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Laura MarlinoOak RidgeNational Lab

Electrical Engineering Commun

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TABLE OF C ONTENTS

Laura Marlino 4DIRECTOR, VEHICLE ELECTRIFICATION PARTNERSHIPSInterview with Laura Marlino - Oak Ridge National Lab

Featured Products 8

Eliminating Unscheduled Hard Drive

DowntimeBY GARY DROSSEL WITH WESTERN DIGITAL

A System Perspective on Specifying 15Electronic Power SuppliesBY BOB STOWE WITH TRUE POWER RESEARCH

RTZ - Return to Zero Comic 18

10

Learn how to save data by predicting when a storage device will fail.

An introduction to the role of the electronic power supply, and how to match source

power with specific applications.



INTERVIEW

LauraMarlinoOakridge National Lab

Laura Marlino - Director, Vehicle Electrification Partnerships

How did you get into

electronics/engineering andwhen did you start?

I was originally attending theUniversity of Tennessee andstudying biology, of all things. Inmy junior year, it became clear tome that in order to do anything thatI really wanted to do in biology, Iwas going to need a PhD. I wasntsure if I was genuinely interestedenough in the subject to devotethe time needed to achieve that,

so I dropped out my junior yearand enlisted in the Air Force. Idecided that I wanted to travel,see the world, and do interestingthings, like live overseas fora while. Well, I never got theopportunity to live overseas;I was stationed state-side the whole time. But I was trained inelectronics in the Air Force, andthat is how I originally got into thisfield. When I got discharged, Ienrolled at the University of NewMexico to finish my bachelorsdegree. I had been stationed inDenver, Colorado and loved thearea, and wanted to go to theUniversity of Colorado. But ofcourse anywhere I went would beout of state, and the University ofColorado was too expensive. NewMexico, however, a borderingstate, was within the price range I

could afford with the GI bill.

I completed my bachelors atthe University of New Mexicoand went on from there to workat Teledyne Camera Systems in Acadia, California. I worked onanalog electronics for a digitalfilm conversion system, to storeHollywood films in a digital



INTERVIEW

format. At the time they had all ofthe movies on film, and after timethe film degrades in the vaultsso we had come up with an ideaof how to digitize it all. I worked

on doing that for a while anddecided that California was waytoo expensive at the time, givenmy salary. I was married andmy husband was having a hardtime finding a job. We decidedto move back to New Mexicowhere I got a job offer at Sperry, which later became HoneywellAerospace and Marine Systems.I spent about six years there anddecided that I wanted to go on formy masters degree.

I went back to the University ofTennessee for my masters, and when I graduated we were in arecession. Jobs werent plentiful,but I was able to get a position atOak Ridge National Laboratory,working in electronics. I workedthere for several years andthen left to go work for a smallstart-up design company doingsemiconductor design. Thecompany was sold to Flextronics,at which time I left and returnedto Oak Ridge National Labs andhave been here ever since, nownearing 20 years.

What type of work do youdo at Oak Ridge NationalLaboratory?

For the past seven years I have

been in hybrid electric vehicletechnologies. We are theDepartment of Energys (DOE)premier power electronics andelectric machines laboratory. Wedo novel, next generation designsfor the electronics and the motorsfor hybrid, electric, and fuel cellvehicles.

It is a national laboratory;is it government-relatedresearch?

We get the majority of our fundingfrom the Department of Energy. With the funding we are taskedwith looking at far reaching, longterm, new technologies that theOEMs or suppliers dont havethe resources or luxury to look at.They are all tasked with, What dowe do to get to the next model? We are looking at technologiesfor ten years down the line.

Can you tell us a little bit

about the research you aredoing?

Like I said, the majority ofour funding comes from theDepartment of Energy, but we also work with companiesdirectly. We do a lot of work withthe automotive OEMs and Tier 1

and 2 suppliers. Most of that workis on a proprietary level. The workthat we do for the Department ofEnergy is all open to the public,since is it funded by tax dollars.

