HP SCR-1P Series Service manual

Errata
Title & Document Type: 6448B DC Power Supply Operating and Service Manual
Manual Part Number: 06448-90001
Revision Date: April 1968
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DC POWER SUPPLY
SCR-1P SERIES
MODEL 6448B
.1.
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OPERATING AND SERVICE M/1.NUA1
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FOR SERIALS 610182 -0241*
\ • ' 1"
*For Serials above 610241
Check for.inclusion of
*For 9erials B,elciw 610182
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change page.
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. Refer to Appendix A.
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100 Locust Avenue,. Berkeley Heights,
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NeW Jersey 07922.
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.._ __ ...;.. _____ , _________ _;..i.... __ ..;..; ________ ..;_ ___ ~
.HP Part No. 06,448'.:~0001 \ '\
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Printed: April, 1968
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TABLE OF CONTENTS
Section' , Page No.
I
GENERAL INFORMATION •••••••••••• l-1
' l7,l I De,scriptlon , ,, 1-1
1-4 Operating papabllltles
1
',171
1-~0 Specifications '\'-2 :,
1-112 Options h2
1,!.14 lMtrument/Manual Identlflca-
' '
t;, /. tlon
/1-17 Ordering Additional Manuals
1-2 '·
1-2.
II INSTALIA'l'ION ••••••• , ••••••••.••• 2-1
2-1
2-3
2-5
2-7 ·
2-9
2-11
2-13
'2-15,
2-17
2-19
2·~22
Initial Inspection
Mechanlca l Check
Electrical Check
Installation Data
l.ocatlpn
P.ack Mounting
Input Power Requirements
Modifications for 208 or
230Vac Operation·
50Hz Operation
Power
Cable
Repackaging f~r Shipment ·
2-1
2-1
2-1
2-1
2-1
2-1
2-1
2-1,
2-1
2-1
2-1
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I'I I OPERATING INSTRUCTIONS ••••• : ••• 3-,l
3-1 . Turn-on
Checkout Procedure 3-1
3'_3 ,Operating Modes 3-1 ·
3-5 Normal Operating Mode
3'-1 ,/,'
3-7
Constant Voltage 3-2,
· 3-9 Constant Current ,·
1• ' '
37,2
3-11 Connecting Load 3-2
3-14 Operation of Supply Beyond ;':1 ·
Rated Output ' ~.::2
3-16 Option~! qperatlng :Modes , ,'./~~2 ,
3-17 Remote· Programming,
Con- ;!' ',
stant Voltage f"' 3-2
3-24 Remote Progrilmn\lng,' Con- .
· 3-29'
3-33
, ·3-37
3-40
, 3-41
3-43
3-46
stani Current ·
Remote
Sensing
Parallel Opemtlon
Auto-Tracking Operation
Special, Operating
Consider-
ations ,
Pulse Loading
··
Output Capacitance
Rever~d Voltage Loading
3-3
3-3
3-4
3-5
3-5
3-5
3-5
3-5
Section , Page JI/~.
I II OPERATING INSTRUCTIONS (Cont'd.) • '
3~48 Revers~ Current Loading
3-6
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. i IV 'PRINCIPLES OF OPERATION •••••••• 4-1
l ii
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•4-1 Overall Description 4-1,
4-12 Detailed Circuit Analysis 4-3
4-13 AC Input , ' ' 4-3 ·
4-15
DC ouiput, i' 4-3,
4-1,1 Feedback Loop 4-3
4-22 Voltage Gomparlson Amplifier 4-3
'4-25 Current Comparison Amplifier 4,-4
4-28 Gating Circuit 1 4;.4 :,
4-31 SCR Regulator Control
4-4
1:
• I
4,-39, SCR Regulator , ;, , , 4-5,
4-44 Bla:s and Referencti Circuit 4-6 '
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V, · MAINTENANCE.• ••••••• ,, •• , •••• , •• , 5-1
',·5-'l' •Introduc~lc,n : : 5-1
,5~3 Tdsi E'qJlpment Re'qu!/ed 5-1 ·
5~5 Perform~nce Test: f . , 5-2,
5'-7 Cbnstar,t Voltagel:Tests 5-2 ·
5.~~3 Output1 Impe9an7~ . ;·. 5-6
5'-43 Constant Current ·10sts , 5-8
5-,50' Troubieshootlng , ' 1 5-9 .
5-55
Overall Troubleshooting Pro-
'1
1 cedure 1 ,
5-9
I I
5-59 Repair and Replacement · 5-11
5~61, Adjus,tment.and/Call~ratlon
/.· 5-'ll
5-63, Meter. Zero · I ·· , , , 5-12
,, !5-65 1/oltmet~r'Adju~tme!'\t,, . 5-12'
/
5:_57 Ammeter Adjustment• ; • , 5,-12' ',
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5-69' Voltage Programming Accuracy 5-12 , ,
5-71 Current Progiammlng
Acdracy 5-14 '·,\'•
5-:;73 ·~anslentRecovery; Time 1
•
5-14
5-'75, Overvoltage,,Protectlon Adjust- ' I,
I ' I ' \
/ ' '/ ment , ·. . i 1 , / 5-14
/5-77:i Ripple lmbalance1 ~djust~ent
1
5;-14
,YI REPLACEABLE PARTS •• :.: •••• i ••••• , 6-1
6f4 Ordering Information ,:' 6-1
,1;
) /' ' '
VI I CIRCUIT DIAGRAMS ••••••• I?' •• • •. 7-1
: I
APPENDIX A ••• , •••••• .' ••••••• ,,.: •••• ,. A-1
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,LIST OF TABLES
Table
'' 1-1 Specifications,
5-1 Tost Equipment Required
5-2 Reference and Bia~ Voltages
5-3 Overall Troul1leshootlng ,
5-4 low output Voltage Tro,ubleshootlng ·
5-5 High Output Voltage Troubleshooting
6-1 'Reference Designators ·
6-2 Description Abbreviations
6-3 Code List of Manufacturers
6-4 Replaceable Parts, ,
LIST OF ILLUSTRATIONS
Page No.
1,-2
5-1
I 5-9
5-10·
5-11
5-12
6-1
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· 1'.,
Flgur, ·
1-1
Page No,
1.:1
3-1
DC Power Supply, Model 6.448B
Front PaneI ContraIs and Indicators
NormaI Strapping PattP.rn
1., '
Figure , '1' P,~ge NO: '
5-1 Differential Voltmeter Substitute · 1
3-i
3-2
3-3
3-4
'3-5
13-;-6
3-7
, 3-B
3-'9
4.;.1,"
4-'2',
4-3
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Remote Resistance Programming
Remote Voltage Programming
·(Constant Voltage)
Remote
Resistance Programming
,. . (Constant Current) . .
Re'mote Sensing · ':. '
Normal Parallel Connections
Auto Parallel, Two and Three Units
Auto Tracking,Two·and Three Units
OveraUiJlock Diagram
· Operdtlllg
locus of a CV/CC
, Power Supply
SCR Regulator Control, Timing
Diagram
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3-2
3;2
3-3
3-3
3-4
3-4
3-4
3-5
4.:1,
,,·
4-2
' 4-4
I
·,'
,IV
Test Setup' 5-2
5-2 ··.Front Panel Terminal' Connections 5-3
5-3 Constant Voltage To~t Setup 5-3
,,
5-4 CV Ripple and Noise', Test ,Setup 5-4
5-5
. CV Noise Spike, Tost Setup 5-5
5-6 ; Transient Recovery'Tlme, Tost' Setup 5-6·
5-7 Transient Recovery Time, Wave-
'5-B
5-9
I 5-}Q'
5-ll
5-12
1 forms'
Output, ImpPdance, Test Setup
Outpu't Current Measurement
.
,5-7
5-7
, 'j'echnlquo . ,
Output Current, Test'Setup '
Servicing Printed Wiring,Boards,
Rlppl" Imbalance Waveform
: ' /' ·, '' ,'' .-.i .':\\'-!
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5-8
5-B ,
5-13
5-14
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SECTION i'
GENERAL INFORMATION
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Figure 1-1. DC Power Supply, Model 6448B
'
1-1 DESCRIPTION
1-2 This power supply, Figure 1-1, is co'mplet~-
ly transist.:irized and sulti}ble for bench or rack op-
eration. It is a well-regulated, Constant Voltage/
Constant Current supply that wUl furnish full rated
output voltage at the maximum rated output.current
or can be continuously adjusted throughout the r.,\Jt- ·
put range.' The front panel CURRENT controls 'can
be used to establish the output current limit (over:.
load
or.short clrcult)when the supply' is used,as a
constant voltage. source and'the VOLTAGE contra1
can be •1sed to establish the rnltage 1'tmit when the
supply :is used as a constant current source. The
supply\vUl automatically crossover 'from constant
voltage to constant cµrr'ent operationand vice-
versa if the output current or voltage exceeds tho
limits
established by these controls.
