| 摘要 |
<p>PROBLEM TO BE SOLVED: To extend a period of time in which electric power can be supplied without increasing a capacity of a smoothing capacitor of a primary side of a power supply device when a power failure occurs.SOLUTION: A power supply device includes: an all-night AC-DC converter 7 which has a transformer 5, a smoothing capacitor 12 for smoothing a voltage rectified from AC voltage, an FET 13 for switching a current flowing through a primary coil of the transformer 5, and a power supply IC 20 for stopping operation of the FET 13 when an output of the smoothing capacitor 12 is a low voltage, and which converts the AC voltage to a DC voltage (5 VA) 6; an all-night DC-DC converter 9 for converting the DC voltage (5 VA) 6 to a DC voltage (3.3 V) 8; and a CPU 3 for performing control so that the operation of the FET 13 is continued by the power supply IC 20 even when a power failure is detected.</p> |
