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April 3, 20

Dave BaarmanFulton Innovation

Electrical Engineering Commun

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TABLE OF CONTENTS

Dave Baarman 4FULTON INNOVATION

Featured Products 9

Understanding Wireless Power - Part IBY DAVE BAARMAN AND JOSHUA SCHWANNECKE WITH FULTON INNOVATION

A Simple Circuit to Generate Plus 18And Minus Supplies Using a Boost RegulatorBY DON LAFONTAINE WITH INTERSIL

RTZ - Return to Zero Comic 23

Interview with Dave Baarman - Director of Advanced Technologies

With differing perceptions of wireless power demands among developers and consumers, itsimportant to find common ground for future wireless power solutions.

See how using a boost converter can help you get larger supplies of both positive and negativevoltages within your circuit.

11

7/31/2019 Eeweb Pulse 2012 40


INTERVIEW

Fulton Innovationwater treatment system to eliminate6-log reduction or 8-log reductionof bacteria and viruses. It ended

up becoming a flagship product for

Amway.

From developing that water

treatment system, we created a very

unique wireless power system that

had a lot of versatility and was highlyresonant in the way that it would

adapt and respond to environmental

changes like temperature, space

and pressure. It was then that we

realized we really had a winning

product.

Can you tell us more aboutthe 400 patents you hold inwireless power technology?

We began developing the watertreatment system and the wireless

power system about 15 years ago

and we saw a very open white-

space of intellectual property

in the patenting world. So we

started patenting back then on

this technology, and really havent

stopped since. Actually, as it sits

DaveBaarman

Dave Baarman - Director of Advanced Technologies

How did you get into electricalengineering and when didyou start?

I always wanted to be an engineer.

Much of my purpose revolves

around being someone innovative

and who can develop new products.

I am very interested in research and

developmentmy first job was

actually in automotive research anddevelopment.

I also have a very entrepreneurial

mind. I started my own business,

sold it, and became a consultant.

I later got hired by Amway as a

consultant to provide wireless

power to a water treatment system.

Out of that relationship, the eSpring

water treatment system was born.

We created a wireless-powered

lamp system to be dropped into the

7/31/2019 Eeweb Pulse 2012 40


INTERVIEW

right now, we have a portfolio of over

700 patents pending or granted in

just the wireless power space.

Can you tell us about beinga founding member of theWireless Power Consortium?

The goal of the Wireless Power

Consortium is to establish Qi

(pronounced chee) as the global

standard for power rechargeable

electronic products. It has more

than 100 members including

industry leaders in mobile phones,

consumer electronics, batteries,

semiconductors, components,

wireless power technology, andinfrastructure such as wireless

operators, furniture and automotive

parts companies.

Some member companies include

Motorola, Samsung, Philips, Verizon

Wireless, Texas Instruments, LG

Electronics and many more. A full

list of member companies can be

found here.

Fulton and the WPC believethat global standards are a vital

step in driving widespread

consumer adoption of wireless

power, and opens up the door

for full interoperability between

device manufacturers and OEMs

worldwide. Globally recognized

standards give consumers

confidence that their purchases

will work with compatible devices,

regardless of the brand.

How does Qi certicationwork?

We do Qi precertification for our

partners. The actual certification

is done by laboratories that are set

up to do this type of testing through

the WPC. It works out pretty nicely

because once you become certified,

they are deemed as interoperable,

and you become part of the WPC

and can put the Qi logo on your

products, just like Bluetooth or Wi-

Fi.

Can you tell us more aboutFulton Innovation and thetechnology it is developing?

Fulton Innovations goal is to

commercializing new and innovative

technologies that improve the way

we live, work, and play. Fulton

is working with a wide range of

industry-leading companies to

integrate wireless power technologyinto infrastructure and electronic

devices enabling consumers to live

a truly wireless life. Fulton Innovation

was established in 2006 to advance

wireless power technology, which

was first developed in 1998 by

parent company Alticor for its

eSpring water purification system.

The technology was further

developed, branded, and officially

launched as eCoupled technologyin 2007. Fulton licenses its eCoupled

technology to manufacturers so they

can incorporate eCoupled into their

products.

Can you tell us about theeCoupled intelligent wirelesspower project?

eCoupled technology is intelligent

wireless power based on inductive

coupling that allows for safe andefficient power transfer without

wires. eCoupled technology is

based on the principle of near-

field resonant magnetic induction.

With magnetic induction, electricity

travels via magnetic fields instead

of through a physical connection

of conductive materials like those

found in a traditional power cord.

Wireless power requires two coils:

a power supply coil (usually in a

surface or pad) and a receiving coil

(in a device). A shared or coupledelectromagnetic field is generated

when the power supply and

receiving coils are positioned near

each other, which then wirelessly

transfers power to or charges the

device.

eCoupled technology uses this

concept to eliminate the need

for power cords. It creates an

electromagnetic conduit, combined

with an intelligent control system

that constantly monitors the power

flow to ensure optimal efficiency

and safety.

How did you and FultonInnovation get involved in thisproject?

Fulton Innovation originally

developed the concept of eCoupled

wireless power in 1998 to solve a very

real problemfinding a safe way topower a UV lamp in a water purifier.

It was then that Fulton realized the

true potential of wireless power and

its broad applicability to virtually

any electronic power system. Since

then, Fulton has enhanced and

developed the technology and is

dedicated to commercializing new

and innovative implementations of

wireless power that improve the

way we live, work, and play.

How has this technology hada signicant impact on thewireless power industry?

