Design of an Active Equalization System for Lithium-ion Battery Based on Coreless Planar Transformer

In view of the problems caused by the inconsistency of the battery cells in the battery pack, considering the advantages and disadvantages of active equalization and passive equalization, a DC/DC active equalization scheme based on coreless planar transformer is proposed. The method of design and optimization of planar transformer is proposed. The DC/DC equalization scheme using phase-shifted full-bridge soft-switching DC/DC converter circuit is designed. The test was carried out with twelve single lithium-ion battery cells connected in series. The research showed that the overall efficiency is over 91% at 2A output current, and the highest efficiency is 93.5%. Compared with the traditional transformer, the power density is increased by 5.25 times and the volumetric specific power is increased by 5.93 times.