Two-stage-cascaded Li-battery charger with current ripple considered

In this paper, a two-stage-cascaded scheme is presented to charge two Li batteries. The first stage consists of a boost converter which is used to step up the input voltage to some value and takes voltage-mode control, whereas the second stage is comprised of two paralleled buck converters which are used to charge two Li batteries under voltage-mode control and constant current control. Above all, the second stage takes interleaved control and hence the corresponding output current ripple of the boost converter is with double switching frequency and is decreased so that the life of the output capacitor of this stage is upgraded. Some experimental results, based on Cyclone II FPGA used as a control kernel, are provided to verify the proposed topology.