Agilent AN 372-1Power Supply Testing

Application Note

Agilent Technologies

An electronic load offers a broad

range of operating modes, providing

versatile loading configurations

needed for characterizing and

verifying dc power supply design

specifications.

Load

Abrupt Load Change

Standard Output Quantity

Load EffectOvershoot AmplitudeLoad

EffectRand

Load Effect

Load EffectTransientRecovery Time

Load EffectSettlingTime

Load Settling EffectTime

Time

I

T1

I

T1

As regulated-power supplytechnology evolves, testingmethods for design verificationand product function requiremore sophisticated electronicequipment. The different powersupply architectures and out-put combinations also dictatethe need for versatile testinstruments that can accommo-date a broad range of specifica-tions. As a result, one testingrequirement that has beengrowing in importance is themethod of loading the powersupply under test. The need fora higher degree of load controldue to test sophistication, suchas the need for computer pro-grammability, has increasedthe demand for electronic loadinstruments. The followingexamination of the most com-mon power supply architec-tures or topologies clearlyillustrates the growing need forhigher performance and versa-tility in electronic loads andpower supply test equipment.

An Overview of Power Supply TopologiesOf all the possible power supply topologies, linear andswitching regulation tech-niques are the most commondesign implementations. Linearpower supplies are typicallyused in R&D environments and in production test systemsbecause they provide high performance, low PARD (rippleand noise), excellent line andload regulation, and superiortransient recovery time specifi-cations. However, they are relatively inefficient when compared to switching powersupplies, and tend to be largeand heavy due to the heatsinks required to continuouslydissipate power from the seriestransistors and due to the magnetics used in this design.Typically, linear power sup-plies provide a most effectivesolution in lower power appli-cations, and are often used as subassemblies in various products.

Switching power suppliesaddress the disadvantages oflinear power supplies (namelythe low efficiency and relative-ly large size and weight), andare therefore a more effectiveand less costly solution forhigh power applications. Therelative disadvantages occur inthree areas when compared tolinear power supplies: slowertransient recovery time, higherPARD, and lower reliability.Switching power supplies areused in a wide variety of indus-tries and environments, andare commonly found as sub-assemblies in products such ascomputers, computer peripher-als, and copiers. Recent powersupply designs combine thebest features of switching andlinear topologies.

Below, Table 1 compares thetypical specifications for linearand switching topologies.

2

Table 1

Regulation Load Line Transient PARD EfficiencyTechnique Regulation Regulation Response

Switching 0.05 – 0.5% 0.05 – 0.5% 1 – 20 ms 5 – 20 mVrms 65 – 85%

20 – 150 mVp-p

Linear 0.005 – 0.1% 0.005 – 0.1% 20 – 200 µs 0.25 – 5 mVrms 30 – 50%

(Series Pass) 1.0 – 15 mVp-p

Introduction

Power supplies are used in awide variety of products andtest systems. As a result, thetests performed to determineoperating specifications candiffer from manufacturer tomanufacturer, or from end userto end user. For instance, thetests performed in an R&Denvironment are primarily forpower supply design verifica-tion. These tests require highperformance test equipmentand a high degree of manualcontrol for bench use. In contrast, power supply testingin production environmentsprimarily focus on overall function based on the specifi-cations determined during the products design phase.Automation is often essentialdue to large volume testing,which requires high testthroughput and test repeatabil-ity. Power supply test instru-ments must then be computerprogrammable. For both testenvironments, measurementsynchronization is necessary to perform some tests properlyand to obtain valid data. Inaddition, considerations suchas test set reliability, protec-tion of the power supply undertest, rack space, and total costof ownership may be of equalimportance to the power sup-ply test set designer. Properselection of testing instrumen-tation will provide the bestcombination of measurementsophistication and test setcomplexity.

