Floating Current Regulator Circuit for MRI-Stable Neurostimulation
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Solution Overview
Problem
Conventional neurostimulation systems face challenges in maintaining consistent and predictable therapy delivery in the presence of electromagnetic interference, particularly from magnetic resonance imaging scanners, leading to unpredictable voltage potentials and the need for additional programming and circuit complexity.
Innovation Solution
A neurostimulation system with a current regulator powered by a floating power supply and a floating ground node, which maintains a high impedance loop to control current flow and emulate passive discharge, using a charge pump and EMI antenna to sense and mitigate interference, allowing continuous therapy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional neurostimulation systems are used in the presence of MRI scanners, then electromagnetic interference causes unpredictable voltage potentials and therapy delivery issues, but the system requires additional programming complexity and circuit modifications to handle the interference
Solution Approach 1:
The patent implements a floating ground node that maintains equipotential conditions during EMI events by allowing the ground reference to float rather than remain fixed. This enables the system to maintain stable voltage potentials across all circuit nodes relative to each other, even when absolute potentials shift due to external electromagnetic interference from MRI scanners
Solution Approach 2:
The patent introduces a charge pump circuit as an intermediary component that actively manages voltage potential differences between the floating ground node and other circuit elements. This intermediary mechanism mediates the effects of EMI by dynamically adjusting voltage levels to maintain stable therapy delivery without requiring complex shielding or filtering circuits
2Stability of the object's composition
If the system uses a fixed ground reference during EMI events, then circuit operation becomes unstable due to voltage drift, but allowing ground to float increases programming complexity
Solution Approach 1:
The floating ground node maintains equipotential relationships within the circuit by allowing the entire circuit reference to shift together in response to EMI. This preserves stable voltage differences across all components while adapting to external interference, eliminating the need for complex programming to compensate for ground drift
Solution Approach 2:
The system automatically adapts to EMI conditions through the floating ground mechanism without requiring manual reconfiguration or complex programming. The charge pump circuit self-regulates to maintain proper voltage relationships, making the system operationally simple despite the sophisticated underlying mechanism
3Reliability
If conventional current regulators are used during EMI events, then current control becomes unpredictable due to induced voltage potentials, but implementing EMI protection increases device complexity
Solution Approach 1:
The charge pump circuit serves as an intermediary between the floating ground node and the current regulator, isolating the regulator from EMI-induced voltage fluctuations. This intermediary layer provides stable reference voltages to the regulator, ensuring predictable current control without requiring the regulator itself to be complex or EMI-resistant
Solution Approach 2:
The floating ground node maintains equipotential conditions for all regulator circuit elements, ensuring that voltage references and sensing nodes remain stable relative to each other even during EMI events. This enables the current regulator to maintain predictable control without additional complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system ensures stable neurostimulation therapy during EMI events, minimizing therapeutic side effects and simplifying programming by maintaining a desired stimulation profile and reducing circuit complexity.
Implementation Method 1
The floating power supply may include a charge pump and a switch network
Implementation Method 2
An EMI antenna may be configured to sense and mitigate interference from EMI
Data Source
AI summary
A system and method are provided that include a power supply having positive and negative terminals. The negative terminal defines a reference ground. First and second electrodes are positioned within a patient and configured to be located proximate to tissue of interest that is associated with a target region. A control circuit is configured to control delivery of current for a therapy between the first and second electrodes. A current regulator (CR) circuit is connected to, and configured to control current flow through, at least the first electrode during delivery of the therapy under direction of the control circuit. A floating power supply is connected across power supply terminals of the CR circuit. The CR circuit and floating power supply are coupled to a floating ground node that is electrically separate from the reference ground.