Wirelessly Power Hearable Devices with NFC2022-09-27T13:39:20-05:00

Wirelessly Power Hearable Devices with NFC

To Qi or Not To Qi: Introduction

NuCurrent has been driving the wireless power industry for over a decade, launched more product categories into mass production than any other company in the world, and developed a global reputation for technology innovation with over 150 patents and many contributions to global standards bodies like the WPC, Airfuel, and NFC. NuCurrent sets customers up for wireless power success by posing five essential questions to determine which wireless power transfer method will be most effective for hearable devices.

While Qi-based (inductive) charging is the best-known method of wireless power transfer, there are several other options for product developers to consider. In the To Qi or Not To Qi: Introduction video, NuCurrent explores and defines the different wireless power transfer methods available and details key terminology and concepts along the way.

(logo swoosh) Good morning and good afternoon and good evening to everybody from around the world joining us today. My name is Mike Harmon, I'm the Director of Marketing at NuCurrent and today I'm once again joined by my esteemed colleague and Senior Field Applications Engineer, Jason Luzinski for a topic that is clearly a popular one, what we call To Qi, or Not To Qi. I'd like to take a minute to address why I think this topic is so popular and why NuCurrent is a really good resource to address it. Wireless power and wireless charging means different things to different people. This is an emerging and high growth industry with a lot of different technologies and techniques and terminology and so on. So, for someone walking into this or even someone who's spent a little bit of time with it it can be pretty confusing and that's where NuCurrent comes in. We've been driving this industry for over a decade and we've launched more product categories into mass production than anyone in the world. And we've developed a global reputation for technology innovation with over 150 patents, granted (indistinct) many major contributions to global standards bodies like the WPC and AirFuel and NFC. We've developed a center of excellence with over 50 engineers representing RF mechanical, electrical, and software disciplines all serving major challenges in wireless power. And we do so in a way that we aim to be easy to work with and customer centric, which has qualified us to be among other things and an NXP Gold Partner. And ultimately we're driven to be the world's go-to resource for wireless power, which is why we put on programs like the ones that we have today. As we get started into the meat of this, we're really gonna dig into wireless power over the next hour and before we do we ought to review some important concepts excuse me, and terminology. So first on the left-hand side of the screen, we're gonna take a quick peak at transfer methods and the different types of methods of power transfer that are gonna be applicable for the conversation today. The first is low frequency, which is operating at 110 to 220 kilohertz via magnetic induction. And so Qi, which is, you know, the most well-known standard and method of power transfer is regarded as a low-frequency method. So we wanna make sure everybody understands that. Also Apple's new MagSafe protocol is a low frequency at around 360 kilohertz. Moving on to NFC which is a relatively new transfer method for wireless power operates at 13.56 megahertz and employs magnetic resonance. Similarly high-frequency using magnetic resonance is at 6.78 megahertz. We've got a high frequency solution as well that tends to map to what AirFuel has done as well as NuCurrent through our NuEva Development Platform. The next transfer method we refer to as a hybrid which is really sort of application specific but it employs both low frequency and high frequency. So inductive and NFC for kitchen appliances and the cordless kitchen through the Ki standard. And then lastly, the RF method of transfer which operates around 915 megahertz to 2.4 gigahertz using radio frequency power transfer. And so these methods are gonna come into play as we go through the different product examples that we have. But before we jump into those, there are some definitions and some terminology that I would like to have Jason walk us through so that everybody's aware of these terms as we talk about them through the products that we'd go through. So Jason, can you walk us through the concepts of magnetic induction and magnetic resonance for the audience? Yeah, sure. So magnetic induction is what we coined low-frequency technologies as we are operating like an air transformer where we are relying on coupling to deliver majority of the efficiency as we're trying to harness as many of the flux lines or the magnetic field lines going from the transmitter to the receiver. Magnetic resonance is a blend of a magnetic induction but it also has a little bit of more RF components attached to it such as energy storing items such as a tuning network that allow us to utilize and store energy to not have to rely on coupling as much. Magnetic resonance technologies are in the high frequency range of the NFC or 6, 7, 8, 13.56 megahertz. The next definition we are going to define is going to be antenna and coil. So we are gonna be talking about our RF wireless power technologies which rely on electromagnetic fields as opposed to just magnetic fields. So antenna will relate to something like a Bluetooth antenna, something that is able to harness the field similar to the RF technologies of 915 megahertz to 2.4 gigahertz, and the coil will relate to the inductor that we use for wireless power. The third definition we're gonna cover is coupling and mutual inductance. So this is related to the magnetic technologies. Essentially coupling is the ability of a receiver to capture a percentage of the magnetic flux that is created by a transmitter. This is usually on a scale from zero to one where one is you're capturing all of the fields and zero is capturing your none of the fields. Mutual inductance is the interaction between your receiver and transmitter coil. So essentially you have windings on both sides that are creating an inductance, the transmitter creates a field that generates a voltage on the receiver windings and that receiver winding actually, when you generate that voltage creates a current which inherently has an effect back on the transmitter. So, by understanding that value, you can kind of estimate the amount of power you're able to transfer over a certain area. Third item that we are going to define is foreign object detection. This is kind of an