High misalignment tolerance is vital in the application of wireless power transfer (WPT) system. In this article, a self-oscillation WPT system with high misalignment tolerance is presented. Under the condition that the compensation equation is satisfied and the input impedance is pure resistance, the output of the S/PS topology WPT system is independent of the coupling coefficient. This article adopts the self-oscillation control method to ensure that the input impedance is pure resistance, so that the fluctuation of the system output is small with the change of the coupling coefficient. Moreover, a parametric design method that can satisfy the design requirements of transmission distance, misalignment, and output voltage is proposed. To deduce the analytical solution of the proposed WPT system, an equivalent coupled-mode method is presented in this article. Finally, the experimental results indicate that when the distance is 20.0 cm and the misalignment is less than 14.9 cm, the output voltage and efficiency of the system remain almost unchanged.

The characteristic of constant-current output (CCO) and constant-voltage output (CVO) on full bridge topology can be realized by using traditional double-sided LCC compensation network. The switching from CCO mode to CVO mode can be realized by switching the operating frequency in CCO mode (fCC) to the operating frequency in CVO mode (fCV). However, the operating frequency is generally high, the value of LP, LS and M in loosely coupled transformer will have a significant influence on the operating frequency of circuit, which makes it difficult to carry out a long-distance transmission at a lower operating frequency, otherwise the self-inductance of the coils will be high, even though it is used to transfer low-power. Therefore, in this paper, a novel P-CLCL compensation topology based on single-switching circuit (SSC) is proposed to address these problems. The switching from CCO to CVO can also be realized by changing the operating frequency from fCC to fCV, and a relatively lower operating frequency, a relatively farther transmission distance than full-bridge topology are realized. The calculation method of circuit parameters, implementation of zero-voltage-switching (ZVS), sensitivity analysis, and load-independent output are discussed. Finally, the simulation, experiment are carried out to verify the correctness of the analysis.

The full-bridge can further improve the output power through parallel inverters. The inverter output voltage of single-switch LC -resonant circuit is a combination of trapezoidal wave and half-sine wave; there is no relevant research on parallel connection of single-switch LC -resonant circuit. Therefore, this article presents a novel input-parallel single-switch LC -resonant circuit; this topology adopts switchable secondary networks for constant-current (CC) and constant-voltage (CV) output, and prevents shoot-through of power switches. The decoupling between transmitters simplifies the analysis and calculation. The input-parallel structure avoids the unbalanced input voltage of each inverter and improves the stability of the wireless power transfer system. CC and CV output modes can be achieved by controlling one relay without adding dc–dc converters or changing the switching frequency. This article includes decoupling equivalent analysis of coils, topologies analysis of CC mode and CV mode, calculation of equivalent input ac voltage source, design of magnetic coupler, and circuit parameters. Finally, a 1-kW experimental prototype is built to verify the theoretical analysis; the maximum efficiency can reach up to 92.5%.

At present, single-stage wireless power transfer (WPT) resonant converter with boost bridgeless power-factor-correction (PFC) rectifier has not been promoted due to the rising voltage of dc-link and unstable output voltage of the converter. The compensation network with load-independent constant current output (CCO) and constant voltage output (CVO) characteristics cannot be analyzed in this converter due to the above problems. In order to solve these problems, a new asymmetric modulation method and the corresponding compensation network design method for single-stage WPT converter are proposed in this article. The proposed modulation method makes the voltage of dc link and the output voltage of single-stage WPT converter constant. Based on the new modulation method, the design method of the compensation network and the implementation of zero-voltage switching (ZVS) in single-stage WPT converter are proposed and analyzed in this article. Compared with the other WPT converters, the proposed scheme has advantages in efficiency and cost. Finally, the superiorities of the proposed circuit are verified by experiments.

Miniaturization and low cost contribute to the development and popularization of wireless power transfer (WPT). Reducing the number of power conversion stages can reduce the volume and cost of the WPT converter, and even make it possible to improve the efficiency. A single-stage WPT converter with constant current (CC) and constant voltage (CV) output and its asymmetric modulation method are proposed in this paper. A direct AC-AC converter is applied to the primary side of the WPT converter to directly convert line-frequency AC to high-frequency AC. The applied direct AC-AC converter that can replace the commonly used multi-stage primary converter reduces the number of circuit devices, thereby reducing the volume and cost of primary converter. The proposed WPT converter can realize zero voltage switching (ZVS) and power factor correction (PFC). In order to achieve CC and CV output, a switchable hybrid compensation topology is applied to the proposed WPT converter. A 720-W experimental prototype was manufactured to verify the rationality of the proposed WPT converter and the correctness of the theoretical analysis.

In order to improve the restraint ability of electromagnetic energy in space and improve the coupling efficiency, a magnetic coupler structure with composite magnetic shield is proposed. Firstly, the model is established by using the finite-element simulation software. Then, according to the limit of public exposure to time-varying electromagnetic fields pointed out in ICNIPR (International Commission on Non-Ionizing Radiation Protection) guidelines, the characteristics and spatial magnetic field distribution of magnetic couplers with a single shielding structure, double shielding structure, and composite shielding structure are compared and analyzed. Finally, the experimental results show that the structure of magnetic couplers with a composite magnetic shield has a good effect in strengthening magnetic field concentration and reducing the electromagnetic interference of wireless charging systems to the external environment. It also has the advantages of smaller volume, lighter weight, and lower cost, and can effectively improve the transmission efficiency and enhance the stability of wireless charging systems.