“Time Shared Flyback Converter” Based Regenerative Cell Balancing Technique for Series Connected Li-Ion Battery Strings

A cell voltage equalizer circuit for future plug-in hybrid electric vehicles (PHEV) or renewable energy storage is proposed in this paper. This topology has fewer passive components compared to the conventional topologies found in the literature, and therefore, it could reduce implementation complexity. This circuit is based on a time shared flyback converter, and any number of series connected cells in a string could be used without any apparent issues ensuring good modular architecture. Each cell in a module shares a single converter during its allocated time slot allocated by a low-power microcontroller. In addition, dynamic allocation of time slots is possible to achieve a faster cell balancing, and the circuit dynamically distributes depleted charge among the cells in a regenerative fashion. The operating principles and design procedures of the proposed topology have been presented in the paper. The prototype of a four-cell lithium-ion battery balancer circuit with the proposed topology has been constructed, and the test results have been included.