EEWeb Pulse - Volume 40

PULSE EEWeb.comIssue 40

April 3, 2012

Dave BaarmanFulton Innovation

Electrical Engineering Community

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TABLE O

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Dave Baarman 4FULTON INNOVATION

Featured Products 9Understanding Wireless Power - Part I BY DAVE BAARMAN AND JOSHUA SCHWANNECKE WITH FULTON INNOVATION

A Simple Circuit to Generate Plus 18 And 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, it’s important 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 negative voltages within your circuit.

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Fulton Innovationwater treatment system to eliminate 6-log reduction or 8-log reduction of 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 highly resonant 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 about the 400 patents you hold in wireless power technology? We began developing the water treatment 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 haven’t stopped since. Actually, as it sits

Dave Baarman

Dave Baarman - Director of Advanced Technologies

How did you get into electrical engineering and when did you 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 development—my first job was actually in automotive research and development.

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


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right now, we have a portfolio of over 700 patents pending or granted in just the wireless power space.

Can you tell us about being a founding member of the Wireless 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, and infrastructure 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 believe that 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 certification work?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 about Fulton Innovation and the technology it is developing?Fulton Innovation’s 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 technology into 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 technology in 2007. Fulton licenses its eCoupled technology to manufacturers so they can incorporate eCoupled into their products.

Can you tell us about the eCoupled™ intelligent wireless power project? eCoupled technology is intelligent wireless power based on inductive coupling that allows for safe and efficient 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 coupled electromagnetic 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 Fulton Innovation get involved in this project? Fulton Innovation originally developed the concept of eCoupled wireless power in 1998 to solve a very real problem—finding a safe way to power 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 had a significant impact on the wireless 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/


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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 clients are using this technology? Fulton’s 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 water purification 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 involve providing a development platform for users to start using the 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 Innovation’s goal is to

commercialize new and innovative

technologies that improve the way we live, 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 to contribute 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 of that knowledge into a physical embodiment that enhances our customers’ products.

Are there any certification requirements for products to make sure there isn’t any interference with the system?There are FCC, CISPR and IEC

requirements associated with any electronics design. What we’ve 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, we’ve 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 balancing in 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 device be and still remain efficient with 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 don’t 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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Are you able to design directional antennas to centralize where the power is being 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 design and incorporate your technology into their products?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

manufacturer’s 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 eCoupled technology be used? There are almost no limits to where eCoupled can be used. Anywhere there’s a traditional power cable, eCoupled can certainly replace it. We have shown examples of eCoupled in everything from kitchen appliances to vehicles. At last year’s 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, we’ve shown how wireless power can be incorporated into packaging (we lit a cereal box so it flashed on a supermarket shelf), and at CES this year we’ll be showing a similar example with a copy of Entertainment Weekly that lights up and flashes while it sits on a stand.

Regarding the technology, what frequency do you typically 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 from a marketing standpoint to convince companies to incorporate this technology into their next devices?Ten years ago, when we were pitching the capabilities of wireless power, the reactions were, “It’s impossible,” “It can’t 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 the wireless power industry? We want wireless power to become ubiquitous. We’d like to remove the final cable (power) so we can enjoy a truly wireless, mobile lifestyle. ■

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DRC/AGC is also configured to protect the speaker from damage at high power levels and compress the dynamic rangeofmusictofitwithinthedynamicrangeofthespeaker.TheTPA2029D1iscapableofdriving3Wat5Vinto4Ωloador880mWat3.6Vinto8Ωload.Thedevicefeaturesanenablepinandalsoprovidesthermalandshortcircuitprotection. For more information, please click here.

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becoming more prevalent, as they provide bi-directional communication and work through walls (no line-of-sight communication is required). Microchip’s remote-control demo is in the form factor of a wireless remote control, but it can also be used as a reference design to build any type of application that requires a graphical display, touch sensing, USB and/or wireless capability. The demo is supported by free source code that customers can use to customize for various graphical screens or touch-button scenarios. The MRF24J40 transceiver can be used with the 2.4 GHz RF4CE, ZigBee® or MiWi™ protocols, depending upon the wireless needs of the end application. The demo showcases how a vivid color display application can use a low cost PIC24 MCU with integrated graphics driver, utilizing only the on-chip RAM to eliminate the cost of external memory.For more information, please click here.

Demo Board - Touch, USB and WirelessMicrochip Technology Inc., a leading provider of microcontroller, analog and Flash-IP solutions, announced the availability of its Remote Control Demo Board, which integrates graphics, touch sensing, USB, and wireless communications (ZigBee® RF4CE). The board demonstrates a remote control populated with a PIC24FJ256DA210 MCU, 3.5” graphical TFT LCD display with resistive touch screen, capacitive touch keys with plastic overlay, MRF24J40 2.4 GHz transceiver and ZENA™ wireless adapter. Many consumer products now feature colorful graphical displays and touch capability. And, RF-based remote controls are

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Wireless power is transitioning from a technology to an industry.Many questions ranging from what consumers 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 them—and 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 misconceptions in 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 industry—it has become necessary

to collectively understand and educate developers and consumers and collaborate to create the best available 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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everyday life has also arisen.

There has been a level of misunderstanding about what the consumer really wants and needs. Research has shown that if consumers 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-quarter would 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 picture of 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 concerns around 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 the evolution 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 interoperability weigh 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


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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 relationship—that 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 difference from 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 the protection 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 power supply 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. With closer 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 supply from start up charging only, power and charging.

MID-RANGE WIRELESS POWER

Mid-range wireless power, as defined here, is wireless power that extends 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 the diameter 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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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 more interesting 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 additional considerations.

