Elenco Electronics XP-660 Manuel utilisateur

POWER SUPPLY

MODELS XP-660 / XP-760

Instruction Manual

No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

Elenco®Electronics, Inc.

Variable Regulated

Model XP-760

Model XP-660

Specifications for Model XP-660 @ 120VAC input

0-20V Supplies 5V Supply

Input Voltage 110-135VAC 60 Hertz Same

Output Voltage 0-20VDC Variable 5VDC + .1V

Output Current 0-1A over 0-20V range 0-5A

Load Regulation Less than .1V over 0-20V range Less than .15V

Line Regulation Less than .1V 110V to 130V Less than .15V

Ripple RMS Less than 5mV Less than 10mV

Current Protection .05 to 1A Variable current limiting Current foldback

Short Protection .05 to 1A current limit Current foldback

Output Impedance .1 ohms .03 ohms

Specifications for Model XP-760 @ 120VAC input

0-20V Supplies 5V Supply

Input Voltage 110-135VAC 60 Hertz Same

Output Voltage 0-20VDC Variable 5VDC + .1V

Output Current 0-1A over 0-20V range 0-5A

Load Regulation Less than .1V over 0-20V range Less than .15V

Line Regulation Less than .1V 110V to 130V Less than .15V

Ripple RMS Less than 5mV Less than 10mV

Current Protection .05 to 1A Variable current limiting Current foldback

Short Protection .05 to 1A current limit Current foldback

Output Impedance .1 ohms .03 ohms

-1-

Circuit Description

The Elenco®XP-660 and XP-760 use the same

basic power and regulator circuit. The only

difference is in the display function. The XP-660 has

two 0-1mA analog meters. These meters convert to

a voltmeter by placing a 20kΩresistor in series or

an ampmeter by placing a .39Ωshunt resistor

across the meter.

The Model XP-760 has two 3 1/2 digit LED meters.

Voltage is read by connecting the meter to a voltage

divider on the power supply output. Current is read

by connecting the meter to a shunt resistor in series

with the power supply output.

When referring to the schematic diagrams, the

circuit components associated with each supply can

be identified by its number. The 5V supply begins

with 100. The 0-20V Power One Supply begins with

300 numbers and the 0-20V Power Two Supply

begins with 200 numbers. The basic circuit of these

supplies consist of 1) The power source, 2) The

regulator and 3) The readout circuit. These circuits

are shown in Figure 1 and will be discussed in detail

in the following paragraphs.

Figure 1 Block Diagram of 0-20V Power Supply

Power Source

The power supply for Models XP-660 and XP-760

consists of a transformer with four isolated step

down windings. Connected to each winding is a

diode bridge and a filter capacitor. The components

on the Power One Supply are diodes D301, D302,

D303, D304 and capacitor C304. These

components convert the 120VAC input to 25VDC.

0-20V Regulators

Figure 2 shows a simplified circuit of the 0-20V

regulator circuit. This circuit consists of a high gain

amplifier transistor Q305. The gain of this stage is

over 100,000 because of its extremely high load

impedance.This load consists of a current source

transistor Q301 and its biasing circuit. The effective

resistance of this circuit is over 500,000 ohms.

Transistor Q302 is a power device that controls the

output current. Transistors Q303 and 304 are

emitter followers used to prevent loading of the

current source.Q301, Q302, Q305 and VR303 form

a closed negative feedback loop. If you analyze this

loop you will find that when the output voltage goes

down due to increase output current, the voltage at

the base of transistor Q305 goes negative. This

reduces the current in transistor Q305 and thus the

collector voltage will increase, returning the output

voltage to very near its original value. The high gain

is essential to the output voltage. Diode D309 is

added to prevent drift with temperature changes

and to allow the output voltage to go to zero.

To protect the regulator from overloads and short

circuits, transistor Q306 is added. Whenever the

voltage drops across resistor R309 reaches .6V,

transistor Q306 will conduct and lower the collector

voltage of amplifier Q305. To obtain variable current

limiting, transistor Q306 is prebiased via resistor

R309 and VR301 (see XP-660 schematic). This will

allow the output current limit between .05 and 1

amp. Transistors Q307 and Q308 are added to light

the overload LED.

