| 摘要 |
PURPOSE:To obtain pulses of a prescribed period with either 50 or 60Hz frequency commercial power supply, by selecting pulses at an integer multiple of 1/20sec among the pulses in response to the commercial power supply frequency. CONSTITUTION:An output voltage of a transformer T is rectified at a rectifier circuit A and applied to a transistor (TR). The output of the TR is given to one-shot pulse generators W1, W2, which opens a gate circuit G at each 1/20sec and is synchronized by the incoming pulse. This is due to the fact that the phase of both 50 and 60Hz is coincident at each 1/20sec, since because the period of the pulse for 50Hz is 1/100sec and the period for 60Hz is 1/120sec. Thus, no frequency changeover is required by picking up a pulse at each 1/20sec from the both and using the pulse as a synchronizing pulse. Then, the synchronizing pulse having 1/20sec period only is produced from a circuit G and synchronism is applied to a frequency division circuit D1. Further, the period is permitted at every 1/20n (where; n=2, 3...) second. |
