Float Zener Diode Protection Circuitry for IPG ESD and Defibrillation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing implantable pulse generators (IPGs) for neurostimulation systems are not immune to interference from MRI systems and other sources of electromagnetic interference (EMI), leading to therapy degradation and the need for specialized programming or disabling of therapy during exposure.
Innovation Solution
The implementation of improved protection circuitry in IPGs, which includes an IPG ground connection and a plurality of protection Zener diodes, along with a float Zener diode, to protect stimulation and sensing circuitry from damage during electrostatic discharge and cardiac defibrillation, and to mitigate unintended stimulation during EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional protection circuitry is used in IPGs, then the device can operate during neurostimulation therapy, but the stimulation and sensing circuitry is vulnerable to damage from electrostatic discharge and cardiac defibrillation
Solution Approach 1:
A float Zener diode is introduced as an intermediary protective element between the protection Zener diodes and IPG ground. This float Zener diode acts as a mediator that clamps voltage excursions during electrostatic discharge and cardiac defibrillation events, preventing harmful voltages from reaching the stimulation and sensing circuitry while allowing normal operation during neurostimulation therapy and MRI scans
Solution Approach 2:
The protection circuitry including multiple protection Zener diodes and a float Zener diode is pre-configured in the IPG before implantation. This beforehand cushioning provides immediate protection against electrostatic discharge and cardiac defibrillation events without requiring any action at the time of the event, ensuring the circuitry is already protected when exposed to harmful voltage excursions
2Object-affected harmful factors
If neurostimulation therapy is disabled during MRI scans, then the IPG is placed in MRI-safe mode to avoid interference, but therapy cannot be delivered when needed
Solution Approach 1:
The protection Zener diodes and float Zener diode, originally designed to protect against harmful voltage excursions, are repurposed to enable therapy delivery during MRI scans. By clamping EMI-induced voltage fluctuations on the can and leads, the protection circuitry converts the harmful EMI environment into a manageable condition that allows continuous therapy delivery without requiring MRI-safe mode
Solution Approach 2:
The protection circuitry changes the electrical parameters (voltage clamping levels) dynamically during MRI scans to maintain therapy delivery. The Zener diodes adjust their clamping action based on the EMI conditions, allowing the IPG to operate in a previously unusable EMI environment by modifying the electrical characteristics of the protection elements
3Object-affected harmful factors
If specialized bipolar stimulation programs are used during MRI scans, then therapy can be maintained, but additional programming burden is placed on clinicians and patients
Solution Approach 1:
The protection circuitry with float Zener diode and protection Zener diodes provides automatic, self-regulating protection during MRI scans and EMI events. The circuit self-adjusts by clamping voltage excursions without requiring clinician programming or patient action, eliminating the need for specialized bipolar stimulation programs and making the device automatically resistant to EMI-induced stimulation
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 improved protection circuitry effectively maintains effective and safe neurostimulation therapy during exposure to MRI and other EMI sources, reducing the need for specialized programming and ensuring consistent therapy delivery without therapy degradation.
Implementation Method 1
The protection circuitry includes an IPG ground connection, a plurality of protection Zener diodes, wherein one of the protection Zener diodes is electrically coupled between the IPG case and a float Zener diode, and wherein the remaining protection Zener diodes are electrically coupled between the plurality of electrodes and the float Zener diode, and the float Zener diode electrically coupled between the plurality of protection Zener diodes and the IPG ground
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present disclosure provides systems and methods for protection circuitry for an implantable pulse generator (IPG) of a neurostimulation system. The protection circuitry is coupled to an IPG ground, a plurality of electrodes, and an IPG case, and operable to protect IPG stimulation and sensing circuitry from damage during electrostatic discharge and cardiac defibrillation, and to mitigate unintended stimulation during electromagnetic interference. The protection circuitry includes an IPG ground connection, a plurality of protection Zener diodes, wherein one of the protection Zener diodes is electrically coupled between the IPG case and a float Zener diode, and wherein the remaining protection Zener diodes are electrically coupled between the plurality of electrodes and the float Zener diode, and the float Zener diode electrically coupled between the plurality of protection Zener diodes and the IPG ground.