Astec_Power_Supplies_Aug82 Astec Power Supplies Aug82

Astec_Power_Supplies_Aug82 Astec_Power_Supplies_Aug82

User Manual: Astec_Power_Supplies_Aug82

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-APPLE

PRODUCTS

-ASTEC

INFORMATION

POWER

PKG.

SUPPLIES--

ORIGINATOR: Larry Sovulewski
DATE: 6-Aug-82

computczr Inc.

POWER SUPPLY SCHEMATICS AND COMPONENT LAYOITS

--------------------------------------------Apple J L -Astec AAl1040
..........................
Astec AAI1040/B ...........•...•..•..•....

1
3

Apple 1// -Astec AAl1190

...............•..........

5

Profile //1 -Astec AAlI770
Astec AA117701 A
As tec AAll771

.....•.....•.....•...•....
...................
.......
•..........•••.•.••..•.•..

7
9
10

POWER SUPPLY COMPONENT LISTINGS

------------------------------Apple J L -As tec AAl1040
..••.•.......•...•........
Astec AAI1040/B ••.....•..••.......•......

12
14

Apple 1// -Astec AAl1190

....................•.....

17

Profile 1// -Astec AAll770
Astec AAll770/ A
Astec AAII771

.......•..•.......••....••
...•...••.......•.........
.•........................

21
25
26

Astec - Apple Part g Cross Reference ••••••••••

32

POWER SUPPLY INFORMATION

------------------------

Astec "Notes On Power Supplies" •••••••••••••••

34

"Switching Power Supplies" ......................

56

-i-

computc!r Inc.

PLEASE NOTE
ASTEC Services, Ltd. may provide a suitable replacement with
a different part number, depending on vendor availability. Also,
not all ASTEC component parts are available from Apple Computer
at this time. As of this release, we are in the process of obtaining piece part listings and costs to be entered onto the MIS
Corporate system. When this has been done, all Service Sites will
receive updated parts cross-reference listings and additional
parts ordering information. The present cross-reference listing
included in this package lists about 40% of the parts by Apple
Part Number.

ii

computc!r Inc.

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PROFILE III

'ABTEC #AA11771

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........I

-12-

ASTEC 11040 STANDARD POWER SUPPLY
LOCATION

DESCRIPTION

VENDOR NO.

C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
Cll
C12
C13
C14
C15
C16
C17
C18

POLYESTER CAPACITOR 0.1 UP 400V
ELECTROLYTIC CAPACITOR 47 UP 250V
ELECTROYLTIC CAPACITOR 47 OF 250V
ELECTROYLTIC CAPACITOR 47 OF 250V
ELECTROYLTIC CAPACITOR 47 UP 250V
TANTALUM CAPACITOR 22 UP l6V
CERAMIC CAPACITOR 1000 PF 3KV
CERAMIC CAPACITOR 0.01 UP lKV
ELECTROYLITIC CAPACITOR 1000 UP 10V
ELECTROYLITIC CAPACITOR 1000 UP 10V
ELECTROYLITIC CAPACITOR 330 UP 16V
ELECTROYLITIC CAPACITOR 220 UP 10V
ELECTROYLITIC CAPACITOR 1000 UP 10V
POLYESTER CAPACITOR 1000 PF 50V
ELECTROYLITIC CAPACITOR 1000 OF 10V
ELECTROYLITIC CAPACITOR 220 UP 10V
ELECTROYLITIC CAPACITOR 680 UP l6V
ELECTROYLITIC CAPACITOR 330 UP 16V

058-10400100
057-47020040
057-47020040
057-47020040
057-47020040
072-22600040
055-10210001
055-10367325
057-10220020
057-10220020
057-33120080
057-22120060
057-10220020
058-10200020
057-10220020
057-22120060
057-68120010
057-33120080

D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11

RECTIFIER RPC10M
SILICON DIODE IN4150
RECTIFIER RGP10M
RECTIFIER/BEATSINK ASSEMBLY
RECTIFIER/REATSINK ASSEMBLY
RECTIFIER/HEATS INK ASSEMBLY
RECTIFIER RGP15B
RECTIFIER RGP10B
SILICON DIODE 1N4150
SILICON DIODE 1N4150

226-10400050
212-10700050
226-10400100
853-00200020
853-00200020
853-00200020
226-10100040
226-10400070
212-10700050
212-10700050

BLANK

DBl

BRIDGE RECTIFIER KRPI0

226-30500010

Fl

FUSE 2.75

AMP

084-00200040

L1

CONTROL CHOKE COIL
FILTER CHOKE COIL ASSEMBLY
FILTER CHOKE COIL ASSEMBLY
FILTER CHOKE COIL ASSEMBLY
FILTER CHOKE COIL ASSEMBLY

L2
L3
L4
L5

Q1
Q2

250 VOLTS

Q3
Q4

TRANSISTOR
TRANSISTOR
TRANSISTOR
TRANSISTOR

NPN PE8050
NPN 2SC1358
NPN PE8050
PNP PE8550

R1
R2

THERMISTER 4R @25 DEC.CEN +-10%
RESISTOR CARBON FILM 2.2M +-5%

328-00150016
TF-20100010
TF-20100050
TF-20100010
·TF-~0100020

209-11700382
209-10200020
209-11700382
210-11700322
258-40970015
240-22506033

computar Inc.
~------------------------------~---------------------------------~~

-13-

COMPONENT LISTING - ASTEC AAII040
R3
R4
R5
R6
R7
R8
R9
RIO
R11
R12
R13
R14
R15
R16
R17
RI8
R19
R20
R21
R22
R23
R24

RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
BLANK
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR
RESISTOR

CARBON FILM 2.2M +-5%
CARBON FILM 82R +-5%
METAL OXIDE FILM 27R
CARBON FILM 4.7R +-5%
CARBON FILM lOR +-5%
METAL FILM 0.33R +-5%
CARBON FILM 180R +-5%
CARBON FILM 12R +-5%
CARBON FILM 470R +-5%
CARBON FILM 1K +-5%

240-22506033
240-82006033
248-27006052
240-47906033
240-10006022
247-03386054
240-18106022
240-12006022
240-47106022
240-10206022

CARBON
CARBON
CARBON
CARBON
CARBON
CARBON
CARBON

lK +-5%
330R +-5%
5.6K +-5%
27R +-5%
82R +-5%
lK +-5%
2.7K +-5%

240-10206022
240-33106022
240-56206022
240-27006022
240-82006033
240-10206022
240-27206022

RESISTOR CARBON FILM 100R +-5%
RESISTOR CARBON FILM 100R +-5%
RESISTOR CARBON FILM 390R +-5%

240-10106033
240-10106033
240-39106022

SCI

SILICON CONTROL RECTIFIER 2P 05M

227-12500010

T1
T2
T3

POWER TRANSFORMER ASSEMBLY
CONTROL TRANSFORMER ASSEMBLY
COMMON HODE TRANSFORMER ASSEMBLY

TF-10200370
TF-10200200
TF-20200010

Zl
Z2

ZENER DIODE 12.2V +-O.2V
ZENER DIODE 6.8V +-0.2V

222-12295001
222-06895003

VDR1

VARISTOR 260VAC

256-26100014

PCB

PRINTED CIRCUIT BOARD (NO PART'S)

042-02012202

CASE
CASE
CASE

SWITCH (ROCKER TYPE)
AC IKPUT SOCKET (THREE PRONG GROUND)
VOLTAGE SELECTION SWITCH 115/230

278-01200020
149-00200010
283-02200100

(CASE)
(CASE)

BOTTOM PLATE 1.6 AL SHEET
COVER (TOP) 1.6 AL SHEET

403-03100700
403-03100810

FILM
FILM
FILM
FILM
FILM
FILM
FILM

BLANK

,-.-..~ computar Inc.