The Qi global low-power standard,

set by the Wireless Power

Consortium (WPC), includes

elements of eCoupled technology.
http://www.wirelesspowerconsortium.com/member-list/http://www.wirelesspowerconsortium.com/member-list/

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INTERVIEW

The Qi standard ensures full

interoperability between devices

and transmitters, regardless

of brand. The Qi standard

gives consumers flexibility and

confidence in their technology

purchase. Today, there are more

than 100 Qi-certified devices on

the market worldwide and the list

is growing rapidly. Fulton, as a

founding member of the WPC, is

committed to advancing Qi as the

standard with manufacturers and

consumers to encourage wireless

power industry growth.

What Fulton Innovation clientsare using this technology?

Fultons technology has been

incorporated into scores of products

from various manufacturers

around the world. You can see

our technology in the following

products:

Amway eSpring waterpurification system

Samsung Droid Charge

Motorola Droid 3

Motorola Droid Bionic

LG Revolution

HTC Thunderbolt

HTC Rezound

HTC Incredible 2

LG Charging Pad

Pantech Breakout

Motorola Droid 4

Does your licensing involveproviding a developmentplatform for users to start usingthe eCoupled technology?

This is a new science based on

old physics. It has a new twist:

multidimensional control. This

means that we are maximizing

physics in order to adapt to varying

environmental conditions. So, when

Fulton Innovationsgoal is to

commercialize newand innovative

technologies that

improve the way welive, work, and play.

we partner with a company, it

is a true collaboration. What we

are really selling is not just a

technology; we are selling that

knowledge to bring our partners

up to speed to understand the

state-of-the-art in a particular

technological realm. We do this tocontribute to the understanding of

state-of-the-art models, tools and

equipment, space and relationships

and electromagnetic fields and

materials that help users see things

in a dynamic environment that were

not previously possible.

Our patents are a progression of that

knowledge, and our relationships

are a technology transfer ofthat knowledge into a physical

embodiment that enhances our

customers products.

Are there any certicationrequirements for productsto make sure there isnt anyinterference with the system?

There are FCC, CISPR and IEC

requirements associated with any

electronics design. What weve

done with the WPC is set up under

a specific band where we have

reference designs to meet the

considerations and requirements

that exist for various products.

With the WPC, weve actually

selected a specific frequency

range in order to be able to meet

the regulatory requirements for

SAR exposure and insure that any

products using the Qi standard

are able to pass the strictest safety

regulations. You can do some

very interesting things balancingin between ICNIRP exposure

guidelines. Our range allows us to

do everything in the power range

of automobiles all the way down to

printed electronics.

Is that safe?

Just to give you an idea, a hairdryer

generates more radiation than our

power systems.

How far away can a devicebe and still remain efcientwith power transfer?

We can do relatively huge distances

and still efficiently transfer wireless

power. In space, you could do some

very large distances. In a room with

people in it, however, you are limited

by SAR exposure and ICNIRP

guidelines. We dont like to do huge

distances in rooms because of the

exposure to humans, so we have

made a considerable effort to limit

the distance between the appliance

and the wireless power supply.

We like the distance to be inches

rather than feet. Although we have

the ability, we have still chosen to

try and limit the distances to limit

exposure.

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INTERVIEW

Are you able to designdirectional antennas tocentralize where the power isbeing transferred?

We have done some very interesting

work with shaping electromagnetic

fields. We call it selective saturation.

We can actually put a radiator in a

table and put laminate over that

table with a shielding material.

Then selectively, wherever you

place your device, the field is

opened to transfer power through

the shielding material. It is very

interesting because it allows for the

opening of virtual holes where you

want the power to be transferred.

This year at the 2012 International

Consumer Electronics Show (CES),

we showed power through metal.

We have designed an aluminum

enclosure, and you can actually

set your electronics on top of that

product and it will charge.

Do you help clients designand incorporate yourtechnology into theirproducts?

Typically, yes. However, the process

varies with each partner. Using

a cell phone manufacturer as an

example, we may or may not go

through the process of using a

license agreement because the

client company might buy the

semiconductors from another

company (e.g., Texas Instruments)

that is already a licensee of ours.The manufacturer might want to go

through the process on its own and

use parts from other companies, but

still enlist our help with the product

to make the design meet certain

specifications and standards like

size and efficiency. There also

might be additional twists to the

manufacturers desires such as

incorporating another trademarked

feature into the design.

We then work together with the

manufacturer to model, design,test, validate and make sure it is Qi

compatible with the WPC. Doing all

of these things is what allows other

companies to use our technology in

their products.

Where can the eCoupledtechnology be used?

There are almost no limits to where

eCoupled can be used. Anywhere

theres a traditional power cable,eCoupled can certainly replace

it. We have shown examples of

eCoupled in everything from kitchen

appliances to vehicles. At last years

Consumer Electronics Show, we

demonstrated wirelessly charging

a Tesla Roadster electric vehicle.

eCoupled is flexible enough to be

used in packaging or publishing.

Using printed electronics, weve

shown how wireless power canbe incorporated into packaging

(we lit a cereal box so it flashed

on a supermarket shelf), and at

CES this year well be showing

a similar example with a copy of

Entertainment Weeklythat lights up

and flashes while it sits on a stand.

Regarding the technology,what frequency do youtypically use to transmit

power?

The technology is frequency-

agnostic, which means that we

can really tune to any frequency

and utilize and maximize the

relationships between transmitters

and receivers.

We can do that dynamically at

about any frequency range, but

with the WPC we operate between

80 250kHz. We have done that

very specifically for very specific

reasons.

What are you doing froma marketing standpoint toconvince companies toincorporate this technologyinto their next devices?

Ten years ago, when we were

pitching the capabilities of wireless

power, the reactions were, Its

impossible, It cant be done.

People thought it would be

inefficient and extremely expensive.Today, while it is a robust power

supply, it is also more convenient

to the consumer--it gets rid of a top-

ten warranty and reliability issue

by eliminating cords and cables

that usually break, and it can be

designed in ways that simply

replace the current power supply

and power management at very

little additional cost, regardless of

the power level.

