Patent Document

BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention generally relates to an LCD device, an electronic apparatus and an electronic system, and more particularly to an LCD device having a pixel electrode and a pixel driving transistor. 
         [0003]    2. Description of Prior Art 
         [0004]    With advantages of lightweight and low electricity power consumption, LCD devices are used as monitors for the electronic apparatus such as a computer or a mobile phone. In an active matrix display device which employs the thin film transistors (TFT) for applying voltages to the pixels electrodes, the TFTs are positioned between the data lines and the pixels electrodes. The gate lines are utilized to switch the aforesaid TFTs and provide the voltages which are applied to data lines to the pixels electrodes as disclosed in Japan Patent Publication No. 2007-188079. 
         [0005]    For extending the service lifespan of the LCD device, the applied voltages between the pixel electrodes and the common electrode are inverted for each frame to force the voltages applied to the liquid crystals to be inverted correspondingly in the LCD device. Meanwhile, non-inverted and inverted voltages can be applied to the scan lines in one frame to control the liquid crystals not to be merely twisted toward a single direction. 
         [0006]    Please refer to  FIG. 16 , which shows waveforms of gate line driving method of an embodiment according to prior arts.  FIG. 16(A)  shows waveforms of a first liquid crystal driving status and  FIG. 16(B)  shows waveforms of a second liquid crystal driving status. The solid lines represent gate voltages Vg, Vg′. The dotted lines represent source voltages Vs. Vs′. The one-dot chain lines represent drain voltages Vd, Vd′. The two-dot chain lines represent a common voltage Vcom applied to a common electrode. 
         [0007]    In the gate line driving method of the prior arts as shown in  FIG. 16 , the gate voltage Vg is unrelated to the first liquid crystal driving status or the second liquid crystal driving status but a fixed value. Therefore, when the gate voltage Vg becomes the base voltage Vgl as the TFT is turned off in the first liquid crystal driving status as shown in  FIG. 16(A) , the voltage difference between the base voltage Vgl of the gate voltage Vg and the drain voltage Vd is 2.3V. However, in the second liquid crystal driving status shown in  FIG. 16(B) , the voltage difference between the base voltage Vgl′ of the gate voltage Vg′ and the base voltage Vsl′ of the source voltage Vs′ is increased up to 7.5V. Consequently, the difference of the off-status currents Ioff of the TFT exists between the first liquid crystal driving status and the second liquid crystal driving status. Significantly, the difference of the off-status currents Ioff between the first liquid crystal driving status and the second liquid crystal driving status is one of the reasons causing the picture quality deterioration and causing a flicker phenomenon on the screen. 
       SUMMARY 
       [0008]    The disclosure is directed to an LCD device, an electronic apparatus and an electronic system capable of reducing the flicker. 
         [0009]    The LCD device of an embodiment has a pixel electrode and a pixel driving transistor. The drain of the pixel driving transistor is coupled to the pixel electrode, and the source of the pixel driving transistor is coupled to a source bus. The pixel driving transistor controls a voltage applied to the pixel electrode corresponding to a gate voltage applied to the gate of the pixel driving transistor. The LCD device of an embodiment comprises a capacitor, a gate voltage control transistor and a source driving circuit. The capacitor is coupled to the gate of the pixel driving transistor and holds the voltage at the gate of the pixel driving transistor. The drain of the gate voltage control transistor is coupled to a connection point between the gate of the pixel driving transistor and the capacitor, the source of the control transistor is coupled to the source bus and the gate of the control transistor is coupled to a gate line. The gate voltage control transistor is used for controlling the voltage applied to the capacitor. The source driving circuit utilizes adjacent source bus lines to alternately switch the voltages held by the capacitor among several different high voltages and several different low voltages to drive the source of the pixel driving transistor. 
