DoCoMo Shows Wireless Cell Phone Power Recharging

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Japan's NTT DoCoMo unveiled on Tuesday a prototype cell phone that charges without wires. The phone is based on a new wireless power standard called "Qi" that promises to replace charging cables and power-brick adapters for most of today's portable gadgets.

The Qi system (pronounced "chi") transfers power by induction. Electricity flows when a wire coil in a gadget, in this case a cell phone, is aligned with an energized coil in a charging pad. In the DoCoMo demonstration the charging pad was built into a table top and the cell phone just had to be placed on the pad for charging to begin.

In addition to the cell phone with an embedded coil, DoCoMo showed two other prototypes. One was a cell phone battery with an integral coil. This could be fitted into existing cell phones that don't have the required coil to allow wireless charging. The other was a portable back-up battery pack with the coil.

Charging time is about the same as a standard wired charger, a representative of NTT DoCoMo said during the demonstration, which was done at Japan's Ceatec electronics show.

The charging pad has a single coil that moves to align itself with a device that is placed upon it. When two phones are placed upon it the charging coil aligns itself with the first phone and, when charging is complete, it moves over to charge the second phone.

None of the prototypes are ready to be commercialized, but a DoCoMo representative said actual products "weren't too far away."

The prototypes were developed with Sanyo Electric, which is a member of the Wireless Power Consortium (WPC) that is developing the technology.

The WPC began developing the technology in late 2008 and published the first version of the standard earlier this year, said Camille Tang, chair of WPC Promotion Group, in a telephone interview.

The first version of the standard targets devices that require 5 watts or less to charge, such as mobile phones, Bluetooth headsets, digital cameras and TV remote controls, she said.

Commercial devices based on the Qi standard are already on the market. Energizer offers a charging pad and Qi adapter jackets for the iPhone and BlackBerry smartphones. And more are on the way from other vendors, said Tang.

The group has worked hard to make the system as efficient as possible, and Tang says in use it will match that of a typical power brick.

While the wireless power system loses some energy in the inductive coupling, it roughly equals the amount of electricity wasted if a power brick is kept plugged into the socket when it's not being used. Tang said that's common in most homes so the systems should match each other in overall efficiency.

Members of the Wireless Power Consortium include some big-name portable electronics producers like Nokia, Olympus, Research In Motion and Philips, and there are also chip makers like National Semiconductor and Texas Instruments. It appears to have few competitors.

Several other companies have already launched wireless charging systems, but they are based on proprietary systems and are not necessarily compatible with devices from other companies. Qi offers a standard that ensures interoperability, said Tang.

The standardization of wireless charging is expected to help push the market to US$4.3 billion by 2014, according to recent research from InStat. It found 44 percent of respondents to a survey expressed annoyance with current mobile charging systems and up to 40 percent were willing to pay up to $50 for a wireless charging system.

With the standardization of the 5-watt version, the consortium has shifted its focus towards larger portable electronics products, such as video cameras and laptop PCs.

"We are now forming the next standard work group that will cover medium power devices from 50- to 120 watts," said Tang.

Martyn Williams covers Japan and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is

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