Wireless power for charging mobile devices

Wireless power has become a hot topic as wireless charging of mobile devices is get getting some popularity. Wireless charging isn’t something new; the technology exists since 1981 and Nikola Tesla has made first wireless power experiments over 100 years ago. Wireless charging for Qi technology is becoming the industry standard on smartphones (pushed by Wireless Power Consortium) as Nokia, HTC and some other companies use that. There is a competing AW4P wireless charging standard pushed by Samsung ja Qualcomm. And there is more standards coming. Power Matters Alliance is heavily pushing their own wireless charging standard. It seems there is going to be fight on wireless charging in near future. It seems that right now we’re in the midst of a battle between two standards for wireless charging – Qi from the Wireless Power Consortium and Power 2.0 from the Power Matters Alliance. It seems that a common Wireless Power Standard Years Off as Battle Heats Up.

As obviously useful as wireless charging is, it suffers from a Tower of Babel problem with incompatible standards and competing interests keeping it from truly going mainstream. Wireless charging continues to be a niche category until there’s a common standard. Heavyweights are backing the idea of wireless charging capabilities embedded in phones, and public charging stations are beginning to pop up. Differing standards, however, still make for a rocky adoption. Realistically there probably isn’t room for two or more standards, which do essentially the same to end user but are incompatible, so expect some technologies to disappear in the near future. Charging portable devices without needing to carry a power adapter sounds handy when we can agree on one standard. “Wireless charging continues to be a niche category until there’s a common standard,” said Daniel Hays, a consultant with PricewaterhouseCoopers. “The hassle factor is still high.”

Qi seems to be at the moment standard that gets most attention. The news that Nokia to join Qi party with wireless-charging Lumia 920 have given lots of publicity to it. Even if the Lumia isn’t a big seller, the publicity and visibility it will provide for Qi should be enough to make everyone forget there was ever an alternative, if indeed there ever was. Also some HTC phones and Nexus 4 phone use this standard. Toyota launches the world’s first wireless charging of mobile phones in the car. Toyota’s car will get wireless mobile phone charger using Qi standard.

Qi has been here for some years. Qi has been around for a while, gaining the name and logo back in 2009. The Qi standard came out of water filtration units, which needed wireless power, and has been widely endorsed but devices are still quite rare. Under the Qi specification, “low power” for inductive transfer means a draw of 0 to 5 W, and that’s where mobile device charging solutions most probably go. The system used inductive coupling between two planar coils to transfer power from the power transmitter to the power receiver. The distance between the two coils is typically 5 mm, but can be expanded to 40mm.

The Qi system uses a digital control loop where the power receiver communicates with the power transmitter and requests more or less power via backscatter modulation. Besides low-power specification up to 5 watts, there is also a medium-power specification will deliver up to 120 watts. The frequency used for Qi chargers is located between about 110 and 205 kHz for the low power Qi chargers up to 5 watts and 80-300 kHz for the medium power Qi chargers.

Method: inductive coupling between two planar coils
Frequency: 110-205 kHz (80-300 KHz)
Communication: backscatter modulation

WiPower was a technology start-up company that used the principles of inductive coupling to develop a near-field wireless energy transfer system. Qualcomm bought WiPower in 2010 and started quietly negotiating with manufacturers to get the technology embedded in their kit. Qualcomm argues that the additional range of WiPower (which can charge devices up to 45mm away) allows new possibilities. WiPower system is based on modified coreless inductive technology and dynamically adjusts power supplied by the transmitter to power demanded by the receiver without the need for control systems or communication. WiPower chargers are claimed to operate at about 60-75 percent efficiency.

Method: inductive coupling
Communication: no need for specific communication

Samsung and Qualcomm’s Alliance for Wireless Power (A4WP) promises more flexibility in wireless charging. Instead of induction, this standard will use loosely-coupled (LC) wireless power transfer (a series resonance-tuned pair of magnetically-coupled coils) to transmit power. This construction allows that the transmitter and receiver don’t have to be in direct contact, which gives more flexibility to industrial designers. This designs will support simultaneous charging of multiple devices with different power requirements. A4WP specification takes advantage of Bluetooth 4.0. The biggest downside in this design is that currently there are no products with this technology are yet on the market.

Method: series resonance-tuned pair of magnetically-coupled coils (loosely coupled)
Frequency: 6.78 MHz
Communications: Bluetooth 4.0

The Power Matters Alliance (PMA) is working on an open standard for wireless charging. A group of companies back up this initiative (including Google, AT&T, ZTE, Starbucks, ,McDonalds, PowerKiss). PMA uses inductive charging method used in Duracell’s Powermat product. It requires the transmitter and receiver be close together, placing the mobile device on the charging pad.

This is quite new alliance but it seems to get lots of backers: over the last few months, the PMA has seen a tenfold increase in membership. One very big thing is that AT&T is seeking from its handset vendors a commitment to one standard of wireless charging.

The PMA is working to advance the widespread acceptance of the wireless power paradigm in multiple sectors. PMA is intent on leading and organizing the Power 2.0 agenda to commercial realization, while working under the umbrella of the most trusted name in standards: the IEEE. Powermat is capable of delivering 5-to-50 watts of power. Powermat allows a built-in check for alignment via light and voice signals based on RFiD Handshake feature. When you place a Powermat-enabled device on one of its mats, the two exchange a “handshake” using RFID: The mat identifies the device, determines how much power it needs and transfers energy to it. Powermat operates at 277-357 kHz frequency. Once a device is fully charged, Powermat stops the electricity from flowing. But as much momentum as the PMA has achieved, it is far from clear whether it will be that bandwagon.

Power Matters Alliance (PMA)
Method: inductive charging
Frequency: 277-357 kHz
Communication: RFID

As obviously useful as wireless charging is, it suffers from a Tower of Babel problem with incompatible standards and competing interests keeping it from truly going mainstream. There are also attempts to support several standards on one product. Samsung Galaxy SIII wireless power supports both Qualcomm’s WiPower and Wireless Power Consortium Qi. The Samsung Galaxy S4 will support both PMA and Qi standards. NXP has developed a charging station, which allows you to use both the general mobile phone charging standards (as well as one rare third standard).

The technologies I mentioned are not the only ones trying to push to the market in the near future. Apple is trying to patent wireless charging, claiming its magnetic resonance tech is new and that it can do it better than anyone else. Digitoday writes that Finnish research organization VTT is planning to combine wireless power and NFC technologies. The reasearchers believe that in the future NFC devices could be made to work as way to get power into device and send power to other device cheaply. Technology is not ready yet, because today’s NFC antenna circuits are not optimized for power transfer and there is no standard that covers this kind of use yet. NFC operates within the globally available and unlicensed radio frequency ISM band of 13.56 MHz.

Wireless Power: Convenient, But Its Shortcomings Are Somewhat Sour article tells that close-proximity inductive coupling is commonly estimated to deliver 50 to 70% efficiency. That’s considerably worse efficiency that what you get with a well designed wired charger. Intel increases consumer-product power consumption 50% blog post says that a system that is 50% efficient on top of the ac-dc conversion, and pumps RF energy all over the place is far from ideal in world where some other parties try to conserve every single watt. In a world with 15 billion chargers, energy efficiency is a big deal. Based in that is makes me a little bit hard to believe the Power Matter Alliance claims that wireless charging could save a lots of power in the future. How Wireless Charging Will Keep Toxic Waste Out of Landfills article tries to describe how wireless power could be more eco-friendly, but it is hard to believe all those claims without good data. I can believe that wireless chargers can have better energy efficiency than some old chargers supplied with consumer devices, but I given the limitations wireless charging it is very hard to believe that wireless charger could ever be more efficient than well designed wired charger. But wireless charger could be well “good enough” to be acceptable.