         [0010]    Moreover, the source driving circuit of an embodiment further comprises a multiplexer, a first high voltage source, a second high voltage source, a first low voltage source, a second low voltage source, a voltage selecting circuit and a voltage switching circuit. The multiplexer provides a source voltage of the pixel electrode to the source bus. The first high voltage source generates a first high level voltage. The second high voltage source generates a second high level voltage that is higher than the first high level voltage. The first low voltage source generates a first low level voltage that is lower than the first and second high level voltages. The second low voltage source generates a second low level voltage that is lower than the first low level voltage. The voltage selecting circuit selectively outputs one of the first high level voltage and the second high level voltage to a first output line, and outputs one of the first low level voltage and the second low level voltage to a second output line according to a selection signal. The voltage switching circuit provides the voltages outputted by the first output line and the second output line to the source bus when the voltage applied to the capacitor is held and alternately provides the outputs of the multiplexer to the source bus when the source voltage is applied to the source of the pixel driving transistor. 
         [0011]    In addition, the voltage selecting circuit of an embodiment further comprises a first voltage level selecting unit, a second voltage level selecting unit, a third voltage level selecting unit and a fourth voltage level selecting unit. The first voltage level selecting unit outputs the first high level voltage or the second high level voltage, the first low level voltage or the second low level voltage according to a voltage level selecting signal. The second voltage level selecting unit outputs the second high level voltage or the first high level voltage, the second low level voltage or the first low level voltage according to the voltage level selecting signal. The third voltage level selecting unit outputs either the first high level voltage or the second high level voltage, as well as either the first low level voltage or the second low level voltage from the first voltage selecting unit to first source bus lines according to a source bus switching signal. The fourth voltage level selecting unit outputs either the second high level voltage or the first high level voltage, as well as either the second low level voltage or the first low level voltage from the second voltage selecting unit to second source bus lines adjacent to the first source bus lines according to the source bus switching signal. The first and second source bus lines are alternatively arranged. 
         [0012]    According to some embodiments, the LCD device has a pixel electrode and a pixel driving transistor. The pixel driving transistor has a drain thereof coupled to the pixel electrode, a source thereof coupled to a source bus to control a voltage applied to the pixel electrode according to the gate voltage applied to a gate of the pixel driving transistor. By using the design of some embodiments, the alteration of the voltages between the gate and the source of the gate voltage control transistor or the alteration of the voltage between the gate and the drain of the aforesaid gate voltage control transistor can be diminished. Therefore, alteration of the voltage applied to the drain of the pixel driving transistor can be diminished accordingly to reduce the flicker. In the aforesaid design, the capacitor is coupled to the gate of the pixel driving transistor to hold the voltage at the gate of the pixel driving transistor, the drain of the control transistor is coupled to a connection point between the gate of the pixel driving transistor and the capacitor, the source of the control transistor is coupled to the source bus and the gate of the control transistor is coupled to the gate line to control the voltage applied to the capacitor; furthermore, the source driving circuit utilizes adjacent source bus lines to alternately switch the voltages held by the capacitor among several different high voltages and several different low voltages to drive the source of the pixel driving transistor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a functional diagram showing a system of an embodiment according to the present invention. 
           [0014]      FIG. 2  depicts a diagram showing major components of the display unit  105 . 
           [0015]      FIG. 3  depicts a block diagram of the source bus driving circuit  104 . 
           [0016]      FIG. 4  depicts a circuit diagram of the voltage selecting circuit  211 . 
           [0017]      FIG. 5  shows a block circuit diagram of the display device in an initial status according to the present invention. 
           [0018]      FIG. 6  shows a block circuit diagram of the display device when the gate voltage is held according to the present invention. 
           [0019]      FIG. 7  shows a block circuit diagram of the display device when the gates are opened (turned off) according to the present invention. 
           [0020]      FIG. 8  shows a block circuit diagram of the display device during executing the write operation according to the present invention. 
           [0021]      FIG. 9  shows a block circuit diagram of the display device during executing the write operation according to the present invention. 
           [0022]      FIG. 10  shows a block circuit diagram of the display device during executing the write operation according to the present invention. 
           [0023]      FIG. 11  shows a block circuit diagram of the display device when the write operation is finished according to the present invention. 
           [0024]      FIG. 12  shows a block circuit diagram of the display device when the voltages applied to the capacitors Ck becomes low level according to the present invention. 
