Qi是由无线电源联盟开发的接口标准，用于在最大4厘米（1.6英寸）的距离上进行感应式电能传输。Qi系统包括便携式设备中的动力传输板和兼容的接收器。为了使用该系统，将移动设备放置在动力传输垫的顶部，该功率垫通过共振感应耦合对其充电。

    Under the Qi specification, "low power" for inductive transfers denotes power deliveries below 5 W. Systems that fall within the scope of this standard are those that use inductive coupling between two planar coils to transfer power from the power transmitter to the power receiver. The distance between the two coils is typically 5 mm. It is possible to extend that range to at least 40 mm. Regulation of the output voltage is provided by a digital control loop where the power receiver communicates with the power transmitter and requests more or less power. Communication is unidirectional from the power receiver to the power transmitter via backscatter modulation. In backscatter modulation, the power-receiver coil is loaded, changing the current draw at the power transmitter. These current changes are monitored and demodulated into the information required for the two devices to work together.