Patent ID: 7471287

Claim:
A light source driving circuit, suitable for driving a first light emitting component, the circuit comprising: a power supply circuit, having an output terminal and a feedback terminal, wherein the output terminal is coupled to one terminal of the first light emitting component for supplying a power supply voltage to the first light emitting component and determining the value of the power supply voltage according to a feedback signal received by the feedback terminal; a first dimming circuit, having a first terminal coupled to another terminal of the first light emitting component and a second terminal coupled to a common level, wherein the first dimming circuit determines the on/off states of the first terminal and the second terminal thereof according to the logic states of a pulse width signal; and a feedback circuit, coupled between the first terminal of the first dimming circuit and the feedback terminal of the power supply circuit, for determining the feedback signal according to the on/off state of the first dimming circuit, wherein the feedback circuit comprises: an first impedance detection circuit, comprising a first terminal, a second terminal, and a detection terminal, wherein the first terminal is coupled to the first terminal of the first dimming circuit and the second terminal is coupled to the common level, for determining the level output by the detection terminal of the first impedance detection circuit according to the impedance between the first terminal of the first impedance detection circuit and the second terminal of the first impedance detection circuit: and a feedback voltage control circuit, having an input terminal coupled to the detection terminal of the first impedance detection circuit and an output terminal outputting the feedback signal, for controlling the value of the voltage of the feedback signal according to the level output by the detection terminal of the first impedance detection circuit.