Abstract:
A driving apparatus for driving a plasma display panel and a method of driving the same are disclosed. The plasma display panel includes multiple display cells, with each of the display cells comprising a sustain electrode, a scan electrode, and a data electrode. Every set of the electrodes has a corresponding driving circuit to provide a required driving waveform for driving the display cell to luminesce. The driving method includes the following steps: first, a first erase pulse, a priming pulse, and a second erase pulse are applied in sequence during a reset period. Then, data pulses corresponding to the display cells are applied during an address period. Lastly, multiple sustain pulses and multiple high frequency driving pulses are applied simultaneously during a sustain period.

Description:
This application claims the benefit of Taiwan application Serial No. 91121713, filed on Sep. 23, 2002. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates in general to a driving apparatus for driving a display and method of driving the same, and more particularly to a driving apparatus for driving a plasma display panel and method of driving the same. 
   2. Description of the Related Art 
   There is an increasing demand for better audio and video service in our daily lives. A conventional CRT (Cathode Ray Tube) display that requires an analog interface to create light and color will become an antiquated technology in the near future as digital TV is brought forth to mainstream broadcasting. A plasma display panel (PDP) with features such as large size, wide-angle viewing, high resolution, and full-color display function will replace the CRT display. 
     FIG. 1  is a perspective view showing a plasma display panel (PDP). The plasma display panel includes a front plate  102  and a rear plate  108 . Multiple sustain electrodes X are parallel and are paired with multiple scan electrodes Y, respectively, which are on the surface of the front plate  102  opposite to the rear plate  108 . The multiple sustain electrodes X and scan electrodes Y are covered by a dielectric layer  104 . The dielectric layer  104  is covered by a protective film  106 , which is made of MgO (magnesium oxide), to protect the multiple sustain electrodes X, scan electrodes Y, and the dielectric layer  104 . In addition, multiple data electrodes (or called address electrodes) A are situated in parallel and are located on the rear plate  108  and are also covered by a dielectric layer  116 . The multiple data electrodes A are perpendicular to the multiple sustain electrodes X and the multiple scan electrodes Y Multiple barrier ribs  112  are formed along the length of the rear plate  108  in parallel with the data electrodes A. Adjacent barrier ribs  112  and the rear plate  108  form a substantial U-shaped trench. A phosphor layer  110  is formed and is located between every two adjacent ribs  112 . 
   The chamber sandwiched between the front plate  102  and the rear plate  108  is discharge space, which is filled with a discharge gas mixture of Ne (neon) and Xe (xenon). A display cell is defined by every pair of sustain electrodes X and scan electrode Y on the front plate  102  corresponding to the data electrodes A on the rear plate  108 . Accordingly, multiple display cells are combined into a row-and-column matrix and are defined by the multiple sustain electrodes X, the scan electrodes Y, and the data electrodes A on the plasma display panel. 
     FIGS. 2A and 2B  show a timing diagram of driving waveform for conventionally driving a display cell of the plasma display panel. The display cell displays a frame in each frame period. Each of the frame periods includes multiple subframe periods. A driving circuit applies a driving waveform to the display cell in every subframe period, which drives the display cell either to luminesce or not luminesce. Every subframe period can be divided into a three phase sequence: a reset period T 1 , an address period T 2 , and a sustain period T 3 . In the reset period T 1 , the scan electrodes Y first output an erase pulse P Y1  to eliminate wall charges accumulated near the sustain electrodes X and the scan electrodes Y during the previous subframe period. Afterwards, a priming pulse is applied to excite the discharge gases in the discharge space and enable ionization to again release discharge ions, which are needed for the display cell to luminesce, and also have the states of the active discharge ions of every display cell in the plasma display panel be identically excited. A manner of applying the priming pulse can be to have the sustain electrodes X output a high voltage to excite a pulse P X2 , as shown in  FIG. 2A , or to have the sustain electrodes X and the scan electrodes Y, respectively, output pulses P X2  and P Y2  with opposite polarities, as shown in  FIG. 2B . Furthermore, the priming pulse can be not only a square wave, but also a saw-tooth wave of the same waveform as the erase pulse P Y1 . Lastly, the driving circuit applies an erase pulse P Y3  to the scan electrodes Y to eliminate wall charges in the display cell. In the address period T 2 , data pulses according to the image data are applied to data electrodes A to write wall charges into the display cells. In the sustain period T 3 , gas discharge occurs in the display cells with wall charge written in the address period T 2  while alternating sustain pulses are applied to the sustain electrodes X and the scan electrodes Y, and also the discharge ions collide against each other constantly in the discharge space, so as to generate ultraviolet (UV) rays of the designated wavelength. The phosphor layer can emit visible light continually after absorbing the ultraviolet (UV) rays of the designated wavelength. 
