Power Board - Philips LX700/21S/22S/25S Service Manual

7-1

POWER BOARD

TABLE OF CONTENTS
Internal IC Diagram........................................................7-1
Circuit Diagram ................................................................ 7-2
PCB Layout.......................................................................7-3
Electrical Parts List..........................................................7-4
TL431 EQUIVALENT SCHEMATIC
CATHODE
REF
3.28 k
20 pF
2.4 k
7.2 k
800
ANODE
TOP249 BLOCK DIAGRAM
V C
CONTROL (C)
Z C
SHUNT REGULATOR/
ERROR AMPLIFIER
+
- 5.8 V
-
4.8 V
5.8 V
+
INTERNAL UV
I FB
COMPARATOR
V I (LIMIT)
CURRENT
SOFT
LIMIT
START
ADJUST
ON/OFF
V BG + V T
EXTERNAL
CURRENT LIMIT (X)
STOP LOGIC
1 V
LINE-SENSE (L)
V BG
STOP SOFT-
START
OV/UV
LINE D MAX
DC
DC
SENSE
MAX
MAX
CLOCK
HALF
SAW
FREQ.
FREQUENCY (F)
OSCILLATOR WITH JITTER
LIGHT LOAD
FREQUENCY
R E
REDUCTION
7-1
800
800
20 pF
150
4 k
10 k
1 k
0
INTERNAL
1 SUPPLY
SOFT START
-
÷ 8
+
SHUTDOWN/
AUTO-RESTART CURRENT LIMIT
COMPARATOR
HYSTERETIC
THERMAL
SHUTDOWN
CONTROLLED
TURN-ON
GATE DRIVER
S Q
-
LEADING
EDGE
R
+ BLANKING
PWM
COMPARATOR
DRAIN (D)
SOURCE (S)