| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a momentary power failure detector that can report a momentary power failure to an upper controller or a user by detecting it accurately and can prevent erroneous detection when a person turns off power by accident in a servo driver with a sensor for feedback signal. SOLUTION: A momentary power failure detection circuit 1 for outputting a high level during a period before and after the zero-cross point of an AC input power supply voltage waveform and for outputting a low level during a period other than the above is provided. Also, an interval counter 2 counts up at a specific clock during the low level and retains the counted value during the high level. The increment of the counter output is detected by the above zero-cross point, a flag without increment is set when no increment is detected, and a momentary power failure signal is outputted when an increment is detected by an increment detection circuit 3 after the flag is set.</p> |
