| 摘要 |
PURPOSE:To detect the frequency of an AC power source by itself and to change a control time, by calculating the frequency of the AC power source from a counter which starts at the time of zero-crossing and stops at the next time of the zero-crossing, and deciding the control time based on the frequency. CONSTITUTION:The counter which starts at the time of the zero-crossing and stops at the next time of the zero-crossing, an arithmetic means which calculates the frequency of the AC power source from the counted value of the counter, and a means which decides the control time based on a calculated frequency, are provided. And, to supply set power to a load, a power source is supplied by turning ON a load switching device after a prescribed time (control time) from starting the zero-crossing. When the frequency of the AC power source is changed, the control time is changed so as to set a phase angle at the same level by detecting the frequency of the power source by the counter and the arithmetic means.
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