| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device which effectively operates a soft start function even at a restoration time from a power voltage drop which is not less than a threshold that cannot be detected in a conventional case. SOLUTION: The power supply device has a voltage derivative value detecting means for detecting a derivative value of an input power voltage. The device once stops a power supply circuit when the derivative value of the input power voltage detected at the time of restoration from the power voltage drop is not smaller than a prescribed value so as to restart the circuit. If a soft start is required when the input power voltage is rapidly restored, a soft start function is operated and the device is restarted. When it is slowly restored and PWM control can be followed, restarting is not performed. Thus, restarting and the soft start function are operated only when they are required. Thus, the soft start function is operated at the time of rapid restoration even at a restoration time from the voltage drop that is not small than the threshold. Since the function is not restarted at the time of a slow change that can be followed by PWM control and at a time when the voltage drop is small, there is no possibility of repeating restarting frequently. COPYRIGHT: (C)2007,JPO&INPIT
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