industry standard term where we're talking about as you're transferring power from a transmitter to a receiver and someone places let's say a coin or a key into the field, that is considered a foreign object, something that shouldn't be there. And we wanna be cognizant of these items because they cause safety issues and degrade performance of the system. The next term is charging infrastructure. This is related to the global standards that we have out currently, that is related to AirFuel to Qi to Ki and basically in terms of what is currently available the global leader in charging infrastructure is Qi. You know, all the pads that you see laying around the tables to charge your iPhone, or your Samsung phone, you know, those are related to the Qi charging infrastructure. And there's lots of great companies that are integrating these things into public spaces, so that as you walk around, you don't need to bring your charger anymore. you can just place it down and be able to charge, And the last term that we are going to define is proprietary solution or let's say closed ecosystem. All of these technologies can be developed into a proprietary solution for a specific customer. Now, if we talk about a larger ecosystem, such as Qi that is more charging infrastructure. So we want to create that separation between the two to ensure that you understand in certain situations where, you know, you really don't care about utilizing, for example, the Qi standards, but you want to be able to create your own ecosystem within a family of products, that's how we delineate the two. Jason thanks for running through that. The next slide here is just one of the things that really helps us focus. The session that we have today with some really useful questions and coming from outside the industry, this was one of the things that really helped develop my own understanding of how to map solutions to products. And there are two real breakthroughs I think in having these questions. The first is that we've got these five really smart questions that help quickly eliminate certain options and shine a light on what might be the best solution candidates. And then the next part about this is that based on the nature of the product, whether it's industrial design or its use case or the power levels, some questions are better asked first in this process than others. So we actually give ourselves the flexibility to do that. And as we go through the products that we have today we are gonna see that we approach all of these questions but we sometimes do them in different orders based on what we know about that product. So Jason, let's go through these questions and talk about the rationale for why they matter. So why would someone care about this first question? What is the size of the product and size of the antenna required when it comes to wireless power? So, this is one of the questions that I like to ask is because the size of the product will automatically dictate the maximum size of the receiver core. This will right away eliminate certain wireless power technologies due to the need for specific resistance and coupling characteristics to hit necessary thermal and user experience specifications. Great, so moving on to question two, what is the coil-to-coil distance and how many receivers need to be charged? So, wireless power requires appropriate mutual inductance which is a function of the inductance of the transmitter receiver and coupler. If the charge distance is greater than four to five millimeters, or requires a larger XY offset, it may be necessary to move to a high frequency technology as these do not rely on coupling as heavily as low frequency technologies. With this in mind, it is possible to eliminate certain tech paths based on the unique attributes of the product. Additionally, if there's a desire to charge multiple devices on a singular pad, high-frequency and NFC is usually the desired path due to the ability to operate under low coupling conditions. Great, so the first two are really about size and antenna related, the third one says, does the product need data transfer capabilities greater than 10 kbps? What's up with that? So, wireless power technologies have certain data transfer capabilities. Low frequency technology such as Qi was originally designed to be solely for power and the low frequency of operation limits the total data transfer through but about two kilobits a second from the receiver to the transmitter and on the order of bits from the transmitter to the receiver. NFC comes from a data background and with its higher frequency of operation at about 13.56 megahertz, allows up to 848 kilobits a second throughput. High frequency also supports in band communication up to about 10 kilobits a second. So, if that is a key requirement of a system, this question can be used to eliminate certain technologies. All of these technologies can potentially use auto band communication such as BLE, or ZigBee or a similar scheme, but this usually increases the cost and complexity of the system.
Great, so the next question,
do you need this product to be interoperable with existing infrastructure such as Qi?
This is an easy elimination question.
As of right now, there are only three viable charging infrastructure standards, Qi, NFC, and Ki. So if your product requires the use of an existing Qi charging pads, or wishes to use NFC data infrastructure, you can easily remove certain technology.
Perfect and then the last one,
what is the power level required to power or charge the device?
So power level is usually
one of the first questions you can ask to eliminate certain technologies. If the powers required is greater than three watts, you can immediately remove NFC and RF. However, if the power requirements is less than three watts, you know, you may need to start with a different question and to kind of touch on these five questions, the order that I asked them in is based off my previous experience being in the industry for six, seven years now and applying these questions to the different use cases of products that we see coming in. Wireless power is an interesting blend of mechanical, electrical, RF engineering, in addition to helping shape the industrial design and user experience of a product. So depending on the product that you're looking at you may have a different approach of how you ask these questions for a project that you're looking at. However, as we go through the presentation, I'm gonna give you an insight kind of how I approach this, but I urge everyone to look at the questions and understand what is really key and important for your product and the experience that you're trying to bring your end customers. (logo swoosh)