   In comparison with other display models, such as the CRT (Cathode Ray Tube) display or the LCD (Liquid Crystal Display), a shortcoming of the plasma display panel is that the luminous and the luminance efficiency are inferior to other models. The critical problem that needs to be solved, then, is to determine how to enhance the luminous and the luminance efficiency of plasma display panels. 
   SUMMARY OF THE INVENTION 
   It is therefore an objective of the invention to provide a driving apparatus for driving a plasma display panel and method of driving the same, which can not only enhance the luminous and the luminance efficiency of the plasma display panel, but also enhance the display frame quality of the plasma display panel. 
   The invention achieves the above-identified objectives by providing a driving apparatus for driving a plasma display panel and method of driving the same. The plasma display panel includes a plurality of display cells, with each of the display cells including a sustain electrode, a scan electrode, and a data electrode. Each set of the sustain electrodes, scan electrodes, and data electrodes has a corresponding driving circuit to provide a required driving waveform for driving the display cell to luminesce. The driving method includes the following steps: first, a first erase pulse, a priming pulse, and a second erase pulse are applied in sequence during a reset period. Then, data pulses corresponding to the display cells are applied during an address period. Last, multiple sustain pulses and high frequency driving pulses are applied simultaneously during a sustain period. 
   Other objectives, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  (prior art) is a perspective view showing a conventional plasma display panel (PDP). 
       FIGS. 2A and 2B  (prior art) are timing diagrams illustrating conventional driving waveforms for driving a display cell of the plasma display panel. 
       FIG. 3  shows a timing diagram of driving waveforms for driving the display cell according to a preferred embodiment of the invention. 
       FIG. 4  illustrates a circuit diagram of a high-frequency driving pulse generator according to the preferred embodiment of the invention. 
       FIG. 5  shows a timing diagram of a control signal and an output signal from the high-frequency driving pulse generator provided by the preferred embodiment of the invention. 
       FIGS. 6A–6C  show the equivalent circuit diagrams of the high-frequency driving pulse generator provided by the preferred embodiment according to the invention. 
       FIG. 7  shows a timing diagram illustrating driving signals during sustain period according to the preferred embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 2A ,  2 B, and  3 , simultaneously,  FIG. 3  shows a timing diagram of driving waveforms for driving the display cell according to a preferred embodiment of the invention. The greatest difference between the driving waveforms of the invention and the driving waveforms shown in the prior art is that high frequency driving pulses at a frequency of about 1 MHz or above will be continually applied to the data electrodes, while at the same time the sustain pulses is applied to the sustain electrodes X and the scan electrodes Y alternately during the sustain period. 
     FIG. 4  shows a circuit diagram for a high-frequency driving pulse generator according to the preferred embodiment of the invention. The high-frequency driving pulse generator is coupled to the data electrodes, and is employed to apply the high frequency driving pulses to the data electrodes. The high-frequency driving pulse generator of the preferred embodiment includes a voltage source V D , a first switch M 1 , a second switch M 2 , an inductor L, and a diode D. The voltage source V D  supplies a direct current (D.C.) voltage, with a positive end connected to the first switch M 1  and a negative end connected to ground GND. The first switch M 1  and the second switch M 2  are both n type metal oxide semiconductor field effect transistors (MOSFET). The drain electrode of the first switch M 1  is connected to the voltage source V D , while a source electrode is connected to the drain electrode of the second switch M 2 . The source electrode of the second switch M 2  is connected to the ground GND. The diodes D 1  and D 2  are the body diodes of switches M 1  and M 2 , respectively. The anode of the diode D is connected to the inductor L, while the cathode of the diode D is connected to the drain electrode of first switch M 1 . Also, one end of the inductor L is connected to both the source electrode of the first switch M 1  and the drain electrode of the second switch M 2 , while the other end is connected to the anode of diode D. 
   The plasma display panel includes front and rear plates, and the electrodes are formed on the front and rear plates, thereby inducing an equivalent capacitance between the electrodes. In  FIG. 4 , this equivalent capacitance is represented by an equivalent capacitor C. The high-frequency driving pulse generator is coupled to the data electrodes of the rear plate at one node a, and to a ground of the display system of the plasma display panel at a node b. 
