Axial Leaded PTC Over-Current Protection Device Parallel Resistance
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Solution Overview
Problem
Conventional axial leaded over-current protection devices with positive temperature coefficient (PTC) materials have high initial resistance, which limits their application in small appliances and can be triggered by high process temperatures, such as those encountered in injection molding, leading to reduced functionality.
Innovation Solution
An axial leaded over-current protection device with a stack strap structure comprising multiple PTC devices connected in parallel, where terminal metal strips diverge into electrode strips to reduce resistance, allowing for lower initial resistance without significant volume increase, enabling use in small appliances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the PTC element is increased to lower the initial resistance, then the resistance decreases, but the device volume increases making it unsuitable for small appliances
Solution Approach 1:
The patent divides a single large PTC element into multiple smaller PTC elements (first PTC element and second PTC element). These segmented elements are connected in parallel between the terminal metal strips, allowing each element to have smaller area while achieving lower overall resistance through the parallel configuration. This resolves the contradiction by maintaining low resistance without requiring a large device volume.
Solution Approach 2:
The patent transitions from a single-plane PTC element layout to a three-dimensional stacked configuration. The first and second PTC elements are arranged in different spatial layers and connected in parallel, effectively utilizing vertical space. This dimensional change allows the device to achieve lower resistance without increasing the footprint area, thus suitable for compact small appliances.
2Device complexity
If a single PTC element is used, then the device structure is simple, but the resistance is high limiting application scope
Solution Approach 1:
The patent segments the single PTC element into multiple smaller elements connected in parallel. This segmentation reduces the overall resistance while maintaining relatively simple structure through standardized connection methods using terminal metal strips. The segmented approach allows resistance reduction without proportionally increasing structural complexity.
3Reliability
If the PTC element area is increased to reduce resistance, then resistance decreases, but the device becomes too large for small appliances
Solution Approach 1:
By segmenting the PTC element into multiple smaller units connected in parallel, the patent achieves low resistance without requiring large device area. This makes the device adaptable to various applications including small appliances where space is constrained, thus expanding the application scope while maintaining low resistance performance.
Solution Approach 2:
The patent creates a universal PTC device structure that can be applied across different applications. The parallel configuration of multiple PTC elements with terminal metal strips provides a standardized, low-resistance solution that fits both traditional and space-constrained applications like small appliances, enhancing versatility.
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
The solution effectively decreases the resistance of the over-current protection device, expanding its application scope while maintaining compact size, and improving recovery from tripped states, thus enhancing its usability in various applications including batteries.
Implementation Method 1
The resistance of a positive temperature coefficient (PTC) conductive material is sensitive to temperature variation and can be kept extremely low during normal operation so that the circuit can operate normally. However, if an over-current or an over-temperature event occurs, the resistance will immediately increase to a high resistance state
Data Source
AI summary
An axial leaded over-current protection device comprised of a plurality of PTC devices, a first terminal metal strip, and a second terminal metal strip. One end of the first terminal metal strip diverges into a plurality of electrode strips, and the plurality electrode strips are connected to an electrode layer of each PTC device. The second terminal metal strip is connected to the other electrode layer of each PTC device, i.e., the one not being connected to the first terminal metal strip. Accordingly, the first terminal metal strip and second terminal metal strip are respectively connected to the two electrode layers of each PTC device and become in parallel thereby, so that the resistance of the over-current protection device can be decreased.