-14-

ASTEC POWER SUPPLY AAll040B
LOCATION

DESCRIPTION

VENDOB. 110.

Cl
C3
C4
C5
C6
C7
C8
C9
C10
Cll
C12
C13
C14
CI5
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25

MP CAP 0.1 OF +-20% 250 VAC
CER CAP 2200 PF +-20% 400 VAC
CER CAP 2200 PF +-20% 400 VAC
!LEC CAP 47 OF +100-10% 2S0V
!LEC CAP 47 OF +100-10% 250V
!LEC CAP 220 OF +50 -10% 10V
CER CAP 47 PF +-20% 3KV 250
CER CAP 0.01 OF +-20% lKV 25U
CER CAP 0.01 OF +-20% lKV 2SV
POLY CAP 0.22 OF +-10% 100V
!LEC CAP 1000 OF +100 -10% 10V
!LEC CAP 1000 OF +100 -10% 10V
ELEC CAP 1000 OF +100 -10% 10V
ELEC CAP 220 OF +100 -10% 10V
!LEC CAP 220 OF +100 -10% 10V
POLY CAP 0.022 OF +-20% 100V
POLY CAP 0.22 OF +-10% 100V
!LEC CAP 1000 OF +100 -10% 10V
ELEC CAP 580 OF +100 -10% 16V
!LEC CAP 330 OF +100 -10% 16V
£LEC CAP 330 OF +100 -10% 16V
CER CAP 0.01 OF +-20% lKV 2SU
ELEC CAP 47 OF +100 -10% 250V
!LEC CAP 47 OF +10 -10% 250V

068-1'80010
055-2DOOOI0
055-2D20001
057-411;0040
057-4_0040
057"'2:Dl0080
055-457728
055-1IIJ58925
055-Im58925
058-2MEl0120
057-111120020
057-lJII20020
057-1_0020
057-2m0060
057-m20060
058-2D80080
058-2E0120
057-111120020
057-6820010
057-D'l10080
057-lB20080
055-1t368925
057-4_0040
057-4_0040

D1
D2
D3
D4
D5
D6
D7
D8
D9
DI0
Dll
012

RECTIFIER RPG10A
RECTIFIER RPGIOM
RECTIFIER RPGIOM
SILICON DIODE IN4606
SILICON DIODE IN4606
RECTIFIER ASSY
RECTIFIER ASSY
RECTIFIER ASSY
RECTIFIER RGPASB
RECTI FER RGP158
SILICON DIODE IN4606
RECTIIER RGP1S8

226-1Il00050
225-ta00100
226-1MOOI00
2l2-lII00210
212-18100210
853-E

DESCRIPTION

PART NO.

R28

Power transformer ass'y

852-10201210

T2

Control transformer ass,y

852-10200680

SCRl

SCR C122U

227-13000010

VDRI

VDR 260VAC

256-26100014

"Tl

liP connector

Locking header 2cct

146-00200490

OIP Connector

Locking header 12cct

146-00200500

computczr Inc.

-25-

COMPONENT LISTING - ASTEC AAl1770A
DESCRIPTION

PART NUMBER

CI

Cap Poly 0.22uF 100Y

058-22400120

C2

Cap Ceramic O.OluF 100Y

055-10382125

C3

Cap Tant 10uF 25Y

072-10600070

C4

Cap Tant 10uF 25Y

072-10600070

Dl

Diode IN4606

212-107002'10

D2

Diode IN4606

212-10700210

D3

Diode IN4606

212-10700210

Rl

Resistor CF 12K 5~

R2

Resistor CF 2.7K 510

R3

Resistor CF 100R 5%

240-10106022

R4

Resistor CF

240-47106022

RS

Resistor CF

R6

Resistor CF

R7

Resistor CF

R8

Resistor CF

R9

Resistor CF

RIO

Resistor CF

Rll

Resistor CF

R12

Resistor CF 47R 5,%

240-47006022

R13

Resistor CF 2.2K

240-22206022

R14

Resistor CF 470K 5,%

R15

Resistor CF lOOK 5%

Ql

2SB561C

210-11700353

Q2

2SD467C

209-11700463

Q3

2SD467C

209-11700463

Q4

2SD467C

20~-1l700463

QI01

TL43lCLP

211-10800100

CODE

iw

;W

iw
470R 5% iw
lOOK 5% iw
lOOK 5% iw
10K 5~ iw
lOOK 5% ;w
lOOK 5% ;w
lOOK 5% iw
47R 5% ;w

;W
5% ;W
iw
iw

240-12306022
240-27206022

240-10406022
240-10406022
240-10306022
240-10406022
240-10406022
240-10406022
240-47006022

240-47406022
240-10406022

computczr Inc.

-25a-

COMPONENT LISTING - APPLE MONITOR #656-0104
APPLE PART U

CODE

DESCRIPTION

C1
C2
C3
C4

(not used)
Capacitor,
Capacitor,
Capacitor,

35v
16v
16v

048 127-0001
049 127-0101
049 127-0101

CR1
CR2
CR3

5%, 10v
Diode, Zener
Diode, Switching 1N4150 50v
Diode, Switching 1N4150 50v

'050 371-5240
035 371-4150
035 371-4150

R1
R2
R3
R4
R5
R6
R7
RS
R9

Resistor
56
Resistor lOOK
(not used)
Resistor
33K
Resistor
10K
Resistor
2K
Resistor lOOK
Resistor lOOK
Resistor
22K

Q1
Q2

Transistor, NPN Sw.& Amp. 2N3904
Traqsistor, NPN Sw.& Amp. 2N3904

003 372-3904
003 372-3904

U1

Transistor, NPN Optocoupler
Voltage Detector/Indicator, 8 Pin

054 327-0011
055 353-8212

U2

1uF,
10uF,
10uF,

20%,
20%,
20%,

ohm 1/2w 5%
ohm
1w 10%

041 101-2560
042 107-0023

ohm
ohm
ohm
ohm
ohm
ohm

043
045
047
044
044
046

1/4w
1/4w
1/4w
1/4w
1/4w
1/4w

5%
5%
5%
5%
5%
5%

101-4333
101-4103
101-4202
101-4104
iOl-4104
101-4223

computczr Inc.