Power Supply TestingInstrumentationThe power supply testing methods and configurationsdiscussed in this applicationnote are certainly not the onlymeans of obtaining the desiredmeasurements. However, cer-tain instruments are essentialto all tests, regardless of theimplementation. Some com-mercially available turnkeypower supply test systemsincorporate custom board levelinstrumentation and handwiring. However, power supplytest systems based on standardproducts afford greater benefits.These systems are more reliableand provide repeatable, highperformance measurementsbecause of their low noise environment. A system whichutilizes standard instrumenta-tion is modular, allows configu-ration flexibility based on per-formance needs, and is easierto upgrade. In addition, theservice, replacement, or cali-bration of separate instru-ments in the system can beperformed with minimal system down-time.

The tests covered in the follow-ing section are configured withstandard instrumentation: electronic loads, digital oscilloscopes, digital multime-ters, true rms voltmeters,wattmeters, and ac powersources.

Electronic loads can facilitatepower supply testing in severalways. They are typically pro-grammable, although mostrequire external DAC program-mers.

This capability enables finercontrol over loading valuesduring testing, and can providethe test set operator with valu-able status information. Theseloads are often designed withFETs, which provide increasedreliability over less sophisticatedsolutions consisting of relaysand resistors. Also, these prod-ucts offer a selection of operat-ing modes: constant current(CC), constant voltage (CV),and constant resistance (CR).The more sophisticated elec-tronic loads provide all threemodes in one product for optimum testing flexibility.They provide a versatile solution for testing both dcvoltage and current sources. A final advantage is providedby loads with readback over the bus. This can elimi-nate the need for digital multi-meters for voltage and currentmeasurements in some tests.As mentioned, there are vary-ing degrees of electronic loadsophistication. The AgilentElectronic Load family pro-vides all of the most sophisti-cated features and high levelperformance in one box.

3

An Overview of Power Supply Testing Needs

Several other instruments arerequired for power supply test-ing. The performance criteria(accuracy, resolution, stability,bandwidth, etc.) vary for eachtest. In general, the measure-ment capability of the instru-ments should ensure an errorno greater than 10% of themeasured specification. Table 2 on the next page pro-vides a guideline for instru-ment performance levels foreach test discussed in thisapplication note.

Load Transient Recovery TimeA constant voltage dc powersupply is designed with a feed-back loop which continuouslyacts to maintain the outputvoltage at a steady-state level.The feedback loop has a finitebandwidth, which limits theability of the power supply to respond to a change in theload current. If the time delaybetween the power supply feed-back loop input and output

approaches a critical value at its unity gain crossover, the power supply will becomeunstable and oscillate.Typically, this time delay is measured as an angular difference and is expressed asa degree of phase shift. The critical value is 180 degrees of phase shift between the loop input and output.

4

Power Supply Tests

Table 2 Load Transient Load Effect Current Limit PARD Efficiency and Start-UpRecovery Time Characterization Power Factor

Electronic Load t rise ≤15 µs 1% programming 1% programming 1% programming 1% programming 1% programmingaccuracy accuracy accuracy accuracy accuracy

Trigger output to CC or CR mode CR or CC mode CC or CR mode CC or CV mode CR modethe oscilloscope Low PARD

Digital tsample ≤100 µs N/A N/A tsample ≤25 µs N/A tsample ≤1 µs

Oscilloscopedc to 20 MHz Record length 1 Kminimum bandwidth samples minimum

Record length≥2 K samples

100 µ/Div (linears)1 mV/Div (switchers)

Digital N/A 5 1/2 Digits 5 1/2 Digits N/A N/A N/A

Multimeter ±0.005% accuracy ±0.005% accuracy

Wattmeter N/A N/A N/A N/A 1% accuracy with N/Acrest factors to10:1 in currentwaveforms

Regulated >1% regulation >1% regulation N/A >1% regulation >1% regulation >1% regulation

ac SourceAdjustable peak Adjustable peak Adjustable peak Adjustable peak Adjustable peakand frequency and frequency and frequency and frequency and frequency

Power factor Phase controlmeasurementcapability

RF rms N/A N/A N/A 100 µV Full scale N/A N/AVoltmeter dc to 20 MHz

minimum bandwidth

For a step change in load cur-rent, a marginally stable CVpower supply will have a ring-ing voltage output. This defeatsthe purpose of the power sup-ply’s regulation circuitry andcan be damaging to voltage-sensitive loads. An example ofa voltage sensitive load is thelogic circuitry in a computer.In this case, a computer manu-facturer that purchases powersupplies from an externalsource may consider verifying

the load transient recoveryspecification of the power sup-ply subassembly. This test canalso reveal critical manufactur-ing flaws that can cause insta-bility, such as a defective out-put filter capacitor or loosecapacitor connections.

