PTC Over-Current Protection Device with Heating Element
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Solution Overview
Problem
Over-current protection devices with low resistivity fail to trip easily at specific temperatures, particularly at high temperatures, which is a concern for quick charge applications and safety specifications.
Innovation Solution
Incorporating a heating element with sufficient resistance into the over-current protection device to accelerate the tripping of the PTC device, ensuring effective over-current protection by reducing the hold current when activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a PTC device maintains high hold current at elevated temperatures for quick charge, then quick charge performance is improved, but the device cannot trip within safety time limits when over-current occurs
Solution Approach 1:
The heating element is pre-positioned within the PTC device structure, ready to activate when needed. This preliminary arrangement ensures that when over-current detection occurs, the tripping action can be initiated immediately without delay, meeting safety time limits while preserving quick charge performance during normal operation.
Solution Approach 2:
The device dynamically changes its resistance parameter based on operational conditions. During normal quick charge operation, the PTC device maintains low resistance for high current flow. When over-current is detected, the heating element activates to rapidly increase the temperature, causing the PTC material's resistance to surge and trip the device within safety time limits.
2Reliability
If the PTC device has low resistivity for high current applications, then the device allows high hold current, but the tripping temperature is not easily reached
Solution Approach 1:
The heating element provides continuous heating action once activated, ensuring that the tripping temperature is reliably achieved and maintained. This continuous thermal input overcomes the low resistivity characteristic that normally prevents temperature rise, ensuring consistent tripping behavior while preserving high current carrying capacity during normal operation.
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 enables the over-current protection device to sustain high hold currents at elevated temperatures while tripping quickly within 60 seconds when necessary, meeting safety criteria and enhancing protection during quick charge applications.
Implementation Method 1
the heating element is operable to heat the PTC device
Implementation Method 2
The resistive material has PTC characteristic; that is, the resistance of the PTC material remains extremely low at a normal temperature; however when an over-current or an over-temperature occurs in the circuit, the resistance instantaneously increases to a high resistance state
Data Source
AI summary
An over-current protection device comprises a PTC device and a heating element operable to heat the PTC device. The PTC device contains crystalline polymer and metal or ceramic conductive filler dispersed therein. The PTC device has a resistivity less than 0.1 Ω·cm. The over-current protection device has the relation: It (heating)<Ih (60° C.)×10%, where Ih (60° C.) is a hold current of the over-current protection device at 60° C. when the heating element is not activated; It (heating) is a trip current of the over-current protection device when the heating element is activated to heat the PTC device. The PTC device has high hold current, thereby allowing a battery containing the device can be fast charged with a large current. In a specific situation, the heating element heats the PTC device to decrease the hold current of the over-current protection device of low resistivity, and accordingly the PTC device can trip by a small current.