Abstract:
An apparatus for driving a display panel includes an output terminal for outputting driving voltages to the display panel, a source driver for intermittently outputting data voltages to the driving voltage output terminal and at least one charge sharing branch connected to the driving voltage output terminal. Each of the at least one charge sharing branch includes a charge sharing capacitor and a charge sharing switch connected in series between the driving voltage output terminal and ground, enabling the accumulation and supply to the display of the necessary reverse driving voltages, from a single intermittent source driver instead of from two independently-powered opposite polarity sources.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to display panel driving technologies, and more particularly, to an apparatus for driving a display panel, and a display device using the apparatus. 
         [0003]    2. Description of Related Art 
         [0004]    Liquid crystal displays (LCDs) utilize liquid crystal molecules to control light transmissivity of pixel units, where the liquid crystal molecules in a pixel unit tilt to a corresponding angle in accordance with a driving voltage applied to the pixel unit. The driving voltage is normally provided by a source driver. 
         [0005]    In order to protect the liquid crystal molecules from decay or damage, a typical LCD may employ a polarity inversion driving method. In the polarity inversion driving method, each pixel unit is provided with a positive driving voltage in a frame period, and in a next frame period, the driving voltage provided to the pixel unit is changed to be negative. In other words, the polarity inversion driving method requires the source driver to output driving voltages having two different polarities in two consecutive frame periods. This causes power consumption of the typical LCD to increase. 
         [0006]    What is needed is a means that can overcome the above-described limitations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of at least one embodiment. In the drawings, like reference numerals designate corresponding parts throughout the various views, and all the views are schematic. 
           [0008]      FIG. 1  is a block diagram of a display device according to one embodiment of the present disclosure. 
           [0009]      FIG. 2  shows driving periods of the display device of  FIG. 1 . 
           [0010]      FIG. 3  is a block diagram of a display device according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Reference will be made to the drawings to describe certain exemplary embodiments of the present disclosure. 
         [0012]      FIG. 1  is a block diagram of a display device according to one embodiment of the present disclosure. The display device includes a display panel  200  and an apparatus  800  for driving the display panel  200 . The display panel  200  may be a flat panel such as an LCD panel. 
         [0013]    The apparatus  800  includes a source driver  100 , a control switch  30 , a plurality of charge sharing capacitors C1, C2, C3, . . . , C(n−1), a plurality of charge sharing switches sw1, sw2, sw3, . . . , sw(n−1), and a driving voltage output terminal  10 . The output terminal  10  is electrically connected to the display panel  200 , and outputs driving voltages to the display panel  200 . 
         [0014]    The source driver  100  includes a data voltage output terminal  20  for outputting data voltages. The control switch  30  is connected between the data voltage output terminal  20  and the driving voltage output terminal  10 . Each of the charge sharing capacitors C1, C2, C3, . . . , C(n−1) corresponds to a charge sharing switch sw1, sw2, sw3, . . . , sw(n−1), and in this embodiment, each one of the charge sharing capacitors C1, C2, C3, . . . , C(n−1) and the corresponding charge sharing switch sw1, sw2, sw3, . . . , sw(n−1) is connected in series between the driving voltage output terminal  10  and ground, and cooperatively form a charge sharing branch. Accordingly, a plurality of charge sharing branches are connected in parallel and formed in the apparatus  800 . 
         [0015]    Referring to  FIG. 2 , in each driving period for the display panel, the source driver  100  may first output, via the data voltage output terminal  20 , data voltages V1, V2, V3, . . . , V(n−1), Vn in respective time periods T1, T2, T3, . . . , T(n−1), Tn, and then secondly output data voltages V(n−1), V(n−2), V(n−3), . . . , V2, V1 in respective time periods T(n+1), T(n+2), T(n+3), . . . , T(2n-1). In this embodiment, the data voltages V1 to Vn decrease gradually, for example, the data voltages V1 to Vn may be 30V, 25V, 15V, . . . , 0V. The time periods T1 to T(2n−1) are non-consecutive time periods, and these non-consecutive time periods are defined as data voltage outputting periods T1 to T(2n−1) in the present disclosure. Moreover, since the data voltage outputting periods T1 to T(2n−1) are non-consecutive, a plurality of time periods in which no data voltage is being output from the source driver  100  alternates in time with the data voltage outputting periods T1 to T(2n−1). These time periods of zero voltage output (or no data voltage output) are defined as charge sharing periods in the present disclosure. 
