上海科技大学知识管理系统

Wireless faster chargers have been well developed by the various manufacturers (like Xiaomi, Huawei, and Oppo) in the past years. Considering the comparability, the standard Qi-based coils are usually used and will naturally suffer from the misalignment issue. The high-efficiency power transfer can only happen under good alignment. Even a small coil misalignment causes variation in self and mutual inductance, resulting in the drop of output power and transfer efficiency. Instead of customizing a specific transmitter, this paper provides a simple charging area extension method to fully utilize the capability of existing Qi coil, such that the system compatibility can be maintained. The proposed transmitter can still support the charging of Qi-standard based devices, and a replay coil is added outside the small Qi-coil to extend the charging area. Through the circuit-model analysis, this paper explore the power transfer and efficiency characteristics when the replay coil is activated. In the experiment, it shows the proposed charger delivers 50-W power under the standard voltage and current limitation, while the lateral offset between the transmitting coil and receiving coil is 30 mm. © 2021 IEEE.