Reflected Impedance Modulation for Wireless Charger Alignment
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Solution Overview
Problem
Existing wireless external chargers for implantable medical devices face challenges in achieving optimal alignment between the external charger and the implantable device, leading to reduced coupling efficiency and increased power consumption, which can cause heating and potential harm to the patient.
Innovation Solution
The use of reflected impedance modulation to assess the change in coil voltage (ΔV) and coil voltage (Vcoil) during charging pulses to determine alignment, allowing for improved coupling detection and alignment adjustments without interrupting the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional alignment detection methods are used, then alignment can be detected, but the charging process must be interrupted and additional telemetry hardware is required
Solution Approach 1:
The patent combines alignment detection functionality with the existing charging pulses and telemetry coil infrastructure. The same coil used for wireless power transfer is also used to detect alignment by monitoring impedance changes during charging pulses, eliminating the need for separate detection hardware and reducing system complexity.
Solution Approach 2:
The charging coil and control circuitry perform multiple functions: they deliver power to the implantable device during charging pulses and simultaneously detect alignment conditions by measuring reflected impedance. This multi-functionality removes the need for dedicated alignment detection hardware, simplifying the overall system.
2Productivity
If alignment detection is implemented without interrupting charging, then charging efficiency is maintained, but additional control mechanisms are needed
Solution Approach 1:
The system continuously monitors alignment conditions during the charging process without interrupting power transfer. By detecting impedance changes in real-time during charging pulses, the system maintains continuous useful action (charging) while simultaneously assessing alignment, thereby preserving charging efficiency.
Solution Approach 2:
The control circuit monitors reflected impedance changes during charging pulses and uses this feedback to determine alignment conditions. This feedback mechanism enables real-time alignment detection during charging without requiring separate detection phases or interrupting the power transfer process.
3Productivity
If high power is used for charging, then charging speed is improved, but heating and potential harm to the patient increases
Solution Approach 1:
The system dynamically adjusts charging parameters based on detected alignment conditions. When optimal alignment is detected through impedance monitoring, the system can safely deliver higher power for faster charging. When alignment is suboptimal, power is reduced to minimize heating, creating a dynamic adaptation to actual coupling conditions.
Solution Approach 2:
By continuously monitoring impedance changes during charging pulses, the system receives feedback on actual power transfer efficiency and alignment conditions. This feedback enables real-time adjustment of charging power to optimize the balance between charging speed and thermal safety, preventing excessive heating while maintaining efficient charging.
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 method enables more precise alignment detection, reducing power consumption and ensuring efficient charging by identifying optimal alignment conditions, thereby minimizing the risk of overheating and improving charging speed.
Implementation Method 1
Power transmission from the external charger 50 to the IPG 100 occurs wirelessly, and transcutaneously through a patient's tissue 25, via inductive coupling.
Implementation Method 2
The impedance of the charging coil 18 may also be modulated by a single transistor in series with the coil 18, which modulates the impedance by opening the coil
Data Source
AI summary
The disclosed means of determining alignment between an external charger and an implantable medical device (IMD) involves the use of reflected impedance modulation, i.e., by measuring at the external charger reflections arising from modulating the impedance of the charging coil in the IMD. During charging, the charging coil in the IMD is pulsed to modulate its impedance. The difference in the coil voltage (ΔV) produced at the external charger as a result of these pulses is assessed and is used by the external charger to indicate coupling. If the magnitude of ΔV is above a threshold, the external charger considers the coupling to the IMD to be adequate, and an alignment indicator in the external charger is controlled accordingly. The magnitude of Vcoil can be assessed in addition to ΔV to determine alignment with the IMD with improved precision, and/or to further define a high quality alignment condition.