Abstract:
A driving circuit for producing sustain waveforms of a plasma display panel (PDP) is mentioned. The driving circuit includes the functions of voltage clamping and energy recovery. By controlling switches contained in the driving circuit, the supplied voltage source can be made to be only half of the sustain voltage. The voltage stress of some components will therefore be lower. In addition, the numbers of components can be reduced in the driving circuit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of the filing date of U.S. provisional patent application No. 60/595,303, 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 recent years, there has been an increasing demand for planar matrix displays such as plasma display panels (PDP), liquid-crystal displays (LCD) and electroluminescent displays (EL display) in place of cathode ray tube terminals (CRT) due to the advantage of the thin appearance of the planar matrix displays.  
         [0006]     In a PDP display, a sustaining discharge pulse activates inert gas to generate ultraviolet so that the ultraviolet further activates fluorescent materials and visible light is emitted to display. As far as the PDP display is concerned, it is required to apply a high voltage to the electrodes. In particular, a pulse-duration of several microseconds is usually adopted. Hence the power consumption of the PDP display is quite considerable. Energy recovering (power saving) is therefore sought for. Many designs and patents have been developed for providing methods and apparatuses of energy recovering for PDPs. One of the examples is U.S. Pat. No. 5,828,353, “Drive Unit for Planar Display” by Kishi, et al., which is included herein by reference.  
         [0007]     Please refer to  FIG. 1 .  FIG. 1  is a block diagram of a prior art driving circuit  100 . The plasma panel display can be taken as a panel equivalent capacitor Cp. The conventional driving circuit  100  includes four switches S 1  to S 4  for passing current, an X-side energy recovery circuit  110  and a Y-side energy recovery circuit  120  for charging/discharging the panel equivalent capacitor Cp from the X side of the panel equivalent capacitor Cp and the Y side of the panel equivalent capacitor Cp respectively. S 5 , S 6 , S 7  and S 8  are switches for passing current. D 5 , D 6 , D 7  and D 8  are diodes. V 1  and V 2  are two voltage sources. C 1  and C 2  are capacitors adopted for recovering energy, and L 1  and L 2  are resonant inductors. The X-side energy recovery circuit  110  includes an energy-forward channel comprising the switch S 6 , the diode D 6  and the inductor L 1 , and an energy-backward channel comprising the inductor L 1 , the diode D 5  and the switch S 5 . Similarly, the Y-side energy recovery circuit  120  also includes an energy-forward channel comprising the switch S 8 , the diode D 8  and the inductor L 2 , and an energy-backward channel comprising the inductor L 2 , the diode D 7  and the switch S 7 .  
         [0008]     Please refer to  FIG. 2 .  FIG. 2  is a flowchart of generating the sustaining pulses of the panel equivalent capacitor Cp of the PDP by the conventional driving circuit  100  illustrated in  FIG. 1 .  
         [0009]     Step  200 : Start;  
         [0010]     Step  210 : Keep the voltage potentials at the X side and the Y side of the panel equivalent capacitor Cp at ground by turning on the switches S 3  and S 4 ;  
         [0011]     Step  220 : Charge the X side of the panel equivalent capacitor Cp by the capacitor C 1  and keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switches S 6  and S 4 ; wherein the voltage potential at the X side of the panel equivalent capacitor Cp goes up to V 1  accordingly;  
         [0012]     Step  230 : Supply charge to the panel equivalent capacitor Cp of the PDP from the X side by turning on the switches S 1  and S 4 ; wherein the voltage potential at the X side of the panel equivalent capacitor Cp keeps at V 1  and the voltage potential at the Y side of the panel equivalent capacitor Cp keeps at ground accordingly;  
         [0013]     Step  240 : Discharge the panel equivalent capacitor Cp from the X side and keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switches S 5  and S 4 ; wherein the voltage potential at the X side of the panel equivalent capacitor Cp goes down to ground accordingly;  
         [0014]     Step  250 : Keep the voltage potentials at the X side and the Y side of the panel equivalent capacitor Cp at ground by turning on the switches S 3  and S 4 ;  
         [0015]     Step  260 : Charge the Y side of the panel equivalent capacitor Cp by the capacitor C 2  and keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switches S 8  and S 3 ; wherein the voltage potential at the Y side of the panel equivalent capacitor Cp goes up to V 2  accordingly;  
         [0016]     Step  270 : Supply charge to the panel equivalent capacitor Cp of the PDP from the Y side by turning on the switches S 2  and S 3 ; wherein the voltage potential at the Y side of the panel equivalent capacitor Cp keeps at V 2  and the voltage potential at the X side of the panel equivalent capacitor Cp keeps at ground accordingly;  
         [0017]     Step  280 : Discharge the panel equivalent capacitor Cp from the Y side and keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switches S 7  and S 3 ; wherein the voltage potential at the Y side of the panel equivalent capacitor Cp goes down to ground accordingly;  
         [0018]     Step  290 : Keep the voltage potentials at the X side and the Y side of the panel equivalent capacitor Cp at ground by turning on the switches S 3  and S 4 ;  
         [0019]     Step  295 : End.  