It has been a long road getting

the consensus and understanding

within the electronics arena. But we

have been successfully doing it with

over 100 companies in the WPC,

and are finally nearing the tipping

point where people are realizing the

value in this technology.

What is the overall target

for Fulton Innovation for thewireless power industry?

We want wireless power to become

ubiquitous. Wed like to remove the

final cable (power) so we can enjoy

a truly wireless, mobile lifestyle.

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communication is required). Microchips remote-control demo is in the form factor of a wireless remote control, but

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Wireless power is transitioning

from a technology to an industry.

Many questions ranging from whatconsumers really expect to which

technology is the safest and most

efficient solution are generating

an increasing amount of debate

as proprietary products come

to market and a wireless power

standard is introduced. As wireless

power reaches a tipping point,

it is important that developers

and consumers alike understand

the realities of the different

technological approaches

especially the safety and efficiency

concerns surrounding themand

the current and future states of the

technology as it gains momentum.

EXECUTIVE SUMMARY

Research has shown that wireless

power is one of the most attractive

new technologies to consumers.

However, there are misconceptionsin the media and the marketplace

about what consumers really expect

from the technology. In order for

the industry to fully develop and

reach mass adoption, there needs

to be a fuller understanding of the

different embodiments of wireless

power technology, as well as

clearer definitions of efficiency

(in particular, how efficiency is

measured), safety and the different

consumer embodiments of the

technology, including pad and

adapter solutions and a wireless

power specification.

Given these considerations

the viability of the technology

and the growing wireless power

industryit has become necessary

to collectively understand and

educate developers and consumers

and collaborate to create the bestavailable solution for today and

best position wireless power for its

future.

UNDERSTANDING

WHAT CONSUMERS

REALLY EXPECT

Research has shown that a desire

to simplify powering and charging

experiences and add a new level

of convenience to everyday life are

driving the consumer expectation

for wireless power. As the latest

wave of wireless power products

enter the marketplace and the

viability of the technology expands

into industry, a need to address the

understanding of wireless power

and how it will be incorporated into

Dave BaarmanDirector OfAdvanced Technologies

UnderstandingWirelessPowerPART 1

Joshua SchwanneckeResearchScientist

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TECHNICAL ARTICLE

everyday life has also arisen.

There has been a level of

misunderstanding about what

the consumer really wants and

needs. Research has shown that ifconsumers knew that an integrated

wireless power solution was going

to be offered in the future, they would

support a pad and adapter solution

today. Nearly half of consumers

surveyed indicated that they would

wait two years for a product if they

could have the technology built

into electronic devices. Still, about

one-third would be willing to buy

adapters, and about one-quarterwould buy the standalone charger

(pad) and use them until they

replace their devices with ones with

embedded technology [1].

However, this research also

indicates that there is a specific

price point that, once exceeded, no

longer makes the adaptive solution

attractive, even to early adopters.

Also, given the size of the adapter

market in light of the larger pictureof all consumer electronics and

infrastructure, it is not reasonable

to think that proprietary charging

pads and adapters are anything

more than short-term options

that will help prepare consumers

for the universal, integrated,

globally-available solution they are

expecting.

Given this understanding

of the marketplace, many

underdeveloped and divergent

thoughts have been introduced

from both the developmental and

perceived consumer points of view.

These range from broadcasting

power and charging any device,

in any position, anywhere in a

room, to leveraging near-field

solutions where devices interact

with charging hot spots built into the

surrounding infrastructure.

As the industry matures and more

specific questions and concernsaround wireless power technology

develop along with it, there is a

necessary sequence of events that

is required for mass adoption of the

technology worldwide. The first of

these is a deeper understanding

of the available technologies,

their strengths and limitations

and the importance of creating

a global standard to serve as

the most effective vehicle for theevolution of the universal wireless

power solutions that is capable of

answering the consumer demand

for a universal, integrated solution.

A simple assumption would be that

consumers want wireless power in

the same vein as Wi-Fi solutions

where power would be available

anywhere. Initially, this holds true

until the aspects of efficiency,

safety, cost and interoperabilityweigh into the equation. This then

becomes a complex consideration

of solutions. This is the underlying

reason to further discuss these

considerations, compromises and

available solutions.

THE PRIMARY

EMBODIMENTS OF

CONSUMER-READY

WIRELESS POWER

Wireless power can be transferred a

number of ways. From microwaves

and lasers, to the way Tesla did

it, to simple embodiments like

rechargeable toothbrushes--

all these methodologies have

limitations that potentially

undermine mass adoption and

commercialization. As an opening

caveat, microwave and laser-type

wireless power systems that are

typically point-to-point sources have

been excluded from this discussion.

That said, development teams are

stretching the boundaries of physics

using available components to

create systems that are able to

compete with the efficiencies of

wired solutions while offering

the conveniences of wire-free

connections. The solutions being

offered currently are based on high-

frequency broadcast, mid-range

inductive coupling or near-field

inductive coupling technologies.Other terms like magnetic

resonance may be used, but think

of this in terms of a very well-tuned

and possibly larger inductively

coupled transmitter and receiver

system that can be configured and

enabled in various ways.

Several terms are used in defining

inductive wireless power transfer,

including magnetic coupling,

where wireless power transfer

is typically near-field inductive

coupling. When discussing terms

like non-radiated energy, this would

assume magnetic coupling or, more

specifically, inductive coupling.

This can refer to both near-field and

mid-range inductive coupling. This

discussion defines these systems

as near-field and those that use a

larger primary coil for mid-range

distances as near-field, far-edge.In addition, mid-range is defined

as somewhere between one and

ten times the diameter of the

transmitting coil.