     FIG. 5  shows a timing diagram for a control signal and an output waveform from the high-frequency driving pulse generator of the preferred embodiment. The high-frequency driving pulse generator controls its output signals by controlling the first switch M 1  and the second switch M 2  to be on and off. As shown in  FIG. 5 , the control method of the high-frequency driving pulse generator includes four steps, which are described in sequence, as follows:
     1. t 1 ≦t≦t 2 :   
   Referring to  FIG. 5 , the first switch M 1  is turned on and the second switch M 2  is turned off when t=t 1 . An equivalent circuit representation of the high-frequency driving pulse generator is shown in  FIG. 6A . When t=t 1 , the voltage on the equivalent capacitor C of the panel is 0V, and the inductor current I 1  flows from the voltage source V D  through the inductor L to charge the equivalent capacitor C of the panel. The voltage on the equivalent capacitor C of the panel V ab  begins to increase at this moment. When the voltage V ab  is equal to a DC voltage value of the voltage source V D , the diode D is forward biased. Therefore, the output voltage signal V ab  is clamped at the DC voltage value output by the voltage source V D , as shown in  FIG. 5 .
     2. t 2 ≦t≦t 3 :   

   Referring to  FIG. 5 , the first switch M 1  is turned off when t=t 2 . An equivalent circuit representation of the high-frequency driving pulse generator is shown in  FIG. 6B . The direction of the inductor current I 2  in  FIG. 6B  is the same as that of the inductor current I 1  in  FIG. 6A  because of the continuity of the inductor current. The induced current I 2  from the inductor L flows through the diode D to the voltage source V D . The output voltage signal V ab  is still equal to the DC voltage value output by the voltage source V D , as shown in  FIG. 5 .
     3. t 3 ≦t≦t 4 :   

   Referring to  FIG. 5 , the second switch M 2  is turned on when t=t 3 . An equivalent circuit diagram of the high-frequency driving pulse generator is shown in  FIG. 6C . The inductor L starts to resonate with the equivalent capacitor C of the panel. In this case, the voltage V ab  starts to oscillate and the oscillating frequency is determined by the inductance value of the inductor L and the equivalent capacitance value of the equivalent capacitor C of the panel. 
   Due to the existence of inherent resistance, the equivalent circuit of the high-frequency driving pulse generator is not an ideal LC oscillating circuit. Consequently, the peak-to-peak value of the voltage V ab  will decrease gradually, as shown in  FIG. 5 . 
   In  FIG. 5 , the average value of the voltage V ab  is zero, and the maximum peak value of the voltage V ab  is equal to the DC voltage value of the voltage source V D ; however, the invention is not limited thereto. The invention can also be achieved by adding a DC bias circuit to the high-frequency driving pulse generator so that the average value of the output voltage signal V ab  is a non-zero DC bias voltage, for example, equal to the DC voltage value of the voltage source V D .
     4. t 4 ≦t:   

   Referring to  FIG. 5 , the second switch M 2  is turned off when t=t 4 . At this time, the first and second switches M 1  and M 2  are off, and the value of the output voltage signal V ab  is zero. 
     FIG. 7  shows a timing diagram of driving waveforms during the sustain period according to the preferred embodiment of the invention. The high-frequency driving pulse generator is coupled to the data electrode A. The first switch M 1  of the high-frequency driving pulse generator is turned on so as to apply a pulse with steep slope to the data electrode A to output a pulse signal with while the sustain pulse is applied to the sustain electrode X or the scan electrode Y. Then the second switch M 2  is turned on and the first switch M 1  is turned off, and the high-frequency driving pulse generator applies high frequency driving pulses to the data electrode A. The high frequency driving pulses will influence the motion of the discharge ions in the discharge space by repel or attract the discharge ions so as to increase the probability of collision between the discharge ions. It will help to excite the discharge gas in the discharge space of the display cell and generate more ultraviolet (UV) to excite the phosphor in the phosphor layer so that more visible light is emitted. In addition to the above process to increase the amount of UV rays produced by the collisions between excited ions, UV rays of specifically designated wavelengths can also be produced through control of the peak-to-peak value and frequency of the high frequency driving pulses, thereby more effectively producing visible light through the phosphors in the phosphor layer to absorb the UV rays. Therefore, in comparison with the method of the prior art, the driving signal for driving the display cell of the plasma display panel according to the invention not only can enhance the luminance and the luminance efficiency of the plasma display panel but also can enhance the display quality of the plasma display panel. 
   The driving apparatus for driving a plasma display panel and method of driving the same according to the above-mentioned embodiments of the invention can enhance the effect of the luminance and the luminance efficiency of the plasma display panel. It can also enhance the display quality of the plasma display panel. 
   While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.