ULP Wireless Update

China smart city embraces resonant wireless charging

Dell’s new 2-in-1 portable computer is the first to incorporate AirFuel-certified wireless charging technology.

Shenzhen in China is the first major city to roll-out resonant wireless charging as part of an overhaul of communication and information technology

Imagine the convenience if all your mobile devices—smartphone, tablet, fitness band—start to charge when brought close to a café table, even if they remain in your backpack. This is the promise of resonant wireless charging, a technology from the AirFuel Alliance that transfers power even when devices aren’t perfectly aligned with, or even particularly close to, the charging transmitter.


The technology is beginning to fulfil this promise as the first commercial devices equipped with AirFuel resonant wireless charging start to reach the market. Public familiarity is also on the rise with a 2016 consumer survey, sponsored by analyst IHS Markit, concluding that eight out of ten consumers in the U.S. had heard of wireless charging, and one in four had used the technology to recharge a smartphone battery. According to the alliance, AirFuel has already enabled more than 4,000 resonant-based public charging spots throughout the world. Now the technology has received another significant boost in a city-wide deployment as part of a “smart city” initiative in Shenzhen, China.


City-wide overhaul

Shenzhen’s initiative includes a public wireless charging infrastructure that adds charging transmitters onto the underside of existing furniture surfaces. Resonant wireless charging is part of a city-wide overhaul that integrates communication, information, and IoT in an ecosystem glued together with ubiquitous wireless connectivity. Offices and hotels are the first to receive charging stations and AirFuel Resonant infrastructure will expand to include more public places such as restaurants, malls, airports, and subway stations for use by the city’s population of 12 million. Shenzhen’s adoption of city-wide wireless charging demonstrates to other cities how ubiquitous wireless charging complements ubiquitous wireless connectivity to improve the productivity, health, and leisure time of citizens.


AirFuel Resonant uses coupled magnetic resonance technology, which has some advantages over the competing inductive technology. These advantages include a single charging transmitter which can simultaneously charge multiple devices across a wide surface area, elimination of the requirement to precisely align the device to be charged with the charging transmitter, and charging that occurs even if an object is placed between the device to be charged and the charging transmitter.


Power transmitting units (PTUs) are equipped with Bluetooth Low Energy (Bluetooth LE) wireless connectivity which connects to a Bluetooth 4.0 (or later) smartphone or tablet (the power receiving unit (PRU)) to control power levels, identify loads, and protect non-compliant devices. Several companies, including LG, Samsung, Motorola, and Nokia, are already selling smartphones and tablets with AirFuel Alliance’s inductive wireless charging technology. Manufacturers look set to incorporate both resonant and inductive technologies into their products for maximum consumer convenience (Samsung, for example, has already implemented more than one wireless charging standard into a single phone.) Moves are afoot to incorporate both technologies into a single certification process.


Dell, for example, introduced the Latitude 7285 2-in-1, featuring AirFuel-certified technology, at CES 2017 in Las Vegas. The portable computer charges automatically when placed on an AirFuel-compatible charging surface. Although slower than plugging in to a power point, the 30 W of power transmitted through resonant wireless charging is sufficient for a handy top-up between full charges.


AirFuel Alliance member companies have already established a far-reaching ecosystem to support wireless charging. Nordic Semiconductor, for example, offers the nRF5 Software Development Kit (SDK) for AirFuel. The SDK can be used with both the nRF51 Series and nRF52 Series SoCs and supports the development of AirFuel Alliance-compliant wireless charging applications. The SDK includes examples for both PTUs and PRUs.