Neural Stimulator Voltage Control for Low-Loss Adaptive Stimulation
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Solution Overview
Problem
Existing neuromodulation systems, such as spinal cord stimulators, suffer from inefficiencies in power usage, leading to frequent battery recharging needs, as they rely on current control methods that waste significant energy due to voltage drops across current mirrors, especially when the required stimulation strength varies with patient posture or tissue impedance changes.
Innovation Solution
Implementing a voltage converter that controls the voltage applied to the electrode based on measured nervous responses, such as evoked compound action potentials (ECAPs), using digital processors and switched-mode converters to optimize energy efficiency and compensate for impedance variations, thereby reducing power dissipation in current mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If current control methods are used to deliver electrical energy to neural tissue, then the desired neural stimulation effect is achieved, but significant energy is wasted due to voltage drops across current mirrors
Solution Approach 1:
The patent changes the control parameter from current to voltage. Instead of using current mirrors to control stimulation current, the invention directly controls the voltage applied to the electrode. This parameter change eliminates the voltage drops associated with current mirrors, reducing power loss while maintaining effective neural stimulation through direct voltage application.
Solution Approach 2:
The patent extracts and removes the current mirror circuitry from the stimulation system. By eliminating the current control mechanism that causes voltage drops, the invention directly applies voltage to the electrode without the intermediate current conversion stage, thereby removing the source of energy waste.
2Reliability
If the stimulation strength is adjusted to account for patient posture or tissue impedance changes, then the neural stimulation effectiveness is maintained, but the power consumption increases
Solution Approach 1:
The patent implements a feedback mechanism where the voltage converter continuously monitors and adjusts the applied voltage based on measured nervous responses. This feedback loop maintains optimal neural stimulation effectiveness by adapting to posture and impedance changes, while the efficient voltage conversion process minimizes the additional power consumption required for these adjustments.
Solution Approach 2:
The patent introduces dynamic voltage adjustment capability through the voltage converter, which can adapt the stimulation parameters in real-time based on patient posture and tissue impedance changes. This dynamic control maintains stimulation effectiveness without the excessive power consumption associated with traditional current control methods that require similar adaptability.
3Reliability
If a higher voltage is applied to overcome tissue impedance variations, then the neural stimulation effectiveness is maintained, but the power loss in the system increases
Solution Approach 1:
The patent replaces the mechanical/current-based control system with a direct voltage control system. By substituting the current mirror mechanism with direct voltage application, the system can adjust to tissue impedance variations more efficiently, applying only the necessary voltage without the additional power losses inherent in current control architectures.
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
This approach extends battery life by minimizing power loss, allowing for longer intervals between recharges while maintaining desired neural stimulation effects, and provides adaptable stimulation strength regardless of patient posture or tissue changes.
Implementation Method 1
a voltage converter to transform the electrical energy from the battery and to control a voltage applied to the electrode
Implementation Method 2
An electrical pulse applied to the dorsal column by an electrode causes the depolarisation of neurons and generation of propagating action potentials
Implementation Method 3
a measurement circuit to measure the nervous response of the tissue
Data Source
AI summary
This disclosure relates to a device for applying a neural stimulus. A battery supplies electrical energy at a battery voltage and an electrode applies the electrical energy to neural tissue. A circuit measures the nervous response of the tissue and a voltage converter receives the electrical energy from the battery and controls a voltage applied to the electrode based on the measured nervous response of the tissue. This direct voltage control is energy efficient because losses across a typical current mirror are avoided. Further, the control based on the measured nervous response leads to automatic compensation of impedance variation due to in-growth or change in posture. As a result, the stimulation results in a desired neural response.