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Wireless charging shift ahead

Technology News |
By eeNews Europe


By 2018, analysts say, the race will be all but over with one player dominating the 700 million systems using wireless charging. Experts expect a technology shift to resonant charging after a generation of hybrid inductive/resonant products currently coming on the market. Before it’s over, Apple is expected to debut what could be a wild-card proprietary approach.

Wireless charging "standards have to converge, and I think this year they will figure out this market is not taking off until they get together," Henry Samueli, the chairman and CTO of Broadcom, said at a company event in December in San Francisco. "It’s about much more than a smartphone market. The main driver is the Internet of Things."

Ryan Sanderson, a wireless charging analyst at IHS, told us the mobile phone and tablet markets will be key to volume adoption of wireless charging in the coming years. IHS forecasts assume that at least one major cellphone manufacturer will integrate wireless power capability throughout its ecosystem by 2016.

"Apple is probably not eager to adopt another standard for it. They’ll want to develop own thing. They have a huge influence, along with Samsung," IHS analyst Jason dePreaux told us. "It will take those two companies to create a standard, not just saying the standard or joining an alliance, but actually building it in. It’s several years away, though, especially on the Apple side."

Three types of main wireless charging technologies are contenders in the race to mainstream use — magnetic induction, magnetic resonance, and niche solutions such as radio frequency. On the following pages, we will explore each in some detail. Though dePreaux said there isn’t much difference in power or charging time among the technologies, an Ars Technica speed test of the Qi (pronounced chee) technology showed that charging a Google Nexus 7 wirelessly took nearly three times as long as using a power adapter.

Trade groups of chip makers and patent holders back different charging platforms. The Wireless Power Consortium (WPC) backs inductive and bridge solutions, while the Association for Wireless Power (A4WP) champions resonance. Seeing the writing on the wall, the Power Matters Alliance has moved to embrace resonant charging, as well.


The startup Humavox is going it alone with an approach that is based on what it calls radio frequency charging. Still, market watchers say other players and technologies could emerge before the dust clears.

"In the future, it’s possible that technologies which offer the consumer even more freedom of space and distance to charge wirelessly — RF perhaps being an example of this — will enter the market and compete with resonant technologies," Sanderson said. Advancements are likely several years out. "In my opinion, it will be difficult for a new technology to enter the market once an infrastructure is in place, and therefore, if one technology is adopted in volume in the next two years, it is likely to remain the technology of choice for the future."

Last year, 20 million wireless charging receivers were shipped, and though most of them were inductive, Sanderson expects the market to grow to 700 million devices in four years. Inductive and resonant wireless chargers will ship in 2014, with resonant/bridge solutions expected to ramp up in the second half of the year.

A standard is "not taking up faster because folks are confused by the existence of what appears to be competing standards," John Perzow, the WPC’s vice president of market development for Wireless Power Consortium, told us. "The well-known standards — Power Matters Alliance, A4Wp, WPC — those differentiating is making it hard for groups to combine… They don’t share communication protocol. They won’t talk to each other.

But consolidation is necessary before the technology can become ubiquitous. Only inductive and radio frequency products are available to the public, with Qi inductive technology built into products such as the Samsung Galaxy S4, Nokia Lumia 920, and Google Nexus phones and tablets. Major market players such as Broadcom, HTC, and Samsung are among the members of both industry groups.

Magnetic induction currently has the wireless charging market cornered and is available in Google, Samsung, and Nokia devices. Induction typically uses two magnetic coils — a primary wire coil with an alternating electromagnetic field from within a charging base station, and a secondary coil in the device to convert power from the electromagnetic field to electrical current to charge a battery. Together, the coils create a transformer.

"If you design it right — the right frequency and material, the quality of that coil — you can get very efficient power transfer and design for specific distance or power," Perzow said.


Several companies have taken to inductive charging. Samsung’s Galaxy S4 supports Qi, as has Google and Nokia. Perzow said the WPC has more than 40 million wireless devices on the market and has support from the semiconductor industry, Ikea, and Verizon.

The WPC offers close coil inductive technology, which draws up to five Watts and operate at 200-300 kHz. Perzow said the WPC’s Qi technology can extend the charging range up to 40 mm away from the power source with 70% power efficiency.

ConvenientPower’s dual-mode inductive/resonance multi-device charger. Source: WPC blog.

Qi and inductive charging have been touted for having protected connections, being safe enough for medical devices, and harboring low radio frequency interference. However, inductive charging is accused of being more delicate and more inconvenient than other types of charging; users have little freedom and must line up a device precisely with a wireless charging pad.

"I think there’s something to that, but the assumption is that Qi is close couple inductive, and it will be that way forever, and that’s not the case," Perzow said. "It is a constantly evolving technology. Qi is not a product. You can’t spec it."

Though the WPC and Qi are currently synonymous with inductive charging, the WPC also demonstrated resonant technology at the 2014 International CES. Dubbed WoWz, the technology is backward compatible with Qi and charges at a distance of up to 18 mm with 65% charging efficiency.

"Samsung has Qi phones out there today and is also an investor in a company that is developing resonance technology that is in WPC," Perzow said. "It’s reasonable to guess that Samsung will have resonance technology in their phones." A WPC member and phone maker will debut a PMA+Qi compatible wireless charging system in 2014. He expects more bridge products in the coming years. "For a short term, it can work, but as soon as one standard can develop significantly, it’s going to be impossible for that approach to work."