Far-field is typically radio frequency

(RF) and has a lower wavelength with

a smaller antenna and propagates

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

effectively. This discussion also

reviews the considerations of these

systems for use and integration. As

a general term, both RF and mid-

range wireless power are defined

here as broadcast power systems,

where the range invokes additional

considerations in field, susceptibility

and coverage in both radiated and

non-radiated terms. The basic term

broadcast for discussion is in a

one-to-many relationshipthat is to

say, one transmitter coil providing

power to many receiver coils. In

these broadcast relationships, the

design requires every receiver in

the system to suffer the differencefrom the most demanding

requirement on the system. This

will typically be expressed as

losses in the transmitter and

receiver. In broadcast systems, the

consideration of the one-to-many

relationship is very interesting;

however, it brings many additional

demands on both sides of the

power system. On the receiver side,

it demands that any device has theprotection and limiting of the largest

device. This places very interesting

and challenging requirements

on the receivers to manage these

voltages and power transactions.

Although technology has advanced

in DC-to-DC conversion, the

efficiency of such systems will be

challenged. Other factors include

extraneous losses in the field and

other parasitic elements. With

close proximity systems, these

can be easily managed. Each

power channel delivers only what

is requested for peak efficiency

which, in turn, limits losses.

Another key challenge is controlling

in various modes with broadcast

power. Consider the option to run as

a battery charger, power supply or

fast rate charger. A difficult problem

for the one-to-many broadcast

power system is managing powersupply interactions, as seen in

Figure 1, along with meeting the

time-dependent requirements of a

demanding power system.

It would be reasonable to think

that for most broadcast systems

the solution is one output and one

charging solution, resulting in more

waste. It is also important to point

out that batteries are typically more

forgiving than power systems. Withcloser proximity systems, scalable

power from one transmitter over

many control modes has been more

easily demonstrated. This problem

appears to be very challenging

in broadcast power and may limit

applications and interoperability.

Figure 1: The power supply management demands of a basic 45 watt laptop power supplyfrom start up charging only, power and charging.

MID-RANGE

WIRELESS POWER

Mid-range wireless power, as

defined here, is wireless power thatextends to larger areas of influence.

Mid-range wireless power is built

around the idea of using resonant

magnetic induction or near-field,

far-edge to send power between

coils across distances from

several inches to several feet. The

limitations of this concept start

with the diameter of the transmitter.

Typically, an inductive coupled

system can transmit roughly thediameter of the transmitter. With

additional tuning of the primary and

secondary Q along with impedance

matching capacitance or inductance

to achieve a matched magnetic

resonance, these distances

can be extended. To date, the

publications and experimentation

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TECHNICAL ARTICLE

show highly tuned systems that can

transmit power over substantial

distances with transmitter and

receiver diameters that are larger

than many consumer electronic

devices. This tuning and the use

of well-engineered low-loss coils

in turn allow these distances to be

extended. It should be noted that the

discussion to date has been about

extending distance and efficiency

to ratios greater than four times the

diameter of the transmitter. This

is not to say that it will necessarily

produce high efficiency, but rather

that power can be transferred at this

distance. For many, this will be moreinteresting at shorter distances

where efficiencies are higher and

suitable distances for specific

applications are gained. This

allows gains that create exciting

opportunities but again benefit the

closer proximity applications the

most by extending distances and

maintaining the highest efficiencies.

The opportunities in this range are

exciting but require additionalconsiderations.

In reviewing the case of early RF

wireless home control technologies

that attempted to leverage the same

thinking, these systems were tested

in situations where significant gaps

in coverage and limiting factors like

aluminum siding were discovered

that created additional consumer

confusion and cost. Imagine these

power transfer coils on the insidewall of a house with aluminum

siding. This places a large coil

within six inches of a metal surface.

This is not an easy solution as the

screen that holds plaster or stucco

would present the same challenges

to an RF-based power solution.

Broadcast wireless power faces the

same probable set of challenges,

the most significant of which is

consumer education. Today, this

technology has been presented in a

way that appears to be magic while

the real comparisons will be made

by the designers of future products.

Wireless-powered devices can be

very finely tuned and operate at

specific frequencies. If a device,

printed circuit, semiconductor or

wire circuit happen to be tuned

to these frequencies, they will

suddenly develop a potential from

the power being broadcasted. This

opens up channels of interferencethat threaten efficiencies as well as

functionality, creating usage issues

for consumers. And, as distances

between power sources and

devices increase, these issues are

amplified beyond simple shielding

solutions. Additionally, wireless

power in larger areas may present

susceptibility and compatibility

issues with devices. This may

create a need for regulation and

standardization that would require

new levels of testing and design

for devices to prevent additional

reliability and warranty failures.

Potential susceptibility failures

can be immediate or latent failure

modes.

In reviewing the claims of non-

radiated energy by some, one

could see how it is more directed

as in magnetic fields, but a specificenergy is still present at the transmit

frequency within that field. This is

typically strongest between these

coils. It should be noted that this

can be minimized but a component

of radiated and non-radiated energy

will be present.

Orientation provides yet another

challenging factor for broadcast

power as distance increases. With

this, consideration must be given

to not only the physical orientation

and alignment between the

specific transmitter and receiver,

but also orientation and alignment

in conjunction with other bodies

of various materials that fall within

the broadcast field. If this condition

happens to restrict the field

completely, the consumer is left with

a dead spot. These circumstances

will change performance and

operation unless the system can

adjust and respond accordingly.

This becomes even more importantwhen considering efficiencies in

a highly tuned system. Adaptive

intelligent solutions can provide

gains in performance when facing

these issues. However, if adaptive

intelligence is not built into systems

at the outset, the system risks

potential technology failures and

reduced consumer confidence.

In addition to tuning and orientation

challenges, mid-range wireless

power solutions face coil geometry

factors that should also be

considered. The laws of physics

have proven that well-matched coils

provide the best power transfer.

