PURPOSE: To simultaneously decrease settling characteristic and seek noise and to increase a stopping torque by increasing a duty ratio in latter half of chopping control of an exciting phase larger than that in former half if a head shifter is disposed on a track to be recorded with information of an information recording disk.
CONSTITUTION: A stepper high voltage signal 8 becomes an 'H' level by a pulse input as a step signal 6, and an exciting phase is excited during 3msec while moving one track. When it is moved to one track, it becomes an 'L' level, and a chopping control is executed at 40% of duty ratio (D ratio) for 3msec. Then, a chopping is performed at 70% of the D ratio during 3msec, and the H level is then maintained. Thus, settling characteristic indicated by a solid line is obtained. Since it is excited at 40% of the D ratio, a seek noise is reduced, and since the period of time when the signal 8 is ON is long, a stopping torque is increased, and the position holding force of a head unit is improved. It may be gradually raised at 60, 70, 80% of the D ratio like a chopper 3.
MASUDA ATSUSHI
KUMAGAI KAZUNORI
