FOSO
FMSO
TRSO
DMSO
A B C D E F RFO
IOA
LDO2
LDO2
MD11
Switch circuit
APC circuit
Main axis
control detect
circuit
Main axis
electric
machine
Feed
electric
machine
XS101
AM5888
MT1389
Open/close
circuit
TK-
TK+
FC+
FC-
SL+
SL-
SP-
SP+
1
23
4
26
15
16
14
13
17
18
12
11
Figure 3.2.2.1 Servo circuit block diagram
2. Working principle: after power on or close to proper position, loader laser head begins to reset;
after laser head reaches proper position, detect switch will give a signal to Mt1389, Mt1389 begins to
output focus, main axis and light emission signals, machine begins to rotate, laser head begins to
identify disc information and decide whether disc is CD or DVD according to disc information to facilitate
to output level from IOA pin to make disc switch circuit and laser head PD IC make the relevant control
action. At the same time, Mt1389 adjusts laser output power through laser power control circuit.
After loader reading disc information, A, B, C, D, E, F signals are formed through photo-electric
conversion and sent out to Mt1389 (DVD only has A, B, C, D signals), and then inputted from pin 2~11,
18, 19 of MT1389. After being amplified and processed by the pre-amplifier inside MT1389, now signals
are separated to two part s for processing inside Mt1389. One part, through addition inside Mt1389 and
amplifying and subtraction circuit, produces servo error signal, after being processed by digital servo
signal circuit, corresponding servo control signals form to output FOO, TRO, DMO, FMO digital
servoControl signals from pin 42, pin 41, pin 37, pin 38 of Mt1389 respectively, and FOSO, TRSO,
DMSO, FMSO, through integration circuit composed by resistor capacitor, and send to servo driver
circuit for amplification to bring along focus winding, trace winding, main axis electric machine and feed
electric machine after drive amplification. Among these, focus and trace servo are used to correct
objective position accurately; feed servo is used to bring along laser head to make radial large-scale
move which belongs to the preliminary adjustment to laser head position; and main axis servo is used to
control main axis electric machine to make it read signals in means of constant linear velocity and
bringAlong disc to rotate. After processing of amplification by VGA voltage control amplifier and
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