DC voltage conversion circuit having output voltage with a predetermined magnitude

A DC voltage conversion circuit comprising:

• a first DC power supply;
• a first semiconductor switching device which is connected to two ends of the first DC power supply through an inductor;
• a series circuit which is connected in parallel with the switching device and which includes a rectifier device, a parasitic inductor and a load, so that an input voltage supplied from the DC power supply can be converted into an output voltage with a predetermined magnitude by a switching operation of the switching device and supplied to the load;
• a series circuit which is connected to two ends of the rectifier device and which includes a first snubber capacitor and a first snubber diode;
• and
• a charging circuit which charges the first snubber capacitor to a voltage lower than the input voltage or the output voltage in a period of time when the switching device is ON,
• wherein the charging circuit includes a series circuit of a second DC power supply and a diode,
• wherein a current does not flow into the first snubber diode and the first snubber capacitor until a sum of a voltage of the first semiconductor switching device and a voltage of the first snubber capacitor exceeds a voltage across the load;
• and
• when a sum of the voltage of the first semiconductor switching device and the voltage of the first snubber capacitor exceeds the voltage across the load, a surge voltage occurs in the parasitic inductor.