| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a sensor-less motor drive circuit without any burden such as an increase in the number of externally installed parts or an increase in the area of an IC chip and producing a noise mask signal automatically following variations in rotational speed, by using a motor rotation signal and a simple counter. <P>SOLUTION: A slope signal synchronous with a resultant frequency signal formed on the basis of counter electromotive force comparison signal is produced, and a noise mask signal is produced in accordance with a predetermined level of the slope signal or a varying point of the resultant frequency signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
