Wireless power transfer systems with integrated impedance matching and methods for using the same

Abstract

A conventional wireless power transfer (WPT) system based on resonant inductive coupling typically operates at a peak power efficiency at the expense of a energy transfer rate. Impedance matching circuits can increase the energy transfer rate, but tend to increase the complexity, form factor, and weight of the WPT system. To overcome these limitations, a WPT system is described herein that includes a resonant circuit with integrated impedance matching. The resonant circuit includes a first coil, a first capacitor in series with the first coil, a second coil in series with the first coil and the first capacitor, and a second capacitor in parallel with the first coil and the first capacitor. The inductor coils and capacitances are tailored to increase the voltage gain and, thus, the energy transfer rate. The inductor coils also transmit or receive power, thus increasing the energy transfer rate and the power efficiency.

1 . A wireless power receiver, comprising:
 a resonant circuit to receive power from a wireless power transmitter via wireless magnetic resonance charging at a voltage gain of about 1 and an efficiency of at least 95% at a resonant frequency between about 80 kHz and about 90 kHz, the resonant circuit comprising:   a first coil;   a second coil coupled in series and concentric with the first coil and stacked on the first coil, the first coil and the second coil receiving the power from a third coil and a fourth coil in the wireless power transmitter at the resonant frequency during operation of the wireless power receiver;   a first capacitor coupled in series with the first coil; and   a second capacitor coupled in parallel with the first coil and the first capacitor,   wherein:   the first coil is magnetically coupled to the second coil;   
       the first coil and the second coil are operable to, when physically aligned with the wireless power transmitter, be magnetically coupled to the third coil and the fourth coil; and
 the first capacitor and the second capacitor do not act as an open circuit during operation of the wireless power receiver.