technology first - alternative energy - en

8/2/2019 Technology First - Alternative Energy - En

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Alternative

Energy

On the horizon:

LIVEWIRE | MARKETWATCH | EMBEDDED CORNER

WORLDVIEW | ROADTEST | TECHTRENDS | GET TECH

Solar EnErgySolar CEllS

Solar PanElSPhotovoltaiC arrayS

MCUSMPUS

MoSFEtS

Wind PoWErigBt

BattEry/ChargE ControllErSCaPaCitorS

invErtErSConnECtorS

grEEn EnErgyindUStrial

oFF grid PoWEr SyStEMSaPPlianCES

PoWEr ManagEMEnt iCS

FUEl CEllSthryStorS

BridgE rECtiFiErS

EnErgy EFFiCiEnCyoPtiCal SEnSorS

lEdS

rEnEWaBlEEnErgyPFCControllErShEat SinkS

A Premier Farnell Company DESIGN WITH THE BEST

JOURNAL


2/44Discrete Semiconductors and Passive ComponentsOne of the Worlds Largest Manufacturers of

www.vishay.com

Discrete Semiconductors

Number 1 worldwide in low-voltage

power MOSFETs

Number 1 worldwide in rectifiers

Number 1 worldwide in glass diodes

Number 1 worldwide in infrared components

...and others

Passive Components

Number 1 worldwide in wirewound and

other power resistors

Number 1 worldwide in foil, SMD thin film,

and leaded film resistors Number 1 worldwide in wet tantalum capacitors

Number 1 worldwide in strain gage sensors

and load cells

...and others

We Are TheMarket Leader In


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There are many viable reasons for considering an alternative energy solution to power new designs,especially for those with ultra-low power requirements. Battery regulations, lower total cost ofownership, environmental benets, and ease of implementation are just some of the many benets thatalternative energy sources can bring.

It is easy to think of all alternative energy as giant wind farms or hydro plants, but many alternativeenergy sources can be as simple as a single solar cell powering a remote sensor and wireless transmitter.

As well as solar power, piezoelectric and thermoelectric generators can harvest vibration and thermalenergy to generate enough electricity to power a simple circuit.

For alternative power sources to be viable, efciency is key. The overall amount of energy generated canbe quite small, and the generation, transformation, storage, conversion and distribution phases of thecircuit need to have as few losses as possible to ensure enough power is available to drive the load.

This journal will look at the design and implementation of these systems, along with the latest powerchain innovations that have opened new applications for alternative energy. We also include somepractical examples of these circuits in operation. The journal will contain articles from both ourindustry leading range of suppliers and our in-house technical teams. We also have the regular featuresto keep you up to date with the current trends in the industry and the latest news from Premier Farnellcompanies.

As usual we welcome all feedback. Any comments and suggestions can be sent [email protected]

David ShenGlobal Head, Technical Marketing, Premier Farnell

Alternative Energy

THE ISSUE

Printed on papers produced from renewable resourcewood (sustainable forests). Please recycle after use.

Making a Dierence...

3


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isntlike

our playground

Needless to say, our people arent afraid to use a calculator.

In fact, we employ over 3,600 PhDs, drawn from every quarter

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7 LiveWireA quick look at energy trends and

developments from around the world.

9 MarketWatchThe photovoltaic industry has had its ups& downs recently. Whats ahead for PV?

11 LegislationFind out how to design for the

Energy using Products legislation.

12 RoadTestSign up to test the latest development tools

from Texas Instruments and Microchip.

14 Alternative EnergyAlternative energy sources are the future of

energy generation. Articles in this issues focus

will look at the design and implementation

of new energy systems, along with the latest

power chain innovations that have paved the

way for new energy applications.

32 Embedded CornerFind out what goes into the redesign

of an aging electronic product, and howenergy harvesting provides energy for

small scale needs.

38 Premier Farnell News Adopting environmental and social

policies is good business as well as

good corporate citizenship.

40 TechTrendsShowcasing some of the latest products

addressing alternative energy applications.

42 Get Tech See what questions engineers are asking

about monolithic devices, single mode

and multimode ber and more.

Editorial Staff|Editorial dirEctor Jamie Furness|Editor-in-chiEf alistairWinning|Editor Janice Fleisher|tEchnical Editor randall restle|crEativE dirEctor david

macaluso|art dirEctor gamilah smith|Publishing ManagEr Judy medhurst|PrograM

ManagEr melissa tucker|

CONTENTS

5


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Global newsUK research onenvironmental targetsLondon, UK Researchcommissioned by WRAP (Waste& Resources Action Program)into how resource efciency canhelp the UK meet climate changetargets, shows that making betteruse of natural resources couldcontribute as much as 10% of thetarget reduction in UK domesticgreenhouse gas (GHG) emissions by2020, with no impacton GDP.

Budget for energyprojects announcedWashington DC, US The DOEannounced $155 million funding tosupport 41 projects, with a further$634 million in private support.The money will be invested incombined heat and power, districtenergy and waste energy recoverysystems, and energy efciencyinitiatives in hospitals, utilitiesand industrial facilities.

Telenor Pakistan

opts for solar powerEspoo, Finland Telenor Pakistansigned a contract with Nokia SiemensNetworks to build off-grid sites usingenergy harvested from the sun. NokiaSiemens Networks will use solarenergy to power base station sites inrural and remote areas.

Global environmentalsustainability centerSingapore, The National ResearchFoundation (NRF) has partneredwith the Swiss Federal Instituteof Technology to set up a global

environmental sustainability centerin Singapore. NRF has also starteda fourth research program withthe Massachusetts Institute ofTechnology (MIT).

Xcel Energy to add moresolar power in ColoradoDenver, US Xcel Energy added over257MW solar power to its plan formeeting Colorados renewable energystandard. The standard requires 20%energy to come from renewableresources by 2020. Xcels plan also

includes about 700MW of new windpower and about 350MW of utilityscale solar power plants.

Swedish companies eye cleantechnologies in VietnamHanoi, Vietnam Swedish companiesare seeking opportunities to investin energy efciency projects inVietnam. ABB, Ericsson, and MuntersGroups and others are searchingfor partners for projects involvingenergy efciency, CDM andtechnology transfer.

Green Technology agreementfor LA port complexSan Pedro, US Technoplexand Proteus EnvironmentalTechnologies have announced astrategic partnership to bring greentechnology practices into port,maritime and the goods movementcommunity. The LA port complex hasimplemented green policy changes

to reduce pollution and increaserenewable energy supply.

New clean energy plantLondon, UK The UK governmenthas given the all-clear for a new plantin Peterborough, which will convertwaste glass, plastic and metal intoclean energy. The waste and biomass-fuelled power station could help theregion to get more than half waytowards its carbon reduction target ofa 17% drop by 2020, as it will deliver a10% reduction by itself.

Renewable energy couldcreate 1.9 million US jobsWashington DC, US The studyClean Energy & Climate Policyfor U.S. Growth and Job Creationestimates that as many as 1.9 millionnew jobs could be created across theUnited States within renewable energy.Annual household income couldincrease by US$1,175 per year andGross Domestic Product could increaseUS$111 billion by 2020.

600MW Texas wind farmWashington DC, US The U.S.Renewable Energy Group (US-REG)and Cielo Wind Power LP have enteredinto a joint venture frameworkagreement with Chinas ShenyangPower Group, which sets forth plansto develop a 600MW wind farm that

covers approximately 36,000 acres inTexas. The project is estimated to havea total cost of approximately $1.5b.

Biofuel for commercial ightsNew Delhi, India The InternationalAir Transport Association (IATA)will attempt to nd a biofuel by 2010for its commercial ights. Biofuelsfor commercial ights and it wouldbe certied by the end of the year.Certication may do away withsome investment uncertaintiesplugging the use of high quality

biofuels in aviation.n

LONDON

WASHINGTON

ESPOO

SINGAPORE

DENVER

HANOI

SAN PEDRO

NEW DELHI

7

LIVEWIRE


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After recording 30 years of continuousgrowth, the photo-voltaic (PV ) industrywalked into a perfect storm in 2009,experiencing its rst major downturn. Aconuence of forces contributed to theabrupt shift in direction, as the industrycame off a banner year in 2008. First,there was a great deal of excess capacitythat had been baked into the supplychain in early 2008, when a key rawmaterial (polysilicon) had been in short

supply and ASPs for PV cells and moduleshad been soaring. As nancing dried upand the worldwide economy sputteredin the latter part of the year, the shortageof polysilicon quickly disappearedand spot prices collapsed to less than aquarter of what they had been at theirpeak. Additionally, local legislation inthe Spanish market effectively cappeddomestic PV spending, a move thatquickly rippled through the worldwideindustry, given that Spain represented a42% share of global PV system sales atthe time.

The predicted outcome according toGartner Research published in October,2009, is that overall 2009 solar cellrevenue is expected to decrease by morethan 50%, down from a record $16.3Bin 2008. While the market continues toevolve, cell and module prices remainwell below 2008 levels and may not rmup until 2011 or beyond. But despite a

very rough year, the overall prognosis forthe industry is far from gloom and doom.

