William Plumb

Wireless Power Systems for Mobile Devices Supporting Inductive and Resonant Operating Modes

We demonstrate a family of wireless power devices that operate in a variety of operating modes. A multimode wireless power receiver unit (PRU) allows a mobile device to charge from any one of three wireless power standards: Qi, Power Matters Alliance, or Rezence. A coil arrangement and matching network is introduced that is resonant in both 6.78-MHz and 100-kHz bands, allowing the same power conversion circuitry to operate in either mode. The multi-mode PRU converts 5 W of ac power to a regulated 5-V output with an efficiency of up to 83% in Rezence mode and up to 86% in Qi mode. A wireless charging power transfer unit (PTU) using the Rezence specification charges three such PRUs at a power level of 5 W each with a power transfer efficiency of 66%. An in-band communications protocol provides enhanced capabilities to the Rezence system. Multiple layers of encoding ensure reliable delivery of messages under difficult channel conditions. Another PTU design allows the same receiver to charge through a table of 30-mm thickness while maintaining the in-band communications link. We show that a wide variety of multimode devices are possible, enabling widespread adoption of wireless power even in the absence of a single unified standard.

A 3D resonant wireless charger for a wearable device and a mobile phone

A resonant wireless power transfer (WPT) system that allows for free positioning of a wearable device about a 360° 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%.