DC-link capacitor sizing method for a wireless power transfer circuit to be used in drone opportunity charging

Resonant-coupled inductive Wireless Power Transfer systems are very appealing as opportunity charging systems for droneapplications. Drones are compact systems in which weight and size are critical constraints, so the on-board electronics and the battery must be as small and light as possible. The paper presents the LTSpice simulation analysis of a circuit on the WPT secondary side that uses the intrinsic inductance of the Li-poly battery and only an external capacitor as filter of the full-wave bridge rectifier that typically constitutesthe DC-link. The analysis shows the trade-off between the power delivered to the battery and the capacitor size. It results that it can be found a capacitor value that maximizes the power transfer to the battery at the expense of a non-optimal transfer efficiency and increased ripple in the battery current. That value sets the LC-filter resonant frequency close to the double of the excitation frequency of the WPT system.