Patent ID: 6570351
Filing Date: 2003-05-27
Classification: H02P

Abstract:
A sensorless motor driving apparatus comprising:a position detector for outputting a pulse signal in response to a movement of an object driven by a sensorless motor; a commutation control means which counts a number of pulses of the pulse signal output from the position detector and controls the commutation of the sensorless motor depending upon a count value; and a commutation reference point setting means for setting a commutation reference point employed as a reference point in the counting of the pulses; wherein, each time said sensorless motor is started for the first time after the apparatus has been turned on, said commutation reference point setting means performs a first and a second phase excitation such that a first pulled-in position resulting from the first phase excitation and a second pulled-in position resulting from the second phase excitation become different in electrical angle from each other by a magnitude not equal to either 180Â° or an integral multiple of 180Â°, and said commutation reference point setting means further performs a third phase excitation such that a third pulled-in position resulting from the third phase excitation becomes different in electrical angle from the second pulled-in position by a magnitude not equal to either 180Â° or an integral multiple of 180Â°, and, thereafter, said commutation reference point setting means performs the setting of said commutation reference point when a rotor of said sensorless motor has stopped after said third phase excitation.