RF Telemetry Power Supply for Implantable Medical Devices
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Solution Overview
Problem
Active implantable medical devices face challenges in providing the high current required for RF telemetry circuits due to the internal resistance of batteries used in pacemakers and defibrillators, which limits the operational range of RF telemetry and necessitates additional battery types or complex setups.
Innovation Solution
A regulating circuit with an accumulator and load circuit is implemented between the supply battery and the RF telemetry circuit, allowing for cyclic and intermittent operation to maintain a predetermined voltage level, using a lithium-ion accumulator or capacitor to supply the necessary current, and incorporating a voltage multiplier to adapt to the battery's voltage, enabling efficient power delivery to the RF circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium-iodine battery is used to power pacemaker circuits, then the device can operate with low current consumption, but the battery's internal resistance increases to 100-1000Ω which prevents providing the high current needed for RF telemetry circuits
Solution Approach 1:
The power supply system is segmented into two distinct batteries: a lithium-iodine battery for low-power circuits (stimulation and detection) and a lithium-manganese button battery for high-power RF telemetry. This segmentation allows each battery to be optimized for its specific power requirements, resolving the contradiction between low current consumption and high current delivery capability.
Solution Approach 2:
A voltage regulator circuit acts as an intermediary between the lithium-manganese battery and the RF telemetry circuit. This regulator manages the high current delivery while protecting the battery and ensuring stable operation, enabling the RF circuit to receive sufficient current without directly burdening the battery's internal resistance limitations.
2Ease of operation
If RF telemetry circuit is implemented to enable remote programming and data exchange, then the operational range is extended beyond 3 meters, but the current consumption exceeds 3 mA which cannot be provided by the existing battery
Solution Approach 1:
The patent merges two different battery technologies (lithium-iodine and lithium-manganese) into a single dual-battery system. The lithium-manganese button battery specifically supplements power for RF telemetry operations, enabling extended operational range while the lithium-iodine battery continues to power low-consumption circuits, thus resolving the energy consumption contradiction.
3Power
If an additional lithium-manganese button battery is added to provide high current for RF circuits, then the current requirement is satisfied, but the device complexity and surgical implantation difficulty increase
Solution Approach 1:
The lithium-manganese button battery is designed as a consumable component with a limited lifespan (approximately 2-5 years). When it depletes, only this small button battery needs replacement rather than the entire implant system. This approach manages device complexity by making the high-power component replaceable and relatively simple in design.
Solution Approach 2:
The additional button battery is positioned locally within the implant housing, optimized specifically for RF telemetry power needs. This localized placement and specialization allows the rest of the device to maintain its original simple architecture, minimizing the increase in overall device complexity while still providing the necessary high current capability.
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 allows for reliable and efficient operation of RF telemetry circuits in active implantable medical devices by providing the required high current without the need for additional batteries, ensuring consistent communication and data exchange over extended distances without external intervention.
Implementation Method 1
a regulating circuit (16) including an accumulator of electric power (12), coupled with the auxiliary circuit to deliver a current ready to feed this auxiliary circuit
Implementation Method 2
When the voltage corresponding to the predetermined level of load is higher than the voltage delivered by the supply battery, the load circuit includes a voltage multiplying stage
Implementation Method 3
using the two components of an electromagnetic wave produced by emitting/receiving circuits operating in the field of radio frequencies (RF)
Data Source
AI summary
An active implantable medical device having an RF telemetry circuit. The device is in particular a stimulation, resynchronization, defibrillation and/or cardioversion device. It includes a principal circuit, an RF telemetry auxiliary circuit and a supply battery for the principal and auxiliary circuits. It is envisaged to have between the supply battery and the auxiliary circuit a regulating circuit including an accumulator of electric power coupled with the auxiliary circuit to deliver a current ready to feed the auxiliary circuit, and a load circuit coupled with the supply battery to maintain the accumulator on a predetermined level of load.