Wireless Charging
The Electronics and Telecommunications Research Institute (ETRI) announced on Dec. 10 that it developed a key technology for a 60-watt wireless charging system utilizing magnetic resonance and succeeded in putting it to commercial use on an electric bicycle.
ETRI’s new development is characterized by creating a wireless charging zone in a space so that smart devices can be automatically changed there. Specifically, it installed two kiosk-shaped transmitters one meter apart from each other and produced a quiet zone with a uniform energy density and a frequency bandwidth of 1.78 MHz. The space between the kiosks could then be used to wirelessly charge the bicycle.
The bicycle has a built-in resonant coil for energy reception in its front wheel disk. The electricity supplied to the bicycle is collected by a collection circuit, sent to the receiver and charger, and then converted into a DC signal to charge the battery. At present, this type of charging is available on the X axis alone. However, complete wireless charging using space instead of charging pads is expected to be possible once simultaneous charging in the Y and Z planes are made possible.
The magnetic resonance-based wireless charging developed at this time is about 58 percent of cable charging in terms of charging efficiency, whereas the pad- and magnetic induction-based technique has an efficiency level of about 80 percent. According to ETRI, the former can be commercialized once reaching 70 percent.
The battery of the bicycle can be fully charged in six hours when using a cable, but magnetic resonance takes 10 hours. ETRI is planning to halve the latter through follow-up research while dealing with the environmental impact of magnetic waves by ensuring the stability of the transmission and reception system.