         [0020]     Please refer to  FIG. 3 .  FIG. 3  shows a diagram illustrating the voltage potentials at the X side and the Y side of the panel equivalent capacitor Cp, and the control signals, M 1  to M 8 , of the switches S 1  to S 8  in  FIG. 1  respectively. In  FIG. 3 , the horizontal axis represents the time, while the vertical axis represents the voltage potential. Note that the switches S 1  to S 8  are designed to close (turned on) for passing current when the control signal is high, and to open (turned off) such that no current can pass when the control signal is low.  
         [0021]     Conventionally, the energy recovery (power saving) circuit provides two individual channels of charging and discharging the equivalent capacitor respectively (energy-forward channel and energy-backward channel) for each side of the panel equivalent capacitor Cp. Therefore, the amount of required components is quite large. Furthermore, the area of capacitors C 1  and C 2  is usually considerable. Hence the cost of energy recovery circuit is not easy to reduce.  
       SUMMARY OF THE INVENTION  
       [0022]     It is therefore an objective of the invention to provide plasma display panel driving circuits that solve the problems of the prior art.  
         [0023]     According to a preferred embodiment of the present invention, a claimed plasma display panel driving circuit includes a panel equivalent capacitor having a first side and a second side; a first switch electrically connected between the first side of the panel equivalent capacitor and a first voltage; a second switch electrically connected between the first side of the panel equivalent capacitor and a first node; a third switch electrically connected between the first node and a second voltage; a first capacitor electrically connected between the first node and a second node; a fourth switch electrically connected between the second node and the second voltage; a first inductor and a fifth switch electrically connected in series between the second node and a third voltage; a sixth switch electrically connected between the second side of the panel equivalent capacitor and a fourth voltage; a seventh switch electrically connected between the second side of the panel equivalent capacitor and a third node; an eighth switch electrically connected between the third node and a fifth voltage; a second capacitor electrically connected between the third node and a fourth node; a ninth switch electrically connected between the fourth node and the fifth voltage; and a second inductor and a tenth switch electrically connected in series between the fourth node and a sixth voltage.  
         [0024]     According to another preferred embodiment of the present invention, a claimed plasma display panel driving circuit includes a panel equivalent capacitor having a first side and a second side; a first switch electrically connected between the first side of the panel equivalent capacitor and a first voltage; a second switch electrically connected between the second side of the panel equivalent capacitor and a second voltage; a third switch electrically connected between the second side of the panel equivalent capacitor and a first node; a fourth switch electrically connected between the first side of the panel equivalent capacitor and the first node; a fifth switch electrically connected between the first node and a third voltage; a sixth switch electrically connected between the third voltage and a second node; a capacitor electrically connected between the first node and the second node; and an inductor and a seventh switch electrically connected in series between the second node and a fourth voltage.  
         [0025]     It is an advantage that the voltage potential output by the voltage sources is only half of the sustaining voltage produced by the driving circuit. The voltage stress of some components in the driving circuit will therefore be lower. In addition, the numbers of components can be reduced in the driving circuit.  
         [0026]     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  
       [0027]      FIG. 1  is a plasma panel display driving circuit diagram of a prior art.  
         [0028]      FIG. 2  is a flowchart of a prior art method of generating the sustaining pulses of the panel equivalent capacitor Cp.  
         [0029]      FIG. 3  is a diagram illustrating the voltage potentials at sides of the panel equivalent capacitor Cp and the control signals of the switches.  
         [0030]      FIG. 4  shows a circuit diagram of a plasma display panel driving circuit according to a first embodiment of the present invention.  
         [0031]      FIG. 5  is shows a circuit diagram of a plasma display panel driving circuit according to a second embodiment of the present invention.  
         [0032]      FIG. 6  is a flowchart illustrating the operation of the driving circuit of the second embodiment for creating a sustain waveform.  
         [0033]      FIG. 7  shows a circuit diagram of a plasma display panel driving circuit according to a third embodiment of the present invention.  
         [0034]      FIG. 8  is shows a circuit diagram of a plasma display panel driving circuit according to a fourth embodiment of the present invention.  
