Battery Pack Temperature Protection Circuit
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Solution Overview
Problem
Existing battery packs lack accurate temperature protection for lithium ion batteries, which can lead to self-heating during discharging, especially when a charging device is connected, due to unreliable temperature detection methods.
Innovation Solution
Incorporating a series circuit of a thermistor and a resistor in parallel with the battery, along with an abnormal temperature detection unit in the protection circuit, which operates a switch to prevent self-heating by detecting temperatures above a predetermined threshold and adjusting the switch state based on voltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermistor is used for temperature detection during charging, then temperature protection function is provided, but temperature detection accuracy deteriorates when charging device voltage varies or divided resistance includes tolerance
Solution Approach 1:
The patent introduces a constant current source as an intermediary element that provides a stable reference current for the temperature detection circuit. This constant current source acts as a mediator between the variable charging voltage and the temperature detection mechanism, ensuring that the thermistor readings remain accurate regardless of voltage fluctuations or resistance tolerances in the charging circuit.
2Reliability
If temperature detection circuit is always active, then temperature protection is continuous, but self-heating of battery occurs during discharging when charging device is connected
Solution Approach 1:
The patent implements a dynamic temperature detection system that automatically adjusts its operation state based on the connection status of the charging device. When the charging device is disconnected, the detection circuit becomes active to monitor battery temperature. When the charging device is connected, the circuit dynamically switches to an inactive state to prevent self-heating, thus adapting its behavior to the operational conditions.
Solution Approach 2:
The system incorporates a feedback mechanism that monitors the connection status of the charging device and uses this information to control the operation of the temperature detection circuit. The feedback signal from the connection detection unit regulates the power supply to the temperature detection circuit, ensuring it operates only when needed and remains inactive when the charging device is connected, thereby preventing self-heating.
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 solution enables accurate temperature protection and prevents self-heating of lithium ion batteries during discharging only when a charging device is connected, ensuring the battery pack's safety and reliability.
Implementation Method 1
a series circuit of a thermistor and a resistor, the series circuit being provided in parallel to the rechargeable battery, the thermistor being thermally connected to the rechargeable battery
Data Source
AI summary
A battery pack including a protection circuit configured to detect over-charge, over-discharge and over-current of a rechargeable battery to turn off a switch element, the switch element provided at a wire provided between the rechargeable battery and a load circuit or a charging device; a series circuit of a thermistor and a resistor, the series circuit provided in parallel to the rechargeable battery, the thermistor thermally connected to the rechargeable battery; and an abnormal temperature detection unit provided in the protection circuit, wherein the abnormal temperature detection unit operates the switch to be in an off state when the temperature of the rechargeable battery is higher than a predetermined temperature, and when a voltage of the wire is higher than a threshold voltage of a forward drop voltage of a body diode in the switch, the abnormal temperature detection unit operates the switch to be in an on state.