Philips LX 3700D, Service Manual

Page: 53 / 90

POWER BOARD
TABLE OF CONTENTS
Internal IC Diagram & Voltage.........................................9-1
Circuit Diagram.............................................................. 9-2
PCB Layout ................................................................... 9-3
Electrical Parts List.........................................................9-4
9-1
ANODE
REF
CATHODE
2.4 k
7.2 k
3.28 k
20 pF
4 k
1 k
800
800
800
20 pF
150
10 k
TL431 EQUIVALENT SCHEMATIC
TOP249 BLOCK DIAGRAM
9-1
SHUTDOWN/
AUTO-RESTART
PWM
COMPARATOR
CLOCK
SAW
HALF
FREQ.
CONTROLLED
TURN-ON
GATE DRIVER
CURRENT LIMIT
COMPARATOR
INTERNAL UV
COMPARATOR
INTERNAL
SUPPLY
5.8 V
4.8 V
SOURCE (S)
S
R
Q
D MAX
STOP
SOFT-
START
-
+
CONTROL (C)
LINE-SENSE (L)
EXTERNAL
CURRENT LIMIT (X)
FREQUENCY (F)
-
+
5.8 V
1 V
IFB
R E
Z C
V C
+
-
LEADING
EDGE
BLANKING
÷ 8
1
HYSTERETIC
THERMAL
SHUTDOWN
SHUNT REGULATOR/
ERROR AMPLIFIER
+
-
DRAIN (D)
ON/OFF
SOFT
START
DC
MAX
V BG
DC
MAX
V
BG
+ V
T
0
OV/UV
V I (LIMIT)
CURRENT
LIMIT
ADJUST
LINE
SENSE
SOFT START
LIGHT LOAD
FREQUENCY
REDUCTION
STOP LOGIC
OSCILLATOR WITH JITTER