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Wireless charging OTA expected in a decade

Posted: 25 Jan 2016     Print Version  Bookmark and Share

Keywords:Wireless Power Consortium  wireless charging  AirFuel Alliance  WPC  far field 

During the recent DesignCon, a speaker said the future of wireless charging isn't current coil-based systems. In fact, standardisation won't drive this kind of wireless charging adoption among consumers. While the large industry groups such as AirFuel Alliance and the Wireless Power Consortium (WPC) battle for wireless charging dominance in furniture and cars, the answer is in the air.

Existing wireless charging systems that use magnetic induction or resonant technology typically require plugging a mat in to the wall. Those systems also require users to place their device on a specific spot and have sub-optimal charging efficiency, "It's not really revolutionary," said Meng He, Maxim Integrated's power product executive business manager.

Far field communications, which He defines as beaming focused power to coupled devices at specific locations, will ultimately triumph in the wireless charging race.

Far field charging system

Far field charging system diagram. Source: Meng Lee

Infrared systems such as Wi-Charge, RF systems including Energous' WattUp and Cota, and ultrasound from uBeam will ultimately trump wired systems because they allow for freedom of movement and act more like WiFi.

Far field specs

Far field specs. Source: Meng He

He told EE Times that she's betting on RF, but it will take another 10 years before the technology matures. There are many challenges that must be overcome before any of these systems can proliferate, He continued, and none of the following issues can be compromised:


Over-the-air charging systems must be mobile and easily able to follow multiple receivers. When those receivers are out of range, another transmitter must pick up the signal immediately. Still, ultrasound doesn't work through walls and RF loses strength as a receiver moves further from the transmitter.


Many consumers still need to be convinced that charging over the air is safe.

System interference

Low level analogue and digital signals can be effected by EMI/RFI. Both inductive and resonant coil systems are subject to interference, while only ultrasound and infrared over-the-air systems are interference free.


Purchasing a system can be expensive, though He said the iPhone 6 averages 47 cents/year to charge while a home security system costs six cents a day.

Dead battery charge

Near field charging (Qi and AirFuel standards) can revive a dead battery, but far field charging cannot because the receiver must constantly send out a signal to be linked to a power router.

Despite these engineering challenges, He is hopeful about a wire-free future where the ecosystem coalesces to create a great product that needs adopting. The collective work of device manufacturers, semiconductor companies, system manufacturers and infrastructure developers (likely the most important piece of the puzzle, He noted) can great something good, but only after the dust settles between different standards organisation "to provide a seamless charging experience."

One company could completely shake up the charging ecosystem, He said. If Apple created its own wireless charging standard that went beyond "wireless charging" for its Apple Watch, they would have the power "to steer the whole industry into a different direction."

- Jessica Lipsky
  EE Times

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