PURPOSE: To improve the efficiency of a power source by accumulating in a capacitor a regenerative energy obtained at the time of electrically discharging a load and by using said energy at the time of charging said load subsequently.

CONSTITUTION: A power source 4 is connected in series with a capacitive load 1 via a first switch 2 and a first diode 5. Also, a second switch 3 and the primary side of a current transformer 6 are connected in parallel with said capacitive load 1. A second diode 7 and a capacitor 8 are connected in series with the secondary side of said current transformer 6 and said capacitor 8 is connected in parallel manner with the power source 4 and the first diode 5. An electric current regenerated at the time of discharging said capacitive load 1 is accumulated in the capacitor 8 to be reused at the time of charging said load subsequently.