Gartner believes the major drivers for thesolar market are beginning to align onceagain. Alphonso Velosa, Research Directorfor Semiconductors at Gartner, notes thateven though this is a phenomenallyhorrible market for vendors right now,it has turned into a fantastic opportunityfor end users. In fact, the denegradedASPs for PV modules has made solarmuch more competitive, relative tocompeting energy alternatives, at a timewhen improvements in supporting

technologies are enhancing the efciencyand output of solar module arrays.Meanwhile, US and Chinese stimuluspackages include signicant funding forthe development of solar alternatives, andmore US federal and state programs aregreasing the wheel for solar growth. Thechart below forecasts worldwide modulerevenue growth through 2013 under

different scenarios: recession, conservativeand accelerated growth.

Indeed, many of the leading componentmanufacturers have aligned their strategicfocus to capitalize on the long-termpotential of solar energy. Last March,National Semiconductor announced theacquisition of Act Solar Inc., a privatelyheld solar energy company that willexpand Nationals existing portfolio ofpower optimization technologies. MikePolacek, VP of Nationals Key MarketSegments commented ....with Act Solar,we can further improve the performance

and efciency of solar systems, at the sametime providing monitoring capabilitiesnot available before. In October2009, Tyco Electronics announced thelaunch of its new micro website (www.tycoelectronics.com/solar) dedicated to thephotovoltaic industry; the site is backedby Tycos own research and engineeringcapabilities, and features a broad array of

information, products, and solutions forthe PV industry.

While the PV industry is expectedto continue its bumpy ride for thenext few years, most insiders do see abright light at the end of the tunnel.The 2009 PV industry downturncontained some valuable lessons forprivate industry and governmentsalike about the need to more carefullymaintain a balanced supply chainacross a globally-subsidized industry.Manufacturing costs seem to be comingdown to a level where a reasonablemargin can be maintained, andsupporting technologies are bolsteringperformance, while reducing long-termcost. Without a doubt, the dynamicPV industry will have its share of ups

and downs in the next 30 years of itsevolution, but its long-term prognosisremains very solid.n

The PV orecast:

a partly sunny warm-upB Jck Mu, Mke resech Me, newk

MARKETWATCH

Source: Navigant Consulting, August 2009

9

MARKETWATCH


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The next step in mains LED lighting

For AC mains powered LED lamps, NXPs driver and controller ICs are the

next step in performance and reliability. Offering the only LED drivers available

that match LED lifetimes, dimming to below 1%, support for both flyback and

buck configuration, they are the solution of choice for this fast emerging market.

As incandescent bulbs are phased out, NXP has a complete portfolio of

proven lighting solutions (CFL, LED, HID, TL) to help you take advantage of

this lighting revolution. So act now, and discover all the benefits at

www.nxp.com/ad/experience_lighting

Experience high-performance analog

Join theLighting Revolution


11/44

The focus is clearly on the design phaseof the product, since it is considered thatthis is the determining stage affectingthe resources used in a product. Thedirective does not apply to means

of transport, but apart from this, thescope is deliberately broad, covering inprinciple, any product which when inuse depends on, generates, transfers ormeasures energy (electricity, fossil fuelor renewables).

EuP legislation promises to have asignicant impact on the design phaseof a wide variety of electrical products.Obligations on manufacturers will resultfrom a series of specic ImplementingMeasures, the rst of which was adoptedin January 2009.

The criteria required before a productcan be considered for assessment is thatit must sell more than 200,000 unitsper year in the European Union, havea signicant environmental impactand present considerable potential forimprovement. The latter is important asthe target is for a 20% improvement inenergy efciency by 2020.

Implementing Measures must not have asignicant negative impact on a productsprice or performance or impact thecompetitiveness of EU industry. DuringPhase 1, studies were commissioned on20 broad product categories rangingfrom water heaters, televisions, laundry

dryers, vacuum cleaners and lightingto imaging equipment, such as copiers,faxes, printers, scanners and personalcomputers.

Beyond that, a further 17 categories havebeen highlighted from ovens and hobs,machine tools, DVD / video players,and air-conditioning equipment totransformers, heating and networkingequipment. Among the rst obligationsto come into force were energy efciencyimprovements, covering standby andoff-mode losses, simple converter boxesfor digital television, external powersupplies and ofce, street anddomestic lighting.

More recently, measures were placed onelectric motors, circulators in buildings,

domestic refrigerators as well as freezersand consumer electronics, such astelevisions. Implementing Measureslook to reduce energy in use, cut standbylosses, limit the use of toxic substancessuch as lower mercury content inlighting, promote clear energy labelling,as well as measures covering the furtherimpact on design and waste.

Products that fall within scope aresubject to conformity assessment. Thismeans that CE marking applies to theproduct and cannot be afxed until theeco-design measures, dened by theregulation, have been implementedand documented in the technical le

of the product. The legislation shallbe consistent in all EU Member States,which is known as a single marketdirective.

Moving forward, the EuropeanParliament has now adopted theEuropean Commissions proposal towiden the scope of the directive toinclude energy-related products. Untilnow, the Energy using Products Directivewas limited to products that consumeenergy during use such as boilers,computers, televisions, industrial fansand light bulbs.

Many more products have an indirectimpact on the energy in use, such aswatertaps and showerheads, doubleglazing windows and insulating

material. Improvement in their designcould clearly result in the signicantenergy savings. For example, watersaving taps and shower heads reducewater consumption and therefore theamount of energy used to heat water.

Under the EuP Directive, studies hadto set requirements for individualproducts where, in fact, it is theperformance of the whole system thatoften needs to be optimized, not justa single component or products. Thenew directive will repeal the existing2005/32/EC, which is often quoted bythe European Commission as a modelof better regulation.n

How to design or

Energy usingProducts (EuP)LegislationB g nes, les & Eme affs, Peme Fe

The European Unions Directive 2005/32/

EC, Energy using Products, entered into

force on August 11, 2007. The main aim

of the legislation is to monitor energy

efciency throughout the life cycle of a

product, from the mining of raw material

through recycling at end-of-life.

LEGISLATION

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TMS320VC5505 eZdsp USB stickFor many designers, the cost and time to set up development toolsis a major barrier when evaluating a new DSP platform. To lowerthis barrier, Texas Instruments TMS320VC5505 eZdsp USB stickdevelopment tool drops the cost of a full-featured emulator andintegrated development platform. The kit enables rapid creation

of DSP applications including portable audio players, voicerecorders, IP phones, portable medical devices, biometric USB keys,software dened radios (SDRs), hands-free headsets and meteringapplications.

At an extremely low price point, it makes development accessibleto existing and potential customers, hobbyists, researchers andstudents.

Comparable to the size of a stick of gum, the C5505 eZdsp sticksimplies development by providing integrated features, suchas an on-board XDS100 emulator and on-board audio codec andconnectors. Taking advantage of the energy efcient C5505 DSP,the eZdsp requires no other components or cables, allowing theentire development tool to be powered by the USB port. Designers

simply plug into the USB port of any laptop or workstation forhassle-free development and a simple out-of-the-box experience.

C5505 eZdsp USB stick development tool key features and benets:

Based on the C5505 processor, the industrys lowest power16-bit

DSP, with active power consuming less than 0.15mW/MHz andstandby power less than 0.15mW

Integrated XDS100 emulator provides complete debugcapabilities and visibility inside the processor for algorithmoptimization and benchmarking

On-board audio codec and connectors allow developers toevaluate many features of the C5505 processor and quicklyoptimize complex DSP algorithms in terms of performance andpower consumption across a variety of design scenarios

Extension connector allows developers to design and directlyconnect to daughter cards suitable for their application

Unique form factor plugs into any laptop or workstation,conserving test bench space

Simplies development tools setup by eliminating power andinterface cables

Includes the complete Code Composer Studio version 4 IDE

Stereo line in and headphone out connectors, making itpossible to evaluate many DSP algorithms and listen to them

Users can easily migrate to TIs C5505 evaluation module thatoffers additional extensive evaluation options

The feature-rich C5505 eZdsp USB stick development includesa full XDS100 emulator and a target version of the industry-

leading CCStudio v.4. The C5000 platform is supportedby TIs extensive Developer Network, as

well as a complete chip support library,comprehensive application notes,

reference designs, applicationguides, videos and online

communities.

Sign upto testthe latestdevicesWelcome again to RoadTest, your chance to receive

a cutting-edge development tool to test. In this issue,

we have two development kits to give away, both

from industry-leading companies. Texas Instruments

has given us 10 TMS320VC5505 eZdsp USB stick

development tools, and we also have 10 Microchip

PICkit 2 Development tools bundled with the Flowcode

3 Graphical programming language.

It is also worth registering at

www.element-14.com and joining the

RoadTest group. Being a member

of this group will make it easy to

enter this giveaway and also enter

other offers that are not included

in this journal. There will also be

space for recipients to post

their own reviews, and for

manufacturers and other

users of the product to

offer opinions. You can nd

the group at www.element-14.com/

community/groups/roadtest.