Hearable Devices

Choosing the right wireless power transfer solution for hearable devices such as Apple AirPods, Samsung Galaxy Buds, or Google Pixel Buds can be difficult. Due to the compact form factor, hearable devices have distinct needs and will likely demand a flexible antenna that can adjust to the extremely tight, narrow design. In To Qi or Not To Qi: Hearable Devices, NuCurrent explores the best wireless power transfer solution for hearable devices.

And this would be hearing devices. So this  would be... Imagine your earbuds, like you   might find from Apple or Samsung type devices.  Jason, can you walk us through these? Because I   think this is the first case where we're seeing  sort of multiple receivers in a product. So,   walk us through your thoughts here please. So, for hearing devices, first question,   what is the size of the product? And what's the  size of the antenna required? If you think of   an earbud, such as an AirPod or the Samsung  Galaxy Buds or the Pixel Buds, your sizes   of antennas are going to be very restricted.  In addition to that, due to the form factor,   you're more than likely going to need an  antenna that's flexible to adjust to the   extremely tight cramped design that these  products tend to have. As a result, I   immediately remove low frequency and low frequency  hybrid, just because of the magnetics required,   lots of windings, turns, relatively thick, and not  flexible. RF has a good potential solution here,   because the antennas can be printed on flexible  substrates, they can potentially be onboard chips.   And the similar thing for NFC and High-Frequency,  we're talking about nanohenrys. So,   one couple turns only on a flexible substrate.  This allows us to integrate and not have to   change the industrial design of the product. Great. And so moving on to the distance between   receivers and the number of receivers, this  seems to be a departure from the other things   that we've talked about. That's correct. So   earbuds, you have to have them, basically you  need to be able to charge two different devices.   With RF, the radio frequency wireless  power, you have the ability to charge these   multiple devices at once. One of the interesting  things here though is, if you look at the use case   of earbuds and what people are used to the gold  standard right now is the Apple AirPods. Everyone   has the case, the case prevents you from losing  your AirPods. And as you place them in there,   they snap, they feel good, and you know that you  always have them with you. One of the issues that   you would run into with RF in this specific  application is that, if you are trying to   charge your AirPods while they're inside  your case, it becomes very difficult   because RF still has kind of line of sight. You're going to have lots of metal inside the   product, that'll prevent you from hitting the  necessary power levels you're looking for. If   you're wearing them in your ears, again you're  walking around the room, but you might not be   able to always get a charge. The second thing,  from an NFC standpoint, and from High-Frequency   standpoint, the fact that we are operating under  low coupling, we could potentially charge two   devices with one transmitter, reducing costs and  complexity of the system. In the form factors   that we're talking about, the small form factors,  the high frequency of operation also lends itself   to a better performance. That is why I give NFC  and High-Frequency also a thumbs up in this case.  We move to question three. It looks like when we  start talking about data transfer capabilities,   we're seeing some strengths in some  areas and some weaknesses in others.  That's correct. So the pogo pins on your earbuds,  or the little plates on the bottom of your   AirPods, have multiple purposes. Not only do they  provide power to charge your earbuds, they also   usually have a data path to enable  the case to talk with the earbuds,   understand the levels of battery that they  have, and other functionality that's necessary,   to give the user experience that you're  looking for. RF and NFC both have higher   data capabilities, that let you address  these issues similar to the wrist wearables,   to give the functionality that you currently have  using pogo pins, but now over a wireless link.   