Patent ID: 7915880

Claim:
A step-up DC-DC converter, comprising: a direct current power source; an inductor connected to a positive polarity of the direct current power source; a first switching element connected between the inductor and ground; a second switching element; a smoothing capacitor connected to the inductor via the second switching element; a driver controller configured to control switching ON or switching OFF the first switching element and the second switching element; and a control changing unit configured to change a control operation of the driver controller according to a load current; wherein; the driver controller performs one of operations of switching OFF the second switching element and switching ON or switching OFF the second switching element according to an output from the control changing unit, two of the second switching elements are connected in series, a back gate of one of the second switching elements is connected to the inductor, and a back gate of the other one of the second switching elements is connected to the smoothing capacitor, and when the step-up DC-DC converter is in a standby state and the second switching elements are switched OFF, charging the smoothing capacitor with a direct current to is prevented.