Importance

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Abstract

Embodiments of the invention avoid erroneous drive current control at the time of a change in the drive waveform for a spindle motor. In one embodiment, a drive current setup section acquires the actual rotational speed from a rotational speed determination section. If the drive waveform is not changed, the feedback system for a first gain determines a drive current. Drive current data corresponding to the drive current is set in a register. If the drive waveform data switches to a curved wave during the next timing cycle, the feedback system does not perform any process, but the same drive current data as for the immediately preceding timing cycle is set in the register. During the next timing cycle, the actual rotational speed is acquired from the rotational speed determination section, and the feedback system for a second gain determines the drive current. When the drive waveform data changes, the feedback system process is skipped once. Therefore, erroneous drive current control can be avoided at the time of a drive waveform change.

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First Claim