  1. Tomi Engdahl says:

    What’s the Difference Between Qi and Other Types of Wireless Power Transfer?

    Interoperability, adoption, use case, readiness, and safety/regulatory are the key differentiating factors among these competing technologies.

    Apple announced that its iPhones, AirPods, and other accessories will all include Qi (pronounced “chee”) wireless charging. The Qi standard is one type of wireless power transfer, and certain to be a popular one due to Apple’s adoption. However, other types of wireless power transfer, such as AirFuel Resonant, proprietary near-field magnetic coupling (NFMC), radio frequency (RF), and ultrasound offer different value propositions.

    The No. 1 value-added differentiator for Qi is interoperability. If you see the Qi logo on a product, it is Qi-certified. Qi-certified devices (e.g., phones) are guaranteed to work with Qi-certified transmitters (e.g., charge pads, enabled autos, embedded furniture). This is important in the world of consumer electronics, where users can expect to have Qi transmitters in common locations throughout their daily life: home, car, office, coffee shops, airports, hotels.

    AirFuel is another standard that offers interoperability using a different type of protocol, frequency, and process than Qi. Theoretically, AirFuel promises the same interoperability benefits as Qi (all AirFuel devices will work with all AirFuel transmitters), but the current reality is that Qi has scale via adoption that AirFuel can’t match.

    Proprietary NFMC is, by definition, “proprietary” or “non-interoperable” with other devices. Proprietary systems don’t make sense for consumer mobile devices, but make a lot of sense for non-consumer devices like medical tools/devices, commercial-grade equipment, industrial electronics, unique form-factor devices, etc.

    RF and ultrasound are each in very early stages of development. Individual companies are launching “standards” (such as Ossia’s “Cota Standard”), but the standards are unlikely to become ubiquitous without much broader support from ecosystem partners and further technology readiness.

    Qi technology is undoubtedly the leader in number of mobile devices deployed worldwide. Apple, Google, HTC, LG, Motorola, Nokia, and Samsung have launched Qi mobile phones (note: Google added Qi for Nexus 4, but dropped it from future models citing “slow charging times” that must be addressed before they include it again). Likewise, infrastructure adoption is unparalleled with Qi included in over 35 automotive models, IKEA furniture, Corian countertops, and standalone Qi transmitters of different shapes, colors, and sizes (to name only a few…).

    AirFuel adoption is limited mostly to pilot scale.

    Proprietary NFMC has surprising levels of deployment, partially owed to the fact that certain niches have been using wireless power since the 90s. For example, implanted neurostimulators, electronic toothbrushes, and industrial equipment interconnects have been leveraging magnetic-coupling technology for over two decades.

    RF has no major commercial deployment, but has been impressively displayed by a variety of technology developers, including phone-charging demos where multiple phones are charged simultaneously at distances up to 15 feet away from the source.

    AirFuel Resonant’s major promise is use case. AirFuel utilizes loosely coupled technology, which means that multiple devices can charge from a single transmit coil simultaneously; orientation and distance (up to ~50 mm) is flexible; power levels can scale reasonably above 50 W; and device charging can be invisible and more intuitive (i.e., embedding transmitters under the counter versus visibly embedding in or on the counter).

    For AirFuel to succeed, it needs adoption and scale. Superior technology and use case may win over customers in the long term, but there’s a significant uphill climb given Qi’s current market leadership.

  2. Tomi Engdahl says:

    Magnetic Connective Wireless Charging and Data Transfer

    Magnetic connective wireless charging (Magconn) is an innovative magnetic connection technology that is a simple and safe low-cost alternative to induction charging and conductive wireless charging, with all the benefits of a direct plug-in connection, even for data transmission, data acquisition and sending pulse signals or audio. The product is most versatile and its potential applications are multiple. Magconn is proving to be of major interest to product designers working on devices destined for the Internet of Things, including rugged, smart, wearable, and wireless devices.

    Magnetic connective wireless charging is the name given to the worldwide patented Magconn product technology. Although it may seem somewhat contradictory, the name Magconn is a most apt one, when one thinks about the term “wireless” in a different context. “Inductive and conductive wireless charging” have used the term “wireless”: in theory, it is correct usage of the word as the power is actually transmitted wirelessly, albeit at an extremely short range. However, the wireless device still has to be physically rested on or in a charging platform, hence eliminating the process of plugging in the device when it needs to be charged.

    Magconn is a lower cost alternative that offers so much more! There is no charging efficiency loss, no energy loss and not heat loss, as effectively it is direct contact. Direct contact means no loss in charging times. Magconn uses magnets to automatically self position and self center the device to the charger.

  3. Tomi Engdahl says:

    EV Charging Moves Forward with Collaborations

    More firms are partnering to innovate at the pace of the fast-evolving automotive market, as shown by WiTricity’s use of TI semiconductor components in its new automotive wireless charger solution.

    As a result of the rapid growth rate in the electric vehicle (EV) market, wireless charging solutions are quickly emerging. Many semiconductor companies, technology developers, and carmakers are working on new wireless charging automotive solutions. Sometimes they join forces to do so, as is the case for WiTricity and Texas Instruments.

    WiTricity’s DRIVE 11 wireless charging technology can optimize energy transfer between the source and vehicle in a wide range of real-world operating conditions including parking misalignment, differing vehicle ground clearance, and varying battery voltage conditions. The DRIVE 11 features Texas Instruments’ C2000 real-time control microcontroller.

    “New automotive technologies, such as wireless charging, are entering the market at a rapid pace,”

    WiTricity is working with major automakers and Tier 1 suppliers to make wireless EV charging a commercial reality. The DRIVE 11 evaluation system is an end-to-end reference design for “ON and OFF” wireless charging for pure electric and hybrid vehicles. With up to 11kW of power and up to 94% efficiency, the system is suited for applications based on the SAE TIR J2954 standard, which is an industry guideline that establishes wireless power transfer between infrastructure, vehicle suppliers, and OEMs for plug-in electric and electric vehicles (PH/EVs). Licensing agreements have been announced with Toyota, Delphi, TDK, IHI, Shindengen, Daihen, and BRUSA.

  4. Tomi Engdahl says:

    Andrew Tarantola / Engadget:
    San Jose-based Energous, which is developing wireless charging tech that works from three feet away, says the FCC has approved its product, set for debut at CES — Charging your mobile device wirelessly is certainly less of a hassle than plugging it in, but still requires the device …

    FCC approves first wireless ‘power-at-a-distance’ charging system
    The WattUp Mid Field transmitter refills batteries from 3 feet away.

    Charging your mobile device wirelessly is certainly less of a hassle than plugging it in, but still requires the device be in physical contact with its station to actually work. That’s about to change now that the Federal Communications Commission has approved the first wireless charger that works from up to three feet away.

    The transmitter converts electricity into radio frequencies, then beams the energy to nearby devices outfitted with a corresponding receiver. This differs from the resonant induction method that the Pi wireless charging system relies upon and offers a greater range than the Belkin and Mophie chargers that require physical contact with the device.

