Simultaneously tuning and powering multiple wirelessly powered devices

Wireless charging standards for consumer devices include specifications for charging multiple receive devices simultaneously. However if the devices are not all the same size or if they require different amounts of power, these existing standards may be incapable of charging multiple devices efficiently. This paper provides an overview of a complete wireless power transfer system that is capable of automatically tuning, communicating with, and efficiently powering multiple single-cell battery charging receive devices. Frequency tracking, power tracking, and adaptive impedance matching are used to dynamically tune each receiver and the transmitted signal for optimal power delivery to each receiver. Additionally, these same tuning techniques are used to demonstrate time-division multiplexing, where individual receive devices are powered sequentially while all other receive devices are de-tuned and do not consume any power, even in the presence of the transmit coil.