Hp A series Service manual

MODULAR

POWER

SUPPLIES

A,

C,

AND

E

SERIES

MODELS

62003A-62048A,

62003C-62048C,

AND

62003E-62048E

OPERATING

AND

SERVICE

MANUAL

FOR

SERIALS

1210A-00101

AND

ABOVE*

^For

Serials

Above

1210A-00101,

a

change

page

may

be

included.

Hewlett-Packard

HP

Part

No.

5950-5969

Printed;

May,

1972

SECTION

1

GENERAL

INFORMATION

1-1

DESCRIPTION

1-2

Hewlett-Packard

modular

power

supplies

are

completely

solid-state,

employing

high-reiiability

tran¬

sistors

and

integrated

circuits.

The

power

supplies

are

packaged

in

three

uniform

height

and

depth

cases

that

are

fractions

of

the

standard

19-inch

rack

width.

The

supplies

can

be

bench-operated

or

rack-mounted

indi¬

vidually

or

in

any

combination

to

full

rack

width

or

less.

The

modular

power

supplies

are

of

the

Constant

Voltage/Current

Limiting

type,

furnishing

fuli-rated

output

voltage

at

the

maximum

rated

output

current.

The

output

voltage

can

be

adjusted

between

±0.5

V

or

±5%

(whichever

is

greater)

of

nominal

while

providing

full-rated

output

current.

The

supply

and

load

are

fully

protected

from

current

overloads

by

a

self-restor¬

ing

current

cutback

circuit

that

causes

the

output

current

to

cutback

linearly

from

approximately

103%

to

approximately

10%

of

rated

output

as

the

load

varies

from

slightly

above

the

maximum

rated

value

to

a

complete

short

circuit.

The

current

limit

(cutback)

activation

point

is

adjustable

anywhere

between

the

103%

and

10%

limits.

1-3

Either

the

positive

or

negative

output

terminal

may

be

grounded

at

the

rear

terminals.

1-4

SCOPE

1-5

This

manual

provides

installation

procedures,

operating

instructions,

principles,of

operation,

main¬

tenance

data,

and

replaceable

parts

information

for

the

thirty-three

Hewlett-Packard

modular

power

supplies

listed

in

the

following

chart.

Note

that

the

last

two

digits

in

the

model

number

indicate

the

nominal

out¬

put

voltage

of

the

supply.

The

-A

suffix

supplies

are

1/8-rack

width

units

while

the

-C

and

-E

models

are

1/4-rack

width

units.

1-6

SCHEMATICS

1-7

The

modular

power

supplies

covered

in

this

manual

are

of

similar

design

differing

mainly

in

com¬

ponent

values

rather

than

in

circuit

operation.

Hence,

in

general,

the

information

presented

in

the

manual

applies

to

all

of

the

power

supply

models

with

any

significant

differences

among

the

supplies

described

as

applicable.

Thus,

the

schematic

diagrams

at

the

rear

of

the

manual

depict

groups

of

similar

supplies

with

five

DC

OUTPUT

MODEL

NOMINAL

VOLTAGE

(Minimum

Adj.

Span)

CURRENT

AT50“C

3V

(±0.5V}

2A

62003A

4.25A

62003C

8.5A

62003E

4V(±0.5V)

2A

62004A

4A

62004C

8A

62004E

5V

(±0.5V)

2A

62005A

4A

62005C

8A

62005E

6V

(±0.5V)

1.75A

62006A

3.75A

62006C

7.5A

62006E

10V

(±0.5V)

1.5A

6201OA

3.25A

62010C

6.5A

62010E

12V

(±0.60V)

1.5A

62012A

3.0A

62012C

6.0A

62012E

15V

(±0.75V)

1.25A

62015A

2.SA

62015C

5.0A

62015E

18V{±0.90V)

1.0A

62018A

2.25A

62018C

4.5A

62018E

24V

(±

1.20V)

.75A

62024A

1.75A

62024C

3.75A

62024E

28V

(±

1.40V)

.7A

62028A

1.5A

62028C

3.25A

62028E

48V(±2.40V)

.45A

.62048A

1.0A

62048C

2.0A

62048E

1-1

schematics

provided

to

illustrate

all

33

models.

Each

schematic,

of

course,

identifies

the

supplies

for

which

it

applies

and

includes

notes

and

tables

to

identify

the

difference

{mainly

in

component

values)

among

the

supplies

illustrated

in

the

common

schematic.

1-8

SPECIFICATIONS

1-9

Detailed

specifications

for

the

power

supplies

are

given

in

Table

1-1.

Table

T1.

Specifications

INPUT:

115Vac

±10%,

single

phase,

48-63

Hz.

See

Options

101,

102,

and

103.

OUTPUT:

See

Paragraph

1-5.

LOAD

REGULATION;

Less

than

0.01

%

or

1

mV

whichever

is

greater

for

a

full

load

to

no

load

change

in

output

current.

LINE

REGULATION:

Less

than

0.01

%

or

1

mV

whichever

is

greater

for

a

10%

change

in

the

specified

input

voltage.

RIPPLE

AND

NOISE:

Less

than

1

mV

rms

and

2

mV

p-p

(up

to

20

MHz).

TEMPERATURE

RANGES;

Operating:

0

to

50“C

ambient.

Output

current

de¬

rated

linearly

for

temperatures

greater

than

50°

with

50%

of

maximum

output

current

at

71°C

ambient.

Storage:

~55°C

to

+85“C

Cooling:

Convection

cooled.

TEMPERATURE

COEFFICIENT:

Less

than

0.01%

output

voltage

change

per

degree

Centigrade

over

the

operating

range

from

0

to

50

C

after

30

minutes

warmup.

THERMAL

PROTECTION:

Heat

sink

mounted

thermostat

opens

ac

line

if

supply

overheats

due

to

high

ambient

temperature.

Thermostat

automatically

closes

(reset)

when

temper¬

ature

cools

to

safe

operating

level.

STABILITY:

Less

than

0.1%

total

drift

for

8

hours

after

an

initial

warm-up

time

of

30

minutes

at

constant

ambient,

con¬

stant

line

voltage,

and

constant

load.

TRANSIENT

RECOVERY

TIME:

Less

than

50

jusec

for

output

recovery

to

within

15

mV

of

nominal

output

voltage

following

a

load

change

from

full

to

half

load

(or

vice

versa)._

OVERLOAD

PROTECTION:

A

current

limit

circuit

cuts

back

current

linearly

to

approximately

10%

of

rated

output

current

when

supply

is

short-circuited.

Automatically

resets

when

overload

removed.

Current

limit

activation

point

adjustable

(screwdriver

control)

but

preset

at

factory

to

activate

at

104

±1%

of

maximum

rated

output

current

at

nominal

output

voltage.

OUTPUT

CONTROL:

Screwdriver

adjustment

accessible

through

hole

in

front

panel.

Minimum

adjustment

range

is

±0.5

V

or

±5%,

whichever

is

greater.

ERROR

SENSING:

Error

sensing

normally

accomplished

locally

at

rear

terminals.

Provision

included

at

rear

terminal

strip

for

remote

sensing

with

correction

for

load

lead

voltage

drops

of

up

to

0.5

V

total.

Load

protected

if

sensing

terminals

inadvertently

opened.

MOUNTING:

Three

mounting

surfaces

provided

for

mounting

in

the

upright

position.

For

mounting

orientations

other

than

upright,

adequate

cooling

is

required.

See

Section

II.

