Protective Circuit for Lithium Cell Using Segmented Detectors
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Solution Overview
Problem
Energy-storage devices (ESDs) are vulnerable to damage from adverse conditions such as overcharging, over-discharging, and excessive temperatures, which existing protective circuits do not adequately address, especially for lithium-based batteries operating within specific voltage ranges.
Innovation Solution
A protective circuit that includes p-channel and n-channel FETs, overcharge and overdischarge detectors, and a temperature detector to selectively enable or disable charging and discharging based on detected conditions, ensuring the ESD operates within safe voltage and temperature ranges, thereby preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing protective circuits are used, then some protection is provided, but they do not adequately address damage from overcharging, over-discharging, and excessive temperatures for lithium-based batteries
Solution Approach 1:
The protective circuit is segmented into three independent detection modules: overcharge detector, overdischarge detector, and temperature detector. Each module independently monitors a specific adverse condition and triggers protection when its threshold is exceeded, ensuring comprehensive coverage without interference between protection functions.
Solution Approach 2:
The patent introduces FETs (Field Effect Transistors) as intermediary components between the detectors and the energy-storage device. The FETs act as controllable switches that can rapidly isolate the device from charging or discharging currents when adverse conditions are detected, providing fast protection response while maintaining circuit integrity.
2Speed
If FETs are used in the protective circuit, then fast response to adverse conditions is achieved, but circuit complexity increases
Solution Approach 1:
The FETs are configured to automatically respond to detector signals without requiring external control logic. When the overcharge detector, overdischarge detector, or temperature detector identifies adverse conditions, the FETs self-activate to block current flow, eliminating the need for complex control circuits and microprocessors.
Solution Approach 2:
Multiple protection functions (overcharge protection, overdischarge protection, and temperature protection) are merged into a single integrated circuit architecture. The detectors and FETs work together in a unified structure that provides comprehensive protection while minimizing the overall circuit footprint and component count.
3Reliability
If multiple detectors and FETs are added to provide comprehensive protection, then protection coverage is improved, but device complexity and potential failure points increase
Solution Approach 1:
The protective circuit uses universal components that can handle multiple protection scenarios. The FETs serve as multi-functional switches that can block both charging and discharging currents depending on the detected condition. The detector outputs are designed to control the FETs in a unified manner, reducing the need for separate control circuits for each protection function.
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
Effectively protects ESDs from adverse conditions by preventing overcharging, over-discharging, and temperature-related damage, ensuring the device remains operational within its designated voltage range and maintains safety, even at low voltages.
Implementation Method 1
a p-channel FET adapted and configured to block current flow out of the energy-storage device when a state corresponding to an overcharge state is detected
Implementation Method 2
an n-channel FET adapted and configured to block current flow into the energy-storage device when a state corresponding to an overdischarge state is detected
Implementation Method 3
an overcharge detector having an output adapted and configured to assert a value in a second state when a voltage corresponding to a state other than an overcharge state is detected
Implementation Method 4
an overdischarge detector having an output adapted and configured to assert a value in a first state when a voltage corresponding to a state other than an overdischarge state is detected
Implementation Method 5
a temperature detector circuit adapted and configured to detect a temperature of the energy-storage device
Data Source
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AI summary
A method and apparatus for protecting an energy-storage device (ESD), such as a rechargeable battery, is provided. A protective circuit protects an ESD from adverse charging and loading conditions including overcharging, overdischarging, charging at an excessive rate and discharging at an excessive rate. The protective circuit selectively disables charging and discharging based on the present terminal conditions. A plurality of ESDs and protective circuits can be interconnected to protect a multi-cell ESD device. Embodiments of the protective circuit are adapted to protect a lithium cell operating around 2 volts. The protective circuit may also protect the ESD from adverse temperature conditions.