Cell balancing control of single switch flyback converter using generalized filters

This paper presents cell balancing method of single switch flyback converter with multi-winding. In the conventional converter, voltages of each secondary winding might be unequal due to the different effective turn-ratios in multi-winding. The unequal secondary voltages make the cell voltage unbalance. Individual cell control by adding a switch for each cell can reduce the undesired effect, but the circuit becomes bulky and causes additional loss. Proposed method adds a generalized filter for each cell instead of a switch to control the unbalance. With the filters and the switching frequency selection, the magnitude of voltage applied to a particular cell can be reduced or increased. By applying the proposed method, unbalanced voltages by the effective turn-ratios are corrected and balanced voltage without any additional switch at secondary side. The experimental results verify the performance of the proposed method.