Test Overview/Procedures CV Load Transient RecoveryTime is a dynamic measure-ment of the time required forthe output voltage of a CVpower supply to settle within a predefined settling band following a load currentinduced transient (see Figure 1).The response is typically measured in microsecondsor milliseconds, and varies invalue depending on the topologyof the power supply under test.

5

Figure 1. Load Transient Recovery TimeLoad transient recovery time measurements require an electronic load with a risetime and falltime atleast five times faster than the power supply under test.

ILOAD

T(ms)

T(ms)

TRISE TFALL

VOUT

SettlingBand

Load TransientRecovery Time

The electronic load used in thistest should have a risetime atleast five times faster than thepower supply under test, andshould be able to operate in CCmode (or CR mode) up to themaximum current rating of the powersupply. Measuring the loadtransient recovery time requiresthe load to have the capabilityto pulse between two differentvalues in CC or CR mode. Forcontinuous load transient test-ing, the repetition rate of thepulses should be slow enoughso that the power supply feedback loop can recover and stabilize after each applied transient.

Figure 2 shows a typical testsystem for making load tran-sient recovery time measure-ments. Measurement of Voutof the power supply can bemade with a digitizing oscillo-scope as the load input pulsesare applied. Synchronization of the measurement is crucialin obtaining proper measure-ments. Therefore, a commontrigger should start the elec-tronic load and oscilloscopemeasurements.

Load Effect (Load Regulation)Load Effect or Load Regulationis a static performancemeasurement which definesthe ability of a power supplyunder test to remain withinspecified output limits for apredetermined load change(see Figure 3). In a CV power

supply, the influenced quantityof interest is the steady-stateoutput current. In a CC powersupply, the influenced quantityis the steady-state output voltage. For single output CVpower supplies, voltage loadeffect is given for a load current change equal to thecurrent rating of the supply. A typical specification wouldbe stated in millivolts, or as a% of the rated output voltage.

For multiple output CV powersupplies, cross load effect isdetermined. This is an exten-sion of the load effect test for a single output power supply,and determines the ability of all outputs of a CV powersupply to remain within theirspecified voltage rating for aload current change on one

6

ac in PowerSupplyUnderTest

ElectronicLoad

Settling Band

Load EffectTransientRecovery Time

Load

Time (ms)

Time (ms)

Abrupt Load ChangeVOUT

T1

T1

ILOAD

VOUT

+

–

+

–

Scope

Figure 2. Load Transient Recovery Test Configuration and Vout Measurement Results for a CV Power Supply

output. Conversely, the abilityof one output to withstand theeffects of changes on all otheroutputs can be specified.

Test Overview/ProceduresFor a CV power supply, mea-surement of the output voltageand input voltage should bemade after the load is variedfrom the minimum to the fullcurrent rating of the powersupply under test (Figure 4).Measurement of the ac inputvoltage is necessary to ensurethat the output voltage changeis a result of only the loadchange, and not from a changein the ac input. To decrease thetest time when test throughputis a concern, a regulated acsource providing a predeter-mined ac input level and fre-quency can be utilized. Thiswill eliminate the need for theac input voltage measurement.

The output voltage should beallowed the specified settlingtime before measurements are taken. An electronic loadselected for this test must becapable of operating in CC orCR mode, and must have inputratings (voltage, current, andpower) sufficient to accommo-date the maximum ratings ofthe power supply under test.

Figure 4. Load Effect Testing ConfigurationA regulated ac source is used in this loadeffect testing configuration to maintain the ac input at a predetermined value. This willensure that the test results reflect changes in Vout only with respect to load currentchanges.

