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1. A driving circuit for an LCD system, the LCD system comprising a common electrode, a display electrode, and a coupling capacitor, the driving circuit comprising:
a DC voltage supply unit, coupled to the common electrode, for supplying a DC voltage to the common electrode; an image driving unit, coupled to the display electrode, for providing an image driving signal to the display electrode; an AC voltage output terminal coupled to the common electrode via the coupling capacitor; a charging/discharging switch; a charging/discharging unit coupled to the AC voltage output terminal via the charging/discharging switch, when the charging/discharging switch is turned on, the charging/discharging unit charging or discharging the AC voltage output terminal; a charge sharing switch coupled between the display electrode and the AC voltage output terminal, when the charge sharing switch is turned on, the display electrode and the AC voltage output terminal being electrically coupled to each other; and a control unit, coupled to the charging/discharging switch and the charge sharing switch, for respectively controlling the charging/discharging switch and the charge sharing switch based on a requirement to change the electrical polarity of the common electrode, wherein when the voltage of the AC voltage output terminal is required to be raised from low to high, the control unit can first turn on the charge sharing switch to transfer a charge of the display electrode into the AC voltage output terminal and preliminarily pull high the voltage of the AC voltage output terminal to a first voltage level, the control unit secondly turns off the charge sharing switch and turns on the charging/discharging switch to charge the AC voltage output terminal to pull high the voltage of the AC voltage output terminal to a second voltage level, and the control unit thirdly controls the charge sharing switch and the charging/discharging switch to charge the AC voltage output terminal to pull high the voltage of the AC voltage output terminal to a third voltage level, wherein at the same time, the control unit pulls a voltage provided from the image driving unit to the display electrode from a fourth voltage level down to a fifth voltage level; wherein the third voltage level is larger than the second voltage level, the second voltage level is larger than the first voltage level, the fourth voltage level is between the second voltage level and the third voltage level, and the fifth voltage level is between 0 and the first voltage level. |
