Patent ID: 8125478

Claim:
A switching voltage controlling circuit that is adapted to a liquid crystal display (LCD), the LCD comprising a display panel and a plurality of gate drivers, the display panel comprising a plurality of pixel units, the switching voltage controlling circuit comprising: a current-controlled switch, having a first terminal and a second terminal, the first terminal being coupled to a constant voltage; a transmission line, having a first terminal and a second terminal, the first terminal being coupled to the second terminal of the current-controlled switch, the transmission line being serially coupled to the gate drivers, wherein the gate drivers generate a switching voltage according to a voltage provided by the transmission line and control the pixel units; and a feedback circuit, coupled to the transmission line and the current-controlled switch, the feedback circuit regulating an amount of a current passing through the current-controlled switch according to a voltage difference between the first terminal and the second terminal of the transmission line, wherein the feedback circuit comprises: a first amplifier, a first input terminal and a second input terminal of the first amplifier being coupled to the first terminal and the second terminal of the transmission line, respectively; a first voltage dividing resistor, a first terminal of the first voltage dividing resistor being coupled to an output terminal of the first amplifier; a second voltage dividing resistor, a first terminal and a second terminal of the second voltage dividing resistor being coupled to a second terminal of the first voltage dividing resistor and a first voltage, respectively; and a second amplifier, a first input terminal and a second input terminal of the second amplifier being coupled to the second terminal of the first voltage dividing resistor and a second voltage, an output terminal of the second amplifier outputting a control voltage for regulating the amount of the current passing through the current-controlled switch.