Monolithic EDLC (“supercapacitor”) cell balancing IC

January 30, 2015 // By Graham Prophet
From Rohm Semiconductor, a cell balancing IC contributes to increased miniaturisation, greater stability, and longer life for EDLCs (electric double layer capacitors), which are driving the adoption of energy regeneration applications in industrial equipment, automotive idling stop systems, and voltage sag (instantaneous voltage drop) countermeasures.

The availability of this chip will, the company says, assist expansion of the EDLC energy regeneration market for automotive and industrial applications. BD14000EFV-C integrates over 20 discrete components required for EDLC cell balancing on a single chip, reducing mounting area by 38% over conventional solutions while eliminating component variations, simplifying configuration of compact, high reliability EDLC systems.

In addition to cell balancing functionality for up to six cells, multiple ICs can be connected in series to enable simultaneous control of even more cells. The cell balancing voltage can be set between 2.4V and 3.1V, ensuring support for a variety of EDLCs. Flag output is also built in, along with an over-current detection voltage function with adjustable detection voltage setting based on the cell balancing voltage. AEC-Q100 qualification aids use in automotive and other environments requiring high reliability.

When connecting multiple EDLCs in series to support higher voltages, the voltage applied to each EDLC cell may vary, which can adversely affect the lifetime and shorten the amount of time they can be safely used. Cell balancing has previousy been achieved through discrete configurations, making it necessary to address a number of issues such as board space and design load in order to minimise fluctuations while maintaining reliable cell balancing operation.

Rohm, in cooperation with Nippon Chemi-Con Corp., active in the development of EDLCs and aluminium electrolytic capacitors, has developed the EDLC cell balancing IC that provides high performance operation and integrates multiple protection functions.

Detection is enabled for 4-6 cells, and the shunt resistor method is used to achieve simple cell balancing operation, making self-contained operation possible and reducing design load considerably. In addition, the cell balancing voltage can be adjusted (2.4-3.1V, 0.1V increments) to ensure compatibility with a wide range of EDLC output voltages.

The EDLC market itself is trending towards higher voltages and capacitances, and the practice of connecting large-capacitance EDLCs in series to generate higher voltages is increasing.