Right now, I think the most excitingproject we are working on is onefor wireless power transfer forcharging the large battery packsin electric and plugin hybridvehicles. We got into this several years ago. It is sort of the buzzword now and everyone appearsto be jumping on the bandwagon,but ORNL started back when veryfew people had ever even thought

of it for vehicular applications. Inthe future, I feel that all electricand plugin hybrid cars will havethis technology in them.

With this technology, there isa receiving antenna on theunderside of your car. You will

Evanescent high power wireless transfer antennas(receiving antenna on left and transmitting antenna on right)



INTERVIEW

also have a transmitting antennain your garage that is built intothe concrete floor or part of amat you can throw down on thefloor. When you park your car in

the garage, you will not have toplug it in to charge the battery;it will receive its charge from thetransfer of power from the garagefloor up into the car.

Oak Ridge is now taking the nextstep forward, which is probably atechnology about 10 years downthe line, where we are going tobe embedding these coils inroadways. The DOEs mission

is to find ways to eliminate ourdependency on foreign oil. Todo that, we want to move towardthe electrification of vehicles. Weare working toward embeddingcharging coils in the road, andsimilar to a carpool lane, youwill have a charging lane. As youdrive your electric vehicle, youwill be picking up a charge. Youcan enter the freeway with notquite a full charge, you will pickup charge as you drive downthe lane, and you can exit with afully charged battery. The carscommunications system willcontrol whether the battery willreceive a charge and will even beable to talk to your utility companyto bill you for the electricity used.This will allow the downsizingof battery packs, making thecars lighter and more efficient,

leading to cost reductions ofthese vehicles, accelerating theminto the marketplace.

What type of system is beingused for this technology?

It is a resonant system, whichhas inherent voltage isolationfor safety. Since it operates at

resonance, it is going to draw very little power unless there isa matching antenna above thetransmitting antenna. We arecurrently operating our system

at about 20 kilohertz, thoughother companies are utilizingother frequencies. At Oak Ridge we are transmitting about fivekilowatts of power across a 200-250 millimeter gap between thetwo antennas with fairly highefficiencies.

Believe it or not, this technologyis moving so fast, there is nowa standards committee that has

been formed to establish wirelesscharging standards. I believe thetargeted efficiency is 90 percent,from the wall to the battery.

Have you been buildingprototypes?

Yes, we have. We have a movingprototype demonstrator unit andwe have been doing a lot of workon the antenna design this past

year. Our demonstration unit isused primarily for testing ourdifferent design options. We aremoving forward with plans tobuild our first in motion chargingprototype

Do you test the differencebetween the moving andstationary antennas?

Yes, our demonstration prototypehas been fabricated so wecan adjust alignment in threedimensions. One antenna is ona motorized track and we cantest field coupling between thetwo antennas as a function of theantennas alignment.

When moving one antenna overanother, our demonstration test

bed moves fairly slow. The stationwe have set up right now wouldrepresent stationary chargingor what we call opportunitycharging. Opportunity charging

would be at red lights, stop signs,bus stopsany spot where you would momentarily stop your vehicle. While you are sittingthere, waiting on traffic, your carwould pick up a charge.

Ideally, one of the first demos thatwe wanted to do was testing thesystem with shuttles at airports, which is a perfect fit for thistechnology. The vehicles routes

are well-defined as well as wherethey will park. The buses orshuttles can charge their batteries while waiting for customers toload, drive the customers to theirdestination, and then sit and waitfor additional customers whilegetting another charge.

What size of an antenna isbeing used?

