Implantable Device Charging System Frequency Tuning
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Solution Overview
Problem
Existing implantable medical devices face inefficiencies in transcutaneous energy transfer due to mismatched resonant frequencies between external and internal coils, leading to prolonged recharging times and potential patient discomfort from heat dissipation.
Innovation Solution
A system that monitors signal characteristics to determine the system resonant frequency, adjusting the drive frequency of the primary coil to match the optimal resonant frequency, using edge detection to identify 'stub pulses' and adjust the frequency accordingly, ensuring efficient energy transfer during recharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the primary coil is driven at a fixed nominal resonant frequency, then the device structure is simple, but the energy transfer efficiency deteriorates due to frequency mismatch with the secondary coil system
Solution Approach 1:
The system monitors the characteristic signal from the primary coil and uses this feedback to automatically adjust the drive frequency. The control circuit detects when the monitored signal characteristic appears (indicating frequency mismatch) and adjusts the drive frequency accordingly to maintain optimal energy transfer efficiency without requiring complex manual tuning procedures
Solution Approach 2:
The system performs self-adjustment by automatically detecting frequency mismatch through the monitored signal characteristic and correcting its own drive frequency. This self-service mechanism eliminates the need for external intervention or complex tuning equipment, maintaining simplicity while improving energy transfer efficiency
2Productivity
If the drive frequency is adjusted to match the system resonant frequency, then the recharging time is reduced, but the system requires continuous monitoring and adjustment which increases operational complexity
Solution Approach 1:
The control circuit continuously monitors the characteristic signal and automatically adjusts the drive frequency to maintain resonance. This closed-loop feedback system maintains optimal recharging speed without requiring user intervention, as the system self-corrects frequency drift caused by coil deformation or environmental changes
Solution Approach 2:
The system dynamically adapts the drive frequency in real-time based on the monitored signal characteristic. This dynamic adjustment allows the system to maintain optimal recharging performance despite changes in coil configuration or environmental conditions, while the automation keeps operation simple
3Object-affected harmful factors
If the primary coil operates away from resonant frequency, then the system is more tolerant of frequency variations, but heat dissipation increases reducing patient comfort
Solution Approach 1:
The system uses feedback from the monitored signal characteristic to maintain precise frequency alignment with the resonant frequency. This ensures maximum energy transfer efficiency and minimal heat dissipation, thereby maintaining patient comfort while the system remains tolerant of frequency variations through automatic correction
Solution Approach 2:
The system converts the potential harm of frequency mismatch (which would cause heat dissipation) into a detectable signal characteristic. By monitoring for the appearance of this characteristic, the system can adjust the frequency to prevent heat generation, thereby turning a harmful effect into a useful monitoring mechanism
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 allows for real-time adjustment of the drive frequency to maintain optimal efficiency during recharging, reducing recharging time and minimizing heat dissipation, thus enhancing the comfort and efficiency of the process.
Implementation Method 1
power can be transferred by inductively coupling an external primary coil that is positioned on or near the skin of a patient with a secondary coil that is coupled to, or included within, an implantable medical device
Implementation Method 2
To transfer energy as efficiently as possible, it may be desirable to tune the frequency of the signal being generated within the primary coil... the optimal frequency at which to drive the primary coil may be based, in part, on the electrical properties of the antenna containing the primary coil as well as the other circuitry associated with the primary coil
Data Source
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AI summary
Techniques are disclosed for tuning a frequency at which an external device transcutaneously transfers energy. The transferred energy may be used to charge a rechargeable power source of an implantable medical device (IMD) and/or to power the IMD directly. One embodiment relates to a charging system that may comprise a circuit to drive a primary coil of an external device at a drive frequency and a control circuit to tune the drive frequency based on a characteristic of a monitored signal that is associated with the primary coil. The characteristic is not present when the primary coil is being driven at a resonant frequency of the system. In a specific example, the characteristic comprises a stub pulse and the control circuit is configured to tune the drive frequency based on at least one of a relative timing and a width of the stub pulse.