Detection of a perturbation in the synchronization of the driving in a tripolar mode of a brushless, sensorless DC motor for minimizing torque ripple

摘要

A method of detecting the relative position of the rotor of a sensorless DC brushless motor driven in a tripolar mode includes the step of monitoring the voltage difference between the drive voltage that is applied to at least one winding of the motor and the voltage drop on a resistive portion of the drive current path through the same winding. The voltage drop may be detected between the two current terminals of an MOS power device of the driving bridge of the winding. The monitoring of the voltage difference is used to signal a perturbation from a pre-existing condition of correct synchronization of the phase switchings during a driving phase in a tripolar mode of the motor. Such information may be used by the driving system to switch to one of a bipolar mode, a unipolar mode or a tripolar mode with momentary drive interruptions, until restoring a correct synchronization condition and/or attain a correct rotating speed.