Unlock instant, AI-driven research and patent intelligence for your innovation.

Backlight driving circuit and liquid crystal display

a backlight driving circuit and liquid crystal display technology, applied in static indicating devices, instruments, optics, etc., can solve the problems of parasitic capacitance between the gate, ccfl needs a long time, and low lighting efficiency

Inactive Publication Date: 2015-03-05
TCL CHINA STAR OPTOELECTRONICS TECH CO LTD
View PDF2 Cites 13 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a backlight driving circuit and a LCD that can generate PWM optical signals with a certain duty-cycle ratio to control the LED string to emit lights normally or stop its operation. This allows the backlight driving circuit to operate normally and ensures the constant-current driving chip works efficiently.

Problems solved by technology

However, as the CCFL backlight is characterized by attributes including low color reduction ability, low lighting efficiency, high discharging voltage, bad discharging characteristics in low temperature, and also, the CCFL needs a long time to achieve a stable gray scale, LED backlight source is a newly developed technology.
However, parasitic capacitance exists between the gate and the source of the MOS transistor Q2.
In this way, the charging time of the parasitic capacitance C is short, which may results in that the MOS transistor Q2 cannot be fully turn on and the current passing through the LED string 120 cannot reach a predetermined level.
Especially, if the duty-cycle ratio of the PWM optical signals is too small, the MOS transistor Q2 may not be in be turn on in time.

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Backlight driving circuit and liquid crystal display
  • Backlight driving circuit and liquid crystal display
  • Backlight driving circuit and liquid crystal display

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0024]FIG. 2 is a schematic view of the backlight driving circuit in accordance with a The backlight driving circuit includes a boost circuit 210, a constant-current driving chip 220, a detecting module 230, and a LED string 240 coupled with the boost circuit 210.

[0025]The boost circuit 210 boosts the input voltage Vin when being controlled by the constant-current driving chip 220 so as to output the voltage capable of driving the LED string 240 to emit lights normally. In addition, the input voltage Vin is also provided to the constant-current driving chip 220 to act as the operation voltage. The detecting module 230 receives and calculates the external PWM optical signals to obtain a duty-cycle ratio of the PWM optical signals. The detecting module 230 then compares the duty-cycle ratio of the external PWM optical signals with a predetermined threshold to determine if the control signals have to be generated for the constant-current driving chip 220 such that the constant-current...

second embodiment

[0033]FIG. 3 is a schematic view of the backlight driving circuit in accordance with a

[0034]As shown in FIG. 3, the backlight driving circuit includes the boost circuit 210, the constant-current driving chip 220, the detecting module 230, and the LED string 240 coupling with the boost circuit 210.

[0035]The boost circuit 210 boosts the input voltage Vin when being controlled by the constant-current driving chip 220, and outputs the voltage capable of driving the LED string 240 to emit lights normally. In addition, the input voltage Vin is also provided to the constant-current driving chip 220 to act as the operation voltage of the constant-current driving chip 220. The detecting module 230 receives the external PWM optical signals and calculates the PWM optical signals to obtain the duty-cycle ratio. The detecting module 230 then compares the duty-cycle ratio of the PWM optical signals and the predetermined threshold to determine whether the control signals have to be generated for t...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

PUM

PropertyMeasurementUnit
input voltageaaaaaaaaaa
boosted voltageaaaaaaaaaa
voltageaaaaaaaaaa
Login to View More

Abstract

A backlight driving circuit is disclosed. The backlight driving circuit includes a boost circuit, a constant-current driving chip, a detecting module and a LED string coupled with the boost circuit. The boost circuit boosts an input voltage and then provides the boosted voltage to the LED string. The detecting module receives and calculates external PWM optical signals to obtain a duty-cycle ratio of the PWM optical signals, and compares the duty-cycle ratio of the external PWM optical signals with a predetermined threshold to determine if control signals have to be generated for the constant-current driving chip such that the constant-current driving chip controls the current passing through the LED string. The backlight driving circuit can operate normally even when the duty-cycle ratio of the PWM optical signals is very small. In addition, a liquid crystal display includes the above backlight driving circuit is also disclosed.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present disclosure relates to liquid crystal display technology, and more particularly to a backlight driving circuit and a liquid crystal display (LCD).[0003]2. Discussion of the Related Art[0004]With the technology revolution, backlight technology of LCDs has been developed. Typical LCDs adopt cold cathode fluorescent lamps (CCFL) as the backlight sources. However, as the CCFL backlight is characterized by attributes including low color reduction ability, low lighting efficiency, high discharging voltage, bad discharging characteristics in low temperature, and also, the CCFL needs a long time to achieve a stable gray scale, LED backlight source is a newly developed technology.[0005]Generally, backlight driving circuits are required to provide a driving voltage for LED strings. FIG. 1 is a schematic view of one conventional backlight driving circuit. As shown in FIG. 1, the backlight driving circuit includes a boos...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

Application Information

Patent Timeline
no application Login to View More
Patent Type & Authority Applications(United States)
IPC IPC(8): G02F1/1335H05B33/08H05B44/00
CPCH05B33/0815G02F1/1336G09G3/342G09G2320/064H05B45/44H05B45/38
Inventor ZHANG, HUALI, FEI
Owner TCL CHINA STAR OPTOELECTRONICS TECH CO LTD