Description Of Circuit; Alpc (Automatic Laser Power Control) Circuit - LG RHT497H Service Manual

1. ALPC (AUTOMATIC LASER POWER CONTROL) CIRCUIT
1-1. Block Diagram
LPM101
VREFPD
Optical
Pick-up
HOP-7232TL
19
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 aver-
age/peak value detection path, erase/bottom value detection path, space/playback power value detection path.

DESCRIPTION OF CIRCUIT

LIC101
AN22117A
124
APC
LPF
123
FPD
D/A
D/A
D/A
Serial
I/F
D/A
D/A
D/A
Ave
S/H2
Erase
S/H3
VGA
Space
S/H1
VGA
40 41 42
SH3 SH2 SH1
4-34
LIC201
MN103SC7G
M
P
A/D
X
Write
Strategy
S/H
Signal
ADSC