High Misalignment-Tolerant 15 W Wireless Charging System Using Parity-Time Symmetric Topology

Magnetic coupled resonant wireless power transfer (MCR-WPT) is widely adopted in consumer electronics and portable charging devices, yet conventional systems suffer from severe output power drop and efficiency degradation under large lateral coil offset, thus limiting its application in miniature charging scenarios. Targeting this issue, this paper proposes a 15 W low-power wireless charging system adopting parity-time (PT) symmetric topology to enhance misalignment tolerance. A series–series (SS)-compensated equivalent circuit is established for the PT-symmetric wireless power transfer (WPT) system. The mathematical derivation is carried out to obtain the parameter boundary conditions for maintaining PT-symmetric operation, as well as the calculation method of PT-symmetric operating frequencies. According to the technical specifications, including 3.7 mm transmission distance, ±15 mm maximum lateral offset, limited coil size, and ultra-thin receiving coil, the overall circuit parameters are optimized and designed. Prototype experiments are implemented under the maximum 15 mm offset condition and multiple offset states. The results demonstrate that the proposed PT-symmetric WPT system realizes constant voltage output and stable 15 W power delivery within the full offset range. At 15 mm lateral misalignment, the system efficiency remains 65.60%, which fully verifies the superior anti-misalignment capability and engineering practicability of the designed system.