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Due to the convenience and electrostatic discharge (ESD)-free features, wireless power transfer (WPT) technology has become essential for mobile devices. Conventional WPT solutions use symmetrical inductive couplers with complex structures to enhance misalignment tolerance, while using a large transmitter (TX) coil with a small receiver (RX) coil can increase distance but results in lower power density. On the contrary, we employ in this paper small TX coil and large RX coil for a better tradeoff between power transfer efficiency (PTE), output power and robustness. With detailed analyses, we prove that the small TX large RX configuration outperforms the conventional large TX coil and small RX coil solution and derives the necessary conditions with design procedures for achieving optimal PTE and desired output power. An experimental setup is built to validate the analyses, revealing that the small TX large RX configuration achieves better PTE under the higher output power conditions. Specifically, the system with small TX large RX configuration attains a PTE of 98.7% at an output of 31.29W with an airgap of 10mm.
Fang et al. (Wed,) studied this question.