Advertisement
1. APC (Automatic Power Control) Circuit
1-1. APC Circuit Constitution
DVD-LD(LASER DIODE)
LD
Monitor
Diode
CD-LD(LASER DIODE)
LD
Monitor
Diode
1-2. APC Circuit Operation
It drives the LD to the constant current and adjusts the LD input current , so that the output current is
constant.
IC301 (SSI3723) Pin
IC301 (SSI3723) Pin
The detect current from the monitor diode converts to the I/V (Current/Voltage) at the external resistor.
Beforehand, it adjusts a fixed level over for a standard GND.
If this voltage inputs to the PD IN (IC301 Pin 23, 24), it is amplified about 36.4 times (about 31.2dB).
So this voltage outputs from the LD OUT (IC301 Pin 21, 22).
The LD driving element (Q302/Q303) uses the TR more than 200h fe , and controls LD OUT (IC301 Pin 21,
22) connected to the base of Q302/Q303.
The APC control for the each DVD/CD sets Register of the IC301 (SSI3723) according to Disc in the
µ-COM.
DESCRIPTION OF CIRCUIT
PN301
DVD-
18
MD
DVD-
19
VR
DVD-
16
LD
CD-
22
PD
21
CD-VR
CD-
27
LD
PICK-UP Unit
,
: PD IN, Monitor Input of Laser diode APC
23
24
22
21
,
: LD OUT, External Current Driver Control output of the LD (Laser Diode)
Vcc
5V
R317
C332
R318
Q302
Vcc
5V
C331
R315
R316
Q303
IC301 SSI3723
23
DVD PD
DVD LD
21
C335
24
CD PD
22
CD LD
C333
13
Advertisement
