Patent ID: 7224128

Claim:
A device for driving light emitting diodes, for applying in a backlight module of a liquid crystal display (LCD), the device comprising: a DC-to-DC converter, having a first DC-to-DC converter end and a second DC-to-DC converter end, the second DC-to-DC converter end being coupled to a fixed voltage, the DC-to-DC converter outputting a DC voltage from the first DC-to-DC converter end according to a feedback signal; a light emitting diode (LED) string coupled to the first DC-to-DC converter end; a switch electrically connected to the LED string in series, for allowing the DC voltage to drive the LED string and allowing a DC current to flow through the LED string when the switch is turned on; and a feedback circuit for outputting the feedback signal according to the DC current, the feedback circuit comprising: a current-voltage converter, having a first end and a second end, the first end of the current-voltage converter being coupled to the switch, the second end of the current-voltage converter being coupled to the second DC-to-DC converter end, the DC current flowing through the DC-to-DC converter when the switch is turned on, causing the current-voltage converter to generate a first reference voltage according to the DC current, the first reference voltage being used as the feedback signal; whereby the LED string is lit up to reach a predetermined brightness level when the switch is turned on, and the LED string ceases illumination when the switch is turned off.