Patent ID: 8907565

Claim:
A power supply device that supplies power to a semiconductor light source load and lights the semiconductor light source load, comprising: a DC-DC converter that includes an inductance element and a switching element, and performs voltage conversion by storing energy in the inductance element from an input power source when the switching element is on, and discharging the energy, the energy being stored in the inductance element, to a load side when the switching element is off; and a controller that controls ON/OFF operations of the switching element so that an output current of the DC-DC converter can be the same as a target value, wherein a timing regulator that regulates timing of turning on the switching element is provided at least in the controller so that a current flowing through the inductance element can flow in a continuous mode operation, wherein the timing regulator is composed so as to detect a current flowing when the energy is discharged from the inductance element to the load side when the switching element is off, and to turn on the switching element when a value of the detected current becomes equal to or lower than a predetermined value, and wherein a time while the switching element is off is controlled to continue for at least a first predetermined minimum time, and to not continue beyond a second predetermined maximum time that is higher than the first predetermined minimum time.