| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve accuracy of detecting a zero-cross point. <P>SOLUTION: A comparator 10 of a phase measuring instrument 100 detects a zero-cross point by comparing an input voltage signal Sv to a zero-cross position, and generates a zero-cross signal Szv based on the detected zero-cross point. A phase synchronization circuit 22 detects a cycle of the zero-cross signal Szv generated by the comparator 10, and generates a synchronization signal synchronized with the zero-cross signal Szv by doubling a frequency that is based on the detected zero-cross signal Szv. Then, a zero-cross regeneration signal Sfv having the same frequency as the zero-cross signal Szv is generated by dividing the frequency of the generated synchronization signal by two. Similarly, a zero-cross regeneration signal Sfi is generated from a current signal Si. As a result of this, a duty ratio in each cycle of the zero-cross regeneration signals Sfv and Sfi becomes 50 percent, and an error in detecting the zero-cross point can be prevented. <P>COPYRIGHT: (C)2012,JPO&INPIT |