DIMENSIONS;

A—

suffix

models:

1.91"

W

x

5.03"

H

x

12.25

D

'

(48

mm

W

x

128mm

H

x

311mm

D)

C-

Si

E

™

suffix

models;

3.94"

W

x

5.03"

H

12.25"

D

(100

mm

W

X

128mm

H

x

311mm

D)

WEIGHT

(net/shipping):

A—

suffix

Models:

6

lbs

(2,

7

kg)/8

lbs

(3,

6

kg)

C-

suffix

Models:

10

lbs

(4,

5

kg)/12

lbs

(5,

4

kg)

E-

suffix

Models:

ii

lbs

(5,9

kg)/16

lbs

(7,

3

kg)

1-10

OPTIONS

103

T11

Options

are

factory

modifications

of

a

standard

instrument

that

are

requested

by

the

customer.

The

following

options

are

available

for

the

instruments

covered

by

this

manual.

Where

necessary,

detailed

cover¬

age

of

the

options

are

included

in

the

manual.

OPTION

NO.

DESCRIPTION

011

Overvoltage

Protection

"Crow¬

bar":

A

completely

separate

circuit

for

protecting

delicate

loads

against

power

supply

failure

or

operator

error.

The

crowbar

circuit

monitors

the

output

voltage

and

within

10

Msec

imposes

a

virtual

short-circuit

(conducting

SCR

or

triac)

across

the

power

supply

output

if

the

preset

overvoltage

margin

is

exceeded.

The

crowbar

circuit

is

contained

on

a

printed

wiring

board

that

is

mounted

inside

the

power

supply.

The

activa¬

tion

(trip)

voltage

of

the

crowbar

is

adjustable

(screwdriver

adjustment)

over

the

following

minimum

range:

from

-i-0.5

Vdc

above

minimum

rated

output

voltage

to

+2

Vdc

above

maxi¬

mum

rated

output

voltage.

101

220

Vac,

single

phase

input:

Supply

is

normally

shipped

with

a

120

Vac

(nominal)

transformer.

Option

101

replaces

this

transformer

with

a

220

Vac

(nominal)

transformer

and

allows

operation

from

a

190-233

Vac,

48-63

Hz

single

phase

input.

102

240

Vac,

single

phase

input:

Supply

is

normally

shipped

with

a

120

Vac

(nominal)

transformer.

Option

102

replaces

this

transformer

with

a

240

Vac

(nominal)

transformer

and

allows

operation

from

a

208-254

Vac,

48-63

Hz,

single

phase

input,

120

Vac/240

Vac,

single

phase

in¬

put:

Supply

is

normally

shipped

with

a

120

Vac

(nominal)

transformer.

Option

103

replaces

this

transformer

with

a

120

Vac/240

Vac

(nominal)

multi-tap

transformer

and

allows

field-

changeable

operation

from

104-127

Vac

or

208-254

Vac,

48-63

Hz

single

phase

input.

104

System

Control:

This

option

allows

the

user

to

control

the

supply's

over¬

voltage

protection

"crowbar"

circuit

as

well

as

output

voltage.

The

104

option

includes

the

same

internal,

ad¬

justable

overvoltage

protection

crow¬

bar

as

provided

with

the

011

option.

In

addition,

the

104

option

crowbar

includes

external

(from

a

rear

term¬

inal

strip)

pulse

control

capability

that

allows

the

crowbar

to

be

either

externally

triggered

or

which

provides

an

output

pulse

to

indicate

that

the

crowbar

has

triggered.

The

crowbar

pulse

specifications

are:

Input

Trigger

Pulse:

Voltage:

8

—

15

V

Width

(between

90%

point

at

leading

edge

and

10%

point

at

falling

edge);

5

jusec

—

2

msec

Output

Pulse:

Voltage;

2

-

12

V

Width

(between

90%

point

at

leading

edge

and

10%

point

at

falling

edge):

2

—

20Msec

Load

Impedance;

1

Kii

(min.)

In

addition

to

the

crowbar

trigger

external

access,

the

104

option

also

includes

access

(from

a

rear

terminal

strip)

to

the

summing

point

of

the

supply

to

enable

the

dc

output

volt¬

age

to

be

remotely

programmed

to

zero

(±15

mVdc

max.)

with

a

contact

closure.

1-3

1-13

The

accessories

listed

below

may

be

ordered

with

the

power

supply

or

separately

from

your

local

Hewlett-

Packard

field

sales

office

(refer

to

list

at

rear

of

manual

for

addresses).

HP

Part

No.

Description

62410A

Rack

Mounting

Tray

for

mounting

any

combination

of

supplies.

19”

wide,

5'1/4”

high,

and

17”

deep.

(Refer

to

Section

II

for

details.)

62411A

Rack

Tray

Blank

Front

Panel,

10-1/2"

wide,

5-3/16"

high,

1/8"

thick.

62412A

Rack

Tray

Blank

Rear

Panel,

mounts

on

rear

of

rack

mounting

tray

and

allows

installation

of

custom

input/

output

connectors

or

other

hardware.

62415A

Rack

Tray

AC

Distribution

Panel

mounts

on

rear

of

rack

mounting

tray

and

includes

ac

input

terminal

strip

and

line

card.

62414A

Rack

Tray

Slides

provide

easy

access

to

rack

mounting

tray

and

its

supplies.

62413A

Rack

Mounting

Tray

Cooling

Unit

provides

forced

air

cooling

of

rack¬

mounted

supplies.

1-15

Hewlett-Packard

power

supplies

are

identified

by

a

two-part

serial

number.

The

first

part

is

the

serial

number

prefix,

a

number-letter

combination

that

de¬

notes

the

date

of

a

significant

design

change

and

the

country

of

manufacture.

The

first

two

digits

indicate

the

year

(10=

1970,

11

=1971,

etc.),

the

second

two

digits

indicate

the

week,

and

the

letter

"A”

designates

the

U.S.A.

as

the

country

of

manufacture.

The

second

part

is

the

power

supply

serial

number;

a

different

sequential

number

Is

assigned

to

each

power

supply,

starting

with

00101.

1-16

If

the

serial

number

on

your

instrument

does

not

agree

with

those

on

the

title

page

of

the

manual.

Change

Sheets

supplied

with

the

manual

or

Manual

Backdating

Changes

define

the

differences

between

your

instrument

and

the

instrument

described

by

this

manual.

M7

ORDERING

ADDITIONAL

MANUALS

1-18

One

manual

is

shipped

with

each

power

supply.

Additional

manuals

may

be

purchased

from

your

local

Hewlett-Packard

field

office

(see

list

at

rear

of

this

manual

for

addresses).

Specify

the

model

number,

serial

number

prefix,

and

HP

Part

number

provided

on

the

title

page.

INITIAL

INSPECTION

NOTE

2-2

Before

shipment,

this

instrument

was

inspected

and

found

to

be

free

of

mechanical

and

electrical

de¬

fects.

As

soon

as

the

instrument

Is

unpacked,

inspect

for

any

damage

that

may

have

occurred

in

transit.

Save

all

packing

materials

until

the

inspection

is

completed.

If

damage

is

found,

a

claim

should

be

filed

with

the

carrier

immediately.

Also,

a

Hewlett-Packard

Sales

and

Service

office

should

be

notified.

2-3

i\flechanica!

Check

2-4

This

check

should

confirm

that

there

are

no

broken

connectors

and

that

the

panel

surfaces

are

free

of

dents

and

scratches.

2-5

Electrical

Check

2-6

The

instrument

should

be

checked

against

its

electrical

specifications.

Section

V

includes

an

"in-cab-

inet”

performance

check

to

verify

proper

instrument

operation,

2-7.

INSTALLATION

DATA

2-8

The

instrument

is

shipped

ready

for

bench

oper¬

ation.

It

is

necessary

only

to

connect

the

instrument

to

a

source

of

power

and

it

is

ready

for

operation.

2-9

Location

2-10

This

instrument

is

air

cooled.

Sufficient

space

should

be

allotted

so

that

a

free

flow

of

cooling

air

can

reach

the

instrument

when

it

is

in

operation.

