Sony XM-1502SX Training Manual page 8

Pulse Power Supply – Oscillator / Output
Refer to Figure 1-4 (oscillator) and 1-5 (driver). The switching power supply consists of the oscillator within
IC901, the MOSFET drivers (Q904-8) transistors and the multiple winding transformer (T901) that it feeds.
TO T901
Q903
REM
POWER
1
ON/OFF
F901 Q901, 902
12V 2
B+
SWITCH
GND 1
D808
THERMAL
POWER
Q808
Circuit Operation
IC901's internal oscillator starts and produces a 36kHz output at pins 9 and 10 when four conditions are met:
1. Vcc is applied to IC901/pins 8, 11 and 12 of at least 5.9Vdc (normally = battery voltage).
2. Protection Latch 1 and 2 applied to IC901/pin 1 is less than 1.2Vdc.
3. Thermal Sensing voltage applied to IC901/pin 16 is less than 1.2Vdc.
4. Feedback for regulation at IC901/pin 4 (not shown) is less than 3Vdc.
TO Q801,802
IC902
DC
DET.
OVER CURRENT
D809
OFFSET
D810
D811
D807
Q809
LED
INHIBIT
FIGURE 1-4 - POWER SUPPLY
FROM
FROM
OVER
OFFSET
CURRENT
DETECT
CIRCUIT
CIRCUIT
Q813
LED
DRIVE
OSC.
START
Q812 PROT.
LATCH
Q811
LED
DRIVE
Q810
PROT.
LATCH
5.0V
D803
STOP
1.2V
REF.
THP802-3,
TH801-813
0.2V
TEMP. DET.
TEMP LATCH
0V
6
1. Car Power Amplifier
SW.+12V
11
Q904/5
12 10
+12V
REF.
FROM
REG.
F901
8
Q906/7
9
OSC.
14
STOP
1
2
15
IC901
16
DC-DC
CONVERTER
3
1A125
T901
11/12/02