Hitachi, Ltd.

Yasuo Abe

Hiroshi Kimura

Akihiko Kanouda

Kenichi Onda

Katsunori Hayashi

Masayoshi Sato

Hideaki Horie

A parallelized power supply system including a plurality of switching power supplies each having a circuit for limiting rush current generated when a main switch is turned on. This system can be installed in an apparatus which requires the functions such as power uninterrupted operation and live wire insertion/dismount. Each switching power supply has another power supply for driving the rush current limiter circuit and a relay circuit for supplying relay driving current and making a connection of relay contacts after a predetermined time lapse after the operation start of the switching power supply. An a.c. power is supplied via the relay contacts to each switching power supply. The relay driving time set in the rush current limiter circuit is different for each switching power supply. Accordingly, concentration and excess of rush current when the relay is driven can be suppressed, and sparks at contact pins of a connector to be otherwise generated when the switching power supply is mounted on the connector, can be eliminated so that radiation noises and connector breakage can be avoided. Each of the switching power supplies connected in parallel has a current detecting resistor connected between the low voltage side of a load and the low voltage side of a voltage regulator d.c. output, and at least one operational amplifier for detecting a change in the d.c. output, the negative power supply terminal of the operational amplifier being connected to the current detecting resistor at its one end on the load side.

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Chigasaki, Japan

Yasuo Abe