Patent ID: 7009371

Claim:
A DC/DC converter, comprising: a switching element for supplying power from a power supply to a load side output terminal and holding the load side output terminal at an output setting voltage by switching; an error amplifier for amplifying the error between the voltage from the load side output terminal and a error comparison reference voltage; a differentiation circuit for differentiating the voltage from the load side output terminal; a soft start circuit comprising a constant current source and a capacitor that are connected to an output terminal of the differentiation circuit, for generating voltage that gradually rises when the power supply is started up; a triangular wave generator for generating triangular waves; and a comparator for comparing the triangular wave voltage and the voltage from the soft start circuit when the power supply is started up, comparing the triangular wave voltage and the output voltage of the error amplifier during normal operation after the power supply is started up, and controlling the switching of said switching element by the comparison output thereof.