Patent ID: 8054023

Claim:
A method of driving an electric motor in a pulse width modulation (PWM) mode comprising: tristating a motor winding of the electric motor during a time window to detect a zero-cross of the back electromotive force (BEMF) induced in the motor winding; monitoring a voltage on the tristated motor winding during an unmasked portion of the time window; detecting during the time window a zero-cross event of the induced BEMF; verifying whether the zero-cross event occurred during the unmasked portion of the time window; modifying a duration of the time window and a duration of the unmasked portion of the time window based upon the verification of the zero-cross event; defining a safety interval in the unmasked time window; and modifying the duration of the time window and of the unmasked portion of the time window based upon whether the zero-cross event is detected during the safety interval.