DC-DC converter including circuit to detect switching frequency of switching supply

A DC-DC converter to convert an input voltage input from an input terminal into a predetermined voltage and to output the predetermined voltage through an output terminal, the DC-DC converter comprising:

• a first switching device to provide energy for an inductor;
• a second switching device or a rectifying device to discharge the energy from the inductor to the output terminal;
• an error amplifier to amplify an error voltage between a first reference voltage and a monitoring voltage obtained by dividing an output voltage output from the output terminal;
• a set signal generation circuit for the first switching device, including a first comparator into which a second reference voltage and an output of the error amplifier are input;
• a reset signal generation circuit for the first switching device;
• a control circuit for the first switching device and one of the second switching device and the rectifying device into which an output from the set signal generation circuit for the first switching device and an output from the reset signal generation circuit for the first switching device are input;
• and
• a detection circuit to detect a switching frequency of an electric power supply and to output an output signal, corresponding to the detected switching frequency, to the first comparator, to control a characteristic of the first comparator, based on the detected switching frequency.