| 摘要 |
PURPOSE:To detect a hit of an AC input without setting a voltage nor frequency by controlling the time constant of a CR oscillation circuit according to the frequency of a power source and holding and comparing the peak value of an oscillation output with a comparative reference value. CONSTITUTION:The output of an AC power source 1 is converted into a direct curremt by the secondary winding 2a of a transformer 1, rectifying circuit 3, etc., and the current is impressed to the CR oscillation circuit formed of a capacitor 4, resistances 5 and 6, transistor (TR)17, etc. This TR17 is controlled by a time constant circuit whose output is attenuated more and more as AC frequencies of the secondary winding 2b, capacitors 10 and 12, resistance 11, etc., are higher and higher, and the potential at a node (a) which corresponds to the minimum potential E0 of a CR oscillation output is held constant to the power source AC voltage of different frequency. The potential at this node (a) is compared by a comparator 9 with the potential at a node (b) which corresponds to a peak held value which never varies even in case of a several-cycle hit through a capacitor 7. Then, the hit of AC power supply is detected without setting a voltage nor frequency according to the power supply.
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