-2-

5V Regulator

The circuit of the 5V regulator is shown on the

schematic with components beginning with number

100. The heart of the regulator is IC1. This IC

contains the same basic circuit as the 0-20V

regulator, previously described (see schematic

diagram of XP-660). Transistor Q102 is the pass

transisitor that controls the output current. Transistor

Q101 is used to increase the impedance of the pass

transistor. Resistor R104 senses the current and

shuts down the IC if the current exceeds 5 amps.

The regulator features a current foldback circuit

which reduces the current to less than 1 amp when

the output is shorted. Resistors R105 and R106 form

the current foldback circuit. Resistors R102 and

R103 are added to form a stable 3.9V reference

voltage for the IC to operate.

XP-760 Digital Meters

Meter operation centers around the 7107 integrated

circuit (IC). This chip contains a dual slope A/D

(analog to digital) converter, display latches, seven

segment decoder, and display drivers.

The input of the 7107 IC is fed to an A/D converter.

Here the DC voltage is changed to a digital format.

The resulting signals are processed in the decoders

to light the appropriate LED segments.

Timing for the overall operation of the A/D converter

is derived from a 40kHz external oscillator. The IC

divides this frequency by four and the resulting clock

pulses are used to drive its decade counters. It is

then further divided to form three convert-cycle

phases. The final readout is clocked at about 2.5

readings per second.

The digitized data is presented to the display as four

decoded digits (seven segments) plus polarity. The

decimal point position on the display is selected by

the Volts/Amps switch.

A/D Converter - Any given measurement cycle

performed by the A/D converter can be divided into

three consecutive time periods, autozero (AZ),

integrate (INTEG) and read. A counter determines

the length of the time periods. The integrate period

is fixed at 1,000 clock pulses. The read period is a

variable time that is proportional to the unknown

input voltage. It can vary from zero counts for zero

input voltage to 2,000 counts for a full scale input

voltage. The autozero period varies from 1,000 to

3,000 counts. For an input voltage less than full

scale autozero gets the unused portion of the read

period.

During the autozero cycle the accumulated offset

voltage errors in the converter are measured and

stored as a voltage on the external autozero

capacitor.This voltage is used to correct for the

offset voltage errors during the read cycle.

During the INTEG cycle the INTEG capacitor is

charged up for 1,000 clock pulses (100ms.), see

Figure 3. The charging rate is determined by the

unknown input voltage. At the end of the integrate

cycle the voltage on the capacitor is proportional to

the unknown input voltage.

During the read cycle the INTEG capacitor is

discharged at a constant rate. The time required for

the discharge is therefore proportional to the

unknown input voltage. This time is converted to a

digital format by counting the number of clock

pulses that occur during the discharge.

Figure 2 Simplified Regulator Circuit

-3-

Counter Output

Figure 3 Dual Slope A/D Converter

Operation Instructions

Check the voltage rating of the equipment to be

powered. Care must be taken not to exceed this

rating.

2) Plug the line cord into a 120V 60Hz AC outlet.

3) Adjust the voltage control to the desired voltage.

Load variation will have practically no effect on

the voltage setting due to the special regulation

circuit.

4) Connect the positive lead of your equipment to

the red output terminal marked (+) and the

negative lead to the black terminal marked (–).

5) Adjust the current limiting control to maximum

counter-clockwise position. Switch your

equipment on. The overload light will glow if

excessive current is drawn. Increase this control

until the light goes out and stays out during

normal use. Your equipment is now protected

from high current surges. An alternate method

of adjusting current limiting is to short the output

and adjust the current to a desired value.

Remove the short. This will now limit the current

to your setting.

6) Meters can be switched to read voltage or

current.

Elenco®Models XP-660 and XP-760 are extremely

versatile power supplies. All supplies are

completely isolated from each other. This means

that they have separate grounds. By tying the

ground terminal of one supply to the positive

terminal of the other, you can obtain an output of 0-

40V @ 1 ampere. Also by stacking the 5V terminal

you can increase the output to 45V.

