Protection Circuit - Ps Oscillator Stop 1 (Thermal) - Sony XM-1502SX Training Manual

Protection Circuit – PS Oscillator Stop 1 (Thermal)
Concept
Refer to Figure 1-9. The power supply oscillator within DC-DC Converter IC901 starts when voltage is applied to
pin 12. This 36kHz oscillator can be stopped for amplifier protection if the voltage at pins 1 or 16 rises to 1.2Vdc.
The protection circuits external to IC901 keep this voltage latched high (oscillator = OFF) when the circuit is
tripped.
TO T901
Q903
REM
POWER
1
ON/OFF
F901 Q901, 902
12V
2
SWITCH
1
GND
THERMAL
POWER
Q808
UNMUTE TO
Q801,802
IC902
DC
DET.
B+
OVER CURRENT
D809
D808
OFFSET
D810
D811
D807
Q809
LED
INHIBIT
FIGURE 1-9 - PROTECTION CIRCUIT 1 - THERMAL
FROM
FROM
OVER
OFFSET
CURRENT
DETECT
CIRCUIT
CIRCUIT
Q813
LED
DRIVE
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
12
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
T901
SEE FIG.1-5
1A125a 11/11/02