1-3 Output voltage and current can be continu-
ously monitored on the two.front panel mete~s. · ,,
.The power supply !:as both front an_d rear output
terminals. Either the positive or negative output
terminal may be ground,ed
or the pc;,wer supply can '
' '
' ,·
,,
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, ' ' I ,
be oper11ted Ilo11ting at up to amaximum of 300
· Volts off ground. ;
1-4, OPERATING CAPABILITIES
' '
1-5 Terminals at the rear of the unit allow ac-
<:ess-,to various control points within the unit to
expand the operating capabilities of the lnstrumcmt.
A
brl_ef description of these capabilities ls given
below.
1-6 Remote Programming. Tho power supply may
be programmed (controlled) from a romoto location
by mea,ns
of an external voltage sourco or resist-
' ' '
unce.
1•.:.7 · Remote· Sensing. The degradatlon·,in reguln-
1ion which would occur at the load because, of the
voltage· drop In the load leads can be,;educed by
using the power
supply lri the remote sensing
mode _of operation•
,: :, l;:8, l.uto-Parallel Ope~atlon. Th~ pO\~~r supply.,
ri1ay be operated 'in Auto-Parallel with a similar
, '' '
,)
' '
''
.,
1-1
'"
,,
'· ,\II,
,.
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unit
when greater output current
capabllity
Is
re-
quired. Auto,'Parallel operation permits one,knob
control
of
the
totaloutput
current>from a "master"
supply. , '
1-9
Aut~-Tracklng. The power supply,
may
be
used
as
a "master" supi,ly, having
control
over
one
(or more)
"slave"
supplies
that
furnish
varl-
,,
ous
voltages
for a
system.
· ' ,
,,
'
t-10
SPECIFICATIONS
1-11,
,Detailed
speclflcatl~ns
for' the pow~r sup'..
'p\y
are
gl~-cn
ln Table
1-1.
,
,,
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i'-12
OPTl9NS
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18
'
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,·,1,
',,
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'
,
stallatlon
of
208
Volt Input power
transfor!per~.,.b1as
tra~sformer.
and
' '
SCR's to'
replace
the standard
'us
or'
~3q
Vo
It compopents.
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.
'230Vac
±10%
1
Single
Phase
Input.
.,
Factory modification Includes
the
In-'
stallatlon
of
'a
230
Volt,lriput
power'
transformer,
bias
tr~risformer,
'and
',
'
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,
SCR
1
s to
replace
,the standard 115
cir
·
''"
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·'
'
230
Volt compon
7
,n\s·'
1, ' ·
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1-14
INSTRUMENT/MANUAL
IDENTIFICATION
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1-15 Hewlett:.Packard power
supplies
are
!dent!-
,\
fled by a three-p~rt serial, nu~ber tag;' The
first
' 1' ' \ 1 ,
part
ls
the
power'supply model number. The
sec-
\'
\'
1-13
Options are factory modifications
of
a
stand-
ar,~
Instrument
that
are
reC).iested by the'
cust9mer;
1
The following
options
are
available
for,
the
lnstru-
ond part
Is
the,
serial
number prefix;\y,lilch conJ. '' \ \
,',
s\sts
of
a number-letter:comblnatlon1\h,at
denotEi~
, '
the
date
of a
significant
design
change.
The num-
,ment covered by
this
manual. Where
necessary,
'detaJl~d cov~rage
of
the options .ls Included
throughout the ·manual. ' ,
'
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'I.,,
De
scrlpt!on
Option No.,
05
50Hz Regulator Realignment.
Stand-
ard Instruments wUI opera\\!
,satlsfac
7
torlly
at
both
60,and 50Hz
without
/1
adjustment. However, Option
05
fac-
,1
tory
reallgnment'results
In ,more
effi-
cient
operation
at
50Hz,
and
Is
recom-
mended for
all
applications
wheri
con-
tinuous
operation
from
a SOHz
,i'c
Input
ls
Intended. ' /
10
)
'
'
' '
Chassis
Slides.
Enables
convenient
access
to power su'pply ln\~rlor
tor'
,
maln~enance purposes.
Slldes•are
at-
17
INPUT:
tached
at
the factory. / ,
'
'
'
' 208Vac
,HO%,
Single Phase Input.
Factory modification h\cludes the
In-
,
'
/
'
'
/'
i
llSVac
:U0%,
57-63Hz,,
single
phase,
16 Am-'
peres,
1200
Watts
maximum.
,,'
OUTPUT:
0-600
Vo:ts@
0-1.
5 Amperes.
'
LINE'
REGUIATION:
Constant
Voltage -Less than
600mV
for a
change
In,
line
voltage
from
~03.,5
to 126. 5 (or
1,26.
~
to 103.
~).
, ,
1-2
,
ber
designates
the
year,
anti the leUer Athrough
I~,
deslgnates
1
the month, ranuary through Dec
7
mber, \ \ ; ,
respective
y,
with "I" omitted., The third
part
Isl
;''
", '
the
power,supply
serial
number; a different sequen~
tlal
null)ber'Is
assigned
Jo
each
power supply. ,
I
1-16
If the
serial
number on
you/
lnstr~ment doe~
1
1
not agree y,lth t)lose on the
mle
page
of
the
man- '
ua,,, Change ShRets supplied with the manual
or
Manual Backdating Clianges
In
Appendix A define I
the
differences
beMeen
your Instrument and the
1
\
lnstru".'ent described
by
this
manual.,
1-17
.
ORDERING
ADDITIONAL
MANUALS
I
I
'1-18
'•on,e
manual Is shipped with
each
power ,
supply.' Additional manuals may pe
purchased
from
'your local Hewlett-Packard
sales
t>fflce (see
list
,
at
rear
of
this manual for
addresses).
Specify ihe
model number,
serial
number pr~flx,
'and
t$j
part '
number provided on the
title
page.
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,Constant Current -Less than
lSmA
for a
change'
In' line voltage
from
103. 5 to 126. 5 (or 126. 5 to ,
10~. 5). , ,
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LOAD
REGUIATION:
,
,. Co~stant Voltage
-·Less
than
600mV
for
1,1,change
in ou•,put current
from
no load to full load
or
full ,
load
11'
no
load. ,
Constant
Current -Less than
lSmA
for a
change
In output voltage
from
no
load to full load
or
full
load to
no
load. '
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Table'
lJ.l:
Specification~ (C~ntlnued)
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r----:-.:-,~----'-----'----'---'--------r....;.---',,_.;.---~-....;.---....;.----:....
'
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IUPPLE
AND
NOISE:
"'
""
,Less
than
600mVrms/2Vp-p (de to 20MHz).
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LOAD
TRANSIENT
RECOVERY:
"Less than 200nisec ls,requlr~d for output
voltage
r~covery to within 30oomy
of
the nominal
output,
voltage following a
loe:l
change
from
fu!Uoad
lo
:'half
load or,half
loa,d
to
foll
load,. ~xcludln9
~he
':
lnltlarnarrow
spike
of
approxlrr,a,tely
l00µsec
,
I
duration (significant
only
with
ioad rise times.
faster
than
0. lA/µsec),
the
transient
amplitude
wlll
be
le.ss thnn'.20 Volts/Amp for any load
'change,between''20%
and
100%
of
rated output
cur-''
,rent~
1'
.
I,
1
LINF.,
TRANSIENT
RECOVERY:
Less
than
200msec
Is
required for output
volt-
age recc.1ery
to
within
30
Volts
of
the nominal
olltput voltage following a change
In
the nominal
line
voltage
fro~ 1~3. 5
~
1.26.
SVac.
,,
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TEMPERATURE
RANGES:
dperatlng:
ooc
to
550c.
~tcirage: -400C to
+7soc.
TEMPERATURE
COEFFICIENT:
Constant
Voltage -
Less
than
(O.
03%
+ l00mV)
output
change
per degree centigrade change In ,
ambient following
30
minutes warm-up.
'
Constant
Current -'Loss than
SmA
output
change
per degree centigrade
change
In
ambient folio'?'- ,
fog
30
minutes wnrm-up.,', , ,
,,
.
STABILITY:
,, , ,
• ' ' \ '
..
l '
Constant,Voltage -
Less,than
o.