At

least

1/2-inch

clearance

at

the

bottom

of

the

unit

is

recom¬

mended

to

permit

proper

air

flow.

The

supply

should

be

used

in

an

area

where

the

ambient

temperature

does

not

exceed

50°C.

If

operated

at

an

ambient

greater

than

50°C,

the

supply's

output

current

must

be

linearly

de¬

rated

down

to

50%

at

71°C.

If

the

power

supply

must

be

operated

in

a

restricted

air

flow

environment,

the

supply's

power

consumption

(and

heat

dissipation

requirements)

can

be

minimized

by

oper¬

ating

at

low

tine

input

voltage.

Consult

your

nearest

HP

sales

engineer

for

more

infor¬

mation

on

the

cooling

requirements

for

your

specific

operation

2-11

Mounting

Orientation

2-12

Figure

2-1

shows

outline

and

dimension

infor¬

mation

for

each

modular

power

supply

size.

As

shown,

holes

are

provided

on

three

surfaces

of

the

supplies

any

of

which

can

be

used

to

install

the

supply

in

the

up¬

right

position.

If

the

top

mounting

holes

are

used;

how¬

ever.

be

sure

that

a

rigid

top

support

is

employed

to

support

the

weight

of

the

unit{s).

Note

that

if

any

other

orientation

other

than

upright

is

required,

adequate

air

flow

must

be

provided;

see

your

nearest

HP

sales

engi¬

neer

for

additional

information.

2-13

Rack

Mounting

2-14

The

modular

power

supplies

can

be

readily

mounted

in

any

combination

in

a

standard

19-inch

rack

using

the

Hewlett-Packard

Rack

Mounting

Tray,

Model

62410A.

The

supplies

are

mounted

upright

and

attached

to

the

tray

using

the

two

(A—

suffix

models)

or

four

{C—

and

E—

suffix

models)

10-32

threaded

mounting

holes

located

in

the

bottom

of

the

supply

case.

The

maximum

number

of

supplies

that

can

be

mounted

in

the

tray

depends

on

the

types

of

supplies

used.

For

example,

if

all

1/8-width

{A-

suffix)

supplies

are

employed,

eight

modular

power

supplies

can

be

mounted

in

the

tray.

Of

course,

the

tray

does

not

have

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SUFFIX

MODELS

(1/4-WIDTH

PACKAGE)

Figure

2-1.

Outline

Diagrams,

Modular

Power

Supplies

2-2

2-15

INPUT

POWER

REQUIREMENTS

2-16

The

modular

power

supplies

may

be

operated

from

a

nominal

120

Vac,

220

Vac,

or

240

Vac,

48-63

Hz,

power

source.

The

standard

supply

(no

options)

is

shipped

from

the

factory

wired

for

120

Vac

(nominal)

operation

and

requires

the

following

maxi¬

mum

input

current

and

power

at

high

line

(127

Vac)

voltage

input:

AC

INPUT

at

127

Vac

MODEL

CURRENT

(Max.)

POWER

(Max.)

62003A

.30A

31W

62003C

.77A

74W

62003E

1.38A

143W

62004A

.33A

34W

62004C

.78A

76W

62004E

1.42A

149W

62005A

.37A

37W

62005C

.80A

79W

62005E

1.53A

160W

62006A

.36A

37W

62006C

.80A

79W

62006E

1.56A

161W

6201OA

.39A

39W

62010C

.98A

97W

62010E

1.87A

192W

52012A

.47A

47W

62012C

1.00A

100W

62012E

1.89A

191W

62015A

.45A

46W

62015C

.99A

97W

62015E

1.82A

181W

62018A

.42A

42W

62018C

.97A

95W

62018E

1.93A

196W

62024A

.39A

39W

62024C

.93A

88W

62024E

1.95A

198W

62028A

.44A

44W

62028C

.91

A

86W

62028E

1.87A

190W

62048A

.47

A

47W

62048C

.97A

95W

62048E

2.00A

193W

2-17

220/240

VOLT

OPERATION

2-18

As

applicable,

Options

101,102,

and

103

(in¬

stalled

at

the

factory)

permit

the

supply

to

be

operated

from

a

120,

220,

or

240

Vac

(nominal)

input

line.

Option

101

provides

for

220

Vac

operation

while

Option

102

allows

240

Vac

operation.

Option

103,

however,

provides

for

either

120

Vac

or

240

Vac

oper¬

ation

at

the

selection

of

the

user

as

described

below.

2-19

Option

103

Power

Transformer

Connections,

A—

suffix

Models.

For

the

A-

suffix

models,

the

pri¬

mary

connections

of

the

supply

are

changed

at

the

in¬

board

side

of

the

rear

power

input

terminals.

For

120

Vac

operation

(as

shipped),

two

leads

are

soldered

from

each

of

the

ac

input

terminals

as

shown

in

Figure

2-2B.

To

connect

the

supply

for

240

Vac

oper¬

ation,

unsolder

the

wht/bik/yel

and

wht/blk/grn

leads

and

twist

them

together

with

a

wire

terminal

as

shown

in

Figure

2-2A.

Figure

2-2.

Primary

Connections

For

120/240

Vac

Operation

(Option

103)

—

A

Suffix

Models

Only

2-20

Option

103

Power

Transformer

Connections,

-C

and

E-

Suffix

Models.

For

the

C-

and

E-

suffix

models,

the

appropriate

power

transformer

120/240

V

terminals

must

be

connected

as

shown

in

Figure

2-3.

Notice

that

the

transformer

connections

are

changed

at

the

transformer

terminals

shown

in

the

illustration.

2-3

2-21

REPACKAGING

FOR

SHIPMENT

A

INPUT

POWER

TRANSFORMER

(T!)

PRIMARY

CONNECTIONS

FOR

240V

OPERATION

B

INPUT

POWER

TRANSFORMER

(Tl>

primary

CONNECTIONS

FOR

120V

OPERATION

Figure

2-3.

Primary

Connections

For

120/240

Vac

Operation

(option

103)

-C

and

-E

Suffix

Models

Only

2-22

To

insure

safe

shipment

of

the

instrument,

it

is

recommended

that

the

package

designed

for

the

instru¬

ment

be

used.

The

original

packaging

material

is

re¬

usable.

If

it

is

not

available,

contact

your

local

Hewlett-

Packard

field

office

to

obtain

the

materials.

This

office

will

also

furnish

the

address

of

the

nearest

service

office

to

which

the

instrument

can

be

shipped.

Be

sure

to

attach

a

tag

to

the

instrument

which

specifies

the

owner,

model

number,

full

serial

number,

and

service

required,

or

a

brief

description

of

the

trouble.

2-4

3-1

TURN-ON

CHECKOUT

PROCEDURE

3-2

The

following

checkout

procedure

describes

the

use

of

the

voltage

control

and

ensures

that

the

supply

is

operational.

a.

Before

connecting

input

power

to

unit,

connect

external

voltmeter

across

+S

and

—S

terminals

at

rear

terminal

board.

b.

Connect

unit

to

input

power

source

using

AC,

ACC.

and

ground

terminals

at

rear.

(Use

proper

wire

size

in

accordance

with

the

input

AC

current

rating.)

c.

Observe

output

voltage

of

supply

on

external

meter.

Output

is

factory

set

to

nominal

voltage.

If

de¬

sired.

VOLTAGE

ADJUST

(screwdriver

control,

ac¬

cessible

through

cutout

on

front

panel)

potentiometer

can

be

used

to

set

output

to

any

voltage

within

adjust¬

ment

span

(±0.5

V

or

±5%

as

applicable).

NOTE

The

current

limit

may

require

readjust¬

ment

if

the

output

voltage

is

set

away

from

nominai.

Refer

to

Paragraph

3-8.

d.

