3-2-2. Sled control
IC302
LBFHPFLA6527N
Sled Drive
24Tracking block7411TESLOFS
SOUTSLDMT+
41122
To sled motor
LPF3885SDCNTSLDMT�
HYCNT
752518
34 33 30 29
HA+HA�HB+HB�
14
IC506TKCFrom FG-43 board,
CXD8730RIC501, IC502
Feedback speed
control by Hall element
Figure 3-10. DVD Sled control
(1) Sled control during playing
During disc playing, namely, when the focus servo and tracking servo are turned on,
the sled servo controls the sled motor so that an objective lens of optical pickup positions
always in the center of movable range of tracking actuator.
The error signal of the sled servo is obtained by amplifying the low frequency components
of TE by the digital filter in the DSP. Consequently, it cannot be observed externally.
The error signal generated internally is output from SOUT ($�P)) via the digital low
pass filter, and input to the sled dr!aP). iver IC302
The sled driver carries out sled speed control constantly, and adds the SOUT voltage to
the control loop.
The Servo DSP IC506 CXD8730R carries out the following controls in the sled servo
block.
(a) Sled error signal generation
Carries out tracking error TE processing to generate the sled error signal.
(b) Sled error amplification
Amplifies the sled error signal by the LPF (Low Pass Filter) composed of the
digital filter and amplifier.
(c) Sled error ON/OFF
Turns ON the sled servo during normal playback, and turns it OFF when the
tracking servo is OFF when playback starts, during search, etc.
� 41 � |
ACEC