7

FullRating

LoadEffectBand

Time (ms)

Time (ms)T1

0

ILOAD

VOUT

∆VOUT

PowerSupplyUnderTest

ElectronicLoadILOAD

VOUT

+

–

+

–

DMMRegulatedac source

Figure 3. Load EffectFor a load current change equal to the fullcurrent rating of a CV power supply, theresulting change in Vout should not exceed the predetermined load effect band. Typicalspecifications for load effect range from 0.005to 0.5% of the maximum output voltage.

Current Limit CharacterizationCurrent limit measurementsdemonstrate the degree towhich a constant voltage powersupply limits its maximum out-put current to a preset value.This preset value can be fixedor variable throughout a speci-fied range. There are basicallythree types of current limitingdesign implementations:

1. Conventional current limiting power supplies

2. CV/CC mode power supplies3. Foldback current limiting

power supplies

Conventional current limitingpower supplies and CV/CCmode power supplies are very similar in function. Theseimplementations generally varyonly in the degree of regulationin the constant current operat-ing region (see Figure 5) and inthe ability of the user to adjustthe CC operating point (CV/CCpower supplies). A roundedcrossover knee and sloping current limit characteristicdenotes less precise currentregulation. In comparison, asharp knee and vertical cur-rent limit characteristic denotea higher degree of current reg-ulation. The foldback currentlimiting power supply employsa technique that enables boththe output voltage and currentto decrease simultaneously for load resistances below thecrossover value. The purposeof current limiting is to provide protection for the

power supply and the devicebeing powered (assuming thecurrent limit value is below the maximum current rating of the device).

Test Overview/ProceduresA measurement of the outputvoltage and current of thepower supply under test isrequired while decrementingthe electronic load resistance(or current in CC mode) bysteps from an initial value thatproduces the power supply’sfull rated voltage output (seeFigure 6). The voltage will

remain constant until the com-pliance current (output currentof the power supply) increasesto the preset current limit value.The crossover region or currentlimit has been reached whenthe rated output voltage of thepower supply changes by adegree greater than the loadregulation specification. At thecurrent limit knee, the compli-ance current and output voltagebehavior is determined by thetype of current limiting circuitimplemented in the power supply design (see Table 3).

8

Table 3. Typical Test Results of Standard Current Limiting Implementations

Current Limiting I Compliance (or Iout)Method at Minimum Load Resistance

CV/CC Remain constant (CC mode)Conventional Current Limiting Typically ≤ (105%) ImaxCurrent Foldback Typically foldback is ≤ (50%) Imax

Figure 5. Typical Operating Characteristics of Three Types of Current Limiting Power Supplies

LoadEffectBand

CV/C

urre

nt F

oldb

ack

R LOAD

= C

ross

over R

esist

ance

CV/Current Limit

CV/CC

VOUT

(50%)IMAX (100%)IMAX (105%)IMAX

IOUT

PARD (Periodic and Random Deviation)PARD (formerly known as rippleand noise) is the periodic andrandom deviation of the dcoutput voltage from its averagevalue, over a specified band-width, and with all other para-meters constant. It is represen-tative of all undesirable ac andnoise components that remainin the dc output voltage afterthe regulation and filtering circuitry (see Figure 7).

PARD is measured in rms or peak-to-peak values, and is typically specified over abandwidth range of 20 Hz to 20 MHz. Any deviation below20 Hz is included in a specifi-cation called output drift. In some applications, a lowoutput ripple specification is critical. An example wouldbe where the power supply is providing power to a high gain amplifier with inadequate ripple rejection for the applica-tion. In this case, a portion of

the power supply PARD wouldbe amplified along with thedesired signal. It is extremelyimportant that the PARD valuebe specified as a peak-to-peakvalue as well as an rms valuein this application. The peak-to-peak value would provideinformation on high magni-tude, short duration noisespikes while the rms valuewould be beneficial for deter-mination of the expected signal-to-noise ratio.

