Stationary wireless power transfer has been deployed commercially and can be used to charge a variety of devices, including mobile phones and parked electric vehicles. However, wireless power transfer set-ups typically suffer from an inherent sensitivity to the relative movement of the device with respect to the power source. Nonlinear parity–time symmetric circuits could be used to deliver robust wireless power transfer even while a device is moving rapidly, but previous implementations have relied on an inefficient gain element based on an operation-amplifier circuit, which has inherent loss, and hence have exhibited poor total system efficiency. Here we show that robust and efficient wireless power transfer can be achieved by using a power-efficient switch-mode amplifier with current-sensing feedback in a parity–time symmetric circuit. In this circuit, the parity–time symmetry guarantees that the effective load impedance on the switch-mode amplifier remains constant, and hence the amplifier maintains high efficiency despite variation of the transfer distance. We experimentally demonstrate a nonlinear parity–time symmetric radiofrequency circuit that can wirelessly transfer around 10 W of power to a moving device with a nearly constant total efficiency of 92% and over a distance from 0 to 65 cm.

固定式无线电力传输已在商业上部署，可用于为各种设备充电，包括移动电话和停放的电动汽车。然而，无线电力传输设置通常遭受对设备相对于电源的相对运动的固有敏感性。非线性奇偶时间对称电路即使在设备快速移动的情况下也可以用于提供可靠的无线功率传输，但是先前的实现方式依赖于基于运算放大器电路的低效率增益元件，该元件具有固有损耗，因此表现出整体系统效率差。在这里，我们证明，通过在奇偶时间对称电路中使用具有电流感应反馈的高功率开关模式放大器，可以实现强大而有效的无线功率传输。在该电路中，奇偶时间对称性确保了开关模式放大器上的有效负载阻抗保持恒定，因此，尽管传输距离有所变化，该放大器仍保持高效率。我们通过实验证明了一个非线性奇偶时间对称射频电路，该电路可以将大约10 W的功率无线传输到移动设备，总效率几乎恒定为92％，并且传输距离为0至65 cm。