-26-

COMPONENT LISTING - ASTEC AAI177I
CODE_

DESCRIPTION_

PART NUMBER

BR1

Bridge rectifier KBP10

226-30500010

C1

MP ·cap O.OluF +-20% 250VAC

068-10300010

C2

Cer cap 2200pF +-20% 400VAC

055-22220001

MP cap 2200pF +-20% 250VAC
C3

or

Cer cap 2200pF+-20% 400VAC
.RP cap 2200pF

068-22200020
055-22220001

+-20v.-250VA~

or

068-22200020

C4

MP cap O.luF +-20% 250VAC

068-10400010

C6

Elect cap 47uF +100-10% 250V

057-47020040

C7

Elect cap 47uF +100-10% 250V

057-47020040

e8

Elect cap 47uF +100-10% 250V

057-47020040

C9

Elect cap 47uF +100-10% 250V

057-47020040

elO

Elect cap 220uF +-20% 10V SXA

057-22120300

ell

Cer cap 470pF +-20% 3KV Z5P

055-47167728

e12

Poly cap 0.22uF +-10% 100V

058-22400120

e13

Elect cap 1000uF +-20% 16V SXA

057-10220180

C16

Elect cap 100uF +-20% 25V

057-10120270

C18

Poly cap

0~022uF

SXA

+-20% 100V

058-22300080
or

e19

Poly cap 0.22uF +-10% 100V

058-22300090
058-22400120

or

058-22400240

e20

Elect cap 1000uF +-20% 16V SXA

057-10220180

e21

Elect cap 1000uF +-20% 16V SXA

057-10220180

e22

Elect cap 100uF +-20% 25V SXA

057-10120120

e24

Elect cap 2200uF +-20% 10V SXA

057-22220120

computczr Inc.

-27-

COMPONENT LISTING - ASTEC AAl1771
CODE

DESCRIPTION

PART NUMBER

C25

Cer cap O.OluF "+-201. lKV Z5U

055-10368925

C26

Cap Poly 0.22uF 100V

058-22400120

,

CeraD!i.c_ 9 .~OluL 100V

055-103821~'

C27

C~p

C28

Cap Tant 10uF 25V

072-10600070

C29

Cap Tant 10uF 25V

072-10600070

C30

Cer cap 470pF +-101. 100V Z5F

055-47152126

C31

MP cap O.OluF +-201. 250VAC

068-10300010

C32

Cap ceramic 0.01uF 100V

055-10382125

Dl

Rectifier RGPI0B

226-10400070

D2

Rectifier RGPIOJ

226-10400060

D3

Rectifier RGPI0M

226-10400100

D4

Rectifier RGP15B

226-10100040

D5

Rectifier RGP10B

226-10400070

D6

Silicon diode IN4606

212-10700210

D7

Silicon diode IN4606

212-10700210

D8

Schottky diode S3SC3M

212-31100030

D9

Schottky diode S3SC3M

212-31100030

D11

Rectifier 384M

226-11400010

D13

S il i con diode IN4606

212-10700210

D14

Diode IN4606

212-10700210

D15

Diode IN4606

212-10700210

D16

Diode IN4606

212-10700210

computc:!r Inc.

-28COMPONENT LISTING - ASTEC AAl1771
CODE

DESCRIPTION

PART NUMBER.

F1

Fuse 2. 5A 250V' 3AG

084-00200060

Ll

Common mode choke assembly

852-20200120

L2

Toroid

124-00000110

L3

Toroid

r24-00000rro

L4

Base choke 2.2uH

328-00100030

L5

Choke 1.5mH

328-00100010

L6

Choke coil assembly

852-20100180

L7

Choke coil assembly

852-20100180

L8

Choke coil assembly

852-10100490

Ql

NPN transistor SD467

209-11700460
or

209-11700400

Q2

NPN transistor 2SC1875

209-10200030

Q3

PNP transistor SB561

210-11700350
or

210-11700330

Q4

2SB561C

210-11700353

Q5

2SD467C

209-11700463

Q6

2SD467C

209-11700463

Q7

2SD467C

209-11700463

Q9

TL431CLP

211-10800100

Q10l

TL431CLP

211-10800100

cornputc!r Inc.

-29-

COMPONENT

LlSTI~G

- ASTEC

~11771

CODE

DESCRIPTION.

PART NUMBER

R1

Thermistor 4R +-10%

258-40970015
or

258-50990010

or·

-258-60990010-

R2

Resistor carbon film lOOK +-5% lW

240-10406033

R3

Resistor carbon film lOOK +-5% lW

240-10406033

R4

Resistor metal oxide film 68R +-5% lW

248-68006052

R5

Resistor carbon film 820R +-5% ~

240-82106022

R6

Resistor carbon film 5.6R +-5% ~

240-56906022

R7

Resistor metal oxide film l20R +-5% 1W

248-12106052

R8

Resistor carbon film 5.6R +-5%

R9

Resistor carbon film 47R +-5% ~

240-47006022

RIO

Resistor carbon fi 1m lOR +-5% ~

240-10006022

Rll

Resistor carbon film 5. 6R +-5% ~

240-56906022

R12

Resistor metal film 0.47R +-5% lW

247-04786054

R13

Resistor carbon film

R14

Resistor carbon film 270R +-5% \W

240-27106033

R15

Resistor carbon film 330R +-5% \W

240-33106033

R16

Resistor carbon film 8.2R +-5%

~

240-82906022

R17

Resistor carbon film 330R +-5% ~

240-33106022

R18

Resistor carbon film l2R +-5%

~

240-12006022

R19

Resistor carbon film 56R +-5% ~

240-56006022

R20

Resistor carbon film 56R +-5%

tw

240-56006022

R2l

Resistor carbon film 12K +-5%

tw

240-12306022

R22

Resistor carbon film 470R +-5%

~

240-47106022

R24

Resistor carbon film 2.7K +-2%

tw

247-27015022

3~R

+-5%

~

~

240-56906022

247-39006022

computar Inc.

-30-

COMPONENT LISTING - ASTEC AAl177l
CODE -

DESCRIPTION

PART NUMBER

R26

Resistor carbon fi 1m 2. 7K +-2% \W

247-27015022

R27

Resistor metal film 1R +-5% 1W

247-10086054

R28

Resistor CF 12K 5%--\W

240-12306022

R29

Resistor CF 2.7K 5% \W

240-27206022

R30

Resistor CF 100R 5% \W

240-10106022

R31

Resistor CF 470R 5% \W

240-47106022

R32

Resistor CF lOOK 5%

:tw

240-10406022

R33

Resistor CF lOOK 5%

:tw

240-10406022

R34

Resistor CF 10K 5%

R35

Resistor CF lOOK 5%

:tw

240-10406022

R36

Resistor CF lOOK 5% \W

240-10406022

R37

Resistor CF lOOK 5% \W

240-10406022

R38

Resistor CF 56R 5% \W

240-56006022

R39

Resistor CF 56R 5% \W

240-56006022

R40

Resistor CF 1K 5% \W

240-10206022

R41

Resistor CF lOOK 5%

:tw

240-10406022

R42

Resistor CF lOOK 5% \W

240-10406022

R43

Resistor CF 220K 5% \W

240-22406022

R44

Resistor CF lOOK 5%

:tw

240-10406022

R45

Resistor CF 220K 5% \W.

240-22406022

R46

Resistor CF lOOK 5% \W

240-10406022

R48

Resistor CF lOOK 5% \W

240-10406022

:tw

240-10306022

computar Inc.

-31-

COMPOBENI LISTIN9 - ASIEC AAl1771. __

DESCRIPTION

paT NUMBER

T1

Power transformer ass'y

852-10201210

T2

Control transformer ass'y

852-10200680

SCR1

SCR C122U

221-13000010

-

VDR1
Zl

256-26100014
Zener 5.6 +5$ lW 40mA

222-56086002

compt.Dzr Inc.

