Novel control approach to achieving efficient wireless battery charging for portable electronic devices

Various resonant converter topologies have become popular in wireless power transfer applications. In particular, due to convenience and aesthetics, wireless charging has become very popular for portable electronics. In low power applications such as portable electronics charging, it is desirable to minimize the number of converter components to improve the efficiency. This paper presents a novel control method that exploits the desirable characteristics of the dual active bridge series LCLC resonant converter topology. The result is a wireless charger with several desirable features: it eliminates the need for digital communication between the transmitter and receiver, the design is robust against coupling coefficient and load variations, it operates most of the time at the highest efficiency operating point (the unity gain frequency), it uses synchronous rectification for improved efficiency, it does not require a downstream regulator for battery charging current control, and it provides a fast charging operating mode. In this paper, the series LCLC resonant network is analyzed in detail to describe the notable characteristics that are crucial in making the proposed control method effective. Throughout the analysis, various simulation results are provided to complement the discussion. Finally, the charging process employing the proposed control method is described in detail, and Simulink simulation results are presented to demonstrate the feasibility of the proposed control method.