Patent ID: 7986720

Claim:
A circuit for driving a light-emitting element, comprising: a boost circuit for boosting an input voltage and supplying a boost voltage to the light-emitting element, where the boost circuit comprises: a regulator including an input terminal to which the input voltage is supplied, a first output terminal, and a second output terminal, where a voltage from the first output terminal is applied through a diode to the light emitting element as the boost voltage; and, a first reactance and a second reactance connected together in series between a cathode side of the diode and a ground, the second output terminal connected to a connection point between the first reactance and the second reactance; a photoreceptor for monitoring light from the light-emitting element; and a boost control circuit for controlling the boost voltage based on a monitored amount of the photoreceptor, where an output of the boost control circuit is divided by the first reactance and the second reactance and supplied to the second output terminal, wherein the voltage from the first output terminal is controlled based on a voltage supplied to the second output terminal.