The first one we began workingon takes up most of theundercarriage of the car. It isabout 36 x 40. One problem is, where you build the matchingantenna in your garage, or in aparking garage, will depend onknowing where the position ofthe antenna is in your car. Thelocation and size of the antennain the vehicle will need to bestandardized, so whether they

are pulling forward or backinginto the parking space, they canposition it correctly for maximumcoupling. The goal is to developan antenna that is about a 10 x 10square that will be located undera cars trunk. We are hoping tomove to that, but right now thedemo is just to test the science,



INTERVIEW

location, separations, and size.

How much does the bodyof the vehicle impact thetuning of the antenna?

There are shielding and EMIissues that are part of the ongoingwork.

What is your primary role inthis project?

I am the Director of VehicleElectrification Partnerships atOak Ridge National Laboratories.I oversee technical aspects ofprojects.

Are there any other

interesting projects that OakRidge is working on?

One big issue is that most of themotors in hybrid vehicles havebeen using rare earth magnetmaterials. These motors haveinternal or surface magnets.The biggest supplier of thesematerials is China. We get about

97 percent from them. There is abig push to change this becauseChina is so quickly becomingso technology driven that theyare starting to use more of thesematerials in-house. The cost ofthe materials has doubled in

the past year. The automobileindustry is all about cost. Wehave new projects focusing onmotor designs that do not usethese rare earth magnets. Rightnow these rare earth machineshave the highest power densityof any motor utilized for hybrids.The trick is to develop motorsthat do not use the rare earthmagnets but have the speed andtorque characteristics of rare

earth machines, as well as theirefficiency and power density. Wehave a number of projects goingon in this area.

We are also looking at alternativepermanent magnet motortechnologiesones that usedifferent types of magnets,

Matt Scudiere with evanescent high power wirelesstransfer antenna and initial instrumentation setup

not composed of rare earthmaterials. We are also lookingat electromagnets to generatethe electric fields. We are re-examining motor technologies

that have been used for otherapplications, dismissed by OEMsbecause the rare earth permanentmagnet machines perform so well. We are investigating waysto make these motors moreeffective. One technology isinduction machines. They arethe workhorse of the industry butthey are bigger and heavier thanthe rare earth motors. There maybe a case that can be made forinduction machines in all electricvehicles. We think that we have afew ideas to make the inductionmotors more efficient and we arepursuing this research area.

How hard is it for privateindustry to work withyou on developing newtechnologies?

We make it pretty easy for private

industry to work with us. Wehave meetings twice a year anda review in Washington whereindustry people can come in. Ifthey see technology that they areinterested in and want to pursue, we offer licensing agreementsso that we can promote gettingthese things out into the industry.That is ultimately our goal, to gettechnologies we develop out intocommercial use.

What challenges do youforesee in your industry?

The market acceptance due tounproven reliability and high cost

of electric vehicles.



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Gary DrosselDirector of Product Planning

Unscheduled Hard DriveEliminatingDowntime

No matter how dependable the storage device,sooner or later it wears out. Often, this occurs without warning after tens of thousands of write/erase

cycles. Unexpected drive failures can cause a complete

disruption of business, resulting in costly downtime and

a loss of data and customers. Until now, there has been

no definitive way to predict when a storage device will

fail.

Western Digital (WD) developed Self-Monitoring

Analysis and Reporting Technology (SiSMART) to help

embedded OEMs avoid this problem. By constantly

tracking a drives usage, SiSMART is able to report to

the user the exact amount of useable life left on the drive.Drive usage information can be requested by the host

at any time, and allows for an accurate prediction of

the drives life. This is especially important during the

qualification process.

Users can take advantage of this information to set

intervals for data collection, system maintenance, and

drive replacement. This can save embedded OEMs

upwards of hundreds of thousands of dollars a year in

lost data, system downtime, and maintenance.

WD SiliconDrive solid state storage technology isspecifically designed to meet the high-performance, high-

reliability, and multi-year product lifecycle requirements

of embedded OEMs in the netcom, military, industrial,

interactive kiosk, and medical markets. With its key focus

on decreasing the total cost of storage ownership over the

entire system deployment, WD created technologies to

minimize unscheduled downtime, maximize security for

the OEMs software IP, and provide real-time feedback

to enable the host system to manage its storage more

effectively.

