Dc Power Supply Module A14, 150- Volt, Stage Analysis

TM 11-6625-667-45/NAVSHlPS 0969-249-8010/NAVAIR 16-30APM123-2/TO 33A1-3-367-22

b. Sguare Wave Oscillator Functioning. Two

responding voltage change is coupled by Q2 to the

saturable-core type square wave oscillator circuits

base of Q1, decreasing the conduction of Q1, and

produce the square wave voltage. Transistors Q1

effectively increasing the voltage drop across it.

and Q2 form one oscillator and transistors Q3 and

A decrease in the input voltage will cause an oppo-

Q4 the other. The operating voltage of the oscil-

site effect. Stage Q3 will conduct less and cause Q1

lator circuits is supplied by the +28-volt input.

to conduct more, and the voltage drop of Q1 will

One transistor in each oscillator conducts and

then decrease. These voltage changes are propor-

tional to the input voltage change. Thus, the

forms the first one-half cycle of the square wave.

The second transistor in each oscillator conducts

emitter voltage of Q1 is maintained at 12 volts.

and forms the second one-half cycle. Oscillation

Regulator diode VR1 serves as overload protec-

tion for Q1. If the regulator output lend increases

depends primarily on the characteristics of trans-

former T1 and the value of the dc voltage input

abnormally, VR1 provides a current path to the

to the transistors. Changes in transistor collector-

input voltage source. Its conduction through resis-

emitter currents, and currents flowing in the pri-

tor R2 decreases the conduction of Q3 and of Q1 in

mary windings of the transformer, cause changes

turn.

in transformer flux. This changing flux generates

b. 12-Volt Rcgulator. This regulator uses a

voltages in the feedback and output. windings of

18-volt input from the 150-volt. dc power supply

the transformer. Voltages from the feedback wind-

(module A14). A sing]e transistor stage (Q4) is

ings provide the regenerative action required to

used. which is always conducting through R8. Its

maintain oscillation. The output voltage from the

base bias is regulated by the action of diode CR6

oscillators is a square wave and is coupled by sepa-

and regulator diodes VR4 and VR5. This arrange-

rate windings to the bridge rectifiers.

ment maintains constant emitter conduction

c. 18-Volt and 150-Volt Dc Bridge Rectifier

through R8, which provides a 6-volt drop. Thus,

a regulated 12-volt. out put is taken from the

Functioning. The rectified output of the 18-volt

bridge rectifier is applied to the 12-volt regula-

emitter of Q-1.

tor in module A13. The rectified output of the

150-volt dc bridge rectifier is applied to the trans-

2-17. Dc Power Supply Module A14, 150-

mitter (A16) also used to control the input voltage

Volt, Stage Analysis

regulator.

(fig. 8-6)

d. Input Voltage Regulator Functioning. This

a. General. The 150-volt dc power supply mod-

regulator consists of transistors Q5, Q6, and Q7.

ule is a dc-to-dc converter type find provides 150

It regulates the operating voltage of the saturable-

volts dc and 18 volts dc. Input power for this

core, square wave oscillators. The 150-volt bridge

unit is provided by the +28 volts dc from either

rectifier output is sensed at the base of Q7 through

the 28-volt. power supply or an external 28-volt

source. Two oscillator circuits, containing tran-

resistors R7 and R8. The regulator output is ad-

sistors Q1 through Q4 and common transformer

justed with R8. A change in the 28-volt dc input

T1, generate a square wave voltage. This square

will cause a corresponding voltage change at the

wave voltage is transformer-coupki to two full-

bridge rectifier. A voltage increase causes Q7 to

wave bridge rectifiers. Diodes CR1 through CR4

conduct through R11 and decreases the conduction

form a full-wave bridge rectifier circuit. to provide

of Q5 nnd Q6. Thus, the emitter of Q5 goes low

18 volts dc. Diodes CR5 through CR8 form the

and effectively maintains the 28-volt input to os-

150-volt dc bridge rectifier. Ripple components on

cillator Q3/Q4. A decrease in the X1-volt input

the 150-volt dc line are reduced by a resistive-

will cause the opposite condition. Conduct ion of

capacitive filter circuit composed of resistors R.5

transistor Q7 will decrease, hereby increasing the

and R6 and capacitors C8 and C9. A regulator cir-

conduct ion through Q5 and Q6. The emitter out-

cuit is used to control the 150-volt dc output by

put of Q5 goes high and maintains the 28-volt

controlling the voltage to the square wave

input to the oscillator.

oscillators.

2-25