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1
1.2.3 Carriage servo system
The carriage servo system inputs the output of the low frequency component from the tracking equalizer (information on
the lens position) to the carriage equalizer, and, after the gain is increased to a certain level, outputs the drive signal from
A
the CD of the LSI. This signal is applied to the carriage motor via the driver IC.
Specifically, since it is necessary to move the whole pickup to the FORWARD direction when the lens offset reaches a
certain level during the play mode, the equalizer gain is set to output higher voltage than the carriage motor starting
voltage at this time. In actual operations, a certain threshold level is preset in the servo LSI for the equalizer output, and
only when it exceeds the threshold level, the drive voltage will be output. This can reduce the power consumption. Also,
before the whole pickup starts moving, the equalizer output voltage may exceed the threshold level a few times, due to
such causes as eccentricity of discs. In this case, the output waveform of the drive voltage from the LSI assumes a
pulse-like form.
B
IC201 PE5547A
From
TRACK EQ.
KICK, BRAKE
C
Fig.1.2.7 Block diagram for the carriage servo block
D
E
Fig.1.2.8 Waveforms of the carriage signal
F
12
1
2
DIG.
EQ
CONTROL
REGISTERS
TRACKING DRIVE
(LOW FREQUENCY)
LENS POSITION
DRIVE ON/OFF THRESHOLD
CRG DRIVE
(INSIDE UPD63711GC)
CRG MOTOR VOLTAGE
2
3
IC301 BA5839FP
SD
PWM
111
CARRIAGE MOVED AT THESE POINTS
CX-3195
3
4
LCOP
18
M
24
LCOM
17
CARRIAGE
MOTOR
4
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