Design and Implementation of a Dual-Mode Supercapacitor Fast Charger Employing Continuous and Fine-Tuned Pulse Currents

As an energy storage technology, supercapacitors feature a high power density. In particular, supercapacitors can be charged or discharged by a relatively large pulse current for a limited period of time. This paper takes advantage of this characteristic and develops a dual-mode fast charger for supercapacitors that employs both continuous and fine-tuned pulse currents. Based on the conventional forward converter, the proposed charger introduces an energy storage capacitor and a branch resistor to tune the rising and falling edges of the pulse current, respectively. Consequently, the transitions between the continuous and pulse current modes are significantly accelerated, which ultimately shortens the supercapacitor charging time. A prototype is built and tested using a 3 V/6 F supercapacitor. To charge the supercapacitor from 2 to 2.5 V, the proposed charger takes 0.87 and 1 s when it is configured to operate in the dual-mode and the continuous current mode only, respectively, which leads to a 13% reduction in the charging time. Moreover, compared to the forward converter, the pulse characteristics of the proposed charger are significantly improved in that the pulse rising and falling times are dramatically reduced: 2.1 versus 147 μs and 7.2 versus 103 μs, respectively.