Wireless power transfer based on current non‐linear PT‐symmetry principle

Abstract

In this study, the authors propose a novel circuit topology based on the current non-linear parity-time (PT)-symmetry principle. The exact analytical solutions of transfer efficiency and resonant frequency are deduced, a state switching phenomenon is observed, and the mathematical expression of the critical coupling coefficient (κ c) corresponding to the state switching point is provided. When the coupling coefficient (κ) is ≥κ c , the system has two real frequencies and can maintain near 100% transfer efficiency theoretically. When κ < κ c , the system has only one real frequency, and the transfer efficiency attenuates rapidly. The correctness of the theoretical model is verified by simulation and experiment. Results show that when the distance between the two coils (38 cm in diameter) varies from 10 to 42.5 cm, the transfer efficiency remains ∼95%, without the need for any tuning. Theoretical analysis and experimental verification show that κ c increases when the load resistance increases and the natural resonant frequency or the self-inductance of the Rx coil decreases. Furthermore, the system can maintain the equivalent current of the Tx and Rx circuits when κ ≥ κ c , which is convenient for controlling the circuit current, and suitable for the case of small load and large current.

Transmission range extension strategy of parity–time‐symmetry‐based wireless power transfer system by a boost converter

“…In fact, the value of R L þr 2 ω 0 L 2 is small. Ignoring the high order term in (13), k c can be described as…”

“…of the WPT system are listed in Table 1. According to (12), (13), and Table 1, the dynamic curves of critical coupling coefficient, output power, and efficiency with the change of R 0 L can be drawn as Figure 5.…”

“…4. Compared with the methods in other studies, [11][12][13] the proposed system does not require larger coils, making it more suitable for cases with small coils, such as mobile phones and biomedical implants. As for the method in Wei and Zhang, 14 although these two methods both cause a decline in efficiency, the method in this article is more suitable for the case with large resistance.…”

“…Yet too large coils and additional shielding structures will reduce availability. Dong et al 13 increased the inductance of the receiving coil to reduce the critical coupling coefficient will enlarge the receiving coil so that the system loses some convenience. Wei and Zhang 14 improves the problem above by adding an inductor, which is not coupled with the transmitting, to the secondary side.…”

“… For a certain object, its resistance is determined. Adding a boost converter to change equivalent resistance can improve the performance of transmission distance. The drive signal for the converter can be selected according to the system requirements, providing more design flexibility. The drive signals in transmitting circuit and receiving circuit can both be generated and controlled by themselves in practical applications, not any communication device is required. Compared with the methods in other studies, 11–13 the proposed system does not require larger coils, making it more suitable for cases with small coils, such as mobile phones and biomedical implants. As for the method in Wei and Zhang, 14 although these two methods both cause a decline in efficiency, the method in this article is more suitable for the case with large resistance. …”