Abstract:
A 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 first inductor and a first diode electrically connected in series between the first side of the panel capacitor and a first node, a second inductor and a second diode electrically connected in series between the second side of the panel capacitor and the first node, a third switch electrically connected between the first side of the panel capacitor and the first node, a fourth switch electrically connected between the second side of the panel capacitor and the first node, and a fifth switch electrically connected between the first node and a second voltage.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of the filing date of U.S. provisional patent application No. 60/595,301, filed Jun. 22, 2005, the contents of which are hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a driving circuit, and more specifically, to a driving circuit for a plasma display panel (PDP). 
   2. Description of the Prior Art 
   In a plasma display panel (PDP), charges are accumulated on the electrodes of cells according to display data, and a sustaining discharge pulse is applied to paired electrodes of the cells in order to generate visible light. 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. There are many sustaining pulses to apply to electrodes. Hence the power consumption of a PDP display is considerable. When energy can be recovered from the panel, the power consumption of the panel will be reduced. Many designs and patents have been developed for providing methods and apparatuses for energy recovery in PDPs. 
   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. 
   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. 
   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 
   It is therefore an objective of the invention to provide a plasma display panel driving circuit that solves the problems of the prior art. 
   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 first inductor and a first diode electrically connected in series between the first side of the panel capacitor and a first node, a second inductor and a second diode electrically connected in series between the second side of the panel capacitor and the first node, a third switch electrically connected between the first side of the panel capacitor and the first node, a fourth switch electrically connected between the second side of the panel capacitor and the first node, and a fifth switch electrically connected between the first node and a second voltage. 
   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 
       FIG. 1  is a circuit diagram of a plasma display panel driving circuit according to the prior art. 
       FIG. 2  shows voltage levels in the circuit of  FIG. 1 . 
       FIG. 3  is a circuit diagram of a plasma display panel driving circuit according to a first embodiment of the present invention. 
       FIG. 4  is a flowchart illustrating the operation of the driving circuit of the first embodiment for creating a sustain waveform. 
       FIG. 5  is a circuit diagram of a plasma display panel driving circuit according to a second embodiment of the present invention. 
       FIG. 6  is a flowchart illustrating the operation of the driving circuit of the second embodiment for creating a sustain waveform. 
   

   DETAILED DESCRIPTION 
   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 two inductors L 31  and L 32 , coupled to an equivalent panel capacitor Cp 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 2 . The voltage V 1  is a positive voltage, whereas the voltage V 2  can be ground or a negative voltage. 
   The switch S 31  is electrically connected between the voltage source V 1  and node N 3 . Switches S 32  and S 33  are unidirectional switches, as indicated by the arrows shown in  FIG. 3 . Switch S 32  is electrically connected between the node N 3  and an X side of the panel capacitor Cp, wherein current flows in the direction toward the X side of the panel capacitor Cp. Switch S 33  is electrically connected between the node N 3  and a Y side of the panel capacitor Cp, wherein current flows in the direction toward the Y side of the panel capacitor Cp. Diode D 31  and inductor L 31  are electrically connected in series between the X side of the panel capacitor Cp and the node N 3 , where an anode of diode D 31  is electrically connected to the X side of the panel capacitor Cp and the inductor L 31  is electrically connected between a cathode of the diode D 31  and the node N 3 . Likewise, diode D 32  and inductor L 32  are electrically connected in series between the Y side of the panel capacitor Cp and the node N 3 , where an anode of diode D 32  is electrically connected to the Y side of the panel capacitor Cp and the inductor L 32  is electrically connected between a cathode of the diode D 32  and the node N 3 . Switch S 34  is electrically connected between the X side of the panel capacitor Cp and voltage source V 2 , whereas switch S 35  is electrically connected between the Y side of the panel capacitor Cp and V 2 . 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. One advantage of the driving circuit  300  is that the rising and falling slopes of the sustain waveform can be different from each other and can be adjusted by adjusting the inductance of the inductors L 31  and L 32 . Moreover, the five switches S 31  to S 35  is one fewer than the six switches S 1  to S 6  of the prior art driving circuit  100 . 
   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. 
   Step  400 : Start. 
   Step  410 : Keep the voltage potential at the X side of the panel capacitor Cp at V 2  by turning on the switch S 34 . Keep the voltage potential at the Y side of the panel capacitor Cp at V 1  by turning on the switches S 31  and S 33 , where the current path is through S 31  and S 33 . 
   Step  420 : Discharge the panel capacitor Cp from the Y side to the X side by turning on the switch S 32 . The voltage potential at the X side of the panel capacitor Cp goes up to V 1  and the voltage potential at the Y side of the panel capacitor Cp goes down to V 2  accordingly, and the current path is through D 32 , L 32 , and S 32 . 
