External Coil Current Limiting for LVAD Safety
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Solution Overview
Problem
Current implanted medical device systems face challenges in safely and efficiently managing electromagnetic field exposure and power transfer, particularly in limiting current in external coils to ensure patient safety and prevent interference with other devices.
Innovation Solution
The system employs processing circuitry in the external power transmitter to dynamically adjust the current limit of the external coil based on operational modes, alarm conditions, and power transfer status, transitioning between low and high current limits to optimize power transfer and minimize electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high current limit is applied to external coil for efficient power transfer, then power delivery efficiency is improved, but electromagnetic field exposure and interference with other devices increases
Solution Approach 1:
The system dynamically adjusts the external coil current limit based on operational conditions. The processing circuitry transitions between low and high current limits according to whether TETS power transfer is active, alarm conditions exist, or free mode is intended. This dynamic adjustment allows the system to optimize power delivery efficiency when needed while minimizing electromagnetic field exposure during other operational states.
Solution Approach 2:
The system changes the current limit parameter of the external coil based on operational mode. When TETS power transfer is active, the current limit is increased to high levels for efficient power delivery. When TETS is inactive or alarm conditions exist, the current limit is reduced to low levels to minimize electromagnetic field exposure and interference with other implanted devices.
2Object-affected harmful factors
If dynamic current limit adjustment is implemented, then electromagnetic field exposure is minimized, but system complexity increases
Solution Approach 1:
The processing circuitry monitors operational conditions including TETS power transfer status, alarm conditions, and free mode intent. Based on this feedback, the system automatically transitions between low and high current limits. This feedback mechanism enables intelligent current limit adjustment without requiring complex manual control systems, as the processing circuitry autonomously makes decisions based on monitored system state.
3Object-generated harmful factors
If low current limit is applied to external coil, then electromagnetic interference is minimized, but power transfer efficiency decreases
Solution Approach 1:
The system dynamically switches between low and high current limits based on operational needs. During TETS power transfer operations, the current limit is raised to high levels to ensure efficient power delivery. During free mode or when alarms are present, the current limit is lowered to minimize electromagnetic interference. This dynamic switching resolves the contradiction by applying the appropriate current limit level at the appropriate time.
Solution Approach 2:
The processing circuitry periodically evaluates operational conditions and transitions between current limit levels accordingly. The system monitors for changes in TETS power transfer status, alarm conditions, and free mode intent, adjusting the current limit in response to these periodic assessments of system state.
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 effectively constrains electromagnetic field exposure, ensures patient safety, prevents component damage, and minimizes interactions with other implanted devices, while allowing for efficient power delivery and reduced interference during different operational states.
Implementation Method 1
The coils 18 and 20 transfer power by mutual induction of electromagnetic energy over the air and through the body.
Data Source
AI summary
An external power transmitter of an implanted medical device system such as a left ventricular assist device (LVAD) system and a method therefore are provided. According to one aspect, a method includes transitioning from applying a first external coil current limit to applying a second external coil current limit to limit current of an external coil coupled to the external power transmitter, the transitioning being based on at least one of an intent to enter a free mode of operation of the implanted medical device system, an existence of an alarm condition, and an existence of transcutaneous energy transfer system (TETS) power transfer.