Lg Philips Lcd Co., Inc.

Jin Sang Kim

Ju Cheon Yeo

Sang Young Yoon

In a shift register for driving a pixel row in a liquid crystal display device a plurality of stages are connected: to a high level voltage source, a low level voltage source and a phase-delayed clock signal generator; to row lines; and in cascade, with respect to a scanning signal, for charging and discharging the row lines. Each stage of the shift register has a pull-up transistor, a pull-down transistor, and first to fourth transistors. The pull-up transistor has a control electrode and a conduction path connected between the first clock signal line and the output terminal. The pull-down transistor has a control electrode and a conduction path connected between the low level voltage line and the output terminal. The first and second transistors have conduction paths connected in series between the input terminal and the control electrode of the pull-up transistor, and each has a control electrode connected commonly to the second clock signal line. The first and second transistors allow a voltage to be charged on the control electrode of the pull-up transistor. The third and fourth transistors have conduction paths connected in series between the third clock signal line and the control electrode of the pull-down transistor, and each has a control electrode connected commonly to the third clock signal line. The third and fourth transistors allow a voltage to be charged on the control electrode of the pull-down transistor.

Shift register

A shift register for driving a pixel array is adapted to prevent a defect due to a short of a capacitor. In each stage of the shift register, an output circuit is provided with a pull-up transistor having a first input electrode for receiving a first clock signal, a first output electrode connected to a row line and a first control electrode, and a pull-down transistor having a second input electrode connected to a low-level voltage source, a second output electrode connected to the row line and a second control electrode. An input circuit generates a first control signal to be applied to the first control electrode and a second control signal to be applied to the second control electrode in response to a second clock signal having a phase different from the first clock signal. A first capacitor is connected between the input circuit and the row line, a second capacitor is connected between the second control electrode and the low-level voltage source, and a third capacitor is connected between the first control electrode and the low-level voltage source. At least one of the first to third capacitors has associated therewith a second capacitor connected in series thereto.

A shift register that is suitable for reducing the required number of clock signals as well as simplifying the configuration of an external control circuit uses a plurality of stages connected, in series, to a start pulse input line. In each stage, an output circuit responds to a first control signal to apply any one of first and second clock signals to a row line of a liquid crystal cell array and thus to charge the low line of the liquid crystal cell array, and responds to a second control signal to discharge a voltage at the row line. An output circuit responds to a clock signal different from any one of the start pulse and an output signal of the previous stage to generate the first control signal, and responds to a clock signal different from the first control signal to generate the second control signal.

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Anyang-shi, South Korea

Jin Sang Kim