-32-

ASTEC - APPLE PART NUMBER CROSS REFERENCE LISTING
ASTEC PART

{I

APPLE

DESCRIPTION

-------

-------------

TF-10200200
TF-10200370
TF-20100010
TF-20100020
TF-20100050
TF-20200010
042-02012202
055-10210001
055-10367325
055-10368925
055-22220001
055-47167728
057-10220020
057-22120060
057-22120080
057-33120080
057-47020040
057-68120010
058-10200020
058-10400100
058-22300080
058-22400120
068-10400010
072-22600040
084-00200040
209-10200020
209-10200030
209-11700382
209-11700400
210-11700322
210-11700330
211-10800100
212-10700210
222-06895003
222-12295001
222-98085002
226-10100040
226-10400050
226-10400070
226-10400100
226-30500010
227-12500010
227-13000010

CONTROL TRANSFORMER ASSEMBLY
POWER TRANSFORMER ASSEMBLY
FILTER QiOKE COIL ASSEMBLY, RADIAL
FILTER QiOKE COIL ASSEMBLY, RADIAL
FILTER QiOKE COIL ASSEMBLY, RADIAL
TRANSFORMER, COMMON MODE ASSEMBLY
P.C. BOARD (ASTEC 11040 STD.)
CAPACITOR, CERAMIC DISC, lSU,
1000pF,
CAPACITOR, CERAMIC DISC,
O.OluF,
CAPACITOR, CERAMIC DISC, lSU,(VDE) O.OluF,
CAPACITOR, CERAMIC DISC,
(VDE) 2200pF,
CAPACITOR, CERAMIC DISC, lSP,(VDE)
47pF,
CAPACITOR, ELECTRO.,SW.TYPE,RDL.LD.,1000uF,
CAPACITOR, ELECTRO.,SW.TYPE,RDL.LD., 220uF,
CAPACITOR, ELECTRO.,
RDL.LD., 220uF,
CAPACITOR, ELECTRO.,SW.TYPE,RDL.LD., 330uF,
CAPACITOR, ELECTRO.,SW.TYPE,RDL.LD., 47uF,
CAPACITOR, ELECTRO.,SW.TYPE,RDL.LD., 680uF,
CAPACITOR, METALIZED POLY, RDL.LD., 1000pF,
CAPACITOR, METALIZED POLY, RDL.LD.,O.luF,
CAPACITOR, POLYESTER FILM, RDL.LD., .04~uF,
CAPACITOR, POLYESTER FILM, RDL.LD. ,0.22uF,
CAPACITOR, METALIZED POLY,
O.O.luF,
CAPACITOR, TANTALUM,
RDL.LD. , 22uF,
FUSE, 2.75A, 125V
TRANSISTOR, NPN 2SC1358
TRANSISTOR, NPN 2SC1875
TRANSISTOR, NPN PE8050
TRANSISTOR, NPN 2SD592NC/2SD467C
TRANSISTOR, PNP PE8550
TRANSISTOR, PNP 258621NC/2SB561C
I.C. ,OPTICAL COUPLER, TL431CP/TL431CLP
DIODE, SILICON, 1N4606
DIODE, ZENER,
6.8V +/-0.2V
DIODE, ZENER, 12.2V +/-0.2V
DIODE, ZENER,
9.8V +/-0.2V (2K7)
RECTIFIER, RG15B
RECTIFIER, RGP10A (G.I.)
RECTIFIER, RGP10B
RECTIFIER, RGP10M (G.I.)
RECTIFIER, BRIDGE, KBP10
RECTIFIER, SCR, 2P 05M
RECTIFIER, SCR, C122U/2N6395

-------

{I

------

3KV
1KV
1KV
400V
3KV
10V
10V
10V
16V
250V
16V
50V
400V
100V
100V
250V
16V

U157-0005
Ul57-0004
Ul55-0008
Ul55-001O
U155-0009
Ul57-0006
U820-0010
Ul32-0003
Ul32-0004
U132-0002
Ul32-0001
Ul31-0001
U128-0003
Ul24-0004
U126-0001
U124-0002
U124-0001
U124-0005
Ul21-0102
Ul21-0101
Ul19-0002
U119-0001
Ul21-0100
U127-0001
U74o-0001
U376-0005
U376-0002
U376-0004
U376-0001
U376-0006
U376-0003
U327-0001
U371-0001
U371-0003
U371-0004
U371-0002
U375-0015
U375-0014
U375-0016
U375-0013
U351-0001
U376-0007
U372-0001

computar Inc.

-33-

ASTEC - APPLE PART NUMBER CROSS REFERENCE LISTING
ASTEC PART /I

DESCRIPTION

--------240-10006022

---------------------------------------RESISTOR, CARBON FILM, +-5% 1/4W 10 OHM

240-10106022
240-10406022
240-12206022
240-12306022
240-15406033
240-18206022
240-22206022
240-27106033
240-27206022
240-47106022
240-56006022
240-56106022
240-68106022
240-82006033
247-03386054
247-05686054
247-10086054
248-12106052
248-22106052
248-27006052
248-27006063
247-27015022
256- 261000 14
258-40970015
283-02200100
328-00100010
328-00100030
328-00150016
328-20100010
852-10100370
852-10100490
852-10200680
852-lO200940
852-20100140
852-20200950
853-00200210
853-00200020

RESISTOR, CARBON FILM, +-5% 1/4W 100
RESISTOR, CARBON FILM, +-5% 1/4W lOOK
RESISTOR, CARBON FILM, +-5% 1/4W 1.2K
RESISTOR, CARBON FILM, +-5% 1/4W 12K
RESISTOR, METAL FILM, +-5% 1/2W 150K
RESISTOR, CARBON FILM, +-5% 1/4W 1.8K
RESISTOR, CARBON FILM, +-5% 1/4W 2.2K
RESISTOR, CARBON FILM, +-5% 1/4W 270
RESISTOR, CARBON FILM, +-5% 1/4W 2.7K
RESISTOR, CARBON FILM, +-5% 1/4W 470
RESISTOR, CARBON FILM, +-5% 1/4W 56
RESISTOR, . CARBON FILM, +-5% 1/4W 560
RESISTOR, CARBON FILM, +-5% 1/4W 680
RESISTOR, METAL FILM, +-5% 1/2W 82
RESISTOR, METAL FILM, +-5% 1 W .33
RESISTOR, METAL FILM, +-5% 1 W .56
RESISTOR, METAL FILM, +-5% 1 W 1
RESISTOR, MIL-OX FILM, +-5% 1 W 120
RESISTOR, MIL-OX FILM, +-5% 1 W 220
RESISTOR, MTL-OX FILM, +-5% 1 W 27
RESISTOR, MIL-OX FILM, +-5% 2W 27
RESISTOR, MIL-OX FILM, +-2% 1/4W 2.7K
TRANSIENT SUPPRESSOR, VDR 260VAC
THERMISTOR, 4R, 10% or 5R
VOLTAGE SELECTION SWITCH 115/230
CHOKE, 1.5 mH, RADIAL
BASE CHOKE, 2.2 uH, RAD IAL
CHOKE COIL, CONTROL, RADIAL
CHOKE COIL ASSEMBLY, RADIAL
CHOKE COIL ASSEMBLY, RADIAL
CHOKE COIL, RADIAL
CONTROL TRANSFORMER ASSEMBLY
POWER TRANSFORMER ASSEMBLY
CHOKE COIL ASSEMBLY, RADIAL
COMMON MODE TRANSFORMER ASSEMBLY
RECTIFIER ASSEMBLY
RECTIFIER, HEATSINK ASSEMBLY

OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM
OHM

OHM
OHM
OHM

APPLE II

----U101-4100
U101-4101
U101-4104
UlOl-4122
UlOl-4123
Ul07-0001
UlOl-4182
U101-4222
U101-4271
UlOl-4272
U101-4471
UlOl-4560
U101-4561
U101-4681
U107-0001
U107-001O
U107-0004
Ul07-0006
U107-0003
U107-0008
Ul07-0009
Ul07-0002
Ul07-0005
U377-0001
Ul07-0100
U705-0003
Ul55-0003
U155-0002
U155-0007
U155-0005
U155-0004
U155-0006
Ul57-0003
Ul57-0002
Ul55-0001
U157-0001
U375-0017
U375-0018

computczr Inc.

-34-

With Compliments

wm
ASTEC

EUROPE LTD

NOTES ON POWER SUPLIES

CONTENTS

1.0

Introduction

2.0
3.0

What's a Power Supply

4.0

Advantages

5.0

Types of SMPS

6.0

How to read Data Sheets

SI"IPS 8asics
~

Disadvantages of SMPS

Appencli'X.

ASTEC EUROPE LTD

November 1981

computczr Inc.

-35-

1. 0 I r":7R:DUCT I ON

---------------ASTEC manufactures flyback and feed-forward, single and
multi-rail output Power Supplies.
The Company places a

lot of emphasis on the production of

ultra-reliable power supplies. Special consideration is given to
thermal criteria during the design phase. High 1emperature (125
dt5'g C) reverse bias Bur'n-in for a minimum of 24 hour's is standard
procedure for al I critical

transistors and diodes. Elimination of

doubtful components by comparative measurements before and after
Burn-in prior to their use in asseUtbly contribute to our ability
to ship Power Supplies that will continue to give years of
satisfactory life.
Additional
be found

information concel~ning our rilanufactl.lrinq pl~OCIi'SS ~,Ii II

in the Appendix.

Elec'tro-rttagnetic disturbances fl~om Switching Mode POtoller Supplies
are a po t en t i a I

prob I em. ASTEC so I ves

t

hese pl~ob I ems and reduces

both" ine conducte-d and radiatlli!'d radio fl~eql.\ency noise to .eet
the International performance standards by incorporating
correctly designei::t line filters and electrostatic shielding of
the powt5'r switching transformer.
In the following pages we will be describing in detail
cir~ui t

the

tecniques w. use and compal~ing various types of Power

Supply solutions.
A section is devoted to an explanation of how to read and
interpret our DatA Sheets.

computar Inc.

I

-36-

2.0 WHAT IS A POWER SUPPLY?

In

~ss~nc~

Lin~ar

are two basic

th~r~

Suppli~s

-

seri~s

typ~s

and shunt

Charact~ris~d

of

r~gulated

pow~r

supplies.

vari~ti~s.

by dissipatinq as heat the

Switching Supplies - bucK and boost varieties
Characteris~d

input

pow~r

tht is required and

by using only that part of the
h~nce

not dissipating the surplus

as heat


To look at these varieties in a

littl~

more detail:-

2.1 Linear supplies.
A

lin~ar

r~gulator

absorbs the difference

between the input voltage at the source and the regulated voltage
at the load.
(se~

fig 1)

_~-:-,I
E.1N

..,..

otSSrPA-noN

'IN

E.olJ'j'

=

~ :LL
-

E.O'-lT

---------=--

F lGt ,.

computar Inc.

-37-

2.2 Switching

suppli~s.

A SwilchinQ regulator
pow~r

in a

stor~s

th~

exc~ss

LC filter ( a network consisting of an inductor and a

capacitor) and delivers the power to the load in measured
inte-rvals.
Tbe two basic varieties of switching regulators are:2.2. 1 Eluc K•

(see fig 2)

During the time- the switch is ON, energy is stored in the networK
consisting of the inductor L and capacitor C and is delivered to
the load as require-d.
The output voltage of the BucK regulator is

controll~d

by the

duty cycle of the switch.
E out

=

t.on • E in
T

Th~

output voltage may be controlle-d from zero volts to E in.

2. 2. 2 Boos t

•

(see fig 3)

The Boost regulator is similar to the BucK regulator except that
the circuit is designed to

provid~

an output

voltaq~

that

is

highe-r than the input voltage.

computczr Inc.

-38-

L
0

~t--~
!5.;w

SW"c..H

IN

-

1~~

t

00.

U

C

....

-

\

OUT

~

1:;.01\

-=rJ:
F\..J

T

,

24 - 96 HRS. BURN IN

'.

«

Comparison of test results enables us to reject

~

any units showing parameter changes likely to

z

t-

(J)

w

cause failures during use.

t-

16 STEP COMPUTER TEST

I

L-

OA

1
PACKING

T
STORE

I

It is our target to offer a power supply that
system designer can specify with absolute
confidence. can fit and can then forget. The
name ASTEC is synonymous with Qualitv
and reliability.

computczr Inc.

SWITCHING

POWER

SUPPLIES

Editor's note: The material for this article
was edited from HP's DC Power Supply
Handbook IAN 90B), originally written
by Richard Tomasetti of the Jfarketing
Communications group at HP's power
supply division in Rockaway, New
Jersey.

-56-

Therefore. a switching power
supply is defined as an ac in, dc
out, constant voltage power supply that uses a "switching technique" for regulation.

Electronic power supplies are defined as units that convert power
from an ac or dc source into ac or dc
power at voltages suitable for supplying an electronic device.

Basic Switching Supply
In a switching supply, the regulating elements consist of seriesconnected transistors that act as
rapidly opened and closed switches
(Figure 1). The input ac is first converted to unregulated Clc. then
..cfiopped" by lbe SWIt.chlnrz elp.ment
operatmg at a rapHf rate (typlcaUy
20kHz). The resultant ~Ukaz -pulse
train i~ transformer-coupled to an
output network which provides final
rectification and smoothing of the de
output. Regulation is accomplished
through control circuits that vary
the on-off periods (duty cycle) of the
switching elements.

Within this definition, electronic
power supplies can be divided into
four broad classifications:
(1) ac in, ac out line regulators and frequency changers
(2) dc in, dc out - converters
and dc regulators
(3) de in, ac out - inverters
(4) ac in, dc out - "common"
power supply
This last category is by far the most
common of the four and is generally
the one referred to when speaking of
a "power supply."
Four basic outputs or modes of
operation can be provided by dc output power sHpplies:
• Constant Voltage: The output
. voltage is maintained constant in
spite of changes in load, line, or
temperature.
• Constant Current: The output
current is maintained constant in
spite of changes in load, line, or
temperature.
• Voltage Limit: Same as Constant
Voltage except for less precise
regulation characteristics.

