Investigations on Active Balancing Circuits for Supercapacitor Banks

Abstract

The present paper continues our investigations in the field of Supercapacitors or Electrochemical Double Layer Capacitors, briefly named EDLCs. The series connection of EDLCs is usual in order to obtain higher voltage levels. The inherent uneven state of charge (SOC) and manufacturing dispersions determine during charging at constant current that one of the capacitors reaches first the rated voltage levels and could, by further charging, be damaged. The balancing circuit with resistors and transistors used to bypass the charging current can be improved using the proposed circuit. We present here a complex variant, based on integrated circuit acting similar to a microcontroller. The circuit is adapted from the circuits investigated in the last 7-8 years for the batteries, especially for Lithium-ion type. The test board built around the circuit is performant, energy efficient and can be further improved to ensure the balancing control for larger capacitances.