Okay, Jim, we're onto the second method of wireless power transfer. This is a type of wireless power technology that's very near and dear to us at NuCurrent. Can you take us through the concept of inductive power transfer and tell us how it works? Yeah, Mike. So, right now, inductive wireless power is currently running away as the most dominant mode of wireless power charging, and that's because inductive charging has been adopted by all of the manufacturers of the largest battery-powered market segment today, and that's smartphones. When Apple adopted the Qi standard in 2017, it aligned and consolidated both the Android and iOS smartphone markets into the same standard, and that alignment removed any doubt from the transmit charger manufacturers which technology was going to be used. But before we get into the details of the Qi standard, let's talk about what inductive charging is. So, let's look at the diagram here that shows and inductive wireless power system. The term inductive refers to the fact that a magnetic field is generated by a transmitter device, and that magnetic field is picked up by a receiver device to deliver power as needed, typically to charge a battery. So, let's explain how it works. To generate a magnetic field, we simply need to push electrical current through a wire. Those of us with an electronics background will understand this is one of Maxwell's equations, known as Ampere's Law, that anytime you pass a current through a wire, a magnetic field is generated. To increase the amount of magnetic field, we can wind the wire in a coil shape with multiple turns, so each turn of the coil contributes to an even higher magnetic field that gets generated. So, that's a transmit coil you see on the left-hand side of the diagram. Now, if we take a second coil and we move it into the area of the magnetic field generated by the first coil, then there is another one of Maxwell's equations we know as Farraday's Law, that says a coil placed in a time-varying magnetic field will induce a voltage in the second coil. The time-varying part is key. So the ability of the coil to couple is based on an alternating current. To maximize coupling for inductive couple power transfer, you want them to be as close together as possible to maximize the coupling of the fields. Actually, ideally, you would like to have the exact same coils for both the transmit and receive coils, and you'll want them centered as much as possible and as closely together as possible. Once the size of the coils changes or they get offset from each other so they are not concentrically aligned, or the distance between them increases, the amount of coupling then starts to trail off and the amount of power drops. The inductive coupling is essentially an air transformer. The key is to try to maximize the coupling between the coils. The coupling coefficient, normally goes by the letter P, is normally between about 0.3 to about 0.7 on Qi systems. And what kind of power levels and distances are we looking at here, Jim? Well, the main wireless power standard is the Wireless Power Consortium's Qi standard, which is currently designed to transfer up to 15 Watts of power to a wide range of devices. The typical distance between the coils is quite small, typically about three to five millimeters, although last year, NuCurrent designed a new transmit reference design that could allow over 10 millimeters of coil to coil distance. That new, higher Z-distance transmitter can be seen on today's PopSockets Pop Power wireless charger, which was a unique design that allowed users of the popular PopSockets attachments to charge their phones wirelessly with the PopSocket still attached to the phone. Yeah, it's my favorite charger on the market, to be sure. What are some advantages and challenges with this type of, with this method of transfer, Jim? Well, the main advantages of inductive wireless power transfer is it can transmit a substantial amount of power. It is a simple concept that is quite cost-effective, and magnetic fields are generally localized and are quite safe. The human body is quite unresponsive to magnetic fields. However, there are a couple of key disadvantages to the Qi standard. The first, familiar to most people that wirelessly charge their smartphones, is the limited freedom of placement of the receiver. To properly charge, you only have a few millimeters of placement variability to have a successful Qi charging experience. It is a big convenience to just plop your smartphone on a charger and walk away, but occasionally, some users have complained that if they receive a text message on their smartphone and it vibrates and they're not there, the phone actually may move a little bit, and actually may move out of the charging zone. There are multiple coil solutions that are available to mitigate this risk, but overall, the placement accuracy is probably the main disadvantage of the Qi wireless standard. A second disadvantage of the Qi standard is the propensity of Qi chargers to heat up foreign objects like coins or keys or gum wrappers. Qi operates at a frequency around 120 kilohertz, which is a frequency that readily heats up small metal objects like coins due to skin effect. To protect against this, Qi has foreign object detection circuitry built into the standard to prevent unwanted excessive heating. This works adequately for the users, but is an added level of complexity to the designers. So you've already mentioned Qi and the Wireless Power Consortium already, Jim, so what is happening with the consortium, and kind of give us a snapshot of the state of the state there, and a little bit about where they're headed. Well, as I said, for inductive technology, the dominant body is certainly the Wireless Power Consortium. It is the main driver behind the Qi standard, and to date, there's been over 7,000 products that have been Qi certified and over a million new Qi-enabled devices ship every day, but there are several other charging standards under development by the Wireless Power Consortium to address higher power applications. For instance, inside the WPC is the Ki standard, that's K-I, which is under development to drive the wireless kitchen. So, imagine all your kitchen appliances in the future, from bread makers, coffee makers, mixers, even cooktops that can be placed on a kitchen counter and just start working with up to two kilowatts of power delivered without ever needing to be plugged in. That is the promise of the Ki kitchen standard under development by the WPC. It is also an inductive technology. Several kitchen manufacturers are contributing to the development of the standards, and it has already gained significant momentum. NuCurrent is very active in the standard and is supplying NFC modules used as a communication interface between the Ki transmitters and Ki kitchen appliances. Beyond the cordless kitchen, there is also work going on to extend the Qi standard to handle larger devices, such as tablets, notebooks, and laptop computers, while maintaining backward compatibility with the current Qi charging devices. There is also standards work going on for other more commercial and industrial spaces, including charging of medium power devices, which could include drones, light electronic vehicles, and power tools. So, what are some of your favorite applications of inductive charging that you've been involved in, Jim? Well, since NuCurrent is a member of WPC and I regularly attend WPC meetings, one of the most rewarding experiences was helping our client, PopSockets, develop the charger that can charge smartphones with their popular PopSockets attachment. For them, the popularity of wireless charging on smart phones was actually a threat to their vibrant business, and delivering a solution to them was very rewarding. We also has pushed Zeke gap limits for other clients, such as Honeywell, which was a product for a more industrial application used by today's UPS drivers that allows wireless charging of their handheld scanning devices. So, as you've mentioned, Jim, inductive is the dominant method of wireless power transfer at this time, and one that NuCurrent knows really well. What are your thoughts about what the future will hold for inductive charging? The future is certainly bright for inductive charging. It has gotten through the first big hurdle of any new technology by getting enough large players to align on a standard to generate critical mass. So, all the makers of the transmitter infrastructure don't worry about obsolescence or lack of operability between different large vendors. The future is now focused to drive to higher power, to allow faster smartphone charging, as well as charging of larger devices. The future is certainly very bright. Thanks, Jim. That wraps up Method #2, inductive wireless power transfer.
