Abstract: A servo control device includes: a phase compensator configured to generate a plurality of types of control values for controlling a driver based on a signal output from an optical pickup, and output the control values; and a transfer data generator configured to serially transfer the control values to the driver. The phase compensator sends, to the transfer data generator, a notification that the phase compensator has output a control value which needs to be sent with a reduced delay among the control values. In response to the notification, the transfer data generator determines whether or not the transfer data generator is transferring one of the control values, and if the transfer data generator is not transferring one of the control values, the transfer data generator starts transferring a control value associated with the notification among the control values.

Abstract: A sensorless motor drive device has: a first operation mode of generating current waveforms including non-energizing times based on a first rotor position signal generated by detecting zero crossings in windings of a motor as a signal indicating the rotor position of the motor, and supplying currents to the windings of the motor according to the current waveforms; and a second operation mode of generating current waveforms including no non-energizing time based on a second rotor position signal generated without use of zero crossings as the signal indicating the rotor position of the motor, and supplying currents to the windings of the motor according to the current waveforms. The first and second operation modes can be switched to each other.