To

verify

operation

of

current

limit

circuit,

remove

voltmeter

and

disconnect

input

power.

Connect

short

across

output

terminals

of

supply

and

reconnect

input

power.

Using

clip-on

milliammeter

(HP

Model

428B,

or

equivalent)

observe

that

short

circuit

output

current

is

approxi

mately

3%

to

15%

of

rated

output

current.

e.

Remove

short

and

milliammeter.

Before

con¬

necting

actual

load

to

supply,

read

the

following

para¬

graphs.

3-3

OPERATION

3-4

The

supply

can

be

operated

in

one

of

two

oper¬

ating

modes;

normal

or

remote

sensing.

Auto-Series,

Auto-Parallel,

Auto-Tracking

and

remote

programming

operation

are

not

feasible

with

this

supply.

The

follow¬

ing

paragraphs

describe

both

of

those

modes

plus

supplementary

operating

information.

More

theoreti¬

cal

descriptions

regarding

the

operational

features

of

power

supplies

in

general

are

given

in

application

note

90A,

DC

Power

Supply

Handbook

(available

at

no

charge

from

your

local

HP

sales

office).

3-5

Normal

Operating

Mode

3-6

The

power

supply

is

shipped

with

the

rear

term¬

inal

straps

connected

for

Constant

Voltage/Current

Limiting,

local

sensing,

operation.

This

strapping

pattern

is

illustrated

in

Figure

3-1.

Before

connecting

a

load

to

the

supply,

check

the

rear

terminals

to

ensure

that

the

connections

are

correct

and

that

the

connect¬

ing

straps

are

tightened

securely.

3-7

Current

Limit

3-8

Figure

3-2

shows

typical

current

limiting

charac¬

teristics

for

all

HP

modular

supplies.

As

indicated

on

the

drawing,

the

current

limit

point

varies

in

accord¬

ance

with

the

output

voltage.

As

received

from

the

factory,

the

initial

current

limit

point

is

set

to

104

±1

%

of

the

current

rating

with

the

output

voltage

at

its

nominal

value.

This

same

current

limit

setting

is

recom¬

mended

for

ail

output

voltages

within

the

adjustment

span

because:

(1)

the

current

limit

crossover

point

must

be

at

least

3%

higher

than

the

maximum

expected

operating

current

to

prevent

performance

degradation;

and

(2)

a

current

limit

setting

of

higher

than

105%

of

rating

creates

the

possibility

of

excessive

internal

heat¬

ing

as

specified

in

the

caution

note

of

Figure

3-2.

Hence,

the

current

limit

potentiometer

(accessible

through

a

cutout

in

the

side

panel)

may

have

to

be

readjusted

to

satisfy

the

above

two

requirements

if

the

user

intends

to

operate

at

an

output

voltage

which

is

above

or

below

nominal.

For

example,

if

the

user

has

a

supply

of

10

Volts

or

above

and

requires

an

output

voltage

of

+5%

above

nominal,

the

initial

current

limit

point

would

be

factory

set

to

approximately

109%

of

rating.

This

violates

the

105%

current

limit

constraint

mentioned

previously

and,

thus,

the

current

limit

potentiometer

would

have

to

be

adjusted

(described

in

Section

V)

so

that

the

current

limit

point

is

moved

to

104

±1%at

the

upper

voltage

limit

rather

than

at

nominal

voltage.

A.

SUPPLIES

BELOW

lOV

NOMINAL

OUTPUT

*

3V

89%

119%

4V

93%

115%

5V

95%

113%

6V

97%

111

%

B.

SUPPLIES

10V

AND

ABOVE

CAUTIOM

OPERATION

AT

OUTPUT

CURRENTS

ABOVE

I0S%

OF

RATING

CAN

CAUSE

EXCESSIVE

INTERNAL

HEATING

AND

POSSIBLE

DAMAGE

TO

THE

SUPPLY,

3-9

Connecting

Load

3-10

Each

load

should

be

connected

to

the

proper

supply

output

terminals

using

separate

pairs

of

con¬

necting

wires.

This

will

minimize

mutual

coupling

effects

between

loads

and

will

retain

full

advantage

of

the

low

output

impedance

of

the

power

supply.

Each

pair

of

connecting

wires

should

be

as

short

as

possible

and

twisted

or

shielded

to

reduce

noise

pickup.

(If

a

shield

is

used,

connect

one

end

to

power

supply

ground

terminal

and

leave

the

other

end

unconnected.)

3-11

if

load

considerations

require

that

the

output

power

distribution

terminals

be

remotely

located

from

the

power

supply,

then

the

power

supply

output

term¬

inals

should

be

connected

to

the

remote

distribution

terminals

via

a

pair

of

twisted

or

shielded

wires

and

each

load

separately

connected

to

the

remote

distribu¬

tion

terminals.

For

this

case,

remote

sensing

should

be

used

(Paragraph

3-13).

3-12

Positive

or

negative

voltages

can

be

obtained

from

this

supply

by

grounding

either

one

of

the

out¬

put

terminals

or

one

end

of

the

load.

3-13

Remote

Sensing

(See

Figure

3-3)

3-14

Remote

sensing

is

used

to

maintain

good

regu¬

lation

at

the

load

by

reducing

the

degradation

in

regu¬

lation

that

would

occur

due

to

the

voltage

drop

in

the

leads

between

the

power

supply

and

the

load.

Remote

sensing

is

accomplished

by

utilizing

the

strapping

pat¬

tern

shown

in

Figure

3-3.

The

power

supply

should

be

turned

off

before

changing

strapping

patterns.

The

leads

from

the

sensing

terminals

to

the

load

will

carry

much

less

current

than

the

load

leads

and

it

is

not

re¬

quired

that

these

leads

be

as

heavy

as

the

load

leads.

However,

they

must

be

twisted

or

shielded

to

mini¬

mize

noise

pick-up.

Figure

3-2.

Typical

Current

Limiting

Characteristics

Figure

3-3,

Remote

Sensing

3-2

3-15

For

reasonable

load

lead

lengths,

remote

sensing

greatly

improves

the

performance

of

the

supply.

How¬

ever,

if

the

load

is

located

a

considerable

distance

from

the

supply,

added

precautions

must

be

observed

to

obtain

satisfactory

operation.

Notice

that

the

voltage

drop

in

the

load

leads

subtracts

directly

from

the

avail¬

able

output

voltage

and

also

reduces

the

amplitude

of

the

feedback

error

signals

that

are

developed

within

the

unit.

Because

of

these

factors

it

is

recommended

that

the

total

drop

in

both

load

leads

not

exceed

0.5

V.

If

a

larger

drop

must

be

tolerated,

please

consult

your

local

HP

sales

engineer.

NOTE

Due

to

the

voltage

drop

in

the

load

leads,

it

may

be

necessary

to

readjust

the

current

limit.

Refer

to

Paragraph

3-8.

3-16.

It

should

be

noted

that

a

problem

can

occur

in

obtaining

maximum

rated

output

voltage

(nominal

+0.5

V)

from

a

lower

voltage

supply

(below

10

V)

even

if

the

total

voltage

drop

in

both

load

leads

is

maintained

at

0.5

Volt.

This

problem

is

most

likely

to

occur

when

the

input

ac

is

at

low

line.

To

counter¬

act

this

effect,

the

user

can

maintain

the

ac

input

at

a

higher

line

voltage

or

reduce

the

voltage

drop

in

the

load

leads

by

using

larger

diameter

wires.

3-17

SPECIAL

OPERATING

PRECAUTIONS

3-18

Temperature

3-19

The

normal

operating

temperature

for

this

supply

is

from

0

to

50°C,

ambient.

Beyond

50°C,

the

output

current

is

linearly

derated

to

50%

at

71

C.

