Patent ID: 8269442

Claim:
A method for driving a brushless D.C. motor having a rotor and a plurality of stator windings that define a stator field when driven by a bridge circuit, where a microprocessor drives the bridge circuit using pulse-width modulation logic, the method comprising: triggering a commutation of the stator field; monitoring voltage induced by rotation of rotor in a non-energized stator winding to determine whether the induced voltage reaches, or is below a threshold voltage; determining a delay time between triggering the commutation of the stator field and the voltage reaching, or being below the threshold voltage; and using the determined delay time to establish a triggering time point for a next commutation of the stator field; where a multi-threshold comparator logic is used for the monitoring of the induced voltage, where the multi-threshold comparator logic is integrated in to the microprocessor, and is synchronized with the pulse-width modulation logic, and where the synchronization is produced via a fast shutdown logic integrated within the microprocessor.