9

ac in PowerSupplyUnderTest

ElectronicLoadIOUT

VOUT

+

–

+

–

DMM

VOUT

RL = Open Circuit

RL = Short Circuit

RL = Load ResistanceRC = Crossover Resistance

R L >

R C

R L < R C

ILIMIT IOUT = ICOMPLIANCE

R L = R C

Pard

dcOUTPUT

VOUT

Time

Figure 6. Test Configuration and Results forCurrent Limit Characterization

Figure 7. PARD Consists of UndesirableSignals Superimposed on the dc Output of a Power Supply

Test Overview/ProceduresTo make PARD measurements,the electronic load used shouldoperate in CR mode for con-stant voltage and constant cur-rent power supplies. The loadshould also have lower PARDthan the power supply beingtested. This is especially impor-tant when measuring the PARDof linear power supplies, sincethey typically have excellentPARD specifications. A regulatedac source should be applied tothe input of the power supplyunder test. PARD measure-ments are made at the lowestand highest specified values ofac input to the power supply,and at the lowest and highestspecified source frequencies.

Proper connections betweenthe instruments and powersupply under test are essentialwhen making these measure-ments. Since PARD consists oflow level, broadband signals,major test set concerns areground loops, proper shielding,and impedance matching. Adigitizing oscilloscope can beused for peak-to-peak measure-ments (see Figure 8). High frequency noise spikes need to be measured, and thereforethe digitizing rate of the oscil-loscope must be at least fivetimes the maximum PARD frequency for proper sampling. To eliminate cable ringing andstanding waves, the typicalconfiguration includes coaxialcabling with 50 Ohm termina-

tions at both ends. Capacitorsshould be connected in serieswith the signal path to blockthe dc current.

A true rms RF voltmetershould be used to measure therms specification. Precautionssimilar to those for the peak-to-peak measurements shouldbe considered. For both mea-surements, care should betaken to prevent ground loops.Since most oscilloscopes and

true rms voltmeters haveground referenced inputs, testing a power supply withgrounded outputs may createsuch a ground loop. In thiscase, it may be necessary touse instruments with floating(differential amplifier) inputsto eliminate this problem.

10

Figure 8. PARD Testing Configuration

PowerSupplyUnderTest

ElectronicLoad

Scope

A. Peak-To-Peak PARD Measurements

B. rms PARD Measurements

+

–

+

–0.01 µF

0.01 µF

50 Ω

50 Ω

50 Ω

Regulatedac Source

PowerSupplyUnderTest

ElectronicLoad

RF Truerms

Voltmeter

+

–

+

–

0.01 µF

50 Ω

Regulatedac Source

The first set of PARD measure-ments should be made with theac source voltage and frequencyset at the lowest specified val-ues, and with the power supplyunder test at its minimum andthen maximum rated loadvalue. A second set of measure-ments should be made with theac source set at the highestspecified values of amplitudeand frequency, and with thepower supply minimally loadedand then maximally loaded. To test multiple output powersupplies, PARD measurementsfor each output should be madewith all other outputs set initially to minimum load, and then to maximum load.

EfficiencyThe efficiency of a power supply is simply the ratio of itstotal output power to its totalinput power. To obtain the trueinput power (rms voltage x in-phase rms current) of a typicalac-to-dc converting power supply, commercially availablewattmeters or ac sources canbe used to measure the neces-sary parameters. The instru-ment used to measure theinput current and voltage must be capable of samplingthe input signals at a rate fastenough to produce accuratemeasurements.

This test serves as a good indi-cation of the overall correctoperation of the power supplyunder test. If the measuredefficiency is outside the speci-fied range for the topology ofthe power supply, it is probablethat a design flaw or a manu-facturing problem exists thatshould be addressed.

Test Overview/ProceduresThe efficiency and power fac-tor of the power supply undertest should be measured understeady-state operation after theunit has been allowed to warmup. The electronic load can beoperated in CC mode (for CVpower supplies) and CV modefor (CC power supplies). Atleast two load settings shouldbe used, one of them being themaximum rated load for thepower supply under test (seeFigure 9 for test configuration).Some power supplies vary sub-stantially in efficiency andpower factor as a function ofloading. In this case, the loadshould be varied throughenough settings so that curvescan be plotted from the data toprovide the best representationof the test results.

