than the voltage potential output by voltage source V 6 .  
         [0042]     In summary, the present invention provides embodiments of driving circuits that utilize fewer switches than the prior art driving circuit. Only five switches are required instead of six switches. Therefore, use of the present invention driving circuits reduces the space required on a semiconductor integrated circuit.  
         [0043]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.