Applications requiring advanced levels of reliability

and availability can employ WDs patented SiSMART

technology, which allows the host system to poll the

SiliconDrive and receive real-time feedback as to

the current usage. This technology allows the host to

calculate projected remaining useable life and model the

data transactions to ensure that the drive lasts throughout

the scheduled deployment.



TECHNICAL ARTICLE

SMART for Hard Drives

The Self-Monitoring Analysis and Reporting Technology

(SMART) function was introduced in the American

National Standards Institutes (ANSI) release of the

ATA-3 specification. Designed to act as an early warningsystem for pending problems with mechanical media

such as hard disk drives (HDD), SMART technology

works in conjunction with various sensors to monitor

the HDDs performance and determines whether or

not performance is normal. The host system software

can then poll the HDD using the SMART command and

generate a flag to alert the user to a potential problem.

The theory behind this command is that HDD failures

do not usually occur suddenly. Most failures result

from issues that generally occur over time, such as the

mechanics of the HDD spindle wearing out. The SMARTfeature was designed to monitor such issues, which

limits data loss and unscheduled system downtime.

SiSMART for Monitoring Solid State Drives

Solid State Drives (SSDs) such as WD SiliconDrives

do not have moving parts because they are solid state

storage solutions, so many of the parameters monitored

by the SMART function for HDDs are not applicable.

Solid state drives are preferred in environmentally

robust and high-duty cycle applications because they

do not mechanically wear out, but there is still a concernabout them degrading when exceeding the endurance

specification.

In much the same way a rechargeable battery loses

its charge after several cycles, nonvolatile solid state

storage components can lose their ability to retain data

after tens of thousands of write/erase cycles. This is

usually specified by component vendors as endurance.

When a block loses its ability to retain data or when data

errors occur that cannot be corrected by the drives

ECC algorithm, the block is swapped with one from

an available spare pool. When the spare blocks are

exhausted and another error occurs, the solid state drive

reaches critical failure and needs to be replaced. WD

saw the need for a monitoring method for solid state

drives and developed the SiSMART technology for SSDs.

Eliminating Unscheduled Downtime

There are two ways to eliminate unscheduled downtime:

Develop technologies to prevent the failures and

increase drive endurance.

Provide monitoring technology to warn the host

system of impending issues.

WD has engineered technologies that accomplish both

of the following:

PowerArmor eliminates drive corruption due to

power disturbances.

Solid state storage management algorithms such

as advanced ECC and wear-leveling over the entireSiliconDrive maximize the drive operating life and

extend system-level endurance.

SiliconDrive Solid-

StateStorag

eArray

HostSystemHostInte

rface

ApplicationSpecific

Technology

PowerArmor

Solid-State StorageManagement

Algorithms

SiSMART

Figure 1: Solid State Storage Technology



TECHNICAL ARTICLE

SiSMART

SiSMART technology performs an equally critical

function by acting as an early warning system for the host

and providing status on the percentage of drive usage

relative to the endurance specification. The host can thenset its threshold and schedule preventive maintenance

before the system goes down unexpectedly.

WD designed the SiSMART feature to monitor the write/

erase cycles of each block and the usage of spare blocks

in SiliconDrive products. Monitoring both is essential in

solid state drives that use wear-leveling to extend the life

and endurance specification of the drive.

Monitoring Spares Only

There is a significant consideration when only using

spares to determine remaining useable life in a solidstate drive that does wear-leveling. Defined as the ability

of the solid state drive to map logical block addresses to

different physical blocks, wear-leveling evenly wears all

of the blocks in the solid state drive if done properly, and

all of the blocks should wear out at roughly the same

time.

