Analysis and Design of an LCCC/S-Compensated WPT System With Constant Output Characteristics for Battery Charging Applications

The wireless power transfer (WPT) system has been extensively studied for its safety, convenience, and esthetics and has gradually been introduced into our life applications. In order to maintain battery performance, constant-current (CC) and constant-voltage (CV) charging outputs are generally regarded as the dominant charging modes. However, battery equivalent resistance changes significantly during the charging, so it is difficult to simultaneously achieve load-independent CC and CV charging outputs and zero phase angle (ZPA) condition. This article proposes a new LCCC/S topology and its corresponding parameter tuning method to obtain CC and CV charging modes at two different ZPA operating frequency points, respectively. In addition, it is worth mentioning that the receiver has only one compensation capacitor, which follows the principle that the receiver of the WPT system should remain compact and portable. Furthermore, a simple frequency modulation controller is designed to solve the problem of inaccuracies of the charging outputs due to parasitic losses of components and fluctuations of dc input voltage. Finally, a verification setup with 3-A output current in the CC mode and 48-V output voltage in the CV mode was built to validate the feasibility and rationality of the proposed LCCC/S-compensated WPT system and the corresponding control method.