| 摘要 |
PROBLEM TO BE SOLVED: To continue position detection operation by preventing stopping and out-of-step without any interference with rotation control even in case of being unable to detect position of a rotor in a brushless motor. SOLUTION: In carrying out rotation control of a brushless motor 4, the voltage of an armature winding in the motor is compared with reference voltage by a position detection part 10 for attainment of a position detection signal D. The detection signal D is inputted into a control circuit 11 to detect the position of a rotor 4a in the motor, and based on the position detection, current- carrying of the winding voltage of the motor is switched. At this point, the control circuit 11 counts time between position detection intervals. Based on the counted time, the time corresponding to a phase angle 30 is predicted from the position detection and position detection at the predicted time is checked. In case of no position, present current-carrying switching is conducted based on a previous switching time of current-carrying. In case of no position, the control circuit 11 adds the content of position detection register by one. For presence of position detection, the circuit subtracts the content of the register by one. If the content of the register is the prescribed value or more, applied voltage of the motor is decreased to the prescribed value. |
