| 摘要 |
<P>PROBLEM TO BE SOLVED: To set the length or timing of a nondrive period adaptivebly, according to the rotational state of a motor. <P>SOLUTION: A counterelectromotive detection circuit 20 detects a zero cross point by comparing a counterelectromotive voltage Vu generated in at least one coil of a motor 110 with the midpoint voltage Vcom of the coil, and outputs a counterelectromotive detection signal BEMF_EDGE. A switching control circuit 30 controls the switching state of a plurality of switching circuits 10, based on the counterelectromotive detection signal BEMF_EDGE, and regulates a current flowing in the coil of the motor 110. A window generating circuit 40 outputs a window signal WINDOW which comes to a specified level during the period of having multiplied the cycle Tp1 of the counterelectromotive detection signal by a specified coefficient, prior to detection of the zero cross point by the counterelectromotive detection circuit 20. The switching control circuit 30 stops the switching of the switching circuit 10, while the window signal WINDOW is on a specified level, thereby putting it in a nondrive period where it gets in a high-impedance state. <P>COPYRIGHT: (C)2008,JPO&INPIT |
