Power Supply Sw Circuit - Furuno FS-1503 Service Manual

2.6 Power Supply SW Circuit

Power supply SW circuit is included in PA/FIL board.
When the power switch is turned on, a relay K1 is made ON by Q1 and power is supplied
to circuits. To protect the contact of K1 against the rush current at power on, a delay cir-
cuit is provided. That is, C10 is charged through Q11 which is switched on by Q3 at
power on, and then K1 is turned on. When K1 is ON, Q11 is switched OFF, and power is
supplied through K1. Turn-on of K1 is delayed until C9 is charged.
F2 (1.35 A)
TB1
+ 13.6 V
TB2
– 13.6 V
The allowable input voltage of power supply is from about +8 V to +17 V. (Rating volt-
age: 13.6 V ± 15 %) The upper limit +17V is determined by a over-voltage detector U1
and a switch Q2 and the lower limit +8 V is determined by the drive voltage of the relay
K1. F1 and F2 are poly-switches. The poly-switch works as a fuse that cuts off (trip) cir-
cuit with a Joule heat generated by the current flowing through it. Once the switch be-
comes off, it does not recover until it cools down while power supply is off.
Note) The negative line of the power supply and the negative ground of the circuit
boards (chassis) shares a common earth. When a floating ground that separates the
negative line and the negative ground is needed, an optional SW REG board is to be
added.
TX/RX PCB
CR1 Q11
R2
R1
K1
C10
R4
U1
Q2
Q3
Overvolt.
Detector
E
POWER ON
POWER SW
Figure 2-20 Power Supply Circuit
2-26
JP1
BK + 12V
JP2
BK – 12V
+13.6 V
PA
R12
F1 (4 A) FL2
C13 C14
C49 to 52
K1
E
Q1
C9
12 V
J1
J2
J1
+12 V
SW REG
(OPTION)
-12 V
J3 J4
J7
12 V