Referencing a recent paper by

researchers at Koninklijke Philips

Electronics N.V., one can see the

possible practical applications

using these methods [2]. All

efficiencies referenced in thefollowing efficiencies section of this

paper also consider tightly matched

transmitter and receiver coils.

Subsequent demonstrations have

been realized with vastly different

ratios from the transmitter diameter

to receiver diameter. It should be

pointed out that these efficiencies

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

may follow some portion of these

ratios. This may further degrade

the efficiency references provided

below for these systems as these

ratios are changed from the

mentioned efficiency. The example

that follows uses a transmitter and

receiver each with a 25cm coil, and

this system demonstrates an AC

system efficiency of 15 percent.

By changing the receiver coil

from 25cm to 25mm (a typical size

needed for a handheld device)

there should be a negative impact in

efficiency. It would also be expected

that any change in coil size would

negatively impact tuning, so thissystem would need to be highly

tuned as the system changes. Given

these variables, there is opportunity

for more system inefficiency at the

system level when considering

interoperability than has been

communicated previously.

Another consideration with mid-

range wireless power systems is

power control. When powering a

laptop, a headset and cell phone,

the power transmitted must be

tailored to the highest demand. The

other devices must be designed

to either accommodate this input

amplitude or other tradeoffs must

be made. This represents yet

another opportunity for losses,

leading to overall lower efficiency

and potentially greater thermal

dissipation in the device. This

also represents additional designconsiderations and protections

for smaller devices that already

struggle to reach their high level of

integration.

Appendix

1. AcuPOLL Research, Inc.,

August 2008 Project Alamo

River

2. Eberhard Waffenschmidt and

Toine Staring, Limitation of in-

ductive power transfer for con-

sumer applications, Submittedas synopsis to European Power

Electronics (EPE) Conference

2009, Barcelona, Spain, 8-10

September, 2009.

3. AIP Industrial Physics Forum

(November 13, 2006). Retrieved

from: http://powercastco.com/

PDF/HarvesterDataSheetv2.pdf

4. Aristeidis Karalis,

J.D.Joannopoulos, and MarinSoljacic (2006). Wireless Non-

Radiative Energy Transfer.

5. AIP Industrial Physics Forum

(November 13, 2006). Retrieved

from: http://powercastco.com/

PDF/HarvesterDataSheetv2.pdf

6. Hadley, Franklin (Version from

November 19, 2008).Retrieved

from: http://web.mit.edu/isn/

newsandeven ts /wire less_power.html




sumer applications, Submitted

as synopsis to European Power



September, 2009.

8. Hadley, Franklin (Version fromNovember 19, 2008). Retrieved

from: http://web.mit.edu/isn/

newsandeven ts /wire less_

power.html

9. Intel Labs (Accessed Octo-

ber 2009). Wireless Resonant

Energy Link. Retrieved from:

http://seattle.intel-research.net/

research.php#wrel



ductive power transfer for con-sumer applications, Submitted

as synopsis to European Power



September, 2009.

11. http://www.ecoupled.com




sumer applications, Submittedas synopsis to European Power



September, 2009.

13. http://www.wirelesspowercon-

sortium.com

14. Aristeidis Karalis,

J.D.Joannopoulos, and Marin

Soljacic (2006). Wireless Non-

Radiative Energy Transfer.

About the Authors

DAVID W BAARMAN

David Baarman is the Director of

Advanced Technologies at Fulton

Innovation and the lead inventor

of eCoupled intelligent wireless

power technology. Mr. Baarman

is responsible for the technical

supervision and development ofeCoupled technology and other

Fulton Innovation technologies. Mr.

Baarman joined Amway in 1997,

where he first pioneered the use of

intelligent inductive coupling in the

eSpring Water Purifier. With over

20 years of leadership experience in

the development of consumer and
http://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://seattle.intel-research.net/research.php#wrelhttp://seattle.intel-research.net/research.php#wrelhttp://www.ecoupled.com/http://www.wirelesspowerconsortium.com/http://www.wirelesspowerconsortium.com/http://www.wirelesspowerconsortium.com/http://www.wirelesspowerconsortium.com/http://www.ecoupled.com/http://seattle.intel-research.net/research.php#wrelhttp://seattle.intel-research.net/research.php#wrelhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://web.mit.edu/isn/newsandevents/wireless_power.htmlhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdfhttp://powercastco.com/PDF/HarvesterDataSheetv2.pdf

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

industrial products, Mr. Baarman

took the technology behind eSpring

and developed it to power everyday

technologies, including consumer

electronics, with a diverse range

of power needs. Mr. Baarmans

efforts have led to national and

global recognition of eCoupled

technology and the acquisition of

former competitor, Splashpower, in

May 2008. Mr. Baarman has more

than 700 U.S. and foreign patents

that are granted or pending.

JOSHUA SCHWANNECKE

Joshua Schwannecke is a Research

Scientist with the Advanced

Technologies Group at Fulton

Innovation. Josh has more than fiveyears of experience with wireless

power and developing solutions

using eCoupled technology. He has

developed wireless power solutions

for the Amway eSpring Water

Purifier and other devices including

hearing aids, phones, headsets,

laptops, and power tools. He also

works closely with Fultons partner

companies to research wireless

power solutions for prototype

products. Mr. Schwannecke holds

a Masters in Electrical Engineering

from Michigan State University and

has received an excellence award

for coil design and optimization. He

holds one granted patent and has

eight published patent applications.
http://bit.ly/nKLRXohttp://bit.ly/nKLRXohttp://bit.ly/nKLRXohttp://bit.ly/nKLRXohttp://bit.ly/nKLRXohttp://bit.ly/nKLRXohttp://bit.ly/nKLRXo

7/31/2019 Eeweb Pulse 2012 40

17/24

60V Fault Protected, 3.3V to 5V, 20V Common Mode

Range, RS-485/RS-422 Transceivers with Cable Invert

and 15kV ESD

ISL32450E, ISL32452E, ISL32453E, ISL32455E, ISL32457EThe ISL32450E through ISL32457E are 3.3V to 5V powered, fault

protected, extended common mode range differential transceivers

for balanced communication. The RS-485 bus pins (driver outputs

and receiver inputs) are protected against overvoltages up to

60V, and against 15kV ESD strikes. These transceivers operate

in environments with common mode voltages up to 20V

(exceeds the RS-485 requirement), making this RS-485 family

one of the more robust on the market.