    The WattUp can charge multiple devices simultaneously and should work on any number of devices

    the company does plan to show off the new technology at CES 2018

  5. Tomi Engdahl says:

    In the car, you can charge your cellphone wirelessly

    Now that Apple’s iPhone also supports wireless downloading, technology begins to attract more car makers. At Las Vegas CES, On Semiconductor develops a solution for mobile phone charging safely in a car.

    Together with ConveniantPower Systems, ON Semi has developed a solution around its VCV6500 power management circuitry. The solution uses different coils to support multiple devices and deliver up to 15 watts of charging power.

    Companies make the most of the new detection technology for foreign objects so that the charging field can be implemented relatively large without the connection to the wrong devices.

    According to Sem, in addition to safety, it is important to carry out a wireless download where the device is simply “dropped” on the platform for charging. The VCV6500 power management circuit operates on a 5 volt input voltage and can be used to produce both wireless Qi and PMA standards.

    Source: http://www.etn.fi/index.php/13-news/7370-autossa-voi-pian-ladata-kannykan-langattomasti

  6. Tomi Engdahl says:

    Wireless charging: advanced technology delivers real benefits

    Power needs to catch up with data and become wireless to truly empower the latest generation of mobile devices. In this technical article, Infineon reviews the design challenges and standards that drive this new sector before looking at technologies that make this vital step possible.

    As with many emerging technologies, multiple incompatible standards develop which stifle progress until a universal solution emerges. Wireless charging has two industry alliances and two standards. The Wireless Power Consortium (WPC) supports the Qi inductive standard that supports tightly coupled charging. Qi has become the mainstream standard, covering over 80% of all wireless charging receivers. The Power Matters Alliance (PMA) and the Alliance for Wireless Power (A4WP) were formed as separate organizations. PMA focused on tightly coupled inductive solutions whereas A4WP worked on loosely coupled resonant technology. PMA and A4WP merged and rebranded as the AirFuel Alliance (AFA).

    Currently, there are three topologies for wireless charging, offering different advantages. Single-coil inductive is the simplest and most prevalent solution. Supported by Qi and AirFuel, this employs a single transmitter coil and requires exact and close positioning of the device and the transmitter, which precludes charging through surfaces. This approach can only charge a single device.

    Multi-coil enables intelligent systems that detect the coil closest to the device and direct the power accordingly. The broader charging field allows you more freedom in placing the device to be charged.

    AFA supports a resonant approach that relies on resonance between the transmitter and receiver to transfer energy far more efficiently. This approach charges multiple devices from a single coil and allows for a greater distance (up to 50mm) between the transmitter and receiver. This flexibility in positioning of the device gives a ‘drop and go’ experience with efficiencies up to 80%.

    The resonant approach permits higher power ratings, allowing laptops or power tools to be charged wirelessly.

    There are two primary topologies used for resonant (AirFuel) applications, Class D and Class E. Class D offers an almost flat efficiency curve over a wide load range and is therefore suited to general-purpose wireless charging stations, such as those found in public places where a wide variety of devices could be charged. Class D is suitable for a wide range of power levels.

  7. Tomi Engdahl says:

    USB Type-C Power Delivery and Wireless Charging Now Available in One IC

    They’ve arrived. ROHM’s dual-mode devices enable simultaneous charging, automatically switching charging operation without the need for an MCU.

    While wireless charging continues to gain traction, a growing number of portable devices also are adopting the USB Type-C Power Delivery (USBPD) standard, which allows for charging up to 100 W (20 V/5 A). To deliver the wide power-supply range required by USBPD, a boost function must be added to a system to charge two-cell (approx. 8.4 V) batteries from conventional 5-V chargers. And if you want to enable the two different charging methods at the same time, it requires mounting charge ICs along with peripheral components as well as an MCU to control charge switching—all of which presents a barrier to introduction.

    However, ROHM shows it can be done in a simpler manner. The company developed dual-input charging ICs supporting both USBPD and 5-V inputs in a single package that’s compatible with wireless as well as USBPD charging technologies. Support also is provided for USB Battery Charging Specification Revision 1.2 (USB BC 1.2), the key standard for establishing the proper way to charge a battery from a USB port (up to 7.5 W [5 V/1.5 A]). This facilitates configuration of dual-mode systems capable of simultaneous charging via USBPD or from an ac adapter.

    The BD99954GW/MUV (Fig. 1) generates a charging voltage from 2.56 to 19.2 V for one to four cells (in series) through boost-buck control.

  8. Tomi Engdahl says:

    At CES 2018 Powercast, Energous to Demo Wireless Charging at a Distance

    On Dec. 26th Powercast Corporation said that it will unveil at CES (booth #40268) an FCC- (Part 15) and ISED-approved (Innovation, Science, and Economic Development, Canada) three-watt PowerSpot transmitter which can deliver over-the-air charging to multiple electronic devices from a few inches to 80 ft. away, and that charging mats or direct line of sight are not needed.

    Up until this point wireless charging has been very short range, based on either Qi or Powermat standards

    The Powercast PowerSpot transmitter, on the other hand, sends RF energy on the 915-MHz ISM band over the air to a receiver chip embedded in a device, which converts it to DC to recharge its batteries or directly power the device. This remote charging technology behaves like Wi-Fi, where enabled devices automatically charge when within range of a power transmitter.

    Charging rates will vary with distance, type, and power consumption of a device.

    he PowerSpot transmitter uses Direct Sequence Spread Spectrum (DSSS) modulation for power and Amplitude Shift Keying (ASK) modulation for data, and includes an integrated 6-dBi directional antenna with a 70-deg. beam pattern.

    The company expects that up to 30 devices left in the zone on a countertop or desktop overnight can charge by morning, sharing the transmitter’s three-watt (EIRP) power output

    Powercast’s Lifetime Power Energy Harvesting Development Kit for Battery Recharging is a demonstration and development platform for recharging batteries wirelessly from RF energy. It is designed to be used with an app and is configured for out-of-the-box operation. The battery recharging boards utilize the P1110B Powerharvester Receiver, which converts RF energy into DC power. Either the PowerSpot transmitter or TX91501-3W transmitter is the source of RF energy, with both operating at 915 MHz. Other RF energy sources operating from 850-950 MHz can also be used as power sources (UHF RFID readers, for example).

    Powercast will begin production of its standalone PowerSpot charger now that it is FCC-approved, and is also offering a PowerSpot subassembly to consumer goods manufacturers who want to integrate it into their own products (think lamps, appliances, set-top boxes, gaming systems, computer monitors, furniture or vehicle dashboards).

  9. Tomi Engdahl says:

    At CES 2018 Powercast, Energous to Demo Wireless Charging at a Distance

    on December 26th, Energous Corp., the developer of WattUp charging technology, announced that it had received “Industry-First FCC Certification for Over-The-Air, Power-At-A-Distance Wireless Charging.” The FCC determined that the WattUp RF beam forming based wire-free at-a-distance charging is safe and meets the current regulatory health and safety guidelines established by the FDA (and enforced by the FCC).

    The WattUp Mid Field transmitter sends focused, RF-based power to devices at a distance.

    The company claims it is the first FCC certification for power-at-a-distance wireless charging under Part 18 of the FCC’s rules; Part 18 rules permit higher-power operations than are permitted under the Part 15 rules that were used to approve Powercast’s at a distance charging devices.

