Patent ID: 9058776
Filing Date: 2015-06-16
Classification: G09G,H05B,Y02B

Abstract:
1. A LED backlight source for a liquid crystal device, comprising: a boost circuit for boosting an input DC voltage and for outputting the boosted DC voltage; a plurality of LED strings connected in parallel, wherein each of the LED strings comprises a plurality of serially connected LEDs and a first resistor, and each of the LED strings receives the boosted DC voltage from the boost circuit; an over-current protection circuit for controlling an output power of the boost circuit according to a detected resistance; a short-connection protection circuit for adjusting the resistance detected by the over-current protection circuit according to a voltage at two ends of the first resistor; wherein when the voltage at two ends of the first resistor of one of the LED strings is smaller than a first reference voltage, the short-connection protection circuit increases the resistance detected by the over-current protection circuit so as to reduce the output power of the boost circuit, and when the voltage at two ends of the first resistor of one of the LED strings is greater than the first reference voltage, the short-connection protection circuit decreases the resistance detected by the over-current protection circuit so as to increase the output power of the boost circuit; wherein the short-connection protection circuit comprises: a detecting circuit for comparing the voltage at two ends of the first resistor of each of the LED strings with the first reference voltage and for outputting different level signals based on a comparison result; a switch circuit for adjusting the resistance detected by the over-current protection circuit according to the level signals output from the detecting circuit; and wherein when the voltage at two ends of first resistor of each of the LED strings are greater than the first reference voltage, the detecting circuit outputs low level signals, and when the voltage at two ends of first resistor of the LED strings are smaller than the first reference voltage, the detecting circuit outputs high level signals, and the switch circuit increases the resistance detected by the over-current protection circuit.