Universal wireless charger in the offing

Washington :Researchers have developed a prototype ‘universal wireless charger’ that could be used to simultaneously power multiple devices such as smartphones and laptops.

The dual frequency wireless charging platform could be used to charge multiple devices at the same time – regardless of which wireless standard, or frequency, each device supports.

“To our knowledge, this is the only multi-standard wireless power transmitter that’s been shown to operate simultaneously at two different frequencies with high efficiency,” said Patrick Mercier, a professor at the University of California, San Diego, who led the study.

The study not only presents a “universal wireless charger” that can deliver power to multiple devices concurrently, it addresses an issue that afflicts existing wireless technology: incompatibility between the three competing wireless standards in today’s market.

Each wireless charger so far supports either the Qi, Powermat, or Rezence standard and will only work with devices that support the same standard.

“We developed a wireless technology that is universal and supports all of these standards so it won’t matter which standard your device supports,” said Mercier.

These three standards operate under different frequencies: Qi and Powermat operate at around 200 kHz while Rezence operates at 6.78 MHz.

Existing wireless chargers are typically built with a transmitter coil that’s optimised to work at one frequency. The chargers are extremely inefficient at other frequencies.

To address this problem, Mercier and his team built a charging platform capable of simultaneously operating across the frequencies supported by all three wireless power standards.

The prototype that they built is a thin, rectangular box (12.5 centimetres � 8.9 centimetres) that contains two transmitter coils: an inner coil optimised to operate at a frequency of 200 kHz, and an outer coil optimised to operate at 6.78 MHz.

One of the features of this design is that the coils lie in the same plane, allowing for a compact size. The platform is just big enough to fit two smartphones side by side.

Another important feature of the prototype is a filtering circuit that researchers designed to prevent the coils from interacting with each other and causing efficiency losses.

The researchers then tested the charging platform using two receiver coils (one optimised for 200 kHz operation and the other for 6.78 MHz), which served as models for two different smartphones.

Engineers demonstrated that the charging platform was able to deliver power to both receiver coils at the same time at efficiencies ranging from 70 to 80 per cent.

The receiver coils were also able to receive power regardless of where they were placed on the charging platform.
The study was published in the journal IEEE Transactions on Power Electronics.