| 摘要 |
A device for driving a DC brushless motor by outputting commutation control signals based on voltages induced in the drive windings includes a position detection circuit having low-pass filter circuits that remove a chopping frequency component and have a phase lag of 60-90 DEG at maximum motor rotational speed, a rotational frequency computing section, and a phase correction amount computing section that effects a computation based on the rotational frequency computed by the rotational frequency computing section to set the commutation time point to produce a 30 DEG phase lag in a rotational speed range in which the phase lag falls in the range of 0 DEG to less than 30 DEG and to produce a 90 DEG phase lag in a rotational speed range in which the value of the phase lag falls in the range of 30-90 DEG . The device achieves high efficiency at optimum commutation timing in the high rotational speed region and suppresses vibration and noise in the low rotational speed region.
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