1.  Field of Invention
The present invention relates to a source driver and a driving method thereof, and more particularly, to a source driver that includes an output buffer charging a display panel in a phased manner for reducing power consumption. 
2.  Description of the Related Art
FIG.  1 is a block diagram of a conventional source driver 110 and a display panel 140.  Referring to FIG.  1, the source driver 110 includes a plurality of driving channels 120.  Each of the driving channels 120 includes a latch 122, a digital-to-analog converter (DAC) 124, an output buffer 126, and an output switch 128.  Video data on the data bus is sequentially input into the driving channels 120 in response to a control signal CON provided by a timing controller (not shown).  The source driver 110 converts the digital video data into analog driving signal through the DAC 124, and transmits the driving signal to the output buffer 126.  The output buffer 126 further enhances the driving signal and passes the driving signals to the display panel 140 through the conducted output switch 128 for driving pixels on the display panel 140. 
Generally, in the driving system of the LCD, a polarity of the driving signal delivered to a certain pixel must be periodically converted for avoiding a residual image phenomenon caused by liquid crystal polarization.  There are three types of polarity inversion for driving the display panel, i.e. frame inversion, column inversion, and dot inversion.  Taking the dot inversion as an example, the adjacent pixels in one frame are driven by the driving signals with opposite polarities, and the pixels in the same location of two continuous frames are also driven by the driving voltages with opposite polarities.  Since the driving signal with opposite polarities have different voltage levels, the voltage swing of the output buffer 126 causes large power consumption so the output buffer 126 contributes a large percentage of power consumption to the source driver 120.  Therefore, how to solve this problem becomes an important issue to be researched and discussed.