Nikkei Electronics Asia --July 2010
Feature
Consortium Draws up Transmission Specs for Wireless Power to Mobile Gear

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Jul 1, 2010 00:03 Hideyoshi Kume

An industry standard for wireless power supply to smartphones, digital cameras and other portable equipment has been drawn up by major mobile telephone manufacturers and other firms. The standard was announced by the Wireless Power Consortium (WPC), an industry body working on wireless power standardization, in April 2010.

The WPC membership includes major handset manufacturers such as Nokia Corp. of Finland and Samsung Electronics Co., Ltd. of Korea, as well as Li-ion rechargeable battery manufacturer Sanyo Electric Co., Ltd. of Japan. A large number of members are companies with considerable influence in the mobile equipment sector, and the WPC is being closely watched as a result Note 1).

Note 1) 42 other members include Texas Instruments Inc. of the US, Duracell of the US and Rohm Corp of Japan (as of May 10, 2010).

The newest WPC standard covers the transmitter and receiver configurations and control protocols needed for contactless power supply to a piece of mobile equipment. Power transmission is implemented through electromagnetic induction, with a range of several mm and a frequency waveband of 100kHz to 200kHz. The group plans to formulate standards covering spurious emission and safety, such as preventing effects on the human body by electromagnetic waves, for individual regions.

The WPC has already provided all members with the transmission specifications for equipment with outputs of 5W and below. Product development is thought to be under way now, with the first products expected before the end of 2010 from multiple vendors.

The transmission specification supports charging control, and safety has been heightened by assigning control to the receiver (Fig.1). After the transmitter verifies the target piece of equipment is present, it verifies and charges it in response to commands from the receiver.

Fig.1 Control Managed by Receiver
Diagram shows wireless power system control. The receiver first calculates the needed rechargeable battery charge from output load information such as residual charge, and passes the result to the transmitter (1). The transmitter begins power transmission accordingly (2). Diagram by Nikkei Electronics based on material courtesy WPC.

The announced standard has three parts, namely Interface Definition, Performance Requirements and Compliance Testing. Multi-vendor charging will be possible as long as the requirements given in all three parts are complied with.

According to a source at Philips Electronics Japan, Ltd. of Japan, "By about summer 2010 all three standards will be complete. We plan to offer compliance verification testing through two or three test organizations to start" Note 2). The market is gradually getting ready to handle the new products.

Note 2) Philips is a core member in the WPC.