    WattUp Mid Field and Far Field Transmitters sense and communicate to authorized receiver devices via Bluetooth Low Energy (BLE), only sending power when needed and requested by those devices. WattUp is software-controlled, determining which devices receive power, when, and in what priority.

    WattUp uses the 5.850 GHz-5.875 GHz band for the transmission of power. This is just outside of the 5.8 GHz Wi-Fi band. Other technical specifications of the WattUp charging solution include:

    A GaN-based 5-10 W RF receiver IC
    A GaN-based 10-15 W RF power amplifier (PA)
    An RF-based charging solution allowing for full 2D / planar movement
    Support for 90-deg. charging angles (sideways charging)
    Accommodation of metal and other foreign objects
    PA integration into the overall system leading to a lowered BOM cost

  10. Tomi Engdahl says:

    Wireless charging. It doesn’t really do what it says on the tin

    As far as consumers and their smart phone go, wireless charging sounds a great idea. And if it was a reality it would be. Let’s face it, relative to much of our technology-driven lives, wireless is the way to go.

    As well as that, wireless charging capability can add costs to the design of a phone which have to be passed onto the consumer, and that is not a good thing in such a cost competitive market.

    Convenience wise I really don’t see the point. You have to plug your charging pad into an electrical socket and then place you phone precisely on the charging pad. So in effect you have replaced one charging wire with another.

    Ok so wireless charging you phone in your car is a good thing.

    Wireless charging happens in two ways; conductive which links conductive material in a charging pad to integral conductive material in the phone, and inductive which uses a charging station which has an induction coil in it.

    Inductive charging is a complex business and not necessarily very efficient or fast. It employs two electromagnetic coils to create a magnetic field between two devices

    Back in the 1860s radio waves were first considered for power transportation by James Maxwell and twenty years after that Heinrich Hertz showed evidence of radio waves using his sparkgap radio transmitter. At the same time engineer and physicist Nicola Tesla was convinced wireless power transfer was feasible. He built a giant coil connected to a high tower with a metre diameter ball on it and then proceeded to push close to 300kw of power into the thing. Unfortunately the experiment failed due to the power scattering in multi-directions.

    Coming back to the modern day and the inaccurately titled, wireless charging concept, there are plenty of electronics developments that are moving the idea forward.

    AURIX and XMC microcontroller families provide design-flexible chipsets for wireless charging apps and reference designs for both inductive and resonant wireless charging solutions for in-car, at home or in public places.

    The controller supports today’s 15W charging standards

    The XMC based 2.5W low-power solution supports both one-to-one and multi-device charging on a single transmitter by using small high-frequency coils which can be implemented in a variety of form factors.

  11. Tomi Engdahl says:

    Wireless Charging of Electric Vehicles

    The successful convergence of new technologies will require electric vehicles (EVs) that are low cost and fully autonomous. These attributes can be realized through wireless charging.

    While the concept of medium-range wireless power transfer (WPT), achieved using near-field (non-radiative) electromagnetic coupling, has existed since the pioneering work of Nikola Tesla (1891) more than a century ago, the technology to enable effective dynamic WPT for EVs is still in its nascent stage. Numerous challenges related to performance, cost, and safety need to be overcome before the vision of wirelessly powered EVs can be realized.


    Near-field WPT systems are of two types: inductive, which use magnetic field coupling between conducting coils, and capacitive, which use electric field coupling between conducting plates to transfer energy (Fig. 1). For medium-range applications (in which the distance between the transmitter and the receiver couplers is comparable to the size of the couplers, as in EV charging), inductive WPT systems have traditionally been preferred.

    Capacitive WPT Systems

    Capacitive WPT systems have potential advantages over the inductive systems because of the relatively directed nature of electric fields, which reduces the need for electromagnetic field shielding. Also, because capacitive WPT systems do not use ferrites, they can be operated at higher frequencies, allowing them to be smaller and less expensive. Capacitive WPT could thus make dynamic EV charging a reality.

    But because of the very small capacitance between the road and vehicle plates, effective power transfer can occur only at very high frequencies, making the design of these systems extremely challenging.


    The size of the couplers in WPT systems can be reduced and the power transfer density increased by designing the systems to operate at higher frequencies.

  12. Tomi Engdahl says:

    Your Next Smartphone May Ditch the Charging Cable in Favor of Lasers

    Lasers have now existed for well over half a century, and yet they still enjoy an almost mystical status in pop culture.

    At the University of Washington, a team of engineers have created a system for charging consumer electronics with laser beams. Wireless charging by laser isn’t a particularly new concept, and the basic technology already exists. It just takes an invisible laser beam emitter, and a power cell which converts that into electrical energy.

    The real innovation here is in the practicality and safety of the system.

    the team added an additional four “guard” lasers that are completely harmless and which surround the power laser. If something touches one of the guard lasers—like your hand—a shutter will block the power laser in just a fraction of a second.

    The system can transmit power up to 14 feet and cover a 15 square inch area. It can provide 2W of power

    Using a laser to wirelessly charge a smartphone safely across a room

    “In addition to the safety mechanism that quickly terminates the charging beam, our platform includes a heatsink to dissipate excess heat generated by the charging beam,” said Majumdar. “These features give our wireless charging system the robust safety standards needed to apply it to a variety of commercial and home settings.”

  13. Tomi Engdahl says:

    Next year, a billion wirelessly charged devices

    According to IHS, last year, 500 million wireless charged devices were sold. The amount is 40 percent higher than in the previous year. Mobile phones were the largest single product group, whose growth began to be the launch of the Samsung Galaxy S8 in April 2017.

    Of course, wirelessly, you can charge a lot of devices other than just smartphones. About Puffy Devices Apple’s Watch smartphone is the best-selling, portable wireless rechargeable device from IHS. For home appliances, the toothbrush is clearly the most popular and will be sold more than 100 million by 2026, IHS estimates.

    According to IHS, the widespread introduction of wireless charging slowed down the fight for several competing standards. By the beginning of 2017, the Qi standard gained the market and its position is now believed to be further strengthened.
    Ensi vuonna miljardi langattomasti ladattavaa

  14. Tomi Engdahl says:

    Wireless Charging Creeps Forward

    Electric cars, mobile devices and industrial applications are focusing renewed attention on this technology.

    “I remember working 10 or 15 years ago on medical implants that had to be recharged using a cuff or coil so the power could get through and you wouldn’t have to go back to surgery,” Jeff Miller, a product marketing manager at Mentor, a Siemens Business. “Or charging the tire pressure monitoring system on a truck – you can’t get wires through a tire, and you didn’t want to take the tire off, so it’s worth looking into a different approach.”

    Most applications for wireless power involve industrial, automotive, or low-end consumer products such as rechargeable toothbrushes. But increasingly it is finding a home in smartphone chargers. These are mainly based on the Qi standard for wireless charging, which relies on magnetic induction generated by a transmitter and receiver that must sit so close to each other during charging that they nearly touch.

    It is very difficult to get most wireless power products to generate and actually deliver 5 watts or more that a smartphone needs to charge, Treffers said.

    “It is easy to do a demo that looks as if you are charging a phone from 15 feet, but it is important to look at the numbers,” he said. “If you are only delivering microwatts to a device that wants 5 watts, that is not very useful. With magnetic induction you can get 5 watts, 2.4 kilowatts for appliances, power for laptops and drones at 60 to 100 watts. Power at a distance feeds the dream that you never have to charge, but we are nowhere near solving the problem at higher power levels.”

