No Need for Power Cords Now!
6月 16, 2016
Wireless Power is here and Multi-mode Solutions will Fuel its Adoption Rate
Wireless charging of cell phones
Wireless power has arrived! The 220 end-use products with embedded wireless power capability sold in 2015 provides evidence of this arrival. More recently, Dell’s demonstration of a 30 W wireless charging pad for laptops at Computex showed the expansion of this technology to mobile devices beyond the cell phone.
Companies the likes of Google and Facebook have declared that they are making charging stations conveniently available to employees. In fact, the wireless power market is estimated to grow at an 85% CAGR through 2020. It is clear that the design and manufacturing “engines” for wireless power production have started. We are on our way to realizing the prediction by Wireless Power Consortium’s (WPC) vice president of marketing development, John Perzow, when he “…envisions a phone that never dies since it will be continuously charged…It [phone] will be charging while you’re sleeping, driving, working, and practically any public place you decide to stay at.”
Of course cell phones are but one use for wireless power; everything that requires power to operate will be affected by this emerging technology. For example, another application is the charging of electric vehicles.
Wireless charging of busses, "on the fly" In fact, there is an experiment underway in England testing the wireless charging of electric buses between stops. Thinking even more broadly, in the home, wireless power systems can be embedded in walls, with repeater transmitters placed within the floor so that lamps, TVs, and other home gadgets never have to be “plugged in.” In military applications, soldiers outfitted with electric equipment can have their devices wirelessly charged while traveling to their mission. Uses for wireless power are numerous, ubiquitous, and long awaited!
No doubt, this is an exciting time and the future is promising for companies engaged in the wireless charging business. However, as with most new technologies that cross many end uses and involve applications that must have compatible transmitting and receiving devices, such as the cell phone, there must be standards to which products can be designed and manufactured in order to work with devices manufactured by others. Interestingly, as technologies emerge and get adopted, standards change (mature) as more and more is learned about end use requirements and technical capabilities of the underlying technologies.
Wireless Power Standards: In Search of the Best Technology
Such a “honing” of standards is underway with wireless power transfer. There are currently two prominent wireless power standards for the mobile device market: the Wireless Power Consortium (Qi) standard and the AirFuel™ Alliance standard, which emerged from the merger of the Alliance for Wireless Power (A4WP) and the Power Matters Alliance (PMA) consortia. The two standards are based upon two different technologies for accomplishing wireless power transfer. The Qi standard based on inductive coupling technology uses a low frequency (200 kHz) approach, whereas AirFuel standard uses a magnetic resonant technology and has both low frequency (100 kHz through 315 kHz) and high frequency (6.78 MHz) requirements.
In terms of getting to the market, the Qi standard was first and occupies the lead in terms of number of receiving devices (e.g. cell phones) having Qi-compatible receiving capability. Qi technology requires tight coupling, meaning that the receiving unit must be placed fairly precisely and close to the unit transmitting power. Only one device can be charged for each transmitter. These are severe limitations for Qi standard devices.
In contrast, the AirFuel standard, which followed Qi devices to market, rely on highly resonant magnetic technology which has the capability of the transmitting unit and receiving unit being loosely coupled – precise location of the receiving unit to the transit unit is not necessary, making charging truly “drop-and-go” possible. The AirFuel standard allows simultaneous powering/charging of multiple devices in a loosely configured array and an increase in the distance at which devices can be powered. In addition to being very safe to humans, magnetic waves can pass power through solid surfaces, thus making it possible to have the transiting coil built into or placed under a surface and retain the ability to charge devices on the top of the surface.
Alex Guzen, CEO of WiTricity, which is one of the pioneer companies in, and strong proponent of, magnetic resonance for wireless power transfer points out that as the technology evolves, companies looking to take solutions to market will rely on standards to streamline development, reduce costs, and accelerate adoption. In opinion of the AirFuel™ Alliance, the AirFuel standard is causing companies to rethink the way power in the mobile age is obtained. And because AirFuel is intelligent, it opens the door to a future of “smart charging zones” that will enhance the user experience.
Two Standards Accommodated with One Solution
As noted Qi was first to market, whereas AirFuel has more promise for meeting the requirements of the end users. This is the dilemma; is the implementation of wireless power transfer engaged in a battle of standards, another BetaMax vs. VHS struggle with a winner and a loser? Has the proliferation of wireless power products using different standards for mobile applications leading to consumer confusion and hindering adoption while a universal standard evolves.
The answer is no! Companies such as Semtech (Triune Systems) and Neosen have introduced multi-mode power transmitting units that have two amplifiers that can be called upon to charge devices based upon the standard used in the receiving device – low frequency, Qi and PMA, or high frequency, AirFuel devices. The power amplifiers of these early multi-mode transmitting products are using high frequency EPC’s eGaN FETs and ICs for the high frequency AirFuel transmitter.
Furthering the concept of a multi-mode device, EPC has introduced a 10 W, single highly efficient ZVS Class-D power amplifier evaluation kit (EPC9121) based upon an eGaN IC having three high frequency FETs in a single chip. The advantages of this single amplifier approach includes the need for only one transmitting amplifier (PTU), it is easy to use, low cost, and the amplifier works with all the standards – WPC (Qi) A6 and AirFuel Class 2 compatible.
No stopping the adoption of wireless power now!
It may take time for the market to settle on a single standard for wireless power transfer, if it is even necessary. With multi-mode power amplifiers transmitters being able to work with receiving devices based upon low frequency or high frequency, the emergence of wireless products and their adoption in the market need not slow down.
As WiTricity CEO Alex Gruzen has noted, "There will be multi-mode products in the transition to a single standard, but this is not unusual when innovation is coming from different directions." Until a single standard becomes a reality, using a multi-mode transmitting solution will permit the use of devices regardless of the standard used for wireless power transfer.
The time has come…cut the power cords!