Omnidirectional wireless charging up to half a meter away from a power source

July 8, 2015

Omnidirectional wireless-charging system can charge multiple numbers of mobile devices simultaneously in a one-cubic-meter range. Above: charging transmitter; below: a Samsung Galaxy Note with embedded receiver. (credit: KAIST)

A group of researchers at KAIST in Korea has developed a wireless-power transfer (WPT) technology that allows mobile devices in the “Wi-Power” zone (within 0.5 meters from the power source) to be charged at any location and in any direction and orientation, tether-free.

The WPT system is capable of charging 30 smartphones with a power capacity of one watt each or 5 laptops with 2.4 watts.

The research team used its Dipole Coil Resonance System (DCRS) to induce magnetic fields, composed of two (transmitting and receiving) magnetic dipole coils, placed in parallel. Each coil has a ferrite core and is connected with a resonant capacitor.

Current wireless-power technologies require close contact with a charging pad and are limited to a fixed position.

The research was published in the June 2015 on-line issue of IEEE Transactions on Power Electronics.

KAIST | KAIST Omnidirectional Wireless Smartphone Charger at 1m

Abstract of Six Degrees of Freedom Mobile Inductive Power Transfer by Crossed Dipole Tx and Rx Coils

Crossed dipole coils for the wide-range 3-D omnidirectional inductive power transfer (IPT) are proposed. Free positioning of a plane receiving (Rx) coil is obtained for an arbitrary direction within 1m from a plane transmission (Tx) coil. Both the Tx and Rx coils consist of crossed dipole coils with an orthogonal phase difference; hence, a rotating magnetic field is generated from the Tx, which enables the Rx to receive power vertically or horizontally. Thus, the 3-D omnidirectional IPT is first realized for both the plate type Tx and Rx coils, which is crucial for practical applications where volumetric coil structure is highly prohibited. This optimized configuration of coils has been obtained through a general classification of power transfer and searching for mathematical constraints on multi-D omnidirectional IPT. Conventional loop coils are thoroughly analyzed and verified to be inadequate for the plate-type omnidirectional IPT in this paper. Simulation-based design of the proposed crossed dipole coils for a uniform magnetic field distribution is provided, and the 3-D omnidirectional IPT is experimentally verified by prototype Rx coils for a wireless power zone of 1 m3 with a prototype Tx coil of 1 m2 at an operating frequency of 280 kHz, meeting the Power Matters Alliance (PMA). The maximum overall efficiency was 33.6% when the input power was 100 W.