| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply unit capable of achieving cost reduction, little loss and high efficiency while coping with a sudden drop in an input voltage during a power failure and the like. <P>SOLUTION: A preconverter 40 is connected with a pre-stage of a DC-DC converter 50 as a switching power supply. The preconverter 40 includes a boost chopper, and a controller 70 operates the boost chopper when an input voltage into the preconverter 40 is lower than a predetermined reference value and boosts the input voltage. A bypass circuit 80 includes a bypass route for bypassing the preconverter or the boost chopper and a bypass switch inserted into the bypass route. The bypass switch brings the bypass route into conduction while the power supply unit 100 is under a steady operating state. <P>COPYRIGHT: (C)2012,JPO&INPIT |