Additional

information

on

temperature

is

given

in

Section

II.

NOTE

During

normal

operation

of

the

supply,

the

case

of

the

unit

may

become

hot

to

the

touch.

This

is

a

normal

occurrence

and

no

cause

for

alarm.

3“20

Mounting

Orientation

3-21

The

supply

should

be

mounted

and

operated

in

the

upright

position

as

instructed

in

Section

II.

If

the

supply

must

be

operated

in

an

orientation

other

than

upright,

an

adequate

flow

of

cooling

air

must

be

main¬

tained.

Contact

your

nearest

HP

sales

engineer

for

details.

3-3

SECTION

IV

PRINCIPLES

OF

OPERATION

4-1

OVERALL

DESCRIPTION

4-2

Figure

4-1

is

a

simpiified

schematic

of

the

power

supply

indicating

ail

of

its

major

circuits.

Except

for

minor

variations

{discussed

later

in

Section

IV)

the

Hewlett-Packard

modular

supplies

covered

by

this

manual

are

as

shown

in

Figure

4-1.

Notice

that

each

stage

of

the

supply

has

been

designated

according

to

function.

These

functional

designations

also

appear

on

the

applicable

schematic

at

the

rear

of

the

manual

so

that

both

diagrams

can

be

correlated.

4-3

The

ac

input

voltage

is

reduced

to

the

proper

level

by

the

power

transformer

and

fed

to

the

rectifier-

filter

where

it

is

converted

to

raw

(unregulated)

dc.

The

raw

dc

voltage

is

adjusted

by

the

series

regulator

so

that

a

regulated,

constant

voltage

is

available

across

the

out¬

put

terminals

of

the

supply.

4-4

The

series

regulator,

part

of

a

feedback

loop,

alters

its

conduction

in

accordance

with

the

feedback

control

signals

obtained

from

the

driver.

The

driver,

in

turn,

is

controlled

by

feedback

signals

originated

in

4-1

the

voltage

comparison

amplifier,

during

constant

volt¬

age

operation,

or

the

current

limiting

amplifier

during

current

limit

operation.

4-5

The

reference

supply

provides

regulated

bias

voltages

which

are

used

by

the

internal

circuitry

throughout

the

main

power

supply.

4^6

DETAILED

DESCRIPTION

4-7

The

following

paragraphs

describe

in

detailed

terms,

the

operation

of

each

of

the

supply's

major

circuits.

Throughout

this

discussion,

refer

to

both

the

simplified

schematic

of

Figure

4-1

and

the

appropriate

schematic

diagram

at

the

rear

of

the

manual.

4-8

Feedback

Loop

4-9

The

voltage

comparison

amplifier,

together

with

the

driver

and

series

regulator,

comprises

the

constant

voltage

feedback

loop.

This

feedback

loop

maintains

a

constant

output

voltage

during

normal

(constant

voltage)

operation.

To

accomplish

this,

the

voltage

comparison

amplifier

continuously

monitors

the

out¬

put

voltage

of

the

supply.

It

detects

instantaneous

changes

in

the

output

and

applies

an

amplified

error

signal

to

the

series

regulator

(via

the

driver)

which

is

of

the

correct

phase

and

amplitude

to

counteract

the

change.

4-10

The

feedback

loop

also

prevents

the

output

current

from

exceeding

a

preset

current

limit

value.

Current

limiting

operation

is

initiated

by

the

current

limit

comparison

amplifier

which

conducts

if

the

out¬

put

current

that

flows

through

the

current

sampling

resistance

exceeds

a

value

established

by

the

current

limit-adjust

potentiometer.

When

conducting,

this

am¬

plifier

sends

a

turn-down

signal

to

the

series

regulator,

via

the

driver.

4-11

An

output

capacitor,

Cq

,

connected

across

the

output

of

the

supply,

helps

to

stabilize

the

feedback

loop

regardless

of

the

type

of

load

that

is

imposed.

4-12

Constant

Voltage

Comparison

Amplifier

4-13

This

circuit

consists

of

the

VOLTAGE

ADJUST

potentiometer

R7

and

a

differential

amplifier

stage

(U2

and

associated

components).

An

integrated

circuit

is

used

for

the

differential

amplifier

for

increased

reliability

and

to

minimize

differential

voltages

due

to

mis-matched

transistors

and

thermal

differentials.

4-14

The

voltage

comparison

amplifier

continuously

compares

the

output

voltage

of

the

supply

with

the

voltage

drop

between

the

—S

terminal

and

the

circuit

s

summing

point

(junction

at

voltage

divider

R5,

R7,

and

R8).

if

these

two

voltages

are

momentarily

unequal,

an

error

voltage

is

generated

whose

amplitude

is

propor¬

tional

to

the

difference.

The

error

signal

ultimately

alters

the

conduction

of

the

series

regulator

which,

in

turn,

alters

the

output

current

so

that

the

output

volt¬

age

becomes

equal

to

the

voltage

at

the

summing

point.

Hence,

through

feedback

action,

the

difference

between

the

two

inputs

to

U2

is

held

at

nearly

zero

volts.

4-15

The

inverting

input

of

the

comparison

amplifier

(pin

2

of

U2)

is

connected,

through

jumper

W1

to

the

constant

voltage

summing

point.

(As

indicated

on

NOTE

7

of

each

schematic,

W1

is

connected

either

to

the

junction

of

R5,

R7

for

supplies

below

10

V

or

to

the

junction

of

R7,

R8

for

supplies

10

V

and

above.)

The

non-inverting

input

to

the

comparison

amplifier

(pin

3

of

U2)

is

connected

directly

to

the

output

volt¬

age

sensing

terminal

(+S)

of

the

supply.

Instantaneous

changes

in

the

output

voltage,

or

changes

at

the

sum¬

ming

point

due

to

rotation

of

the

voltage

pot,

produce

a

difference

voltage

between

the

two

inputs

of

the

comparison

amplifier.

This

difference

voltage

is

am¬

plified

and

appears

at

the

output

of

the

amplifier,

at

6.

4-16

Capacitor

C12

and

resistor

RIO

couple

rapid

out

put

voltage

variations

to

the

input

of

U2

while

slower

(dc)

changes

are

coupled

to

U2

via

resistor

R8.

Diodes

CR11

and

CR12

prevent

excessive

voltage

excursions

from

over-driving

the

comparison

amplifier;

RC

net¬

work

R12,C13

provide

degenerative

feedback

to

help

stabilize

the

feedback

loop.

4-17

Driver

4-18

The

driver

amplifies

the

error

signal

from

the

constant

voltage

or

current

limit

comparison

amplifiers

to

a

level

sufficient

to

drive

the

series

regulating

tran-

sistor(s).

Inverting

stage

Q2

receives

its

input

signal

from

the

OR-gate

diode

(CRI3

or

CR14)

that

is

con¬

ducting

at

the

time.

During

normal

(constant

voltage)

operation,

CR13

is

forward

biased

and

CR14

is

reverse

biased.

The

reverse

is

true

during

current

limiting

operation.

4-2

4-19

Stage

Q2

provides

mainly

voltage

amplification

of

the

feedback

signal

while

emitter

follower

Q3

pro¬

vides

most

of

the

current

gain.

Some

models;

e.g.

62048A,

contain

only

one

driver

stage

(Q2)

instead

of

two.

4-20

Feedback

capacitor

CIS

provides

degenerative

feedback

to

Q3

to

prevent

oscillation

and

Cl

9

helps

shape

the

high

frequency

rolloff

of

the

feedback

loop

response

curve.

R28

provides

a

leakage

current

path

for

transistor

Q3.

4-21

Series

Regulator

4-22

The

series

regulator,

or

series

control

element,

acts

as

a

variable

resistance

connected

in

series

with

the

load.

