公开(公告)号：JPS6482338A

公开(公告)日：1989-03-28

申请号：JP23866387

申请日：1987-09-25

Applicant: SONY CORP

Inventor： WACHI SHIGEAKI ,  YAMAMOTO SHIRO

IPC: G11B7/09

Abstract: PURPOSE:To simplify a circuit constitution, and also, to prevent a switching noise from being mixed into the signal system of a servo-circuit by adopting a switching control system for an automatic gain servo-circuit. CONSTITUTION:The titled circuit is constituted so that a PWM (Pulse Width Modulation) signal whose pulse width is modulated by the light quantity of a light irradiating to an optical disk is formed, and the amplification gain of servo-circuits 20, 30 is made variable by feedback circuits 14A, 14B which are brought to switching by a pulse duty of this PWM signal. In such a way, the servo-gain can be determined to a correct value without using an expensive AGC amplifier, and also, the generation of a noise caused by a gain control by the switching system, and the deterioration of a servo-characteristic can be eliminated.

公开(公告)号：JPS63316346A

公开(公告)日：1988-12-23

申请号：JP15227187

申请日：1987-06-18

Applicant: SONY CORP

Inventor： WACHI SHIGEAKI ,  YAMAMOTO SHIRO ,  TOSAKA SUSUMU

IPC: G11B5/02 ,  G11B11/10 ,  G11B11/105

Abstract: PURPOSE:To hold a permanent magnet at a prescribed position without always allowing control current to flow after the inverse operation of the permanent magnet by obtaining control current to be applied to a holding coil for holding the permanent magnet based on a magnetic field detecting output consisting of a rotational angle error of the permanent magnet. CONSTITUTION:In a magnetic field impressing device 2 consisting of a magnetic field detecting means 8 for detecting the rotational angle error of the permanent magnet 4 and sending a magnetic field detecting output SH, the holding coil 6 for holding the magnet 4 in a prescribed direction corresponding to recording or erasing operation and kick coil 7 for starting the rotation of the magnet 4, the holding coil 6 is controlled at its drive by a drive controlling means 30A provided with an absolute circuit 34 for sending the absolute output SH1 of a magnetic field detecting output SH, an inverse circuit 36 for inversing the code of the output SH1 in accordance with recording or erasing operation. Control current IV10 to be applied to the coil 6 for holding the permanent magnet 4 is obtained based on the magnetic field detecting output SH consisting of the rotational angle error of the permanent magnet 4.