The 0-20V supplies have an adjustable current

overload feature, a red LED will light when current

limiting is activated. The current limit control adjusts

the maximum current the supply will allow before

automatically turning down the output voltage. This

limit is between 50mA to 1 amp. You can set it to

your desired limit by shorting out the output terminal

and adjusting the current limit control to the desired

current. Remove the short and attach the load. The

maximum current drawn will be per your setting.

All three power supplies are protected against

external shorts. The 0-20V supplies are protected

by the current limiting feature.If the output is

shorted the maximum current drawn will depend on

the limit control setting. The 5V supply features a

current foldback circuit. This circuit will limit the

output current to less than 1 amp. When the short

is removed, the output voltage will automatically

reset to 5V.

-4-

Safety Precautions

Certain safety procedures must be observed when

this power supply is used with external circuits that

are connected to AC power lines. There is always

some danger when working with electrical

equipment or circuits that operate at hazardous

voltages. You should thoroughly familiarize yourself

with the equipment before working on it. High

voltage may appear at unexpected points in

defective equipment.

The Elenco

power supplies are equipped with three

wire line cords which ground the chassis to power

line cord. DO NOT CUT OFF OR DISABLE THE

GROUND PLUG.

The power supply secondary circuits are isolated

from the 120V primary circuit via the power

transformer. When working with other equipment, this

may not always be the case. Always be familiar with

the equipment rating. Keep in mind that defective

equipment can have dangerous voltages at

unexpected points. CAUTION: When removing the

cover for fuse replacement, always disconnect the

power cord from the AC socket. Service repair should

only be done by qualified personnel who are

knowledgeable of electrical hazards.

Maintenance and Calibration

The Elenco®Models XP-660 and XP-760 have been

designed and manufactured to require no routine

maintenance. The circuits are protected by design

from external shorts or overloads. The following

information is provided in the event the supply requires

service or re-calibration.

Fixed 5VDC Regulation Calibration

1) Connect an accurate digital meter to the output

of the 5V supply.

2) Adjust the variable resistor VR101 to read

5.0VDC.

Variable 0-20VDC Regulator

Calibration

1) Connect an accurate digital meter to the output

of the 0-20V supply.

2) Set the voltage pot to maximum position.

3) Adjust the variable resistor VR302 of Power One

Supply for 20.0V. Adjust VR203 for Power Two

Supply.

Digital Meter Calibration

for Model XP-760

1) Note the small pot (R2) on the top of each

meter’s PC board. This is the GAIN pot which

controls the accuracy of the meter.

2) To set the accuracy of the meter you need

another very accurate digital meter. Connect

this meter to measure the voltage on the output

terminals of the supply under adjustment. Set

the output to 18VDC. Set the Volts/Amps switch

to Volts and adjust the GAIN pot for 18.0 on the

XP-760 meter.

3) To set the accuracy of the current measurement

connect a suitable load to the output and

connect the accurate digital meter to measure

the current in the load. Set the Volts/Amps

switch to Amps. Set the output current to 0.8

amps. Adjust VR304 (Power One Supply) or

VR204 (Power Two Supply) for a reading of 0.8

on the XP-760 meter.