Start-UpThe start-up delay of a powersupply is the amount of timebetween the application of acinput and the time at whichthe outputs are within theirregulation specification. Forswitching power supplies orpower supplies with currentlimiting, this time period isessential for proper sequencingof the output voltage at turn-on. In switching power supplydesigns, undesirable events canoccur at turn-on, causing cur-rent spikes which can destroythe switching transistors. Theproblem occurs when the feed-back loop tries to compensatefor the low output voltage thatit sees when the ac input is initially applied to the powersupply. This problem is usuallysolved by adding “soft-start”circuitry to limit the time theswitching transistors areturned on during the start-upsequence. This will limit thecurrent flow through themuntil the power supply hasreached stable operation.

11

ElectronicLoad

+

–

+

–

W

PowerSupplyUnderTest

Regulatedac SourceFigure 9. Configuration for Testing

Efficiency and Power Factor In this test configuration for measuring power supply efficiency and power factor, the variable ac source provides measurementsfor input power and power factor.

Another undesirable conditionthat can occur during powersupply start-up is voltage latch-up. In this case, the outputvoltage of a CV power supplywith current foldback fails toreach its full value at turn-onbecause the output currentattempts to immediately go toa high value. The protectiveresponse of the current fold-back circuitry of the powersupply can cause the outputvoltage to “latchup” at a pointwhere the current that must bedissipated can cause damage tothe power supply (see Figure10). It is, therefore, beneficialto measure the start-up delaytime and fully characterize it toensure safe operation at turn-on.

To fully characterize the start-up sequence of the power sup-ply under test, measurementsmust be made of the outputvoltage response to the instan-taneous application of the acinput (see Figure 11). A digitaloscilloscope should be used so that storage of the outputvalues can be accomplished for the measured start-up timeperiod. To accurately controlthe ac input frequency andamplitude to the power supplyunder test, a regulated ac sourceshould be used. Turn-on of theac source at selected 60 Hz (50 Hz) phases (zero-crossingand positive or negative peakvoltage, for example) is impor-tant for thorough characteriza-tion of start-up. The electronicload used in this test shouldoperate in CR mode.

12

Figure 10. Voltage Latch-Up Undesirable voltage latch-up and turn-on cancause the power supply to operate at currentlevels that may be damaging to internal circuitry.

Figure 11. Start-Up Delay Test Configurations and Results

VOUT

IOUT

RLOAD < RCROSSOVER

R CROSSOVER

VLATCH-UP

ILATCH-UP

Time (s)

Start-Up Delay

Time (s)

VDUT

Vac

PowerSupplyUnderTest

ElectronicLoadIOUT

VOUT

+

–

+

–

ScopeRegulatedac Source

An observation of any dcpower supply data sheet from a power supply manufacturerreveals a number of designspecifications that must be verified and tested. These testsoften differ in technique and in the test equipment that isused to measure the variousparameters. The commonaspect of all of these tests isthat a method of controlledloading of the power supplyoutputs is required, which ismost easily done with an electronic load. The list belowcontains a brief description of some of these tests.

DriftThis test involves the measure-ment of the periodic and random deviation of a powersupply’s output current or voltage (typically over 8 hours),typically covering a bandwidthfrom dc to 20 Hz. The electronicload used for this test shouldbe able to operate in CC or CV mode.

Test Equipment:• Computer

(for long-term testing)• Electronic Load• True rms Voltmeter

Source Effect (Line Regulation)A measurement of the changein the output voltage or cur-rent due to a change in thesource voltage magnitude. Theoutput of interest is measuredafter it settles within the regulation specifications.The electronic load used forthis test should be able tooperate in CC or CV mode.

Test Equipment:• Electronic Load• Regulated ac Source• Digital Multimeter• Precision Current Shunt

Short Circuit Output CurrentThis test measures the steady-state current of the power supply under test after the output terminals have beenshorted. The short circuit canbe provided by an electronicload operating in CR mode.