           [0025]      FIG. 13  shows a block circuit diagram of the display device recovered back to the initial status according to the present invention. 
           [0026]      FIG. 14  shows a timing diagram of the write operation to the pixel according to the present invention. 
           [0027]      FIG. 15  depicts waveforms of the operation to the pixel driving transistor Md. 
           [0028]      FIG. 16  shows waveforms of a gate lines driving method of an embodiment according to prior arts. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Please refer to  FIG. 1 , which is a functional diagram showing a system of an embodiment according to the present invention. An LCD device  100  is described as an embodiment for explaining the present invention accordingly. For example, the LCD device  100  can be an active matrix display device. The active matrix display device comprises an interface  101 , a controller  102 , a gate driving circuit  103 , a source driving circuit  104  and a display unit  105 . The interface  101  is coupled with an interface of a host control device of the LCD device  100  to receive display data therefrom. The controller  102  generates control signals for the display unit  105  according to the display data received via the interface  101 . And then, the controller  102  provides the aforesaid control signals to the gate driving circuit  103  and the source driving circuit  104 . 
         [0030]    The gate driving circuit  103  generates gate driving signals for driving the gate lines GL of the display unit  105  according to the control signals from the controller  102  and provides the gate driving signals to the display unit  105 . The source driving circuit  104  generates source driving signals for driving first source bus lines SB 1  and second source bus lines SB 2  of the display unit  105  according to the control signals from the controller  102  and provides the source driving signals to the display unit  105 . 
         [0031]    Please refer to  FIG. 2 , which depicts a diagram showing major components of the display unit  105 . The display unit  105  comprises a polarizing plate  111 , a bottom glass substrate  112 , pixel electrode portions  113 , gate lines GL, first source bus lines SB 1 , second source bus lines SB 2 , an alignment layer  114 , liquid crystals  115 , an alignment layer  116 , a common electrode  117  (common lines CL), a top glass substrate  118  and a polarizing plate  119 . The polarizing plate  111  is positioned under the bottom glass substrate  112  to allow a specific polarized light component of the light from the back light module to penetrate the bottom glass substrate  112 , for example. The gate lines GL, the first source bus lines SB 1 , the second source bus lines SB 2 , and the pixel electrode portions  113  are formed above the bottom glass substrate  112 . The gate lines GL are coupled with the gate driving circuit  103  shown in  FIG. 1  to receive the gate driving signals therefrom. 
         [0032]    The first source bus lines SB 1  and the second source bus lines SB 2  are aligned perpendicular to the gate lines GL. Meanwhile the first source bus lines SB 1  and the second source bus lines SB 2  are isolated from the gate lines GL and coupled with the source driving circuit  104 . Furthermore, the first source bus lines SB 1  and the second source bus lines SB 2  are arranged alternately. The pixel electrode portions  113  are located between the gate lines GL and also between the first, second source bus lines SB 1 , SB 2 . Meanwhile, the pixel electrode portions  113  are coupled with the gate lines GL and the first, second source bus lines SB 1 , SB 2 . The alignment layer  114  is formed above the gate lines GL, the first, second source bus lines SB 1 , SB 2  and the pixel electrode portions  113 . The alignment layer  114  is employed for forcing the liquid crystals  115  to align in a specific direction. The top glass substrate  118  is positioned above the alignment layer  114  with spacers (not shown) sandwiched therebetween. The common electrode  117  is positioned on the opposite surface of the top glass substrate  118  with respect to the surface toward the alignment layer  114 . The common electrode  117  is applied with a reference voltage, e.g. a GND voltage. 
         [0033]    The alignment layer  116  is formed on a surface (i.e. the bottom surface as shown in  FIG. 2 ) of the common electrode  117  and the common electrode  117  is attached to the top glass substrate  118 . The alignment layer  116  is employed for forcing the liquid crystals  115  to align in a specific direction. The aligning directions of the alignment layer  114  and the alignment layer  116  can be parallel or perpendicular to each other. Moreover, the polarizing plate  119  is positioned on the surface of the top glass substrate  118  with respect to the surface toward the liquid crystals  115 . The polarizing plate  119  allows a specific polarized light component of the light to penetrate the top glass substrate  118  therethrough. 