         [0016]    At the data voltage outputting periods T1 to T(2n−1), the control switch  30  is switched on under the control of an external control signal. Thus, the data voltages V1, V2, V3, . . . , V(n−1), Vn, V(n−1), V(n−2), V(n−3) . . . , V2, V1, which are output by the source driver  100 , are transmitted to the driving voltage output terminal  10  and then output to the display panel  200  for the duration of the data voltage outputting periods T1 to T(2n−1). At the charge sharing periods, the control switch  30  is switched off and the charge sharing switches sw1 to sw(n−1) are switched on in sequence under the control of the external control signal, such that the charge sharing capacitors C1 to C(n−1) feed their charges in turn to the display panel  200 . 
         [0017]    Specifically, at a first data voltage output period T1, the control switch  30  is switched on, and the first data voltage V1 provided by the source driver  100  is output to the display panel  200 ; after period T1, at a first charge sharing period between T1 and T2, the first charge sharing switch sw1 is switched on, and thus the first charge sharing capacitor C1 feeds the charge therein to the display panel  200 ; at a second data voltage output period T2, the control switch  30  is switched on again, and the second data voltage V2 provided by the source driver  100  is output to the display panel; at a second charge sharing period between T2 and T3, the second charge sharing switch sw2 is switched on, and the second charge sharing capacitor C2 feeds the charge therein to the display panel  200 ; the operation of the apparatus  800  repeats and cycles in the above-mentioned manner, and at a (2n−1)th data voltage outputting period T(2n−1), the control switch  30  is switched on, and the source driver  100  re-outputs the first data voltage V1 to the display panel  200 . 
         [0018]    In the display device according to the present disclosure, because the charge sharing capacitors C1, C2, C3, . . . , C(n−1) can share their charges with the display panel  200  during the charge sharing periods, the source driver  100  merely needs to output the data voltages discontinuously, during the data voltage outputting periods. As such, the power consumption of the source driver  100  is significantly reduced. 
         [0019]    Furthermore, in the display device according to the present disclosure, the number of the charge sharing branches may be designed as needed. In one embodiment, the apparatus  800  may only include one charge sharing branch, i.e., n=2, and thus a single capacitor C1 and a single second control switch sw1 are included in the apparatus  800 . Accordingly, the first control switch  30  and the second control switch sw1 are alternately switched on. 
         [0020]    In another embodiment, the apparatus  800  may include two charge sharing branches, i.e., n=3, thus a first charge sharing branch (including a first charge sharing capacitor C1 and a first charge sharing switch sw1) and a second charge sharing branch (including a second charge sharing capacitor C2 and a second charge sharing switch sw2) are connected between the driving voltage output terminal  10  and the ground. Assuming the source driver  100  outputs sequential data voltages 30V, 15V, 0V, 15V, 30V during the respective data voltage output periods T1, T2, T3, T4, T5, and capacitance of each of the first and second charge sharing capacitors C1, C2 is substantially equal to an equivalent capacitance of the display panel  200 , it can be calculated that the first and second charge sharing capacitors C1, C2 reach their saturation voltages after thirteen driving periods, and the power consumption of the source driver  100  will be reduced by 33.3% from the 14th driving period onwards. Alternatively, for the same function of the source driver  100 , but the capacitance of each of the first and second charge sharing capacitors C1, C2 is about five times the equivalent capacitance of the display panel  200 , it can be calculated that the first and second charge sharing capacitors C1, C2 reach their saturation voltages after forty driving periods, and the power consumption of the source driver  100  will be reduced by 45.3% from the 41th driving period onwards. 
         [0021]    Referring to  FIG. 3 , a block diagram of a display device according to another embodiment of the present disclosure is shown. The display device as illustrated in  FIG. 2  is similar to the above-described display device as illustrated in  FIG. 1 ; however, in the display device as illustrated in  FIG. 3 , the data voltage output terminal  20  of a source driver  100  of the driving apparatus  900  is connected to an output terminal  10  with no control switch, for driving a display panel  200 , and the source driver  100  further includes a control terminal  22 . The control terminal  22  is configured to receive a control signal. The control signal controls the data voltage data output terminal  20  to be in a high-impedance state in the charge sharing periods, so as to enable the charge sharing capacitors C1 to C(n−1) to feed the charge therein to the display panel  200 , and to control the data voltage data output terminal  20  to be in a low-impedance state in the data voltage outputting periods, so that the data voltages provided by the source driver  100  can still be output to the display panel  200 . 
         [0022]    It is to be further understood that even though numerous characteristics and advantages of preferred and exemplary embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and changes may be made in detail, especially in the matters of shape, size and arrangement of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.