Patent ID: 8154233
Filing Date: 2012-04-10
Classification: H02P

Abstract:
1. A sensorless method for starting a three-phase brushless direct-current motor, comprising: generating a start-up control signal, a start mode selection signal, and a control signal commutation period; switching to a start mode according to the start mode selection signal; implementing a first position aligning procedure to rotate a rotor of the three-phase brushless direct-current motor into a first position according to the start-up control signal and the control signal commutation period, and outputting a commutation signal for a commutation of the three-phase brushless direct-current motor; implementing a second position aligning procedure to rotate the rotor into a second position according to the start-up control signal and the control signal commutation period, and outputting the commutation signal for the commutation of the three-phase brushless direct-current motor, wherein a time interval required for the first position aligning procedure is less than a time interval required for the second position aligning procedure; detecting a zero crossing point of back electromotive forces during each control signal commutation period after the first position aligning procedure and the second position aligning procedure; outputting a sensorless mode selection signal while detecting the zero crossing points of the back electromotive forces during consecutive control signal commutation periods; switching to a sensorless mode according to the sensorless mode selection signal; and detecting a zero crossing point of back electromotive forces in the sensorless mode to determine a starting result of the three-phase brushless direct-current motor.