ROADTEST

12

DESIGN WITH THE BEST at www.farnell.com


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To have a chance of testing these products, write to me

at [email protected] with either eZdsp or PicKit

in the subject title, or join the element14 RoadTest

group, and accept the invitation for the particular

product youd like to test (you have to register as a

member of element14 to be able to apply to take the

test). If you choose to email me, please detail in a short

paragraph the reason why youd like to test the devices,

as it will allow us to distribute the devices to test in the

PICkit 2 DevelopmentProgrammer/Debuggerwith Flowcode 3Microchips PICkit 2 Development Programmer/Debugger(PG164120) is a low-cost development tool with an easy-to-use interface for programming and debugging the companys

Flash families of microcontrollers. The full featured Windowsprogramming interface supports baseline (PIC10F, PIC12F5xx,PIC16F5xx), midrange (PIC12F6xx, PIC16F), PIC18F, PIC24,dsPIC30, dsPIC33, and PIC32 families of 8-bit, 16-bit, and 32-bitmicrocontrollers, and also many Microchip Serial EEPROMproducts.

With MPLAB IDE, the PICkit 2 enables in-circuit debugging onmost PIC microcontrollers. In-Circuit-Debugging runs, haltsand single steps the program, while the PIC microcontroller isembedded in the application. When halted at a breakpoint, the leregisters can be examined and modied.

PICkit 2 development programmer/debugger

44-pin demo board with PIC16F887 midrangePIC microcontroller

A series of 12 lessons on assemblyprogramming that cover I/O, A/Dconverters, timers, interrupts, anddata tables (All source code lesare provided)

A debugging tutorial on using thePICkit 2 as a debugger with theMPLAB IDE (Ch. 4 of the PICkit 2Users Guide)

Getting started in C tutorial ondeveloping and debugging in C witha FREE CCS PCM Midrange C Compiler

Demo for PIC16F887 (contained on thePICkit 2 CD) *2kWord Program Limit.

Getting Started in C tutorialon developing and debuggingin C with a FREE HI-TECHPICC LITE C Compiler withMPLAB IDE

MPLAB IDE software for acomplete code developmentenvironment

How to get your hands on these products.widest number of applications and give the broadest

spectrum of reviews.

Thanks again to everyone who has written in before.

If you were selected, I look forward to reading your

reviews, and if you werent, please try again. Once

again, a special thank you to Texas Instruments and

Microchip, who have kindly supplied this equipment.

Dont forget to visit the RoadTest group at element14

to see the winners and reviews. n

Flowcode 3Flowcode 3 is one of the worlds most advanced graphicalprogramming languages for microcontrollers. The great advantageof Flowcode is that it allows those with little experience to createcomplex electronic systems in minutes. Flowcode achieves thisin two steps. First, drag and drop owchart symbols onto thescreen and ll in the dialog boxes when prompted. Then Flowcodecompiles the ow chart into code that is downloaded to a

microcontroller which executes the program.

Flowcode contains standard ow chart icons and electroniccomponents that allow you to create a virtual electronic systemon screen. Use the drag and drop interface to create a program andclick on each icon and component to set the actions and propertiesyou need. The range of components is large and includes simpleswitches and LEDs, communication bus interfaces like I2C and SPI,and more advanced components such as Bluetooth and internetservers.

ROADTEST

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Alternative

energy

te hme dep Sm hme s e w'sfs lEEd Pum "e- b" ............ 16

aces s -ce pbe pucs .....18

Us Mxmum Pe Pwe tce ece s pwe ssems ........................21

reuce se sb pwe

w u-w-cue, PFM dC-dC cees ....22acceee u se we UPS eepme ......24

opmz cpcs w pwe pp cs .....................................26

S ee b epccesce bubs.............................................28

Pwe csump FPga es ....................30

Since the development of the

steam engine, the inhabitants

of the earth have relied on non-

renewable resources such as coal,

gas, uranium, and most importantly,

oil to power homes, workplaces and

transportation. Power generated from

these sources is quite efcient and

drawbacks such as pollution at rst

seemed easy to ignore.

Now times are changing and the earths seemingly innite supply of non-renewableresources is becoming scarce, and what remains is harder to extract, making energy moreexpensive. The pollution that was ignored for so long has become a major problem, as thepopulation of the earth boomed and demands for energy increased accordingly. Globalwarming, which is thought to be caused, or at least exacerbated, by burning fossil fuelshas also become a major factor that could endanger life on the planet, according to manyscientists.

If we are to halt global warming and conserve the earths remaining non-renewable energyresources, we have to look to natural and renewable sources of energy that do not contributeto global warming. Sun, wind and water power are now making a comeback, driven by

todays technology. Biofuels are another source with the potential to change the way wecreate and use energy.

We are only starting to develop these renewable energy sources, and as such, they are notas efcient as our older energy sources, which have been in development for centuries. It ismuch harder to extract usable energy from natural sources, so we must work to make it asefcient as possible through every stage, and technology is the key to this.

Governments around the world havegiven the renewable energy market aboost by setting mandatory targets forelectricity production. The EuropeanUnion and Australia, for example, aimto have 20% of electricity by renewablesources by 2020, and Switzerlandincentivizes energy producers with atariff for renewable energy. The UnitedStates has no mandatory targets forrenewable energy, but offers subsidies,

tariffs, tax exemptions and other support.Although there are no federal targets,29 individual states have implementedtheir own mandatory targets. China hasno mandatory plan, but aims to equal oreven exceed the EU by 2020.

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Automotive industryAutomotive designers have been oneof the rst to move away from non-renewable energy sources in theirproducts and their technology currentlyleads the way. Toyota, REVA and Teslahave pioneered technology for thismarket and turned it into commerciallyviable products. Fossil fuels have beenreplaced, or at least supplementedby electricity in these companiesvehicles. Other vehicles have been

designed to operate using biofuels.

These examples are a good start,but not necessarily a long termsolution; electricity still has to begenerated and the vast majority ofthat generation is mainly throughthe use of fossil fuels. As for the useof biofuels, there have been riotsin some countries because landthat was normally used for foodprovision has been turned to use increating biofuels, creating either foodshortages, or a large increasein food prices.

Alternative energy generationTaking usable energy fromalternative sources has not provedeasy. One of the major problems is thatthe load points for the energy are usuallyin large cities, which are well awayfrom any wind farms, hydro plants orother energy generation points. Apartfrom hydro power, renewable energysources do not guarantee a constant,reliable source of energy. If the windstops blowing, or if it is a cloudy day,these sources will not produce the

optimal amount of energy, meaning thatelectricity needs to be brought in froma more distant source, further droppingefciency. This has placed moreemphasis on power saving and efciencyin appliances. After all, the less powerthey draw, the further electricity goes.

Accurate control and the ability toswitch between sources have made UPSdevices popular in alternative energysupported powergrids, especially smallerlocalized grids. The UPS can be used asa pure inverter for batteries charged byalternative energy sources, and switch

over to a mains supply if the power fromthe batteries drops below the requiredamount. Microchips article, which starts

These applications usually do notrequire the circuit to be in operationconstantly. It is more usual that the MCUwill be awakened either by a signal fromthe network or at a predetermined timeto take a measurement. Then it willsend the data back wirelessly and it will

power down again. As the circuit spendsthe majority of its time in sleep mode, itcan operate almost indenitely; in somecases the circuits are specied to operateindependently for over ten years.

A great example of this type of circuitis showcased in this months EmbeddedCorner Texas Instruments article onhow the companys MSP430 MCU andCC2500 RF transceiver are being used ina vibration scavenging application byAdaptivEnergy.

Scavenged energy can be use as astandalone source of energy, or totrickle charge a battery. The batteryoption has found a new marketfor an older battery technology.Lithium-thionyl chloride batteriesare generally not used in consumerapplications because they cannotcompete in power density withmodern battery technologies. Butthis battery technology offers twomajor advantages; it is suited toextremely low-current applicationsand it has a very long life. Theseadvantages make Lithium-thionylchloride batteries ideal for use in

remote monitoring systems.

SummaryWhichever side you are on of the

global warming debate, there is nodoubt that alternative energy sourcesare the future of energy generation.This generation not only applies toenergy on a national grid type level,but also to many smaller devices.As technology improves, these deviceswill become bigger, and who knows,it may not be long before we see the rstsolar-powered television.n

on page 24, details how UPS designs thatare based around the companys dsPICcontroller, guarantee a clean, reliablepower supply.

Solar power for handheld devicesWhen talking about alternative energyits easy to think of windmills and hydrodams, but also just as important aresmaller self-powered devices. Previousgenerations of handheld productshave featured solar charging either tosupplement a battery or to power thedevice completely. In general, theseproducts have been a novelty, and asometimes expensive one for a varietyof reasons, including inexibility fordesigns, and more importantly, theinherently inefcient behavior of solarcells in series.

