VHF Engineering PS-15C Instruction Manual

170

WATkR

ZT

PO

ROX

1971 . RINGHAMTON

NY

11902

607-721-9574

The PS-15C

is

a well filtered regulated 12-14 volt power supply capable of handlin

up to 15 amps.

It

is

designed for con~munications equipment where maximum

current

is

drawn less than 50 pcrcent of the time. For continuous operation,

it must be derated

approximately

20 percent.

*%@W$

PS-15C SPECIFICATIONS

@#

VOLTAGE OUTPUT:

adjustable between 12 and 14 volts.

LOAD REGULATION:

2

percent from no load to 15 anips.

CURRENT OUTPU'I

15 amps intermittent (50 percent duty cycle)
10 amps continuous.

CURRENT LIMITING: maximum short circuit current

1

amp nominal.

RIPPLE

:

50 MV at 10 amps.

AMBIENT TEMP:

OC

maximum.

LIMITED WARRANTY

Factory wired units are warranted for one year. The unit must be re-

turned to the factory postpaid with a note describing difficulty

and

date of purchase,

include a check to cover return postage.

Our liability under warranty

is

limited

to repair, adjustment or replacement of units proven to be defective. No further

warranty

is

expressed or implied. Units modified or obviously misused will

not be covered by the warranty.

The parts in kits built according to our instructions carry the original

manufacturers1 warranty. Defective parts must

be

returned for credit. Units
built from kits may be returned to the factory for repair and alignment for a
nominal charge, plus parts and shipping.

WARNING!

The input power connection

is

at

the ac line potential (115 or

230V

ac). Use caution when working
in this area.

PARTS LIST - PS3A

(Kit 7010190)

(Wired 7010191)

25000

MFD

40V (2010610)

.OO1

(2 010 3 70)
470MFD 16V (2 010 5 70)
.001 (2 010 3 70)
.01 (2010410)

1K 5% (2 020240)

2K Pot (202 0510)

1OK 570 (2020340)

5.6K 1/2W (2020300)
330 ohm

570 (2020175)

390 ohm

5% (PS15) (2020180)

3.3K 570 (2 02 02 70)
.1

ohm 5W (2020010)

Heat Sink Grease Capsule

(

3050200)"
P.C. Board (4040220-1)
Heat Sink

Small on

PS3A & PS15

(4020100)

Large on PS25 (4020150)
3 Keystone Pins (4060130)
Hardware

Instruction Sheet (5010203)

*C1

is

not supplied with PS3A kit.

When using

PS3A with external pass

transistors R7

is

changed to 100 ohm

1

W resistor (2020110)

.

CIRCUIT

l,3t'SCNIF"I

ION

The PS-3A regulator card can supply up to 6 amps of regulated 12-14 volts from

an unregulated source. It

is

designed for communicptions equipment where maximum

current

is

drawn less than 50 percent of the time. For continuous operation, it must be

derated to 3 amps with the heat sink supplied. The maximum current

is

limited by the
power dissipation (input voltage minus output times current) and the current capabilities
of the pass transistor, which

is

90 watts and 10 amps respectively at room temperature

for the

TIP3055. With a supply voltage of 20 volts, the PS3A

will

handle 6 amps by

adding additional heat sinking to keep the case temperature of the TIP3055 below

120°

centigrade. With the addition of external pas€ transistors, currents up to amps can be

k

regulated.

When using the

PS3A without external pass transistors, the maximum short

circuit current

is

6

amps. When used with external pass transistors,

R-7

is

changed

to 100 ohms. The maximum 'current of 6 amps

is

multiplied

by

the number of pass

transistors. The unregulated input must be at least two volts above the output under
load to keep the pass transistors out of saturation. Any ripple on the input voltage
must be added to the 2 volts difference.

When the pass transistor saturates regulation

is

lost.

THEORY

OF

OPER.4TJON

The IVE550

is

a precision voltage regulator chip that contains a zener voltage

reference, operational amplifier, current limiter, and pass transistor.

-4 portion of the

output voltage controlled by R-4

is

compared to a reference voltage, any difference or

error

is

amplified by the op-amp and changes the bias on the internal pass transistor to

eliminate the error.

The reference voltage for the

NE550

is

1.6 volts.

Therefore, the

t

autput voltage is the ratio of the voltage divider (consisting of R-1, 2, and 3) times

1.

6.

The current limiter transistor saturates when a voltage of .6

is

applied between pins 2 and

3, shuting down the output. Therefore, with a

.1

ohm resistor for R-5, the supply will

;hut $own

when.

a-~urrent

Qf

6

amps

is

reached.

The current limiting section of

IC1 operates when a vol

between pins 2 and 3 of IC1.

This voltage

is

the algebraic sum of

developed across R-5 and

R-7.

Reverse voltage

is

the result of

r

through R-5 and R-6 to ground.

Its value

is

dependent mainly

and

the value of

R-6.

Forward voltage (disabling voltage)

is

applied across

R-7

by the

load current through the paralled

E-B

junctions of the pass transistors and

.1

ohm

emitter resistors.

Its value

is

a function of load current. When the voltage across

R-7

s

.6

volts higher than the voltage across R-5, current limiting results.

3UPPLIES USING OVP

The over-voltage protection

(OliP)

is essentially a crowbar circuit which prevents

the output voltage from

rjsing above 14 volts.

if

t!le

supply voltage (pot on PS3A board)

is

set too high, the OVP will shut down the supply as soon as it

is

turned on.

To reset

the OVP:

turn the power off - wait about one minute for the filter capacitor to discharge

-

turn the regulator pot down - reapply power - adjust the regulator pot for the desired output

volt age.

Install

IC first.

The

T1P

3055 transis!or

is

installed with the metal side down.

The

6-32

screw holds the heat sink on top

of

the transistor.

Be sure to use some silicon

grease \)ctween

the

)]cat sink and

the

trar~slfor.

The mctal part of

the

transistor

is

interndly connected to

t11e

collector.

Therefore, the screw and heat sink have full

voltage on them.

Care should be taken to prevent them from grounding out.

Observe

pclarity on the electrolytic condensers.

The board

is

usually mounted by the filter con

dcnser.

If

it'is used without the filter condenser (when used with an existing filtered

unregulated supply) it may be

]mounted on stand offs by drilling mounting holes

in

the

corners of the board,