Patent ID: 7710049

Claim:
A LED drive circuit comprising: a boost circuit configured for receiving an input voltage and providing an output voltage according to a control signal; at least two branch circuits, each including a plurality of LEDs connected in series and providing a feedback signal representative of a current flowing therein, thus there are at least two feedback signals, each of the branch circuits further including a branch switch and a feedback resistor connected in series with the LEDs; a selector configured for alternatively selecting one of the feedback signals as an output feedback signal and switching on or off a corresponding one of the two branch circuits, the selector including a first selecting unit and a second selecting unit, wherein: the first selecting unit generates a switch signal for each of the two branch circuits so that branch switches of the two branch circuits are switched on alternatively; and the second selecting unit includes at least two transmission gates receiving the feedback signals of the corresponding branch circuits and outputting the output feedback signal of one of the branch circuits that is switched on; and a pulse-width modulation (PWM) controller configured for generating a pulse-width modulation signal as the control signal for the boost circuit according to the output feedback signal of the selector.