| 摘要 |
PURPOSE: To avoid a position detection error caused by noises, switch the current application to armature windings properly, reduce the vibration and noises and avoid a step out. CONSTITUTION: When a DC power supply Vdc is switched by an inverter unit 4 and is applied to the armature windings of a brushless motor 3, the inverter unit 4 is driven in accordance with the detection of the position of the rotor 3a of the brushless motor 3 to switch the current application to the armature windings. An induced voltage induced in the armature winding is compared by a comparator 5 with the half value of the reference voltage Vdc from a reference voltage generating circuit 5a and a position signal which is changed at the cross point of the comparison results is inputted to a controller 10 which counts the intervals between the changing points (position detection points) of position signals and calculates noise mask periods based upon the counted time intervals and the position detection is not performed during the noise mask periods. |