         [0034]    Then, please refer to  FIG. 3 , which depicts a block diagram of the source bus driving circuit  104 . The source bus driving circuit  104  comprises a voltage selecting circuit  211 , a multiplexer  212 , a voltage switching circuit  213 , a first high voltage source  214 , a second high voltage source  215 , a first low voltage source  216  and a second low voltage source  217 . Moreover, the voltage selecting circuit  211 , the first high voltage source  214 , the second high voltage source  215 , the first low voltage source  216  and the second low voltage source  217  constitute a holding voltage switching circuit for the gate voltage applied to the pixel driving transistor. 
         [0035]    The first high voltage source  214  generates a first high level voltage H 1 . The second high voltage source  215  generates a second high level voltage  112 . The first low voltage source  216  generates a first low level voltage L 1 . The second low voltage source generates a second low level voltage L 2 . The first high level voltage H 1 , the second high level voltage H 2 , the first low level voltage L 1 , and the second low level voltage L 2  respectively generated by the first high voltage source  214 , the second high voltage source  215 , the first low voltage source  216  and the second low voltage source  217  are provided to the voltage selecting circuit  211 . The magnitudes of the first high level voltage  111 , the second high level voltage H 2 , the first low level voltage L 1  and the second low level voltage L 2  are such that H 2 &gt;H 1 &gt;L 1 &gt;L 2 . 
         [0036]    The voltage selecting circuit  211  determines to output one of the first high level voltage and the second high level voltage as a first output voltage V 1 , and determines to output one of the first low level voltage and the second low level voltage as a second output voltage V 2 , according to a driving voltage level indicating signal high/low and a bus indicating signal posi/nega provided by the controller  102 . 
         [0037]    Please refer to  FIG. 4 , which depicts a circuit diagram of the voltage selecting circuit  211 . The voltage selecting circuit  211  comprises a first voltage level selecting unit  221 , a second voltage level selecting unit  222 , a third voltage level selecting unit  223  and a fourth voltage level selecting unit  224 . The first voltage level selecting unit  221  comprises transistors M 11 ˜M 14 . The first voltage level selecting unit  221  outputs one of the first high level voltage H 1  and the second high level voltage H 2 , as well as one of the first low level voltage L 1  and the second low level voltage L 2 , according to a driving voltage level indicating signal high/low provided by the controller  102 . The second voltage level selecting unit  222  comprises transistors M 21 ˜M 24 . The second voltage level selecting unit  222  outputs one of the second high level voltage  112  and the first high level voltage H 1 , as well as one of the second low level voltage L 2  and the first low level voltage L 1 , according to the driving level indicating signal high/low provided by the controller  102 . 
         [0038]    The third voltage level-selecting unit  223  comprises transistors M 15 ˜M 18 . The third voltage level selecting unit  223  outputs either the first high level voltage H 1  or the second high level voltage  112 , also either the first low level voltage L 1  or the second low level voltage L 2  selected by the first voltage level selecting unit  221  as the first output voltage V 1 , according to a bus indicating signal posi/nega provided by the controller  102 . The fourth voltage level-selecting unit  224  comprises transistor M 25 ˜M 28 . The fourth voltage level selecting unit  224  outputs either the second high level voltage H 2  or the first high level voltage H 1 , also either the second low level voltage L 2  or the first low level voltage L 1  selected by the second voltage level selecting unit  222  as the second output voltage V 2  according to the bus indicating signal posi/nega provided by the controller  102 . The first output voltage V 1  and the second output voltage V 2  outputted by the voltage selecting circuit  211  are provided to the voltage switching circuit  213 . The multiplexer  212  generates and provides the source voltages to the voltage switching circuit  213  according to the control signals provided by the controller  102 . 
