| 摘要 |
PROBLEM TO BE SOLVED: To detect a zero-crossing point by utilizing a microcomputer even if an exclusive zero-crossing circuit is not used. SOLUTION: A controller has a full-wave rectifier 2 which rectifies a commercial power supply voltage, a voltage converter 5 which transforms the rectified power supply voltage into a voltage of several volts, an A/D converter 7a which converts the voltage transformed by the voltage converter 5 into a digital value with a certain time interval and a microcomputer 7 which processes the output of the A/D converter 7a to perform various control. The controller detects a zero-crossing point at which the output of the A/D converter 7a is zero and the state of the output is transferred from a descending direction to an ascending direction and, if the zero-output of the A/D converter 7a is continued, detects a time for which the zero-output is continued. |
