Install guide

ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
switching regulator requires + 15 and — 15V for its
operational amplifiers and a 40-kHz square wave signal
for its pulse width modulation section. The normal
control signal for the + 5V switching regulator is regu-
lator-on. When any one of the computer power supplies
five output voltages exceeds its maximum allowable
limit, or when more than 8 amps is drawn from the O to
+ 5V switching regulator, the crowbar signal (CB°)
goes to O volts and initiates an emergency power supply
shutdown. This emergency shutdown is accomplished
by firing a silicon controlled rectifier (SCR) which shorts
the output of the + 5V switching regulator and simulta-
neously causes the regulator-on signal to go low.
(2) 0 to + 5V switching regulator. The O to + 5V
switching regulator is located on the 15V power supply
circuit card assembly. This regulator is commanded by
an analog reference signal (V lamp ref) which originates
in the computer. The output of the regulator follows
the V lamp reference signal. The regulator supplies O to
+ 5V with input variations of +20 to + 30V and load
variations of 0 to 5 amps. Operation of the 0 to + 5V
switching regulator is similar to the + 5V switching
regulator. In addition to current limiting at 8 amps, a
power supply shutdown signal (VLOC°) is sent to the
control and monitor circuitry when the load current
exceeds 8 amps. Asterisk denotes negative logic. The O
to + 5V switching regulator responds to the regulator-
on and CB° signals in the same manner as the + 5V
switching regulator.
(3) +25 V switching regulator. The + 15V switch-
ing regulator is located on the 15V power supply
circuit card assembly. This regulator supplies + 15V
with input variations of +20 to + 30V and load varia-
tions of 1 to 6 amps. The operation of the + 15V
switching regulator is similar to the + 5V switching
regulator.
(4) DC-to-dc converter. The dc-to-dc converter is
located on the 5V power supply circuit card assembly.
The converter receives its input from a + 12V supply at
turn-on and then from the + 15V switching regulator
during normal operation. The converter switches at
approximately 28 kHz and generates square waves of O
to + 20V on a secondary winding of the converter
transformer. These square waves are rectified and filt-
ered and supply +19 and –19V to the 15V precision
supplies. The converter transformer has two additional
secondary windings. The square waves on these wind-
ings are again rectified and filtered, producing a floating
+3V which is used as a boost voltage for the two
switching regulators.
(5) +15 V precision supply. The + 15V precision
supply is located on the 5V
-
power supply circuit card
assembly. The + 15V precision supply is a linear series-
pass type regulator with an input voltage of + 19V
from the DC-to-DC converter and an output voltage of
+ 15V with load variations of 40 to 260 mA.
(6) –15 V precision supply. The –15V precision
supply is located on the 5V power supply circuit card
assembly. The —15V precision supply is a linear series-
pass type regulator with an input voltage of –19V from
the DC-to-DC converter and an output voltage of
–15V with load variations of 0.1 to 1.2 amps.
(7) Control and monitor section. The control and
monitor section consists of MOS logic and voltage
comparators and is located on the 15V power supply
circuit card assembly. The monitor portion consists of
voltage comparators and their associated precision re-
sistor dividers, All the computer power supply output
voltages are compared in the monitor circuit to sepa-
rate high and low voltage references. If any output
voltage is below the low reference, the low voltage
(LV) signal goes high. If any output voltage goes above
the high reference, the crowbar (CB) signal goes high.
When either of these signals goes high, the computer
power supply will shut down. The control portion
contains logic that controls the tumon and turnoff of
the computer power supply. This circuitry initiates
tumon when the + 24V input from the power supply
goes above + 21V. For the first second after initial
tumon, a high signal (PS POR) is sent to the computer
for initialization of the computer and its memory. The
+15 and –15V precision supplies are enabled first,
When the ouput of these supplies reach greater than
+ 10V, the three switching regulators are turned on.
During the time the PS POR is high, only an overvolt-
age (CB
O
) or the computer command (PS 0FF°) can
shut down the computer power supply. During normal
operation, a low voltage (LV), overvoltage (CB°), or the
computer command (PS Off° can turn off the computer
power supply. Anytime the CB
O
or LV signals initiate
the shutdown, a built-in-test magnetic latching indicator
will be set by the flag set’ control signal. The power for
the monitor and control section is supplied by an
auxiliary + 5V regulator that operates directly from the
+ 24V input power. In addition to the control and
voltage monitoring functions, this section also contains
an oscillator that generates a + 30V peak-to-peak, 40-
kHz square wave.
2-5. Power Supply Functional Description. The power
supply assembly converts +20 to + 30V vehicle or
PADS battery power to the following outputs:
115V RMS, 0° phase, 400 Hz, square wave, unregulated
115V RMS, 90° phase, 400 Hz, sine wave, regulated
26V RMS, 90° phase, 400 Hz, sine wave, regulated
±28V, regulated
+ 28V, battery charge, regulated
Figure FO-3 illustrates the power supply assembly
functional Mock diagram. The circuit assemblies within
the power supply assembly are as follows:
RFI filters
2-9