Qi wireless charging spec gets more flexibility with distance extension

The industry group is working to enable 2,000-watt power transfers for large appliances

The most popular wireless charging spec, Qi, which is supported by brands such as Duracell's PowerMat and Energizer, has gotten an extension to its specification allowing it to charge devices at short distances.

Various Qi-charging pads and mobile devices are backward compatible with the new resonant extension to the wireless charging specification (source: WPC).

The Wireless Power Consortium (WPC), the industry group supporting the Qi (pronounced "chee") specification, has added a magnetic resonant extension of the Qi specification's inductive charging technology.

The WPC said it is also working on enabling Qi wireless power transfers of up to 2,000 watts for kitchen applications. The Qi spec transfers 5 watts of power for enabled mobile devices, such as the Galaxy S4 and S3, Nokia Lumia 1020, LG G2, Motorola Droid Maxx and Mini and the Google Nexus 5 phone and Nexus 7 tablet.

The extension allows devices to be charged at distances of about 1.75 inches from a charging pad. That distance allows mobile devices to be more loosely placed around pads in order to charge rather than needing to be placed in an exact spot to receive power.

"It is clear there is room to safely and efficiently push the distance and power limits within the Qi specification," Menno Treffers, chairman of the WPC, said in a statement. "And with more than 50 million receivers in the market and 500 certified products, Qi is well-positioned to continue its market leadership as it drives forward the global wireless charging ecosystem of manufacturers, innovators and end-users."

The WPC with its Qi specification is up against two other industry organizations with their own wireless charging protocols: the Power Matters Alliance (PMA) and the Alliance for Wireless Power (A4WP.

Earlier this year, the PMA and A4WP announced a deal to adopt each other's technologies enabling both to have resonant charging at distance, among other capabilities.

Both inductive and resonant coupling use two separate copper coils to create a magnetic field to transmit electrical energy. When a receiving device (embedded in a smartphone) is tuned to the same frequency range as the transmitting device, a magnetic coupling is created and electricity can pass between the two.

The integration of resonant charging into the already present inductive technology within the Qi specification gives users the option to discreetly embed wireless chargers deeper in structures, like furniture and desktops, or utilize direct-contact, low-cost surface applications, the WPC said.

The magnetic resonant extension is backward compatible for mobile devices already enabled for the more tightly coupled inductive charging now being used by Qi-style charging pads.

The WPC said it has demonstrated power transfer at up to 30 millimeters (mm), compatible with today's Qi v1.1 receivers, and that five different WPC member companies demonstrated charging at a distance of 45mm using prototype Qi v.1.2 receivers.

Lucas Mearian covers consumer data storage, consumerization of IT, mobile device management, renewable energy, telematics/car tech and entertainment tech for Computerworld. Follow Lucas on Twitter at @lucasmearian or subscribe to Lucas's RSS feed. His e-mail address is lmearian@computerworld.com.

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Copyright © 2014 IDG Communications, Inc.

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