11 Myths About Magnetic-Resonance Wireless Charging

Consider the devices we use every day: From smartphones and smartwatches and potentially electric vehicles, electronics are becoming as mobile as people themselves. We rely and expect our devices to be charged at all times, ready-to-use when needed. But as it currently stands, we still must plug in our phones, our electric cars, and our smartwatches, tethering us to cords and cables, triggering range anxiety and obsessing about the remaining juice on our devices.

Wouldn’t it be nice instead to have a user experience where our electronics are charged autonomously and seamlessly, without any conscious human intervention, even while our devices are in use? The physical act of “plugging in” should—and soon will be—an outdated concept due to technology enabling us to deliver energy to our devices sans burdensome cords.

While wireless charging is not a new concept, the industry has been fluctuating over the past decade or so as different forms of the technology enter the arena, all promising to eliminate the last tether. However, those excited for what’s to come are left confused in terms of what is wireless charging reality and what is just a myth.

Before we set out to clarify, let’s look at the history of wireless charging for context. Inductive—the first generation of wireless-charging technology—was very limiting, providing only low power transfer and almost zero spatial freedom. Still, it offered wireless charging’s first form factors, like the electric toothbrush. More recently, power transfer via RF fields have been developed to enable energy transfer over greater distances, but it’s not very efficient at doing so.

Magnetic resonance is another—and the most promising—form of wireless power as it moves beyond form-factor restrictions and allows for charging over distance, efficiently and safely. It can also be applied to a wide range of applications because of these qualities.

However, while the possibilities of magnetic resonance are very exciting, the technology is frequently misunderstood by those not involved in the industry. It’s time to bust myths on what is reality and what is a pure myth, so consumers and engineers alike will know what to expect in their devices.

1. Magnetic resonance offers a poor user experience.

Magnetic resonance offers significant user benefits compared to the first generation of inductive-charging technology. Products on the market today charged via inductive require the device to be in direct contact with the source. In essence, that’s still tethering consumers to a specific spot if they want to use their devices while it’s charging.

Alternatively, magnetic resonance allows for charging at a distance, through materials—from wood and granite to skin (including body tissues) and water—and can charge more than one device at a time (like every device at your workspace). This superior user experience coupled with scalable power delivery to meet various applications of electronic devices make magnetic resonance the ideal solution.

2. Magnetic resonance is inefficient and slow.

Magnetic resonance can satisfy the charging needs of devices for a wide range of applications, from a wearable to an electric car. Because power delivered to a device isn’t limited by the device-side battery-charging system, there’s actually no difference in charging speeds for wired and wireless charging, meaning magnetic resonance still delivers on fast charging speed.

Well-designed magnetic resonance systems are very efficient, too. For example, electric vehicles enabled by this technology can achieve efficiencies as high as 94%, the same efficiency that can be achieved via state-of-the-art wired solutions. The Airfuel Alliance is the body that oversees magnetic-resonance technology to ensure these standards are being met.

3. Magnetic resonance isn’t safe.

A common misconception about magnetic-resonance technology is that it’s not safe. Perhaps because these systems can deliver energy over mid-range distances, consumers assume they’re being exposed to potentially dangerous electromagnetic fields. In reality, the relatively low-frequency electric and magnetic fields of a magnetic-resonance system design are kept below established and long-standing human safety limits (often specified by global regulatory bodies such as the ICNIRP and FCC). These regulate all electromagnetic consumer devices, including Bluetooth headphones, cell phones, radio transmitters, and wireless routers.

4. Magnetic resonance causes damage to products with RFID.

To properly function, RFID devices use magnetic fields. Consequently, RFID tags may be damaged when exposed to magnetic fields of the strength used for wireless energy transfer. Given this, magnetic-resonance systems are available that detect the presence of RFID tags and provide user notification so that corrective action can be taken. The AirFuel Alliance resonant standard is incorporating and evolving this functionality to ensure that basic safety functionality is built into all products.

5. Magnetic resonance can’t be used in products with metal housings.

Many people assume that magnetic resonance can’t be embedded in products that are either built with, or have, a metal case, because the metal blocks electromagnetic fields and currents induced in the metal may cause it to heat up. This isn’t true, though. The AirFuel Alliance utilizes electromagnetic waves at 6.78 MHz, which will not heat up most common metal objects, even those in close quarters to the device like coins or car keys.

Devices with metal housings can be charged via magnetic resonance even if the device needs higher frequency magnetic fields, as it takes advantage of apertures and seams that may already be present in the housing. This quality is very beneficial for engineers—it gives designers the freedom to express themselves and integrate magnetic resonance into their products with metal casings.

6. Magnetic resonance is so complex, it requires a PhD to build into a product.

Product integration of new technology is always complicated, and magnetic resonance used to be no exception. However, the maturity of industry standards via the Airfuel Alliance and the availability of purpose-built ASICs and associated market reference designs are allowing OEMs to easily and quickly integrate magnetic resonance in their products. No PhD required.

7. Magnetic resonance is expensive for designers to embed into products.

Early implementations of magnetic resonance based on off-the-shelf parts were not ideal for product companies from cost and size perspectives. However, purpose-built ASICs for magnetic resonance on the market today simplify the product integration and reduce the overall bill-of-materials cost for both the transmitter and receiver sides. Reference designs based on these integrated parts reduce the time to market and reduce the engineering efforts required to do product integration.

8. Magnetic resonance only works for my consumer electronics, and no other electronics.

A very common misconception is that magnetic resonance can only be applied to the consumer electronics space, such as low-power devices like a phone, laptop, or smartwatch. While this may hold true for other forms of wireless power technology—e.g., RF and inductive—magnetic resonance is different, as it’s efficient enough to work with high-power equipment. For example, a magnetic-resonance system can send 11 kW of power to charge electric vehicles. The technology can also enable wireless power over distance for other high-powered, electrified devices, from military drones to industrial robotic equipment.

9. Magnetic-resonance sources are always charging pads.

Wireless charging traditionally required a source that sends the power to the device. That source is often realized as a flat, two-dimensional surface referred to as a charging pad. While it may hold true for other forms of wireless power, magnetic resonance doesn’t limit the charging pad to that form factor.

Source resonators can be implemented on thin, flexible printed-circuit boards or formed into three-dimensional shapes to create a “charging volume.” Therefore, product designers are offered the flexibility and creativity to conceive the form factors to deliver the best user experience for their customers. Sources with very different form factors and IDs can be created, resulting in aesthetically pleasing sources and creating a better design to charge-up, say, wearables.

10. Magnetic resonance will make my product design bulkier and heavier.

Resonators for magnetic resonance can be fabricated on thin, flexible circuit boards, minimizing impact to the overall device shape and design. Furthermore, eliminating the charging port is extremely beneficial to product designers and their end users, because that gives them the freedom to create more innovative and unique device designs. It also eliminates vulnerabilities to water, sweat, or dust, enabling devices to be “life-proof.”

11. Magnetic-resonance-enabled devices won’t penetrate my life anytime soon.

The most common myth of all is that magnetic resonance is all buzz—just  a concept and a technology that won’t become a reality for decades. While the industry has been quiet over the past year or two, much development has been happening in the background. In fact, the first product enabled by magnetic resonance will be hitting the market this year, starting this spring with the Dell Latitude 7285, the industry’s first 2-in-1 laptop to enable a workspace free of wires.

By Sanjay Gupta, VP Product Management, WiTricity








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