A Constant-Power and Optimal-Transfer-Efficiency Wireless Inductive Power Transfer Converter for Battery Charger

To improve the battery-charging rate while alleviating its aging problem, it is important to vitalize constant power (CP) charging with respect to the traditional constant current charging. Herein, a single-stage inductive-power-transfer converter is proposed for both wireless CP charging and optimal transfer efficiency. Specifically, this system adopts an inductor–capacitor–capacitor-series (
LCC
-S) compensation topology and a semiactive rectifier (SAR) at the receiver side without involving any dc–dc converter(s) or switch-controlled capacitor circuits. The load-independent transfer characteristic and system parameter design freedom are introduced by the
LCC
-S compensation topology while the conditions of soft switching are analyzed. On this basis, a novel control strategy using communication-free pulse–density-modulation-based SAR regulation is identified and implemented such that it directly regulates the output to comply with the CP charging profile and modulates the optimal equivalent load throughout the charging process. However, a 230-W experimental platform is built to verify the performance of the proposed system, and then, experimental results demonstrate a CP output with a maximum efficiency of 89.8%, and also, the efficiency can be maintained at the optimal level throughout the charging profile. Furthermore, the efficiency remains at 88.6% even at 16% dislocation.