Class-E inverter is widely used in the wireless power transmission (WPT) system due to its high efficiency. Generally, its switching frequency should be in accordance with the resonant frequency. In a weak-coupling case, the maintenance of high transmission efficiency requires a higher resonant frequency, which would restrict its application due to the corresponding high switching frequency. To solve the issue, this article proposes a Class-E-based inverter with the phase shift control strategy, which enables the operation frequency of the inverter much lower than the resonant frequency. Besides, the transmitting coil accepts power injection twice during each period, which greatly enhances emission intensity. In addition, the proposed phase shift control strategy avoids the weakness of an extremely low duty cycle. Hence, it contributes to the MHz middle power WPT system. Then, simulations and experiments are implemented to verify that the WPT system with the proposed inverter maintains a high efficiency within the middle range and realizes nearly 50% transmission efficiency even in a very weak-coupling coefficient ( k=0.08k=0.08 ). Finally, it is proved that the proposed converter and its control strategy are available.

中文翻译：

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一种适用于 MHz WPT 系统的降低开关频率的双脉冲能量注入转换器


E类逆变器因其高效率而广泛应用于无线电力传输（WPT）系统。一般来说，其开关频率应与谐振频率一致。在弱耦合情况下，维持高传输效率需要更高的谐振频率，这会由于相应的高开关频率而限制其应用。为了解决这个问题，本文提出了一种采用相移控制策略的E类逆变器，使得逆变器的工作频率远低于谐振频率。此外，发射线圈每个周期接受两次功率注入，大大增强了发射强度。此外，所提出的相移控制策略避免了占空比极低的弱点。因此，它有助于MHz中等功率WPT系统。然后，通过仿真和实验验证，采用所提出的逆变器的WPT系统即使在非常弱的耦合系数（k=0.08k=0.08）下也能保持中等范围内的高效率并实现接近50%的传输效率。最后证明了所提出的变换器及其控制策略的有效性。