Increase in Power Efficiency When Discharging Series Capacitors with a Step-Down Circuit Compared to Discharging Parallel Capacitors with a Step-Up Circuit

Abstract

A discharging circuit with high energy efficiency is designed for supercapacitors. In this design, the capacitors are connected in parallel during charging and connected in series during discharging. With this method, the voltage of the capacitors in series becomes two times larger during discharging; thus, the step-down circuit can be used to produce the desired output voltage. The efficiency of the step-down circuit is four times larger than that of the step-up circuit in simulations. The experimental results agree well with the theoretical values. These results show that a step-down circuit is superior to a step-up circuit for extracting electrical energy from supercapacitors.