Direct-current converter

A direct-current converter comprising:

• a high-frequency converting circuit that converts a direct-current voltage of a direct-current power source to a high-frequency alternating-current voltage;
• a first transformer having a primary winding and a secondary winding;
• and
• a rectification smoothing circuit that rectifies and smoothens a voltage induced in the secondary winding of the first transformer to pick up a direct-current output, wherein
• the high-frequency converting circuit includes a second transformer having a first winding and a second winding, a first switching element having a first main electrode connected to a negative pole of the direct-current power source and a second main electrode connected to a positive pole of the direct-current power source through the first winding of the second transformer, and a second switching element having a third main electrode connected to the negative pole of the direct-current power source and a fourth main electrode connected to the positive pole of the direct-current power source through the second winding of the second transformer, the second switching element being turned on/off alternately to the first switching element being turned on/off, and
• the primary winding of the first transformer is connected to one connection point between the first winding of the second transformer and the second main electrode of the first switching element and another connection point between the second winding of the second transformer and the fourth main electrode of the second switching element.