Patent ID: 9590543
Date: 2017-03-07
CPC Classifications: H02P

Claim:
1. A drive device for a sensorless brushless DC motor comprising: a drive circuit that drives the sensorless brushless DC motor by alternating, with a constant cycle, an energizing pattern for determining a rotation position of a rotor of the sensorless brushless DC motor; a detection circuit that detects a zero-cross signal indicating alternation of a phase of the rotor; and a processor that calculates a synchronization determination rate as a percentage by dividing the number of zero-cross signals detected by the detection circuit in a predetermined sampling period by the maximum number to be potentially obtained in that sampling period and controls a PWM (Pulse Width Modulation) drive duty to be supplied to the drive circuit for controlling a driving current supplied from the drive circuit to the sensorless brushless DC motor so that the calculated synchronization determination rate is in a target range.