Implantable Charging Circuit With Coil Detuning for Heat Control
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Solution Overview
Problem
Existing implantable medical devices (IMDs) face challenges in efficiently and safely charging their batteries wirelessly, as rapid charging can lead to excessive heat and tissue damage due to improper regulation of charging energy.
Innovation Solution
A wireless charging system for IMDs that includes a series switch and voltage regulation circuitry to control charging energy, using a series LC circuit configuration with a series switch between the coil and rectifier, and a coil clamp control circuit to detune the inductive coupling element in the OFF state, minimizing feedthrough paths and preventing high voltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wireless charging energy is input into the IMD quickly to charge the battery rapidly, then the charging speed and productivity are improved, but the temperature of the IMD increases to dangerous levels causing tissue damage
Solution Approach 1:
The patent implements dynamic control of the wireless charging process by switching between ON and OFF states. The system dynamically adjusts the charging energy input based on real-time conditions, enabling rapid charging when safe and preventing overheating when temperature thresholds are approached. This dynamic switching resolves the contradiction between charging speed and temperature control.
Solution Approach 2:
The patent employs feedback mechanisms through temperature sensors and control circuitry that continuously monitor the IMD temperature and adjust the charging process accordingly. When temperature approaches dangerous levels, the system reduces or pauses energy input, and when temperature is safe, it resumes rapid charging. This feedback loop enables the system to achieve fast charging while preventing tissue damage.
2Loss of energy
If wireless charging energy is input into the IMD without proper regulation to maximize power transfer, then the energy transfer efficiency is improved, but the temperature of the IMD increases causing tissue damage
Solution Approach 1:
The system dynamically modulates the wireless energy transfer by switching the IMD between charging and non-charging states. During ON periods, energy transfer occurs at high efficiency; during OFF periods, energy transfer is halted to allow temperature dissipation. This dynamic approach maintains high overall energy efficiency while preventing dangerous temperature accumulation.
Solution Approach 2:
The patent implements periodic charging cycles with alternating ON and OFF periods. During ON periods, wireless energy transfer operates at maximum efficiency to quickly recharge the battery. During OFF periods, energy transfer is suspended to allow thermal management. This periodic action pattern resolves the contradiction between maintaining high energy transfer efficiency and preventing temperature-related tissue damage.
3Reliability
If the coil is detuned during the OFF state to prevent resonance-induced high voltages, then the safety and reliability are improved, but the charging efficiency during the ON state may be affected
Solution Approach 1:
The patent segments the coil operation into distinct ON and OFF states with different configurations. During the ON state, the coil is tuned for maximum charging efficiency. During the OFF state, the coil is detuned to prevent resonance-induced high voltages and improve safety. This segmentation allows each state to be optimized independently, resolving the contradiction between reliability during OFF periods and productivity during ON periods.
Solution Approach 2:
The system dynamically adjusts the coil tuning status based on the operational state. The coil impedance and resonance characteristics are modified during transitions between ON and OFF states. During charging (ON state), the coil is tuned to resonate at the operating frequency for maximum efficiency. During non-charging (OFF state), the coil is detuned to eliminate resonance effects that could cause dangerous voltages. This dynamic tuning resolves the contradiction between charging efficiency and safety.
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 system ensures safe and efficient charging of IMD batteries by regulating charging voltage and preventing resonance-induced high voltages, thereby reducing the risk of tissue damage and optimizing power transfer.
Implementation Method 1
an inductive coupling element including at least one inductor (L) and at least one capacitor (C) coupled to the at least one inductor in a series LC circuit configuration operative to accept RF power from an external charger
Implementation Method 2
a series switch disposed between a first electrical node of the series LC circuit configuration and a bridge rectifier... to prevent a high voltage condition from developing in the series LC circuit configuration that may be caused due to resonance in the OFF state
Data Source
AI summary
A charging energy control system includes an implantable medical device (IMD) and an external charger for effectuating wireless power transfer. The IMD receives charging energy to recharge a battery during an ON period and rejects the charging energy during an OFF period. A series switch is disposed between the IMD's coil and rectifier circuitry that is controlled by voltage regulation circuitry operative to generate a clamp control signal configured to detune the coil in the OFF state.