Stand-Alone Broad Frequency Range Charge-Balancing System for Neural Stimulators
Jana M. Späth (Technical University of Berlin, Fraunhofer Institute for Reliability and Microintegration IZM)
Konstantina Kolovou Kouri (TU Delft - Bio-Electronics, Fraunhofer Institute for Reliability and Microintegration IZM)
Lukas Holzapfel (Fraunhofer Institute for Reliability and Microintegration IZM, TU Delft - Bio-Electronics)
Roland Thewes (Technical University of Berlin)
Vasiliki Giagka (TU Delft - Bio-Electronics, Fraunhofer Institute for Reliability and Microintegration IZM)
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Abstract
Safety is a critical consideration when designing an electrical neural stimulator, given the direct contact with neural tissue. This paper presents the design of a charge balancing system suitable for frequencies up to the kilohertz domain, to be used as an add-on system for stimulators over a wide range of frequencies, also covering nerve conduction blocking. It operates independently of the stimulator timing by continuously sensing the offset voltage, and applying a corrective current to the electrode, using the offset compensation technique. To ensure its stand-alone capability, the system is battery-powered, and includes a safety and start-up circuit. Electrical measurements verified the functionality of the circuit, demonstrating a residual offset of only 0.7 mV for 1 V biphasic pulses at 50 kHz. When tested for 20 kHz biphasic pulse at a 5 V amplitude, the offset was measured at -11.6 mV, which is still within the (commonly used) ±50 mV safety window.