Patent ID: 8115422

Claim:
An LED drive circuit including a switching regulator IC having a breakdown voltage lower than a power supply voltage to be applied between power supply input terminals, for driving an LED by an output current controlled by the switching regulator IC, the LED drive circuit comprising: a voltage clamp circuit for clamping the power supply voltage from a voltage of the one of the power supply input terminals which is located on a positive side to an operating voltage of the switching regulator IC and outputting the operation voltage; and a current detecting circuit for detecting a current flowing through the LED, and outputting a voltage obtained by converting the detected current into a voltage within a range of the operating voltage of the switching regulator IC, wherein the current detecting circuit comprises: a current detecting resistor; a bipolar transistor including a base and an emitter which are connected to both ends of the current detecting resistor; a voltage setting circuit connected to a collector of the bipolar transistor; and a bias circuit connected to the base of the bipolar transistor; wherein the switching regulator IC includes: one power supply terminal connected to one of the power supply input terminals which has the same polarity as the one power supply terminal; another power supply terminal connected to an output terminal of the voltage clamp circuit; and a feedback voltage input terminal connected to an output terminal of the current detecting circuit.