         [0039]    The voltage switching circuit  213  comprises transistors Mg 1 , Mg 2  provided for each source bus line. The voltage switching circuit  213  provides one of the first output voltage V 1 , the second output voltage V 2  and the output voltage from the multiplexer  212  to the first source bus lines SB 1  and the second source bus lines SB 2 , according to the switching signals gate/source (source bus switching signal) from the controller  102 . The first source bus lines SB 1  and the second source bus lines SB 2  are coupled to the pixel electrode portions  113 . 
         [0040]    The following is an explanation about the pixel electrode portions  113  mentioned above. Each pixel electrode portion  113  comprises a pixel driving transistor Md, a gate voltage control transistor Ms, and an equivalent circuit of capacitors Clc, Cs, Ck. The source of the gate voltage control transistor Ms is coupled with the first source bus line SB 1  or the second source bus line SB 2 . The drain of the gate voltage control transistor Ms is coupled with the capacitor Ck, which is used for holding the gate voltage applied to the pixel driving transistor Md. The gate of the gate voltage control transistor Ms is coupled with the gate line GL. The gate voltage control transistor Ms is turned on so that the capacitor Ck can hold the gate driving voltage. 
         [0041]    The pixel driving transistor Md is a thin film transistor. The source of the pixel driving transistor Md is coupled with the first source bus line SB 1  or the second source bus line SB 2 . The drain of the pixel driving transistor Md is coupled with the capacitor Clc. The gate of pixel driving transistor Md is coupled to a connection point between the drain of the gate voltage control transistor Ms and the capacitor Ck, which is used for holding the gate voltage. The capacitor Clc is brought about by the liquid crystals  115  between the pixel electrode (not shown in figure) and common electrode  117 . Besides, the capacitor Cs is an auxiliary capacitor. The pixel electrode (not shown) can be a transparent electrode. The pixel driving transistor Md is turned on by the voltage held by the capacitor Ck, which is used for holding the gate voltage. Then, the current can be introduced from the first, second source bus lines SB 1 , SB 2  and applied to the pixel electrode (not shown). 
         [0042]    The following is an explanation about the source driving circuit  104 . Please refer to  FIG. 5 , which shows a block circuit diagram of the display device in an initial status according to an embodiment. The driving voltage level indicating signals high/low and the bus indicating signals posi/nega are at low level LL. The switching signals gate/source are at high level HH. The output voltage of the multiplexer  212  to the first source bus lines SB 1  is indicated as Vsn. The output voltage of the multiplexer  212  to the second source bus lines SB 2  is indicated as Vsp. 
         [0043]    When the driving voltage level indicating signals high/low and the bus indicating signals posi/nega are at a low level, the first output voltage V 1  of the voltage selecting circuit  211  becomes at the second low level voltage L 2 . The second output voltage V 2  of the voltage selecting circuit  211  becomes at the first low level voltage L 1 . Meanwhile, when the switching signals gate/source are at high level HH, the transistors Mg 1  are turned off and the transistors Mg 2  are turned on to provide the first output voltage V 1  to the first source bus lines SB 1  and provide the second output voltage V 2  to the second source bus lines SB 2 . Therefore, the second low level voltage L 2  is applied to the first source bus lines SB 1  and the first low level voltage L 1  is applied to the second source bus lines SB 2 . 
         [0044]    The gate voltage control transistor Ms and the pixel driving transistor Md of the pixel electrode portions  113  are turned off because the gate line GL becomes at low level. The voltage about the second low level voltage L 2  is applied to the capacitor Ck and the voltage about the source voltage Vsn is applied to the capacitors Clc, Ck. And then, the capacitor Ck holds the gate voltage. 
         [0045]    Please refer to  FIG. 6 , which shows a block circuit diagram of the display device when the gate voltage is held according to an embodiment. When the gate voltage is held by the capacitors Ck, both the driving voltage level indicating signals high/low and the bus indicating signals posi/nega change from low level LL to high level HH. Therefore, the first output voltage V 1  of the voltage selecting circuit  211  changes from the second low level voltage L 2  to the first high level voltage H 1 . The second output voltage V 2  changes from the first low level voltage L 1  to the second high level voltage H 2 . 
