Patent ID: 7781988

Claim:
A control circuit of a DC/DC converter for supplying a driving voltage to a light emitting element, said control circuit comprising: a voltage detection terminal which receives a detection voltage that corresponds to an output voltage of the DC/DC converter; a hysteresis comparator which compares the detection voltage with two threshold voltages, and outputs a first-level comparison signal when the detection voltage is smaller than the lower threshold voltage, and outputs a second-level comparison signal when the detection voltage is greater than the higher threshold voltage; a light-emission permission terminal which outputs a signal that corresponds to the comparison signal from the hysteresis comparator; a switching control unit which controls the switching operation of a switching element included in said DC/DC converter according to the comparison signal output from said hysteresis comparator as a reference signal, and instructs the switching element of said DC/DC converter to perform switching operation during a period when the comparison signal is at the first level, and suspends the switching operation of the switching element of said DC/DC converter during a period when the comparison signal is at the second level, and a first output terminal which receives an output signal from the switching control unit; wherein light emission of the light emitting element is inhibited during a period when the comparison signal is at the first level, and wherein light emission of the light emitting element is permitted during a period when the comparison signal is at the second level.