Volt Regulator Module A3

TM 11-6625-667-45

be gated by counter reset gate A2M15A. This

performs an isolating function in the collector

action also gates a counter reset signal through

circuit. The emitter output is fed into a filter

gates A2M18A and A2Q5/A2Q6 to the coun-

consisting of inductor A3L1 and capacitors

ter. Both counter reset gates are inhibited

A3C2 and A3C6. Diode VR1 provides regula-

when readout control A2FF7 is set by an ac-

tion at the output of the filter if the voltage

ceptable count. A constant readout (ACCEPT

increases above 6.3 volts. At this point, the

or REJECT) is maintained by the reply rate

voltage is normally 5.6 volts (approximately).

evaluator until the PUSH ON TEST switch is

Additional filtering is performed by the action

released.

of capacitors C7, C8, and C9.

b. Square Wave Oscillator A8Q10/A3Q11

c. Prf Counting. The prf counter controls

(fig. 8-39). This square wave oscillator con-

the operation of time-decoded video enable

trols the operation of series power regulator

A2SS2. It enables this one-shot for the initial

A3Q1. Its operating frequency is dependent

64 prf periods. After this time, it disables

on the load, and is controlled by the action of

A2SS2 until the counter is reset by the release

constant current amplifier A3Q7/A3Q8. The

o f the PUSH TO TEST switch. When the

square wave output, applied through amplifier

PUSH ON TEST switch is activated, each prf

A3Q9 to emitter follower A3Q3, is held off

pulse is gated by prf count gate 1 (A2M16A)

one-fifth more than on; therefore, this action

and coupled by inverter A2M16C to trigger

maintains approximately 5.6 volts at the emit-

flip-flop A2FF8. On the count of 64, flip-flop

ter of series power regulator A3Q1 by effec-

A2FF14 goes high and gates on prf count gate

tively dividing the 28-volt dc input.

2. This action disables prf count gate 1 and

one-shot A2SS2 until the prf counter is reset

c. Constant Current Circuit. The constant

by the release and activation of PUSH TO

current circuit consists of constant current am-

TEST switch; therefore, additional time-de-

plifier A3Q7/A3Q8, limiting amplifier A3Q2

coded video counts are inhibited.

/ A 3 Q 4 , and differential amplifier A3Q12/

A3Q13. This circuit provides a constant cur-

rent source for the square wave oscillator. The

5.1-4. 5-Volt Regulator Module A3

constant current amplifier operation is con-

(fig. 8-39)

trolled by the limiting and differential ampli-

T h i s voltage regulator provides the power

fiers. Output current limiting is adjusted with,

source to the micrologic circuits in mode 4

control A3R3 (fig. 8-42). The setting of this

modules Al and A2. Regulation is performed

control establishes the base bias of stage A3Q2

by series power regulator A3Q1, and its con-

and, in turn, its conduction. The collector out-

ducting is controlled by the operation of square

put of stage A3Q4 is coupled by diode A3CR3

wave oscillator A3Q10A/A3Qll through am-

to the common emitter circuit of constant cur-

plifiers A3Q3 and A3Q9. The operation of

rent amplifier A3Q7/A3Q8. Adjusting con-

the oscillator is controlled by a constant cur-

trol A3R3 will establish a regulated emitter

rent circuit. Transistors A3Q5 and A3Q6 form

b i a s at A3Q7/A3Q8. Differential amplifier

a + 12-volt bias protection circuit. If the +12-

A2Q12/A3Q13 establishes the base bias at

volt bias is not present, this circuit stops the

stages A3Q7/A3Q8. Control A3R24 is used

conduction of A3Q1, thus preventing regula-

to adjust the differential amplifier (A3Q7/

tor circuit damage because of loss of bias volt-

A43Q8) operation and, in turn, the regulator

age.

output voltage. If a short circuit occurs at the

regulator output, the current limiting stages

a. Series Power Regulator A8Q1. This stage

serve as a load, thereby preventing power sup-

operates in series with the 28-volt source and

ply damage. If the regulator input voltage

mode 4 modules (Al and A2). Its conduction

changes, it is sensed by the differential ampli-

determines the source output voltage and is

fier. This amplifier causes the square wave os-

controlled by square wave oscillator A3Q10/

cillator to change frequency through the con-

A3Q11 (fig. 8-39). Diode A3CR1 (fig. 8-42)

Change 1

5.1-4