Backlight of liquid crystal display device and driving circuit thereof

• US 9,402,288 B2
• Filed: 05/15/2014
• Issued: 07/26/2016
• Est. Priority Date: 02/27/2014
• Status: Active Grant

• Current Assignee: Shenzhen China Star Optoelectronics Technology Co., Ltd. (TCL Technology Group Corp.)
• Original Assignee: Shenzhen China Star Optoelectronics Technology Co., Ltd. (TCL Technology Group Corp.)
• Inventors: Xu, Xiangyang
• Primary Examiner(s): CRAWFORD, JASON
• Application Number:
  US14/380,905
• Publication Number:
  US 20150366017A1
• Time in Patent Office: 803 Days
• Field of Search: 315/185.R, 315191-192, 315/291, 315/294, 315/297, 315/307
• US Class Current: 1/1
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133612 Electrical details
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/34 by control of light from an independent 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
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/42 Antiparallel configurations

Abstract

The present invention relates to a backlight of a liquid crystal display device and a driving method thereof. The backlight comprises a LED lamp bead group and a backlight driving module. The LED lamp bead group includes a plurality of strings of LED lamp bead which are opposite in term of positive and negative directions. The backlight driving module is electrically connected to the LED lamp bead group to output a voltage signal and a current signal to drive the LED lamp bead group, wherein the voltage signal is configured as more than one serials of periodic square-wave signal, under the action of which a string of LED lamp bead of positive direction and a string of LED lamp bead of negative direction emit light in an alternate manner, and the brightness of emitted light is determined by the magnitude of the current signal.

Claims

1. A backlight of a liquid crystal display device, comprising:

a LED lamp bead group, including a plurality of strings of LED lamp bead which are opposite in term of positive and negative directions;

a backlight driving module, an output end of which is electrically connected to the LED lamp bead group to output a voltage signal and a current signal to drive the LED lamp bead group, wherein the voltage signal is configured as more than one serials of periodic square-wave signal, under the action of which a string of LED lamp bead of positive direction and a string of LED lamp bead of negative direction emit light in an alternate manner, and the brightness of emitted light is determined by the magnitude of the current signal, wherein

the voltage signal output by the backlight driving module is configured as two serials of periodic square-wave signal, the amplitudes of which two are same and greater than or equal to the turn-on voltage of the string of LED lamp bead, and the frequencies of which two are same but have a phase difference of half period;

the strings of LED lamp bead of positive direction are connected in parallel to each other, wherein one end of each string of positive direction is electrically connected to a first output end of the backlight driving module and the other end thereof is electrically grounded, so as to receive a first serial of periodic square-wave signal; and

the strings of LED lamp bead of negative direction are connected in parallel to each other, wherein one end of each string of negative direction is electrically connected to a second output end of the backlight driving module and the other end thereof is electrically grounded, so as to receive a second serial of periodic square-wave signal.

2. A backlight of claim 1, wherein,

a frequency of the periodic square-wave signal is more than 50 Hz.

3. A backlight of claim 1, wherein,

the number of the strings of LED lamp bead of positive direction is the same as that of the strings of LED lamp bead of negative direction, and each of the strings of LED lamp bead includes the same number of series-connected LED lamp beads.

4. A backlight driving method of a liquid crystal display device, comprising the steps of:

outputting a voltage signal and a current signal to drive a LED lamp bead group including a plurality of strings of LED lamp bead which are opposite in term of positive and negative directions;

wherein the voltage signal is configured as more than one serial of periodic square-wave signal, which enable a string of LED lamp bead of positive direction and a string of LED lamp bead of negative direction to emit light in an alternate manner, at the meanwhile, the magnitude of the current signal is controlled to adjust the brightness of emitted light of the string of LED lamp bead of positive/negative direction wherein,

in the case that the strings of LED lamp bead of positive direction are connected in parallel to each other and electrically connected to a the first output end of the backlight driving module and the strings of LED lamp bead of negative direction are connected in parallel to each other and electrically connected to a second output end of the backlight driving module, the voltage signal is configured as two serials of periodic square-wave signal, the amplitudes of which two are same and greater than or equal to the turn-on voltage of the string of LED lamp bead, and frequencies of which two are same and have a phase difference of half period.

5. A backlight driving method of claim 4, wherein,

a frequency of the periodic square-wave signal is more than 50 Hz.