On page 18, IXYS article takes a lookat some of the historical problemswith solar cells and discusses howtodays technology can overcome thosedrawbacks, and enable new products toincorporate solar charging. The marketis changing and solar cells are becominga lot less expensive. By as early as thisyear, the total cost of ownership for solarpowered devices could be equal to mains

power, and after that, solar power isdestined to become even cheaper.

Energy harvestingEnergy harvesting or scavenging is anew area of technology which has beenenabled by ultra low-power MCUs andlow-power wireless protocols like Zigbee.Energy can be harvested from a varietyof sources, such as solar power, vibrationor even radiated magnetic energy fromhigh voltage cables. This normallywasted energy can be scavenged toprovide power for a small remote sensor/metering circuit, an MCU forcontrol and a wirelesstransmitter/transceiver.

ALTERNATIVE ENERGY

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The centerpiece of this program is theHome Depot Smart Home, a unique10-person student residence hall forgreen living, learning and research.The 6,000 square-foot dorm containsve bedrooms, three bathrooms, alarge common area that serves as thekitchen, a dining room, gatheringplace, a clean lab, dirty lab and mediaroom. Completed in December 2007,the facility achieved LEED Platinumcertication for its innovative

design from the U.S. Green BuildingCouncilthe highest possible rating

achievable www.usgbc.org

The inspiration for a live-in researchlaboratory at Duke came from seniorengineering student Mark Youngerin 2003. Given the go ahead, he andan ever-growing cast of studentsspearheaded the design, fundraising,and construction process. The programcontinues to be a mostly student ledventure. The more than 100 Dukestudents now involved participate in a

variety of ways: independent study forcredit, house courses on sustainabilitytopics, senior capstone design

projects, or as members of the SmartHome student club. Student teams areencouraged to prototype their ideasand compete in various competitionseach year.

This article proles the work of

four Smart Home Fellows who areconducting intensive, research-oriented independent study projects.

Smart Use of Sensors Conserving Energy and TreatingNerve PalsyThe central theme of Smart HomeFellow Ben Hamners project is signalprocessing: integrating informationfrom sensors, appropriately processingthis information, and then acting onthis information.

Signals are omnipresent, he explains.

The power consumption of your TV isa signal. When you blink at the screen,

The Home Depot

Smart Home is the worldsfrst LEED Platinum live-in laboratoryThe Duke Smart Home Program encourages students from different

academic disciplines to explore smart technology and sustainable living.

The program promotes teamwork, innovation, diversity and education in

order to enable a lifestyle that reduces energy use and harmful effects

on the environment.

ALTERNATIVE ENERGY

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the change in electric potential acrossyour eye is a signal. The electricalpulses your keyboard sends to yourcomputer is a signal, along with theminute electrical variations on thesurface of your forearm as you type.

Ben, a triple major in biomedical

engineering, electrical and computerengineering and mathematics, istackling three distinct problems inhis project. First, he plans to trackhow much power is being used by allthe devices through an inexpensive,reliable network of sensors thatwirelessly monitor the powerconsumption at every outlet.These signals will be received,processed, and stored in an onlinedatabase system. Then, signal analysistechniques and psychological feedbackmechanisms will be used to display

the information to the user andmodify the users behavior to reducepower consumption.

His second project is to treat patientswith facial nerve palsy. The mostcommon treatment option is toimplant an unsightly gold weight inthe eyelid that restricts vision in orderto prevent infection. To x this, he isworking with doctors and leading ateam to prototype a device that detectsa blink in the non-paralyzed eye viasurface electromyography (sEMG) andstimulates a synchronous blink in the

paralyzed eye.

In his third project, Ben hopes touse sEMG signals from the forearmto determine what key a person ispressing and enable people to typewithout a keyboard. This project hasthe potential to enable amputees totype and enhance how millions ofusers interact with their phones. Ben isworking with electrical and computerengineering professor John Board.

Mobile Lighting Control Harnessing the Smart in Cellular

DevicesOriana Wen, a double major inbiomedical engineering and electricaland computer engineering, saidshe didnt realize the full potentialof cell phones until last year, whenshe worked on the Mobile LightingControls Team of the Smart Home.Using Internet-enabled cell phones,Orianas team expanded the range ofcontrol over the Smart Home dormlights, enabling residents to talkto the lights system and easily turnoff lights from any distance with the

simple ip of a cell phone.

Inspired by that success, Oriana isnow working with Dukes Romit RoyChoudhury in the Department ofElectrical and Computer Engineering.Choudhury is the inspiration behindthe PhonePoint Pen write in the airwith a phone concept much in the

media this year. Orianas project aimsto use a cell phone camera to recordand track a ngers movements inthe air. She will then map out themovement of the users nger todecipher what letters the useris writing.

By examining the pauses of the nger,we hope to differentiate betweenintentional and unintentional strokes,she explains. The arrangement ofthese intended strokes will then mapto a character that is registered bythe phone.

Whats more, the project canessentially be done even without acell phone. As long as there is a videocamera on hand, the nger can berecorded and tracked. This opens upnew avenues of consideration, such aseliminating chalk or dry erase boardsfrom classrooms, or helping hospitalpatients with limited range of motionto communicate more easily.

Effective Wireless PowerTransmissionIt is now conveniently commonplace

for homes and cafs to have wirelessInternet. But how about tables thattransmit power wirelessly to laptopcomputers, mobile phones and otherelectronic devices?

Yink Teo, a senior majoring inelectrical and computer engineering,is developing a wireless powertransmission system for the SmartHome dorm. His power-transmittingsurface is built into a frame of a coffeetable and will be able to transmittens of watts of electrical power toa receiving unit placed on top of it.

Different receiving units can thenbe adapted to recharge commonelectronic devices, such as cellphonesand laptop computers.

Wireless power transmission isachieved through resonant inductivecoupling, but unlike the non-resonant coupling found in a typicaltransformer system, we introduce ahigh Q L-C resonator. A primary drivecircuit is built using an oscillatorand MOSFET driver that drives thegate of a power MOSFET connectedto a primary coil. This primary coil

drives the L-C resonating coil, whichthen causes magnetic ux couplingwith a non-resonant pick up coil. Heis optimizing the design parametersfor this project through extensivecomputer modeling that helps himunderstand the behavior of our

resonant system.Hear the Difference...SeriouslyDukes Sabrina Liao, a junior majoringin electrical and computer engineeringwith a minor in German, is leading aproject to take traditional sensor datasuch as energy and water usage andprovide the output as sound.

Humans have evolved a wonderfullyadept ability to simultaneously processand make sense of myriad streams ofauditory information: the sounds ofthe wind, a bird chirping, students

talking on the quad, cars passing, aplane ying overhead, music from anIPod and much more.

There are any number of ways torender the data, she explains, butI want to explore the audio for thisproject as it is not as well developed.We can take advantage of the fact thathumans can focus on another activityand still be alerted to changes withauditory messages.

Currently in the Smart Home atDuke, there are sensors for such data

as the total usage of rainwater, totalusage of natural gas, the lights, andthe temperatures of the tank and theroof for the solar hot water. She hopesto generate a sound clip using thehistory of the data, starting with whichlights are on at what times. Sabrina,originally from Pasadena, CA, isworking with Research Associate SteveFeller and Research Scientist RachaelBrady, director of the Duke ImmersiveVirtual Environment.

Sabrinas vision is to have differentsections of the Smart Home correspond

to different sections of an orchestra:when the lights in a certain roomare on, the corresponding orchestrasection (e.g. violins) will be heard inthe music that is continuously played.Once that is proven successful, otherdata sources will be worked on. Onceall these components are integrated,those living in the Smart Home andin future buildings like it will be moreaware of important conditions oftheir environment.

Photo by Duke Photographyn

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Industry detractors: Once the consumer electronicsproduct is sold, manufacturers glean extensive revenuesfrom all extemporaneous items, not the least of which isreplacement batteries.

Low efciency: The efciency of a PV cell is denedby the ratio of the electric energy generated by the celland the energy of irradiance incident at the cell surface.Due to mobile operation and indoor use, light capturein PV powered consumer products can be quite low.Further hampering the energy harvesting effort, smallconsumer electronics have limited space available toimplant solar cells for enough light capture.

Inability to conform: PV cells must be lightweight,exible and capable of conforming to the design of theelectronic device. Regular cells (typically designed in apackage) cant conform to curves; amorphous cells betterconform to the design constraints of small consumerelectronics. However, as Andersson and Jacobsson (2000)pointed out, amorphous silicons efciency is quite low(6-8%).

Voltage: The PV power source must reach the batteryvoltage of 4-12V to ensure adequate recharging ofbatteries. Individual solar cells typically producebetween 0.3V and 0.6V, not nearly enough to meetrecharging demands. Solar cells must be packaged in aseries to produce usable energy amounts. Even when

packaged in a series, each cell only produces energy equalto the output of the lowest power cell. If a single cell isshaded, it affects the entire series.

