To solve the problem of compatibility issues in consumer electronics, U.S. researchers have developed a dual frequency wireless charging platform that could be used to charge multiple devices at the same time.
A team of Electrical engineers from the University of California, San Diego developed the new technology that can charge multiple devices, such as smartphones, smartwatches, laptops and tablets, from different brands at the same time – regardless of which wireless standard, or frequency, each device supports.
The new proof of concept, not only presents a ‘universal wireless charger,’ but also delivers 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 – Qi, Powermat and Rezence.
Conventional wireless chargers support either one of the standards and will only work with devices that support the same standard. The three standards operate under different frequencies: Qi and Powermat operate at around 200 kHz while Rezence operates at 6.78 MHz. In order for a single charging device to support multiple standards, the charger needs to operate across these very different frequencies.
A wireless charger’s ability to operate at a particular frequency depends on its transmitter coil, which sends out a high-power signal to a compatible receiver coil in the device-to-be-charged. Existing wireless chargers are typically built with a transmitter coil that’s optimized to work at one frequency. But as a consequence, the chargers are extremely inefficient at other frequencies.
To address this problem, Patrick Mercier, a professor in the Department of Electrical and Computer Engineering at UC San Diego, 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 centimeters × 8.9 centimeters) which contains two transmitter coils: an inner coil optimized to operate at a frequency of 200 kHz, and an outer coil optimized to operate at 6.78 MHz. Also, this design allows the coils to lie in the same plane, thus reducing the 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 the 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, 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%.
Excerpts and image courtesy of UC San Diego