Transmitters are RS-485 compliant with VCC 4.5V and deliver a

1.1V differential output voltage into the RS-485 specified 54

load even with VCC = 3V.

Receiver (Rx) inputs feature a Full Fail-Safe design, which

ensures a logic-high Rx output if Rx inputs are floating, shorted, or

on a terminated but undriven (idle) bus. Rx full fail-safe operation

is maintained even when the Rx input polarity is switched (cable

invert function on ISL32457E).

The ISL32457E includes a cable invert function that reverses the

polarity of the Rx and Tx bus pins in case the cable is

misconnected during installation.

See Table 1 on page 2 for key features and configurations by

device number.

Related Literature

See FN7784, ISL32470E, ISL32472E, ISL32475E,ISL32478E: Fault Protected, Extended Common Mode Range,

RS-485/RS-422 Transceivers with 16.5kV ESD

Features Fault Protected RS-485 Bus Pins. . . . . . . . . . . . . Up to 60V

Extended Common Mode Range . . . . . . . . . . . . . . . . . . 20V

Larger Than Required for RS-485

15kV HBM ESD Protection on RS-485 Bus Pins

Wide Supply Range . . . . . . . . . . . . . . . . . . . . . . . . . 3V to 5.5V

Cable Invert Pin (ISL32457E Only)

Corrects for Reversed Cable Connections While Maintaining Rx

Full Fail-safe Functionality

1/4 Unit Load for Up to 128 Devices on the Bus

High Transient Overvoltage Tolerance. . . . . . . . . . . . . . 80V

Full Fail-safe (Open, Short, Terminated) RS-485 Receivers

Choice of RS-485 Data Rates . . . . . . . . . . . . 250kbps or 1Mbps

Low Quiescent Supply Current . . . . . . . . . . . . . . . . . . . 2.1mA

Ultra Low Shutdown Supply Current . . . . . . . . . . . . . . . 10A

Pb-Free (RoHS Compliant)

Applications Utility Meters/Automated Meter Reading Systems

Air Conditioning Systems

Security Camera Networks

Building Lighting and Environmental Control Systems

Industrial/Process Control Networks

FIGURE 1. EXCEPTIONAL ISL32453E RX OPERATES AT >1Mbps

EVEN WITH 20V COMMON MODE VOLTAGE

FIGURE 2. TRANSCEIVERS DELIVER SUPERIOR COMMON MODE

RANGE vs STANDARD RS-485 DEVICES

TIME (200ns/ DIV)

VO

LTAGE(V)

0

5

10

15

20

B

A

RO

VCC = 3V

VID = 1V2Mbps

ISL3245XE

COMMO

N

MODERANGE(V)

STANDARD RS-485TRANSCEIVER

-20

-7

0

12

20

February 20, 2012

FN7921.0

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2012

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

Get the Datasheet and Order Samples

http://www.intersil.com
http://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhBhttp://bit.ly/nHxRhB

7/31/2019 Eeweb Pulse 2012 40


Combining the operation of a boost regulator and a

negative voltage converter can generate a negative

supply from a single low-voltage supply. The circuitin Figure 5 shows a standard application circuit for a

+20V supply along with two op amps, two diodes and

two capacitors to generate the 20V supply. This article

will discuss the basic operation of a boost converter to

generate a larger positive supply voltage. Equations

are derived to determine the minimum inductor value to

maintain a safe peak inductor current, and a maximum

inductor value to maintain continuous conduction mode

(CCM) operation. The article will then discuss the

generation of a negative supply and the restrictions of

the design.

Understanding the Boost Topology:

Before we add the additional circuitry to generate the

negative supply, it is important to understand how the

boost convertor produces an output voltage that is

always greater than the input voltage. In order to do this,

we analyze the boost circuits in Figure 1 and the current

waveforms in Figure 2. For this analysis, we account

for all the losses in the charging and discharging loops

in our equations. This should help to give a complete

understanding of the circuit.

However, the output voltage is not dependent upon any

losses in the circuit. This is because all the losses are

inside the circuits feedback loop of the ISL97701which

we will use as an example hereand are automatically

accounted for. The output voltage is defined from

the feedback resistor network shown in Figure 5 and

calculated in Equation 1, where VrefFB is the internal

reference voltage of the ISL97701.

( )

.( )

( )

V V

R

R R

V VR

R R1 15 1

OUT refFB

OUT

2

1 2

2

1 2

:

:

=+

=+

Positive Supply:

Figure 6a shows the basic boost converter circuit.

During one switching cycle, the transistor Q1 turns on

and turns off. During the time Q1 is on, the inductor

L1 is placed in series with the VIN supply through the

Don LaFontaineSenior Application Engineer

A Simple Circuit to GeneratePlus and Minus Supplies

Using a Boost Regulator

+++

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

ISL97701s integrated boost FET (Q1). The diode D1 is

reverse biased and the circuit reduces to that shown in

Figure 6b. The voltage across the boost inductor (L1)

is equal to VIN (VDS + IL1 x RL1) and the current

ramps up linearly in inductor L1 to a peak value at time

DT. Thepeak inductorcurrent (IL1) is calculated in

Equation 3 and shown graphically in Figure 6b. Any

load requirements during this phase are supplied by the

output capacitor C1.

