PTC Device Battery Pack Protection Circuit
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Solution Overview
Problem
Existing battery packs with thermal fuses and second protection circuits become unusable after disconnecting due to temporary temperature increases, preventing reuse despite the battery's continued functionality once the temperature decreases.
Innovation Solution
Incorporating a Positive Temperature Coefficient (PTC) device in the current path of the battery pack to control current flow based on internal temperature, allowing for continuous use by adjusting resistance in response to temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal fuse or second protection circuit is used to prevent overcurrent and overheating, then safety is improved, but the battery pack becomes unusable after temporary temperature increases
Solution Approach 1:
The patent applies the dynamics principle by using a PTC device whose resistance dynamically changes with temperature. Unlike static protection devices (thermal fuse, second protection circuit) that permanently disconnect, the PTC device automatically adjusts its resistance: low resistance at normal temperatures allows current flow, high resistance at elevated temperatures limits current. This dynamic response enables the battery pack to be reusable after temperature normalization while maintaining safety during overheating conditions.
2Object-affected harmful factors
If a thermal fuse disconnects the battery group to prevent fire or explosion, then harmful effects are prevented, but continuous use is prevented
Solution Approach 1:
The patent applies the 'blessing in disguise' principle by converting the harmful effect of temperature increase into a beneficial protective mechanism. The PTC device exploits the temperature rise itself to trigger increased resistance, which then limits current and prevents further overheating or thermal runaway. This self-regulating mechanism transforms the potential hazard (temperature increase) into a automatic safety response, preventing fire/explosion while allowing operation to resume after cooling.
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 PTC device enhances the reliability and lifetime of the battery pack by enabling continuous use during temporary temperature fluctuations, preventing fires or explosions while allowing safe resumption of operation as temperatures normalize.
Implementation Method 1
A positive temperature coefficient (PTC) device is electrically connected in the current path of the battery pack
Data Source
AI summary
A protection circuit for a battery pack is provided in which a positive temperature coefficient device is electrically connected in a current path of the battery pack to control current flowing through the current path in response to an internal temperature of the battery pack. The protection circuit for a battery pack includes a charging and discharging control unit located on a current path of the battery pack. A first protection circuit controls the charging and discharging control unit in response to a charged state of the battery pack. A second protection circuit prevents overcurrent from flowing through the current path of the battery pack. A positive temperature coefficient is electrically connected in the current path of the battery pack. The battery pack may include a bare cell or battery group including one or more secondary batteries.