# US 8,570,269 B2 · Lamp driving apparatus for liquid crystal display device having high contrast ratio

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- Number: US 8,570,269 B2
- Document ID: US8570269B2
- Status: Granted
- Kind: B2
- Application number: 12/003,628
- Filed: 2007-12-28
- Published: 2008-10-02
- Granted: 2013-10-29
- Earliest claimed: 2007-04-02
- Assignees: LG Display Co., Ltd.
- Applicants: Hyeon-Seung Kim; Jong-Ho Lim
- Inventors: Hyeon-Seung Kim; Jong-Ho Lim
- Web page: https://patentgrep.com/patent/US8570269B2

## CPC

- G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines}
- G09G 3/2014: {by modulation of the duration of a single pulse during which the logic level remains constant}
- G09G 2310/024: Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
- G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other
- G09G 2320/066: for control of contrast
- 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

Disclosed is a technology for implementing a high contrast ratio that cannot be implemented by only an analog dimming or burst dimming method, by selectively turning off lamps on the LCD device, comprising: a control unit outputting control signals and video data for controlling a driving of a gate driving unit and a data driving unit, and brightness control signals; the gate driving unit for supplying scan signals to gate lines on a liquid crystal panel by controlling of the control unit and the data driving unit for supplying a data voltage to data lines; the liquid crystal panel having liquid crystal cells arranged in a matrix type and thin film transistors formed at each intersection between the data lines and the gate lines; a backlight driving unit for controlling an optical amount by controlling a tube current supplied to lamps on a backlight unit and for selectively turning off the lamps when the brightness control signals are inputted; and the backlight unit for implementing a high brightness with respect to a dark area by irradiating a backlight having a brightness corresponding to light from the lamps emitted by the backlight driving unit toward the liquid crystal panel, and turning off some of the lamps.

## Claims

### Claim 1

A lamp driving apparatus for an LCD device, comprising:
a control unit configured to output control signals and video data to control a driving of a gate driving unit and a data driving unit, and brightness control signals;
the gate driving unit configured to supply scan signals to gate lines on a liquid crystal panel by controlling the control unit and the data driving unit for supplying a data voltage to data lines;
the liquid crystal panel comprising:
liquid crystal cells arranged in a matrix type; and
thin film transistors formed at each intersection between the data lines and the gate lines; and
a backlight driving unit configured to:
control an optical amount by controlling a tube current supplied to a plurality of lamps on a backlight unit; and
selectively turn off some lamps of the plurality of lamps in response to the brightness control signals being inputted,
wherein the backlight unit is configured to implement a lower brightness backlight output in a dark image area by irradiating a backlight comprising a brightness corresponding to light from the lamps emitted by the backlight driving unit toward the liquid crystal panel, and turning off some of the lamps,
wherein the backlight driving unit includes:
a pulse width modulation integrated circuit outputting switching control signals for switching a switching device inside of an inverter integrated circuit, the inverter integrated circuit converting a power source voltage supplied from a power source into an alternating voltage by using the switching device switched by the switching control signals to supply the alternating voltage to a transformer, the transformer outputting the alternating voltage outputted from the inverter integrated circuit by converting into a high alternating voltage corresponding to a winding ratio, and
a turn-off lamp selection unit configured to:
selectively transfer the high alternating voltage outputted from the transformer to the lamps on the backlight unit, and
pass through the outputted high alternating voltage from the transformer to selected lamps, in response to the brightness control signals being inputted, such that the selected lamps can be turned on, and
wherein the turn-off lamp selection unit comprises a plurality of switching devices such that all of the lamps are turned on in response to the brightness control signals comprising a non-specific value is inputted and some of the lamps are selectively turned on when the brightness control signals comprising a specific value is inputted.

### Claim 2 (depends on 1)

The lamp driving apparatus of claim 1, wherein the turn-off lamp selection unit is provided with a plurality of switching devices to selectively transfer the high alternating voltage.

### Claim 3 (depends on 1)

The lamp driving apparatus of claim 1, wherein the backlight driving unit is further configured to turn off the lamps by selecting some lamps per unit number.

### Claim 4 (depends on 1)

The lamp driving apparatus of claim 1, wherein the backlight driving unit is further configured to turn off the lamps in a selected area by dividing all the lamps into some areas.

### Claim 5 (depends on 1)

The lamp driving apparatus of claim 1, wherein the backlight driving unit is further configured to control a tube current supplied to lamps in an analog dimming method or a burst dimming method.

### Claim 6 (depends on 1)

The lamp driving apparatus of claim 1, wherein the backlight driving unit is further configured to drive the lamps in a scanning method or a non-scanning method.