Wireless Battery Charger with Reverse Power Flow Blocking and Cell Over-Voltage Protection

This paper focuses on a wireless charger for small autonomous aerial vehicles, where lightweight construction and high power density are essential for maximizing flight time. These requirements favor the use of an active rectifier which introduces the possibility of reverse power flow. This issue becomes particularly significant during constant-voltage (CV) charging, as the low charging current increases the likelihood of power reversal. In unidirectional systems, such as solar PV-fed chargers, reverse power flow must be prevented to avoid overcharging and potential damage to the input capacitor. To address this issue, a cascaded constant-current (CC)–constant-voltage (CV) control loop is developed. The charger is designed for a 6S LiPo battery pack without individual cell balancing circuits. To enhance protection, the proposed control scheme incorporates a modified voltage loop to prevent cell overcharging. The implementation of sensing, monitoring, and control mechanisms is presented in detail with relevant simulation and experimental results for a 200 W wireless charger prototype.