Description Of Circuit; Alpc (Automatic Laser Power Control) Circuit - LG RH178H Service Manual

DESCRIPTION OF CIRCUIT

1. ALPC (AUTOMATIC LASER POWER CONTROL) CIRCUIT

1-1. BLOCK DIAGRAM
LPM 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 SIG-
NAL DETECTED WITH THE PD FOR FRONT MONITOR
DETECTION IS INPUT THE VOLTAGE FROM THE VPD PIN(123PIN) OR THE FPDM PIN(127PIN), THE REF-
ERENCE 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.
LIC 121
AN22113A
124
APC
LPF
127 FPDM
19 123
VPD
D/A
D/A
D/A
Serial
I/F
D/A
D/A
D/A
Ave
S/H2
Erase
S/H3
VGA
Space
VGA S/H1
40 41 42
SH3 SH2 SH1
4-34
LIC 201
MN103SA6G
M
P
A/D
X
Write
Strategy
S/H
Signal
ADSC