Implantable Charger Heat Estimation Without IMD Temperature Sensors
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Solution Overview
Problem
Implantable medical devices (IMDs) face challenges in accurately estimating heat generation or temperature during recharging without internal temperature sensors, which can lead to inefficient charging sessions and potential patient discomfort due to elevated temperatures.
Innovation Solution
The system estimates heat generation or temperature by processing circuitry in the external charging device, using algorithms that calculate energy transfer and loss, incorporating factors like resistance, frequency, and current, to control the charging power and duration, even without a temperature sensor in the IMD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If inductive coupling charging is used to extend operational life, then power delivery capability is improved, but heat generation increases causing temperature control issues
Solution Approach 1:
The system implements a feedback mechanism where the external charging device continuously monitors charging parameters and estimates IMD temperature based on power delivery data, resistance measurements, and charging duration. This feedback loop allows the system to adjust charging power in real-time to maintain safe temperature levels while maximizing power delivery capability.
Solution Approach 2:
The patent replaces direct temperature sensing in the IMD with an external estimation system. Instead of using mechanical/physical temperature sensors inside the IMD, the external charging device calculates temperature estimates based on electrical parameters (power, resistance, current) and thermal models, thereby avoiding the need for additional internal sensors while still achieving temperature control.
2Productivity
If charging power is increased to reduce charging time, then productivity is improved, but heat generation increases causing safety concerns
Solution Approach 1:
The charging system dynamically adjusts power delivery based on real-time conditions. The external charging device modifies charging parameters (power level, current, voltage) during the charging process based on estimated temperature, charging stage, and device characteristics. This dynamic control enables fast charging when safe and reduces power when temperature limits are approached, optimizing both charging speed and safety.
Solution Approach 2:
The system changes multiple charging parameters simultaneously including power level, current amplitude, voltage, and charging duration based on the estimated temperature and charging state. By adjusting these parameters dynamically, the system achieves optimal charging speed while maintaining temperature within safe limits to prevent patient discomfort.
3Device complexity
If no temperature sensor is included in the IMD, then device complexity is reduced, but measurement precision of temperature is worsened
Solution Approach 1:
The external charging device acts as an intermediary that performs the temperature measurement function externally. Instead of placing a sensor directly in the IMD, the external device uses electrical parameter measurements (power delivery, resistance, current) and thermal modeling to estimate the IMD temperature, providing accurate temperature information without requiring internal sensors.
Solution Approach 2:
The external charging device leverages its existing sensing and processing capabilities to perform temperature estimation as a self-service function. The charging device uses its built-in power measurement circuits and processing unit to calculate temperature estimates during the normal charging process, eliminating the need for separate temperature sensing hardware in the IMD while maintaining measurement capability.
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 faster and more efficient recharging while maintaining safe operating temperatures, optimizing power delivery and reducing patient discomfort by accurately managing heat generation and temperature within the IMD and charger.
Implementation Method 1
transcutaneous charging may be performed using inductive coupling between a primary coil in the charging device and a secondary coil in the IMD
Implementation Method 2
The external charging device may include a ferrite material adjacent to the primary coil
Implementation Method 3
heat within the IMD and charger by electrical current flowing within electrical components within the IMD and charger
Implementation Method 4
the disclosed systems may use a described algorithm to accurately estimate energy transfer and loss within the recharging system to estimate the heat generated
Data Source
AI summary
A method for controlling charging a power source of an implantable medical device (IMD) in a patient including determining a power being delivered to a primary coil of an external charging device for recharging, determining an estimated power delivered to the IMD power source an estimated heat generated by the primary coil based on a resistance of the primary coil determined as function of at least one of a recharge frequency, a temperature of the primary coil, and a current supplied to the primary coil, calculating an estimated heat generated by the IMD by subtracting the estimated heat generated by the primary coil and the estimated power delivered stored by the rechargeable power source from the power being delivered to a primary coil; and controlling based on the heat generated by the IMD, the power being delivered by the primary coil of the external charging device.