Cell phones, MP3 players, PDAs, batteries and chargers,which typically use rechargeable batteries (lithium ion,NiCd), could have a solar cell added to their PC boards andbe charging constantly when light is available. In eachcharging application, solar cells will provide just enoughcurrent to hit the voltage limit extending battery life,overcoming self-discharge problems and providing anenvironmentally responsible solution.

Many low-power applications and devices spend thevast majority of their time in sleep mode, only wakingup periodically to perform a required function. Staticdisplays and intermittent sensors that utilize a very small

maintenance current are well suited to the use of solar cellsto supplement battery power.

Even the smallest remote sensing and data collectiondevices require some amount of current to operate, even intheir standby mode. The need to provide small amounts ofcurrent over long periods has spawned new battery designs,and this work continues today. The other part of the powerequation is in providing additional power to maintain thesebatteries as long as possible, once the device or sensor isinstalled in the eld.

For all of the various applications that could benet fromsuch energy harvesting, few manufacturers and designershave implemented solar charging for portable product

batteries. Why?

Advances in

solar-chargedportable productsSuce: iXyS Cp www.xs.cm

As designers of portable devices pack greater

functionality into products, power management

requirements have increased. Products require

multiple supply rails, battery charging and a

variety of power management capabilities all ofwhich are implemented to maximize battery life.

The frustration of a cell phone dying, or a laptop

powering off, is not uncommon in our tech-driven

world. Such irritations proved the impetus for

new battery developments, power management ICs

and new energy harvesting techniques (vibration

transducers, thermoelectrical converters, RF

converters and photovoltaic cells (PV)). Today, PV

conversion of light into electricity remains the most

effective way of harvesting ambient energy.

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High cell costs: The need for a large series of solarcells to produce 4-12V of usable energy makes solarcells cost prohibitive.

No break-even: Consumer products have a shortlifetime in the range of 2 to 6 years, so PV systems inthese products suffer a similar fate. In combination withlow light capture, the energy payback time of PV systems

in consumer products might exceed the productslifetime.

PV cell technologyPhotovoltaic cells (monocrystalline, high-efciency solarcells) incorporate an enhanced light-trapping surface withthe potential to generate the voltage necessary to powerbatteries in all types of applications. Manufactured withSilicon-On-Insulator (SOI) process technology, a singlechip could hold multiple solar cells in series, so that a widevariety of voltages is possible. With 24 solar cells on a singlechip, the semiconductor chip gives off 12V (when exposedto natural light) enough to power both rechargeable andnon-rechargeable batteries.

Monocrystalline cells have a spectral sensitivity rangefrom 300nm (near-ultraviolet) to 1100nm (near-infrared),which includes visible light (400 - 700nm). Due to thiswide spectral range, they can be used in both indoor andoutdoor applications. Monocrystalline material does notcontain impurities, and as such, the power conversionefciency does not degrade over operating time. With acell efciency of between 17-20%, a solar chip gives theability to extend run time even in low light conditionsand increase battery life and run time on a small footprint,which can be easily accommodated in the design of portableproducts. Conventional rechargeable batteries can takeseveral hours to recharge; using a solar cell, the battery canbe continuously trickle charged while under a light source.Low efciency currently dictates the need for PV cells thatharvest energy under a variety of lighting conditions.

Given the present high cost of use of rechargeable batteries(more than $3.50 kWh), photovoltaic solar energy underoptimal light capture is cheaper now (about $0.50 kWh)and could become much cheaper in the future. Therefore, itis sensible to partly substitute batteries. Further dampening

the cost prohibitive argument, large scale grid integrationshave made PV cells cheaper (economies of scale). Hence,

if the price of electricity generated by PV cells equals thatof electricity from the mains, costs will not be an issueat all. Furthermore, cheaper raw materials and improvedmanufacturing processes are pushing down prices forPV cells and panels. Many companies and analysts arepredicting that solar power could become cost competitivewith natural gas-fueled electricity as early as 2011.

For the time being, other factors such as ease of use,increased personal mobility, reduced environmental impactand long stand-by times have added value that cant beneglected, yet remain difcult to quantify.

Engineers have sought to package solar cells into the devicein an unobtrusive way (either placed under a devicesdisplay or cover). This integrated design would allow themobile device to be charged from daylight, without having aseparate solar panel be plugged into it.

The circuit design is fairly simple: the batterycharging current is generated by four series-connectedmonocrystalline, high-efciency solar cells. Each cellgenerates 0.63V open circuit voltage and 42mA shortcircuit current. A Schottky diode prevents the battery from

discharging through the solar cells, when the output voltagefrom the solar cells is lower than the battery voltage, ashappens when sufcient light is unavailable.

With the level of efciency and voltage capabilityinherent to the solar chip, it makes it a perfect t forconsumer products including cameras, digital musicplayers and phones. First movers are already integratingthe chip into consumer/portable products in testenvironments. Until full scale integration meets withbroad success, the solar industry is utilizing advancedtechnologies to produce solar chargers.

Iterations of the solar battery charger have already comeand gone. Old cumbersome chargers have been replaced

by smaller systems with new solar charger circuits thatuse a MOSFET as the blocking mechanism to preventbattery back discharge and a small solar cell to powerthe gate of the MOSFET to turn it on and off. The use ofthe MOSFET eliminates the need for an additional morecostly solar cell to overcome the forward voltage drop ofthe blocking diode.

SummaryIn a natural progression, solar chargers will eventuallycede to solar cell integration in portable products and

consumer electronics. According to the Solar EnergyIndustries Association (SEIA), the U.S. stimulus bill givescompanies greater exibility in nancing solar powerprojects. Such government incentives will likely result

in renewed interest for solar power and PV-embeddedapplications, ultimately reducing strain on the electric gridsand introducing advanced green solutions.n

IXYS' portable solar charger provides a convenient, environmentally-conscious, charging solution for portable electronic devices.

IXYS' SolarBits provide a new level of manufacturingease and are ideal for charging mobile phones,

cameras, PDAs, MP3 players and toys.

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The Maximum Peak Power Tracker (MPPT) circuitry is embedded in highly efcientcharge controllers to maximize available power, by nding and using the maximumpower point (MPP) dynamically. MPPT controllers can increase the total useablepower by as much as 50% in some applications. An MPPT charge controller consistsof a DC/DC buck/boost converter and an embedded microprocessor. Since themaximum power at any point in time (Pmax = VI) is dependent on variable weatherconditions such as sunlight (clouds, shade, rain) and temperature, the controllercontinuously recalculates to match up the solar panels voltage and current output tothat of the batterys charging needs.

To see the difference requires an evaluation of the performance of two systems:one with a simple charge controller and the other a MPPT controller. In the simple

charge controller example, a 12VDC @ 200W solar panel is used. The solar panelsspecication sheet lists a nominal 12VDC output, but the actual voltage typically canvary between 16VDC to 20VDC with maximum voltage only achieved on perfectlysunny day. Solar panels are purposely designed to produce more voltage thantheir rating. A 12V rechargeable battery will measure between 10VDC to 13.5VDCdepending on its charge state. Batteries connected to the solar panel via the simplecharge controller or even a PWM charge controller, will see a constant 12VDC signal.The controllers output does not change regardless of temperature, charge timeand/or battery capacity. While this simple controller will charge up the battery,it does so in an inefcient manner due to its inability to take into account thechanging maximum power point of the system.

With a MPPT system, the controllers output depends on both battery conditionand the solar panels harvested energy. Solar panels have a peak point on thevoltage-current curve, which is the maximum power point. As the MPP changes,

the controller tracks it and compares it to the batterys charge levels to determinethe minimum voltage needed to safely charge the battery. Determining theminimum voltage allows the controller to maximize its output current. Asthe batterys voltage increases, the controller adjusts to ensure that the chargevoltage is always a bit higher. Failure to charge to battery at its maximum powervoltage decreases the efciency of the system. The increase in delivered powerallows design engineers to use smaller panels for their applications.

The systems DC/DC converters are capable of working in either buck or boosttopologies. If the harvested voltage is greater than that of the battery, a bucktopology is used, and if the harvested voltage is less, a boost topology is used.In boost topology, the increased voltage results in a decrease in current. Lowercharge currents prolong the charge time. However, it ensures that the battery ischarged in less than perfect weather conditions.

Several vendors have varying ICs for implementing the MPPT algorithm usedin customer solutions. Texas Instruments offers the TMS320F2833xx family ofdigital signal controllers. Linear Technologys LT3652 can be used to achieve

similar results. But Xantrexs XW seriesof charge controllers provides a completeout-of-box MPPT controller solution.

