Description Of Circuit; Alpc Circuit - LG GSA-H20A Service Manual

1. ALPC (Automatic Laser Power Control) Circuit
1-1. Block Diagram
CN 101
VREFPD
Optical
Pick-up
LPC-812R
FM
LD PD
LDD
1-2. ALPC (Automatic Laser Power Control) Circuit Operation
The ALPC block detects the laser output power of the front monitor. The power signal detected with the PD for front monitor
detection is input the voltage from the VPD pin(123Pin), the reference signal of the input signal is input from the VREFPD
pin(124Pin). The ALPC block generates the singals from the input laser power signals in the following detection systems.
This block has four detection paths:All average value path, multi pulse average/peak value detection path, erase/bottom
value detection path, space/playback power value detection path.

DESCRIPTION OF CIRCUIT

IC 121
124
APC
19 123
VPD
D/A
D/A
D/A
D/A
D/A
D/A
AN22117A
LPF
VGA
VGA
40
SH3
Serial
I/F
Ave
S/H2
M
Erase
P
S/H3
X
Space
S/H1
41
42
SH1
SH2
IC 201
MN103SB4G
A/D
Write
Strategy
S/H
Signal
ADSC
49