Researchers at the Korea Advanced Institute of Science and Technology have developed a new system for the first time allows for omnidirectional wireless charging of multiple mobile devices from distances of up to one-half meter away.
Their new wireless-power transfer (WPT) technology makes it possible for laptops, tablets, and smartphones to have their batteries replenished at any location and in any direction, even if the devices are away from the power source. The technique is similar to WiFi.
Professor Chun T. Rim of the Nuclear and Quantum Engineering Department at KAIST and his colleagues explained that their system works as long as mobile users remain in a designated area where the charger is available – an area known as the Wi-Power zone. Doing so will allow their devices to collect power automatically, without being tethered to a charger.
Using magnetic dipole coils to generate magnetic fields
Furthermore, Rim’s team said their WPT system is capable of powering-up multiple mobile devices at the same time and from any position in the Wi-Power zone. It will work even if users hold their phones in midair or have their laptops stationed more than a foot away. Their research was published in the June edition of IEEE Transactions on Power Electronics.
The KAIST researchers demonstrated the technology on Tuesday at a lab on campus, using high-frequency magnetic materials in a dipole coil structure to build a thin, flat transmitter system shaped like a one square meter-sized rectangle. Their device is capable of charging either 30 smartphones with power capacities of one watt each, or five laptops with capacities of 2.4 watts each. The maximum power transfer efficiency for the laptops was 34 percent.
The team used a device they developed last year, the Dipole Coil Resonance System (DCRS), to induce magnetic fields. The device is composed of a pair of magnetic dipole coils – one for transmitting calls (Tx) and one for receiving them (Rx) – each with a ferrite core and connected with a resonant capacitor.
The coils were placed in a parallel position so they could generate rotating magnetic fields, enabling mobile devices to receive a power charge from any direction. While their device is not the first wireless charger, the KAIST team said it’s the first to offer a substantial advantage over traditional charging technology, since it has a larger charging distance and does not require devices to be in close contact with the transmitter (a charging pad).