MediaTek, a member of WPC and PMA (now in partnership with the A4WP) debuted its own wireless charging technology at the CES — a dual-mode charging solution that supports Qi and resonance. The system is a stand that can hold and charge the equivalent of two smartphones. It’s built over a single coil and single IC, with a target segment of mobile applications in the range of 1/2 W to 15 W.

On the left (in red) is a wireless charging station based on resonant power transfer technology. On the right is Qi wireless charging station using industive power transfer technology. Source: EE Times/Junko Yoshida.

"The device is smart enough to figure out which charger it is, and then it charges appropriately. [The technology] goes into virtually anything you want from a Bluetooth headset to an electric vehicle," Mark Estabrook, director of strategic marketing at MediaTek, told us. "This is something of a bridge product, we think, meaning we think it will help get the industry from where it is today — the inductive — to the resonant technology which will be developed over the next 2-3 years."

Mark Hunsicker, senior director of product management at Qualcomm and a treasurer for the A4WP, said there is an opportunity for a dual-mode bridge transitional receiver that implements inductive and resonance charging. There’s not much legacy product in the marketplace.

Nevertheless, "I’m not a big fan," Hunsicker said. "It’s not a highly desirable solution from the consumer side, because there’s not a great deal of commonality between the two technologies. There are increased materials and area costs, because there’s not a lot of synergy between the two technologies."

Mohit Bhushan, US marketing manager at MediaTek, told us his company is working on resonance solutions to complement future generations of its recently released LTE SoC.

"The industry tends to use ‘inductive’ and ‘resonant’ as different technologies, though in reality, both are based on inductive technology," Sanderson said via email. "Those which use magnetic resonance are just a highly tuned inductive solution."


Resonant transfer relies on loosely coupled coils that transfer electricity along the same resonant frequency. A capacitance plate, which can hold a charge, attaches to each end of the coil and then produces a resonant frequency from the inductance of the coil and the capacitance of the plates.

A4WP demonstrates resonance charge pad technology. Source: A4WP.

Resonance advocates have championed the technology for the ability to charge multiple devices at once with freedom of placement — the device can be more than 10 inches above or to the side of the charging plate. Distance can also be increased by placing a repeater between the device and charging place. The A4WP says resonance (or, its version, Rezence) can charge devices though surfaces 40-50 mm thick.

"A resonance-based approach gives the opportunity to have multiple devices charging and multiple device types. Competing forums can do some of that, but can’t meet all the requirements," Hunsicker said. "I think you’re seeing the acknowledgement of that, because those other forums have launched resonant working groups. They’ve acknowledged that the resonant-based approach is going to overtake inductive."

The A4WP seems best aligned to lead this charge. Its member companies include Samsung, Texas Instruments, Dell, and WiTricity, whose resonance technology IP have been used in Intel products. The group recently announced a partnership with a former inductive group, the Power Matters Alliance.

"You’ll see resonance charging as accessory products. Some OEMs will build it natively into, phones but it could also be an accessory back cover," Hunsicker said. "The circuitry can be built into the phone."

"We’re not in the coils game. We’re in radio frequency," Humavox CEO Omri Lachman told us. "Its characteristics give you a lot of freedom and releases setbacks like the need to align or couple the receiver and the transmitter. You have freedom to create, get rid of all inhibitions."


The Israeli company utilizes radio frequencies for wireless charging under its Eterna platform, where frequencies are transmitted and converted to DC voltage. The charge is converted by the company’s miniature antenna receiver, which is installed in a charging platform called Nest.

Officials say Humavox’s miniaturized circuitry makes radio frequency wireless charging scalable. Source: Humavox.

With Humavox’s technology, a signal broadcast at 2.4 GHz sends energy to the receiver, which pushes voltage to a management IC. Frequency transmission occurs in the industrial, scientific, and medical band, though Lachman said the company has engineered compliance with a "very, very broad spectrum of frequencies to transmit in, from single MHz to high range of GHz." The receiver operates at as low as 7 milliamps to support low-power devices such as hearing aids.

Humavox has marketed its technology with a primary focus on healthcare and elders — a huge market with no rechargeable capability due to age segment. Lachman said the winning technology in the wireless charging market will be the most intuitive. "The user doesn’t want to learn new tricks when it comes to operating their device, especially when it comes to charging. For us, intuitive is not resonance. It’s not having my device charge from nowhere, because nine out of 10 people don’t want waves or infrared or laser beams in their living room, office, airport."

In addition, he said RF will champion coil-based systems in the wearable Internet of Things realm, because of scalability. RF is more easily integrated into small devices than magnetic or resonance charging. However, there are no mass-market devices that feature radio frequency charging available today.

"Approaches using RF have been aimed at this market before, and first-generation solutions were not widely accepted," Sanderson said. "This doesn’t necessarily mean that we will not see them in the future."

Lachman said that he is skeptical about a single magnetic standard, and that the winning solution will integrate more than one power source. "We heard same promise [of standards] when WPC introduced Qi and Powermat was introduced, and now we’re hearing the same with resonance. Maybe it’s not going to be just radio frequency, but it has to be something — a receiving system that can be easily integrated in sense of form factor."


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