Neural Stimulator Feedback Voltage Control for Battery Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spinal cord stimulation devices face inefficiencies in power usage, leading to frequent battery recharging and reduced battery life due to excessive power loss in current drive systems, where the voltage supplied to the tissue is higher than needed, resulting in wasted energy.
Innovation Solution
A neural stimulus device employing a voltage converter that measures nervous responses to control the voltage applied to the electrode, eliminating the need for current control and compensating for impedance variations, thereby reducing power loss and extending battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If current drive is used with voltage pumping to VddHV exceeding maximum induced tissue voltage, then sufficient current can be delivered to tissue, but power is wasted due to voltage loss (Vloss = VddHV - Vload)
Solution Approach 1:
The patent implements dynamic voltage adjustment where the voltage pump output voltage is continuously adapted to match the actual tissue impedance and required stimulation current. Instead of using a fixed high VddHV, the system dynamically sets the output voltage to Vload + overhead, where Vload is the actual tissue voltage drop. This dynamic adjustment ensures sufficient current delivery while minimizing the voltage overhead and associated power losses in the drive transistors.
Solution Approach 2:
The patent employs feedback control where the measured nervous response from the tissue is used to adjust the voltage applied by the voltage converter. The system monitors the actual tissue response and impedance changes, then feeds this information back to the voltage pump to optimize the output voltage. This feedback mechanism ensures that the voltage is neither excessively high (wasting power) nor insufficient (failing to deliver required current), thereby resolving the contradiction between power delivery and energy efficiency.
2Device complexity
If fixed VddHV is used for current drive, then simple control is achieved, but power loss exceeds power delivered to patient when stimulation strength is low
Solution Approach 1:
The patent replaces fixed voltage control with dynamic voltage adjustment based on actual tissue requirements. The voltage pump continuously adapts its output voltage according to the measured tissue impedance and desired stimulation current. This dynamic approach prevents the scenario where fixed high voltage causes excessive power loss at low stimulation strengths, while maintaining relatively simple control architecture through automated voltage regulation.
Solution Approach 2:
The patent changes the operating voltage parameter dynamically rather than maintaining a fixed VddHV. The system adjusts the voltage pump output voltage to match the actual needs of the tissue, changing the voltage parameter in real-time based on stimulation strength requirements. This parameter adaptation ensures that power loss does not exceed power delivered to the patient across all stimulation levels.
3Loss of energy
If voltage converter controls voltage based on measured nervous response, then energy efficiency is enhanced and battery life is prolonged, but device complexity increases
Solution Approach 1:
The patent implements feedback control where the measured nervous response from the tissue is used to adjust the voltage applied by the voltage converter. The system monitors the actual tissue response and impedance changes, then feeds this information back to the voltage pump to optimize the output voltage. This feedback mechanism enhances energy efficiency by preventing excessive voltage application while the complexity is managed through integrated control circuits.
Solution Approach 2:
The patent integrates multiple functions into the voltage converter and control system. The same control circuitry that manages the voltage pump also handles the measurement of nervous response and the adjustment of stimulation parameters. This multi-functionality approach reduces overall device complexity by consolidating control functions rather than adding separate dedicated circuits for each function.
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 enhances energy efficiency, prolongs battery life, and maintains desired neural responses by directly controlling voltage based on tissue feedback, reducing the need for frequent recharging and improving patient convenience.
Implementation Method 1
a voltage converter to receive the electrical energy from the battery and to control a voltage applied to the electrode based on the measured nervous response of the tissue
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
Data Source
Figure 1~2b
Figure 3
Figure 4~5
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.