A low cost battery equalizing scheme with buck-boost and series LC converter using synchronous phase-shift controller

Abstract

This paper presents a modularized buck-boost and series LC converter (BBSLCC) circuit for series battery equalizers. The proposed topology has numerous advantages. First, the number of switches in the equalizer is equal to the number of the battery cells needs to be balanced in the string. This is so called one-switch-per-cell, which is a great advantage over the traditional buck-boost converter, since it requires almost two-switch-per-cell to balance. Second, unlike many other existing one-switch-per-cell equalizers, the proposed circuit has the advantage in the modularization design and low voltage stress requirement on the switches. Third, the peak current of the balancing capacitor are suppressed by the synchronous phase-shift controller (SPSC) which can be easily implemented by sensing the zero crossing of the LC resonant current. By using the proposed controller, the speed of the battery equalizing process is also accelerated. In this paper, the proposed topology is first presented, and the operating principle is illustrated. Afterwards, the phase-shift time and the transferred energy of the BBSLCC circuit are calculated to demonstrate the proposed control strategy details. The relationships between the phase-shift time and other circuit parameters such as the inductance and the capacitance are also analyzed. The simulation results and the experimental results are finally demonstrated and verified the theoretical analysis on the performance of the proposed BBSLCC circuit.