MPPT controllers in solar poweredsystems provide other advantagesin addition to improved efciency.With the ability to harvest and storeenergy even in bad weather conditions,the batteries are protected from deepdischarge. The controllers come withbuilt-in overcharge protection helping

to prolong battery life, while improvingsystem reliability. However, the greatestadvantage from the MPPT algorithmis still the increased efciency, whichin some systems can reach as highas 99%.n

Using Maximum

Peak Power Trackerto enhance solar power systemsB deck lb, techc Supp, newk

Although solar power has caused a great deal of excitement in the

search for clean energy, a typical solar panel can only convert about

20 to 30% of available sunlight into electricity. In order to get the

most out of solar energy, Maximum Peak Power Tracker controllers

are used to improve the overall system efciency and reliability.

Graph showing the max power point. Currentdecreases with increasing voltage. MPPTcontrollers calculate the best voltage level that

is able to charge the battery whiles maximizingthe charge current

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converter in those systems should begalvanically isolated. A transformerprovides the isolation, but the challengeis to feedback the voltage reference fromthe secondary side to the primary sidewithout breaking the isolation. The mostcommon approach solves the problemby using either an auxiliary winding oran optocoupler.

The power-supply topology is a step-down approach: the battery pack usedby the application has a nominal voltageof 12V, while the internal electroniccircuits in the system operate at 3.6V,nominal. Figure 2 shows the schematicdiagram of the DC-DC switchingregulator. When the control loop isregulating the voltage, the optocouplerrequires a constant current throughthe LED on the primary side of thetransformer. The lower limit of the

current is xed by the optocouplerscurrent transfer ratio (CTR) at low biascurrents (63% at 10mA, and 22% at1mA) and by a reduction of the responsetime (2s at 20mA and 6.6s at 5mA).

The current consumption of the outputvoltage divider (formed by resistors R5and R11) is xed to 7A. Because of this,the 0.5A required by the referenceinput, plus its thermal deviation, doesnot signicantly affect the outputvoltage. Additionally, the voltage

measured at the divider output doesnot suffer a relevant delay, thanksto the low-input capacitance. Thislatter fact precludes the need fora capacitive divider to reduce theinput capacitance of the precisionreference. In the optocoupler, thephototransistor draws 60A, (IFB< 60nA), which translates into acurrent ow through the LED of lessthan 230A (CTR ~26%).

ControlTo implement a PFM controller, theMAX1771 BiCMOS step-up, switch-

mode power-supply controller (U1)can be used to provide the necessarytiming. The MAX1771 offers

improvements over prior pulse-skippingcontrol solutions: reduced size of theinductors required, due to a 300kHzswitching frequency (the current-limited PFM control scheme achieves90% efciencies over a wide range ofload currents), and a maximum supplycurrent of just 110A. Besides theseadvantages, the main characteristicsof the MAX1771 in a nonisolatedapplication are: 90% efciency with loadcurrents ranging from 30mA to 2A, upto 24W of output power, and an input-voltage range of 2V to 16.5V.

The resistances of the voltage-controlloop have been chosen to have thehighest possible values. This decisionrepresents a trade-off between currentconsumption and loop stability. Asa result, the current through thevoltage-divider is less than 7A. Since

the ltering capacitors are non-ideal,capacitor leakage current must be addedto this current. In this design, lter-capacitor leakage current in C5 and C8is less than 20A. If lower leakage is

required, these caps could be upgradedto ceramic capacitors with the followingcharacteristics: 100F, 6.3V, X5R and1206 size (Kemet C1206C107M9PAC).Using ceramic capacitors reducesthe capacitor leakage to just a few

microamps. Note however, that theceramic capacitors cost about 3xthat of the tantalum capacitors, andthat difference would increase thesystem cost.

Figure 3 shows the prototype PFM DC-DC converter that draws a quiescent

current of just 0.24mA. The boardmeasures less than 50mm by 30mm,can deliver 3.6W with an input-voltagerange of 10V to 15V (12V nominal),and operates at a switching frequencyof 300kHz. The converter can supply amaximum constant output current of1A, while delivering a regulated outputof 3.6V. Employing a yback topology(step down) with both current andvoltage feedback control, the converteroutput is galvanically isolated fromthe input.

The prototype can be used in variouswireless applications that operate ina discontinuous transmission mode.The current consumption of the radiomodules can peak at 3A, and the

maximum mean current is1A. Some basic guidelinessuggest that designersshould use high-valuecapacitors that have lowseries resistances.

SummaryInitial industry surveysindicate that the best

commercial isolated DC-DC converters for powersupplies with low currentconsumption under no-loadconditions typically haveabout 20mA minimumcurrent consumption. With

minimal effort, designers can use a PFMscheme to implement a low-I

Q, isolated

power supply that has the lowest currentconsumption on the market. The no-load current consumption of the powersupply presented here is only 0.24mA.n

Figure 2. Schematic of an isolated PFM yback DC-DC converter.

Figure 3. Top view of the DC-DC PFM converterprototype for wireless applications.

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UPS systems have also found a new niche in the alternative energy market as

inverters, which take stored DC voltage and invert to a reliable, clean AC voltageoutput.

Microchip developed the 1kVA Ofine UPS Reference Design to speed updevelopment while achieving higher performance and lower cost for todaysmarket needs.

Figure 1 shows a block diagram of the Ofine UPS Reference Design indicating signalow and power ow in the entire system.

System BlocksThe Ofine UPS Reference Design consists of three main power conversion stages,namely the Push-pull DC-DC converter, Full-bridge Inverter, and a Flyback batterycharger. The system also includes an LCD module and a USB port to connect acomputer for power management or remote monitoring. The dsPIC Digital Signal

Controller (DSC), with its intelligent power peripherals (high-speed PWM, fast ADCand on-chip analog comparators) forms the heart of the Ofine UPS. It controls allcritical operations of the system as well as user interface functions.

System OperationWhen AC mains voltage is present, the system is in battery charger (or standby)mode until a failure occurs on the AC line. During this mode, the battery is chargedand is maintained after becoming fully charged. When the battery is charging, thefull-bridge inverter is operated as a full-bridge rectier using the body diodes of theswitches. The yback switch mode charger functions as a current generator andprovides constant charging current to the battery. The charging current is variedbased on the state of the battery, and therefore, intelligent battery charging is achievedwith the dsPIC DSC.

After a power failure, the system is switched to Inverter (or UPS)

mode. This power switch-over sequence is completed in lessthan 10 milliseconds. During this event, the output relay logic isswitched to prevent power from being delivered to the AC mainspower grid. In the Inverter mode of operation, the push-pullconverter steps up the battery voltage to 390Vdc. This DC voltageis then converted to a pure sine wave 220V, 50Hz or 110V, 60Hz ACvoltage by the full-bridge inverter and output LC lter.

Software ImplementationThe functions of the main controller are broadly classied into thefollowing categories:

UPS State Machine:

All power conversion algorithms

Executes switch-over from Battery Charger mode to Inverter mode and vice versa

Implements critical protection

schemesHousekeeping Functions:

Performs RMS calculations

Includes soft-start routines for allpower conversion stages

LCD display control

USB communication

The software is structured with respectto execution priorities of the varioustasks. The highest priority tasks arecongured in an interrupt-basedfashion. This structure ensures that the

software execution does not get stuck ina low-priority routine when other highpriority tasks are pending.

Inverter-to-Mains Switch-overRoutineWhen AC mains voltage is absent, thesystem keeps polling the AC mains incase power returns. The system shouldswitch from one mode to the other inthe shortest possible duration in order toprovide uninterrupted power to the load.

Accelerate your sine wave

UPS developmentMcchp tech ic.

UPS systems have become an integral part of many critical

electronic systems ranging from low-power personal computer

systems or residential battery backup systems, medium power life-

support systems, data storage, and emergency equipment, as well

as high-power telecommunications, industrial processing, and online

management systems. As worldwide demand continues to grow, the

need for cleaner, more efcient and more reliable power has fueled

the advent of digitally-controlled uninterruptible power supplies.

Figure 1

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The power quality challenge in wind turbines stems from continuous and sometimesrapid changes in wind speed. A number of aerodynamic controls and generatorarrangements have been proposed to minimize these effects, but the raw AC outputremains subject to uctuations, harmonics and interruptions.

Wind turbines using inverter technology with DC linksThe wind energy market uses various techniques to provide regulated power directly toend users or to grid systems. Many of the electronic inverter systems make use of inverters,using a DC link with aluminium electrolytic capacitors and polypropylene lm capacitors,such as MKP technology metallized polypropylene lm, to smooth the DC-link voltages ofthe frequency converter.

Capacitors in use to smooth the DC-link voltagestypically have a high voltage rating, feature screwterminals, and are assembled in a capacitor bankconguration. They also have high ripple currentcapabilities in order to withstand load differences andperform reliably over a long lifetime of service.

Capacitance values and voltage ratings, chiefamong the other important parameters, can bedelivered to suit individual application requirements.There are standard products developed for theserequirements like Vishay BCcomponents 102 series.In addition, customized solutions will tune thedemand for an effective costperformance ratiofor each typical application.

