Search

In inductive power transfer systems, impedance matching is critical in obtaining high efficiency. However, since the load impedance is subject to variations in most applications, especially wireless charging, maintaining impedance matching is a challenge. One valid solution is to maintain the equivalent load impedance at the optimal value against load variations by controlling a load-side power converter. Nonetheless, the system overall cost, size, and complexity can be increased. In this article, based on a proper selection between full-bridge and half-bridge modes of the inverter and rectifier, an operation mode selection method is proposed that can achieve semi-impedance-matching with large load variations. In general, with the proposed method, high overall efficiency can be obtained while neither additional power converters nor complicated control is required. A 1-kW prototype has been developed and the experimental results have verified the proposed method. [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]