(sethink, Pixabay)
14 October 2015. Engineering researchers designed a prototype device that can simultaneously charge mobile phones compatible with leading wireless charging specifications. Dukju Ahn and Patrick Mercier at University of California in San Diego describe their device in a recent issue of the journal IEEE Transactions on Power Electronics (paid subscription required).
Wireless charging of mobile devices simplifies the task by placing devices on a flat charging surface, rather than plugging each phone, tablet, or wearable device into a separate power source. But three different technologies for wireless charging developed in the industry, which means not all mobile devices will work with all wireless chargers.
Two of the three industry specifications, PowerMat and Qi, use inductive techniques transmitting power at a frequency of 200 kilohertz (kHz). A third specification, called Rezence, uses magnetic resonance and operates at 6.78 megahertz (MHz). Wireless chargers today are optimized to work efficiently with one of these specifications, which means they don’t work well or at all with other types of chargers.
In June 2015 the boards of two wireless charger industry groups — Power Matters Alliance and Alliance for Wireless Power — approved a merger to address this problem of competing specifications. Power Matters Alliance represents companies with the Powermat specification, while Alliance for Wireless Power represents the Rezence technology. As of mid-October 2015, the organizations are still working out their integration, including a name for the combined groups. A third organization, Wireless Power Consortium that represents the Qi specification, is remaining separate.
Mercier, who leads the Energy Efficient Microsystems lab at UC-San Diego and Ahn, a former postdoctoral researcher in the lab, are seeking a solution that can charge mobile or wearable devices meeting all three wireless specifications. In their paper, they describe a proof-of-concept prototype housed in a thin box 12.5 by 8.9 centimeters (4.9 by 3.5 inches). The box, say the researchers, can accommodate two smartphones side-by-side.
The box has two power coils, an outer coil that emits 200 kHz and an inner coil operating 6.78 MHz. The two coils are configured on the same plane, which keeps the charging device compact. Mercier and Ahn built and inserted a filtering circuit to prevent the coils from interacting, which could affect their efficiency.
The researchers tested the prototype charger with smartphones charging at 200 kHz and 6.78 MHz, including both types of devices simultaneously. They report the wireless charger delivered power with 71 percent at 200 kHz and 78 percent at 6.78 MHz.
UC-San Diego says Marcier and Ahn filed for patents on their device, and are seeking commercial partners to take the invention to market.
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