Philips MX3550D/37S Service Manual page 57

10-1
POWER BOARD
TABLE OF CONTENTS
Internal IC Diagram........................................................10-1
Circuit Diagram .............................................................. 10-2
PCB Layout.....................................................................10-3
Electrical Parts List..........................................................10-4
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
LIMIT SOFT
START
ADJUST
ON/OFF
V BG + V T
EXTERNAL
CURRENT LIMIT (X)
STOP LOGIC
LINE-SENSE (L) 1 V
V BG
STOP SOFT-
OV/UV START
D MAX
LINE
DC
DC
SENSE
MAX
MAX
CLOCK
HALF
SAW
FREQ.
FREQUENCY (F)
OSCILLATOR WITH JITTER
LIGHT LOAD
FREQUENCY
R E
REDUCTION
10-1
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)