Communication-Free Control Scheme for Qi-Compliant Wireless Power Transfer Systems

A conventional Qi-compliant wireless power transfer (WPT) system comprises an amplitude-shift keying (ASK) modulator and a DC regulator at the receiver side. The ASK modulator sends power demand signals back to the transmitter by means of backscatter to adjust the input power, such that the DC regulator has sufficient headroom to maintain well-regulated output voltage. Alternatively, in this paper, a communication-free control scheme is proposed for Qicompliant WPT systems without a DC regulator. The output voltage is controlled by the ASK modulator without any communication between the transmitter and the receiver. Therefore, the switched transistor bridge of the transmitter can be controlled to track the maximum energy efficiency (MEE) of the WPT system. The proposed control scheme is simple and intuitive, which can be easily implemented in low-price digital controllers.