Power Control Circuit for Ethylene Oxide Sterilization Safety
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Solution Overview
Problem
Sterilizable trial stimulators for implantable neurological stimulation systems face challenges in being safely sterilized in flammable environments, as ethylene oxide gas used for sterilization is highly flammable and can ignite due to residual electrical energy in the devices.
Innovation Solution
A power control circuit that includes a bi-stable switch to drain energy storage elements in the trial stimulator to a level below the ignition threshold of the sterilizing gas, allowing safe exposure to flammable gases without breaking the sealed packaging, and a remotely actuatable switch to activate the device post-sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the trial stimulator is sterilized using ethylene oxide gas, then sterilization is achieved, but the risk of explosion increases due to residual electrical energy igniting the flammable gas
Solution Approach 1:
The power control circuit is activated before sterilization to drain energy from storage elements (capacitors, batteries) to below the ignition threshold of ethylene oxide gas. This preliminary energy reduction prevents explosion during sterilization while maintaining the ability to complete the sterilization process effectively.
Solution Approach 2:
The circuit dynamically changes the energy parameter of storage elements by controlling discharge pathways. During sterilization, energy is reduced to safe levels; after sterilization, energy is restored to functional levels, allowing the device to operate normally post-sterilization.
2Reliability
If the device is kept in sealed packaging during sterilization, then protection from contamination is maintained, but testing and updates cannot be performed
Solution Approach 1:
Testing and firmware updates are performed before the device is placed in sealed packaging for sterilization. The power control circuit enables these pre-sterilization tests to verify device functionality, ensuring the device works correctly before committing to sterilization and sealing.
Solution Approach 2:
The device lifecycle is segmented into distinct phases: pre-sterilization testing phase, sterilization phase in sealed packaging, and post-sterilization usage phase. The power control circuit manages transitions between these phases, enabling testing before sealing and ensuring sterility during storage.
3Object-affected harmful factors
If energy storage elements are completely discharged for sterilization safety, then explosion risk is eliminated, but battery charge is depleted and device cannot function
Solution Approach 1:
Energy is temporarily reduced to safe levels only during the sterilization process. Before sterilization, the device maintains full charge for normal operation. The power control circuit orchestrates this temporary energy reduction, draining storage elements during sterilization while preserving battery charge for post-sterilization functionality.
Solution Approach 2:
The power control circuit dynamically adjusts the energy state of storage elements based on the operational phase. During sterilization, energy is drained to safe levels; during normal operation, energy is restored to functional levels. This dynamic control eliminates ignition risk during sterilization while maintaining battery charge availability for device operation.
Data Source
AI summary
A power control circuit for use with devices that will be placed in a flammable sterilizing gas includes a bi-stable switch that is configured to produce an output to place the circuitry of a connected device in a run state or a sleep state. The bi-stable switch controls one or more transistors to drain energy from energy storage devices in the circuitry of the connected device to a level below an ignition level of a sterilizing gas. A remotely actuatable switch can be actuated from outside of a packaging in which the power control circuit is placed to cause the bi-stable switch to produce an output that puts the circuitry in the run state without removing the power control circuit from the packaging.