An Anti-Offset CPT System With Multiple Pickups for Mobile Desktop Application

Capacitive power transfer (CPT) system takes advantages of being able to transfer power across metal with low power losses, so it is potential for mobile desktop applications such as mobile phones, tablet PCs, laptops, etc. Compared with single transmitter and single pickup (STSP) CPT systems, single transmitter and multiple pickup (STMP) CPT systems are more competitive in cost and convenience. However, a big challenge in existing multipickup CPT is the outputs vary greatly when the transmitter and the pickup are not aligned. This article proposes an interdigital electrode capacitive coupler to realize antioffset performance of multiple pickups. Then, for ease of analysis, an STMP to STSP conversion CPT model is proposed to simplify mathematical analysis. By designing double-sided LC topology, multiple pickups are regarded as a parallel branch of the compensation network on the primary side, and the STMP system is converted to a STSP system. Finally, the load-independent CC outputs of multiple pickups and the antioffset performance of the proposed CPT system are analyzed, and the zero voltage switching state can be also obtained. A prototype with single transmitter and three pickups was built, load-independent CC outputs and antioffset performance of multiple pickups have been verified. The system efficiency was up to 91.7% (28 W) in the case of three pickups.