Its

conduction

is

controlled

by

the

feedback

signals

from

the

driver

so

that

the

output

voltage

is

maintained

constant

or

the

current

limit

is

not

ex¬

ceeded.

A

diode

(CRs

on

Figure

4-1)

connected

across

the

regulator,

protects

the

series

eiement(s)

from

possible

damage

by

a

reverse

current

flow.

4-23

Many

modular

power

supplies

employ

one

series

transistor

as

indicated

on

Figure

4-1.

However,

higher

power

units

(such

as

Models

62003E

thru

62048E)

use

two

regulating

transistors,

connected

in

parallel

to

minimize

power

dissipation.

Approximately

half

of

the

output

current

flows

through

each

transistor.

4-24

Current

Limit

Comparison

Amplifier

4-25

This

circuit

consists

of

current

limit

adjust

po¬

tentiometer

R18

and

a

differential

amplifier

stage

(U3and

associated

components).

Stage

U3

is

similar

in

appearance

and

operation

to

the

constant

voltage

comparison

amplifer,

U2.

4-26

The

current

limit

comparison

amplifier

effect¬

ively

monitors

the

output

current

of

the

supply

by

monitoring

the

IR

drop

across

current

sampling

resis¬

tor

R15.

The

voltage

drop

across

R15

is

compared

with

a

reference

voltage

established

by

the

setting

of

current

limit

potentiometer

R18.

During

constant

voltage

operation,

the

output

of

U3

is

not

positive

enough

to

forward

bias

OR

gate

diode

CR14.

However,

if

the

out¬

put

current

increases

to

approximately

104%

of

the

rated

value,

the

input

to

2

of

U3

is

driven

momen¬

tarily

less

positive.

If

this

occurs,

a

positive

going

out¬

put

signal

from

U3

forward

biases

CR14and

reverse

biases

CR13.

This

feedback

signal

then

decreases

the

conduction

of

the

series

regulator.

4-27

The

current

limiting

circuit

contains

a

current

"cutback”

feature

which

protects

the

series

regulating

transistor(s)

against

excessive

overloads.

As

the

load

resistance

decreases,

the

output

current

is

cut

back

linearly,

from

the

initial

current

limit

point,

to

approxi¬

mately

10%

of

the

rated

current

under

short

circuit

conditions

(see

Figure

4-2).

Cutback

action

is

made

possible

by

R18and

R19,

which

are

connected

across

the

output

of

the

supply,

if

the

load

resistance

de¬

creases

after

the

initial

current

limiting

point,

the

resultant

drop

in

output

voltage

causes

a

decrease

in

the

current

flowing

through

RISand

R19.

This,

in

turn,

causes

U3

to

conduct

even

harder

further

reduc¬

ing

the

conduction

of

the

series

regulator.

A.

SUPPLIES

BELOW

lOV

NOMINAL

OUTPUT

D

H

m^m

IIEBU

mam

iHsa

1111111091

^

QOI

wmm

iilBI

B.

SUPPLIES

lOV

AND

ABOVE

Figure

4-2.

Typical

Current

Limiting

Characteristics

4-28

As

described

in

Section

III,

the

cutback

point

for

the

supply

can

vary

from

approximately

3%

to

15%

of

the

rated

output

current.

Resistors

R20

and

R21

determine

the

actual

cutback

point.

4-3

4-29

Reference

Supply

4-30

The

reference

supply

is

a

small

regulated

bias

source

which

is

similar

to

the

main

power

supply.

It

contains

a

series

regulator

(Q1)

and

a

comparison

am¬

plifier

(U1).

The

three

reference

voltages

are

all

derived

from

raw

dc

obtained

from

a

full-wave

rectifier

(CR1

and

CR2)

and

filter

capacitor

Cl.

The

-F6.2V

and

-7.5V

outputs

are

developed

across

Zener

diodes

VR1

and

VR2.

The

reference

Zener

diode

(VR2)

is

temperature

compensated.

Resistor

R4

limits

the

cur¬

rent

through

VR2

to

establish

an

optimum

bias

level.

4-31.

The

regulating

circuit

consists

of

U1,

Ql,

and

associated

components.

The

voltage

across

the

reference

zener

(+6.2

V

with

respect

to

+S}

and

the

voltage

at

the

junction

of

divider

R2

and

R3

are

compared

and

any

differences

are

detected

by

U1.

The

error

voltage

is

Then

amplified

and

applied

to

series

regulator

Ql

to

counteract

the

difference

and

maintain

the

+12.4

V

output

constant.

Output

capacitor

C3

stabilizes

the

reference

regulator

feedback

loop

to

prevent

oscillation.

4-32

Zener

diode

VR1

provides

an

additional

reference

voltage

of

—7.5

V.

This

voltage

is

not

as

tightly

regu¬

lated

as

the

other

two

reference

voltages

since

it

is

not

controlled

by

the

regulator

circuit.

The

unregulated

+23

V,

taken

directly

from

the

rectifier,

is

used

only

by

Option

011

or

104

crowbar

circuits.

4-33

Additional

Protection

Features

4-34

The

supply

contains

several

"special

purpose"

components

which

protect

the

supply

in

the

event

of

unusual

circumstances.

One

of

these

is

the

output

diode

(CR9

or

U5;

refer

to

applicable

schematic).

Con¬

nected

across

the

output

terminals,

this

diode

prevents

internal

damage

from

reverse

voltages

that

might

be

applied

during

system

operation

when

one

power

sup¬

ply

is

turned

on

before

another.

The

output

diode

can

withstand

currents

equal

to

the

maximum

current

rating

of

the

supply

for

time

periods

of

short

duration

(approximately

3

minutes);

or

up

to

half

the

current

rating

of

the

supply

for

longer

time

periods.

4-35

The

series

regulator

diode

(CR8

or

U5)

protects

the

regulating

transistor(s)

from

the

effects

of

a

reverse

current

which

would

occur

if

an

external

voltage

were

applied

across

an

unenergized

supply.

4-36

Sensing

protection

resistors

R32

and

R33

pre¬

vent

the

load

from

receiving

full

rectifier

voltage

if

the

connections

between

the

output

terminals

and

the

sensing

terminals

(+S

and

—S)

are

removed

inadvertently.

4-37

Thermal

switch

TC1

opens

if

the

heat

sink

tem¬

perature

exceeds

a

safe

value.

With

TC1

open,

the

ac

input

path

to

the

supply

is

broken,

shutting

down

the

supply.

The

switch

automatically

resets

after

the

sup¬

ply

has

cooled

to

a

temperature

below

that

at

which

it

originally

opened.

The

opening

and

closing

tempera¬

tures

for

the

switch

are

given

in

the

individual

parts

list

for

each

supply.

4-4

5-1

INTRODUCTION

5-2

Upon

receipt

of

the

power

supply,

the

perfor¬

mance

check

of

Paragraph

5-6

can

be

made.

This

check

is

suitable

for

incoming

inspection.

Section

III

contains

a

quick

but

less

comprehensive

checkout

procedure

which

can

be

used

in

lieu

of

the

performance

check,

if

desired.

5-3

If

a

fault

is

detected

in

the

power

supply

while

making

the

performance

check

or

during

normal

oper¬

ation,

proceed

to

the

troubleshooting

procedures

(Paragraph

5-37).

After

troubleshooting

and

repair

(Paragraph

5-54)

repeat

the

performance

check

to

ensure

that

the

fault

has

been

properly

corrected

and

that

no

other

faults

exist.

Before

performing

any

main¬

tenance

checks,

turn

on

the

power

supply

and

allow

a

half-hour

warm-up.

5-4

TEST

EQUIPMENT

REQUIRED

5-5

Table

5-1

lists

the

test

equipment

required

to

perform

the

various

procedures

described

in

this

section.