   Step  430 : Keep the voltage potential at the X side of the panel capacitor Cp at V 1  by turning on the switches S 31  and S 32 , where the current path is through S 31  and S 32 . Keep the voltage potential at the Y side of the panel capacitor Cp at V 2  by turning on the switch S 35 . 
   Step  440 : Discharge the panel capacitor Cp from the X side to the Y side by turning on the switch S 33 . The voltage potential at the X side of the panel capacitor Cp goes down to V 2  and the voltage potential at the Y side of the panel capacitor Cp goes up to V 1  accordingly, and the current path is through D 31 , L 31 , and S 33 . 
   Step  450 : Keep the voltage potential at X side of the panel capacitor Cp at V 2  by turning on the switch S 34 . Keep the voltage potential at Y side of the panel capacitor Cp at V 1  by turning on the switches S 31  and S 33 , where the current path is through S 31  and S 33 . 
   Step  460 : End. 
   Please refer to  FIG. 5 .  FIG. 5  is a circuit diagram of a plasma display panel driving circuit  500  according to a first embodiment of the present invention. The driving circuit  500  comprises five switches S 51 , S 52 , S 53 , S 54 , and S 55 , two diodes D 51  and D 52 , and two inductors L 51  and L 52 , coupled to an equivalent panel capacitor Cp of a plasma display panel. The driving circuit  500  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 2 . The voltage V 1  is a positive voltage, whereas the voltage V 2  can be ground or a negative voltage. 
   Switch S 51  is electrically connected between an X side of the panel capacitor Cp and the voltage source V 1 , whereas switch S 52  is electrically connected between a Y side of the panel capacitor Cp and the voltage source V 1 . Diode D 51  and inductor L 51  are electrically connected in series between the X side of the panel capacitor Cp and node N 5 , where a cathode of diode D 51  is electrically connected to the X side of the panel capacitor Cp and the inductor L 51  is electrically connected between an anode of the diode D 51  and the node N 5 . Likewise, diode D 52  and inductor L 52  are electrically connected in series between the Y side of the panel capacitor Cp and the node N 5 , where a cathode of diode D 52  is electrically connected to the Y side of the panel capacitor Cp and the inductor L 52  is electrically connected between an anode of the diode D 52  and the node N 5 . Switches S 53  and S 54  are unidirectional switches, as indicated by the arrows shown in  FIG. 5 . Switch S 53  is electrically connected between the node N 5  and the X side of the panel capacitor Cp, wherein current flows in the direction away from the X side of the panel capacitor Cp. Switch S 54  is electrically connected between the node N 5  and the Y side of the panel capacitor Cp, wherein current flows in the direction away from the Y side of the panel capacitor Cp. The switch S 55  is electrically connected between the node N 5  and V 2 . As with the driving circuit  300 , a property of the driving circuit  500  is that the rising and falling slopes of the sustain waveform can be different from each other and can be adjusted by adjusting the inductance of the inductors L 51  and L 52 . Moreover, the five switches S 51  to S 55  is one fewer than the six switches S 1  to S 6  of the prior art driving circuit  100 . 
   Please refer to  FIG. 6 , which illustrates the operation of the driving circuit  500  of the first embodiment for creating a sustain waveform. Steps contained in the flowchart will be explained as follows. 
   Step  600 : Start. 
   Step  610 : Keep the voltage potential at the X side of the panel capacitor Cp at V 2  by turning on the switches S 53  and S 55 , where the current path is through S 53  and S 55 . Keep the voltage potential at the Y side of the panel capacitor Cp at V 1  by turning on the switch S 52 . 
   Step  620 : Discharge the panel capacitor Cp from the Y side to the X side by turning on the switch S 54 . The voltage potential at the X side of the panel capacitor Cp goes up to V 1  and the voltage potential at the Y side of the panel capacitor Cp goes down to V 2  accordingly, and the current path is through S 54 , L 51 , and D 51 . 
   Step  630 : Keep the voltage potential at the X side of the panel capacitor Cp at V 1  by turning on the switch S 51 . Keep the voltage potential at the Y side of the panel capacitor Cp at V 2  by turning on the switches S 54  and S 55 , where the current path is through S 54  and S 55 . 
   Step  640 : Discharge the panel capacitor Cp from the X side to the Y side by turning on the switch S 53 . The voltage potential at the X side of the panel capacitor Cp goes down to V 2  and the voltage potential at the Y side of the panel capacitor Cp goes up to V 1  accordingly, and the current path is through S 53 , L 52 , and D 52 . 
   Step  650 : Keep the voltage potential at the X side of the panel capacitor Cp at V 2  by turning on the switches S 53  and S 55 , where the current path is through S 53 , D 51 , and S 55 . Keep the voltage potential at the Y side of the panel capacitor Cp at V 1  by turning on the switch S 52 . 
   Step  660 : End. 
   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. In addition, the rising and falling slopes of the sustain waveform can be different from each other and can be adjusted by adjusting the inductance of the two inductors. 
   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.