High-Frequency, we are limited 10 kilobits a  second, so that's enough for you. It might be able   to work, but if there's anything required greater  than that, we might have to use an out-of-band   communication technology, which a lot of these  buds already have. However, again, in a dead   battery situation, or a scenario where you don't  want to have crosstalk, it becomes difficult with   that lower data rate. So, that's why I gave the  thumbs up to RF and NFC as the main technologies.  Great. And so, now we start to look at question  four and the power levels. This reminds me a   little bit of the conversation about the  wrist wearables. What are you seeing here   with respect to power and charging the devices? So, let's think about the use case, your earbuds   are charging within a case. From an RF technology  standpoint, the size of the transmitters required,   and the cost of those to be placed inside  an earbud case, is a non-starter for me. If   you're talking about the use case where they're  in your ear and you walk into an RF enabled room,   there is potential that they'll trickle charge  appropriately, because the power levels are   relatively low. However, because of that first  scenario that I described, I give it a minus   because it just won't be able to match up to the  experience that people are currently expected.   With NFC, you have the ability to design a much  more cost competitive compact design that can fit   inside the earbud case, and provide a quick charge  similar to what the pogos are doing nowadays.   High-Frequency, it also gives you the  necessary power that we're looking at,   but there are some other considerations that you  have to look at, but it is a viable technique.  Great. And then the last bit again also reminds  me of what we looked at in the wrist wearables   from a interoperability and infrastructure  standpoint. Walk us through that one more time,   and why RF and High-Frequency might not offer  what you need, whereas NFC is strong there.  Like I mentioned earlier, the NFC form ratified   WLC, there are rumors that cell phones are  going to have NFC charging enabled in them.   So as you can see, the infrastructure for  these low powered devices is being developed.   For example, you forget your case at home, and  all of a sudden you need to be able to charge your   earbuds up quickly, being able to use a mobile  battery pack like your cell phone, is going to   be perfect for that application. Additionally, NFC  provides a lot of user experience as benefit as   well. Potentially being able to tap to pair your  earbuds, whether it's via the case or via how the   earbuds themselves, it gives an additional feature  that product developers can utilize to not only   improve the user experience, but also increase  the value that they're bringing to the market.  Perfect. Jason, thanks for running us through  that one. We have one more prepared, which is   shoes and insoles, but we promised our audience  that we would try to take a suggestion or two,   of products that maybe they're  thinking about or working on,   where we could run through this scenario kind of  on the fly. So, at this point in time, if there's   anybody that has a product that they'd like to  suggest, we might need to ask a few qualifying   questions, but if you'd like to suggest that and  put that in the chat, we can take a look at that.   So I'm seeing one suggestion, and this is  a growing category for wireless charging,   it's smart glasses. Jason, can you walk  us through that, describe the product   category a little bit and some of their  attributes related to size and power level,   and where you might need that out there and why? Yeah, of course. When I think of smart glasses,   I think of the user experience first. As a result,  the first question I'm going to ask myself is,   what is the coil-to-coil distance,  and how many receivers need to charge.   If you look at a pair of glasses, you have two  temples, and the glasses usually go into a case.   The temples can fold on either way, so you can  have the left one over the right one, or the   right one over the left one, which gives you a  lot of variability in your charging distances.   As a result, if you place your glasses into your  case, you want to make sure that they charge   every single time. So, the coil-to-coil  distance and the variability of that,   and potentially needing to charge two temples  at once, instantly makes me think of RF, NFC,   or High-Frequency. This addresses a lot of  that misalignment, the low coupling scenarios,   and the ability to charge multiple devices  at once, utilizing a single transmitter. 