-5-

Qty. Description Part #

Resistors

2 R105 .14Ω5% 5W 101405

2 R213, 313 .39Ω5% 2W 103911

2 R210, 310 68Ω5% 1/4W 126800

4R208, 209, 308, 309 200Ω5% 1/4W 132000

2 R211, 311 270Ω5% 1/4W 132700

4 R202, 203, 302, 303 470Ω5% 1/4W 134700

3 R101, 222, 322 1kΩ5% 1/4W 141000

4 R206, 214, 306, 314 1.2kΩ5% 1/4W 141200

2 R201, 301 1.2kΩ5% 1/2W 141201

2 R205, 305 2kΩ5% 1/4W 142000

2 R215, 315 3.3kΩ5% 1/4W 143300

1 R102 10kΩ5% 1/4W 151000

2 R217, R317 20kΩ1% 1/4W 152030

3 R103, 204, 304 22kΩ5% 1/4W 152200

1 R104 27kΩ5% 1/4W 152700

2 R216, 316 100kΩ5% 1/4W 161000

2 R218, 318 200ΩTrim Pot LD 191320

3 VR101, 202, 302 5kΩTrim Pot SU 191451

2VR201, 301 200ΩPot Panel 192320

2R203, 303 5kΩPot Panel 192450

Capacitors

3C104, 206, 306 .001µF Disc 231036

5 C103,201,202,301,302 100µF Lytic 25V 281045

2 C205, 305 100µF Lytic 35V 281046

3 C105, 210, 310 100µF Lytic 25V 281055

(axial)

