| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a synchronous control method, a synchronous control circuit and a communication device capable of detecting precisely a zero cross point of a sine wave alternating current voltage, without depending on a sampling interval. <P>SOLUTION: This method/circuit is provided with a zero cross point time calculation process for calculating a time of the zero cross point P9 of the sine wave alternating current voltage, by sampling the sine wave alternating current voltage periodically, and by dividing proportionally the sampling interval, using a sample value P1 before inversion of polarity and a sample value P2 after the inversion of polarity, to be synchronized with the calculated time of the zero cross point. A sampling frequency for an A/D converter is made low thereby, and voltage measuring resolution is enhanced by this manner. The communication device is constituted to transmit information by superimposing a synchronized unbalanced voltage on the sine wave alternating current voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT |
