Implant Charger Coil Assembly With Thermal Diffuser Cooling
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Solution Overview
Problem
Existing external chargers for implantable medical devices face challenges in thermal management due to Eddy currents generated by the charging coil, leading to overheating and limited charging power, and the placement of temperature sensors is inefficient, making them prone to damage and inaccurate temperature readings.
Innovation Solution
The charger system is redesigned with a separable electronics module and charging coil assembly connected by a cable, incorporating a thermal diffuser within the charging coil assembly to dissipate heat effectively, and placing temperature sensors directly on the circuit board to accurately measure temperature without lead wires, ensuring efficient and reliable charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the charging coil generates magnetic field for wireless power transmission, then charging power is provided to the implantable medical device, but Eddy currents are generated causing overheating and thermal management issues
Solution Approach 1:
A thermal diffuser is introduced as an intermediary component between the charging coil and the housing. The thermal diffuser includes a first portion in contact with the charging coil and a second portion in contact with the housing, creating a thermal management pathway that allows heat to be dissipated through the housing to the patient's body, thereby preventing overheating while maintaining charging power
Solution Approach 2:
The patent converts the harmful thermal energy generated by Eddy currents into a beneficial cooling mechanism. By allowing controlled heat transfer through the housing to the patient's body (which acts as a heat sink), the system transforms waste heat into a manageable thermal flow, preventing dangerous temperature buildup while maintaining charging functionality
2Measurement precision
If temperature sensors are connected with lead wires, then temperature can be measured, but the sensors are prone to damage and placement is inefficient
Solution Approach 1:
The patent replaces the mechanical lead wire connection system with a wireless communication system. Temperature sensors communicate their readings wirelessly to the control circuitry, eliminating the need for physical lead wires that could damage the sensors or interfere with their placement. This substitution maintains measurement precision while significantly improving sensor reliability and placement efficiency
3Device complexity
If the external charger is designed as integrated unit, then device complexity is reduced, but thermal management becomes difficult and charging efficiency is limited
Solution Approach 1:
The patent segments the external charger into functionally independent modules: a charging coil assembly with integrated thermal diffuser, a separate electronics module with control circuitry, and a housing. This segmentation allows each module to be optimized independently - the charging coil assembly focuses on power transmission with built-in thermal management, while the electronics module handles control and communication - thereby improving charging efficiency without excessive complexity
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
The redesigned charger system effectively manages thermal issues, allowing faster and more efficient charging of implantable medical devices by preventing overheating and providing accurate temperature sensing, thus enhancing the charging process.
Implementation Method 1
Power transmission from the external charger to the IMD occurs wirelessly and transcutaneously through a patient's tissue via inductive coupling. Primary charging coil in the external charger is energized via charging circuit with an AC current, Icharge, to create the AC magnetic field. This magnetic field induces a current in the secondary charging coil within the IMD
Implementation Method 2
The charging coil assembly includes a thermal diffuser. The thermal diffuser includes a first portion in contact with the charging coil and a second portion in contact with the housing. The thermal diffuser facilitates heat transfer from the charging coil through the housing to the patient's body
Implementation Method 3
The charging coil assembly includes at least one temperature sensor, such as a thermistor, that reports a temperature of the charging coil assembly to control circuitry
Data Source
AI summary
An external charging system for an Implantable Medical Device (IMD) is disclosed having a thermal diffuser proximate to the primary charging coil for distributing heat from the primary charging coil. In an example, the primary charging coil is mounted to a first side of a circuit board, and the thermal diffuser is also connected to the first side and in contact with the primary charging coil. In one example, the thermal diffuser is a plastic material, such as an acrylic pad, with a high thermal conductivity and a low electrical conductivity. The thermal diffuser may also contact temperature sensors mounted to the first side of the circuit board.