| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the operation of detecting power failure and to attain a reduction in a power loss by a termination resistor, with regard to a power supply unit equipped with a power failure detecting circuit. SOLUTION: The power supply unit is equipped with a rectifying circuit 2 for rectifying AC voltage, a boost converter 3 for inputting the rectified output voltage rectified by the rectifying circuit 2, a DC/DC converter 4 for inputting the output voltage from the boost converter 3 to apply a specified DC voltage to a load 5, and a power failure detecting circuit 9 for stopping the operation of the DC/DC converter 4 upon detection of power failure. The power supply unit furthermore includes an auxiliary rectifying circuit 6 for inputting into the power failure detecting circuit 9 the DC voltage rectified from AC voltage, a series circuit consisting of the termination resistor 7 to which the output voltage of the auxiliary rectifying circuit 6 is applied and of switching elements 8 such as field effect transistors or the like, and a control circuit 11 for inputting into the DC/DC converter 4 a power failure detecting signal of the power failure detecting circuit 9 as an operation stop signal and for turning on the switching element 8. COPYRIGHT: (C)2008,JPO&INPIT
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