Wireless Charging Principles & Technology
How Wireless Charging Works
At a basic level, wireless charging works by creating a wireless transfer of energy between two coils, tuned to resonate at the same frequency.
Based on the principles of electromagnetic resonance, resonant-based chargers inject an oscillating current into a coil to create an oscillating electromagnetic field. A second coil with the same resonant frequency receives power from the electromagnetic field and converts it back into an electrical current that can be used to power and charge devices.
Applications and use cases
The benefits of Wireless Power
What’s the difference between Resonant, RF and Inductive technology?
Both Inductive and Resonant technologies use coils of wire to transfer power while RF uses radio frequency. There are also differences in the transmission frequencies and communication protocols, which translate into variations in spatial freedom to support multiple use cases. For example, Resonant coils are tuned for better efficiency and enable spatial freedom while Inductive requires the device to be attached to the charge.
Resonant charging utilizes uniquely designed coils to allow movement over longer distances while charging. With resonant charging, any enabled surface can power a device, up to 50mm height and from a wide surface area.
Resonant-based chargers inject an oscillating current into a highly resonant coil to create an electromagnetic field. A second coil with the same resonant frequency receives power from the electromagnetic field and converts it back into an electrical current that can be used to power and charge devices.
This lets you transfer power over longer distances and does not require exact orientation. Learn more about AirFuel Resonant technology.
RF charging uses a radio frequency transmitter and a receiver embedded within the device (not a coil) to pick up RF energy and convert it to power. RF provides low power at distances ranging from a few centimeters to a meter, delivering true spatial freedom. This means it works well with wearables, medical devices or other devices that need the broadest spatial freedom. Learn more about AirFuel RF technology.
Inductive charging uses closely coupled coils to deliver transfer of a magnetic field over a short distance (up to 20mm). It works well for devices that can be placed directly on top of the charging source (i.e., with no spatial freedom) such as a smartphones on top of a charging pad.
What about Inductive technology – I thought AirFuel supported Inductive?
AirFuel has worked with all three major wireless charging technologies since our creation in 2015 (based on the merger of PMA and A4WP). But, we’ve seen clear market indicators that Resonant & RF deliver the mobile charging experiences consumers prefer most. We’ve also seen that Resonant provides the best solution to enable widespread public infrastructure deployment.
Having widespread infrastructure to support devices is critical to creating major market penetration. AirFuel Resonant has the benefit of being easy to install while Inductive solutions are costly and difficult to install (this is a key reason Inductive has failed to scale). With Resonant, we are already seeing deployments of public and private infrastructure – particularly in Asia – with lots more to come.
We’ve been hearing about wireless charging for several years now – why is it taking so long?
As with any new or disruptive technology, it takes years to develop a vibrant market. Wireless charging is at an exciting inflection point as we move from early stage, proprietary solutions to standards-based solutions. We have more and more standards-based devices and infrastructure coming to market which helps drive the growth of the market.
Is there still an AirFuel standard for Inductive? Will you support companies already using the AirFuel Inductive standards?
Yes – but AirFuel has discontinued specification work on Inductive technology. Our organization’s focus is on next-generation solutions, which include Resonant and RF technologies.
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