Methods and systems of sensing back-electromotive force in electric motors
Abstract:
A method includes driving a selected motor winding to be in a tri-state during a time interval having a finite time length value of a time window, sensing a zero-crossing (ZC) of an oscillating back electromotive force induced in the motor winding during the time window in which the motor winding is in the tri-state, and producing a ZC sensing signal, which has a first edge at a first time instant at the sensed ZC and a second edge at a second time instant separated from the first time instant by a half oscillation of the oscillating back electromotive force, detecting a phase of a current flowing in the motor winding at a time instant time-shifted with respect to the second time instant of the second edge of the ZC sensing signal, and adjusting the finite time length value based on the detected phase of the current.
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