Abstract:
A display device comprising a driving voltage generating apparatus, a driver circuit, and a display panel is disclosed. The driving voltage generating apparatus comprises a transformer element, a plurality of current-limiting elements, and a plurality of voltage-stabilizing elements. The transformer element has a plurality of secondary coils, which, coupled with current-limiting element capable of rectification and voltage-stabilizing element capable of filtering out noise, allows the driving voltage generating apparatus to output simultaneously positive voltage and negative voltage needed by the driver circuit of the display.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a display device, more particularly a display device having high-performance driving voltage generating apparatus.  
         [0003]     2. Description of the Prior Art  
         [0004]     Among the wide varieties of electronic products, display devices of various kinds (e.g. cold cathode tube display, liquid crystal display panel and plasma display panel) are gaining popularity. With the advancement of manufacturing technology, display devices are able to meet the demands for size, picture quality, weight and price.  
         [0005]     But irrespective of the type of display, they all use panel to display images and pictures. Such panel typically contains many crisscross scan lines, which when driven under proper driving voltage, can display images accurately on the display panel.  
         [0006]      FIG. 1  is a schematic view of a display panel, assuming the display panel  108  will display images accurately when it is driven by a voltage having waveform  106 . Voltage waveform  106  is a square waveform having positive and negative voltages needed by the positive voltage input V s1  and negative voltage input −V s2  of driver circuit  104 . Thus an element that can generate such positive voltage and negative voltage is required for driver circuit  104  to produce voltage waveform  106 .  
         [0007]     In typical circuitry, transformer shown as  102  in  FIG. 1  is commonly used to provide the required voltage. But a simple transformer is designed only to produce one voltage. For example, after a voltage V in  is input into transformer  102 , an output of transformer must be connected to ground potential GND, while its other output can only output the positive voltage needed by driver circuit  104 .  
         [0008]     To produce the negative voltage needed by driver circuit  104 , an inverter circuit  110  must be added to the voltage supply scheme. The inverter circuit  110  can reverse the polarity of voltage. So it is bridged over the output of transformer  102  to receive its positive voltage output and convert the positive voltage into negative voltage before inputting it into the negative voltage input −V s2  of driver circuit  104 . As such, the positive voltage input V s1  and negative voltage input −V s2  of driver circuit  104  will obtain respectively a positive voltage and a negative voltage.  
         [0009]     It is well known in the art of circuitry design that an inverter circuit  110  contains at least a plurality of transistors, so certain loss occurs in each component when the positive voltage output from transformer  102  is processed by inverter circuit  110 . As a result, the quality of negative voltage produced is not as expected and leads to loss of electrical energy efficiency. Moreover, inverter circuit  110  requires a separate control circuit (not shown in  FIG. 1 ) to control its operation. When small size and light weight are requisites of a display device, inverter circuit  110  apparently will take considerable space of the circuitry, which makes further shrinkage of display size difficult and adds to the production cost.  
         [0010]     As described above, a driving voltage generating apparatus that is smaller, costs less and offers better operating efficiency is needed for display device.  
       SUMMARY OF INVENTION  
       [0011]     The primary object of the present invention is to provide a display device.  
         [0012]     Another object of the present invention is to provide a display device having a driving voltage generating apparatus that can supply positive and negative output voltages simultaneously.  
         [0013]     A further object of the present invention is to provide a display device having a highly efficient driving voltage generating apparatus.  
         [0014]     Yet another object of the present invention is to provide a low-cost and small-size display device configuration.  
         [0015]     To achieve the aforesaid objects, an example of the display device according to the present invention uses a display panel, a driver circuit and a driving voltage generating apparatus, wherein the driver circuit is for driving the display panel and comprises at least one positive voltage input and at least one negative voltage input, while the driving voltage generating apparatus is for supplying positive voltage and negative voltage needed by the positive voltage input and negative voltage input.  
