US 8,797,253 B2Granted

Liquid crystal display device

AssigneeSharp Kabushiki Kaisha

InventorsKohji Iwasaki, Motoyuki Oniki

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Abstract

In an LCD device, picture quality luminance is controlled through the combination of pulse-width modulation (PWM) system and current value control system, reducing the electrical power consumption associated with turning on an LED. In the LED backlight, the light emitting luminance of the LED is controlled by both PWM and also by current value control, which selects the value of the current supplied to the LED from a plurality of set values. At least one of the plurality of set values is a predetermined current value at which duty reaches a maximum value at the maximum luminance value used in a specified picture quality mode of the picture quality modes established in the liquid crystal display device. In the aforementioned specified picture quality mode, the greatest luminance value to be used is smaller than at least the greatest luminance value used in other specified picture quality modes.

Claims6

Dependent claims

A liquid crystal display device having a liquid crystal panel for displaying an input video signal, a light source of a light-emitting diode for irradiating the liquid crystal panel, and a light emission luminance control circuit for controlling light emission luminance of the light-emitting diode, wherein,

the light emission luminance control circuit controls the light emission luminance of the light-emitting diode with both a Pulse Width Modulation system in which duty indicating a lighting time per cycle in a pulse to turn on/off the light-emitting diode is changed, and a current value control system in which a value of a current to be flowed to the light-emitting diode is selected from among a plurality of setting values,
the light emission luminance control circuit receiving a mode switching signal and a light modulation control signal, wherein the mode switching signal indicates an eco mode and a plurality of quality modes including a first quality mode and a second quality mode,
the Pulse Width Modulation system adjusting the duty according to the light modulation control signal, the quality mode and the eco mode,
the current value control system selecting the current value according to the light modulation control signal, the quality mode and the eco mode.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 13/382,857Filed 6 Jul 2010
Priority: JP 2009-1607807 Jul 2009
Published: US 2012/0105515 A13 May 2012
Granted: 5 Aug 2014
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G09G 3/3406
By control of light from an independent source: control of illumination source
G02F 1/133613
Direct backlight: characterized by the sequence of light sources
G09G 2320/0633
For control of overall brightness: by amplitude modulation of the brightness of the illumination source
G09G 2320/064
For control of overall brightness: by time modulation of the brightness of the illumination source