The researchers say the platform could be used to charge multiple devices with competing standards

Multi-frequency wireless charger handles differing standards

A wireless charger that supports multiple frequencies in order to charge devices with different standards has been developed by electrical engineers at the University of California.

The charging platform could be used to charge smartphones, smartwatches, laptops and tablets 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 the study’s lead, professor Patrick Mercier.

There are currently three competing wireless standards: Qi, Powermat and Rezence, which are all incompatible with each other. Qi and Powermat operate at around 200kHz while Rezence operates at 6.78MHz.

A wireless charger's ability to operate at a particular frequency depends on its transmitter coil. Wireless charging generally requires the charger's transmitter coil to send a high-power signal out to a compatible receiver coil in the device.

Existing wireless chargers are typically built with a transmitter coil that's only optimised to work at one frequency and is extremely inefficient when operating at others.

The new, multi-frequency prototype is a thin rectangular box (12.5cm × 8.9cm) that contains two transmitter coils: an inner coil optimized to operate at a frequency of 200kHz and an outer coil optimized to operate at 6.78MHz.

The researchers also included a filtering circuit that prevents the coils from interacting with each other and causing efficiency losses.

The researchers say the lack of a unified standard could result in a technology battle similar to that which recently took place in recent years between Blu-ray and HD DVD or the 1980s battle between VHS and Betamax.

"To help avoid such a situation, 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.

The researchers have filed patents on the technology and are looking for commercial partners to help bring the universal wireless charger into the market.

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