         [0016]     The driving voltage generating apparatus in one example of the present invention comprises a transformer element, at least one first current-limiting element, at least one second current-limiting element, at least one first voltage-stabilizing element, and at least one second voltage-stabilizing element. The transformer element contains at least a primary coil, at least one first secondary coil, and at least one second secondary coil, and the homopolar end of the first secondary coil and the heteropolar end of the second secondary coil are connected to a ground potential. The forward terminal and the backward terminal of the first current-limiting element are respectively connected to the heteropolar end of first secondary coil and the positive voltage input. The forward terminal and the backward terminal of the second current-limiting element are respectively connected to negative voltage input and homopolar end of second secondary coil. The two ends of the first voltage-stabilizing element are respectively connected to the backward terminal of first current-limiting element and the homopolar end of first secondary coil. The two ends of second voltage-stabilizing element are respectively connected to the forward terminal of second current-limiting element and the heteropolar end of second secondary coil.  
         [0017]     In another example of the present invention, the driving voltage generating apparatus comprises a transformer element, at least one first current-limiting element, at least one second current-limiting element, at least one third current-limiting element, at least one fourth current-limiting element, at least one first voltage-stabilizing element, and at least one second voltage-stabilizing element. The transformer element comprises at least a primary coil, at least one first secondary coil, at least one second secondary coil, at least one third secondary coil, and at least one fourth secondary coil. The homopolar end of first secondary coil, the heteropolar end of second secondary coil, the homopolar end of third secondary coil, and the heteropolar end of fourth secondary coil are all connected to a ground potential. In addition, the forward terminal and the backward terminal of first current-limiting element are respectively connected to the heteropolar end of first secondary coil and positive voltage input. The forward terminal and the backward terminal of second current-limiting element are respectively connected to the homopolar end of second secondary coil and the backward terminal of first current-limiting current. The forward terminal and the backward terminal of third current-limiting element are respectively connected to negative voltage input and heteropolar end of third secondary coil. The forward terminal and the backward terminal of fourth current-limiting element are respectively connected to forward terminal of third current-limiting element and homopolar end of fourth secondary coil. The two ends of first voltage-stabilizing element are respectively connected to the backward terminal of first current-limiting element and homopolar end of first secondary coil. The two ends of second voltage-stabilizing element are respectively connected to the forward terminal of fourth current-limiting element and heteropolar end of fourth secondary coil.  
         [0018]     In this example, the first current-limiting element, the second current-limiting element, the third current-limiting element, and the fourth current-limiting element are diodes, where the forward terminals and backward terminals of the current-limiting elements are respectively anode and cathode of the diode. The first voltage-stabilizing element and the second voltage-stabilizing element are capacitors. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The details of the present invention will be more readily understood from a detailed description of the preferred embodiments taken in conjunction with the following figures.  
         [0020]      FIG. 1  is a schematic view of a conventional display device configuration.  
         [0021]      FIG. 2  is a schematic view of an example of display device configuration according to the invention.  
         [0022]      FIG. 3  is a schematic view of another example of display device configuration according to the invention. 
     
    
     DETAILED DESCRIPTION  
       [0023]     In the driving voltage generating apparatus of conventional display panels, the transformer usually supplies either a positive voltage or negative voltage to maintain voltage stability. In such design, the driver circuit relies on an external inverter circuit to produce the negative voltage or positive voltage it needs, which not only incurs energy loss, but also takes more circuitry space. The basic concept of the present invention is to allow the transformer element to supply at the same time positive voltage and negative voltage with no need for inverter circuit.  
         [0024]     The objects, features, and advantages of the present invention are further described below with accompanying drawings.  
         [0025]      FIG. 2  is a schematic view of a display device configuration according to the invention. The display device comprises a driving voltage generating apparatus  200 , a driver circuit  104 , and a display panel  108 . The driving voltage generating apparatus  200  comprises a transformer element  201 , a first current-limiting element  208 , a second current-limiting element  210 , a first voltage-stabilizing element  212  and a second voltage-stabilizing element  214 . The current-limiting element is, for example, a diode, and the voltage-stabilizing element is, for example, a capacitor. The transformer element  201  comprises three coils: a primary coil  202 , a first secondary coil  204  and a second secondary coil  206 . The primary coil  202  has two ends  216  and  218  to receive input voltage V in . Based on the principles of transformer, the two ends of those three coils are respectively a homopolar end and a heteropolar end. The homopolar ends are indicated by a round dot. For example, the end  216  of primary coil  202  is a homopolar end, and the end  218  of coil  202  is a heteropolar end.  