Table

5-1.

Test

Equipment

Required

TYPE

REQUIRED

CHARACTERISTICS

USE

RECOMMENDED

MODEL

Digital

Voltmeter

Sensitivity;

lOO/iV

full

scale

(min.).

Input

impedance:

10

megohms

(min.).

Measure

DC

voltages:

calibration

procedures

HP

3450A

Variable

Voltage

Transformer

Range:

90-130Vac.

Equipped

with

voltmeter

accurate

within

1

Volt

Vary

AC

input

Oscilloscope

Sensitivity:

100/iV/cm.

Differential

input.

Display

transient

re¬

sponse

and

ripple/

noise

waveforms;

current

limit

adjust¬

ment.

HP140B

plus

1400B

plug-in.

1402A

plug-in

for

noise

measurements.

Repetitive

Load

Sw.

Rate;

60Hz,

2iisec.

rise

and

fail

time.

Measure

transient

response.

See

Figure

5-4.

Resistive

Load

Value:

See

Paragraph

5-11.

Tolerance:

±5%

Power

supply

load

resistor.

(Fixed

re¬

sistor

or

Rheostat).

James

G.

Biddle

“Lubri-

Tact"

Rheostat

41lG23CSor411G85CS.

Current

Sampling

Resistor

(Shunt)

Value:

See

Paragraph

5-13.

Accuracy:

1%

(minimum)

Measure

output

current

Simpson

Portable

Shunt,

06704.

5*6

PERFORMANCE

TEST

5-7

The

following

test

can

be

used

as

an

incoming

inspection

check

and

appropriate

portions

of

the

test

can

be

repeated

to

check

the

operation

of

the

instru¬

ment

after

repairs.

The

tests

are

performed

using

the

nominal

120VAC,

60Hz,

input

power

for

the

unit,

if

the

correct

result

is

not

obtained

for

a

particular

check,

proceed

to

troubleshooting

(Paragraph

5-37).

5-12

Either

a

fixed

or

variable

resistor

(rheostat)

can

be

used

as

the

load

resistance.

A

rheostat

is

very

useful

when

measuring

the

output

current

of

the

supply

and

also

is

a

convenience

if

the

user

is

testing

a

number

of

modular

power

supplies

of

different

ratings.

A

rheostat

of

the

type

recommended

in

Figure

5-1

is

adequate

for

any

supply

covered

by

this

manual,

if

a

fixed

resistor

is

used

for

output

current

measurements,

its

tolerance

must

be

accounted

for

in

evaluating

the

test

results.

5-8

Measurement

Techniques

5-9

Connecting

Monitoring

Device.

For

the

following

Constant

Voltage

measurements,

the

measuring

device

must

be

connected

across

the

rear

sensing

terminals

of

the

supply

in

order

to

achieve

valid

indications.

A

mea¬

surement

made

across

the

load

includes

the

impedance

of

the

leads

to

the

load

and

such

lead

lengths

can

easily

have

an

impedance

that

is

greater

than

the

supply

im¬

pedance,

thus

invalidating

the

measurement.

To

avoid

mutual

coupling

effects,

each

monitoring

device

must

be

connected

directly

to

the

sensing

terminals

by

separate

pairs

of

leads.

5-10

Avoid

Current

Limiting.

When

measuring

the

constant

voltage

performance

specifications,

the

current

limit

point

should

be

set

at

least

3%

above

the

maxi¬

mum

output

current

which

the

supply

will

draw,

since

the

onset

of

current

limiting

action

will

cause

a

drop

in

output

voltage,

increased

ripple,

and

other

changes

not

properly

ascribed

to

the

constant

voltage

operation

of

the

supply.

The

current

limit

potentiometer

is

fac¬

tory

set

to

its

proper

value

when

the

supply

is

provid¬

ing

nominal

output

voltage.

If

an

output

voltage

other

than

nominal

is

selected,

read

Paragraph

3-8

and

then

proceed

to

the

current

limit

adjustment

procedure.

Paragraph

5-72.

5-11

Selecting

A

Load

Resistor.

Constant

voltage

specifications

are

checked

with

a

"full”

load

resistance

connected

across

the

supply.

The

resistance

and

wattage

of

the

load

resistor,

therefore,

must

permit

operation

of

the

supply

at

its

rated

output

voltage

and

current.

For

example,

a

supply

that

is

rated

at

4

±

0.5

volts

and

4

amperes

would

require

a

load

resistance

of

1

ohm

at

the

nominal

output

voltage

(4V).

If

the

out¬

put

voltage

were

set

to

one

of

the

adjustment

limits

(4.5V

or

3.5V),

the

load

resistance

would

have

to

in¬

crease

or

decrease

accordingly,

to

allow

the

unit

to

provide

its

rated

current

of

4

amperes.

The

wattage

rating

of

the

1

ohm

resistor

would

be

4

watts,

minimum.

5-13

Output

Current

Measurements.

For

accurate

out¬

put

current

measurements

a

current

sampling

resistor

should

be

inserted

between

the

load

resistor

and

the

output

of

the

supply.

An

accurate

voltmeter

is

then

placed

across

the

sampling

resistance

and

the

output

current

at

any

time

can

be

calculated

by

dividing

the

voltage

across

the

sampling

resistor

by

its

ohmic

value.

The

total

resistance

of

the

series

combination

(sampling

resistor

and

load

resistor)

should

be

equal

to

the

full

load

resistance

as

determined

in

the

preceding

para¬

graphs.

Of

course,

if

the

value

of

the

sampling

resistance

is

very

low

when

compared

to

the

full

load

resistance,

the

value

of

the

sampling

resistance

may

be

ignored.

The

meter

shunt

recommended

in

Table

1-1,

for

example,

has

a

resistance

of

only

5

milliohms

and

can

be

neglected

when

calculating

the

load

resistance

of

the

supply.

5-14

Figure

5-1

shows

a

four

terminal

meter

shunt.

The

load

current

is

fed

to

the

extremes

of

the

wire

lead¬

ing

to

the

resistor

while

the

sampling

terminals

are

lo¬

cated

as

close

as

possible

to

the

resistance

portion

itself.

Figure

5-1.

Current

Sampling

Resistor

Connections

5-15

Rated

Output

5-16

Voltage.

To

ensure

that

the

supply

will

furnish

the

maximum

rated

output

voltage,

proceed

as

follows:

a.

Connect

digital

voltmeter

across

+S

and

-S

terminals

of

supply

observing

correct

polarity.

5-2

b.

Apply

input

power

to

supply.

c.

With

no

load

connected,

set

output

voltage

of

supply

to

any

value

desired

within

adjustment

span.

This

output

voltage

can

be

used

for

ail

remaining

con¬

stant

voltage

tests.

d.

With

supply

off,

connect

full

load

resistance

across

+

and

-

output

terminals

of

supply

(see

Para¬

graph

5-11).

e.

Reconnect

input

power

to

supply.

Voltmeter

should

read

output

voltage

set

in

Step

c

(within

tol¬

erances

of

load

resistor

and

meter).

5-17

Current.

To

ensure

that

the

supply

will

furnish

the

maximum

rated

output

current,

proceed

as

follows:

a.

C

onnect

test

setup

shown

In

Figure

5-2.

Select

load

and

current

sampling

resistor

values

according

to

Paragraphs

5-11

and

5-13.

b.

Apply

input

power

to

supply

and

adjust

Rl

until

digital

voltmeter

indicates

a

voltage

drop

which

is

proportional

to

the

maximum

rated

output

current,

5-18

Load

Regulation

Definition:

The

change

AE

out

the

static

value

of

DC

output

voltage

resulting

from

a

change

in

load

resistance

from

open

circuit

to

a

value

which

yields

maximum

rated

output

current

(or

vice

versa).

