Digital type power-failure detector with wide AC frequency response

A proposed quick detector possesses the period data as a digital counter value, and has the novel feature that, when an AC power failure lasts more than one cycle, a power failure signal is generated. The following advantages also exist: this detector can detect a power failure about 100 ms faster than a conventional detector, which checks power failures by means of DC voltage drop for a 60 Hz power source; it operates on a wide AC frequency range, and therefore operates on AC frequencies including not only commercial power but also a high-frequency subdistribution system in buildings, vessels and aircraft; an auxiliary pulse synchronous to the AC power source before it fails is generated during the power failure; the detector is constructed without analog devices such as an operational amplifier and is realized in an IC form