The solid state drive has 100 percent of its spares

available for most of the product life, and if a block

wears out, it is replaced by a spare. The drive ceases

to operate when the spares run out, so all of the spare

blocks are used up at roughly the same time if they all

wear out at roughly the same time (Figure 2).

SiSMART can provide the remaining number of spares

to the host system at any time. The host can then set its

threshold and take preventive action based on its own

established set of criteria.

Monitoring Data Transactions

for Each Block

Most system designers require a better feedback

methodology that yields meaningful data at any time

during system operation. It is useful to understand whenthe application has reached points such as 10%, 20%,

50%, and so on, that the host system can more accurately

flag any issues in advance of when they are likely to

occur (Figure 3).

PercentageofDriv

eUsed

Time

100

80

60

40

20

0

Figure 2: Percentage of Spares Remaining Over Time

PercentageofSparesRemaining

Time

100

80

60

40

20

0

Figure 3: Percentage of SiliconeDrive Used Over Time

SiSMART goes well beyond only monitoring spares. Toyield meaningful information at any point in time, SiSMART

tracks and tabulates write/erase transactions for each

block in the SiliconDrive. Based on this information and

whenever requested by the host, SiSMART can calculate

the percentage of drive life remaining. If the used

percentage goes beyond a certain comfort zone, the drive

can be replaced during the next scheduled maintenance

period. Eliminating unscheduled maintenance calls can

save embedded OEMs tens to hundreds of thousands of

dollars per year.

Modeling System Usage

Another benefit of the feedback provided by SiSMART

is the ability to perform storage usage modeling. It is

difficult for system designers to fully understand all data

transactions between the host and the driveespecially

if operating and file systems are used. SiSMART

eliminates this uncertainty.



TECHNICAL ARTICLE

Example

An OEM that manufactures enterprise edge routers uses

SiSMART to model the data storage requirements of its

system. The router is constantly logging data, and write/

erase endurance is a significant issue. To properly sizethe SiliconDrive, the company had to review the data

collection requirements. First, the company needed to

determine which parameters to monitor and how often

to log those parameters. Next, the company had to

determine how long they wanted to deploy this product

in the fieldin this case, five years.

The company had used flash cards in the past. The flash

cards had no feedback mechanism and the company

felt it would need to double the size of the card to give

them the required comfort level for meeting the five-

year deployment target. With SiSMART technology,the company deployed the capacity originally defined,

resulting in immediate cost savings.

The company tested the SiliconDrive in the field for six

months and then brought the system back to the test lab

and ran the SiSMART utility to determine drive usage.

It turned out that the drive was less than five percent

utilized, so the company not only felt comfortable with

its current application, it found a new data reporting

requirement and collected even more data, potentially

giving it a competitive advantage in its market. The

company could upgrade its system and still feel

confident in meeting the five-year target.

The SiSMART utility runs on Microsoft Windows XP/

Vista/7, Linux, or DOS-host systems. This executable

utility can also be integrated into applications directly.

Software libraries and source code is available under

NDA to those customers wanting to tailor this function to

their unique requirements.

Conclusion

Traditional solid state drives and flash cards did not

incorporate any type of feedback mechanism, and

consequently were allowed to operate until they

exceeded the endurance specification and failed. The

ability to monitor write/erase endurance is analogous to

monitoring fuel in an automobile. Having no monitoring

solution is like driving the car without a fuel gauge. The

system operates until it runs out of gas. Monitoring

spares only is like having a light that comes on just

before running out of gas. There may or may not be

enough time to get to a gas station before the system

fails. SiSMART monitoring technology is like having a

complete fuel gauge. Preventive maintenance (fillingup) in advance of a failure ensures the system operates

properly and does not experience any unscheduled

downtime.

About the Author

Gary Drossel is the director of product planning at

Western Digitals Solid State Storage Business Unit.

