# US 5,706,024 A · Driving circuit for liquid crystal display

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- Number: US 5,706,024 A
- Document ID: US5706024A
- Status: Granted
- Kind: A
- Application number: 08/510,234
- Filed: 1995-08-02
- Granted: 1998-01-06
- Earliest claimed: 1995-08-02
- Assignees: LG Semicon Co., Ltd.
- Inventors: Seung Woo Park
- Web page: https://patentgrep.com/patent/US5706024A

## CPC

- G09G 3/2011: {by amplitude modulation}
- G09G 3/3614: {Control of polarity reversal in general}
- G09G 3/3648: {using an active matrix (G09G3/367 - G09G3/3696 take precedence)}
- G09G 3/3688: {suitable for active matrices only}
- G09G 2310/027: Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
- G09G 2320/0204: Compensation of DC component across the pixels in flat panels
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

A circuit for driving a liquid crystal display including an inverted voltage supplying part for supplying additional inverted power to the liquid crystal display during inverted operation of the liquid crystal display.

## Claims

### Claim 1

A circuit for driving a liquid crystal display comprising:
mode driving means for supplying first polarity driving voltages to the liquid crystal display during a normal mode and supplying second polarity voltages opposite to the first polarity during an inverted mode; and
a supplemental voltage supplying circuit supplying supplemental inverted power to the liquid crystal display during the inverted mode to ensure substantial equivalence in magnitude between corresponding first polarity voltages and second polarity voltages applied across;
wherein the supplemental voltage supplying circuit includes,
an inversion control capacitor,
an inversion power source having a plus terminal thereof connected to the inversion control capacitor in series and a minus terminal thereof connected to ground,
a switch provided between the inversion control capacitor and the inversion power source for selectively supplying the inversion power to the liquid crystal display only during the inverted drive signal mode of the liquid crystal display, and
a switch connected in parallel with the inversion control capacitor for being turned on only at normal operation of the liquid crystal panel for equalizing voltage at both ends of the inversion control capacitor.

### Claim 2 (depends on 1)

The circuit as in claim 1, wherein a common mode voltage on the liquid crystal display is held at a constant value.

### Claim 3 (depends on 2)

The circuit as in claim 2, wherein the common mode voltage is held at five volts.

### Claim 4 (depends on 1)

The circuit as in claim 1, wherein the mode driving means includes:
switch block means, having three outputs, for selectively applying two input voltages V1 and V2 to the three outputs according to a plurality of switch block control signals; and
amplification means for amplifying a combined signal of the three outputs of the switch block means and supplying the amplified combination to the liquid crystal display.