The duty cycle (D) in Equation 5 is determined by setting

the losses in Equation 5 (IL1 x RL1, VD1, VDS) to zero

because they are within the feedback loop of the ISL97701.

The ISL97701 varies the duty cycle continuously to keep

Figure 1

V Ldtdi

iLV

dt ( )2LL

LpkL

T

DT

0

= = #

When Q1 turns off, because the current in an inductor

cannot change instantaneously, the voltage in L1 reverses

and the circuit becomes that shown in Figure 1c. Now the

no-dot end of L1 is positive with respect to the dot end

and D1 becomes forward biased. Because the dot end is

at VIN, L1 delivers its stored energy to C1 and charges it

up to a higher voltage than VIN. This energy supplies the

load current and replenishes the charge drained away

from C1. During this time, energy is also supplied to the

load from VIN. The voltage applied to the dot end of the

inductor is (VIN IL1 x RL1), while the voltage applied

to the no-dot end of L1 is now the output voltage (VO)

plus the diode forward voltage (VD). The voltage across

the inductor during the off-state is ((VO + VD1 + IL1 x

RL1) VIN). The inductor current during the off-time of

the switch (T-DT) is calculated in Equation 4 and shown

graphically in Figure 1c.

IL

V (V I R )DT ( )3L1(on)

IN DS L1 L1=

- + ##D

IL

(V V I R ) V(T DT) ( )4L1(off)

o D1 L1 L1 IN=

+ + --

##D

In steady-state conditions, the current increases during

the on-time of the switch and decreases during the off-time of the switch (Figure 7). Both on-time and off-time

currents are equal to prevent the inductor core from

saturating. Setting both currents equal to each other

and solving for VO results in the continuous conduction

mode boost voltage shown in Equation 5.

V1 D

V I R )V V

1 DD

( )5oin L L

D1 DS= -

-- -

-

##

Figure 2

RL1

IL1

RL

L1 D1

Q1C1

IO

VIN

VDS

+

VO

RL1

IL1

IQ1

L1

(VO+VD+IL1xRL)VIN(T-DT)

L

Q1VIN+

RL1

IL1

RL

L1 D1

DT

DTOT

T

VO

C1

VIN+

IO

a

b

a

b

IL1(of f) =

(VIN(VDS+IL1xRL1))DT

L

IL1(on) =

DTOT

IL1

IL1

IL1(pk)

IL1(a ve)

ID1

IQ1

OT DT T

OT DT T

OT DT T

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

VO constant, regardless of the conduction losses as

a function of load current. With the losses set to zero,

Equation 5 reduces to Equation 6. This results in the

value for the duty cycle shown in Equation 7.

the output current multiplied by the gain of the boost

regulator as shown in Equation 10.

VV

1 D1 ( )6

IN

O=

-

D 1V

V( )7

O

IN= -

Inductor Selection

The inductor selection determines the output ripple

voltage, transient response, output current capability

and efficiency. Its selection depends on the input

voltage, peak inductor current, output voltage, switching

frequency and maximum output current. When choosing

an inductor, make sure the saturation current of theinductor is greater than the IPEAK of the circuit. Likewise,

the transistor should be able to handle peak current

greater than IPEAK. The peak inductor current is shown

in Figure 10 and can be calculated using Equation 11.

Figure 3

From Figure 3, we can see that the peak inductor current

IL1 is equal to the average inductor current IL1 plus one

halftheIL1current,asshowninEquation8.

I I21

I ( )8L1(PEAK) L1(AVE) L1(ON)= + D

The average power IN is equal to the average power

OUT divided by the efficiency of the circuit, as shown inEquation 9.

V IEff

V I( )9IN L1 (AVE)

O O=##

Where Eff is equal to the efficiency of the ISL97701 boost

regulator.

Therefore, the average inductor current is equal to

IV Eff

V I( )10L1(AVE)

IN

O O=#

#

IL1wasdefinedinEquation3andthedutycycle(D)

in Equation 7. Substituting Equation 7 into Equation

3 and adding it to Equation 10 results in Equation 11.

Equation 11 gives the inductors peak current in terms of

input voltage, output voltage, switching frequency, and

maximum output current (again, the losses due to VDS

and IL1 x RL1 are not included because they are inside

the feedback loop of the ISL97701).

IV Eff

V I1/2

L V FREQ

V (V V )( )11L(PEAK)

IN

O O

O

IN O I N+

-

=#

#

#

# #

#

By rearranging the terms in Equation 11, we can solve

for the inductor value using Equation 12.

L(I V Eff I V )2V FREQ

V Eff (V V )( )12

PK IN O O O

IN2

O IN

-

-

=

Equation 12 is useful for determining the minimum

value of L that the circuit can handle without exceeding

the peak current through the inductor, and therefore the

switch Q1. The maximum peak current (IPEAK) allowed

through Q1 for safe operation is given in the electricaltable as 1.2A.

Minimum Inductor Value Design Example

Given: VIN = 5V, VO = 20V, IO = 50mA, IPK = 1.2A, freq

= 1MHz, Eff = 0.85 (Efficiency of 85% from Figure 3 in

the ISL97701 data sheet).

Equation 12 gives us the boundary condition for the

smallest inductor we can have to ensure the peak

current through Q1 is less than the max limit of 1.2A.

The minimum inductor value for the given conditions isdetermined to be 1.94H.