         [0026]     Next the connections of those elements are described. The input ends  216  and  218  of primary coil  202  are connected to input voltage V in , while the homopolar end of first secondary coil  204  and the heteropolar end of second secondary coil  206  are connected to the ground potential GND of the entire display system. The forward terminal of first current-limiting element  208  is connected to the heteropolar end of first secondary coil  204 , while the backward terminal of first current-limiting element  208  is connected to the positive voltage input V s1  of driver circuit  104 , so as to provide positive voltage to the positive voltage input V s1  of driver circuit  104 . The forward terminal and the backward terminal of current-limiting elements  208  and  210  represent respectively the anode and cathode of diode. The backward terminal of second current-limiting element  210  is connected to the homopolar end of second secondary coil  206 . The forward terminal of second current-limiting element  210  is connected to the negative voltage input −V s2  of driver circuit  104 , so as to provide negative voltage to the negative voltage input −V s2  of driver circuit  104 . The two ends of first voltage-stabilizing element  212  are respectively connected to positive voltage input V s1  and ground potential GND, and the two ends of second voltage-stabilizing element  214  are respectively connected to negative voltage input −V s2  and ground potential GND.  
         [0027]     In light that input voltage V in  is an AC voltage generated by the action of alternating power, the current flowing on primary coil  202  would cyclically switch direction. First when a cyclic current flows through primary coil  202  from end  218  to end  216 , currents I 1  and I 2  would be induced on first secondary coil  204  and second secondary coil  206  respectively. Because currents I 1  and I 2  are forward current to first current-limiting element  208  and second current-limiting element  210 , the positive voltage generated from both ends of first secondary coil  204  are relayed to the backward terminal of first current-limiting element  208  to produce positive voltage needed by the positive voltage input V s1 , while the negative voltage generated from both ends of second secondary coil  206  may be relayed to the forward terminal of second current-limiting element  210  to produce negative voltage needed by negative voltage input −V s2 . The first voltage-stabilizing element  212  and second voltage-stabilizing element  214  are used respectively to isolate noises between positive voltage, ground potential GND and negative voltage.  
         [0028]     Conversely when another cyclic current flows through primary coil  202  from end  216  to end  218 , currents in reverse direction to I 1  and I 2  would be induced on first secondary coil  204  and second secondary coil  206  respectively. At this time because of the action of first current-limiting element  208  and second current-limiting element  210 , no voltage would be generated on positive voltage input V s1  or negative voltage input −V s2 . That is, the driving voltage generating apparatus  200  shown in  FIG. 2  has a half-cycle configuration, which saves more circuit space and costs.  
         [0029]      FIG. 3  is the schematic view of another display device configuration according to the invention. The display device comprises a driving voltage generating apparatus  300 , a driver circuit  104 , and a display panel  108 . The driving voltage generating apparatus  300  comprises a transformer element  301 , a first current-limiting element  312 , a second current-limiting element  314 , a third current-limiting element  316 , a fourth current-limiting element  318 , a first voltage-stabilizing element  320  and a second voltage-stabilizing element  322 . The transformer element  301  comprises five coils—a primary coil  302 , a first secondary coil  304 , a second secondary coil  306 , a third secondary coil  308 , and a fourth secondary coil  310 . The primary coil  302  has two ends  324  and  326  to receive input voltage V in . Based on the basic principles of transformer, the two ends of those five coils are respectively a homopolar end and a heteropolar end. The homopolar ends are indicated by a round dot. For example, the end  324  of primary coil  302  is a homopolar end, and the end  326  of primary coil  302  is a heteropolar end.  
         [0030]     Next the connections of those elements are described. The input ends  324  and  326  of primary coil  302  are connected to input voltage V in , while the homopolar ends of first secondary coil  304  and third secondary coil  308  and the heteropolar ends of second secondary coil  306  and fourth secondary coil  310  are connected to the ground potential GND of the entire display system. The forward terminal of first current-limiting element  312  is connected to the heteropolar end of first secondary coil  304 , while the backward terminal of first current-limiting element  312  is connected to the positive voltage input V s1  of driver circuit  104 , so as to provide positive voltage to the positive voltage input V s1  of driver circuit  104 . The forward terminal of second current-limiting element  314  is connected to the homopolar end of second secondary coil  306 , while the backward terminal of second current-limiting element  314  is connected to the positive voltage input V s1  of driver circuit  104 , so as to supply positive voltage to the positive voltage input V s1  of driver circuit  104 . The forward terminal of third current-limiting element  316  is connected to the negative voltage input −V s2  of driver circuit  104 , while the backward terminal of third current-limiting element  316  is connected to the heteropolar end of third secondary coil  308 , so as to supply negative voltage to the negative voltage input −V s2  of driver circuit  104 .  
