PCB implementation of a lithium-ion capacitor charge-discharge protection circuit.

Abstract

Most of the work on LICs addresses their functionality in terms of reliability regarding energy storage and supply but seldom has the issue of their protection from damage when in use been tackled. The use of software routines through microcontroller monitoring has been the norm in protecting LICs when in use. However, it has proved to have a drawback due to the possible faults associated with software. An analog charge protection circuit was proposed but never implemented (Joan and Liven, 2018). This project henceforth sought to implement a physical charge-discharge protection analog circuit for a single lithium ion capacitor (LIC) on a minimum footprint Printed Circuit Board (PCB). Our analysis of the design by Joan and Liven revealed that the circuit could be enhanced to achieve better functionality. After simulation, a new design was proposed, in which an LM358 comparator and Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) were the key components. This circuit was prototyped and tested and the results indicate accuracy at certain states of charge. Furthermore, a PCB was designed and a quotation for fabrication attained. This work concluded that an analog plug and play device can be accurately implemented and used to protect LICs from being damaged due to charging or discharging them beyond their voltage limits.