Analysis and Design of Soft-Switching Active-Clamping Half-Bridge Boost Inverter for Inductive Wireless Charging Applications

This paper presents an accurate analysis and a design methodology for a fixed-frequency-controlled active-clamping half-bridge boost inverter (HBBI)-based series-series compensated inductive power transfer (SS-IPT) charging system. First, the operation principles of the active-clamping HBBI in the charging system are analyzed. Consequently, both the steady-state model and the small-signal model are correctly derived by using the extended describing function (EDF) method and are used to design the system. The derived steady-state model is employed to develop a new design approach to achieve zero-voltage switching (ZVS) for the inverter. The dynamic behavior of the system is investigated, and a digital controller for charging current regulation is designed based on the derived small-signal model. The proposed methodology enables not only reducing switching losses but also avoiding bifurcation. Finally, a 1-kW laboratory prototype is implemented to verify the accuracy of the theoretical analyses. Simulation and experimental results demonstrate that the control method can effectively regulate the charging current with a fast response and no steady-state errors and can enable the inverter to achieve ZVS over a wide variation of the charging current and the battery voltage. The hardware prototype achieves a peak dc-to-dc efficiency of 93.4% at a 170-mm air gap, which is comparable to other IPT systems at similar power levels in the literature.