    Wireless convenience
    The desire to charge a smartphone without the inconvenience of a plug helped drive up the market for wireless-power-equipped consumer goods by 40% during 2017 to an estimated 500 million units, according to a February report from IHSMarkit. By 2022, the firm expects sales of wireless power-equipped smartphones to reach 90 million units.

    Apple’s decision last year to support the Qi standard tipped the balance of power, however, and the battle ended in a deal to integrate the two standards, which was announced Jan. 8.

    Power at a Distance
    The other big news came the FCC, which approved two products to charge at a distance — 3 feet in one case, and up to 80 feet in the other. There are currently no commercial products designed or approved to charge cell-phone batteries from a distance of more than a couple of inches.

    In December, the FCC approved an RF-based, one-to-many charging unit called the WattUp mid-Field Transmitter, to charge devices up to three feet away using 900MhZ and 5.8 Ghz.
    It also approved the 3-watt PowerSpot transmitter from Powermat, which operates on RF to charge at distances as far as 80 feet. That one uses 915MHz, which is usually reserved for ISM, and 850 to 950MHz, which is more typical of UHF RFID.

  15. Tomi Engdahl says:

    Near-IR laser system safely charges a smartphone wirelessly from across a room

    This laser-based wireless charging system was created by University of Washington engineers. The charging laser and guard lasers are normally invisible to the human eye, but red beams have been inserted here in place of the guard beams for demonstration purposes.

    Researchers at the University of Washington (Seattle, WA) have designed and experimentally demonstrated a laser-based line-of-sight wireless power delivery system that could be used, for example, for charging smartphones and other devices.1 The researchers say that the system delivers more than 2 W of power safely over distances of 4.3 and 12.2 m for a smartphone (25 cm2) and tabletop form factor (100 cm2) receiver, respectively.

    The system uses a high-power laser-diode source with a 978 nm wavelength, along with two steerable mirrors to aim the beam at the receiver; a photovoltaic cell, heatsink, and retroreflector at the receiver; and a low-power guard laser beam to serve as a safety interlock (using the retroreflector), switching the high-power laser off within 272 µs if the beam is intercepted by a human. The low-power beam is wider than the high-power beam, ensuring switch-off before the high-power beam can contact a person.

    Using a laser to wirelessly charge a smartphone safely across a room

  16. Tomi Engdahl says:

    5 Wireless-Charging Technologies that Bring the Power

    As the technologies presented here and others like it continue to advance and become more prevalent, perhaps Tesla’s dream of a completely wireless world may come to fruition.

    1. WiTricity

    Boston-based startup WiTricity is known for its “magnetic resonance” wireless-charging technology, which is based on weakly coupled electromagnetic resonant objects to transmit power.
    WiTricity’s primary focus is outfitting electric vehicles with the system and has backing from several automakers, including Toyota and Nissan.

    2. Energous WattUp

    Energous’ WattUp wireless-charging system allows users to charge their smartphones, tablets, and other devices located in the same vicinity as the platform. WattUp functions similarly to WiTricity (magnetic resonance) in that it uses a transmitter equipped with numerous small antennas to send RF signals to a receiver to transfer power.

    That being said, WattUp differs from the Boston startup in that the transmitter utilizes Bluetooth to search for devices that are authorized to be charged using Energous’ app.

    3. uBeam

    uBeam is another startup developing wireless-charging technology, but instead of using traditional methods (inductive, capacitive, magnetic, etc.), it relies on pure ultrasound to transmit power. According to the company, the platform works using a transmitter that’s similar to a speaker, emitting high-frequency sound in the 45- to 75-kHz range (inaudible to humans and animals). It then uses a phased-array antenna to direct the sound to a microphone-like receiver;

    4. Qi Wireless Power

    The Qi standard has been incorporated into over 140 mobile devices and chargers
    since its release back in 2008. Developed by the Wireless Power Consortium, the Qi standard provides wireless power transfer using inductive charging.

    5. Elix Wireless

    Elix Wireless has been developing high-capacity chargers ranging from 1,000 to 20,000 W for any number of wireless-charging applications, including EVs and industrial equipment. The company specializes in “magneto-dynamic coupling” (MDC), which uses a pair of rotating magnets in both the transmitter and receiver, with the two separated by an air gap. The rotation of the magnet in the transmitting unit causes the magnet in the receiver to rotate in synchronicity, allowing for efficient power transfer that produces less heat than other inductive methods.

  17. Tomi Engdahl says:

    Wireless charging: advanced technology
    delivers consumer convenience
    A n i n t e g r a t e d a p p r o a c h
    d e l i v e r s r e a l t e c h n i c a l b e n e f i t s i n r e s o n a n t
    s o l u t i o n s

  18. Tomi Engdahl says:

    Mystery Brand EV Will Offer WiTricity’s Wireless Charging This Year

    In the coming months, an unnamed manufacturer will bring an electric car to market that offers wireless charging from WiTricity, Alex Gruzen, the company’s chief executive, tells IEEE Spectrum.

    Unnamed, yes, but not utterly un-guessable. Among the companies that have demonstrated wireless charging are BMW and Hyundai. And, though there are other wireless charging companies out there—Qualcomm, for example—Hyundai has explicitly named WiTricity as the supplier of the system it showed on its new Kona EV last week at the Geneva Motor Show. Other companies known to be working with WiTricity include Honda, Nissan, and Toyota.

  19. Tomi Engdahl says:

    How can wireless charging help industry at all levels?

    Wireless charging is becoming increasingly popular as a smartphone feature, but the technology has wider implications that will one day have a massive impact on industry at all levels.

    You spot the battery indicator on your phone is low, so you place the device on a charging pad. No fussing with cables; an easy way to grab your phone and go. It’s the public face of wireless charging. Usually found at home, wireless charging for smartphones is increasingly appearing in the workplace. But is this the limit of the technology? What other applications does wireless charging have, and how can it help industry?

    Of the two main technologies, inductive and resonant, it’s the former that has the most use. With two main standards (Qi, and PMA), inductive wireless charging has some advantages which provide unique industrial applications.

    Protected connections mean that water and oxygen cannot corrode wires and components, and with no need to plug and unplug, devices are less prone to general wear and tear. This in turn makes hardware more convenient. Meanwhile, for medical applications of wirelessly charged equipment, there are implications for infection control; for instance, equipment can be kept far cleaner.

    On the other hand, inductive charging takes longer to recharge a battery, and has a short range. Wireless might be convenient for a quick exit; it’s less convenient if you need to pick up and use the device while it’s charging.

  20. Tomi Engdahl says:

    Simple Wireless Electricity System

    A pancake coil and a transistor. 1x AAA battery is being used to power the circuit. The coil is an old modem lead, with 2 wires running through it. The wires are connected following Nikola Tesla’s classic pancake coil method.

    How to make a bifilar Tesla coil. The easy way.

    Nikola Tesla describes his bifilar coil in patent 512340. This video describes how to make one easily, with speaker wire.

  21. Tomi Engdahl says:

    Induction Energy Experiments

    Want to know how an induction cooker works?
    Can it used with a coil to power a lamp?

  22. Tomi Engdahl says:

    EEVblog #1092 – Wi-Charge IR Wireless Charging – Fact or Fiction?

    Running the numbers on the W-Charge Infrared laser wireless charging system, does it work?, is it practical?, what is the efficiency?, how much power can it deliver?, is it dangerous?
    And the laser power is HOW MUCH?!

