Low cost battery equalizer using buck-boost and series LC converter with synchronous phase-shift control

This paper presents a buck-boost and series LC converter (BBSLCC) with synchronous phase-shift control (SPSC) for series battery equalizer. Traditionally, to equalize n series battery cells, buck-boost converter uses 2n-1 switches, but this BBSLCC can reduce half switch count. Closed-loop phase-shift controller based on a feed-forward method is extremely hard to implemented, but this proposed SPSC method is much easier to be achieved by just sensing the zero current through series LC circuit. A theoretical analysis shows that it take much shorter time to equalize batteries using this BBSLCC with SPSC compared with a single BBSLCC without SPSC. It also offers a solution to bypass the open circuit faulty cell. The simulation and experimental results verify the operating characteristics of this proposed topology and method, and show that it features straightforward and low cost implementation.