| 摘要 |
A method of controlling a brushless DC motor of the type having a stator (1), comprising a stator winding (3) excitable to generate a stator magnetic field, and a rotor (2), arranged to rotate with respect to the stator (1) and comprising permanently magnetised material arranged to generate a rotor magnetic field to interact with the stator magnetic field to produce rotation of the rotor. The method comprises the steps of driving current through the stator winding (3) to generate a stator magnetic field to interact with the rotor magnetic field, detecting rotor (2) position with respect to the stator (1), and cyclically commutating the stator winding current (90) according to rotor (2) position as the rotor (2) rotates. Each commutation cycle includes a drive portion (13) during which current (90) is driven through the stator winding (3) in one sense and at the end of which the driving of current (90) in said sense is ceased. The method further comprises the steps of during an initial portion of each drive portion (13), driving current through the winding (3) such that the magnitude of the winding current (90) increases and during an end portion (82) of each drive portion (13), actively reducing the magnitude of the winding current (90). This method reduces undesirable current spikes and voltage spikes (or back EMF) caused by the switching off of current at the end of each drive portion. |