    CORRECTION: The laser output power was stated incorrectly, it was assuming the input power to the laser when it should have been the optical output power. The correct number for a 45% solar cell and zero other losses is 11.1W laser power, not 18W. Still the same class of laser and just as dangerous.

  23. Tomi Engdahl says:

    Future Electric Cars Could Recharge Wirelessly While You Drive

    Electric vehicles may one day be able to recharge while driving down the highway, drawing wireless power directly from plates installed in the road that would make it possible to drive hundreds—if not thousands—of miles without having to plug in.

    The innovation is to use electric rather than magnetic fields. lthough the capacitance between two plates separated by the air gap between a vehicle and the roadway is very small, real power can be transferred if the frequency is high enough. At megahertz-scale frequencies, the researchers were able to transfer more than a kilowatt.

  24. Tomi Engdahl says:

    Simple Wireless Electricity System

    A pancake coil and a transistor. 1x AAA battery is being used to power the circuit.
    The coil is an old modem lead, with 2 wires running through it. The wires are connected following Nikola Tesla’s classic pancake coil method.

    1000W Induction Heating Part 4: Pancake Coil

  25. Tomi Engdahl says:

    EEVblog #1099 – BattBump Kickstarter REDACTED EDITION!

    The infamous video is back up, with hilarious Streisand effect inducing redactions to prevent illegitimate Youtube Privacy complaints from, I don’t know

    BattBump – A mobile app to share battery charge via NFC!
    Yes, it’s as stupid as it sounds.
    It’s NOT a joke, it’s the dumbest Kickstarter idea ever.

    BattBump update — the project backs down on its claims, then cancels and vanishes

  26. Tomi Engdahl says:

    Solving a wireless charging mystery

    No worries; a few extra bucks (mostly) fixed the situation. My wife normally keeps a thin case on her phones anyway, to protect their backsides; a svelte and inexpensive wireless charging accessory slipped in-between the phone and case added Qi support to the case-clad Pixel XL at the tradeoff of monopolizing the phone’s USB-C (formally known as USB Type-C) port.

    Although the engineer in me knows that wireless charging is less efficient (i.e. slower) than the conventional cable-tethered alternative, I can’t argue with the convenience. And given that full recharges take place overnight while we’re sleeping, the charging rate is (within reason, of course) a don’t-care, anyway.

    when the Mophie is connected to the charger wirelessly, its battery serves two important roles; powering the phone, and powering itself, specifically its own Qi receiver and other recharging hardware. But if the Mophie battery is completely drained, it can’t power itself, therefore can’t wirelessly recharge itself.

    The “fix” for this scenario, of course, is to instead recharge the Mophie via USB-C,

    Situations like this admittedly drive me nuts; I wonder, for example, how many Mophie Juice Packs have been unnecessarily thrown away or returned for refund based on an understandable but incorrect diagnosis of premature demise. Or, at minimum, I wonder how much unnecessary consumer time and angst has been consumed on the phone, in 1-1 chat or in email back-and-forth with Mophie’s customer support … time which is an unnecessary expense to the company, too.

    A bit more effort spent in upfront field testing prior to production would have, I suspect, uncovered the issue, enabling Mophie to at least properly document it, if not add hardware support to the juice pack to preclude full battery drain prior to wireless recharge.

  27. Tomi Engdahl says:

    Power Management Chapter 12: Wireless Power Transfer

    You can employ wireless power transfer at different power levels. At the low power level, wireless power transfer is intended for smartphones and other portable battery-powered systems. Higher-power wireless transfer is used to recharge the battery in an electric vehicle. F

    Is there a wireless power transfer standard for portable phones?

    Wireless power transfer is based on the Wireless Power Consortium’s WPC 1.1 Standard (July 2012) that facilitates cross-compatibility of compliant transmitters and receivers. The Standard defines the physical parameters and the communication protocol used in wireless power transfer.

    The Wireless Power Consortium’s global standard for compatible wireless charging is called Qi (pronounced “chee”). The Qi standard guarantees that any device carrying the Qi logo will work with any charging surface that carries the Qi logo, regardless of manufacturer or brand. Qi allows design freedom, product differentiation, and guaranteed wireless charging interoperability.

    Wireless power transfer relies on magnetic induction between planar receiver and transmitter coils. Positioning the receiver coil over the transmitter coil causes magnetic coupling when the transmitter coil is driven.

    How do the receiver and transmitter ICs provide the wireless transfer?

    The power-transfer receiver IC provides efficient ac/dc power conversion as required to comply with WPC 1.1 communication protocol. Control algorithms provide an effective and safe Li-Ion and Li-Pol battery charger—eliminating the need for a separate battery charger circuit.

    What determines the power transfer?

    Power transfer depends on coil coupling, which depends on the distance between coils, alignment, coil dimensions, coil materials, number of turns, magnetic shielding, impedance matching, frequency, and duty cycle. Receiver and transmitter coils must be aligned for best coupling and efficient power transfer. The closer the space between the two coils, the better the coupling. However, to account for housing and interface surfaces, the practical distance is set to be less than 5 mm

    Power transfer is regulated by changing the frequency along the resonance curve from 112 kHz to 205 kHz (that is the higher the frequency is, the lower the power). Duty cycle remains constant at 50% throughout the power band and is reduced only once 205 kHz is reached.

    An A6 coil arrangement can achieve greater than 70-percent efficiency.

    Does the WPC standard set the coil characteristics?

    The WPC standard describes the dimensions, materials of the coils, and information regarding the tuning of the coils to resonance. The value of the inductor and resonant capacitor are critical for proper operation and system efficiency.

    Why is capacitor selection important?

    Capacitor selection is critical to proper system operation. The resonant tank requires a total capacitance value of 68 nF +5.6 nF center coil, which is the WPC system compatibility requirement. Capacitors chosen must be rated for at least 100 V and must be of a high-quality C0G dielectric (sometimes also called NP0). They typically have a 5% tolerance, which is adequate.

    Both parasitic metal detection (PMOD) and foreign object detection (FOD) can continuously monitor the efficiency of the established power transfer. This protects against power lost due to metal objects in the wireless power transfer path.

    Oak Ridge National Laboratory’s Demos 20kW, EV Wireless Power Transfer System

    A 20 kW wireless charging system for electric vehicles was demonstrated recently at the Department of Energy’s Oak Ridge National Laboratory (ORNL). The charging system achieved 90% efficiency at three times the rate of plug-in systems commonly used for electric vehicles.

    The researchers are already looking ahead to their next target of a 50kW wireless charger, which would match the power levels of commercially available plug-in quick chargers.

  28. Tomi Engdahl says:

    EEVblog #1001 – uBeam Ultrasonic Wireless Charging DEBUNKED!

    Dave debunks the uBeam ultrasonic wireless phone charging technology and explains why this will NEVER be a practical solution. Also, Meredith Perry’s rant on engineers and other experts.


  29. Tomi Engdahl says:

    EEVblog #945 – Thermal Powered Smartwatches Are GIMMICKS!

    Thermal powered smartwates are nothing more than gimmicks. Dave runs the numbers on the Matrix Powerwatch from Indieigogo. Also some exercise testing shows up an unusual and undesired effect when using thermoelectric generators on your wrist.

