INSTANTANEOUS STOP COPING CIRCUIT

PURPOSE:To obtain a stable presetting or resetting control signal against an instantaneous stop of an electric power source, by providing a trigger monostable multivibrator for detecting whether an electric power source input exists or not, from an electric power source input which is not smoothed nor stabilized yet. CONSTITUTION:A main electric power source is converted to a pulse of twice the frequency of the electric power source by a rectifying circuit 11, a filter circuit 12 and a slicing circuit 13. By this pulse, a trigger monostable multivibrator 14 is triggered, and its output becomes a constant high level as long as the pulse is inputted. When instantaneous cuf-off of the electric power source occurs, an output of the trigger monostable multivibrator 14 becomes a low level, and when the electric power source is reset, a monostable multivibrator 15 is triggered. When a constant interval of time passes away after an apparatus becomes stable, a control output is outputted from a monostable multivibrator 16. In this way, even after instantaneous cut-off of the electric power source, a stable control output can be obtained.