Driving IC of liquid crystal display

• US 8,243,000 B2
• Filed: 06/14/2004
• Issued: 08/14/2012
• Est. Priority Date: 06/20/2003
• Status: Active Grant

• Current Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Original Assignee: LG Display Co., Ltd.
• Inventors: Lim, Kyoung Moon
• Primary Examiner(s): Dinh, Duc
• Application Number:
  US10/865,809
• Publication Number:
  US 20050093809A1
• Time in Patent Office: 2,983 Days
• Field of Search: 345/204, 345/690, 345/87, 345/89, 345/98, 345/99, 345/100
• US Class Current: 345/98
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A data driver IC of a liquid crystal display is provided. The data driver IC includes a latch circuit latching digital pixel data, a digital-to-analog converter converting an output of the latch circuit into an analog video signal, and an analog amplifier amplifying the analog video signal converted in the digital-to-analog converter. The analog amplifier includes a NAND gate, a capacitor connected to an input terminal of the NAND gate, and a switch for connecting the input terminal and an output terminal of the NAND gate.

Claims

1. A data driver IC for a liquid crystal display, comprising:

a latch circuit latching digital data;

a digital-to-analog converter converting an output of the latch circuit into an analog video signal; and

a plurality of analog amplifiers amplifying the analog video signal converted in the digital-to-analog converter,

wherein the analog amplifiers are cascade-connected to each other,

wherein each of the analog amplifiers comprises;

a NAND gate formed of a polysilicon and having two input terminals that are connected to each other, such that the same analog video signal is input on both of the terminals;

a capacitor connected to any one of the input terminals of the NAND gate; and

a switch connecting the two input terminals and an output terminal of the NAND gate, such that an output signal from the NAND gate is fed back to both of the two input terminals through an operation of the switch,

wherein when the switch is closed to initialize the input and the output terminals of the NAND gate to an intermediate potential of a power supply voltage that is applied to the NAND gate, an initialized voltage is stored in the capacitor, and then a voltage corresponding to a difference between a voltage of an analog video signal supplied to the capacitor and the initialized voltage is output to a data line through the output terminal,

wherein the output signal is an amplified value of the analog video signal that is converted in the digital-to analog converter and is stabilized to a RC delay of the data line, and

wherein the output signal is monitored and fed back to the analog video signal that is converted in the digital-to analog converter.

2. The data driver IC according to claim 1, wherein the latch circuit comprises:

a data latch latching external digital data;

a shift register sequentially generating latch enable signals with respect to the digital data in synchronization with an external clock signal; and

a line latch sequentially storing the digital data that are input in synchronization with the latch enable signal.

3. A data driver IC for a liquid crystal display, comprising:

a latch circuit latching digital data;

a digital-to-analog converter converting an output of the latch circuit into an analog video signal; and

a plurality of analog amplifiers amplifying the analog video signal converted in the digital-to-analog converter,

wherein the analog amplifiers are cascade-connected to each other,

wherein each of the analog amplifiers comprises;

a NOR gate formed of a polysilicon and having two input terminals that are connected to each other, such that the same analog video signal is input on both of the terminals;

a capacitor connected to any one of the input terminals of the NOR gate; and

a switch connecting the input terminals and an output terminal of the NOR gate, such that an output signal from the NOR gate is fed back to both of the two input terminals through an operation of the switch,

wherein when the switch is closed to initialize the input and the output terminals of the NOR gate to an intermediate potential of a power supply voltage that is applied to the NOR gate, an initialized voltage is stored in the capacitor, and then a voltage corresponding to a difference between a voltage of an analog video signal supplied to the capacitor and the initialized voltage is output through the output terminal,

wherein the output signal is an amplified value of the analog video signal that is converted in the digital-to analog converter and is stabilized to a RC delay of the data line, and

wherein the output signal is monitored and fed back to the analog video signal that is converted in the digital-to analog converter.

4. The data driver IC according to claim 3, wherein the latch circuit comprises:

a data latch latching external digital data;

a shift register sequentially generating latch enable signals with respect to the digital data in synchronization with an external clock signal; and

a line latch sequentially storing the digital data that are input in synchronization with the latch enable signal.

5. A data driver IC for a liquid crystal display, comprising:

a latch circuit latching digital data;

a digital-to-analog converter converting an output of the latch circuit into an analog video signal; and

an analog amplifier amplifying the analog video signal converted in the digital-to-analog converter,

wherein the analog amplifier comprises;

a NAND gate having two input terminals, the analog video signal is supplied to a first input terminal and a control signal is supplied to a second input terminal;

a capacitor connected to the first input terminal of the NAND gate; and

a switch connecting the first input terminal and an output terminal of the NAND gate,

wherein the control signal is a signal for locking the analog video signal to a black state depending on an upper bit state of the analog video signal, a multi-color mode selection function or a screen mask,

wherein when the switch is closed to initialize the first input and the output terminals of the NAND gate to an intermediate potential of a power supply voltage that is applied to the NAND gate, an initialized voltage is stored in the capacitor, and then a voltage corresponding to a difference between a voltage of an analog video signal supplied to the capacitor and the initialized voltage is output to a data line through the switch,

wherein the difference voltage is an amplified value of the analog video signal that is converted in the digital-to analog converter, and

wherein the difference voltage output to the data line is monitored and fed back to the analog video signal that is converted in the digital-to analog converter to control the difference voltage,

wherein in a case when the control signal has a logic low level by a user an output state is locked.