| 摘要 |
PROBLEM TO BE SOLVED: To lessen vibration and noise and prevent a step-out by switching the excitation of armature windings properly. SOLUTION: A brushless motor 3 is controlled by a method wherein the brushless motor 3 is rotated with application voltage to the motor being varied by changing a duty ratio of chopping and the excitation of armature windings of the motor is switched based on the detection of position of a rotor 3a of the motor 3. In this case, induced voltage in each of the armature windings and half of a reference voltage Vdc/2 from a reference voltage generating circuit 5a are compared with each other by a comparing circuit 5b and the comparison result which is a position signal of a position detecting point is input into a control circuit 10. Based on the time of one cycle measured at a former position detection and the duty ratio of chopping, the control circuit 10 calculates a standard value of a position detecting interval and then compares a position detecting interval obtained when the position is detected this time with the calculated standard value of a position detecting interval. When the position detecting interval obtained when the position is detected this time is larger than the standard value, the position detecting point this time is put back by a specified value and then an excitation switching timing of the brushless motor 3 is calculated based on the corrected position detecting point. |
