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1
3) Carriage servo system
A
The carriage servo is input the output from low frequency
number composite of tracking equalizer (position
information of lens) to carriage equalizer, and after
acquiring fixed gain, it outputs drive signal from LSI. The
signal is impressed to carriage motor via driver IC.
To be more precise, since it is necessary to move the
entire pick-up to forward direction when lens off-set during
playing reaches to certain level, the gain of equalizer is
set to generate higher voltage than start-up voltage of
carriage motor at that time. In addition, actual operation is
set to fix a certain threshold for equalizer output inside
B
servo LSI, and to output the drive voltage only when the
level of equalizer output is over that fixed level. In that
way, power consumption is reduced. Moreover, according
to decentering of a disc, the level of equalizer output
voltage may cross threshold level several times before the
entire pick-up starts to move. At that time, output
waveform of drive voltage from LSI is pulse state.
C
IC201 UPD63763AGJ,UPD63761AGJ
FROM
DIG.
TRACK. EQ
EQ
KICK, BRAKE
REGISTERS
D
Fig.11 Carriage servo block diagramFig 16: Carriage servo block diagram
TRACKING DRIVE
(LOW FREQUENCY)
LENS POSITION
CRG DRIVE
E
(INSIDE UPD63711GC)
CRG MOTOR VOLTAGE
F
10
1
2
SD
R321
CONTROL
DAC
105
27K
DRIVE ON/OFF THRESHOL D
Carriage is moved by these points.
Fig.12 Carriage signal waveform
2
3
IC302
BD7962FM
COM
19
CARRIAGE
33
M
MOTOR
20
COP
32
CX-3168
3
4
4
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