Patent ID: 6975520

Claim:
A DC-DC converter configured such that a current of a primary coil of a boosting transformer which is supplied from a power source unit is intermittently caused to flow through said converter by a power MOS-FET, and an ignition capacitor is charged with electricity through a rectifier diode using a voltage of a secondary coil of said boosting transformer boosted by a flyback voltage of a coil, said current naturally flowing to the power MOS-FET, and said DC-DC converter comprising: a current detecting unit for detecting a drain current of said power MOS-FET; and a control unit having a one-shot pulse outputting circuit for, when a current value detected by said current detecting unit exceeds a predetermined threshold, outputting a down one-shot with that time point as a trigger, and an AND circuit for, on the basis of the logical product of an output of said one-shot pulse outputting circuit and a signal supplied from said power source unit, supplying a voltage used to drive a gate of said power MOS-FET; wherein said control unit, when the drain current detected by said current detecting unit exceeds a predetermined threshold, turning off said power MOS-FET for a fixed period of time, and then turning on said power MOS-FET again.