Power Supply Circuit (Dc) - Furuno FR-2115 Service Manual

Power Supply Circuit (DC)

DC PWR Board (03P9246)
The PWR board contains a main-inverter, a sub-inverter, and protectors. The main-inverter
produces +24 V and +32 V (for scanner motor), while the sub-inverter produces –12 V, +12 V,
+32 V, and +140 V from +24 V, output of the main-inverter. +5 V is generated by chopping +24
V. Power fail (P.F.) signal generator outputs "High" signal normally and "Low" signal when the
main-inverter fails. +24 V is adjusted by VR51.
Main-inverter:
With the POWER switch pressed, +12 V regulator, Q1 turns on, and over- and low-voltage
protectors and switching regulator controller are powered up. The protector U1 activates when
ship's main is lower than 19.5 VDC and higher than 42 to 46 VDC. The switching frequency is
adjusted by VR1.
Sub-inverter:
The sub-inverter produces –12 V, +12 V, +32 V, and +140 V from +24 V, the output of the
main-inverter. These lines are not stabilized, but the +24 V line is stabilized by the main-inverter.
The switching frequency is adjusted by VR71.
Protector:
Over-current detector U91in the scanner motor power line (ANT MOTOR line) activates when
the current is 6 A or more for 0.8 seconds. The short circuit protector U72 operates when +140 V
line is short-circuited. The output from the U72 is latched by Q33 and then send to the switching
regulator controller U11.
Power for Scanner Motor:
Rectified +32 VDC is applied to the scanner motor through the ANT MOTOR line, MOTOR(+)
and MOTOR(-). The F/V (Frequency to Voltage) converter U93 receives bearing pulses (BP)
from the scanner unit and outputs DC signal depending on the frequency received. The
comparator Q94 compares the output of the F/V converter with the antenna speed data, 24 rpm
or 42 rpm. If the antenna speed is lower or higher than the rating, the comparator outputs the
signal to control the scanner motor supply voltage. Thus, the motor rotates stably.
The VR91 adjusts the antenna rotation to 24 rpm (no adjuster for 42 rpm). The number of the
antenna rotation can be read on the self-test menu.
The table below summarizes how to select the antenna speed data.
Rotation
24 rpm Removed
42 rpm Removed
JP91 JP92
Removed
Connected
R98
4.7 k ohms Disregarding menu setting
1.2 k ohms Ant. revolution, Radar 3 menu; H
2-27
Menu selection