1%
+300mV
total
drift for 8,hours following
30
minutes '('arm-up
,under
constant
ambient,
constant
line
voltage,
and
constant
lciad. '
Constant,Current-,,Less
than 15m~ total drift
fer''
8 hours following
30
minutes warm7up under con-'
stant
ambient,
constant
line voltage, and
constant
load. ' '
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INTERNAL
IMPEDANCE
AS
A
CONSTANT
VOLTAGE
SOURCE:
, \
Less
lhan
0. 5 ohms
from
DC
to.
0. 5Hz.
Less
than
s.
0 ohms irom 0.
SHz,
to l00Hz.
Less than•3.'5 ohms
from
l00Hz to
lkHz.'
Less
than
s.,0 ohms from
lkHz
to
l00kHz.
METERS:
Afront panel voltmeter,(C-700V) ~nd ammeter
,(0-1'.
SA)
are provided.
'Meters
haVe"2%
accuracy:
,
all
units
have meter c1;1llbratlng potentiometers.
i '
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OUTPUT
CONTROLS:
, , ,
,,
,
1
1
q~Tum voltar1e ancl'slngle-tpm current
controls
lo•
1,ted
on
the/.
rent panel perr~lt continuous
B;d-
ju
,
Tent
of
tlie ~utput voltage and current from
ze,~
1
to
the
maximum,
output
rating
of
the supply.
'
/:
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OUTPUT
TERMINALS:
, , ,
' '
'
,,An
output
l:Jarrler strip
located
on the
rear
of
the
r.hassls
lncJudes de o'utput
termlnals'as
well
as
,
all
necessary
terminals for' remote erior
sensing,
remote programming, Auto-Parallel,
etc.
Either
tljeposltlve
or
negative terminal
may
be
connected
to ,the
chassis
via
a
separate
ground terminal
or
' . the
supply
may
be' operated ~loatlng
at
up to
600'
' Volts
off
ground. Front,
panel
terminals may be
used,for
monitoring purposes
cr'for
loods up to
3 Amperes.
,,
'ERROR
SENSING: ,
Error
sensing
Is
normally accompllsh~d,
at
the
front terminals If the load
Is
attached, to the front
,
or
at
the
rear
termInaIs If
the
load Is
attached
to
the
rear
terminals.,, Also, provision ls' inc,luded
on
t)le
rear
terminal strip for remote se'rislng. '
RESOLUTION:
,
,
Constant
Voltage -
60mV,minlmum
output
change
that
can
be
accomplished by the ,front panel
out-
,
,,.,~,ut
control.
Constant
Current -
o.
75inV
minim.um
output
change
that
can
be accio~pllshed
by
the
front
,
panel
output
control.
REMOTE
,PROGRAMMING:
,
Constant
voltage remote programming
ls
approx-
' !mate
ly
300 ohms per
Vo'lt,
wIth
an
accuracy
of
2%.
In
constant
current mo.de'.cif'operatlori,
the
current
can
be remotely progratnmed
at
approximately 600
ohms
per
Amp
with
6%
adcuracy. Remote program-
ming'control
ls
accomplished
either
with Input
.-eslstance
or
lnp,ut voltage.
1 '
, I
CdOL!NG:
I
,The
unit
Is
coolefl by forced
air
from
an
intema
I,
fan.
SIZE:
5-1/4"
H x
16-3/4"
D x,19"
w.
The
unit
can
be
mounted
In
a standard 19',' rack panel.
WEIGHT:
61,lbs. net. 70
lbs.
shipping.
'
'
FINISH:
Ught
gray front panel with
dark
grayc~se.
,,
1-3

' ·,
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1:
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·. I SE~TION II
\ I
I
I " .I '',
f 1NSTALLATION '
"I!
/
2-1 INITIAL INSPECTION
'
' ''1'' ,' . ' ,,'
2-2( Before shipment, this Instrument was In-
\ '_;'
spected and fo(lnd to be free of mechanical. and
I ' "
1,
electrical defects •. As soon as th!! Instrument Is
'( . ' '
.;, ,.unpacked, Inspect for any dama~e that may have
occurred In transit. Save all packing materials
, 'until the Inspection Is completed. If damage Is,
'1 found, proceed as described In the Claim for Dam-
1, age In 'Shipment section of the warranty page at · ,
t!Je rear or this manual. /, '.· ' '
' :1J' I
2-3, MECHANICAL CHECK:
2-4 This check stould confirm that there are ~o
broken 'knobs' or connectcirs. thatthe cabinet ,and
·'p;)nel
surfaces are- free of· dents and scratches;
,1,:' '' ' ' ) '
and that the meters·are not scratched.or cracked.
I, S ' '
2-5
,,
ELECTRICAL CHECK
2-6, ·
Th!! Instrument sho\Jld be checked against, ,
Its electrical specifications. Section V Includes'
an "In-cabinet" performance check 'to verify, I
\
,1 ' I I
I , J , / 1
wired for 115 Volt1 operatlon. The Input power re-
quired when operated from a ll5Vac, 60Hz power
sou'rce,ls 1200 Watts, .16 Amps. · '
,, •,I , , / / ; '
2~15 MOmFICATIONS FOR 208 OR 230VAC OPERA-
TION
1
,· ,
1
\ '
1
. f' ,'. ',/ I .' • I ' ' , / '
2-16 ·.The supply Is normally, shipped with a ll5Vac ,,'
. ·'Input; For Option 17 01 18, 208 or 230Vac lnp'ut; ,
't~ansformers 'Tl' and T2,
·scRs CiU7 and CRIB, and
. I . .
resistors R21 .. and R58 should ba replaced. Part ,.
Information, is given In Table,6-4 under Optlo'ns 17
,~tdlB.
1
,(:·· _1 ,'•··.·)/
, ,'/2-17 /OHZ OP,E~TIO~ / .
•,' 2-18' To permlt,optlmum operation at 50Hz, the
~Htpu~,tll;'ple lm~alan9e must be ,realigned as de- .
, ·scrlbecl,11) P~ra,grap~5-78i . · . . .
' / I ' I
2-19 f'OWER CABLE
1
' ' '
, ·2-20. To.protect',operatlng perso~nel, the National
.· Electrlcat:M'aniifacturers' Assoclatl~n' (NEMA) rec-
•• . I , I
proper Instrument operation. . ,
·,I , . , i1
'ii,.'
ommen,ds that',the lnst"lment panel ~nd cabinet be ,
grounded, This lnstru111ent
ls equipped with a three
conductor power cable;° The third cond~ctor ls the '
'ground co_ndu~tor a~d
when the cable, Is 'plugged
Into an appropriate·
receptacle, the Instrument' ls
grounded. The offset pln'on the p'ower cable
2-7 INSTALI.AT!ON DAT~, ,, , , ·
2-8 ,· The lnstru,~en; Is 'shipped, ready for bench
operation. It Is necessttry only to' c_onnect. the
Instrument to a source of power and It Is ready
,, for operation.. 1 \ '·,,,, '
I'
2-9
LOCATION
2-10 This· Instrument Is cooled by forced air from
the ·cooling fan. It should not be used In an area
where the ambient temperature may exceed 55°c •.
2-ll RACK' M6UNTING
' ' ' ' '
2-12 This lnsiniment ls full rack size and can be
easily rack mounted In a conventional 19 Inch
rack pa.lei using standard mounting screws.'
/ I , '·,
2-13 •INPUT POWER REQUIREM~NTS
2-14 This power supply may be ,operated from a
• , • I
n6mlrial ll$V, 208V, or 230 Volt, 57-63Hz power
·,
source. The unlt,as ·shipped from th~ factory, ls·
' I
2-1
, I . ' . '
three-prong ·connector Is the ground connection.
/ ', ' ' : ' l ' •
2-21/ To preserve the protection feature when op-
erating the Instrument fro111 a two-contact outlet,
use' a three-prong to two-prong adaptei and con-,
nect the green lead on the adapter to ground.
' '
2·22 REPACKAGING FDR' SHIPMENT .
2-23 To Insure ,safe shipment of the lnstn•.ment, it
ls recommended that the package designed for the
Instrument be used. The ~rlglnal packaging mate-
rial ls reusable, If it Is .not available, contact
your local. Hewlett-Packard .field office to obtain
· the materials. This-office wlll also furnish the
address, of the nearest.service office to which the
Instrument can bl. shipped. Be sure.'to attach' a
tag to the Instrument which.specifies the owner,
model number, full serial number, and service re-
quired, or a brief description of the trouble.
I,
,

,,
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...
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'
SECTION
Ill
. \ . I I
OPERATING.
INSTRUCTIO~S\
'
'I
'
·\
I,
\
\
·,
,
' '
'
·\
\
,,
,'I
Figure 3~1. Front
Pi>nel
Controls
and Indicators
'
'
3-1
.
TURN-ON
CHECKOUT
PROCEDURE
.
'
.