         [0035]      FIG. 9  is a flowchart illustrating the operation of the driving circuit of the fourth embodiment for creating a sustain waveform. 
     
    
     DETAILED DESCRIPTION  
       [0036]     The present invention provides plasma display panel driving circuits that allow the supplied voltage to be just half of the produced sustaining voltage. The advantages of this invention are that the supplied voltage will be around half of that of the prior art. The voltage stress of some components will therefore be lower. In addition, the numbers of components can be reduced in the driving circuits.  
         [0037]     Please refer to  FIG. 4 .  FIG. 4  shows a circuit diagram of a plasma display panel driving circuit  400  according to a first embodiment of the present invention. The driving circuit  400  comprises switches S 21  to S 30 , capacitors C 21  and C 22 , inductors L 21  and L 22 , and voltage sources V 21  to V 26 . Switches S 22  and S 27  are unidirectional switches, and the direction of the current is indicated by the arrows on  FIG. 4 . The current direction of switch S 22  is away from the voltage source V 21 , and the current direction of switch S 27  is away from the voltage source V 24 . The driving circuit  400  is shown having an panel equivalent capacitor Cp of the PDP, and has an X side and a Y side. The voltage potential output by voltage source V 21  is greater than that of the voltage sources V 22  and V 23 . Likewise, the voltage potential output by the voltage source V 24  is greater than that of the voltage sources V 25  and V 26 . The voltage potentials output by the voltage sources V 21  and V 24  can be the same or can be different. Similarly, the voltage potentials output by the voltage sources V 22  and V 23  and the voltage sources V 25  and V 26  can be the same or can be different. Inductor L 21  and switch S 23  are electrically connected in series, as are inductor L 22  and switch S 28 .  
         [0038]     Please refer to  FIG. 5 .  FIG. 5  is shows 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 a special case of the driving circuit  400  shown in  FIG. 4  in which the voltage sources V 21  and V 24  are the same positive voltage sources, and are labeled as V 3  in  FIG. 5 . In addition, voltage sources V 22 , V 23 , V 25 , and V 26  are all ground. All other components of the driving circuit  500  are the same as the driving circuit  400 .  
         [0039]     Please refer to  FIG. 6 , which illustrates the operation of the driving circuit  500  of the second embodiment for creating a sustain waveform. Steps contained in the flowchart will be explained as follows.  
         [0040]     Step  600 : Start.  
         [0041]     Step  602 : The switches S 22 , S 23 , S 25 , S 27 , S 28 , and S 30  are turned on. The capacitors C 21  and C 22  are charged to the voltage potential of V 3 . The positive terminal of C 21  is at the node of the connection of S 22  and S 24 . The positive terminal of C 22  is at the node of the connection of S 27  and S 29 . The X side and Y side of the panel equivalent capacitor Cp keep at ground.  
         [0042]     Step  604 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 25 . Charge the Y side of the panel equivalent capacitor Cp by turning on the switches S 28  and S 29 . The voltage potential at Y side of the panel equivalent capacitor Cp goes up to twice the voltage potential of V 3  through the components S 28 , S 29 , L 22 , and C 22 .  
         [0043]     Step  606 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 25 . Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at twice the voltage potential of V 3  by turning on the switches S 26  and S 29 .  
         [0044]     Step  608 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 25 . Discharge the Y side of the panel equivalent capacitor Cp by turning on the switches S 28  and S 29 . The voltage potential at Y side of the panel equivalent capacitor Cp goes down to ground through the components S 28 , S 29 , L 22 , and C 22 .  
         [0045]     Step  610 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 25 . Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 30 . In the meantime, the switches S 22  and S 23  are turned on for charging C 21  by V 3 . The switches S 27  and S 28  are turned on for charging C 22  by V 3 .  
         [0046]     Step  612 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 30 . Charge the X side of the panel equivalent capacitor Cp by turning on the switches S 23  and S 24 . The voltage potential at X side of the panel equivalent capacitor Cp goes up to twice the voltage potential of V 3  through the components S 23 , S 24 , L 21 , and C 21 .  
         [0047]     Step  614 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 30 . Keep the voltage potential at the X side of the panel equivalent capacitor Cp at twice the voltage potential of V 3  by turning on the switches S 21  and S 24 .  
         [0048]     Step  616 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 30 . Discharge the X side of the panel equivalent capacitor Cp by turning on the switches S 23  and S 24 . The voltage potential at X side of the panel equivalent capacitor Cp goes down to ground through the components S 23 , S 24 , L 21 , and C 21 .  