Prior to the March 2009 acquisition of SiliconSystems

by Western Digital, Drossel was the vice president

of product planning at SiliconSystems. Previously,

Drossel has also held various marketing, sales and fieldengineering management positions with SimpleTech,

Motorola Computer Groups Pro-Log division, and the

industrial automation group of Parker Hannifin. Drossel

graduated with a B.S. degree in Electrical and Computer

Engineering from the University of Wisconsin.

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14/19

2.5A Regulator with Integrated High-Side MOSFET for

Synchronous Buck or Boost Buck Converter

ISL85402The ISL85402 is a synchronous buck controller with a 125m

high-side MOSFET and low-side driver integrated. The ISL85402

supports a wide input voltage range from 3V to 36V. Regarding the

output current capability from the thermal perspective, the

ISL85402 can typically support continuous load of 2.5A under

conditions of 5V VOUT, VIN range of 8V to 30V, 500kHz, +85C

ambient temperature with still air. For any specific application, the

actual maximum output current depends upon the die temperature

not exceeding +125C with the power dissipated in the IC, which is

related to input voltage, output voltage, duty cycle, switching

frequency, board layout and ambient temperature, etc. Refer to

Output Current on page 13 for more details.

The ISL85402 has flexible selection of operation modes of

forced PWM mode and PFM mode. In PFM mode, thequiescent input current is as low as 180A (AUXVCC connected

to VOUT). The load boundary between PFM and PWM can be

programmed to cover wide applications.

The low-side driver can be either used to drive an external low-side

MOSFET for a synchronous buck, or left unused for a standard

non-synchronous buck. The low-side driver can also be used to

drive a boost converter as a pre-regulator followed by a buck

controlled by the same IC, which greatly expands the operating

input voltage range down to 3V or lower (Refer to Typical

Application Schematic III - Boost Buck Converter on page 5).

The ISL85402 offers the most robust current protections. It

uses peak current mode control with cycle-by-cycle current

limiting. It is implemented with frequency foldback under

current limit condition; besides that, the hiccup overcurrent

mode is also implemented to guarantee reliable operations

under harsh short conditions.

The ISL85402 has comprehensive protections against various faults

including overvoltage and over-temperature protections, etc.

Features Ultra Wide Input Voltage Range 3V to 36V

Optional Mode Operation

- Forced PWM Mode

- Selectable PFM with Programmable PFM/PWM Boundary

300A IC Quiescent Current (PFM, No Load); 180A Input

Quiescent Current (PFM, No Load, VOUT Connected to

AUXVCC)

Less than 3A Standby Input Current (IC Disabled)

Operational Topologies

- Synchronous Buck

- Non-Synchronous Buck

- Two-Stage Boost Buck

Programmable Frequency from 200kHz to 2.2MHz and

Frequency Synchronization Capability

1% Tight Voltage Regulation Accuracy

Reliable Overcurrent Protection

- Temperature Compensated Current Sense

- Cycle-by-Cycle Current Limiting with Frequency Foldback

- Hiccup Mode for Worst Case Short Condition

20 Ld 4x4 QFN Package

Pb-Free (RoHS Compliant)

Applications

General Purpose 24V Bus Power

Battery Power

Point of Load

Embedded Processor and I/O Supplies

FIGURE 1. TYPICAL APPLICATION FIGURE 2. EFFICIENCY, SYNCHRONOUS BUCK, PFM MODE,

VOUT 5V, TA = +25C

VOUTISL85402VCC

SGND

MODE

BOOT

VIN

PHASE

PGND

FS

EXT_BOOST

EN

FB

COMP

VIN

AUXVCC

LGATE

ILIMIT

SS

SYNC

PGOOD

50

55

60

65

70

75

80

85

90

95

100

0.1m 1m 10m 100m 1.0 2.5

EFFICIENCY

(%)

LOAD CURRENT (A)

6V VIN

12V VIN

24V VIN

36V VIN

September 29, 2011

FN7640.0

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2011

All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

Get the Datasheet and Order Samples

http://www.intersil.com
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Bob StowePower Supply Design Consultant

A System Perspective

on Specifying ElectronicPower Supplies

Power Supplies Match Load to Source

The world we live in provides us with commonly

available sources of electrical power as well asendless types of sources yet to be discovered ordeveloped. We also have countless applicationsfor this power.