  30. Tomi Engdahl says:

    A Guide to Wireless Connectors

    Wireless-power-transfer (WPT) technology using near-field magnetic coupling (NFMC) has been gaining a lot of attention, primarily in the area of wireless charging for applications like smartphone applications. However, there exists another class of products commonly referred to as “wireless connectors” (WiCo), or “wireless couplers,” that utilize the same physical principles.

    Wireless connectors are important for applications where conventional mechanical connectors may not be reliable, or in some cases not even possible to use. Examples of the issues that connectors may face include intrusion from liquid, dirt, and/or corrosive environments. In addition, physical electrical connections become challenging when a situation demands freedom of movement between two or more systems.

    WPT as Applied to Connectors

    Most devices in the market that currently use wireless power for battery-charging applications follow an established standard (such as Qi1 or AirFuel2) to satisfy interoperability and performance requirements. However, these standards are primarily for consumer electronics applications.

    While repurposing of the hardware could allow for some wireless-connector applications, limitations will be imposed, for example, on coupling, data rates, BOM, range, etc. Furthermore, for WiCo, interoperability may not necessarily be needed since the system is typically “closed,” meaning there will always be a known transmitter and corresponding receiver (“a mated pair”). This gives the designer options for customization and cost optimization.

    That being said, it’s conceivable that some classes of wireless connectors may evolve as standards, similar to USB for wired connectors. For this to happen, the solution(s) will need to address a common problem across an industry or industries.

    NFMC and Communication

    For NFMC applications, antenna (coil) size is wide-ranging, typically greater than about 25 mm in diameter. Preferred frequencies range from 10 kHz to about 13.56 MHz.

    Both magnetic induction (MI) and magnetic resonance (MR) use the same physical principle, i.e., a time-varying current in the transmitter antenna is used to create a time-varying magnetic field that induces a voltage in a receiver antenna. The “generally accepted” distinction between MI and MR lies in the use of reactive components to reduce the reactive impedance looking into the antenna—MI doesn’t use it; MR uses it. In reality, all systems known to the authors use capacitive components to alter the effective impedance looking into the antennas, both on the receiver side and the transmitter side.

  31. Tomi Engdahl says:

    5 Things You Need to Know about Wireless Charging and How It Impacts Design

    Engineers developing consumer electronics, wearables, handheld computers, and other devices are actively considering how to include wireless charging into these devices.

    Thanks to flagship smartphones from Apple and Samsung—and the addition of charging stations in places like coffeehouses, airports, and hotels—wireless charging has been gaining momentum with consumers.

    Smartphones ushered in the era of wireless charging. But as more product designers are exposed to the technology, they are discovering use cases for new categories of products. Products including smartwatches, fitness trackers, hearing aids, earphones, sporting goods, apparel, handheld computers, and medical devices now have wireless charging in their specs.

    Here are five things to be aware of when putting wireless charging into your product:

    1.) Wireless Charging Is Difficult.
    2.) Standards Can Be Helpful, but They Aren’t Critical.
    3.) Chips, Magnetics, and Integration Are Critical.
    4.) It’s Way Better to Start at the Beginning.
    5.) Know the Risks Based on Where You Are in the Design Cycle.

  32. Tomi Engdahl says:

    You Can Add Wireless Charging to iPhone… Kinda

    Take a look at his latest video which attempts to add wireless charging to an iPhone. I think there’s a lot to be said for superb lighting and a formidable camera, but part of this is framing the shots just right.

    Now of course we’ve taken apart our fair share of phones and there’s always that queasy “I think I’m going to break something” feeling while doing it.

    How We Added Wireless Charging to an iPhone – in China

  33. Tomi Engdahl says:

    5 Things You Need to Know about Wireless Charging and How It Impacts Design

    Engineers developing consumer electronics, wearables, handheld computers, and other devices are actively considering how to include wireless charging into these devices.

  34. Tomi Engdahl says:

    Wireless Power: One Futuristic Technology Energizing Smart Cities

    A mobile device battery has many demands to fill: photos, maps, social media, apps and ride hailing services, etc. These demands increase at conferences and during travel. Almost inevitably, device batteries drain. One must sit near the wall, pole or wherever, to juice up. That could take an hour… or two. It is, as millennials would say, a huge bummer. However, one exciting technology could eradicate that dead battery stress. It’s called wireless power, and it will energize smart cities.
    What is Wireless Power?

    In this case, wireless power is energy transfer over the air (OTA) using radio frequency (RF) signals. These RF signals carry energy, much like transmitting Wi-Fi signals that hold data. However, when a signal does not carry data, it can transfer energy.

    Wireless power transfer is different from mainstream wireless charging, more appropriately called inductive charging. These wireless charging stations rely on electromagnetic induction coils. These coils transmit power to other coils in the device being charged. They require alignment and close contact between station and device. This system requires thermal engineering solutions to manage heat buildup.

    True wireless power is over a distance using a transmitter-receiver system on a specific radio frequency. The transmitter sends the energy. Then, the receiver converts the RF signal to DC power. The beams do not pass through obstacles. They bounce off and around, making them safe for populated areas. This method is as efficient as wired or induction power charging.

    Who makes Wireless Power?

    Currently, there are two major players with market-ready wireless power products. One of them is Energous. It focuses on consumer electronics networks, like smart living rooms. The other is Ossia. This application best suits commercial electronics networks, like coffee shops and airports.

    Both companies have emerged in the last year. Each of them relies on a different RF channel. Energous uses the 900MHz frequency on their WattUp transmitters. Ossia uses the 2.4GHz spectrum for its “Cota” standard.
    How does Wireless Power Work?

    Energous has different requirements for transmission, dependent on distance. It functions up to 15 feet away. For objects “mid-field” to “far-field,” Energous uses beamforming. This process sends energy beams directly to a receiver from the WattUp transmitter. It is a software-managed system. It checks for Bluetooth devices to charge, their distance and their network authorization. In other words, the transmitter will not waste its energy trying to charge every electronic device in the room.

    Smart Cities and Wireless Power

    The most appealing use of wireless power is in smart cities, especially those connected to the Internet of Things (IoT) using 5G technology. These entities rely on a vast system of software, sensors, AI-enhanced robots and IoT devices to automate city tasks. The above systems require varying amounts of power. Devices like IoT require more power and continuously. OTA wireless power would ensure that none of these devices ever turn off.

  35. Tomi Engdahl says:

    Oak Ridge Inches Closer to 15-⁠Minute Wireless EV Charging

    Scientists at Oak Ridge National Laboratory in Tennessee have developed wireless charging technology that they say could fill up a typical electric car today in under an hour. This represents a six-fold improvement over a similar wireless charging system they announced in 2016. That plugless EV charging technology, they report, is now being modified for commercial applications including delivery trucks.

    The idea is to increase the power throughput of their present system by another factor of three—bringing the total charge time for an empty electric vehicle (EV) battery to under 15 minutes. All without needing to plug anything in to the car or really do anything other than drive the EV over a wireless charging plate embedded in the concrete.

    Ozpineci says two key elements of their 97 percent efficiency, 120-kilowatt wireless charging technology concern the material they made it from and the coil that transmits and receives the electric power.

    To beam wireless power from a floor unit to a power receiver unit in an EV, separated by some six inches of open air, means rapidly oscillating the electric and magnetic fields in the coil, inducing similar behavior in the receiving coil in the EV. Practically speaking, Ozpineci says, that means pumping out 120 kilowatts through oscillating currents at some 22,000 cycles per second (i.e., 22 kilohertz).

