Implantable Device Transformer Impedance Monitoring
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Solution Overview
Problem
Implantable medical devices face the risk of component damage due to high current spikes caused by a transformer's impaired impedance during MRI scans or other ambient conditions, which can lead to premature exit from a special mode or failure to enter a protective mode.
Innovation Solution
An implantable medical device that aborts high voltage charging by comparing a dynamic threshold voltage, calculated from unloaded and loaded battery values and impedance measurements, to determine if the transformer is impaired, thereby preventing damage from excessive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device enters a special mode for MRI scans to protect against transformer saturation, then the risk of component damage is reduced, but the device may still inadvertently exit the special mode prematurely or fail to enter it due to reset or programming errors
Solution Approach 1:
The system continuously monitors the impedance of the primary coil during high voltage charging and compares it against a predetermined threshold. This feedback mechanism allows the system to detect transformer saturation in real-time and abort the charging process automatically, eliminating the need for complex mode management while maintaining high reliability.
Solution Approach 2:
The system performs self-diagnosis by monitoring its own impedance characteristics during operation. The controller automatically detects when the transformer is saturated by measuring the impedance of the primary coil and takes corrective action by aborting the charge, making the system self-protecting without requiring external intervention or complex programming.
2Measurement precision
If the device monitors impedance continuously to detect transformer impairment, then the accuracy of impairment detection is improved, but the complexity of the monitoring system increases
Solution Approach 1:
The system uses the battery voltage as an intermediary measurement to infer impedance changes. By monitoring the voltage across the battery during charging and comparing it to expected values, the system can detect impedance changes without requiring direct impedance measurement circuitry, simplifying the monitoring system while maintaining measurement precision.
Solution Approach 2:
The existing battery voltage measurement circuitry is used for multiple purposes: both for normal charging control and for impedance monitoring to detect transformer saturation. This multi-functional use of existing components avoids adding separate monitoring hardware, reducing system complexity while maintaining measurement accuracy.
3Device complexity
If the device uses a fixed threshold for impedance monitoring, then the simplicity of the threshold comparison is maintained, but the accuracy of transformer impairment detection decreases under varying battery conditions
Solution Approach 1:
The threshold for impedance monitoring is made dynamic by adjusting it based on the measured battery voltage. The system calculates an expected voltage range based on the current battery state and compares actual measurements against this adaptive threshold, maintaining detection accuracy across varying battery conditions while keeping the comparison logic relatively simple.
Solution Approach 2:
The monitoring threshold is changed as a function of battery voltage. As the battery voltage varies during discharge, the expected impedance threshold is adjusted proportionally, allowing the system to maintain accurate detection of transformer saturation regardless of the battery's state of charge, while the adjustment follows a simple mathematical relationship.
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
Effectively prevents component damage by accurately identifying transformer impairment and aborting the high voltage charge, ensuring safe operation during MRI scans and other challenging conditions.
Implementation Method 1
a battery is switched to produce pulses that are provided to a transformer that steps up the voltage
Implementation Method 2
When the strong magnetic field of the MRI machine or other ambient condition saturates the core of the transformer, the inductance of the primary coil is drastically reduced
Data Source
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AI summary
High voltage charging is aborted when it is detected that a transformer providing the high voltage charge is impaired and is providing an impedance that is too low. In one instance, a voltage for a battery that provides power to the transformer is measured when the battery is substantially unloaded and a voltage is later measured when the battery is loaded during the high voltage charge. A dynamic threshold voltage is computed based on a chosen threshold impedance representing the impedance of the transformer and based the substantially unloaded voltage and on an internal resistance of the battery. When the loaded voltage is less than the threshold voltage, then the high voltage charging is aborted.