2 C203, 303 2200µF Lytic 25V 292225

2 C204, 304 3300µF Lytic 50V 293347

2 C101, 102 4700µF Lytic 16V 294744

Semiconductors

1 BR1 Diode bridge 6A 310148

2 D211, 311 Diode 1N4001 314001

15 D101, 201-206, 209, Diode 1N4002 314002

D301-306, 309

4 D207, 208, 307, 308 Diode 1N4148 314148

2 D210, 310

Diode Zener 1N5240 10V

315240

4 Q201, 207, 301, 307

Transistor MPSA70

320070

1 Q101 Transistor TIP120 320120

3 Q102, 202, 302 Transistor 2N3055 323055

8 Q204-206, 208,

Transistor MPS5172

325172

Q304-306, 308

2Q203, 303

Transistor MPS6521

326521

1IC IC MC1723 331723

2LED201, 301 LED Red 350001

Parts List XP-660

Qty. Description Part #

Miscellaneous

1 Transformer 440660

1 PC Board 512010

1 Fuse 1.5A Slow Blow 520150

2 Switch slide DPDT 541111

1 Switch Illuminated 541204

2 Volt/Amp Meter 571020

1 Cover 611060

1 Chassis 611660

1 Heatsink 1 TO-3 615001

2 Heatsink Ham Rod 615100F

4 Knob 622009

1 Bushing Strain 3 wire 624003

3 Binding Post Black 625031

Binding Post Hex Nut 625031HN

Binding Post Lockwasher 625031LW

3 Binding Post Red 625032

1 Binding Post Green 625033

4 PCB Support 625001

2LED Lens 626014

6 Cable Ties 628982

1 Rivet .122 632211

4 Screw M3 x 0.5 x 5mm phillips, black 640300

1 Screw 6-32 x 1/2” 641665

4 Screw 8-32 x 3/8” 641840

4 Screw 6 x 3/8” Truss, AB 642652

8 Screw 6 x 3/8” AB 642660

1 Nut 6-32 Small 644601

4 Nut 8-32 644800

4 Nut 7mm 644101

3 Washer Flat #8 645008

4 Washer 8mm 645101

6 Washer 1/8” 645600

11 Lockwasher 5/16” 646101

1 Lockwasher #6 646600

5 Lockwasher #8 Ext. 646828

2 Lug ground 661001

4 Lug Solder #8 661002

1 Fuse Holder Lower Body 663005LB

1 Fuse Holder Nut 663005N

Fuse Holder Upper Body 663005UB

1 Fuse Holder Washer 663005W

1 IC Socket 14-Pin 664014

-6-

Schematic Diagram XP-660

-7-

Schematic Diagram XP-760

-8-

Qty. Description Part #

Resistors

2 R105 .14Ω5% 5W 101405

2 R213, 313 .39Ω5% 2W 103911

2 R210, 310 68Ω5% 1/4W 126800

2R207, 307 100Ω5% 7W 131017

4 R208, 209, 308, 309 200Ω5% 1/4W 132000

2 R211, 311 270Ω5% 1/4W 132700

4 R202, 203, 302, 303 470Ω5% 1/4W 134700

2 R219, 319 910Ω5% 1/4W 139100

3 R101, 222, 322 1kΩ5% 1/4W 141000

4 R206, 214, 306, 314 1.2kΩ5% 1/4W 141200

2 R201, 301 1.2kΩ5% 1/2W 141201

2 R307, 312 1.5kΩ5% 2W 141503

2 R205, 305 2kΩ5% 1/4W 142000

2 R215, 315 3.3kΩ5% 1/4W 143300

1 R102 10kΩ5% 1/4W 151000

3 R103, 204, 304 22kΩ5% 1/4W 152200

1 R104 27kΩ5% 1/4W 152700

2 R216, 316 100kΩ5% 1/4W 161000

2R217, 317 1MΩ5% 1/4W 171000

2VR201, 301 200ΩPot LD 191320

1 VR101 5kΩPot SU 191451

2 VR302, 303 10kΩPot SU 191516

2 VR204, 304 200Ω Pot Panel 192320

2 VR202, 203 10kΩ Pot Panel 192511

2 R220, 320

.01ΩShunt Wire

897120

Capacitors

3 C104, 206, 306 Disc .001µF Z5V 231036

2 C209, 309 Disc .1µF 251010

2 C207, 307

Lytic 4.7µF 50V Radial

264747

7 C103, 201, 202, 205 Lytic 100µF 25V 281045

C301, 302, 305

3 C105, 210, 310

Lytic 100µF 25V Axial

281055

2C208, 308 Lytic 220µF 25V 282245

2 C203, 303

Lytic 2200µF 25V

292225

2 C204, 304

Lytic 3300µF 50V

293347

2 C101, 102

Lytic 4700µF 16V

294744

Semiconductors

1 BR1

Diode bridge 6A

310148

17 D201-206, 209, 211 Diode 1N4001 314001

D301-306, 309, 311

4 D207, 208, 307, 308 Diode 1N4148 314148

2 D210, 310

Diode Zener 1N5240 10V

315240

4 D201, 207, 301, 307

Transistor MPSA70

320070

4 Q102, 202, 302

Transistor 2N3055

323055

8Q204, 206, 208,

Transistor MPS5172

325172

Q304-306, 308

1Q101 Trans. 6121/1061 326121

2Q203, 303 Trans. MPS6521 326521

Parts List XP-760

Qty. Description Part #

Semiconductors (Con’t)

1 IC101 MC1723 331723

2 IC201, 301 MC7805CT 337805

2 LED201, 301 LED Red 350001

Miscellaneous

2 LED Display 355614MI

1 Transformer 440660

1 PC Board 512010

1 Fuse 1.5A Slow Blow 520150

2 Switch 3PDT 541047

1 Switch Illuminated 541204

1 Cover 611060

1 Chassis 611760

1 Heat Sink 5V 615001S

2 Heat Sink Clip On 615005

2 Heat Sink 20V 615100F

4 Knob Push On 622009

1 Bushing 624003

4 PCB Support 625002

3 Binding Post Black 625031

7 Binding Post Lockwasher 625031LW

7 Binding Post Hex Nut 625031HN

3 Binding Post Red 625032

1 Binding Post Green 625033

2 LED Lens Red 626014

5Cable Tie 628982

7 Rivet .122 632211

2 Screw 6-32 x 1/2” 641665

4 Screw 8-32 x 3/8” 641840

4 Screw 6 x 3/8” Truss, AB 642652

8Screw 6 x 3/8” 642660

4Nut Hex 7mm 644101

1 Nut 6-32 644600

1 Nut 6-32 Small 644601

4 Nut 8-32 644800

3 Washer Flat #8 645008

4 Flat Washer Pot 8 x 14mm 645101

4 Washer Fiber #4 645404

7Flat Washer 1/4” OD 645600

1Lockwasher #6 646600

5Lockwasher #8 Ext. 646828

4Lockwasher Pot 3/8” 646900

2Lug Ground 661001

1Butt Connector 661100

4Feet 662001

1 Fuse Holder Lower Body 663005LB

1 Fuse Holder Nut 663005N

1 Fuse Holder Upper Body 663005UB

1 Fuse Holder Washer 663005W

1 Line Cord 3 Wire 862105

-9-

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