,
3-2
The following
checkout
procedure
describes
the use·
of
the front
panel
controls and l~dlcator.s
and
ensures
that
the
supply
Is
operatlonal, .
,
a.
Set
UN&
breaker
(1)
tci
ON;
pilot
•lamp
(2)
should
light.
, ·
b. Adjust
VOLTAGE
controls
(3)
until
desired·
output
'voltage
Is
Indicated'on voltmete'r ·(4).
c.
To
ensure
that
constant
current
circuit
Is
.
operational;
tum
off
supply
and
short-circuit
rear
output
t~rmlnals, '
.
d.,
1'um
on
supply
and
adjust
CUP.RENT
con-
trols
(5)
until
desired
output
current Is Indicated
bn
am
metes (6). ' . '
" ·
e.
Remove
short
and
connect load to output,
terminals. '
3-3
OPERATING
MODES
,,
3-4
' The power
supply
Is deijlgned so
that
Its
mode
of
operation
can
be
selected
by making
strapping
conr.actions
between particular terminals
3-1
on
the terminal strip
at
the
rear
of
the
power·sup.:'
ply. The terminal
designations
are
.stenciled
In
white
,n
.the powar supply
above
their
respective
terminals, Although the
strapping
patterns
illustra-
ted
In
this
section
show the
positive
terminal
grounded, the operator
can
ground
either
buss
or
operate'
the power supply up to 600Vdc
of[
,:round '
,(floating). The following
paragraphs
describe
the
procedures for utlllzlng the
various
operational
,
1
capabilities
of the power
supply.
A more
theoret-
ical
description concerning
the
operational
fea-
tures
of
this
supply Is
contained
In Application
Note 90, Power Supply Handbook; a•rallable
at
no
charge
from your
local,Hew\ett-Packard
sales
of-
~lce.
Sales
office
address~s
appear
ot
the rear of
the
111anual.
, .
3-5
NORMAL
OPERATING
MODE
' '
3-6
The power supply
ls
normally
shipped
with ·
.
!ts
rear
terminal strapping
connections
arranged
for
Constant
Voltage/Constant
Current,
local
.sensing, local program.ming,
single
unli'modi:, of
II
I.
,,

,,
I i1 ' , ,
Figure 3-2. Normal Strapping Pattern
' { !
I
I , '·
operation. This strapping pattern Is Illustrated In
Flgure/3-2, The operator selects either a constant
VO [tage or a constant current OUtp'ut using the front
panel controls (local programming, no ~trapping
) ' '
change~ are necessary. ,
'
3-7" CONSTANT VOLTAGE
' I;:
I
! \1
3-8' To select a constant voltage output, r,ro- •.,
ceed as follows: , , , , \,
a. Turn-on power sup;,ly'and adjust'VOLT- \
AGE control for dqslred output voltage (output ter-,,
mlnals open).' , ,' ,
' b,,' Short output.terminals and
adjust CUR-
RENT control for ·maximum output current allowable
(current limit), as determined by load conditions.
If a load change causes the current limit to be ex;.
ceeded, the power supply will automatically cross-
over to constant current output at the preset'current
limit and the output voltage will drop prop'ortlol'\:-
ately. In setting the current limit, allowance must
be made for high peak current.which can cause un-
wanted cross-over., (Refer to Parag,raph 3-41.)
'
3-9 CONSTANT CURRENT
,, '
3-10 To select a constant current output, proceed
as follows:
a,·' Short output terminals and adjust CUR-
RENT control for desired output current.
,,
b, Open output•termlrials and adjust ,VOLT-
AGE controls for maximum output voltage 'allowable
(voltage limit),
as determined by load conditions. ,
If a load change causas the voltage limit to be ex-
ceeded, the power supply will automatically cross-
ever to con'stant voltage output at the preset volt-
age limit and the output current will drop propor-
tlonate,ly, In
setting the voltage limit, allowance
must be· made for high peak vpltages which can ,
cause unwanted crossover. (Refer to Paragraph 3-41.)
3-11 '. CONNECTING LOAD
3-12' Each load should be connected to the power ,
supply output terminals using separate.pairs of
connecting wires, This will minimize mutual cou-
pling 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 re-
,!, •. ·' duce l'lois,e piCkup~ ~f shield ·15 used, connect· ope
I,, : ,, ,' ,/
3-2
end to power supply ground terminal and leave the'
other'end uncpnnect7d.) ' I
3.:13 If load consideration's require that the output
power distribution terminals be
remotely located '
from the power supply,
then the' power suppiy out-
put terminals 'should be connected to the remote
distribution terminals ~·la a pair of twlsted'or ,
shielded wires and·each load separately connected
to the remote distribution terminals. ,For this case,
remote sensing should be used (Paragraph 3-29,) '
~ cl 4 OPERATION OF SUPPLYBEYON D RATED OUTPUT
3-15 ,The shaded area on the front panel meter face
Indicates the amount of output voltage or current
!h<!t Is available In excess of the normal rated out-
, put." Although tha supply cari be operated In this
shaded 're11l011 wlthuut being,damaged, It c'annot be
guaranteed to meet
all of its performance speclflca-
, tlcins. However, if 'the line voltage'ls maintained
above
'llSVac, the supply wiH probably operate
within Its specifications. '
3-16 OPTIONAL OPERATING MODES
3-17 REMOTE PRO;RAMMING, CONSTANT VOLTAGE
3-18 The constant voltage output of the power sup-
,
ply can be programmed (controlled) from a remote
,
location if required, Elther'a resistance or voltage
source
can be used for the programming device, The
wires connecting the programming terminals of tho
supply to the re.note, programming device should be
twisted or shielded,to, reduce noise pickup. , The
VOLTAGE control on the front panel Is dlsf1bled by
,
the following procedures. ,
, Figure 3-3. Remote
Resistance Pr~gramming
3-19 'Resistance Programming (Figure 3-3), In th!~
mode, the output voltage
wlll vary at a rate deter-
mined by the programming coefficient (300 ohms
per Volt), The output voltage wlll increase 1 Volt
for each 300 ohms added in series with the pro-
gramming terminals, The programming coefficient
ls determined by the programming' current. This .

current ls factory adjusted to wlthln 2% ,,r'3. 3,;;A.
If greater programming accuracy ls required, lt'may
be achieved by changing resistor R39 a~ discussed
ln Paragraph 5-70.
3-20 To malntaln 'the stablllty and temperature
coefficient of the power supply, use programming,
resistors that have stable; low noise, and low
temperature (less than 30ppm per degree Ce~tl-:, :,,, , I
grade) characteristics •. A switch can bel us. 'Vn'', \.,!,
conjunction with various resistance values' \tlor,Jo?/
to
obtain discrete output voltages. The ~witch ., " 1
should have make-before-break,contacts
1to avoid
momentarlly
opening the programming terminals
.during the
'switching lnterva I.
Figure 3-4. Remote Voltage Programming
· ·
(Constant Voltage)
3-21 Voltage Programming (Figure 3-4). Employ
the strapping
pattern shown on Figure 3-4 for volt-
age programming.,' lil this mode, the output volt-
age will vary In a 1 to 1 ratio with the programming
voltage (reference voltage)
and the load on the
?rogrammlng
voltage source wlll not exceed 20
mlcroarriperes.
3-22
An Impedance matching resistor of approxi-
mately 1000,,.
should be connected In series with
the voltage
source to maintain the temperature and
stablllty specifications of the power ~upply.
3-23 Methods
of voltage programming with gain
are
discussed In. Application Note 90, Power Sup-
ply Handbook; avallable at no charge from your
local\1 Sales Office.
3-24 REMOTE PROGRAMMING, CONSTANT CURRENT
3-25 Either a resistance or a voltage source can
be used to control the' constant current output of
the supply. , The CURRENT controls on the front
panel are
disabled according to the following pro-'
cedures.
3-26 Resistance Programming (Figure 3-5).· In
this mode,
the output current varies at ·a rate de-
termined by the programming coefflclent (600 ohms/
Ampere)., .The programming ':'oefflclent Is adjusted
' '
r.·i:r.:·r:,,· 'H·il• J:iitt-"ir!~J:.·~-- "'' •.,,-.. ~ r '"'F:tf,"'-f"'~J!:'0.:· ~··•t.'·'· ''•,,
1
·\ "\'>'<'a••~\."' ~/!""""' 'r./rt
1;\~Wi;:~VJ/" ~'\""''!Si' t.t:Ll)t'l{,~)'.tf ,fi~r
1
t~·,~'\(
1
'~;p•,._·(J ·!.''