However, the typical case is that the electrical powersource is not in the adequate form to energizespecific applications. There must be a matchingprocess that changes the form of source powerto useable power for applications. This matchingprocess is the role of the electronic power supply.

Notice that the phrase electronic power supplyis a misnomer. Electronic power supplies do notcreate power; rather, they simply transform theavailable power from a source to a useful form for

your application.

Figure 1 illustrates the interactions between thesource and the power supply and the power supplyand the load.

A Timely System-LevelApproach Needed

Approaching power supply applicationspecification, and design from a system-levelperspective is of paramount importance for thesuccess of projects. The system includes the source,the load, and the environment around the powersupply. Additionally, the system power supply mustbe treated with equal weight as other aspects of thesystem design.

Yes, the source and load characteristics must beknown before the power supply requirements aredetermined. However, the time to evaluate power

supply requirements is right after the initial loadand source characteristics are known. It is quitecommon that a matching power supply designis not feasible given the initial load and sourcecharacteristic determination. In this case, either theload or source characteristics need to be adjustedbefore proceeding further with the system design.Otherwise, the result will be a failed project ora project with tremendous cost overruns. This



TECHNICAL ARTICLE

occurrence is a very common mistake that is easilyprevented.

A Major Cause of Project Failures

Perhaps a reason for the common occurrence ofproject failure is a perception that electronic powersupplies are the proverbial black boxes, capable ofperfectly supplying power to the load. They are notperfect black boxes, and failure to consider theirlimitations and adverse behavior can be disastrousto a project program.

It is well known that the cost to make designchanges increases exponentially with time

in the development cycle. This exponentialcharacteristic occurs due to the work that must bedone to re-document, re-test, and re-work designsand existing products. Problems not found untillate in the development cycle can prove to havedisastrous cost consequences. Dont be caughtthinking that the power supply design can wait tillthe end! Design power supplies in your system atthe right time.

Power Supplies are Complex

Electronic power supplies, especially switch-

mode type, have very complex mechanisms andrequire a diverse skill set to design. The skill setincludes not just knowledge of high-frequency withhigh-power analog electronics, but also adequateknowledge of mechanical packaging and heattransfer concepts.

Many vendors have done a good job of simplifyingswitching power supplies for general purposeapplications. However, a system knowledge ofthe source and the load are still important as well

as the characteristics and limitations of the powersupply itself.

Upcoming Topics

This series of articles about specifying powersupplies from a system perspective will coverin more detail various aspects of system-levelconcerns. Following are some of these aspects tobe covered:

Load Characterization

Source Characterization

Efficiency

Thermal Environment

Packaging

Watch for the upcoming articles on A SystemPerspective on Specifying Electronic PowerSupplies.

About the Author

Bob Stowe has over 21 years of experience in various disciplines related to electronic energyconversion, possesses a masters degree in powerelectronics, and is a member of IEEE in goodstanding. He also has obtained his certification inpower electronics from the University of Colorado(COPEC). Additionally, he graduated from theUnited States Naval Academy in 1984 with abachelors degree in electrical engineering, andserved for five subsequent years as a United StatesNaval Officer. As a former military officer, he isfamiliar with military project requirements. Bob now

works for True Power Research as a Power SupplyDesign consultant.

Solid lines represent a direct influence.Dashed lines represent indirect influence through the power supply.

Desired Flow of Power

Source ofPower

Power Supply(Not a perfect black box)

Load

Figure 1: Power Supply Interactions with the source and the load.


17/19

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RETURN TO ZERO


19/19

RETURN TO ZERO

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