5-19

To

check

the

constant

voltage

load

regulation,

proceed

as

follows:

a.

C

onnect

full

load

resistance

across

rear

output

terminals

(Paragraph

5-11).

b.

Connect

digital

voltmeter

across

±S

terminals.

c.

'Turn

on

supply

and

obtain

desired

output

voltage.

Record

voltage

read

on

voltmeter.

d.

Disconnect

load

resistance.

e.

Reading

on

digital

voltmeter

should

not

vary

.

from

reading

recorded

in

step

c

by

more

than

0.01

%

or

ImV,

whichever

is

greater.

5-20Line

Regulation

Definition:

The

change,

AE

qut

f

value

of

DC

output

voltage

resulting

from

a

change

in

AC

input

voltage

over

the

specified

range

from

low

line

(usually

104

Volts)

to

high

line

(usually

127

Volts),

or

from

high

line

to

low

line.

5-21

To

test

the

line

regulation,

proceed

as

follows:

j;

a.

Connect

variable

auto

transformer

between

|

input

power

source

and

power

supply

power

input

|

terminals.

b.

Connect

load

resistance

and

digital

voltmeter

across

output

of

supply.

c.

Adjust

variable

auto

transformer

for

low

line

input.

d.

Turn

on

setup.

Read

and

record

output

volt¬

age

on

digital

voltmeter.

e.

Adjust

variable

auto

transformer

for

high

line

input.

f.

Reading

on

digital

voltmeter

should

not

vary

from

reading

recorded

in

step

d

by

more

than

0.01%

or

ImV,

whichever

is

greater.

5-22

Ripple

and

Noise

Definition:

The

residual

AC

voltage

which

is

superimposed

on

the

DC

output

of

a

regulated

power

supply,

Ripple

and

noise

may

be

specified

and

measured

in

terms

of

its

RMS

peak-to-peak

<

value.

<

5-23

Ripple

and

noise

measurement

can

be

made

at

any

input

AC

line

voltage

combined

with

any

DC

out-

j

put

voltage

and

load

current

within

rating.

|

5-24

Figure

5-3A

shows

an

incorrect

method

of

mea-

(

suring

p-p

ripple.

Note

that

a

continuous

ground

loop

!

exists

from

the

third

wire

of

the

input

power

cord

of

|

5-3

the

supply

to

the

third

wire

of

the

input

power

cord

of

the

oscilloscope

via

the

grounded

power

supply

case,

the

wire

between

the

negative

output

terminal

of

the

power

supply

and

the

vertical

input

of

the

scope,

and

the

grounded

scope

case.

Any

ground

current

circulat¬

ing

in

this

loop

as

a

result

of

the

difference

in

potential

Eq

between

the

two

ground

points

causes

an

IR

drop

which

is

in

series

with

the

scope

input.

This

IR

drop,

normally

having

a

60Hz

line

frequency

fundamental,

plus

any

pickup

on

the

unshielded

leads

interconnecting

the

power

supply

and

scope,

appears

on

the

face

of

the

CRT.

The

magnitude

of

this

resulting

signal

can

easily

be

much

greater

than

the

true

ripple

developed

between

the

plus

and

minus

output

terminals

of

the

power

supply,

and

can

completely

invalidate

the

measurement.

POWER

SUPPLY

CASE

OSCILLOSCOPE

CASE

A,

INCORRECT

METHOD-GROUND

CURRENT

IG

PRODUCES

60

CYCLE

DROP

IN

NEGATIVE

LEAD

WHICH

ADDS

TO

THE

POWER

SUPPLY

RIPPLE

DISPLAYED

ON

SCOPE.

POWER

SUPPLY

CASE

OSCILLOSCOPE

CASE

B.

A

CORRECT

METHOD

USING

A

SINGLE-ENDED

SCOPE.

OUTPUT

FLOATED

TO

BREAK

GROUND

CURRENT

LOOP,

TWISTED

PAIR

REDUCES

STRAY

PICKUP

ON

SCOPE

LEADS-

POWER

SUPPLY

CASE

OSCILLOSCOPE

CASE

C.

A

CORRECT

METHOD

USING

A

DIFFERENTIAL

SCOPE

WITH

FLOATING

INPUT.

GROUND

CURRENT

PATH

IS

BROKEN;

COMMON

MODE

REJECTION

OF

DIFFERENTIAL

INPUT

SCOPE

IGNORES

DIFFERENCE

IN

GROUND

POTENTIAL

OF

POWER

SUPPLY

a

SCOPE,

SHIELDED

TWO

WIRE

FURTHER

REDUCES

STRAY

PICKUP

ON

SCOPE

LEADS,

figure

5-3.

Ripple

and

Noise,

Test

Setup

5-25

The

same

ground

current

and

pickup

problems

can

exist

if

an

RMS

voltmeter

is

substituted

in

place

of

the

oscilloscope

in

Figure

5-3,

However,

the

oscillo¬

scope

display,

unlike

the

true

RMS

meter

reading,

tells

the

observer

imrriediately

whether

the

fundamental

period

of

the

signal

displayed

is

8.3

milliseconds

{1/120Hz)

or

16.7

milliseconds

{1/60Hz).

Since

the

fundamental

ripple

frequency

present

on

the

output

of

an

HP

supply

is

120

H

2

(due

to

full-wave

rectification),

an

oscilloscope

display

showing

a

120Hz

fundamental

component

is

indicative

of

a

"clean”

measurement

set¬

up,

while

the

presence

of

a

6

OH

2

fundamental

usually

means

that

an

improved

setup

will

result

in

a

more

accurate

(and

lower)

value

of

measured

ripple.

5-26

Figure

5-3B

shows

a

correct

method

of

measur¬

ing

the

output

ripple

of

a

constant

voltage

power

supply

using

a

single-ended

scope.

The

ground

loop

path

is

broken

by

floating

the

power

supply

output.

Note

that

to

ensure

that

no

potential

difference

exists

between

the

supply

and

the

oscilloscope,

it

is

recommended

that

whenever

possible

they

both

be

plugged

into

the

same

ac

power

buss.

If

the

same

buss

cannot

be

used,

both

ac

grounds

must

be

at

earth

ground

potential.

5-27

Either

a

twisted

pair

or

(preferably)

a

shielded

two-wire

cable

should

be

used

to

connect

the

output

terminals

of

the

power

supply

to

the

vertical

input

term¬

inals

of

the

scope.

When

using

a

twisted

pair,

care

must

be

taken

that

one

of

the

two

wires

is

connected

to

the

grounded

input

terminal

of

the

oscilloscope.

When

using

shielded

two-wire,

it

is

essential

for

the

shield

to

be

con¬

nected

to

ground

at

one

end

only

to

prevent

ground

current

flowing

through

this

shield

from

inducing

a

signal

in

the

shielded

leads.

5-28

To

verify

that

the

oscilloscope

is

not

displaying

ripple

that

is

induced

in

the

leads

or

picked

up

from

the

grounds,

the

(+)

scope

lead

should

be

shorted

to

the

(—)

scope

lead

at

the

power

supply

terminals.

The

ripple

value

obtained

when

the

leads

are

shorted

should

be

subtracted

from

the

actual

ripple

measurement.

5-29

In

most

cases,

the

single-ended

scope

method

of

Figure

5-3B

will

be

adequate

to

eliminate

non-real

com¬

ponents

of

ripple

so

that

a

satisfactory

measurement

may

be

obtained.

However,

in

more

stubborn

cases,

(or

if

high

frequency

noise

up

to

20MHz

must

be

measured),

it

may

be

necessary

to

use

a

differential

scope

with

floating

input

as

shown

in

Figure

5-3C.

If

desired,

two

single-conductor

shielded

cables

may

be

substituted

in

5-4

HP A Series Service manual

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