1
~\1S(t8:i;~
~ .. ,.. ,,,,, ' ' ,,. . ' .,t ' ' ' •, . ,,,,f,,),,
i;:j\j_,\':\;:.•1'.,··._ ' _"·:. '.-~. ~ CZ, ·t.i_;:;;_1_(·,1
' '
I ._, '
":J _' '' \1 , .\ t J
Figure 3°-5. '.t\emote Resistance Programming
' ' \ .. '
/ ,,(Constant Current)
'jf I
:- ·, l
for an ac;curacy of 6% at the factory., If greater
programming accuracy Is required, It may be a-
chieved by ahanglng resistor R41 as outlined, In
Paragraph 5-72. , . ,
I
i '· ' ' ' ' ' '
, ~-27 ,Use stable, low noise, low tP.mperature co-,
efflclenl! (less than 30ppm/°C) programming resis-
tors td malntaln the power supply temperature co-:'
efficient and stabllity speclflcatlons. · A switch /
' ' '
,fllay·',e used to set,dlscr~te values of output cur-
rent •. A make-before~break type of switch should
be used since the output cun;ent wlil exceed the
'maximum rating of the r,bwer supply lf the switch
I ' I '11
1- '
l
contacts open durlng,the swltchlng lntei;val. ./ '
i) i . '1 ','i\' I
I, I'
Ii '· , 1
_...._ __ -CAUTION-----
/1 ;' !'
'
If the programming' terminals (AZ and
A4) should open at any time during I
\,
' I' • 1\
thls mode, the 9utput current wlll rise
to ayalue that may damage the power
supply and/or thc:load. To avoid this;
possibility, connect a 200 ohm ~csls-'
tor across the programming terminals.
LiJ<e the programming resistor, this '
resistor should be of the low noise,
low teinperature coefflclent type,
i
' ' I , , / • ,
3-28 Methods used to voltage program a power
supply with gain are discussed in Appl!cutlon Note
90, Power Supply Handbook;,available'at no charge
from ,your local rEj, Sales Offke. i ·· ·
'
I .
3-29 REMOTE SENSING (See Flgute 3-6)
. ·. . . I . · ..
3-30 Remote sensing ls used to maintain good
regulation at the load and reduce the degradaUon
of regulation which would occur due to the voltage
drop in the leads between the power supply and
,
the load. · Remote sensing ls accomplished by utl-
' llzlng ~he strapping pattern, shown ln:Flgure 3-6::,
The power supply should be turned off before
changing strapping patterns. The leads from the
+S terminals to the load will carry much loss cur-,.·
3-3
'''

Figure 3-6., Remot~ Sensing
~ . ' '
'
' \ \,' '',
rent thnn the load lead~ and' It Is not required that
these leads be 'as' heavy as the load lead!,~., How-'
ever, they must be twisted or shielded to mlrtimlze
noise pickup. '
'· ' ·
'
3-31. Note that it is desirable to minimize the
voltage drop
In the load leads and It Is recommend-
1ed that'the drop not exceed l Vo,lt per,,lead If the '
power supply Is to
meet its de specifications. .If
dlarger droj:, must be tolerated, please consult a
~ sales engineer.. '· 1,
NOTE
'')ue to the voltage drop In the load.
leads, It may be necessary to read-
Justthe current limit In the remote
sensing mode.
I '1
3-32 Although the strapping· patterns shown in
Figures 3-3 through
3-5 employ local sensing,
note that
it Is possible to ope~ate a power supply
simultaneously In
the reinote sensing 'and Constant
Voltage/Constant
Current remote programming
modes. · ·' ,1
',');
;/ .,i I
Figure 3-7. Normal ParaUel Connections
~-33,. PARALLEL OPERATION,
' '
3-34, Normal Parallel Connections (Figure 3-7).
Two or, more p,iwer supplies can be connected In
I ' ,
parallel to obtain a total output current greater,
i " ' '
I '
',
than that available from one power supply. The
totaloutput current Is the sum of the output cur-
rents of the Individual power supplies. The output
CURRENT, controls of each power supply can be
separately set. 'fhe'output voltage controls of
' one power supply should be set to the desired out-
'put voltage; the other power supply should be· 'set',
for a slightly larger output voltage. The supply
set' to the lower output voltage will act as a con-
stant,voltage source; the supply set to the higher
output will act as a constant current source, drop-
'ping Its output voltge until It equa~s that of the '
other supply,, The constant,voltage source will
deliver only that fraction of Its total rated output.,
current ·which Is necessary to fulfill the total cur-
rent demand.
. 1 /
I
,, I
I,,
.·r :·
,· .. ;
·'q·
' .,
' .
;·,·,
Figure 3.:.a. Auto Paralie I, Two and Three Uni ts
I·,
· 3-35 Auto-Parallel. The strapping patterns for
Auto-Parallel operation of three power supplies
are shown In Figure 3-8. Auto-Parallel operation
permits equal current sharing under all load con-
ditions,' and allows complete control of the output
current from one master power supply. The output
current of each,slave will be approximately equal
to the master's regardless of the load conditions.
Because the. output current controls of each slave
are operative, they should be set to maximum to
avoid having the slave revert to constant current
3-4 '

·,
,,
' '
, I ' , I
operation: this woulc! occur if, the master output
current setting exceeded the slave's. ' '
' ,' ' J '
3-36 Additional slave, supplies 'may be, added In
parallel to the Master/Slave combination. All the.
connections between the Master and Slave lll are
duplicated between
Slave 111 and the added Slave'
' ' '
supply, In addition, the strapping pattern of the
.added Sla\/e should be
the same f\S ,Slave lll. ,
,i
,\'.<'
/,( ·.\'
.,.: .. ,•,.!
·.y,
",.·, i,i::,;:':'
., ... , ... :.;
·.,,-'..\ .. ····
Figure 3"".9,, Auto Tracking, Two and Three Units
3-37
AUTO-TRACKING OPERATION (See Figure 3'-9)
. ' . '
3-38' The Auto-Tracking configuration ls used
when It Is
necessary that several different volt-
ages referred to a common buss, vary In p,'Oportfon
to the setting
of a particular Instrument (the con-
trol or master). Afrar,:tlon of the master's output
voltage
ls fed to the comparison amplifier of the'
slave suµply, thu:s controllln\l the slave's output,
'The master must have
the largest output voltage
i of any power supply in the group (must be the ·
most ne,gatlve supply in
the example shown on
Figure 3-9).
3-39 The output voltage of the slave,ls a percent-
age of the master's ouiput voltage, and ls deter:.
mined
by the voltage,divider consisting of Rx and
the,voltage control of the slave supply, Rp, where
Es= EM(Rp/Rx + Rp). Tum-on and tum-off pf the
, power supplies are contrplled by the'ma,ster, Remote
sensing and programming can be used; although th.e
strapping patterns for tne'se modes show only loc'al
sensing and programming. In order to maintain the
temperature coefficient and stability specifications
of the power suppiy, the external resistors should
be stable, low noise, low temperature coefficient
(less than 30ppm per"C) resistors, '
3-40 SPECIAL OPERATING CONSIDERATIONS
3-41 PULSE LOADING
3-42 Tl'ie power supply will automatically cross
'over from constant voltage to constant current op-
eration. or the reverse, ln response to an increase
(over the preset limit) in the' output"current or volt-
age, "."spectlvely. Although the preset limit may
be set higher than the average output current or
voltage, high peak: currents or voltages (as occur
In pulse loading) may exceed the preset limit and
, cause cross,over to occur.' If this crossover llmlt-
lng Is not desired, set the preset limit for the
· peak requirement and not the average.
3-:-43 OUTPUT CAPACITANCE
·3_44 Internal capacitors (Cl5 and Cl6) connected
across the output terminals of the 'power supply,
help to supply high-current pulses 'of short dura"".,
!Ion during constant voltage operation, Any capac-
itance added externally will Improve the pulse cur-
rent capability, but will decrease the safety pro-
vided by the constant current circuit., A high-cur-
rent pulse may damage load components before tho
average output current Is large enough to cause the
constant current circuit to operate.
3-45 The
effects of the putput capacitor during
constant current operation are as follows:
, ,
a, The output Impedance of the power sup-.
'ply decreases with increasing frequency.
b, The recovery time
of the output voltage
Is longer for load resistance changes. ·
c, A large surge current causing a high
power
dissipation In the load occurs whan the load
resistance ls reduced rapidly.