1.94 H ( )13= n

L(1.2A (5)(0.85) 50mA(20)) 2 (20) 1MHz

(5V) (0.85)(20 5)2

-

-

=

Maintaining CCM Design Example

For maximum efficiency, the boost converter needs to

IL1

IL1

IL1(pk)

IL1(a ve)

O DT T

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

Negative Supply

The operation of the negative supply is best understood

by considering Figure 5. We will start our analysis

under steady state conditions (the inductor operating

in continuous conduction mode and C1 is equal to thevoltage calculated in Equation 1).

When Q1 turns off, the inductor voltage flies up turning

on D1 and D3. Diode D2 is blocking current flow from

C3. The inductor current now charges both capacitors

C1 and C2 with the polarity shown in Figure 5. The

voltage on C2 is equal to the voltage on C1 plus the

forward voltage drop of D1.

When Q1 turns on, Diodes D1 and D3 are blocking and

capacitor C2 is now in parallel with capacitor C3 through

D2 (which is now on), as seen in Figure 4. This connectionresults in a negative voltage being transferred on to C3.

The voltage transferred to C3 is equal to the voltage on

C1 as shown in Figure 4 and Equation 18.

be operated in continuous conduction mode (CCM). To

maintain continuous conduction mode operation of the

boost regulator, the value of IL1 needs to be greater than

orequaltoIL1/2(Figure3).

I21 I

V Eff

V I1/2

L V FREQ

V (V V( )14

L1(AVE) L1

IN

O O

O

IN O IN)-

#

#

#

# #

#

$

$

D

Rearranging terms and solving for L results in Equation

15.

L 1/2

V Eff

V IV FREQ

V (V V )(15)

IN

O OO

IN O IN-

#

#

#

# #

#

$

To maintain continuous conduction mode operation for

the given circuit design conditions above, the value of L

has to be greater than 7.96H.

L 1/2

5V (0.85)

20V 50mA20 1MHz

5V (20V 5V)-#

#

#

# #

#

$

7.96 H ( )16$ n

It should be noted that when there is a light load, the circuit

can slip into discontinuous conduction mode, where the

inductor becomes fully discharged of its current each

cycle. This operation will reduce the overall efficiency

of the supply. Using Equation 15 and making the value

of the inductor large enough for a given minimum

output current will ensure continuous conduction mode

operation.

Output Capacitor

Low ESR capacitors should be used to minimize the

output voltage ripple. Multilayer ceramic capacitors

(X5R and X7R) are preferred for the output capacitors

because of their lower ESR and small packages.Tantalum capacitors with higher ESR can also be used.

The output ripple can be calculated in Equation 17:

Vf C

I DI ESR ( )17O

SW 1

OUT

OUT=#

#

#D +

For noise sensitive applications, a 0.1F placed in

parallel with the larger output capacitor is recommended

to reduce the switching noise.

Figure 4

The efficiency of the charge transfer between the

two capacitors is related to the energy lost during this

process. Energy is lost only in the transfer of charge

between capacitors if a change in voltage occurs. Theenergy lost is defined in Equation 19:

(V D ) D V 0

V V

( )18C1 1 2 C3

C1 C3

+ - - =

=

E21

C (V V ) ( )192 12

2

2-=

Where V1 and V2 are the voltages on C2 during the

charging and transfer cycles. If the impedances of

C2 and C3 are relatively high at the 1MHz frequency

compared to the value of RL, there will be substantial

+

+

+

C2

V = VC1 +D1

Q1 turns on connecting

C2 to ground as shown

VC3

C3

C1

D1

D2

7/31/2019 Eeweb Pulse 2012 40


TECHNICAL ARTICLE

difference in the voltages V1 and V2. Therefore it is

not only desirable to make C3 as large as possible to

eliminate output voltage ripple, but also to employ a

correspondingly large value for C2 in order to achieve

maximum operation efficiency.

Output Voltage Regulation Using Op Amps

The final output voltage regulation is accomplished

using the ISL28208 Dual Opamp. The voltage developed

by the boost converter powers the amplifiers and the

output voltage is calculated using Equations 20 and 21.

currents between 25mA and 125mA. The circuit will

work perfectly fine outside these ranges, as long as the

maximum IPEAK current is not exceeded (Equation 12).

The only drawback will be a reduction in the efficiency

of the circuit. The percent efficiency could drop fromthe 80s to the 60s as the operation goes from continuous

conduction mode to discontinuous conduction mode.

Reference the ISL97701 data sheet for additional

information on performance.

About the Author

Don LaFontaine is a Sr. Principal Application Engineer/

Sr. Engineering Manager with Intersils Analog/Mixed

Signal product line in Palm Bay, Florida. His focus is on

precision analog products. He has been with Intersil

Corp. for the last 30 years. He graduated from theUniversity of South Florida with a BSEE in 1985.

V 5V (R R ) /R ( )20OUT(positive) 3 4 3:= +

V V R /R ( )21OUT (negative) OUT (positive) 6 5= :-

Restriction On DesignFor reasonable voltage regulation of the negative supply

voltage, the negative supply current needs to be less than

or equal to the positive supply current. This is because

the control loop for output voltage regulation is around

the positive supply voltage only.

I I ( )22OUT(positive) OUT(negative)$

The ISL97701 is optimized to work best for a small

range of inductors. The slope compensation ramp

generator, inside the ISL97701, is optimized for inductorvalues between the range of 4.7H to 15H and output

Figure 5

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C2

C3

C1

C0

VOUT(positive)

VOUT

FB

ISL97701

ISL28108

ISL28108

VDDOUT

VDD

NEN

NSYNC

GND

LX20V

VOUT(negative)

- 20V

4.7F6.8H

4.7F

4.7F

R1383k

R2

R3

22.2k

33.2k

R4

100k

R5

100k

R6

100k

5F

- 20.99V

5V

5V

V+

V

V+

V

5V

20.99V

L1

Q1

D2

D1 V0

D3

+

+

+

+

+

O

SCILLATOR

AN

DCONTROL
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