Test Equipment:• Electronic Load• Digital Multimeter• Precision Current Shunt

Overvoltage ShutdownTypically, a power supply isexpected to shut down if itsoutput voltage exceeds themaximum input voltage of itsintended load, the maximumoperating voltage of the powersupply, or a variably set voltagelimit. The overvoltage protec-tion test demonstrates the ability of the power supplyunder test to correctly respondto any of those conditions. An electronic load in CC modecan be used to test the outputvoltage response.

Test Equipment:• Electronic Load• Digital Multimeter

Programming Response TimeThis test measures the maxi-mum time required for the programmed output voltage or current of a power supply tochange from a specified initialvalue to a value within a speci-fied tolerance band of a newlyprogrammed value, followingthe onset of a step change inan analog programming signal,or the gating of a digital signal.An electronic load in CC, CR,or CV could be used in this test.

Test Equipment:• Computer• Electronic Load• Digital Multimeter• Precision Current Shunt

13

Other Power Supply Tests

The Agilent Electronic LoadFamily offers the power supplytester the solution for many of the tests that must be per-formed. For bench or systemapplications in large or smallscale testing environments,Agilent Electronic Loads pro-vide high quality and reliabilitywith superior performance,features, and documentation.This will make power supplytest system configuration easi-er, measurement proceduresrepeatable, and operating environments safer.

The Agilent 6060B 300 Wattand 6063B 240 V Single Inputdc Electronic Loads providemany features that are fullyprogrammable in CC, CV, or CR mode. For measurementsthat require step load changes,the 6060B and 6063B contain a transient generator that has a minimum risetime of 12 microseconds. This allowsfor load transient responsetesting of high performance linear (series regulated) powersupplies as well as switchingpower supplies. In addition,the duty cycle and frequency of the transient generator canbe fully controlled using thefront panel, or via program-ming through the built in GPIB.

Synchronizing the measuringinstruments in a power supplytest system is essential toretrieve valid test data. The6060B and 6063B can generatetriggers that can externallytrigger a DMM, digital oscillo-scope, or wattmeter to take a measurement as the loadchanges according to the testing goals. The 6060B and6063B can also change inresponse to external triggersfrom other test equipment.

For testing multiple outputpower supplies, Agilent offersthe N3300A 1800 Watt LoadMainframe. This product pro-vides an economical alternativeto the 6060B and 6063B forlarge scale testing environ-ments. It has six slots whichcan be user-configured up to1800 Watts with the AgilentElectronic Load Modules—the N3302A 150 Watt Module,the N3304A 300 Watt Module,the N3303A 240 Volt Module,the N3305A 500 Watt Module,and the N3306A 600 WattModule. The N3300A Seriesprovides all of the features ofthe 6060B and 6063B, plus it is faster, even more accurate,and has many new program-mable features to help make a manufacturing test systemfaster and more efficient.

The Electronic Load Familyprovides “One Box” solutionsfor system applications. Theseloads contain a DMM and pre-cision current shunt for volt-age, current, and power read-back via the built-in GPIB. Inaddition, Agilent ElectronicLoads contain a transient generator, provide status readback, and have voltage and current programmers thatreside in the box. This elimi-nates the need for externalDMMs in many power supplytest applications, and thereforesaves rack space and addition-al test system costs.

For reliable and safe operation,Agilent Electronic Loads offerfull protection against overvolt-age, overcurrent, overpower,overtemperature, and reversepolarity conditions. The relia-bility of Agilent ElectronicLoads are backed by a stan-dard three year warranty. Thereliability, performance, andfeatures of the 6060B, 6063Band N3300A Series, combinedwith competitive prices, makethese products an optimumsolution for power supply testing applications.

14

Power Supply Testing with Agilent Electronic Loads

For the latest information on Agilent’s dc electronic loads, visit our web site at:www.agilent.com/find/loads

By internet, phone, or fax, get assistance with all your test & measurement needs

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© Agilent Technologies, Inc. 2002 Printed in USA February 22, 2002 5952-4190

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