Uninterrupted double supplying power source unit

The present invention provides an uninterruptible duplexed power supply system, which is capable of achieving high efficiency and compact size, and moreover, is capable of solving for a power circuit failure in an energized state. This uninterruptible duplexed power supply system connects via a high-frequency transformer (7) a power circuit (A), which rectifies AC from a commercial AC power supply (1), and which comprises a switching device (6) for outputting; a secondary DC outputting circuit (B), which supplies electric power to a load; and a DC power circuit (C), comprising a switching device (20) for synchronizing with switching device (6) of power circuit (A), and for operating this DC power circuit (C), and is constituted so that the power circuit (A) is unitized, and this power circuit unit is detachable in a connected state, wherein same is connected electrically to the high-frequency transformer (7), and in a connection release state, and is constituted so as to provide means for buffering or preventing overcurrent reverse current resulting from induced voltage from the DC power circuit (C) via the high-frequency transformer (7) to the power circuit (A), and so that the power circuit unit is detachable in an energized state.