POWER SOURCE DEVICE

PROBLEM TO BE SOLVED: To minimize power supplied from an AC line, to make a transformer small and to reduce operation cost by controlling the ignition pulse width of a self-arc-extinguishing semiconductor device to suppress load current, and connecting a capacitor in parallel to the output part of a control rectifying device. SOLUTION: AC power from an AC bus 1 is' supplied to a control rectifying device 3 through a rectifying transformer 2 to convert into DC power, and the DC power is supplies to a load 6 through a chopper circuit comprising self-arc-extinguishing semiconductor devices 13a, 13b, and diodes 14a, 14b. In the power source device, the ignition pulse width of the self-arc-extinguishing semiconductor devices 13a, 13b is controlled with a pulse width control circuit 17 to control load current 52 detected with a DC current detector 9. The output voltage of a control rectifying device 3 is controlled based on an average voltage value obtained in the DC voltage detector 8 and an average value detecting circuit 18. A capacitor 16 is connected in parallel to the control rectifying device 3 through a reactor 15, and energy in falling of the load is effectively reused in rising.