One-Shot Battery Circuit for Lithium Passivation Voltage Delay
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Solution Overview
Problem
Lithium primary battery-powered one-shot devices face issues with passivation, which leads to voltage delay and potential failure when activated after long periods of dormancy, as the battery's surface resistance increases, preventing immediate power delivery to critical components.
Innovation Solution
Implementing a system where the logic subsystem remains in an ultra-low power state during storage, continuously drawing a small current to minimize passivation growth, and using environmentally controlled or logic-controlled power switches to manage power application, allowing for gradual power sequencing and periodic current bursts to break down the passivation layer, ensuring timely and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the battery is allowed to passivate during long-term storage, then shelf life is extended, but voltage delay occurs upon activation
Solution Approach 1:
The patent applies preliminary action by implementing a wake-up circuit that periodically activates before the main device operation to break down the passivation layer in advance. This preliminary current flow removes the high-resistance barrier that would otherwise cause voltage delay during actual device activation, thus resolving the contradiction between extended shelf life and immediate operational readiness.
2Ease of manufacture
If the battery capacity is reduced to decrease cost and size, then device cost and size are reduced, but power delivery capability is compromised
Solution Approach 1:
The wake-up circuit performs preliminary action by breaking down the passivation layer before main operation, enabling smaller batteries to deliver their full power capability without delay. This allows the use of reduced-capacity, lower-cost batteries while maintaining the required power delivery capability when the device is activated.
3Device complexity
If no periodic maintenance is performed during storage, then device complexity is reduced, but battery passivation increases
Solution Approach 1:
The wake-up circuit implements self-service by automatically performing the maintenance function of breaking down the passivation layer without requiring external periodic intervention. The circuit autonomously activates to remove passivation, eliminating the need for user-performed periodic maintenance while preventing excessive passivation accumulation.
4Loss of energy
If a mechanical power switch is used to limit power draw during storage, then energy conservation is improved, but immediate power delivery upon activation is delayed
Solution Approach 1:
The power delivery system is segmented into two distinct phases: a wake-up phase handled by the wake-up circuit that breaks down passivation, and a main operation phase activated by the mechanical power switch. This segmentation allows the mechanical switch to remain closed during storage for energy conservation, while the separate wake-up circuit ensures rapid power delivery capability is maintained by pre-breaking the passivation layer.
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 approach effectively mitigates the effects of passivation, ensuring that one-shot devices can operate immediately upon activation without voltage delay, maintaining reliability and extending shelf life while managing battery capacity and safety considerations.
Implementation Method 1
Over time lithium primary cells, that are not being used, build up a high resistance barrier on the surface of the anode. This phenomenon is known as passivation.
Implementation Method 2
The current drawn by the circuit breaks down the passivation barrier and allows the current to flow. This process takes a small amount of time, often referred as the battery's voltage delay time.
Data Source
AI summary
Battery operated one-shot (energetic firing) device having logic subsystem connected to source and operated in ultra-low power idle mode during storage to continuously draw a small amount of current from power source to reduce growth of passivation layer thereon. Power switch(es) throttle application of power to other components (e.g., environmental sensing circuit, energetic fire circuit) until device is active. Power switch(es) may be mechanical switch(es) manually operated or controlled by environmental conditions or logic-controlled switch(es). Power switch(es) can be used to sequentially provide power to other components to minimize voltage dip caused by de-passivation of power source. Logic subsystem may include current pulse generator for causing a current burst to be drawn from power supply to break down passivation layer and timer for tracking time since last current burst, both operational in ultra-low power idle mode. Bursts may occur at defined intervals as required by system design and shelf-life requirements.