         [0046]    Therefore, the voltage level of the first source bus lines SB 1  are changed from the second low level voltage L 2  to the first high level voltage H 1 . The voltage level of the second source bus lines SB 2  are changed from the first low level voltage L 1  to the second high level voltage H 2 . 
         [0047]    Furthermore, the voltage levels of the gate lines are changed from the low level LL to high level HH. Accordingly, the gate voltage control transistors Ms are turned on. In the pixel electrode portions  113  which are coupled with the first source bus lines SB 1 , the capacitors Ck are held at the first high level voltage H 1 . In the pixel electrode portions  113  which are coupled with the second source bus lines SB 2 , the capacitors Ck are held at the second high level voltage H 2 . 
         [0048]    Next, the gate voltage control transistors Ms are turned off. Please refer to  FIG. 7 , which shows a block circuit diagram of the display device when the gates are turned off according to an embodiment. As shown in  FIG. 7 , the voltage levels of the gate lines GL are changed from high level HH to low level LL. When the gate lines GL become at low level LL, the gate voltage control transistors Ms are turned off. The capacitors Ck are disconnected from the first source bus lines SB 1  and the second source bus lines SB 2  and hold the first high level voltage H 1  and the second high level voltage H 2  respectively. With the output voltages of the multiplexer  212 , a write operation is executed to the capacitors Clc, Cs in the pixel electrode portions  113  which are coupled with the first source bus lines SB 1 . 
         [0049]      FIG. 8  to  FIG. 10  show block circuit diagrams of the display device executing the write operation according to an embodiment.  FIG. 8  shows the status of the display device when the output voltage of the multiplexer  212  to the first source bus lines SB 1  is changed from Vsn to Vsp.  FIG. 9  shows the status of the display device when the voltage levels of the switching signals gate/source change from high level HH to low level LL.  FIG. 10  shows status of the display device when the pixel driving transistors Md are turned on. 
         [0050]    Initially, for example, the output voltage of the multiplexer  212  to the first source bus lines SB 1  is changed from Vsn to Vsp as shown in  FIG. 8 . At that moment, the voltage levels of the switching signals gate/sources change from high level HH to low level LL as shown in  FIG. 9 , consequently, the transistors Mg 1  are turned on and the transistors Mg 2  are turned off. The output voltages of the multiplexer  212  are provided to the first source bus lines SB 1  and the second source bus lines SB 2 . The input voltages of the first source bus lines SB 1  and the second source bus lines SB 2  are changed from the first, second high level voltage H 1 , H 2  to the output voltages Vsn, Vsp from the multiplexer  212 . 
         [0051]    Because the input voltages of the first source bus lines SB 1  and the second source bus lines SB 2  are changed from the first, second high level voltage H 1 , H 2  to the output voltages Vsp, Vsn from the multiplexer  212  as aforementioned, the pixel driving transistors Md are turned on by the first, second high level voltage H 1 , H 2  held by the capacitors Ck. 
         [0052]    As shown in  FIG. 10 , the pixel driving transistors Md are turned on. The output voltages Vsp, Vsn from the multiplexer  212  are written into the capacitors Clc, Cs in the pixel electrode portions  113  which are coupled with the first source bus lines SB 1  and the second source bus lines SB 2 . The aforesaid operations are repeated to execute the write operations to the pixels. Then, the gate voltage control transistors Ms are turned on and the pixel driving transistors Md are turned off to finish the write operations to the pixels. 
         [0053]    Please refer to  FIG. 1 , which shows a block circuit diagram of the display device when the write operation is finished according to an embodiment. The controller  102  shown in  FIG. 3  changes the voltage levels of the gate lines GL from low level LL to high level HH. Therefore, the gate voltage control transistors Ms are turned on. The output voltages Vsp, Vsn from the multiplexer  212  are applied to the capacitors Ck through the first source bus lines SB 1  and the second source bus lines SB 2 . The gate voltages of the pixel driving transistors Md become the output voltages Vsp, Vsn from the multiplexer  212  and then are turned off. 