         [0049]     Step  618 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 30 . Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 25 . In the meantime, the switches S 22  and S 23  are turned on for charging C 21  by V 3 . The switches S 27  and S 28  are turned on for charging C 22  by V 3 .  
         [0050]     Step  620 : End.  
         [0051]     It is also allowed to keep the voltage potentials at the X and/or Y sides of the panel equivalent capacitor Cp at twice the voltage potential of V 3  when the other side of the panel equivalent capacitor Cp is charged or discharged. In addition, it is also allowed to charge and discharge the X side of the panel equivalent capacitor Cp during the periods of discharging and charging the Y side of the panel equivalent capacitor Cp, respectively.  
         [0052]     Please refer to  FIG. 7 .  FIG. 7  shows a circuit diagram of a plasma display panel driving circuit  700  according to a third embodiment of the present invention. The driving circuit  700  comprises switches S 31  to S 37 , a capacitor C 31 , an inductor L 31 , and voltage sources V 31  to V 34 . Switch S 32  is a unidirectional switch, and the current direction of switch S 32  is away from the voltage source V 31 , as indicated by the arrow in  FIG. 7 . The driving circuit  700  has an panel equivalent capacitor Cp of the PDP, which has an X side and a Y side. The voltage potential output by voltage source V 31  is greater than that of the voltage sources V 32 , V 33 , and V 34 . The voltage potentials output by the voltage sources V 32 , V 33 , and V 34  can be the same or can be different. Inductor L 31  and switch S 33  are electrically connected in series.  
         [0053]     Please refer to  FIG. 8 .  FIG. 8  is shows 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 a special case of the driving circuit  700  shown in  FIG. 7  in which the voltage source V 31  is a positive voltage source V 4 , and the voltage sources V 32 , V 33 , and V 34  are all ground. All other components of the driving circuit  800  are the same as the driving circuit  700 .  
         [0054]     Please refer to  FIG. 9 , which illustrates the operation of the driving circuit  800  of the fourth embodiment for creating a sustain waveform. Steps contained in the flowchart will be explained as follows.  
         [0055]     Step  900 : Start.  
         [0056]     Step  902 : The switches S 32 , S 33 , S 35 , and S 37  are turned on. The capacitor C 31  is charged to the voltage potential of V 4 . The positive terminal of C 31  is at the node of the connection of S 32 , S 34 , and S 36 . The X side and Y side of the panel equivalent capacitor Cp keep at ground.  
         [0057]     Step  904 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 35 . Charge the Y side of the panel equivalent capacitor Cp by turning on the switches S 33  and S 36 . The voltage potential at Y side of the panel equivalent capacitor Cp goes up to twice the voltage potential of V 4  through the components S 33 , S 36 , L 31 , and C 31 .  
         [0058]     Step  906 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 35 . Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at twice the voltage potential of V 4  by turning on the switches S 31  and S 36 .  
         [0059]     Step  908 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 35 . Discharge the Y side of the panel equivalent capacitor Cp by turning on the switches S 33  and S 36 . The voltage potential at Y side of the panel equivalent capacitor Cp goes down to ground through the components S 33 , S 36 , L 31 , and C 31 .  
         [0060]     Step  910 : Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 35 . Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 37 . In the meantime, the switches S 32  and S 33  are turned on for charging C 31  by V 4 .  
         [0061]     Step  912 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 37 . Charge the X side of the panel equivalent capacitor Cp by turning on the switches S 33  and S 34 . The voltage potential at X side of the panel equivalent capacitor Cp goes up to twice the voltage potential of V 4  through the components S 33 , S 34 , L 31 , and C 31 .  
         [0062]     Step  914 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 37 . Keep the voltage potential at the X side of the panel equivalent capacitor Cp at twice the voltage potential of V 4  by turning on the switches S 31  and S 34 .  
         [0063]     Step  916 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 37 . Discharge the X side of the panel equivalent capacitor Cp by turning on the switches S 33  and S 34 . The voltage potential at X side of the panel equivalent capacitor Cp goes down to ground through the components S 33 , S 34 , L 31 , and C 31 .  
         [0064]     Step  918 : Keep the voltage potential at the Y side of the panel equivalent capacitor Cp at ground by turning on the switch S 37 . Keep the voltage potential at the X side of the panel equivalent capacitor Cp at ground by turning on the switch S 35 . In the meantime, the switches S 32  and S 33  are turned on for charging C 31  by V 4 .  
         [0065]     Step  920 : End.  
         [0066]     In summary, the present invention driving circuits utilize switches to make the sustained voltage twice the voltage potential supplied by the voltage source. The voltage stress of some components will therefore be lower. In addition, the numbers of components can be reduced in the driving circuit.  
         [0067]     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.