Liquid crystal display, LED backlight source, and the driving method thereof

A LED backlight source for a liquid crystal display, comprising:

• a DC voltage input for inputting DC voltage;
• a boost circuit for increasing the voltage of the DC input and outputting the boosted DC voltage;
• a LED strip comprising a plurality of serially connected LEDs and a first resistor (R1), the LED strip receives the boosted DC voltage from the boost circuit, wherein the DC voltage of the LED strip is smaller than or equal to the boosted DC voltage output from the boost circuit;
• a constant current driving circuit for adjusting the voltage at two ends of the first resistor (R1) so as to control the current of the LED strip and for outputting a level signal to the boost circuit;
• and
• wherein the voltage at two ends of the first resistor is decreased by reducing the reference voltage of the constant current driving circuit so that the current of the LED strip is wherein the boost circuit comprises an inductor (L), a second metal oxide silicon (MOS) transistor Q2, a rectifier diode (D) and a capacitor (C), wherein one end of the inductor (L) connects to the DC input, and the other end of the inductor (L) connects to a positive end of the rectifier diode (D), the drain of the second MOS (Q2) connects between the inductor (L) and the positive end of the rectifier diode (D), one end of the capacitor (C) connects to a negative end of the rectifier diode (D) and to the positive end of the LED strip, the other end of the capacitor (C) connects to the source of the second MOS (Q2), and the gate of the second MOS (Q2) connects to the constant current driving circuit.

A liquid crystal display, comprises a liquid crystal panel and a LED backlight source opposite to the liquid crystal panel, the LED backlight source supplies lights to the liquid crystal panel, the LED backlight source comprises:

• a DC voltage input for inputting DC voltage;
• a boost circuit for increasing the voltage of the DC input and outputting the boosted DC voltage;
• a LED strip comprising a plurality of serially connected LEDs and a first resistor (R1), the LED strip receives the boosted DC voltage from the boost circuit, wherein the DC voltage of the LED strip is smaller than or equal to the boosted DC voltage output from the boost circuit;
• a constant current driving circuit for adjusting the voltage at two ends of the first resistor (R1) so as to control the current of the LED strip and for outputting a level signal to the boost circuit;
• and
• wherein the voltage at two ends of the first resistor is decreased by reducing the reference voltage of the constant current driving circuit so that the current of the LED strip is decreased, wherein the boost circuit comprises an inductor (L), a second metal oxide silicon (MOS) transistor Q2, a rectifier diode (D) and a capacitor (C), wherein one end of the inductor (L) connects to the DC input, and the other end of the inductor (L) connects to a positive end of the rectifier diode (D), the drain of the second MOS (Q2) connects between the inductor (L) and the positive end of the rectifier diode (D), one end of the capacitor (C) connects to a negative end of the rectifier diode (D) and to the positive end of the LED strip, the other end of the capacitor (C) connects to the source of the second MOS (Q2), and the gate of the second MOS (Q2) connects to the constant current driving circuit.