3-46
REVERSE VOLTAGE LOADING
3-47 Diodes are connected across the output ter-
minals. Under normal operating conditions, the
,diodes' are reverse biased (anode connected to
negative terminal). If a reverse voltage Is applied
to the output terminals (positive voltage'DPP,lled to
negative terminal), the diodes will conduct: 'shunt-
3-5
•)
,,
' '

ing
current
across
the
output
terminals
and limiting
the voltage
to
the forward
voltage
drop
of
the ·
,,
diode, ,The diodes
protect
the
series
transistors
and
the outpu't
electrolytic
capacitor.·
i ' '
3-4B
REVERSE
CURRENT
LOApING
3-49
Active loads
connected
to
the
power suppl:,,
may actually deliver a
reverse
current
to the power
'
"
' I
,,
. I
I
'
1)'
3-6
supply
during a portion of·
its
operating
cycle,
An
external
source
cannot
be allowed to pump
current
into
the
supply
without
loss
of
regulation and
pos-.
siblP. damage
to
the
output capacitor,
To
avoid
these
effects',
it
is
necessary
to ,preload
the
sup-
ply
with
a dummy, load
resistor
so that
the
power
'I·
supply
delivers.
current
through the entire
'opera-
tion·cycle
of
the
load device,
'
'
'
'

' '
4-1
. \1' , I
' '
SECTION IV
PRINCIPLES. OF' OPERATION
,'
Flgu're 4-1.
' Overall
Block Diagram
' '
OVERALL DESCRIPTION ,(See Flaure 4-ll
. '[ ' ,·' ' ., ,1 '
,,
4-2 The maln power transform~r Tl Isolates the
ac Input from the power supply and Increases lt to
'4-3 The SCR reg~lators are con!rolled by the SCR
regulator
contra I circuit which operates In response
,to signals developed by the voltage or current,com-
parlson cl~cult, A gating circuit assures tha,t only
, . I . . .
. the voltage level required, , Rectification and fil-
tering produces a smoothed·dc output/across the
-
and + terminals. Alarge capa~lfoi'!s connected
across the :. and+ terminals for low ac output Im-
pedance and to help supply large,puls1{'currents,
SCR regulators control the ac Input to provide good
one Input
circuit is used at a time·,,· ,,
' ' ' ' •, ' I '
4-4 The voltage and current comparison circuits
operate In a similar manner,, Each clrc\ilt has an
amplifier' that amplifies an error voltage that Is
proportl~naI to the difference between the actua I
output
and the programmed output. The program-·
med output Is determined by the resistance of the
programming resistors (voltage and current ~on- '
tiols).
', Each progr.immlng resistor has n c~nstant
', . · ' • I· I ,
rogulatlon of the de output, Transformer T2 powers
the SCR regulator,control clrculi dnd 'the bias and'
reference
circuit \'/hlch' produces de bias 'and refer-
. I ' I'
ence voltages for the power supply.
1 • , ', , , '
' ' ,I '
/ I
1'
'
,,
___ -------1'.:.~--
,4-1
"
"

I ,'
"
I
/
'//
I',
,,,·
,I,'
c~rrent through it which is, ~aintained by the' bi~s
ii
',',' I
·and refer,ence circuit.· j , , 1
,4~5 The voltage'comparison amplifier QI detects'
' the error voltage, that is proport'ional to the differ~
ence between the \roltage across its programming
resls\pr 'R~ and :,+0,7 Volts'bn ,'the emitter. The erro~
voltage is',amplified and'passed throug!J the gating
,
circuit to the SCR regulator control which triggers
the SCR regulator. The S,CR' regulator inc;reases or
decreases the ac Input voltage to the main power
transformer
as required to maintain a constant loa'd
voltay'e that is equal to the programm~d value. In
constant voltage 6i,eratlon, the gatlng circuit is .
biased to inhibit the input from the current comparl"
son circuit.
,. I. ', 1 , :, '
4-6 'The current comparison ampl.lfier detects the
error voitage that Is
proportional to the difference'
between' the voltage
across its programming rests- '
tor
RQ and the voltage across current monitoring
resistor RS3. The voltage across R53 is propor-
tlonal to the load curre~t. The ,SCR regulator r1>-,
spends to the amplified error voltage by increasing
or decr~aslng the ac input current to the nialn power
transfdrmers
as 'required to maintain a constant
load current, In constant current operatlon, the
,gatlng circuit is' bia.sed to
inhibit the input from the
voltage input circuit, ,
I ' II
4-7 '!wo in~ut amplifiers are' included in, a CV/CC
supply, 'one for controlling
output voltage, the'
other for controlling output current, Since the con-
stant voltage amplifier tends to achieve zero output ,'
I '
impedance and alters the output current whenever
the load resistan,;e
changes, ,,while the.constant
current comparison
amplifier causes the output Im-
pedance to be infinite
and changes the ,output, volt-
age in response to' any load resistance change, it
is obvious that t'he two comparison
1amplifiers
can-
not operate simultaneously. For any g\ven value
of load resistance, the power supply must act
either as aconstant voltage source or as a con-
I I slant current source-it cannot' be both; transfer
between
these two modes,is ac:complished at a
value of load resistance equal to the ratio of the
output voltage control settlng to the output current
con,trol settlng.
4-8 Figure 4-2 shows the output characteristlc
of a CV/CC power supply. With no load attached
(RL=.,), loUT =0, and
E:QUT = E:s, the front
,
panel voltage control settlng; When a loail,re-
sistance ,is applied to the output terminals of the
power supply, the
output current Increases, while
the output voltage remains
constant; point D thus
'represents a typical constant voltage operating '
point, Further
decreases in load resistpnce are
ac~ompanled by further increases in louT with no
change iri 'the output voltage until the output cur-
rent reaches lg, a value equal to the front panel
,,
''
.. ··:.·.·it,.
PtN" ClRCUtt to,\D CONSTANT VOtT.AOE
'i · D OPWnNG RECtON
C
,,
cilnSTANT cuRRENT
OPERATING RtCtON ,
,, '
' ·l
,·(, EoUT
Jou..-:--- .
ts,
"'t. ! .1' ' .
'.'·is,_ f'Ro,:r PANEL VOLTAGE CONTROL 6En'ING :
,· ·. ls• f'R:ONT PANEt.qtJMENT-CO~_<?L ~NC.
,i; · ,.>' Rc•!a.• •cRll'tc.u.·oR,·c1tos:.ovER·'
· ,,,,. , ls. VALUEOFLOADRtBlSTANCt..
'1.>. , ' ·,,' i).
,
,,
'
''
Figure 4-2. Operating Locus of a CV/CC
Power Supply
,, '
current control settlng. At this point th.e supply
automatically changes its mode of operation and
becomes.a constant current source; stlll further
decreases in the value,of load resistance are ac-
companied by a drop ln•the supply output voltage
with no accompanying' char.ge In the output curre'nt
value, Thus, point Brepresents a typical constant
current operatlng point. Stlll further decreases In
the load resistance result In output voltage de-
creases with 110 ,change In ,butnut current, ,until
finally, with a short circuit across the output load
terminals,, IouT = Is and EoUT = o. ,
I ,
4-9A By gradually chtinging the load resistance
from a short circuit to an open circuit the operating
locus of Figure 4-2 _:,Ill be traversed In the opposite
,direction.' , ,
4-98 Full
protectlon against any overload condi-
, 'tion,l,s lnhererit In the.Constant Volt,age/Constant
Current
design principle since no,lo.:d conditlon
can cause an output which lies outside the oper-
'' '
,ating locus of Figure 4-2. Whether one is prima-
rily concerneil with constant voltage or constant
current operatlon,' the .proper choice of E:s and Is,
insures optlmum protection for the load device as
well as full protection for the power supply Itself,
, ~I .
~-10 The line connecting the origin with any oper-
ating point of tlje locus of, Figure 4-2 has a slope
which• is proportional to the value of load resist-
ance connected to the 0lltput terminals of the sup-
ply.' One can define a
11
crltical
11
or
11
crossover
11
value of load resistance Re'= Eg/lg; i,djustmen.t of
the fro'nt pane 1 voltage and current controIs permits
thls ,
11
crossover
11
reslstance Re to ,be set to any
desired value from Oto.,_ , If RL Is greater than'
4-2

Re;,,
the
supply Is
In
constant
voltage
operation,
whlle
If
RL
ls
le.ss than
Re,
the
supply
Is
in
con.:.
stant
current
operation.
4-11
The Short.,.Clrcult Protection
circuit,
Q2,
monitors
the
positive
(+)
output
of
the
supply
and
prevents
any
damage to the
sui,ply
when
the
'output
terminals
are shorted. The
Overvoltage
Protection
circuit,,
Q3, monitors the
positive'(+)
output
of
the
power
supply.
Its
output
ls
fed
to
the
SCR Regu-
lator
Control
circuit
to
establish
an
output
voltage
celling
that
wlll not
be
exceede'd,
even
If
the
VOLTAGE
contJ:ol becomes
open-circuited.
4-12
DETAILED
CIRCUIT
ANALYSIS
(Refer
tD
Fi1ure
7-3,
S~hemaUc
Diapam.)