    “At 10 kW, you can switch at 20 kHz. But when you go up to 100 kW and beyond, you have to reduce your switching frequency—because of thermal issues, because of the device response, because of a number of things.”

    their 100-pound (45-kilogram) coil needs some refining and optimizing

    Energy Department’s 350- to 400-kW target.

  36. Tomi Engdahl says:

    A MEMS switch for wireless power transfer

    If resonant wireless power transfer (WPT) systems are to fulfill their promise for charging electric vehicles and other high-power applications, there is an engineering issue that must first be satisfactorily addressed.

    One of the biggest challenges in optimizing the performance of a resonant WPT system is ensuring that a relatively constant load impedance is presented to the transmitter power electronics at all times.

    Techniques have been developed to address the problem, including large DC/bias power requirements, complex bias circuitry, and large footprint. A new approach uses micro electro-mechanical system (MEMS) contact switches in an impedance matching network that has advantages over these approaches without their limitations.

    There are two common implementations of resonant WPT, resonant inductive coupling and resonant capacitive coupling.

  37. Tomi Engdahl says:

    New System Delivers Power Wirelessly to Multiple Devices

    So far, though, wireless power transfer (WPT) systems have mostly been limited to supplying power to a single load, such as an individual phone. The few systems that support multiple loads do not currently allow for independent control over each one, making it a challenge to simultaneously charge devices that require different amounts of power.

    This may change in the near future, thanks to a new design developed by Chris Mi at San Diego State University and his colleagues that allows for independent control over 10 loads. Their work is described in a recent study in IEEE Transactions on Power Electronics.

    Supplying different amounts of power to individual devices could be useful in a number of scenarios, such as for charging stations that serve various types of vehicles (including electric cars, bicycles, and scooters).

  38. Tomi Engdahl says:

    No Need to Wait for the “Best” Wireless-Charging Solution—Qi Is It

    Sponsored by IDT: While advances such as fast USB charging are now entering the wireless-power-transfer fray, Qi is the go-to solution for most of the industry.

    It took so long for wireless charging to gain momentum because three approaches were battling it out for supremacy: Qi from the Wireless Power Consortium (WPC), Powermat Airfuel from the Power Matters Alliance (PMA), and Rezence from the Alliance for Wireless Power (A4WP). Fortunately, the winnowing out is over, at least until longer-distance wireless charging is commercialized. The winner is Qi, but the others only called it quits just over a year ago when Apple finally chose its smartphones and Apple Watch. To their credit, the rivals circled their wagons twice before throwing in the towel.

    when Apple made its belated decision, the PMA merged early in 2018 with the WPC and is now collaborating with the organization to bring some of its technology to Qi.

  39. Tomi Engdahl says:


    WHEN IN DOUBT, TRY LASERS. Drones are already doing a lot for us — they’re delivering packages, helping with search and rescue missions, and supporting environmental conservation efforts.

    But we don’t have an effective way to keep the devices powered for long periods of time — many can only remain airborne for 30 minutes or so. That may soon change, however. The U.S. Army thinks it has found a way to keep drones in the air indefinitely. And like all good plans, it involves lasers.

    A LONG-DISTANCE POWER-UP. According to New Scientist, the U.S. Army is developing a system in which a laser shot from the ground can power up a military drone mid-flight.

  40. Tomi Engdahl says:

    Langaton lataus yleistyy – tarjolla kaksi tekniikkaa

    Langattomasta lataamisesta tulee monissa kulutuselektroniikan laitteissa valtavirtatekniikkaa seuraavan 2-3 vuoden aikana. Ranskalainen Yole Developpement -tutkimuslaitos on laatinut ennusteen, jonka mukaan vuoteen 2024 mennessä langaton latauspiiri löytyy jo yli miljardista laitteesta.

    Valtaosa latauspiireistä – kaikkiaan 1,2 miljardia – asennetaan älypuhelimiin. Yolen mukaan tekniikka tekee tuloaan myös sähköautoihin, mutta markkinoille ajoneuvojen langattomat latausratkaisut eivät ehdi ennen vuotta 2022.

    Tekniikan käyttöönottoa hidastutti alkuvuosina kahden-kolmen kilpailevan standardin kisa.

    Kapasitanssiin perustuva tekniikka tuli tiensä päähän viimeistään vuonna 2015 ja jäljelle jäi induktanssin perustuva. Siitä löytyy kaksi varianttia, jotka kisaavat nyt markkinoista.

    Tällä hetkellä markkinoita hallitsee Qi-standardi.

    Sen rinnalla on yleistymässä magneettiseen resonanssiin perustuva tekniikka, jossa laitteiden sijoittelu on vapaampaa.

    Yolen mukaan esimerkiksi Apple tuo langattoman latauksen lippulaivatuotteisiinsa resonanssiin perustuvan Qi-tekniikan voimalla.

    langattomaan lataukseen on tarjolla muitakin tekniikoita

  41. Tomi Engdahl says:

    Wireless Charger Gives a Glimpse into Industrial Design Process

    Almost every product on the market has been through the hands of an industrial designer at some point in its development. From the phone in your pocket to the car in your driveway or the vacuum in your closet, the way things look and work is the result of a careful design process. Taking a look inside that process, like with this wireless phone charger concept, is fascinating and can yield really valuable design insights.

    Industrial Design Process: Foam Modeling a wireless charger Consumer product design and development

  42. Tomi Engdahl says:

    How fast will wireless (inductive) charging for electric vehicles be by 2020 compared to cable (conductive) charging?

    Inductive charging can not be very rapid as efficiency is way less than 95%. This means if we charge at near Tesla Supercharger speed (100kW) then there is at least 5kW of heat. If I’m correct ideally we have 80% efficient conductive charging system available. That means at 100kW input output is 80kW. So 20kW of heat. That is about as much heat as domestic fireplace does produce.

    I expect anything more than 1kW of heat is too much (it can not be passively cooled).

    Can inductive charging get better? Yes and no. There is mathematical limit. The only way to get it better is to put coils very close together (almost touching each other). That makes that system pointless.

    Automatic plugs-sockets are the future. They may even be “invisible” (under the vehicle).

  43. Tomi Engdahl says:

    Wireless Charging Without so Many Chargers

    [Nikola Tesla] believed he could wirelessly supply power to the world, but his calculations were off. We can, in fact, supply power wirelessly and we are getting better but far from the dreams of the historical inventor. The mainstream version is the Qi chargers which are what phones use to charge when you lay them on a base. Magnetic coupling is what allows the power to move through the air. The transmitter and receiver are two halves of an air-core transformer, so the distance between the coils exponentially reduces efficiency and don’t even think of putting two phones on a single base. Well, you could but it would not do any good. [Chris Mi] at San Diego State University is working with colleagues to introduce receivers which feature a pass-through architecture so a whole stack of devices can be powered from a single base.

    Efficiency across ten loads is recorded at 83.9% which is phenomenal considering the distance between each load is 6 cm. Traditional air-gap transformers are not designed for 6 cm, much less 60 cm.

  44. Tomi Engdahl says:

    The Samsung Galaxy S10 can wirelessly charge other phones

    The feature relies on the S10’s large battery to charge of other device.

    enable Wireless Power Share, and you can save the day by placing the handsets back to back.

    The new feature should be compatible with all phones that charge via the Qi standard.


Leave a Comment

Your email address will not be published. Required fields are marked *