| 摘要 |
PROBLEM TO BE SOLVED: To drive a brushless motor at low rotational speed while suppressing the occurrence of a loss of synchronism, in a brushless motor driver in which a pulse voltage application phase is switched according to position information based on a pulse induction voltage induced in a non-conduction phase.SOLUTION: When a motor rotational speed becomes unable to reduce to a target rotational speed by standard rectangular wave drive, control is shift to thinning control in which the detection of position information of the brushless motor is thinned at a rate of once per N pulses, instead of the position information detection on a pulse-by-pulse basis. In the thinning control, in a period not detecting the position information, it is possible to set a duty ratio to be lower than a lower limit value Dmin necessary for the position information detection, so as to control the duty ratio to be an average duty ratio Dav lower than the lower limit value Dmin. Further, when the motor rotational speed becomes unable to reduce to the target rotational speed even under the thinning control, the switchover timing of the pulse voltage application phase is advanced. |