         [0031]     The backward terminal of fourth current-limiting element  318  is connected to the homopolar end of fourth secondary coil  310 , while the forward terminal of fourth current-limiting element  318  is connected to the negative voltage input −V s2  of driver circuit  104 , so as to supply negative voltage to the negative voltage input −V s2  of driver circuit  104 . The two ends of first voltage-stabilizing element  320  are respectively connected to positive voltage input V s1  and ground potential GND, and the two ends of second voltage-stabilizing element  322  are respectively connected to negative voltage input −V s2  and ground potential GND.  
         [0032]     In light that input voltage V in  is an AC voltage generated by the action of alternating power, the current flowing on primary coil  302  would cyclically switch direction. First when a cyclic current flows through primary coil  302  from end  326  to end  324 , currents I 3  and I 6  would be induced on first secondary coil  304  and fourth secondary coil  310  respectively. Because currents I 3  and I 6  are forward current to first current-limiting element  312  and fourth current-limiting element  318 , the positive voltage generated from both ends of first secondary coil  304  are relayed to the backward terminal of first current-limiting element  312  to produce positive voltage needed by the positive voltage input V s1 , while the negative voltage generated from both ends of fourth secondary coil  310  may be relayed to the forward terminal of fourth current-limiting element  318  to produce negative voltage needed by negative voltage input −V s2 . At this time because of the action of second current-limiting element  314  and third current-limiting element  316 , no current would pass through second secondary coil  306  or third secondary coil  308 . The first voltage-stabilizing element  320  and second voltage-stabilizing element  322  are used respectively to isolate noises between positive voltage, ground potential GND and negative voltage.  
         [0033]     Conversely when another cyclic current flows through primary coil  302  from end  324  to end  326 , currents in reverse direction to I 4  and I 5  would be induced on second secondary coil  306  and third secondary coil  308  respectively. Because currents I 4  and I 5  are forward current to second current-limiting element  314  and third current-limiting element  316 , the positive voltage generated from both ends of second secondary coil  306  are relayed to the backward terminal of second current-limiting element  314  to produce positive voltage needed by the positive voltage input V s1 , while the negative voltage generated from both ends of third secondary coil  308  may be relayed to the forward terminal of third current-limiting element  316  to produce negative voltage needed by negative voltage input −V s2 . At this time because of the actions of first current-limiting element  312  and fourth current-limiting element  318 , no current would pass through first secondary coil  304  or fourth secondary coil  310 . That is, the driving voltage generating apparatus  300  shown in  FIG. 3  has a full-cycle configuration, which could enhance the use efficiency of electric energy.  
         [0034]     From the examples provided above, either the configuration of half-cycle action or full-cycle action scraps the needs for an external inverter circuit to provide the positive voltage and negative voltage needed by the driver circuit of display device. And, the magnitude of voltage output may be decided by the turns of the primary coil and secondary coil and the duty cycle thereof, which gives the designer more flexibility. The aforesaid examples use diodes and capacitors to perform the functions of current-limiting elements and voltage-stabilizing elements, in which, the anode and cathode of the diode are respectively the forward terminal and backward terminal of current-limiting element. Other devices that can achieve the same objectives may also be used. By the same principle, if the driver circuit in the display configuration requires several sets of positive voltage and negative voltage, it can be achieved by adding more sets of secondary coils in the transformer element. The presence of more sets of secondary coils can provide more sets of positive voltage and negative voltage. Thus the number of primary coil and secondary coil is not limited by the examples described above.  
         [0035]     Preferred embodiments of the present invention have been disclosed in the examples. However the descriptions made in the examples should not be construed as a limitation on the actual applicable scope of the present invention, and as such, all modifications and alterations without departing from the spirits of the invention shall remain within the protected scope and claims of the invention.