Capacitors for use in a suitable DC link aretypically aluminium electrolytic devices of Vishay

BCcomponents (see Figure 1)and DC MKPlm capacitors of Vishay ESTA, whichmust have high ripple current capability inorder to withstand the current transientsstill present in the rectied input to theDC link.

Power factor correctionPower factor correction (PFC) is afunction common to all wind turbineinstallations, regardless of size, ratingor application. Because of their low-lossbehavior and high energy density, ACheavy current power capacitors in MKPmetallized polypropylene lm technology(see Figure 2)are the most suitable forpower factor correction.

Figure 2: Vishay ESTA power factorcorrection capacitors low voltage,

ESTAprop/ESTAdry (MKP-type capacitors)

For utility-class wind turbines andother installations that may beintended to connect to the grid, PFC isa legal requirement to remove reactivecomponents from the power. This is

necessary to maintain efciency in thetransmission network and to preventdamage to other connected equipment.In systems not intended for connection tothe grid, PFC helps maximize efciencyand power quality. The variable natureof the raw AC generated from the rotormeans that wind turbines need large banksof capacitors that are step-wise switchedin and out of circuit under the controlof a supervisory system that continuallymonitors the actual power factor againstthe target.

Capacitor enhancements for windpower applicationsComponent manufacturers are takinginto account the special requirements ofwind power applications. For example, theneed to minimize losses wherever possibleis stimulating new interconnects andprotection mechanisms. Previously, manycapacitor banks for PFC were built withMKP-type capacitors tted with coiledwire inductors to reduce the inrush currentexperienced by each capacitor. But sincethe coils contribute permanent ohmiclosses, inrush damping pre-resistor devicesthat are only in circuit during switching

now protect the latest PFC capacitor arrays.These enhance the overall efciency ofthe system.

Optimizing

capacitorsor wind power applicationsSuce: vsh ESta vsh BCcmpes

All wind turbines face a similar set of challenges: they need to extract

power at low wind speeds and uctuating wind proles in order to maintain

adequate yield, ensure adequate power quality to operate appliances or to

feed into a grid, and the electrical system must be constructed to minimize

losses and maintain high efciency and reliability. This article discusses how

capacitors can be optimized to meet these challenges.

Figure 1: Aluminium capacitors with screwterminal for use in the DC link

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Further fundamental requirements of any wind turbine installation include highreliability and availability, combined with long maintenance intervals. This is as crucialfor utility companies who need to maintain protability as it is for remote communities orrural users, who are dependent on visiting service agents to ensure continuity of supply.

Capacitor manufacturers are paying special attention to these extreme demands for longlife and failsafe operation. When capacitors are used in wind turbine installations, regularmaintenance of the contactors is very important in order to maximize the lifetime of

the capacitors. It is important to replace contactors before they harm the capacitors byimproper closing of their main contacts and continuous spiking.

Built-in Failsafe MechanismsAll-phase overpressure tear-off fuse systems, which have performed well in manyapplications for a number of years, disconnect the capacitor if the internal pressure insidethe device reaches a threshold level (see Figure 3). Excessive internal pressure may resultfrom excessive overvoltage conditions or excessive repetitive inrush current, resultingfrom extremely frequent switching without damping. In such cases, the overpressurecauses an expansion of the cover. Expansion over a certain limit causes the tear-off of theinternal fuses. The active capacitor elements are thus cut off from the source of supply. Thepressure within the casing separates the breaking point so rapidly that no harmful arc canoccur.

Stacked assembly of thewinding elements alsoprevents the risk of high-energy short circuits betweenline terminals by ensuringthat neighboring contactareas of winding elementsare connected with the sameline terminal. It also ensuresthe same proper contact areafor each winding elementto solder connections to theterminal.

Optimizing Longevity

Capacitor manufacturers have been paying careful attention to optimizing the ratio ofsurface area to the overall volume of the device, in order to maximize cooling efciency,and thereby enhance reliability and longevity. Slim can diameters (e.g. 84mm) ensureexcellent heat transfer to reduce the inner temperature inside the winding elements and toincrease life expectancy of the capacitor in case of very high loads. For some installationsand where there are restrictions on the maximum permissible height of the capacitors, amaximum case diameter of 116mm for MKP lm capacitors could still be considered forsufcient heat behavior.

These carefully optimized case dimensions are additionally supported by lling with a lowthermal resistance, non-toxic, non-PCB, environmentally-friendly, vegetable-based oil.

These measures to maximize heat transfer help typical life expectancy of Vishay ESTAMKP-type capacitors to exceed 150,000 hours, depending on how the ambient temperatureand operating conditions inuence the capacitor case temperature. The latest generation

devices of 84mm diameter can also sustain overcurrents up to 50A per unit, provided thecase temperature is kept below 65C maximum.

Special attention is being paid to lling capacitors with a suitable compound thatcomplements the environmentally-friendly nature of wind power, while also maximizingthermal conductivity to the surface of the device. Some manufacturers offer dryconstruction MKP-type capacitors by lling with an inert gas to avoid corrosion of thewinding elements and inner electric contacts. Although some engineers recommendthese for wind turbine applications, because of the environmentally benign propertiesof the inert gas, Vishay ESTA recommends oil-lled types for use in ltering and heavy-duty applications. Filling with a biodegradable, vegetable-based oil does not requirespecial precautions for disposal and is not hazardous even in the unlikely event of a leak.However, the oil used displays around seven times better thermal conductivity than theinert gas.

The layout of an electrical subsystem, such as the switching system and capacitor banksfor power factor correction, also has an important bearing on reliability and lifetime. Forexample, some early installations can be seen to locate the PFC capacitor banks at the

top of the cabinet, where they are mostvulnerable to heating, as a result of theenergy dissipated by all other components.In later installations, mounting thecapacitor banks nearer the bottom of thecabinet, below the switching elements, hasrectied this (see Figure 4). New capacitor

terminal designs also make it easier toconnect large capacitor banks for PFC.These feed through terminals allowcapacitors to be quickly daisy-chained,connected by cables with up to 25mm2cross-section.

Figure 4: Power factor correctioncapacitors run cooler at the bottom

of the electronic control cabinet

Self-HealingIn MKP technology capacitors, reachingend of life or experiencing inadmissibleelectrical or thermal overload cancause insulation breakdown to occur.A breakdown causes a small arc thatevaporates the metal layer around thepoint of breakdown and re-establishes theinsulation at the place of perforation. Afterelectric breakdown, the capacitor can stillbe used. The decrease of capacitance causedby a self-healing process is less than 100pF.The self-healing process lasts for only a fewmicroseconds, and the energy necessary forhealing can be measured only by means ofsensitive instruments.

ConclusionIncreased usage of wind turbineinstallations drives increased demand forcapacitors to condition the raw electricalpower produced by the various types ofturbine-driven generators. As researchin this area continues, componentmanufacturers can gain a greaterunderstanding of these special needs andtake these factors into account whenevolving new products. The ongoingexchange of information betweenresearchers, leading system integrators andcomponent suppliers is likely to lead toeven greater gains in conversion efciencyand power quality from wind turbineinstallations of all types and sizes. n

Figure 3: The all-phase overpressuretear-off fuse system

ALTERNATIVE ENERGY

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LEDs can be driven with a 230VAC mains input using a buck converter or ybacktopology. For 100% compatibility with an incandescent bulb, the LED solution shouldalso be dimmable using a standard Triac dimmer. Unfortunately, the LED ickers with

the TRIAC chopped waveform due to the fact that the light emitted by LEDs changesinstantly with the current.

National Semiconductor has developed the LM3445 that avoids the visible ickeringcaused by a TRIAC forward or reverse phase dimmer. The problem is overcome bytranslating the TRIAC-chopped waveform into a DIM signal and decoding it to a DCsignal. In fact, the LED current is linearly regulated according to the dimming signal.

This article will describe a solution with 8.5W power consumption that delivers 450lumens, which is comparable to a 40W incandescent bulb that provides around 500lumens. This solution drives six high power LEDs with the capability to dim them usingstandard off-the-shelf TRIAC-based dimmers.

One of the main points is the angle detect and Dim decoder to translate the trigger pointinto a DC current. The LM3445 LED driver integrates most of the functions needed to

translate a TRIAC dimmer angle into an average current running through a number ofLEDs. On the schematic in Figure 1, we see the entry point for the AC signal on the topleft side. This AC signal is rst rectied using a diode bridge, then translated to a lowervoltage level by a bleeder circuit and, nally, is fed to the BLDR pin of the LM3445.

Saving energy by replacing

incandescent bulbsSuce: n Semcuc

Incandescent lights are very inefcient, wasting most of the power they

consume. In effect, they convert only about 10 percent of the energy used

into light, while the rest is emitted as heat. An incandescent bulb produces

between 14 and 17.5 lumens per watt (the standard measurement of

lighting efciency) with 1000 hours lifetime compared to around 74

lumens per watt with 45000 hours for an LED.

