Best Power Transfer Method for Wireless Charging Laptops

Best Power Transfer Method for Wireless Charging Laptops

To Qi or Not to Qi: Wireless Charging Laptops Introduction

NuCurrent has driven 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 countless contributions to global standards bodies like the WPC, Airfuel, and NFC. NuCurrent sets customers up for success in wirelessly charging laptops by posing five essential questions to determine which wireless power transfer method will be most effective for this use case.

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: Wirelessly Charging Laptops 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)

Wireless Laptop Charger: What’s the Right Approach?

Choosing the right power transfer solution for wirelessly charging laptops such as HP, Lenovo, and MacBooks can be difficult. Due to the compact form factor and power needs higher than Qi’s current capabilities, wireless chargers for laptops will likely demand a custom design. In To Qi or Not To Qi: Wireless Charging Laptops, NuCurrent explores the most effective wireless power transfer solutions for a wireless charging laptop.

So Jason, for this one, laptops,
let's imagine sort of a standard 15-inch laptop

from somebody like HP.

Why don't you walk us through how you would advise someone

on which type of transfer method would be appropriate

for this type of product?

So specifically for laptops,

the first question I ask myself is

what is the power level required to power

or charge the device?

Laptops tend to, you know, be in the higher power range

between the 30 Watts to a 100 Watts.

They have specific load requirements to be able to,

you know, for example, charge a laptop

and allow it to function with a dead battery.

So you need to consider both a battery charger

and also a power source.

Based off that, you know, you can immediately eliminate RF,

which is, you know, on order of a couple of milliwatts.

NFC, which has a maximum power transfer capability

up to 3 Watts.

And the hybrid low frequency, high frequency, which is key,

you know, that's on the order of kilowatts.

So it's a little bit of overkill for this application.

So in my mind, this brings us to low-frequency technologies

and high-frequency technologies.

Both have the capabilities of supplying up to a 100 Watts.

So they are the right starting points

for a laptop in this example.

Great, and so that takes us

to the next question.

And we've got in our coding here, in our matrix,

you'll see N's equal no and Y's equals yes.

When we have a Y-plus, that means that there's something

uniquely advantageous to that particular method.

And when you see a Y-minus, there's something there

that might be a cause for concern.

Not a complete deal breaker

but something that you need to be aware of.

So in the second question, Jason, so do you need

to be interoperable with existing infrastructure?

So, you know, looking at this specific question,

you have to kind of look at the product.

So laptops are fairly commoditized.

You can go out on, you know, Amazon,

buy yourself a $300 laptop.

And you want to be able to charge it.

So when you start thinking about infrastructure

specifically for this type of product, you need to consider

that do you want to provide a charger

which will increase the overall cost of your product?

Or do you want to be able to use something

like infrastructure which allows people

to not have to purchase their own?

So from that standpoint, Xi low-frequency tends

to have the edge up on this as the fact that it's become

the global standard for wireless charging at this point.

You know, there are multiple tasks forces within Xi

that are trying to address the laptop market.

And trying to address the medium power market.

On the other hand, with high frequency,

you know, there is the airfield standard.

Unfortunately, back in 2017 when Apple decided

to go with Xi, the airfield standard just did not get

the same traction as Xi did.

So even though there might be possibility going forward

with an infrastructure, there's just no current development

or state that is at the same level that Xi currently gets.

So in this case, this is why I give a low-frequency Xi

a plus compared to high frequency

just because it is more built out

and more, let's say, widely adopted at this point.

Yeah, so it's not that high-frequency

won't work, it's just that if they want to go that route,

they're going to have to supply a charger in the box

along with it because there's no

universal charging capabilities.

That's correct. Perfect.

So the next questions, Jason, three through four,

they're both tracking okay for low frequency

and high frequency.

Is there anything that you want to point out

about those questions with respect to this?

Yeah, so, you know, with low frequency, we are,

at the power levels we're looking at,

we'll more than likely have to go to a wire-rom technology

just to keep the resistance as low

at these higher power levels to ensure proper performance.

But looking at the general form factor of a laptop,

both high-frequency and low-frequency can have the space

to be able to integrate either a PCB or a wire-round coil

into the design.

So I gave both of these, you know,

kind of a level playing field, just due to the nature

of the design of the product.

With question four, what is the coil to coil distance?

And how many receivers need to charge?

High-frequency inherently lets you charge

at a larger distance.

But from a use case that you're looking for with laptops,

you know, when you're placing it on a desk,

you may have a pad, you may have something mounted

under the desk.

Both with the sizes of the coils that are possible

within the laptop, both of these technologies,

essentially are a level playing field.

High-frequency might have a little bit more spatial freedom

but at a cost of efficiency and potential EMI.

Low frequency, you might have to place your laptop

in a more fixed position.

But you would get the EMI and efficiency performance

that you're looking for.

So in this case, I give them both kind of a equal

on this question.

And then for the final question,

does the power need data transfer capabilities

greater than 10 kilobits a second?

Usually, the wireless power is not going to be used

as a data channel.

Laptops obviously have lots of different radios

and functionality through USB, and wifi, and Bluetooth.

So in this case, it's not really needed.

And that's kind of the last question here.

And why both low frequency and high frequency

are on the same level playing field.

So as we come through it,

this is really a (mumbles) option for laptops.

Which, you know, if you want to pursue

this type of product development,

Xi is a really strong candidate.

And of course, Nucurrents Nueva,

low-frequency development platform is there

for getting you to market quickly

while eliminating a lot of these risks that are,

that come with wireless charging development.

(upbeat music)

5 Essential Questions

  1. What are the size of the product and 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?

Solution for Wireless Charging Laptops

NuCurrent’s NuEva LF platform delivers a premium wireless charging solution faster, with better performance and less risk. Looking to develop a laptop with wireless charging capabilities? Our expert team can help.


  • Established global standard

  • Interoperability

  • Safety

  • 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.

Wireless Power Methods





QI: 15W

WHOOP mobile


Want to discuss a laptop wireless charger solution?

Want to discuss a custom low frequency solution?

Where do we go from here? You tell us.

Where do we go from here? You tell us.

Go to Top