Solar power battery charger with a parallel-load resonant converter

Although fossil fuels have led us to economic prosperity, the extensive use has caused a substantial reduction of fossil fuels. Therefore, the solar energy, as one of the green energy resources, has become an important alternative for the future. In this paper, the parallel loaded resonant converter with the feature of the soft switching technique was used in the circuits of the solar storage battery charger. To avoid the damage of the battery charger due to the variation of the output current of the solar PV panels, a closed-loop boost converter between the solar PV panel and the battery charger was designed to stabilize the output current of the solar PV panel. By designing the characteristic impedance of the resonant tank, the charging current of the storage battery can be calculated and then the charging time for the storage battery can further be estimated. By properly designing the circuit parameters, the parallel loaded resonant converter can be operated in the continuous current conduction mode and the switch can be switched for conduction at zero voltage. The experimental results verified the correctness of the theoretic estimation for the proposed battery charger circuit. The average charging efficiency of the battery charger can be up to 88.7%.