         [0054]    Moreover, the controller  102  changes the voltage levels of the driving level indicating signals high/low from high level HH to low level LL. Therefore, the first output voltage V 1  of the voltage selecting circuit  211  changes from the first high level voltage H 1  to the first low level voltage L 1 . The second output voltage V 2  changes from the second high level voltage H 2  to the second low level voltage L 2 . Then, the voltages applied to the capacitors Ck becomes at low level according to the output voltages determined by the voltage selecting circuit  211 . 
         [0055]    Please refer to  FIG. 12 , which shows a block circuit diagram of the display device when the voltages applied to the capacitors Ck becomes at low level according to an embodiment. The controller  102  shown in  FIG. 3  changes the voltage levels of the switching signals gate/source from low level LL to high level HH. Because the voltage levels of the switching signals gate/source are changed from low level LL to high level HH, the transistors Mg 1  are turned off and the transistors Mg 2  are turned on. The first output voltage V 1  of the voltage selecting circuit  211  is applied to the first source bus lines SB 1  and the second output voltage V 2  of the voltage selecting circuit  211  is applied to the second source bus lines SB 2 . At this moment, the first output voltage V 1  becomes the first low level voltage L 1  and the second output voltage V 2  becomes the second low level voltage L 2 . The first source bus lines SB 1  is applied with the first low level voltage L 1  and the second source bus lines SB 2  is applied with the second low level voltage L 2 . 
         [0056]    Meanwhile, the gate voltage control transistors Ms are turned on with the gate lines GL at high level. The capacitors Ck in the pixel electrode portions  113  which are coupled with the first source bus lines SB 1  become at the first low level voltage L 1 . The capacitors Ck in the pixel electrode portions  113  which are coupled with the second source bus lines SB 2  become at the second low level voltage L 2 . 
         [0057]    Next, the explanation about recovering the display device back to the initial status is presented. Please refer to  FIG. 13 , which shows a block circuit diagram of the display device recovered back to the initial status according to an embodiment. The controller  102  shown in  FIG. 3  changes the voltage levels of the gate lines GL from high level HH to low level LL. 
         [0058]    Because the voltage levels of the gate lines GL are changed from high level HH to low level LL, the gate voltage control transistors Ms are turned off and the display device is recovered back to the initial status therewith as shown in  FIG. 5 . Furthermore, a more detailed explanation of the aforesaid operations with a timing diagram is presented in the following. 
         [0059]    Please refer to  FIG. 14 , which shows a timing diagram of the write operation to the pixel according to an embodiment.  FIG. 14(A)  is a waveform of the driving voltage level indicating signal high/low.  FIG. 14(B)  is a waveform of the bus indicating signal posi/nega.  FIG. 14(C)  is a waveform of the first output voltage V 1  from the voltage selecting circuit  211 . 
         [0060]      FIG. 14(D)  is a waveform of the second output voltage V 2  from the voltage selecting circuit  211 .  FIG. 14(E)  is a waveform of the output voltage from the multiplexer  212 .  FIG. 14(F)  is a waveform of the switching signals gate/source.  FIG. 14(G)  is a waveform of the output voltage of the first source bus line SB 1 .  FIG. 14(H)  is a waveform of the gate lines GL.  FIG. 14(I)  is a waveform of the voltage Vk of the capacitor Ck.  FIG. 14(J)  is a waveform of an applied voltage Vlc to the capacitor Cle. 
         [0061]    At the moment t 1  and with the driving voltage level indicating signal high/low and the bus indicating signal posi/nega from the controller  102  shown in  FIG. 3 , the voltage levels of the gate lines are changed from low level LL to high level HH in the initial status. The first output voltage V 1  from the voltage selecting circuit  211  becomes the first high level voltage H 1 , and the second output voltage V 2  becomes the second high level voltage H 2 . Therefore, the first source bus lines SB 1  become at the first high level voltage H 1 . Besides, with the voltage levels of the gate lines GL changed to high level HH, the gate voltage control transistors Ms are turned on and the capacitors Ck are applied with the first high level voltage H 1 . 
