A universal functional electrical stimulator based on merged flyback-SC circuit

Abstract

This paper introduces novel functional electrical stimulation (FES) system architecture. Compared to the existing state of the art solutions [1]-[15], the presented FES system drastically increases variety of stimulation pulses, results in a less painful therapy and has significantly lower power consumption. Furthermore, the FES system inherently provides zero net charge of stimulated tissue eliminating the need for a dedicated discharging circuit. The key element of the FES is a novel power stage merging a flyback and switch-capacitor (SC) converters. The flyback steps up battery voltage and provides galvanic isolation. The following SC stage produces zero net charge high slew-rate pulses reducing pain sensation. The control of the output current pulses is performed through integrated digital voltage-programmed current mode control. The new FES system was tested with able bodied individuals. The results show that it produces pulses with a 10 ns rise time, which compared to other known solutions, result in the same muscle force output for 30+% less stimulation energy. The results also show that the presented FES system requires 60% less energy compared to other known systems allowing longer battery life in portable applications.