Figure 1. Basic Switching Supply

Operating Advantages. Because
switching regulators are basically
on/otr devices, they avoid the higher
power dissipation associated with
the rheostat-like action of a series
regulator. The switching transistors
dissipate very liRie power when
either saturated (onl or nonconducting (om: most of the power losses
occur elsewhere in the supply. Efficiencies ranging from 65% to 85%
are typical forswitching supplies, as
compared to 30% to 45'IC efficiencies
for linear types. With less wasted
power, switching supplies run at
cooler temperatures, cost less to operate, and have smaller regulator
heat sinks.

• Current Limit: Similar to Constant Current except for less precise regulation.
Within each type of power supply,
different forms of regulation are
used to maintain a constant output.
Switching is one of the forms used in
a constant voltage power supply.

I.

.~ppIcz computczr Inc.

-57-

The size and weight reductions for
switching supplies are achieved because of their high switching rate.
The power transformer, inductors,
and filter capacitors for 20kHz
operation are much smaller and
lighter than those required for
operation at power line frequencies.
Typically, a switching supply is less
than one-third size and weight of a
comparable series regulated supply.
Another aspect of performance is the
switcher's ability to operate under
low ac input voltage (brownout) conditions and substain a relatively
long carryover (or holdup) of its output if input power is lost momentarily. The switching supply is superior
to the linear supply in this regard
because more energy is stored in its
input filter capacitance. In a switching supply, the input ac is rectified
directly and the filter capacitor
charges to the voltage peaks on the
ac line. This is opposed to the linear
supplies' ac input being stepped
down through a power transformer,
then rectified, which results in a
lower voltage across its filter
capacitor.
Since the energy stored in a
capacitor is proportional to CV2, and
V is higher in switching supplies,
their storage capability (and thus
their holdup time) is better.
Operating Disadvantages. Although its advantages are impressive, a switching supply does have
some inherent operating characteristics that could limit its
effectiveness in certain applications.
One of these is that its transient recovery time (dynamic load regulation) is slower than that of a series
regulated supply. In a linear supply,
recovery time is limited only by the
speeds of the semiconductors used
in the series regulator and control
circuitry. However, in a switching
supply, recovery is limited mainly
by the inductance in the output ~l­
ter. This mayor may not be of Slgnificance to the user, depending
upon the specific application.

AlsQ~

electro-ma.xnetic interference
(EM!) is a natural by-product of the
o~-off switching. This Interference
can be conducted to the load (resulting in higher output ripple and
noise), it can be conducted back into
the ae line, and it can be radiated
into the surrounding atmosphere.
For this reason, all HewlettPackard switching supplies have
built-in shields and filter networks
that su'bstantiallv reduce EM! and
control output ripple and noise.
Typical Switching Regulated
Power Supply
Figure 2 shows a schematic of one of
HP's higher power, yet less complex, switching supplies. Regulation
is accomplished by a pair of pushpull switching transistors operating
under control of a feedback network
consisting of a pulse-width modulator and a voltage comparison
amplifier. The feedback elements
control the ON periods of the
switching transistors to adjust the
duty cycle of the bipolar waveform
(E) delivered to the putput rectifierl
filter. Here the waveform is rectified
and averaged to provide a de output
level that is proportional to the duty
cvcle of the waveform. Hence, inc~easing the ON times of the
switches increases the output voltage and vice-versa.
The waveforms of Figure 2 provide
a more detailed picture of circuit
operation. The voltage comparison
amplifier continuously compares a
fraction of the output voltage with a
stable reference (EREF) to produce
the V CONTROL level for the tum-on
comparator. This device compares
the VCONTROL input with a triangular ramp waveform (A) occurring at
a fixed 40kHz rate. When the ramp
voltage is more positive than the
control level. a turn-on signal (B) is
generated. Notice that an increase
or decrease in the VCONTROL voltage varies the width of the output
pulses at B and thus the ON time of
the switches.

computczr Inc.

OUTPuT

r - -ilECT/f'l TER----;
='

I

@ .. IIP

'co.'OO.
140"."

-58A.
A.
v::v.;v.~:v
,
,.

A.

,

@TURN'ON COIIP
ouTPuT

,

A.

I

I

I

I

,

CD

IIO~~"R~:rOI ~o...--1._~-!nL'_;-,.;.'_

@

1100 OR,vE.02

I

I

i i '
1

I

I:

I

i

I

L-~:__~_~
,,

;01 0111

,

I

QZOM

Flgur. 2. Switching Supply with Push· Pull rrarllistors and Feedback for Regu/aUon

Steering logic within the modulator
chip causes switching transistors
Ql and Q2 to turn on alternately, so
that each switch operates at onehalf the ramp frequency or 20kHz.
Included, but not shown, in the
modulator chip are additional circuits that establish a minimum
"dead-time" (off time) for the
switching transistors. This ensures
that both switching transistors cannot conduct simultaneously during
maximum duty cycle conditions.
Ac Input Surge Current Protection. Because the input filter
capacitors are connected directly
across the rectified line, some form
of surge protection must be provided
to limit line surge currents at
turn-on. If not controlled, large
surges could trip circuit breakers,
weld switch contacts, or affect the
operation of other equipment connected to the same ac line. Protection is provided by a pair of thermistors (~to) in the input rectifier
circuit. With their high negative
temperature coefficient of resistance, the thermistors present a
relatively high resistance when cold
(during the turn-on period) and a
very low resistance after they
heat up.
A shorting strap (Jl) permits the
configuration of the input rectifierfilter to be altered for different ac
inputs. For a 174-250Vac input, the
strap is removed and the circuit
functions as a conventional fullwave bridge. For 87-127Vac inputs,
the strap is installed and the input
circuit becomes a voltage doubler.

Switching Frequencies. Presently, 20kHz is a popular repetition rate for switching regulators
because it is an effective compromise with respect to size, cost,
dissipation, and other factors. Decreasing the switching frequency
would bring about the return of the
acoustical noise problems that
plagued earlier switching supplies,
and would increase the size and cost
of the output inductors and filter
capacitors.
Increasing the switching frequency,
however, would result in certain
benefits, including further size reductions in the output magnetics
and capacitors. Furthermore, transient recovery time could be decreased because a higher operating
frequency would allow a proportional decrease in the output inductance, which is the main constraint in
recovery performance.
Unfortunately, higher frequency
operation has certain drawbacks.
One is that filter capacitors have an
Equivalent Series Resistance (ESR)
that limits their effectiveness at
high frequencies. Another disadvantage is that power losses in the
switching transistors, inductors,
and rectifier diodes increase with
frequency. To counteract these
effects, critical components such as
filter capacitors with low ESRs, fast
recovery diodes, and high-speed
switching transistors are required.

computczr Inc.

