LED (Light Emitting Diode) backlight source and liquid-crystal display equipment

Abstract

An LED backlight source comprises a boosting circuit (210) used for boosting and outputting the input direct-current voltage (Vin); a plurality of LED strings (220) connected in parallel, wherein each LED string (220) comprises a plurality of LEDs connected in series and receives the direct-current voltage output from the boosting circuit (210); a plurality of constant-current driving circuits (230) connected in parallel and used for controlling the magnitude of current flowing through each LED string (220), wherein each constant-current driving circuit (230) controls the magnitude of current of at least one LED string (220), and a first constant-current driving circuit (231) controls the on-off of the boosting circuit (210); a low-voltage protection control circuit (240) outputting low-voltage protection voltage to each constant-current driving circuit (230), each constant-current driving circuit (230) determining, according to the received low-voltage protection voltage, whether to stop operating, wherein the low-voltage protection voltage output to the first constant-current driving circuit (231) is less than the low-voltage protection voltage output to the other constant-current driving circuits. The backlight source can turn off or on multiple LED strings (220) simultaneously to improve the optical grade of the LED backlight source. A liquid-crystal display device using the LED backlight source is also disclosed.

Description

technical field [0001] The invention relates to the field of liquid crystal display. More specifically, it relates to an LED backlight source and a liquid crystal display device. Background technique [0002] With the continuous advancement of technology, the backlight technology of liquid crystal display devices has been continuously developed. A backlight source of a traditional liquid crystal display device uses a cold cathode fluorescent lamp (CCFL). However, due to the shortcomings of CCFL backlight such as poor color reproduction ability, low luminous efficiency, high discharge voltage, poor discharge characteristics at low temperature, and long time for heating to reach a stable gray level, backlight technology using LED backlight has been developed. [0003] In the liquid crystal display device, the LED backlight is arranged opposite to the liquid crystal display panel, so that the LED backlight provides a display light source to the liquid crystal display panel, w...

AI Technical Summary

Problems solved by technology

Therefore, when the input DC voltage is too low, the voltage across the resistor R3 just triggers the undervoltage protection function of a certain constant current drive circuit, and at this time the voltage across the resistor R3 is not necessarily greater than that of other constant current drive circuits The trigger voltage of the undervoltage protection will cause some of the LED strings 120 connected in parallel to go out, while the other part of the LED strings still work normally, which will have a certain negative impact on the optical quality of the LED backlight.

In addition, when the input DC voltage Vin changes from small to large, when the multiple LED strings 120 in parallel resume to emit light, the above-mentioned inconsistency of actions will also occur.

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