Single-switch single-inductor equalization charger using a voltage multiplier for series-connected energy storage modules

Series-connected energy storage modules such as supercapacitors (SCs) and lithium-ion batteries cause module voltage imbalances that lead to premature deterioration of modules. Various equalization techniques have been proposed for series-connected energy storage cells/modules to alleviate such voltage imbalances. However, since the conventional topologies consist of numerous switches, sensors, inductors, or transformers, their circuit size, complexity, and costs are prone to increase in proportion to the number of series connections. This paper proposes a single-switch single-inductor equalization charger using a voltage multiplier. Because the proposed equalization charger requires only a single switch and a single inductor to operate, the circuit size and complexity can be dramatically reduced compared to that of conventional topologies. An experimental charge test was performed for series-connected SC modules with the proposed equalization charger to demonstrate its performance. Initially imbalanced voltages of the SC modules were equalized and charged to a uniform voltage level by the proposed equalization charger.