Wireless Charging Heads Mainstream: Design Engineers Pay Close Attention
As you get ready for work, you tap the coffeemaker, the blender, your electronic toothbrush. Out the door, you’re wearing your smartwatch, Fitbit, Bluetooth headphones, and holding your smartphone and EV key.
Seems mobile. But you’re near-completely tethered. With only limited wireless charging capability.
We’re so accustomed to charging our devices; we’re not even aware of the degree to which we need wireless charging. Once that mindset changes and some of the technology challenges resolve, wireless charging will head to mainstream.
That’s why we wanted to interview Mike Harmon, director of marketing for NuCurrent—a client of IRI and the “world’s go-to source for wireless power” with more than 150 patents in its estate.
We asked for a quick tutorial on the current technologies available and how to know which to pursue.
Harmon briefly explains there are seven types of wireless charging power transfers in current applications: [for an excellent in-depth tutorial, we urge you to click on the link]
RF Wireless Power. We’re all accustomed to the low radio frequency of AM/FM radios, sending info with radio wave energy from point A to B using antennas. Although it offers incredible dynamic range, we still need to capture the totality of the radio signal itself to power at a distance, and that’s a problem. FCC limits RF to 4 watts. RF transmits a few feet or meters with milli- or micro-watt power. It can trickle charge low consumption devices, like game controllers or mice. But not smartphones.
The true measure of wireless power transfer would deliver capacity at a distance across the room, the house, or across town. But it is difficult to send enough power across distances without degrading or losing power. That’s why radio frequency power is a niche for low-power charging, and caution demands we don’t overhype it.
Inductive Wireless Power. Inductive wireless charging, the most dominant mode today, is adopted globally by manufacturers of the largest segment: smartphones. It uses electromagnetic induction to provide electricity to portable devices. The most common application is the global Qi (pronounced chee) standard developed by the Wireless Power Consortium. This low frequency method operates at 110 kHz and is the universal standard for smartphone charging.
Inductive charging is also a popular method for power tools, electric toothbrushes, and handheld computers. You can place the equipment on a charging station or inductive pad without needing to make direct electrical contact with a dock or plug. But the distance is limited, up to a few millimeters at most.
Even at low frequency, the Qi standard delivers substantial power, cost-effectively and safely. More than 7,000 devices are Qi-certified, and some million devices are shipped every day. NuCurrent recently designed the “world’s best-performing QI charger” for PopSockets, the popular smartphone accessory and world’s first Qi- certified extended range EPP charger.
As exciting, NuCurrent also developed a handheld scanning device using inductive wireless power for the handheld computers that many thousands of UPS drivers use to track their busy routes and stacked deliveries.
Additionally, a new inductive standard from the Wireless Power Consortium called Ki is emerging that foreshadows the arrival of the “cordless” kitchen, where all devices are powered without the clunky outlets on your designer tile backsplash—sure to please minimalist homeowners. As more large players enter the evolution, Ki promises higher powers for larger devices – up to 2.2 kilowatts.
Inductive Resonant Wireless Power. This power transfer is high frequency charging at 6.78MHz-13.56MHz and presents much lower coupling than inductive while maintaining more spatial freedom and greater flexibility for design engineers. Oddly, it has been around since Tesla but has recently gained momentum in usage. One of the special features of inductive resonant charging comes from its ability to support the charging of multiple receivers from a single transmitter such as imaging charging two hearing aids on a single charging surface.
Capacitive Wireless Power. Capacitive power transfer can be an attractive alternative to the traditional inductive power transfer method as it is lighter and lower than inductive. CPT consists of an efficient class-E resonant inverter and capacitive coupling formed by two flat rectangular transmitter and receiver plates. It’s a simple structure with no eddy currents, no coil windings, good misalignment performance; however, issues exist with high voltage, safety ozone production, and low power density. Potential applications for integrated circuits, biomedical devices, and LED lighting are possible.
Ultrasound Wireless Power. Think of power transfer via sound pressure. It is inefficient for any distance. Of all the wireless power transfer methods, ultrasonic is considered the most controversial. Currently, it is in the research and development phase, with no commercial products coming to market yet.
Laser Wireless Power. Lasers hold promise for true power at a distance, from NuCurrent’s viewpoint, especially when power cabling is unwanted. Of all the technologies available for wireless power transfer, the laser may work best for very low power IoT devices. Wi-Charge from Israel holds intellectual property and may see a bright future if safety issues resolve.
Improper use of lasers can cause blindness in humans and animals.
EV Wireless Power. Gasoline-powered vehicles may soon give way to all-electric or plug-in electric cars. Nearly one million EVs operate in the United States. And with the race to reduce global warming, significant growth in EV is anticipated. But the consumer experience needs to become similar.
Gas-powered vehicles ask you to fill up and take off. Four and one-half minutes it takes, and 168,000 gas stations dot the country. Convenient. EVs require time-consuming power transfers driven by impatient humans. It can take 11 hours to recharge your car overnight fully. One day, as EV wireless power evolves, you may only need to drive your car over a charging matt on your garage floor. And walk away. That will be a market-maker.
So, how do you determine which seven options are best suited for wireless power transfer to your product or ecosystem?
You can begin by asking five key questions, says NuCurrent, to help you evaluate which direction to take and how to weigh the pros and cons. Design engineers not yet working in wireless charging are paying close attention, as measured by attendance and comments at NuCurrent’s webinars.
Now, you have an excellent tutorial to take, robust use cases to read at www.nucurrent.com, and a handful of questions to get you started.
Five Foundational Questions
1. What is the size of your product and the size of the antenna required?
2. What is the coil-to-coil distance, and how many receivers need to charge?
3. Does the product need data transfer capabilities greater than 10kb/s?
4. Do you need this product to be interoperable with existing infrastructure?
5. What is the power level required to power/charge the device?
Wireless charging is in its adolescent size at a global USD 9.72 billion in 2019. Also, it’s an emerging market with the bounding energy of a solid young athlete.
Researchers predict the wireless charging market to reach USD 164.38 billion1 by 2030, only a spark away.
And even more bold predictions reside in the minds of NuCurrent’s advanced engineering teams, so we encourage you to stay close to the company, take the well-attended webinars, and sign up for informative blogposts.
To your success,
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