-59-

Some of these components are already available, others are not.
Switching transistors are improving, but remain one of the major
problems at high frequencies. However, further improvements in
high-speed switching devices, such
as the new power Field Effect Transistors (FETs) would make high frequency operation and its associated
benefits a certainty for future
switching supplies.
Preregulated Switching Supply
Figure 3 shows a schematic of
another switching supply similar to
Figure 2 except for the addition of a
triac preregulator and associated
control circuit. The triac is a
bidirectional device and is usually
connected in series with one side of
the input primary. Whenever a gating pulse is received, the triac conducts current in a direction that is
dependent on the polarity of the
voltage across it. The goal is to control the triac so that the bridge rectifier output (dc input to the
switches) is held relatively constant. This is accomplished by a
control circuit that issues a phaseadjusted firing pulse to the triac
once during each half-cycle of the
input ac. The control circuit compares a ramp function to a rectified
ac sinewave to compute the proper
firing time for the triac.
Although the addition of the preregulator circuitry increases complexity, it provides three important
benefits.
(1) By keeping the dc input to the
switches constant, it permits
the use' of more readily available lower voltage switching
transistors.
(2) The coarse preregulation it provides allows the main regulator
to achieve a finer regulation.
\3) Through the use of slow-start
circuits, the initial conduction of
the triac is controlled. providing
an effective means of limiting
input surge current.
Note that the preregulator triac is
essentially a switching device and,
like the main regulator switches,
does not absorb a large amount of
power. Hence, the addition of the
preregulator does not significantly
rf'duce the overall efficiency of this
supply.

Single Transistor
ReguJatol'

Switching

A t lower output power levels, a onetransistor p;tch becomes practical.
The single transistor regulator of
Figure 4 is referred to as a forward,
or feed-through, converter. It can receive a de input from either one of
two sources without a change in its
basic configuration. For ac-to-dc
requiremeafis, the regulator is connected to • line rectifier and SCR
preregulatar. For dc-to-dc converter
applicatious it is connected directly
to an external dc source.
Like the previous switching
supplies, the output voltage is controlled by DrYing the ON time of
the regulator switch. The switch is
turned on by the leading edge of
each 20kHz clock pulse and turned
off by the pulse-width modulator
at a time determined by output load
conditions..
While the regulating transistor is
the half-wave rectifier
diode is forward biased and power is
transferred to the output filter and
th,t load . When the regulator is
turned off. the "flywheel" diode conducts, sustaining current flow to the
load during the off period. A
flywheel diode (sometimes called a
freewheeling or catch diode) was
not required in the two transistor
regulators of Figures 2 and 3 because of their full-wave rectifier
conti guration.
conducting~

Another item not found in the previous regulators is "nyback" diode
CRF. This diode is connected to a
third transformer winding which is
bifilar wound with the primary.
During the off periods of the switch,
CRF is forward biased, allowing the
return ofsw-plus magnetizing current to the input filter, and thus preventing saturation of the transformer core. This is an important
function because core saturation
often leads to the destruction of
switching transistors. In the. previously described two transistor
push-pullrircuits, core saturation is
easier to avoid because magnetizing
current is applied to the core in both

computczr Inc.

-60PII(It(WoUDI'
TRII'

Figure 3. Push-Pull Sw/rchlng Supply w/rh Triac Prereflllllllor

'.000

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1I1(IIIIiAL DC

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Figure 4. Single Transistor Switching
Regulator called II Forward or
Feed-Through Comferfer

Figure 5. Sammal)' of Basic Switching

""'a'or Configurations

directions (Le_. before saturation.
the current is reversed). Nevertheless. matched switching transistors
and balancing capacitors must still
be used in ~hese configurations to
ensure that core saturation does not
occur.
Configuration B is a useful alternative to push-pull operation for lower
power requirements. It is called a
forward or feed-through converter
because energy is transferred to the
power transformer secondary im·
mediately following turn-on of thE
switch. Although the ripple fre·
quency is inherently lower, OUtpUl
ripple amplitude can be efTectivel~
controlled by the choke in the outpu'
filter. Two-transistor configuratioD.!
of forward converters also exis'
wherein both transistors art
switched simultaneously. They pro
vide the same output power as tho
single transistor versions but tho
transistors need handle onl~' halfth.
peak voltage.
-

Summary of Basic Switching
Regulator Configurations
Figure 5 SDaws three basic switching
regulator CDDfigurations that are
often used ia today's power supplies.
ConfiguratiIIIID. A is of the push-pull
class, and dais version was used in
the switcma:g supplies shown in
Figures 2 aacI 3. Other variations of
this circuit are used also, including
two-transistar balanced push-pull
and four tnmsistor bridge circuits.
As a group,push-pull configurations
are the most effective for lowvoltage, hiP-power and high performance .,lications. Push-pull
circuits haa the advantage of a ripple frequeflq' that is double that of
the other bvo basic configurations
and, of ceu:se, output ripple is
inherently lawer.

computar Inc.

-61-

Configuration C is known as a
flyback, or ringing choke, converter
because energy is transferred from
primary to secondary when the
switches are off (during flyback). In
the example, two transistors are
used and both are switched simultaneously. While the switches are on,
the output rectifier is reverse biased
and current in the primary inductance rises in a linear manner.
When the switches are turned off,
the collapsing magnetic field reverses the voltage across the primary, and the previously stored energy is transferred to the output filter and load. The two diodes in the
primary protect the transistors from
inductive surges that occur at turnoff.
Flyback techniques have long been
used as a means of generating high
voltages (e.g., the high voltage
power supply in television receivers). As you might expect, this configuration is capable of providing
higher output voltages than the
other two methods. Also, the fly back
regulator provides a greater variation of output voltage with respect to
changes ih duty cycle. Hence, the
flyback configuration is the most obvious choice for high, and variable
output voltages while the push-pull
and forward configurations are more
suitable for providing low, and fixed
output voltages.
Protection Circuits for Switching
Supplies
Figure 6 shows typical protection
circuits that are used in HP switching regulated power supplies. The
following is a brief descr~ption of
those protection circuits shown.
A. EMI Filter. Helps prevent high
frequency spikes (RFl) from being
conducted to the load or back into
the ac line. HP switching supplies
also contain built-in shields for additional control of conducted and
radiated interference.
B. Thermistor. Limits ac input
surge current by its negative temperature coefficient of resistance.

Has a high resistance when cold
(during turn-on) and low resistance
after it heats up.
C_ Regulator Overcurrent Limit_
This circuit is much faster than the
current limit comparator and protects the regulator switches from
overcurrent conditions of a transient
nature. It monitors current flow
through the switches and prevents it
from exceeding a hannful level.
D. Output Rectifier Diodes. Besides final rectification, these diodes
also protect internal components
against reverse currents that could
be injected into supply by an active
load or series connected supply.
E. AC Undervoltage. This circuit
perfonns a dual function. It protects
the supply from damage that could
result from a prolonged condition of
low ac input voltage, and it limits
output overshoot during turn-on.
During undervoltage or turn-on
conditions, the low ac input level reduces the V BIAS voltage and activates the undervoltage detector.
When activated, the modulator
pulses are inhibited and the regulator switches turned off.
F. Overvoltage Detector. !\ionitors
output voltage and turns off regulator switches if output attempts to
rise above a preset value. Similar to
a crowbar circuit except that output
voltage is removed by turning off
regulator rather than by shorting
the output.
G. Temperature Switch. Opens in
case of high ambiel'1t temperature
that could be caused, for example, by
a misapplication or cooling fan failure. The switch opens and removes
VBIAS '''hich activates the ac l'ndervoltage detector. The switch closes
again after temperature cools to a
safe level.

