Implantable Stimulator Charging Coil Duty Cycle for Heat Control
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Solution Overview
Problem
Neurostimulation system charging devices often operate non-optimally and pose safety risks due to excessive heat generation, which can be hazardous for patients, necessitating effective heat regulation methods to ensure safety and efficacy.
Innovation Solution
A neural-stimulation system with an external charging device that employs duty cycle modulation and net thermal energy tracking to control heat generation, without the need for thermal sensors, by monitoring and adjusting the power drawn from the battery to maintain heat levels within safe operational limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charging device operates at high power to charge the implantable pulse generator quickly, then charging speed is improved, but heat generation increases causing safety risks
Solution Approach 1:
The charging device implements periodic action by using duty cycle modulation to switch the charging coil on and off in controlled cycles. This allows the system to deliver high power when needed while incorporating off-periods that allow heat dissipation, thereby maintaining safe operating temperatures while achieving effective charging of the implantable pulse generator.
Solution Approach 2:
The system applies dynamics by continuously monitoring temperature and dynamically adjusting the duty cycle in real-time. When temperature increases, the duty cycle is reduced to lower power delivery and heat generation; when temperature decreases, the duty cycle can be increased to improve charging speed. This dynamic adaptation resolves the contradiction between charging speed and heat control.
2Reliability
If thermal sensors are added to monitor and control heat generation, then safety is improved, but device complexity increases
Solution Approach 1:
The charging device performs self-service by using its existing temperature sensor and controller to monitor its own operating temperature and automatically adjust its duty cycle accordingly. This self-regulation mechanism enables the system to maintain safe operating temperatures without requiring additional external monitoring equipment or complex control systems, thereby improving safety while minimizing added complexity.
Solution Approach 2:
The system implements feedback by continuously monitoring temperature through the existing sensor and using this information to adjust the duty cycle control. The controller receives temperature feedback and automatically modulates the charging power to maintain safe operating conditions. This feedback mechanism provides reliable safety control using the existing sensor infrastructure rather than requiring additional complex thermal management systems.
3Temperature
If the duty cycle is reduced to limit heat generation, then heat control is improved, but charging efficiency decreases
Solution Approach 1:
The system resolves this contradiction through dynamic adjustment of the duty cycle based on real-time temperature monitoring. When the charging device or implantable pulse generator temperature is low, the duty cycle is increased to maximize charging efficiency. When temperature approaches safety thresholds, the duty cycle is dynamically reduced to control heat generation. This dynamic modulation allows the system to optimize both heat control and charging efficiency throughout the charging process.
Solution Approach 2:
The periodic switching inherent in duty cycle modulation allows the system to deliver high power in controlled pulses followed by brief off-periods for heat dissipation. This periodic action enables the charging process to maintain high efficiency during the on-periods while limiting average heat generation through the cyclical nature of the modulation, thereby resolving the trade-off between heat control and charging efficiency.
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 safely charges implantable pulse generators by regulating heat generation, preventing overheating and ensuring optimal performance of the neurostimulation system, thereby enhancing patient safety and system efficacy.
Implementation Method 1
The external charging device (CD) disclosed herein may include a battery, circuitry for generating the electromagnetic field for charging the IPG
Implementation Method 2
the CD produces an amplitude of voltage or current in the coil to drive the charging process such that the IPG rectified charge voltage is maintained in its desired operating range
Data Source
AI summary
A charging device for an implantable pulse generator, the device including a charging coil and a controller. The controller being configured to track a net expended thermal energy of the charging device and modulate a charging duty cycle of the charging device to limit the heat generated by the charging device based on the net expended thermal energy. The charging device is configured to charge the implantable based on the modulated charging duty cycle by providing a voltage to the charging coil.