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 inside wall 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 interference that 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 specific energy 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 important when 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 the following 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


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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 this system 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 design considerations 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,” Submitted as 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 Marin Soljacic (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/newsandevents /wi re less_power.html

7. Eberhard Waffenschmidt and Toine Staring, “Limitation of in-ductive power transfer for con-sumer applications”, Submitted as synopsis to European Power Electronics (EPE) Conference 2009, Barcelona, Spain, 8-10 September, 2009.

8. Hadley, Franklin (Version from November 19, 2008). Retrieved from: http://web.mit.edu/isn/newsandevents /wi re less_power.html

9. Intel Labs (Accessed Octo-ber 2009). ”Wireless Resonant Energy Link.” Retrieved from:

http://seattle.intel-research.net/research.php#wrel


11. http://www.ecoupled.com


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 of eCoupled 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.pdf




http://web.mit.edu/isn/newsandevents/wireless_power.html








http://www.ecoupled.com/

http://www.wirelesspowerconsortium.com/

http://www.wirelesspowerconsortium.com/


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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. Baarman’s 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 five years 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 Fulton’s 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/nKLRXo

±60V Fault Protected, 3.3V to 5V, ±20V Common Mode Range, RS-485/RS-422 Transceivers with Cable Invert and ±15kV ESDISL32450E, 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 54Ω 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 . . . . . . . . . . . . . . . . . . ±20VLarger 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 . . . . . . . . . . . . . . . . . . . 2.1mAUltra Low Shutdown Supply Current . . . . . . . . . . . . . . . 10μA

• 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)

VOLT

AG

E (V

)

0

5

10

15

20B

A

RO

VCC = 3V

VID = ±1V2Mbps

ISL3245XE

CO

MM

ON

MO

DE

RA

NG

E (V

)

STANDARD RS-485 TRANSCEIVER

-20

-7

0

12

20

February 20, 2012FN7921.0

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


Combining the operation of a boost regulator and a negative voltage converter can generate a negative supply from a single low-voltage supply. The circuit in 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 circuit’s feedback loop of the ISL97701—which we will use as an example here—and 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 VR

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 SuppliesUsing a Boost Regulator

++++ – – ––


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ISL97701’s 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. The peak inductor current (ΔIL1) is calculated inEquation 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 L dtdi i L

V 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.

I LV (V I R )

DT ( )3L1(on)IN DS L1 L1=- + #

#D

I L(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.

V 1 DV I R )

V V 1 DD

( )5oin L L

D1 DS= --

- - -#

#

Figure 2

RL1

IL1

RL

L1 D1

Q1 C1

IO

VIN

VDS

+

–

VO

RL1

IL1

IQ1

L1

(VO+VD+IL1x RL)– 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+IL1x RL1))DT

L∆ IL1(on) =

DTOT

∆ IL1

IL1

IL1(pk)

IL1(a ve)

ID1

IQ1

OT DT T

OT DT T

OT DT T


TECHN

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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

( )6IN

O = -

D 1 VV

( )7O

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 the inductor 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 halftheΔIL1current,asshowninEquation8.

I I 21 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 in Equation 9.

V I EffV 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 EffV I

( )10L1(AVE)IN

O O=#

#

ΔIL1wasdefinedinEquation3andthedutycycle(D)in Equation 7. Substituting Equation 7 into Equation 3 and adding it to Equation 10 results in Equation 11. Equation 11 gives the inductor’s 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 EffV I 1/2

L V FREQV (V V )

( )11L(PEAK)IN

O O

O

IN O IN+

-=

#

##

# #

#

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 electrical table 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 is determined to be 1.94μH.

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

(5V) (0.85)(20 5)1.94 H ( )13

2

-

-= = n

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

(5V) (0.85)(20 5)1.94 H ( )13

2

-

-= = n

Maintaining CCM Design Example

For maximum efficiency, the boost converter needs to

∆ IL1

IL1

IL1(pk)

IL1(a ve)

O DT T


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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 the voltage 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 connection results 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 orequaltoΔIL1/2(Figure3).

I 21 I

V EffV I 1/2

L V FREQV (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 EffV I V 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 7.96μH.

L 1/2

5V (0.85)20V 50mA 20 1MHz

5V (20V 5V)7.96 H ( )16

-#

#

## #

#

$ $ n

L 1/2

5V (0.85)20V 50mA 20 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 CI D I ESR ( )17OSW 1

OUTOUT=

#

##D +

For noise sensitive applications, a 0.1μF 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. The energy lost is defined in Equation 19:

(V D ) D V 0V V

( )18C1 1 2 C3

C1 C3

+ - - =

=

E 21 C (V V ) ( )192 1

22

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 connectingC2 to ground as shown

VC3

C3

C1

D1

D2


TECHN

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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 from the 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 Intersil’s 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 the University 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 Design

For 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 inductor values between the range of 4.7μH to 15μH and output

Figure 5

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C2

C3

C1

C0

VOUT(positive)

VOUT

FB

ISL97701

ISL28108

ISL28108

VDDOUT

VDD

NEN

NSYNC

GND

LX 20V

VOUT(negative)

- 20V

4.7µF6.8µH

4.7µF

4.7µF

R1383kΩ

R2

R3

22.2kΩ

33.2kΩR4

100kΩ

R5

100kΩ

R6

100kΩ

5µF

- 20.99V

5V

5V

V+

V–

V+

V–

5V

20.99V

L1

Q1

D2

D1 V0

D3

+

–+

+

+

+

–

–

–

–

OSC

ILLA

TO

RA

ND

CO

NT

ROL

http://bit.ly/jd6Wcw


RETURN TO

ZERORETURN TO ZERO


RETURN TO

ZERORETURN TO ZERO

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