The second question I would ask myself is, what  is the power level required for this specific  
type of product? From experience, we see  smart glasses ranging on the 500 milliwatt to   two watt range of power transfer. Because  of that, I'm going to have to nix RF,   just because it cannot provide the necessary  power, without the built-in infrastructure.   And even with the built-in infrastructure,  it's still very, very small amounts. So,   NFC and High-Frequency with their capabilities,  NFC up to three Watts, and High-Frequency more   than that, makes me move to NFC and High-Frequency  being the leading candidates of technology. The   third question I'm going to ask myself is, does  the product need data transfer capabilities   greater than 10 kilobits, a second? Glasses... You  want to be able to have a great user experience.   I'm thinking, being able to take your pair of  glasses off, and tap it to the back of your phone,   utilizing NFC to help pair your glasses  directly to your mobile device without any   worry, or being able to do the same thing with  the case. NFC, in my mind, takes the cake here.  High-Frequency still requires proprietary  in-band communication. The data levels are   lower, and if you do want to increase  it, you still have to use Bluetooth,   which NFC already has a leg up on, because  people implement tapped pair all the time.   Based off those three initial questions,  NFC is the clear path for me, for   AR smart classes at this time, to be able to get  something out to market, and give the experience   that people are looking for. Terrific, Jason, thank you.   What about a medical device or an  implantable device, Jason? There's been some   research and work done on that, NuCurrent has been  involved in that type of technology for some time,   how do you see an implanted device? So implanted devices are interesting.   One, the first question I'm going to ask myself  here is, what is the coil-to-coil distance   required? So, anytime you implant a device  inside the human body, you must account for   a certain amount of variability of the angles  and charge distances that you're going to get to,   different tissue thicknesses, different  levels of fat muscle, other tissue,   water content, are all going to affect the  wireless power transfer of an implantable device.   So when I look at this, I start to think, okay,  the distance is going to be relatively variable,   it's going to be a low coupling  situation. RF technologies cannot...   With the electromagnetic fields usually  attenuate extremely quickly in water,   so we have to rely on a magnetic based solution.  So that leads me to NFC and High-Frequency.  We have done quite a bit of models of different  frequencies within the body, and we found   through testing the different ISM bands, 13.5,  six and six, seven, eight megahertz that, six,   seven, eight megahertz tends to be more efficient,  and also provide easier methods of passing SAR   and other regulatory requirements. So from that  standpoint, I can eliminate a lot of the initial   questions, based off the coil-to-coil distance  and the environment that we're placing this in.   High frequency six, seven, eight would be  the appropriate technology for this kind of   application. We can go into power levels and data  capabilities, but based off that, it's easy to   eliminate the rest of the technologies. Very interesting, thank you Jason.

5 Essential Questions

  1. What is the size of the 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?

Hearable Device Solution

NuCurrent’s NuEva NFC platform delivers a premium wireless charging solution faster, with industry-leading performance and less risk.


  • Greater spatial freedom

  • Multi-device charging

  • Thin, efficient coils for small electronics

  • Large component ecosystem

Is Qi Charing for Laptops the Way to Go?

Qi-based (inductive) charging is the most popular form of wireless power, and for good reason. But there are many more power transfer methods to consider when deciding which is best for your device.

In this 60-minute session, NuCurrent will look into the different wireless power transfer methods available and walk through the tradeoffs that come with each method, followed by a recorded Q&A session.

The Power to Get to Production





QI: 15W

WHOOP mobile


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