High Impedance Coin-Cell Battery Management for Implantable Devices
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Solution Overview
Problem
Coin-cell type batteries with high impedance are not suitable for implantable medical devices due to their high output impedance, which causes voltage drops, making them unreliable for applications requiring consistent power delivery, especially in implantable neurostimulators where low impedance is crucial for reliable operation.
Innovation Solution
A small implantable medical device using a high impedance coin-cell type battery that generates electrical stimulation pulses with a low duty cycle, featuring battery control circuitry to manage current draw and prevent voltage drops, allowing the use of commercially available, thin, and inexpensive coin-cell batteries for powering the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a high impedance coin-cell battery is used to power the implantable device, then the device can be made thinner and more cost-effective, but the output voltage drops significantly under load, compromising device reliability
Solution Approach 1:
A voltage regulator circuit is introduced as an intermediary component between the high impedance coin-cell battery and the implantable device. This regulator maintains stable output voltage despite the battery's high internal impedance and varying load conditions, enabling the use of thin coin-cell batteries without compromising voltage stability or device reliability
2Ease of manufacture
If a high impedance coin-cell battery is used, then manufacturing cost is reduced by using commercially available batteries, but the instantaneous current draw causes excessive voltage drop
Solution Approach 1:
A power management circuit with voltage regulation and current limiting functionality is introduced as an intermediary between the coin-cell battery and the device. This circuit enables the use of commercially available high impedance batteries by managing the instantaneous current draw and preventing excessive voltage drops, thus maintaining adequate power delivery while preserving manufacturing simplicity
3Device complexity
If the battery impedance is kept high for cost and size benefits, then device complexity is reduced, but the duty cycle must be limited to maintain acceptable voltage levels
Solution Approach 1:
A feedback control mechanism is implemented in the power management circuit that monitors battery voltage and adjusts current delivery accordingly. This feedback system allows the device to operate with high impedance coin-cell batteries while maintaining voltage within acceptable ranges, effectively managing the duty cycle without requiring complex external power management infrastructure
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
Enables the use of high impedance coin-cell batteries in implantable medical devices by managing current draw and maintaining stable voltage, making the device thinner, more affordable, and suitable for long-term implantation without the need for custom-made batteries.
Implementation Method 1
Coin-cell type batteries are known in the art. They can be used for just about any electronic device or circuit where small size is needed
Implementation Method 2
This high output impedance causes the output voltage of the battery to drop below its nominal voltage value as a function of the instantaneous output current drawn from the battery as a function of ohm's law, V=IR
Data Source
AI summary
An implantable electroacupuncture device for treating a medical condition of a patient through application of electroacupuncture stimulation pulses to a target tissue location within the patient includes 1) a housing configured to be implanted beneath a skin surface of the patient, 2) pulse generation circuitry located within the housing and electrically coupled to at least two electrodes, the pulse generation circuitry being adapted to deliver stimulation sessions by way of the at least two electrodes to the target tissue location in accordance with a stimulation regimen, and 3) a primary battery contained within the housing and electrically coupled to the pulse generation circuitry, the primary battery having an internal impedance greater than 5 ohms and a capacity of less than 60 mAh, wherein the primary battery is the only battery that provides power to the pulse generation circuitry.