Position-independent wireless power transfer system delivering constant power

摘要

A single-stage wireless power transfer (WPT) system based on the switching control capacitor (SCC) is proposed in this paper. Using the SCC instead of an ordinary capacitor gives the WPT system, an additional control degree of freedom. The proposed robust WPT system has a constant power (CP) output characteristic under a wide range of load resistance and coupling coefficient variations by adjusting the conduction angle of the SCC. When compared with constant current (CC) charging, CP charging can shorten the charging time and promote battery cycle life. Moreover, a primary side control method is proposed. It only needs to sample the primary current to identify the reflected impedance, which avoids wireless communication. When combined with the control strategy, the condition of zero-voltage switching (ZVS) is derived. Finally, a 125-W experimental prototype is built to verify the performance of the proposed method. Experimental results demonstrate that stable CP charging can be maintained during coil movement and load changes. In addition, soft switching is implemented in all situations.

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