Figure 1

ALTERNATIVE ENERGY

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There are four major power components associated with the design of an FPGAbased system:

Inrush Power

Conguration Power

Post Programmed Static Power

Dynamic PowerThe power component and reduction techniques of FPGA devicesvary depending on the underlying technology in the devices, suchas SRAM, SRAM Hybrid, Flash and Antifuse FPGAs. SRAM-basedFPGAs have all four major power components, whereas ash andantifuse FPGAs, which are non-volatile, have only two signicantpower components (static and dynamic power).

Inrush Power A current spike is caused when SRAM-basedFPGAs are powered up, because the volatile SRAM transistors arein indeterminate state initially. This current component is knownas inrush current, and is in the order of hundreds of milliamps.Flash- based FPGAs have very minimal inrush power, due to thelive at power-up (LAPU) conguration.

Conguration Power Conguration power is consumedduring the programming of SRAM FPGAs while downloading

bitstream data from a ash or EEPROMmemory device at system power-up.Typically this conguration time ishundreds of milliseconds and the currentis hundreds of milliamps.

Post Programmed Static Power This power consumption is due to the

large number of transistors on FPGAs,which have a small amount of leakagecurrent where the device is not activelyperforming any operation. This leakagecurrent contributes a signicant amountof power dissipation in deep sub microntechnologies. Also, ash-based FPGAs donot require any holding current to keepthe conguration data, and thus havethe lowest static power consumptioncompared to any other type of FPGA.

Dynamic Power This powerconsumption is due to the switchingcurrent of logic cells, where thedevice is actively performing anyoperation. Dynamic power is directlyproportional to operating voltage andswitching frequency.

FPGA Power Saving TricksSelect a Flash-based FPGA as it is atrue single chip solution requiringno conguring support, doesnt sufferfrom inrush power, and has lowstatic power.

Choose FPGAs with a low powermode, also known as sleep mode,where clock serving circuitry isturned off, and I/O is disabled,while preserving device states. Thisultimately reduces static power.

System clock frequency has adramatic impact on the overall powerconsumption of an FPGA device.Clock frequency directly relates tobandwidth performance, however toachieve an optimum balance betweenpower and throughput, a slowerclock can be supplied to componentsthat do not require a fast clock. Forcomponents that are critical tobandwidth, use a faster clock. n

Power consumption

in FPGA designSuce: aus Su, gb tech Cee

With FPGAs featuring higher and higher density, designers are making more

and more progress on power consumption reduction. Another reason for

the power reduction trend is that FPGAs are becoming more widely used in

portable devices like Smartphones, media players, gaming, sat-nav and digital

camera/camcorders. Power consumption is probably the most important

factor when choosing FPGAs for consumer electronic devices, as well as

for medical, industrial and even military applications. System reliabilityimprovement and easy upgradability are also important considerations.

Additional criteria such as cost, capacity, performance, features, power and

packaging also come into play in the selection process.

Fig: Volatile vs. Non-volatile FPGA Power Proles (Source: Actel)

ALTERNATIVE ENERGYALTERNATIVE ENERGY

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Part NumberV

DS

(V)

ID

(A)

RDS(on)

Max

@ VGS

=10V

(m)

Qg

(nC)Package

IRFS3004-7PPBF 40 240 1.25 160 D2PAK-7

IRFP4004PBF 40 195 1.7 220 TO-247

IRFS3004PBF/ IRFB3004PBF 40 195 1.75 160 D2PAK/ TO-220

IRFR4104PBF 40 30 5.5 59 D-PAK

IRFS3006-7PPBF 60 240 2.1 200 D2PAK-7

IRFS3006PBF/ IRFB3006PBF 60 195 2.5 200 D2PAK/ TO-220

IRFB3206PBF 60 210 3.0 120 TO-220

IRFS3206PBF/ IRFP3206PBF 60 210 3.0 120 D2PAK/ T0-247

IRFR1018EPBF 60 79 8.4 69 D-PAK

IRFP4368PBF 75 195 1.85 380 TO-247

IRFS3107-7PPBF 75 240 2.6 160 D2PAK-7

IRFS3107PBF 75 195 3.0 160 D2PAK

IRFB3077PBF 75 210 3.3 160 TO-220

IRFR3607PBF 75 80 9.0 84 D-PAK

IRFP4468PBF 100 195 2.6 360 TO-247

IRFS4010-7PPBF 100 190 4.0 150 D2PAK-7

IRFB4110PBF 100 120 4.5 150 TO-220

IRFS4010PBF 100 180 4.7 143 TO-220

IRFP4568PBF 150 171 5.9 151 TO-247

IRFB4115PBF 150 104 11.0 77 TO-220

IRFS4115PBF 150 99 12.1 77 D2PAK

Tailored for Synchronous Rectification

Optimized for fast switching

Up to 20% lower RDS(on)

*

Up to 20% increase in power density*

RoHS Compliant

Lead Free

*Compared to previous generations

for more information call +49 (0) 6102 884 311

or visit us at www.irf.com

YourFIRSTCHOICE

forPerformance

Lower RDS(on)

Higher Performance

THE POWER MANAGEMENT LEADER


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The redesign of aging electronic products presents uniquechallenges and creative opportunities to electrical engineers.For a complex electronic product, the quality of the redesigneffort often rests in how well the redesign-engineering teamunderstands how the design should be updated. Study of theoriginal electronic design is necessary, and understanding howthe original equipment functions, and what design choices theoriginal engineering team applied to achieve that functionality,is essential.

Orchid TechnologiesEngineering and Consulting,Inc. completed theredesign of the precisionLCR instrument shown inFigure1. Accurate to 0.05%of full scale, the original1988 instrument designwas very well executed.However, vintage 1980sstate-of-the-art electroniccomponents were going end-of-life at an alarming rate.

The rst step was to study the existing design, working

to put ourselves into the minds of the original designers.Through a process of study and review, the redesign approachwas identied. A detailed development plan was thengenerated proposing signicant technical improvementsand cost reductions.

Three primary technical opportunities became clear:

Update the aging DSP processor design

Modernize analog amplier components

Implement old digital logic with an FPGA

The original product contained an older Texas InstrumentsTMS320C31 processor, an outstanding choice for its day, butnow showing its age. Running at only 33MHz, this 32-bit DSP

represents oating point numbers in a Texas Instrumentsproprietary manner. Old upper level software performsoating point numeric conversions to make use of the DSPs

calculations. The redesign provided the opportunity to replacethe old DSP with a new Texas Instruments TMS320C6713.This new DSP performs at 200MHz and represents oatingpoint numbers in standard IEEE format. Old DSP rmwarewas ported to the new processor using Texas InstrumentsCode Composer Studio environment. The result was a newdesign that performs more than six times as fast as theoriginal instrument.

Twenty years ago, the original product was designed using

Analog Devices 24 bit DDS devices. A DDS device (DirectDigital Synthesis) is a highly complex electronic componentwhich generates spectrally pure sine waves using digitalnumeric lookup tables. A DDS allows the generation of sinewaves at virtually any programmable frequency. Althougha remarkable device for its day, twenty years is a long time inelectronics. Today Analog Devices modern DDS componentsmake use of 48-bit look up tables. Such DDS devices provideincredible frequency granularity and purity. The redesignopportunity was to integrate these new DDS components intothe redesign effort. As a result, the new design performed vetimes more accurately than was actually required.

Almost every older electronics product contains MSI (mediumscale integration) and SSI (small scale integration) electronic

components. Parts of this type are the familiar 7400 series quador dual logic function component. Such logic components areoften packaged in large dual in line through-hole technologypackages. Multiple circuit boards are often required in olderdesigns just to t the large sized component parts. Todaysopportunity is to collect those MSI and SSI parts into a single,far smaller programmable logic device. In the LCR meterdesign, we combined the functions of a 48 square inch boardinto a single 0.9 square inch programmable device from Altera.The result was two fold: we reduced product cost by requiringfewer circuit boards in the overall design, and we reduceddigital noise, thereby improving system accuracy.

Through these techniques, Orchid Technologies redesigned theclients instrument into one that performed the same functions

faster and much more accurately, while also reducing the sizeof the design.n

A case study:

Redesigning agingelectronic productSuce: och teches Eee Csu, ic.

Updating out-of-date designs is a major part of the

electronic engineers job. Many viable products need to

be redesigned, mainly because of components availability

and to improve the products performance. This case study

was written by Newark customer Orchid Technologies, to

show the decisions taken and the techniques used when

updating an instrument for one of its customers.

Figure 1

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serious technology

If youre serious about sensing, youve come to the right place.

Honeywell offers advanced products designed for demanding sensing environments. These state-

of-the-art products position, speed, current, load, torque, pressure, humidity, temperature, and

optical are found in potential aerospace, industrial, and medical applications worldwide. And

were constantly adding to our well established technologies such as Hall-effect and microstructure

by commercializing new technologies such as wireless, Surface Acoustic Wave (SAW), MR array,

and sophisticated optical sensing. We also offer interface capabilities for analog or digital output as

well as bus connectivity in designs small enough for demanding medical environments or cramped

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