No abstract

A resonant wireless power transfer (WPT) system that allows for free positioning of a wearable device about a 360 o axis of rotation and simultaneous charging of a mobile phone is proposed. A 3D transmitter coil structure is introduced to provide a cylindrical charging surface with a uniform magnetic field. A prototype charging system including an amplifier and a rectifier operating at 6.78 MHz is demonstrated. The prototype delivers 1 W to a wearable device and 5 W to a mobile phone simultaneously with a power transfer efficiency of 48%.

We demonstrate a compact wireless power receiver for mobile phones that operates either in a resonant mode at 6.78 MHz or an inductive mode in the 110 to 205 kHz range. A coil arrangement and matching network is introduced that is resonant in both frequency bands, allowing the same power conversion circuitry to operate in either mode. The receiver converts up to 5 W of AC power to a regulated 5 V supply with a peak efficiency of 84% in inductive mode and 82% in resonant mode.

A cup-shaped in-vehicle wireless charging system that allows free alignment for charging portable devices is proposed in this paper. A 3D transmitter coil structure is designed to provide the sufficient magnetic flux density perpendicular to each charging surface. By adding the flexible ferrite sheet surrounding the structure, the leakage of magnetic flux is eliminated to meet the electromagnetic compatibility (EMC) requirement. The whole system is designed and simulated according to the A4WP specification.