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In late 2008, the Wireless Power Consortium (WPC) began supporting an inductive-coupling standard. Since that moment, large companies competing in the portable-electronic-device (PED) market have been struggling to define an effective and universal standard to deliver power wirelessly to their devices (Fig. 1). Other standards associations, such as the Power Matters Alliance (PMA; an inductive-coupling standard) and Alliance for Wireless Power (A4WP; a magnetic-resonant standard) also have considerably large companies backing their efforts.

As recently as October of 2013, the IEEE Standards Association announced the IEEE Wireless Power and Charging Systems Working Group (WPCS-WG). Its goal is to control the standards for wireless power transfer (WPT) and help lead a unified front for developing WPT technologies starting with inductive coupling. With so much activity, many are trying to discern why there is such a struggle over WPT systems, the difference between all of the standards, and the impact of WPT on design engineers.

WPT was the brainchild of the wily scientist and showman, Nikola Tesla. His grandiose vision led him to build a WPT tower system that was meant to transmit energy across the globe in 1901. (Wardenclyffe Tower, which was located in Long Island, N.Y., was demolished in 1917.) Much has changed in the WPT world since 1901. The goal is no longer to transfer huge amounts of energy over vast distances with massive towers, but to transfer just enough energy to useful devices over very short distances.Gazing At The Tiers of Wireless Power Solutions, Fig. 1

Building a smart and efficient WPT infrastructure for highly diverse and numerous devices wasn’t economical until computers started fitting into pockets, as there was no demand or real use for such a system. With estimates of yearly PED sales at the hundreds of millions and growing, many companies with their fingers in the PED pie are trying to catch up with accessories and increasing accessibility for these devices. According to Mark Hunsicker, Senior Director of Wireless Power Solutions for Qualcomm, “From Qualcomm’s perspective, smartphones were the catalyst.”

As the computational capability of PEDs increases far beyond battery technology’s capacity to provide safe and adequate power with reasonable charging times, consumers and manufacturers of PEDs are looking for other ways to keep PEDs running. This conundrum has led to a scramble as top companies like Duracell, Procter & Gamble, Qualcomm, Samsung, LG, Energizer, Starbucks, Nokia, and hundreds of others either create their own standards or jump on board with other large companies’ standards. Meanwhile, the standards organizations—WPC, A4WP, and PMA—are vying for technology presence within PEDs to decide what standard will dominate.  

Gazing At The Tiers of Wireless Power Solutions, Fig. 2Both the PMA and WPC standards operate in the hundreds-of-kilohertz range using two inductively coupled coils. Although they exhibit highly efficient energy transfer, they require close physical proximity with exact placement. A lack of interrupting objects also is required, as they can even heat metal objects in the near vicinity. The A4WP standard, Rezence, operates at 6.78 MHz within the Industrial, Scientific, and Medical (ISM) band and uses magnetic-resonant technology (Fig. 2). For a WPT system, magnetic resonance allows for efficient power transfer and position flexibility within several inches vertically/horizontal, through surface charging. These aspects permit incorporation into existing work surfaces. WPT systems also can provide higher power rates for hungrier devices.

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