Analysis of Power Losses and the Efficacy of Power Minimization Strategies in Multichannel Electrical Stimulation Systems

TL;DR

This paper introduces a methodology to analyze power losses in multichannel neurostimulation systems and demonstrates that stepped voltage scaling significantly improves efficiency in high-channel-count applications with variable tissue impedance.

Contribution

It presents a novel methodology for quantifying power losses and evaluates different supply scaling strategies, highlighting the benefits of stepped voltage scaling for high-channel-count systems.

Findings

Stepped voltage scaling improves efficiency by 67-146%.

Variability in tissue impedance reduces power efficiency.

Global scaling is better for low-channel systems.

Abstract

Neuroprosthetic devices require multichannel stimulator systems with an increasing number of channels. However, there are inherent power losses in typical multichannel stimulation circuits caused by a mismatch between the power supply voltage and the voltage required at each electrode to successfully stimulate tissue. This imposes a bottleneck towards high-channel-count devices, which is particularly severe in wirelessly-powered devices. Hence, advances in the power efficiency of stimulation systems are critical. To support these advances, this paper presents a methodology to identify and quantify power losses associated with different power supply scaling strategies in multichannel stimulation systems. The proposed methodology utilizes distributions of stimulation amplitudes and electrode impedances to calculate power losses in multichannel systems. Experimental data from previously published studies spanning various stimulation applications were analyzed to evaluate the performance of fixed, global, and stepped supply scaling methods, focusing on their impact on power dissipation and efficiency. Variability in output conditions results in low power efficiency in multichannel stimulation systems across all applications. Stepped voltage scaling demonstrated substantial efficiency improvements, achieving an increase of 67 % to 146 %, particularly in high-channel-count applications with significant variability in tissue impedance. Global scaling, by contrast, was more advantageous for systems with fewer channels. The findings highlight the importance of tailoring power management strategies to specific applications to optimize efficiency while minimizing system complexity. The proposed methodology offers a framework for evaluating efficiency-complexity trade-offs, advancing the design of scalable neurostimulation systems.