| 摘要 |
PURPOSE: To synchronize events relating to timing by utilizing a difference in number of zero crossings between an input line frequency and a nominal line frequency for a prescribed time to compensate for any fluctuation in the input line frequency. CONSTITUTION: A known value is loaded to a divider 22, and a timer/counter 23 provides an output of an interrupt signal accurately for each prescribed time, based on the known value. In the case of loading the known value to the divider 22, a zero-crossing detector/counter 6 counts number of zero crossings. Then a microprocessor-based controller 2 compares the measured number of the zero crossing with an expected number of zero crossings at a nominal line frequency. When the number of zero crossings counted by the zero crossing detector/counter 6 is proper, a corrected division is fed to the divider 22 and an interrupt pulse train of the timer/counter 23 is surely maintained as a correctly synchronized interrupt signal. |
