Servo Block; General Description Of Servo Circuits; Optical Pickup Control; Sled Control - Sony DVP-M35 Operation Manual

3. SERVO BLOCK 3-2. Servo Operation at DVD Play
3-1. General Description of Servo Circuits
3-1-1. Optical Pickup Control
Dedicated optical pickups for DVD and for CD and video CD are provided. The focus and
tracking servo gains are automatically adjusted for every disc loading so that the gains are
constant for every disc to be played.
3-1-2. Sled Control
Two pickups for DVD and CD/video CD are placed on the same sled, and the position is
controlled with one sled motor. The sled motor is attached with a speed detector utilizing
the Hall element, and a sled speed fluctuation due to mechanical load variations is minimized
by applying the speed servo control (feedback control).
The sled motor used is a DC motor with a brush.
The servo system circuit is used for both DVD and CD.
3-1-3. Spindle Control
One 3-phase brushless motor controls all disc rotations. The rotation detection pulses (FG:
Frequency Generator) utilizing the Hall element are used for control.
3-1-4. Tilt Control
The optical pickup is controlled so that the optical axis is perpendicular to the disc; when
DVD is played, it is controlled so that the time axis variation (jitter) of RF signal becomes
minimum.
At the start of DVD play (before RF signal is output), optical sensor detects the tilt angle of
disc and the optical pickup is controlled so that the optical axis is perpendicular to the disc.
The servo system circuit is used for both DVD and CD. At DVD, it always performs tilt
operation, but at CD, it operates only during start-up and stops at the tilt position during
playback.
3-1-5. Disc Loading and Chucking
One DC motor drives the tray in-out motions, and chucking of disc.
3-1-6. Disc Judgment
The presence of a disk is judged from the spindle motor spinning start-up time.
Also, the disc size (12cm or 8cm) is judged from the spindle motor speed-up time and disc
data.
3-2-1. Optical Pickup Control
(1) DVD focus servo
The focus error signal output from the optical pickup for DVD (hereinafter referred to
as optical pickup) is entered to the TK-47 board IC006: SSI33P3720A A to D ((_ to
(_)P).
The balance amount and offset amount of the focus error signal is set by IC805 (CPU)
via IC804 of the MB-78 board using the internal register of IC006.
The focus error signal is generated at TK-47 board IC006, amplified, and output from
the FE terminal (_p).
The IC006 FOCUS error (DVD FE) signal is input to the MB-78 board via the flexible
flat cable.
The error signal is switched according to whether the disc type is DVD or CD by the
switch IC452, its signal level is adjusted by IC503 (OP amplifier (_), (_), (_p), and it is
input to the servo DSP IC506 (CXD8730R) _p.
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