4-13
AC
INPUT
'
4-"14 The standard
ac
input
voltage
ls
ll
5Vac
±
10%,
,,
57-63Hz;
208 and 230Vac
input
are
optional
as
dis-
cussed
in
Section
I.
The
standard
input
frequency
ls
57-63Hz; 50l!z input
ls
optional
and' requires
circuit
adjustments
as
described
ln
Section
V.
The
ac
input
ls
applled to transformer
T2
and
to the
series
combination of tranaformer Tl and
SCR
1
s
CR17 and
CRIB
which are
in
parallel
opposition.
The
SCR'
s
are
used
to
regulate
the
de
output
by
controlling
the average
value
'of
the
ac
input
to
transformer
Tl.
LC
network L2, C9,
Clo,
and
Cl!
ls
an
RF!
filter that inhibits
noise
spikes
generated
by
the
SCR's
from
the
ac
Input
line.
Capacitors
C7 ' ,
and
Cl2
smooth transients
to
prevent
the
SCR•
s
from being triggered
by
a
rapidly
changing
voltage
from anode to cathode,
Resistor
R21
damps
oscll-
latlons
that
may
occur due
to.
resonance'of
Cl2
and
the
leakage
inductance of
Tl.
The
leakage
Induct-
,
ance
of
Tl
limits the peak
input
current.
'
4-15
DC
OUTPUT
4-16
The output of the
secondary
of
transformer
Tl
ls
full-wave rectified
by
CR20
and
CR21
and
filter-
ed
by
pl-section
fllterC13,
Cl4,
LI,
ClS,
and
Cl0
and'
R29. 'The
de
output
ls
regulated
to
a
constant
'value
by the
SCR'
s
CR
17
and CRIB.
Capacitors
C
15
and
Cl
7
are the output
capacitors.
Diodes
CR21
and
CR22
are connected
across
the
filtered
de
out-'
put
to
protect
the
power
supply
from
reverse
volt-
age
applled to'the output
terminals.
Resistor
R53
ls
the
current monitoring
resistor;
the
full load current
fiows through
it.
Potentiometers
R25
and
R27
are
used
to calibrate the'voltmeter and ammeter,
re-
spectively.
'
4-17
FEEDBACK
LOOP
4-1.B
Th~
voltage and current
feedback
loops
QI,
Q4,
Q7,
QB
and
CR17
and
18
function
continuously
to
keep
the output voltage
constant
during
constant
'
voltage
operation, and
the
output
current
constant
during constant current
operation.
For
purposes
of
this
discussion,
assume
that
the
unit
ls
in
constant
voltage
operation and ~hat
the
VOLTAGE'
control
4-3
programming
resistor
R2
has
been adjusted
so
that
the supply
Is
yielding
the
desired
output voltage:
Further
assume:
that
the
output voltage
Instantane-
ously
rises
(goes posltllre) due to a variation In
the
external
load
circuit.
4-19 Note
that
the
change
may
be in the form.of a
slow
rise
in
th!"
'output voltage or a
posltive'golng,
ac
signal.
An
ac
signal
ls
coupled to QI through
capacitor
Cl
and a
de
voltage
ls
coupled to
QI
'
through R2. '
4-20 The
rise
in
output
voltage
causes
the
voltage
at
the
base
of
Ql
to
increase
(go
positive).
QI
now
decreases
Its
conJuction
and
its
collector
voltage r.lses
negatively.
The negative going error
voltage
ls
amplified
and
inverted
by
Q4
and fed to
the
SCR
Regulator
Controi
clrcult,
which
decreases
the conduction
of
SCR regulators
CR17
anci
CRlB.
This lowers
the
AC
voltage
to transformer
Tl,
de-
creasing
the
rectified
output
voltage
a'
sufficient
amou~\ to
offset
the
error.
'
4-21
If
the
external
load
resistance
Is
decre~sed
to a
certain
crossover
point
as
discussed. in
Para-
graph
4-8
the
output
currant
Increases until
tran-
sistor
QB
begins
to
conduct.
During this time,
the output
voltage
has
also
,decreased to a
level
so
that
the
base
of
Ql
Is
at
a negative potentla l,
' '
4-22
VOLTAGE
COMPARISON
AMPLIFIER
'
'
4-23 This
circuit
consists
of
programmlng
resistor
R2
and
ampllfler
stage
Ql,'
and
associated
com,-
ponents. The
voltage
comparison amplifier con.:.
tlnuously
compares
a
fixed reference voltage
with
a portion
of
the
output
VOitage
Md,
If
a
difference
exists,
produces
an
error
voltage whose amplitude
and pl\ase
Is
proportional to the difference. · The
error
output
ls
fed
back
to,the
SCR
Regulator
Con-
trol
circuit
through
an
OR
gate, ''The error
voltage
changes
the
conduction
of
the
SCR
regu'lators
which, In
tum,
alterthe
output voltage so
that
the difference
between
the
two Input voltages
ap-
plled to the
comparison
ampllfler ls'reduced'to
zero, The
above
action
maintains the output
volt-
age constant~
r
4-24 The
emitter
of
Ql
1.s
connected to
.a
stable
, +0.
7V.
The
base
of
Ql
Is connected to a summing
point
at
the
junction
of
the programming
roslstor
R2
and R42.
Instantaneous
changes
In
output
voltage result' In
an
lncreas·e or
decrease
In
the
summing
point
potential.
QI
Is then made to
con-
duct more
or
less·
In
accordance
with the summing
point
voltage
change.
The resultant output error
voltage Is
f!"d
back
to the
series
regulator
via
OR-
9/lte diode
CR7
and
the
remaining components
of
the
feedback
loop.
Resistor
RI
In
series
with the
base
o[Ql,
limits
the
current through the program-
ming
resistor
during
rapid
voltage turn down. "
Diode CRl
is
a
limiter
that
prevents
excessive
voltage
excursions
from over-driving stage
Ql.
·
Capacitor
Cl
shnntlng
thepiogrammlng rcslstor'HZ,
i

•
Increasing the high frequency galn of the amplifier
Ql. RC 'network C4, Rl3, and Rl4 Introduce neg-
~tl ve feedbacii< In Ql to eliminate 'oscillation.
Rl3 Is select~d to eliminate ringing and minimize
overshoe,! for load transient recovery time, dis:-'
cusse1, ~n Paragraph 5-73.
'
4-25 CURRENT COMPARISON AMPLIFIER
,/ I
'
4-26 Thls circuit Is similar In appearance and
., operation to 'the voltage comparison amplifier. It
'consists basically of current programming resistor
.R9, current sampling resistor R53, and stage QB.
4-27 The current ~omparlson'ampllfier continu-
ously monitors the voltage r,lrop across currez;it
sampling resistor R53. When a preset voltage I~ ,
exceeded,' the amplifier produces·an error voltage,
,
which fo!"~arl biases CRB. The remaining stages
1
In the fe,;,dback loop function to maintain the drop .
across "!.he current sampllng resistor and',. 'iconse~
quent:f, the output current at a constant value.
RC- network R47'and C23 provide negative feedback
to stab'lllze the current comparison nmi:,llfler and
the feedback loop.
4-28 GATING CIRCUIT
4-29 Transistor, Q3 draws current from the SCR
regulator control circuit (capacitor C25). The mag-
nitude of this current ls determined by either the
'voltage or current' comparison amplifier. For con-
stant wltage·operatlon, dlode CR7 Is forward
biased to permit the voltage circuit to drive Q4;
diode CRB ls reverse biased to Inhibit the Input
from
the curr~nt Input circuit. For constant current
operation.,the re~rse occurs ..
,). '
4-30 To prevent transients In the de output wl]en
the power supply ls turned-on, the tum-on of Q4
ls delayed by capacitor C24 which charges through
. R57
and CR15. When C24 charges sufficiently to
,
,reverse blas CRIS, all the current through R57
., flows to the collector of Q4 to tum It on. Base
current ls controlled by the vo'ttage or current cir-
cults 'via CR7 or CRB, respectively. .For example,
during 'constant voltage operation the collector
voltage of QI (voltage lnput) forward b,lases CR7'
(CRB reverse biased by QB), the current through
CR7
will vary as QI collector voltage varies and
thus vary Q4 base current; therefore, the·collector
current of Q4 ls controlled by the voltage Input.
In a similar manner, the current Input circuit con-
trols the collector current of Q4 during constant·
current operation.
4-:iI SCR REGU!ATOR CONTROL (Refer to Figure
4-3, SCR Control Timing Diagram.)
