Determining commutation position for a sensorless permanent magnet brushless motor at low or zero speed using an asymmetric drive pattern

摘要

A system is disclosed for controlling motor switching in a sensorless BLDC motor having a set of three stator windings. A controller unit includes a control signal generator, a memory device, a processing unit, a signal acquisition device, and an analog-to-digital converter. A power stage having a plurality of switches receives a control signal from the control signal generator and a power signal from a power source. The power stage drives two windings of the set of three stator windings with an asymmetric pulse width modulation signal and leaves one stator of the three stator windings undriven. The processing unit acquires a demodulated measured voltage on the undriven winding. The processing unit also communicates with the power stage to change which two windings of the three stator windings are driven when the demodulated measured voltage surpasses a threshold.

主权项

1. Method of controlling motor switching, the method comprising the steps of:
driving an asymmetric pulse width modulated signal on two windings of a set of three windings; measuring a voltage of an undriven winding of the set of three windings; demodulating the measured voltage; and changing which two windings are driven when the demodulated measured voltage exceeds a threshold.