Patent ID: 6853097

Claim:
An uniterruptible electric power supply comprising: a common line for connecting one end of an AC electric power supply with one end of an AC output; a positive electrode side voltage line and a negative electrode side voltage line which respectively become a positive electrode side and a negative electrode side of DC formed at both ends of diodes connected with each other in series, a connecting point of the diodes connected with each other in series being connected with the other end of the AC electric power supply; a first condenser connected between the common line and the voltage line on the positive electrode side; a second condenser connected between the common line and the voltage line on the negative electrode side; a battery, the negative electrode side of which is connected with the common line; a negative electrode side boosting section semiconductor switch, one end collector side of which is connected with the positive electrode side of the battery; a negative electrode side boosting section reactor connected between the other end emitter side of the negative electrode side boosting section semiconductor switch and the common line; a negative electrode side boosting section diode, one end on the cathode of which is connected with the other end on the emitter side of the negative electrode side boosting section semiconductor switch, the other end on the anode side of which is connected with the negative electrode voltage line; a first semiconductor switch of a balance section and a second semiconductor switch of the balance section connected with each other in series between the positive electrode voltage line and the negative electrode voltage line; a first diode of the balance section and a second diode of the balance section which are respectively connected with the first semiconductor switch of the balance section and the second semiconductor switch of the balance section in reverse parallel with each other; a reactor of the balance section connected between a contacting point, at which the first semiconductor switch of the balance section and the second semiconductor switch of the balance section are contacted with each other, and the common line; and a control section for turning on and off the negative electrode side boosting section semiconductor switch and the second semiconductor switch of the balance section, wherein after the second condenser is electrically charged by the battery when the negative electrode side boosting section semiconductor switch is turned on and off at the time of start, the second semiconductor switch of the balance section is turned on and off so as to electrically charge the first condenser by utilizing voltage of the second condenser.