TETS Power Regulation Using External Coil Current Feedback
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Solution Overview
Problem
Current implantable medical device systems, such as LVADs, face challenges in regulating Transcutaneous Energy Transfer System (TETS) power due to varying operating conditions and resistive losses, leading to inconsistent power delivery to implanted devices.
Innovation Solution
The implementation of an external power transmitter with processing circuitry that determines and adjusts the current in the external coil by multiplying the determined current by the supply voltage, controlling power delivery through pulse-width-modulated bridge circuits, and using a PID controller to maintain constant power over different supply voltages, accounting for resistive losses and continuous measurement of peak currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power is supplied from external transmitter to implanted device via TETS, then power delivery is achieved, but power delivery becomes inconsistent due to varying operating conditions and resistive losses
Solution Approach 1:
The system continuously measures the current in the external coil and uses this feedback to adjust the PWM duty cycle, maintaining consistent power delivery despite varying operating conditions and resistive losses. The processing circuitry monitors power delivery in real-time and dynamically adjusts the H-bridge circuit to compensate for changes in coil resistance and coupling conditions.
Solution Approach 2:
The system dynamically changes the PWM duty cycle parameter to maintain constant power delivery. By adjusting this control parameter based on measured current and known resistance values, the system compensates for resistive losses and varying operating conditions, ensuring reliable power transfer to the implanted device.
2Power
If PWM duty cycle is adjusted to control power, then power regulation is achieved, but sensitivity to coil alignment and positioning changes increases
Solution Approach 1:
The system measures the actual current in the external coil and uses this feedback to adjust the PWM duty cycle, maintaining consistent power delivery despite varying coil alignment. The closed-loop control compensates for changes in mutual coupling and resistance caused by positioning variations, reducing sensitivity to alignment changes.
3Measurement precision
If current measurement is performed continuously, then power control precision is improved, but device complexity increases
Solution Approach 1:
The system replaces complex continuous measurement circuitry with a simplified approach that uses periodic current measurements combined with PWM duty cycle control. The processing circuitry calculates power delivery based on measured current and known resistance values, achieving precise control without requiring complex continuous measurement hardware.
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 solution ensures nearly constant power delivery to implanted devices, reducing sensitivity to coil alignment and positioning changes, and minimizing the impact of electromagnetic interference, thereby enhancing the reliability and stability of the TETS power regulation.
Implementation Method 1
power is supplied from the external power transmitter 21 to the i-controller 14 via mutual coupling of the coils 18 and 20, in order to charge the internal battery 15 of the i-controller 14 and to power the LVAD pump 12. The coils 18 and 20 transfer power via electromagnetic energy over the air and through the body.
Data Source
AI summary
In an implanted medical device system, an internal controller, external power transmitter and methods for regulation of TETS power for an implanted medical device system are disclosed. According to one aspect, a method in an external power transmitter of an implanted medical device system includes determining a current in an external coil of the external power transmitter, multiplying the determined current by a supply voltage to determine a power delivered to the external coil, and controlling the power delivered to the external coil by adjusting the current in the external coil.