Patent ID: 7557520

Claim:
A light source driving circuit, for driving a first light-emitting element, wherein a terminal of the first light-emitting element is connected to a first voltage, the light source driving circuit comprising: a first dimming circuit, having a first terminal, a second terminal and a pulse width signal input terminal, wherein the first terminal is connected to another terminal of the first light-emitting element, and the pulse width signal input terminal receives a pulse width signal, and the first dimming circuit determines an ON/OFF state between the first terminal and the second terminal according to a logic state of the pulse width signal; a power supply circuit, having an output terminal and a feedback terminal, wherein the output terminal is connected to the second terminal of the first dimming circuit, so as to supply a second voltage to the second terminal of the first dimming circuit, and the power supply circuit determines a value of the second voltage according to a feedback signal received by the feedback terminal, wherein the second voltage is lower than the first voltage; and a feedback circuit, connected between the first terminal of the first dimming circuit and the feedback terminal of the power supply circuit, so as to determine a value of the feedback signal according to the ON/OFF state of the first dimming circuit.