An Active Approach for Charge Balancing in Functional Electrical Stimulation

Charge balancing is a major concern in functional electrical stimulation, since any excess charge accumulation over time leads to electrolysis with electrode dissolution and tissue destruction. This paper presents a new active approach for charge balancing using long-term offset regulation. Therefore, the electrode voltage is briefly monitored after each stimulation cycle and checked if it remains within a predefined voltage range. If not, an offset current is adjusted in order to track the biphasic current mismatch in upcoming stimulations. This technique is compared to a previously introduced active charge balancer as well as commonly used passive balancing techniques. Subsequently, the techniques are verified through experiments on a platinum black electrode in 0.9% saline solution.