The inherent frequency of magnetic coupling resonance based wireless power transfer system (MCR-WPT) is up to the level of kHz or even MHz. The class-E converter with zero-voltage switching (ZVS) could eliminate the considerable switching loss, however, the high voltage stress and sensitive ZVS condition to coils distance limit its application seriously in MCR-WPT. To solve the issues, a voltage-clamped class-E converter, consisting of an auxiliary clamped circuit to decrease the voltage stress and a harmonic circuit to realize ZVS against a wide range of coils position, is proposed for the WPT system. According to the harmonic analysis, the relationship among duty cycle, input voltage, amplitudes and phases of the harmonics is obtained. Then, the design strategy for system parameters, especially for the harmonic circuit is presented, so that, ZVS could be maintained over a wide range of coils distance. Meanwhile, the efficiency analysis is also carried out, suggesting a steady high efficiency further. Three design examples with disparate harmonic parameters and ZVS ranges are presented and one of the three examples is selected to make comparison with a typical Class-E WPT system. The experimental results agree with the theoretical analysis well.

中文翻译：

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WPT系统中具有宽电压范围的ZVS且电压应力降低的钳位谐波注入E类转换器

基于磁耦合共振的无线电力传输系统（MCR-WPT）的固有频率高达kHz或什至MHz。具有零电压开关（ZVS）的E类转换器可以消除可观的开关损耗，但是，高电压应力和对线圈距离敏感的ZVS条件严重限制了其在MCR-WPT中的应用。为了解决这一问题，为WPT系统提出了一种电压钳位E类转换器，该转换器由一个可降低电压应力的辅助钳位电路和一个在较大的线圈位置范围内实现ZVS的谐波电路组成。通过谐波分析，得到了占空比，输入电压，谐波幅度和相位之间的关系。然后，提出了系统参数特别是谐波电路的设计策略，从而，ZVS可以在很宽的线圈距离范围内保持。同时，还进行了效率分析，进一步表明了稳定的高效率。给出了三个具有不同谐波参数和ZVS范围的设计示例，并选择了三个示例之一与典型的E级WPT系统进行比较。实验结果与理论分析吻合良好。