Liquid crystal display device and method of controlling the same

Patent metadata

Field	Value
Publication number	US-2020004084-A1
Application number	US-201916449226-A
Country	US
Kind code	A1
Filing date	Jun 21, 2019
Priority date	Jun 29, 2018
Publication date	Jan 2, 2020
Grant date	—

Abstract

A liquid crystal display device including a display unit, a backlight including a plurality of light sources, an LED control circuit configured to output a PWM signal (LED control signal) based on a display synchronization signal, such that the light sources are intermittently lighted, and an LED driver configured to control a drive current that is supplied to the light sources, based on the PWM signal, is provided with a monitoring control unit that is configured to perform monitoring at least one of the PWM signal, the drive current, and the display synchronization signal, as a monitoring target. When an abnormality of the monitoring target is detected, the monitoring control unit controls a waveform of the PWM signal such that the drive current that is supplied to the light sources in the backlight becomes zero.

First claim

What is claimed is:

1 . A liquid crystal display device comprising:
a display unit configured to display an image; a light source configured to radiate light on the display unit; a light source control unit configured to output a PWM signal with a constant duty ratio based on a display synchronization signal, such that the light source is intermittently lighted; a light source drive unit configured to control a drive current that is supplied to the light source, based on the PWM signal outputted from the light source control unit; and a monitoring control unit configured to monitor at least one of the PWM signal, the drive current, and the display synchronization signal, as a monitoring target, and control, when an abnormality of the monitoring target is detected, a waveform of the PWM signal such that the drive current that is supplied to the light source becomes zero.

2 . The liquid crystal display device according to claim 1 , further comprising a display drive unit configured to drive the display unit based on an image signal and the display synchronization signal, wherein
the light source control unit is provided in the display drive unit.

3 . The liquid crystal display device according to claim 2 , further comprising a host configured to supply the image signal and the display synchronization signal to the display drive unit.

4 . The liquid crystal display device according to claim 3 , wherein the monitoring control unit is provided in the host.

5 . The liquid crystal display device according to claim 4 , wherein the monitoring control unit initializes the display drive unit and the light source drive unit when an abnormality of the monitoring target is detected.

6 . The liquid crystal display device according to claim 3 , wherein the monitoring control unit is provided in the display drive unit.

7 . The liquid crystal display device according to claim 6 , wherein the monitoring control unit initializes the display drive unit, the light source drive unit, and the host when an abnormality of the monitoring target is detected.

8 . The liquid crystal display device according to claim 3 , wherein the monitoring control unit is provided in the light source drive unit.

9 . The liquid crystal display device according to claim 8 , wherein the monitoring control unit initializes the display drive unit, the light source drive unit, and the host when an abnormality of the monitoring target is detected.

10 . The liquid crystal display device according to claim 2 , wherein the monitoring control unit initializes the display drive unit and the light source drive unit when an abnormality of the monitoring target is detected.

11 . The liquid crystal display device according to claim 1 , wherein the monitoring control unit takes the PWM signal as the monitoring target, and determines that an abnormality is caused in the monitoring target when an on period of the PWM signal becomes longer than a predetermined period.

12 . The liquid crystal display device according to claim 1 , wherein the monitoring control unit takes the drive current as the monitoring target, and determines that an abnormality is caused in the monitoring target when a state where magnitude of the drive current is equal to or greater than predetermined magnitude continues for longer than a predetermined period.

13 . A control method of a liquid crystal display device including a display unit configured to display an image, a light source configured to radiate light on the display unit, a light source control unit configured to output a PWM signal with a constant duty ratio based on a display synchronization signal, such that the light source is intermittently lighted, and a light source drive unit configured to control a drive current that is supplied to the light source, based on the PWM signal outputted from the light source control unit, the control method comprising the steps of:
monitor at least one of the PWM signal, the drive current, and the display synchronization signal, as a monitoring target; and controlling, when an abnormality of the monitoring target is detected, a waveform of the PWM signal such that the drive current that is supplied to the light source becomes zero.

Assignees

• Sharp Kk

Inventors

• Nishihara Yasutomo
• Tohdoh Hideo
• Ohhara Kohichi
• Handa Takuya
• MICHIBAYASHI Kohji

Classifications

• G09G3/3406 Primary

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• G09G2320/0646

  Modulation of illumination source brightness and image signal correlated to each other · CPC title

• G09G2330/12

  Test circuits or failure detection circuits included in a display system, as permanent part thereof · CPC title

• G09G3/006

  Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays (testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309) · CPC title

• G09G2320/064

  by time modulation of the brightness of the illumination source · CPC title