A converter comprising: an inductor; a first switch and a second switch, one end of each of which is connected to one end of the inductor; a third switch, one end of which is connected to the other end of the inductor; and a fourth switch connected between the other ends of the inductor and the second switch, and turning ON/OFF individually the first switch, the second switch, the third switch and the fourth switch so as to convert a voltage applied between the other ends of the first switch and the second switch, a diode, anode and cathode of which are connected respectively to one end and the other end of the third switch; maintaining means for maintaining the third switch at OFF after transition has occurred from a state that the first switch and the third switch are OFF to a state that a ON/OFF switching of the first switch is allowable and the third switch is OFF; charactized by generating means for turning, during the time that the maintaining means maintains the third switch at OFF, ON/OFF individually the first switch, the second switch and the fourth switch such that the state of the first switch, the second switch and the fourth switch transits in the order of a first state that the first switch, the second switch and the fourth switch are respectively ON, OFF, and ON, a second state that the first switch, the second switch and the fourth switch are respectively ON, OFF, and OFF, and a third state that the first switch, the second switch and the fourth switch are respectively OFF, ON, and OFF so as to generate an electric current that flows between the other end of the third switch and the second-switch-side one end of the fourth switch; and release means for releasing, after the generating means has generated the electric current, the maintaining of OFF of the third switch performed by maintaining means such that the first switch, the second switch, the third switch and the fourth switch sequentially transit between a first state in which the first switch, the second switch, the third switch and the fourth switch are ON, OFF, OFF, and ON, a second state in which the first switch, the second switch, the third switch and the fourth switch are ON, OFF, ON, and OFF, and a third state in which the first switch, the second switch, the third switch and the fourth switch are OFF, ON, ON, and OFF. an inductor; a first switch and a second switch, one end of each of which is connected to one end of the inductor; a third switch, one end of which is connected to the other end of the inductor; and a fourth switch connected between the other ends of the inductor and the second switch, and turning ON/OFF individually the first switch, the second switch, the third switch and the fourth switch so as to convert a voltage applied between the other ends of the first switch and the second switch, a diode, anode and cathode of which are connected respectively to one end and the other end of the third switch; maintaining means for maintaining the third switch at OFF after transition has occurred from a state that the first switch and the third switch are OFF to a state that a ON/OFF switching of the first switch is allowable and the third switch is OFF; charactized by generating means for turning, during the time that the maintaining means maintains the third switch at OFF, ON/OFF individually the first switch, the second switch and the fourth switch such that the state of the first switch, the second switch and the fourth switch transits in the order of a first state that the first switch, the second switch and the fourth switch are respectively ON, OFF, and ON, a second state that the first switch, the second switch and the fourth switch are respectively ON, OFF, and OFF, and a third state that the first switch, the second switch and the fourth switch are respectively OFF, ON, and OFF so as to generate an electric current that flows between the other end of the third switch and the second-switch-side one end of the fourth switch; and release means for releasing, after the generating means has generated the electric current, the maintaining of OFF of the third switch performed by maintaining means such that the first switch, the second switch, the third switch and the fourth switch sequentially transit between a first state in which the first switch, the second switch, the third switch and the fourth switch are ON, OFF, OFF, and ON, a second state in which the first switch, the second switch, the third switch and the fourth switch are ON, OFF, ON, and OFF, and a third state in which the first switch, the second switch, the third switch and the fourth switch are OFF, ON, ON, and OFF.