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For an inductive power transfer (IPT) system, mobility is one of the most attractive features, but coupling variations can dramatically affect the system's output. In this article, a reconfigurable rectifier-based detuned series-series (SS) compensated IPT system is proposed to tolerate an extensive coupling range and improve the system efficiency simultaneously. The reconfigurable rectifier, which can operate in a full-bridge rectifier mode or a half-bridge rectifier mode, is used to alter the equivalent ac load from one value to the other so the expected coupling range of the detuned SS topology can be extended. At the same time, the system efficiency is also partly improved because the ac load is changed to get closer to the optimal load of the IPT system. First, a detuned SS IPT system with the reconfigurable rectifier is presented and followed by the analysis of the working modes. Then, a detailed parameter design process and switching control of the reconfigurable rectifier are introduced. Finally, a 400-W prototype was constructed to verify the validity of the proposed method. The experimental results demonstrate that the output power fluctuation of the proposed IPT system is less than 17.5% and the lowest efficiency can be improved from 68.6% to 87.5% with the coupling coefficient varying from 0.1 to 0.4. The proposed method can implement significant antimisalignment and efficiency improvement simultaneously, and it is regarded as a potential solution for low-power IPT applications with high spatial mobility. [ABSTRACT FROM AUTHOR]

To increase the power density of a wireless power transfer (WPT) system, the coupling of coils can be strong. However, in a strongly coupled series–series WPT system with a diode rectifier, currents can be distorted and discontinuous, and first harmonic approximation is no longer valid. The inverter is likely to work in hard switching, leading to extra noise, decreased efficiency, and a potential hazard for a safe operation. Through time-domain analysis, this article reveals that with a dual-side 90° phase shift, the hard switching of the inverter can be avoided, the power level can be enhanced, and the discontinuous conduction mode can be avoided to eliminate noises. The factors impacting the soft switching operations of the inverter and the rectifier are analyzed. To achieve 90° dual-side phase shift, the conventional approach of using the receiver voltage/current, which can be distorted and discontinuous in strongly coupled WPT systems, for phase synchronization is no longer suitable. A new set of coils, namely driving coils, is used for phase synchronization so that dual-side phase shift can be implemented independent from power transfer. Experimental results have validated the effectiveness of the analysis. [ABSTRACT FROM AUTHOR]

Load-independent output characteristics of inductive power transfer (IPT) systems are increasingly popular in battery charging. This paper proposes a novel variable-parameter T-circuit (VT) for an IPT system charging a battery with constant current (CC) or constant voltage (CV) output. The VT can transfer a CC/CV input to a CC or CV output by using an ac switch and a passive component (inductor or capacitor). An IPT system with a VT for CC–CV charging can reduce the number of passive components and ac switches. Besides, the proposed VT merits more design freedom of charge current/voltage with the constraints imposed by the loosely coupled transformer parameters compared to that of the traditional one. In addition, there are three kinds of VTs for various IPT charging systems with different requirements. A 400 W laboratory-scale prototype with a 150 mm air gap was built to verify the theoretical analyses. Both electronic load and lead-acid battery are utilized to verify the charging profile of the proposed method. The experimental results of the IPT system indicate that the fluctuation of the charging current in CC mode is less than 2%, and the change rate of charging voltage in CV mode is within 2.9%. The maximum overall efficiency 93.93% of the charging system is achieved from a dc 110 V input to a dc 100 V output. [ABSTRACT FROM AUTHOR]