Implant Charging Current Control via Temperature Feedback
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Solution Overview
Problem
Conventional inductive charging of implantable medical devices (IMDs) is inefficient due to temperature limitations, leading to excessive heat generation and prolonged charging times, especially for newer implants that require more frequent charging.
Innovation Solution
A method involving a temperature sensor in the IMD to dynamically adjust the current of the battery charge signal based on temperature readings, allowing for controlled charging to maintain the temperature within safe limits, thereby optimizing charging efficiency and reducing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inductive charging is performed at high charging rates to reduce charging time, then charging efficiency is improved, but temperature increases to undesirable levels
Solution Approach 1:
The charging current is dynamically adjusted based on real-time temperature feedback from the temperature sensor. The system transitions from a static charging approach to a dynamic one where the charging rate changes continuously to maintain temperature within safe limits while maximizing charging speed.
Solution Approach 2:
A temperature sensor provides continuous feedback about the IMD temperature during charging. This feedback is used by the control system to adjust the charging current, creating a closed-loop control system that prevents overheating while maintaining efficient charging.
2Temperature
If charging is performed at low charging rates to avoid excessive heat, then temperature is controlled, but charging time increases
Solution Approach 1:
Rather than using a fixed low charging rate, the system dynamically adjusts the charging rate based on temperature conditions. When temperature is low, higher charging rates are used; when temperature approaches limits, the rate is reduced, optimizing both time and temperature control.
Solution Approach 2:
The charging current parameter is changed dynamically during the charging process based on temperature measurements. The system transitions between different charging current levels to optimize the trade-off between charging speed and temperature control.
3Temperature
If charging is completely shut down when excessive temperature is reached, then temperature safety is ensured, but charging efficiency decreases and charging time increases
Solution Approach 1:
Instead of completely shutting down charging when temperature limits are approached, the system applies partial action by reducing the charging current to a lower non-zero level. This maintains some charging activity while controlling temperature, avoiding the inefficiency of complete shutdowns.
Solution Approach 2:
The charging system transitions from a binary on/off control to a dynamic continuous adjustment of charging current. This allows the system to maintain charging operation across a range of temperature conditions rather than abruptly stopping.
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 enables faster and more efficient charging of IMDs by preventing excessive heat buildup, reducing charging time, and improving overall charging efficiency while ensuring patient safety.
Implementation Method 1
receiving, via the receiver, a wireless power signal from an external charger and converting the wireless power signal into a battery charge signal
Implementation Method 2
sensing a temperature of the implantable medical device with the temperature sensor
Implementation Method 3
Eddy currents form in the housing of the IMD during charging and these currents are converted into undesirable heat
Implementation Method 4
some of the inductive signal in the recharging circuitry within the IMD is also converted into heat
Data Source
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AI summary
A method for wirelessly charging a battery in an implantable medical device including the steps of: providing a receiver in the implantable medical device and providing a temperature sensor in the implantable medical device. The method also includes receiving, via the receiver, a wireless power signal from an external charger and converting the wireless power signal into a battery charge signal including power for recharging the battery. The method yet also includes sensing a temperature of the implantable medical device with the temperature sensor. The method further includes changing a current of the battery charge signal from a first non-zero current to a second non-zero current that is different from the first non-zero current. Changing of the current of the battery charge signal is based on the temperature sensed by the temperature sensor.