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POWER MANAGEMENT Fig. 2: On the left (in red) is a wireless charging station based on resonant power transfer technology. On the right is Qi wireless charging station using inductive power transfer technology. (Source: EE Times/Junko Yoshida) charging a Google Nexus 7 wirelessly took nearly three times as long as using a power adapter. Trade groups of chip makers and patent holders back different charging platforms. The Wireless Power Consortium (WPC) backs inductive and bridge solutions, while the Association for Wireless Power (A4WP) champions resonance. Seeing the writing on the wall, the Power Matters Alliance has moved to embrace resonant charging, as well. The startup Humavox is going it alone with an approach that is based on what it calls radio frequency charging. Still, market watchers say other players and technologies could emerge before the dust clears. “In the future, it’s possible that technologies which offer the consumer even more freedom of space and distance to charge wirelessly - RF perhaps being an example of this - will enter the market and compete with resonant technologies,” Sanderson said. Advancements are likely several years out. “In my opinion, it will be difficult for a new technology to enter the market once an infrastructure is in place, and therefore, if one technology is adopted in volume in the next two years, it is likely to remain the technology of choice for the future.” Last year, 20 million wireless charging receivers were shipped, and though most of them were inductive, Sanderson expects the market to grow to 700 million devices in four years. Inductive and resonant wireless chargers will ship in 2014, with resonant/bridge solutions expected to ramp up in the second half of the year. A standard is “not taking up faster because folks are confused by the existence of what appears to be competing standards,” John Perzow, the WPC’s vice president of market development for Wireless Power Consortium, told us. “The wellknown standards - Power Matters Alliance, A4Wp, WPC - those differentiating is making it hard for groups to combine… They don’t share communication protocol. They won’t talk to each other.” But consolidation is necessary before the technology can become ubiquitous. Only inductive and radio frequency products are available to the public, with Qi inductive technology built into products such as the Samsung Galaxy S4, Nokia Lumia 920, and Google Nexus phones and tablets. Major market players such as Broadcom, HTC, and Samsung are among the members of both industry groups. Magnetic induction currently has the wireless charging market cornered and is available in Google, Samsung, and Nokia devices. Induction typically uses two magnetic coils - a primary wire coil with an alternating electromagnetic field from within a charging base station, and a secondary coil in the device to convert power from the electromagnetic field to electrical current to charge a battery. Together, the coils create a transformer. “If you design it right - the right frequency and material, the quality of that coil - you can get very efficient power transfer and design for specific distance or power,” Perzow said. Several companies have taken to inductive charging. Samsung’s Galaxy S4 supports Qi, as has Google and Nokia. Perzow said the WPC has more than 40 million wireless devices on the market and has support from the semiconductor industry, Ikea, and Verizon. The WPC offers close coil inductive technology, which draws up to five Watts and operate at 200-300 kHz. Perzow said the WPC’s Qi technology can extend the charging range up to 40 mm away from the power source with 70% power efficiency. Qi and inductive charging have been touted for having protected connections, being safe enough for medical devices, and harboring low radio frequency interference. However, inductive charging is accused of being more delicate and more inconvenient than other types of charging; users have little freedom and must line up a device precisely with a wireless charging pad. “I think there’s something to that, but the assumption is that Qi is close couple inductive, and it will be that way forever, and that’s not the case,” Perzow said. “It is a constantly evolving technology. Qi is not a product. You can’t spec it.” Though the WPC and Qi are currently synonymous with inductive charging, the WPC also demonstrated resonant technology at the 2014 International CES. Dubbed WoWz, the technology is backward compatible with Qi and charges at a distance of up to 18 mm with 65% charging efficiency. “Samsung has Qi phones out there today and is also an investor in a company that is developing resonance technology that is in WPC,” Perzow said. “It’s reasonable to guess that Samsung will have resonance technology in their phones.” A WPC member and phone maker will debut a PMA+Qi compatible wireless charging system in 2014. He expects more bridge products in the coming years. “For a short term, it can work, but as soon as one standard can develop significantly, it’s going to be impossible for that approach to work.” MediaTek, a member of WPC and PMA (now in partnership with the A4WP) debuted its own wireless charging technology at the CES - a dual-mode charging solution that supports Qi Fig. 3: A4WP demonstrates resonance charge pad technology. (Source: A4WP) 26 Electronic Engineering Times Europe March 2014 www.electronics-eetimes.com


EETE MAR 2014
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