Single-Switch Cell Voltage Equalizer Using Voltage Multipliers for Series-Connected Supercapacitors

A novel single-switch cell voltage equalizer using voltage multipliers for series-connected supercapacitors (SCs) is proposed. Since the proposed equalizer can operate with a single switch at a fixed duty cycle when operated in discontinuous conduction mode (DCM), the circuit complexity can be reduced significantly when compared with conventional equalizers, and can also eliminate feedback control. Operation analyses are made and a dc equivalent circuit is mathematically derived to prove the voltage equalization mechanism. An experimental equalization test using the proposed equalizer operating with a fixed duty cycle was performed for series-connected SCs from an initially cell-voltage-imbalanced condition. The cell voltage imbalance was successfully eliminated with an average power conversion efficiency of 78.8%.