=:-l
"-________-"--____~_Dl_n_ra_p_~---~ I

-62-

~
\

r-;WI~~~ING, \
Art

+OUT

'It-t--':''--....,

Fll TER

,OUT

+OUT

Figure 6. Protection Circuits, Switching Type Supply

SWITCHING

SUPPLY

The following is a brief glossary of
terms encountered in 'dealing with
switching supplies.
Brown Out Rated
The ability of a power supply to
maintain regulated output voltages
in the event that the input line voltagp should drop to a low or zero
level.
FOLD BACK

TERMINDLDGY
crossover point and begins to approach a short circuit. Also known as
output short circuit protection, this
mechanism monitors the output current and, if it exceeds a preset crossover value, turns down the regulator
output.

EMI (RFI)
Electromagnetic interference (radio
frequency interference' - unwanted
high frequency energy caused
primarily by the switching components in the power supply, EMI can
be conducted through the input or
output lines or radiated through the
unit's case. Conducted EMI (RFD
can be reduced using proper filtering, and radiated EMI (RFl) can be
reduced by judicious board lavout
and enclosing the supply in a ~etal
enclosure.
The terms "noise" EM! and RFI are
sometimes used in the same context.

Current FoJdback
An overload protection
where output voltage and
decrease simultaneously as
re~istance decreases below

method
current
the load
a preset

computar Inc.

-63-

ESR (Equivalent Series
Resistance)
The amount of resistance in series
with an ideal (lossless) capacitor
which exactly duplicates the performance of a real capacitor. In general, the lower the ESR, the better
the quality of the capacitor and the
more effective it is as a filtering
device. ESR is a prime determinant
of ripple in switching supplies.
F1yback
Precisely, it's the shorter of the two
time intervals comprising a sawtooth wave. In a switching power
supply, the shorter interval is produced when the transistors are
swit.ched off. This causes a rapidly
collapsing magnetic field in the
transformer which reverses the
voltage across the primary, transferring a high energy to the output.
Ground Loop
A feedback problem caused by two or
more circuits sharing a common
electrical line, usually a common
ground line. Voltages gradients in
this line caused by the first circuit
may be resistively, inductively, or
capacitively coupled into the other
circuit via the common line. With
power supplies, this problem can be
reduced using single point grounding near the supply.
Hold-up Time
The total time any output will
remain within its regulation band
after line input voltage has suddenly
dropped to zero or below rating.
Hold-up is measured at full load and
nominal line conditions.
Input Surge Current
The peak line current which flows
during turn-on. Surge current is
caused by charging of the input
capacitor, and limited primarily by
an inp~t thermistor or preregulator.
Input Voltage Range
The range of line voltages for which
the power supply meets its specifications. The lowest line voltage is important in defining the relative degree of brown-out protection.

Isolation Voltage
The maximum voltage by which any
part of the circuit can be operated
away from chassis ground. Also the
maximum voltage between any output and input terminaL.
Line Regulation
See Source Effect.
Line Frequency Regulation
The variation of an output voltage
due to a change in line input frequency with all other factors held
constant. This effect is negligible in
switching and most linear supplies,
but· is very critical in ferroresonant
supplies.
Load Effect Transient Recovery
Time
Sometimes referred to as transient
recovery time or transient response
time, it is, loosely speaking, the time
required for the output voltage of a
power supply to return to within a
level approximating the nonnal dc
output following a sudden change in
load current. More exactly, Load
Transient Recovery Time for a CV
supply is the time "X" required for
the output voltage to recover to, and
stay within "Y" millivolts of the
nominal output voltage fonowing a
"z" amp step change in load current
- where:
(1)

"Y" is specified separately for
each model, but is generally of
the same order as the load
regulation specification.

(2)

The nominal output voltage is
defined as the dc level halfway between the steady state
output voltage before and
after the imposed load
change.

(3) ttZ" is the specified load current change, typically equal
to the full load current rating
of the supply.

computar Inc.

-64-

TRANSIENT RECOVERY TIME

i !+I..------rLrf-'
~O

FULL LOAD

'OUI

LOAD

LOAa CURRENT

~
L
'l

I'I-*.

i It -----

EOUT

Y

-~-_OM"AL OUTPUT
.OLTACE

:~ I

I

VOL TAGE RECOVERY

I

,--+

Overcurrent Limiting
A protection mechanism which limits the output current of a supply
without materially affecting the
output voltage.
Overshoot
The amount by which an output exceeds its final value in a transient
response to a rapid change in load or
input voltage. In power supp'ly design this parameter is particularly
important at turn-on.

PARD (Ripple and Noise)
The term PARD is an acronym for
"periodic and random deviation" and
replaces the former term ripple and
noise. PARD is the residual ac component that is superimposed on the
dc output voltage or current of a
power supply. It is measured over a
specified bandwidth with all influence and control quantities maintained constant. PARD is specified
in rms and/or peak-to-peak values
over a bandwidth of 20Hz to 20MHz.
Fluctuations below 20Hz are treated
as drift. Attempting to measure
PARD with an instrument that has
insufficient bandwidth may conceal
high frequency spikes that could be
detrimental to a load.

DC OlJ'TPUT OF POWER SUPPLY
AND SUPERI:YIPOSED PARD
COMPONENT

, -I

I ...

i

L

i

I

9

Overvoltage Protection

Peak Charging

A protection mechanism for the load
which reduces the output voltage to
a very low value in the event that
the output exceeds a certain
threshold voltage. In a switching
supply, the regulator is turned off if
the threshold is exceeded, reducing
the output voltage and current to
zero. In linear supplies, an SCR
"crowbar" is used to rapidly place a
short circuit across the output terminals whenever the threshold voltage is exceeded.

A rise in voltage across a capacitor
caused by the charging of the
capacitor to the peak rather than
RMS value of the input voltage. This
generally occurs when a capacitor
has a high discharge resistance
across it and large ripple or spikes on
its input line. In a switcher this effect
determines minimum load (discharge resistance) condi tions on each
output to maintain regulation.

computar Inc.

-65-

Post Regulator
A linear idissipative) regulator used
on the output of a switching supp1y
to further improve over-all regulation performance of the supply. Post.
regulators can be either the 3 terminal I.C. type or a custom discrete
design. Since the differential voltage
across the post regulator can be kept
to a minimum, dissipative losses are
generally smalL
Rise Time and Fall Time
When applied to the switching transistor, that time in which, non-zero
currents and voltages result in high
peak power dissipation. Careful attention must be paid to reducing
these times, particularly when
switching inductive loads.
Ripple and Noise
See PARD.
Short Circuit Protection
See Current Foldback;

Source Effect (Line
Regulation)
Formerly known as line regulation.
source effect is the change in the
steady-state value of the dc output
voltage (of a CV supply) or current
(of a CC supply) due to a specified
change in the source (ac line) voltage, with all other influence quantities maintained· constant. Source
effect is usually measured after a
"complete" change in the ac line
voltage from low line to high line or
vice-versa.
Switcher
A common industry-wide name for a
switching power supply.

Temperature, Coefficient
The average percent change in output voltage per degree change in
temperature with load and input
voltage held constant. The coefficient is usually derived from output
voltage measurements taken at
room temperature (25°C) and at the
two specified operating temperature
extremes.

computczr Inc.

'



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