4-3'2 The SCR regulator control lR basically a
blocking oscillator (Q7 and T3) that applies pulses·
4-4
Flg•1re 4~3. SCR Regulator Control, Timing Diagram
' '
to the SCR regulator In response to error signals
detected by the voltage or current comparison cir-
cuit. When transistor Q7 conducts, i~e pulse
developed In winding 1-2 of transformer T3 ls. . .
coupled to the base of Q7 (positive feedback) and . ',
, and to the SCR regulator (CR17 and CRIB). Capac-
itor C27 charges In opposition to the feedback
voltage
and cuts off Q7 •. The charge time of C27
determines
the pulse duration In the collector of,
Q7 (approximately 20 microseconds). The 32Vdc
bias supplies current thro~gh R52, CR46, and CR44
to
discharge C27 after Qi stops conducting.
4-33
Gate Input. Throughout the 'operation of the
blc,cklng
oscillator, capacitor C25 supplies most
of the collector current for Q4 In the gating circuit'
(refer to Paragraph 4-30). The amount of current
pulled from C25 by,Q4 Is determfned by the Input
(from the voltage or current comparison clrcult)'to
the gating circuit. As a result of.this current flow
from'C25,
the voltage across C25 increases neg-
atively with respect to the +O. 7V bias and has a
waveshape that approximates a linear ramp. Thus,
the slope of this ramp Is determined by the volt-
'
,,

age or current comparison circuit. Due to the
time delay in the feedback loop,· the slope 'or the
ramp is constant•for a half cycle of .the ac·,lnput.
' ' • ., I
The voltage on C25 Is the emitter bias \.c;"'•ard
bias when negative) for Q7 arid therefore nelps
determine the point'at which Q7 conducts.
'
. ' '
4-34 AC Input. The ac Input to transformer T2 Is
stepped-down and ful!-wave rectified by bridge
rectifier CR39 through CR43. The output of the
bridge rectifier Is a negative-going puleatlng de
(120Hz). ·. Voltage•dlvlder RS0-RSl supplies a por-
tion of this pulsating de tlirough C27 to the base
of Q7; thus, the. base is reverse biased. i,
4-35 Firing. A point is reached during each cycle ·
of the 120Hz pulsating de when the reverse blas on
the base and the forward blas (capacitor C25) on
the emitte'r of Q7 are equal, and therefore Q7 has
zero bias. As the ra~p voltage across C25 goes
more negative th~n the base voltage, 'the base-
emitter Junction of Q7 begins to become forwf!rd
biased. When.·the emitter is more negative than
the base by approximately 0. 5 Volts. Q7 conducts •.
The firing point of Q7 is therefore determined by
both the de output error and the line voltage
change. Because Q7 saturates when it conducts,
the collei:tor voltage approximates a.rectangular
wave with a negative going pulse width of approx-
imately 20 microseconds (determined by C27 and
RS l). The conduction of Q7 charges C25 In the
positive direction (clamped by CR49)., When Q7
stops conducting, ihe ramp across C25 begins
again". However, Q7 Is held cut-off by the charge
on C27.
4-36 Reset •. At the beginning of each cycle of
the 120Hz pulsating de, certain initial conditions
must be established on capacitors C25 and C27.
When the negative-goln11 pulsating de is at the
end of its cycle, at lts'most positive voltage,
CR44 and CR45 become forward biased and current
flows·from the 32Vdc blas through R52, CR46, and
CR44 to discharge C27 to approximately ze'ro Volts
and through R52 and CR45 to charge C25 to approx-
imately -0. 7, Volts (clamped by CR49). This dis-
charge end charge occurs rapidly, so that it Is
completed before the next eye!~ begins and Q7 can
conduct again. Diode CR47 provides another path ,
for the current through CR44 so that the voltage to
which 'c27 discharges remains predictable. A~ the,
negative-going pulsating de lncreases'ln the next
cycle, .CR44 and CMS become reverse biased.
4-37 Bridge Rectifier.' At th~ zero cross-over
region of the voltage w,,vefor.n on secondary wind-,
Ing 3-4' of transformer n, ·. the voltage Is lnsuffl-
clent to forward bias the rectlflers ln the bridge.
In order to maintain definltlon between the end of
one cvcle of the rectified output 11,1d tt,a beginning
. , of the.next cyc:le, diode CR41 provfdes anproxl..:
mately o. 7 Volts at the rectlfled outpui. The cur-
rent for CR41 Is supplll'd through CR46. As the
··voltage across the' secondary winding moves away
· from the zero cross-over region, CR41 becomes '
reverse biased. ·
4-38° Transients, De0 coupllnq and Prote0 ~tlon.
Transients ln the pulsating de are reduced by RSG
and C28. The base of Q7 Is decoupled by'C3.
The voltage' spike In' the i:ollector'of Q7, Induced
by secondary winding 1.-2 of transformer T3 when
,Q7 cuts-off, Is clamped by CR48. The collector
ls dP..coupled by RS 3 and C26. TSl Is a tempera-
ture sensitive switch mounted on the heat sink foe'
CR!7 and CRIB. If the' heat sink becomes too hot,
because' the fan Is not operating, TSI opens, :Q7
shuts off, <!nd .the outp':'t voltage drcps to zero.
4-39 SCR REGULATOR
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'4-40. The SCR regulator (CR17 and CRIB) controls
the ac Input voltage and current to,maln power ,
transformer Tl In response to the voltage and cur-
rent error slgna:s. In constant voltage operation,
the·ac Input voltage,'to Tl Is adjusted so tha~ the
.output voltage remains co'nstant with changing
'toads. In con.stant cu'rrent operation, the ac input
current to '1'1 Is adjusted so that the output current
remains constant with changing loads and the out-
,put voltage Is allowed to vary.
1' '
4-41 Gating. 'Each half cycle of the ac input,
either CRI7 or'CRlB Is forward biased. The pul,se
induced In sei-ondary windings 5-6 and ,7-8 of T3
'by the SCR co~t~t', turns.on the SCR that Is for-
ward biased when the pµlse occurs.' The other
SCR Is not affe!'ted by the gate pul,se because lt Is
reverse biased. A gate pulse occurs each half
cycle of. th,e a'c trjput, unless the output Is open.
The timing of the.gate pulse with respect to the ac
lnpu~ Is determined by the error In the de output
via the loop action. . '
\-42 A~ In ut ~lntrol. · When an SCR I; gated'on,
!!conducts until Its anode-to-cathode voltage
goes to approximately zero. Thus, the earlier an
SCR Is gated on/ the greater the portion of the ac
Input that will 9e applied to TI •. Because of the
leakage lnduct')nce of Tl, the conduction of an
SCR may extend lnto th<t next half cycle. The
· conduction period may be shortened at high output
by the voltage across capacitor CI3 through Cl 6
being reflected back Into the primary, By con-
trolllng the ac h1put to Tl each half cycle, the
average value of the voltage or current at the out-
put of rectifier CR19 and CR20 Is adjusted so that
de output voltage or current Is malntalned,,constant,
4-5

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4-43 Protection, Diodes CR5Cl and CRSl prevent
anode Induced reverse gate currents from being
f«d back to the control circuit, Resistors R54 and
~55 limit current In the SCR gates. '
4..:44 BIAS AND REFERENCE CIRCUIT
4-45 The bias and reference circuit supplies four
voltages (+33, +o. 7,' -10 and -30V) for Internal
power supply operation, and maintains the pro-
gramming currents constant, The -28 and -l0V
outputs are regulated,
4;.45 The
output of secondary winding 5-6 of
transformer T2 ls full-wave rectified by CR30 and
CR31. Capacitors C20.and C,21 each charge to
the' peak rectlfled voltage (voltage doubling), The:
0. 7Vdc (with
respect to -S) ls maintained by diode
CR14. The
+33Vdc ls the voltage across C21. The
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4-6
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-33V across C20. provides the unregulated Input to
the regulator,
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4-47, For the -30Vdc:, Jranslstor Ql0 ls the erro'r
detector/amplifier, Zener diode V~l and diode :
CR6 provide ll''ref1rence' voltage,at the emitter of
010. Voltage dlv,der R35-R36 supplies an error
voltage to the
base of Ql0 which amplifies and
applies lt'to the base of series regulator Qll, The,,,
base drive of Qll'adJ.ists the voltage a,cro,s Qll
as required to compensate for the error In' the -30V.
Resistor
R37., sets the optimum current through tem-
peraturo'-compersated
zener diode VRl, Resistor
R33 reduces power dissipation In .Qll and capacitor
C22 stabilizes the loop. T.he -30V,ls divided down
to
-l0V by stage Q5. Th~ conduction of Q5 Is
h'eld
constant by VRl on the base Gnd R39 Is oe-,
lecte.d to provide exactly,-l0V output,
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