Servo circuit

A servo circuit for controlling the positioning of a servo object under servo control to a target position by changing from speed control affording coarse control to position control in the vicinity of the target position, comprising:

• speed detection means for detecting a real speed based on a position signal transferred from the servo object;
• speed error detection means for generating a speed error signal representing a difference between a target speed and the real speed;
• position error detection means for generating a position error signal based on the position signal;
• switching means for switching the connection of the servo object to the speed error detection means or the position error detection means and supplying a control current to the servo object;
• control current detection means for detecting the control current and generating a current sensing signal;
• and
• main processing means for generating and supplying a coarse/fine switching signal to the switching means and controlling the servo object from the coarse, speed control to the position control, said main processing means further comprising gain setting signal preparing means for generating a target speed gain setting signal, a current sensing gain setting signal, and a velocity gain setting signal, and for setting detection gains of each of said gain setting signals at a stage of acceleration control so as to increase in accordance with a decrease of a remaining amount of seek operation corresponding to a remaining number of the tracks, and said main processing means supplying the target speed gain setting signal and reference target speed signal to the speed error detection circuit, and supplying the current sensing gain setting signal and velocity gain setting signal to the speed detection means,
• said speed detection means further comprises a speed detection gain adjustment unit for performing control to vary the detection gains of the velocity and current sensing gain setting signals.