Liquid crystal backlight device and method for controlling the same

• US 8,279,159 B2
• Filed: 12/13/2005
• Issued: 10/02/2012
• Est. Priority Date: 09/09/2005
• Status: Active Grant

• Current Assignee: China Star Optoelectronics International (HK) Limited (TCL Technology Group Corp.)
• Original Assignee: China Star Optoelectronics International (HK) Limited (TCL Technology Group Corp.)
• Inventors: Huang, Jih-Fon
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): DAVIS, TONY O
• Application Number:
  US11/299,618
• Publication Number:
  US 20070057900A1
• Time in Patent Office: 2,485 Days
• Field of Search: 345/87, 345/102, 345/204, 349/68
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines

Abstract

A liquid crystal backlight device and a method for controlling the same are applied to a liquid crystal display apparatus, in which a backlight module is disposed behind a liquid crystal panel to illuminate the panel. The backlight device produces stable illumination to solve the hold type problem due to the hold-type effect of liquid crystal occurred in the prior art. The control method is used to acquire a stable display time from the liquid crystal characteristics and then process the scan signal to match the display data. Controls of the backlight activation signal, including on/off, time delay, and duty cycle adjustment, are then performed to generate a pulse-width modulated signal and a brightness modulated signal so as to produce stable backlight illumination effect. A better display effect can therefore be accomplished.

Claims

1. A control method of a liquid crystal backlight device, said control method comprising the steps of:

obtaining a stable display time from the intrinsic delay characteristic of the liquid crystal;

transmitting the obtained stable display time to a signal processing unit for modulation of a backlight illumination signal;

modulating the backlight illumination signal, including adjusting a backlight illumination frequency, a backlight illumination intensity and a pulse width of the backlight illumination signal, by performing delay control using a plurality of backlight activation times of the liquid crystal, wherein the backlight illumination signal has two different amplitudes in a frame time;

performing delay control of the backlight activation times until the liquid crystal reaches a steady state;

generating a modulated backlight activation signal by a modulation signal regarding the pulse width of the backlight illumination signal, the backlight illumination frequency, or the backlight illumination intensity according to information of a duty cycle of a backlight activation signal of a backlight module; and

controlling a backlight activation timing;

wherein the backlight activation timing of the backlight module is controlled to change its backlight illumination pattern including the backlight illumination frequency, the backlight illumination intensity and the pulse width of the backlight illumination signal by adjusting the duty cycle of the backlight activation signal in order to achieve stable backlight illumination.

2. The control method as claimed in claim 1, wherein said step of modulating the backlight illumination signal further comprises a step of adjusting a duty cycle of backlight illumination.

3. The control method as claimed in claim 1, wherein said step of modulating the backlight illumination signal further comprises a step of performing pulse-width modulation of backlight illumination.

4. A display apparatus using the control method as claimed in claim 1, comprising:

a display signal output unit for receiving a display signal sent from an external device;

a stable-time calculation unit coupled with said display signal output unit and used to obtain a stable display time according to said display signal received by said display signal output unit;

a backlight module control unit for receiving said pulse-width modulated signals to produce a plurality of backlight activation signals;

a backlight module coupled with said backlight module control unit and used for backlight illumination of a liquid crystal module;

a display controlling unit coupled with said display signal output unit and used to generate display data and a scan signal;

a scan drive unit coupled with said liquid crystal module; and

a data drive unit coupled with said liquid crystal module;

wherein the signal processing unit is coupled with said stable-time calculation unit and used to produce a plurality of pulse-width modulated signals based on delay characteristic of the liquid crystal.

5. The display apparatus having a liquid crystal backlight device as claimed in claim 4, wherein said signal processing unit further comprises a time delay control unit used to adjust an activation time of said backlight module according to a signal output by said display signal output unit.

6. The display apparatus having a liquid crystal backlight device as claimed in claim 4, wherein said signal processing unit further comprises a duty cycle control unit.

7. The display apparatus having a liquid crystal backlight device as claimed in claim 4, wherein said backlight module control unit is an inverter for providing power for said backlight module.

8. The display apparatus having a liquid crystal backlight device as claimed in claim 4, wherein said display controlling unit is an analog to digital converter.

9. The display apparatus having a liquid crystal backlight device as claimed in claim 4, wherein said backlight module control unit further comprises an amplification circuit for adjusting the backlight illumination intensity.

10. A control method of a liquid crystal backlight device, said control method comprising the steps of:

acquiring a stable display time from intrinsic delay characteristics of the liquid crystal;

performing a delay control using a plurality of backlight activation times intrinsically regarding the liquid crystal;

adjusting a duty cycle of backlight illumination;

performing pulse-width modulation of backlight illumination;

adjusting a backlight illumination frequency;

adjusting a backlight illumination intensity;

generating a modulated backlight activation signal by a modulation signal regarding pulse width of an illumination signal, illumination frequency, or illumination intensity according to information of a duty cycle of a backlight activation signal; and

controlling a backlight illumination pattern including the illumination frequency, the illumination intensity, and the pulse width of the illumination signal by adjusting the duty cycle of the backlight activation signal of said backlight module, wherein the illumination signal has two different amplitudes in a frame time.