| 摘要 |
PROBLEM TO BE SOLVED: To obtain power a supply unit suitable for supplying power to a load whose operating range is between an upper limit voltage and a lower limit voltage. SOLUTION: The power supply unit is composed of a capacitive element 3a, a DC-DC converter 3b, voltage detectors 4e and 4d which detect the charged voltage of the capacitive element 3a, a switch SW2, and a control portion 4. The control portion 4 controls and causes the DC-DC converter 3b to charge the capacitive element 3a. If the charged voltage of the capacitive element 3a becomes equal to or greater than the lower limit value, the control portion 4 turns on the switch SW2 to connect the capacitive element 3a to the load 1. If the charged voltage exceeds the upper limit value, the control portion 14 stops the operation of the DC-DC converter 3b, and thereafter keeps the DC-DC converter 3b stopped until the charged voltage falls below the lower limit voltage.
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