         [0062]    At the moment t 2 , when the controller  102  changes the voltage levels of the gate lines GL to low level LL, the gate voltage control transistors Ms are turned off and the capacitors Ck are held with the first high level voltage H 1 . 
         [0063]    Then, at the moment t 3 , when the controller  102  changes the voltage levels of the switching signals gate/source to low level LL, the output voltage of the multiplexer  212  is changed from Vsn to Vsp and the voltage of the first source bus lines SB 1  becomes Vsp. Moreover, the pixel driving transistors Md are turned on and the capacitors Clc are applied with the voltage Vsp from the first source bus lines SB 1 . 
         [0064]    Then, at the moment t 4 , when the controller  102  changes the voltage levels of the driving voltage level indicating signals high/low to low level LL and the voltage levels of the gate lines GL to high level HH, the first output voltage V 1  from the voltage selecting circuit  211  becomes the second low level voltage L 2  and the second output voltage V 2  becomes the first low level voltage L 1 . Moreover, with the voltage levels of the gate lines GL changed to high level HH, the gate voltage control transistors Ms are turned on and the capacitors Ck are applied with the voltage Vsp. 
         [0065]    At the moment t 5 , when the controller  102  changes the voltage levels of the switching signals gate/source to high level HH, the first source bus lines SB 1  become at the first low level voltage L 1  and the capacitors Ck are applied with the first low level voltage L 1 . 
         [0066]    At the moment t 6 , when the controller  102  changes the voltage levels of the gate lines GL to low level LL, the gate voltage control transistors Ms are turned off and the capacitors Ck are held with the first low level voltage L 1  to recover the display device back to the initial status. 
         [0067]    As aforementioned, the gate voltages of the pixel driving transistors Md can be changed to the first, second high level voltages H 1 ,  112  and the first, second low level voltages L 1 , L 2  with the gate voltage control transistors Ms. Therefore, the alteration of the off-status currents of the pixel driving transistors Md between the first liquid crystal driving status and the second liquid crystal driving status can be diminished. 
         [0068]    Please refer to  FIG. 15 , which depicts waveforms of the operations to the pixel driving transistors Md.  FIG. 15(A)  shows waveforms of the first liquid crystal driving status and  FIG. 15(B)  shows waveforms of the second liquid crystal driving status. The solid lines represent gate voltages Vg, Vg′. The dotted lines represent source voltages Vs, Vs′. The one-dot chain lines represent drain voltages Vd, Vd′. The two-dot chain lines represent common voltage Vcom which is applied to the common electrode  117 . 
         [0069]    In the voltage selecting circuit  211  of this embodiment, the gate voltage Vg of the pixel driving transistor Md in the first liquid crystal driving status as shown in  FIG. 15(A) , is approximately + 10  V˜−7.5V. In the second liquid crystal driving status as shown in  FIG. 15(B) , the gate voltage Vg′ is approximately +15V˜−2.5V. Comparing the first liquid crystal driving status shown in  FIG. 15(A)  with the second liquid crystal driving status shown in  FIG. 15(B) , a voltage difference (2.3V) exists between the base voltage Vgl of the gate voltage Vg and the base voltage Vdl of the drain voltage Vd, and the voltage difference (2.5V) exists between the base voltage Vgl′ of the gate voltage Vg′ and the base voltage Vsl′ of the source voltage Vs′. The voltage difference between the first liquid crystal driving status and the second liquid crystal driving status can be diminished to be 0.2V approximately. Consequently, the off-status current in the second liquid crystal driving status can be decreased. Furthermore, the alteration of the off-status currents between the first liquid crystal driving status and the second liquid crystal driving status can be diminished and accordingly, the flicker phenomenon can be reduced. 
         [0070]    Moreover, the LCD apparatus  100  of the aforesaid embodiment can be utilized in computers, televisions or other electronic apparatus. The aforesaid electronic apparatus can be further utilized for electronic systems, such as, information process systems. 
         [0071]    As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative rather than limiting of the present invention. It is intended that they cover various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.

Technology Category: 3