Battery Protection Circuit for Safe Charger Voltage Gating
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Solution Overview
Problem
Lithium ion batteries are vulnerable to overcharging, which can lead to damage, explosion, or safety hazards due to the lack of effective protection against inappropriate charging voltages, and existing solutions rely on software that may not adequately prevent self-discharge during undervoltage or overvoltage conditions.
Innovation Solution
A battery protection circuit device is designed with a configuration that includes first and second voltage distribution circuits, field effect transistors (FETs), and Zener diodes to control the charging voltage, ensuring it falls within a safe range by selectively turning on/off FETs based on threshold voltages, thereby preventing overcharging and self-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If software-based protection is used to manage battery charging, then the battery management system can control charging processes, but the system may not adequately prevent self-discharge during undervoltage or overvoltage conditions and may wake up unnecessarily
Solution Approach 1:
The patent introduces a hardware-based voltage detection circuit as an intermediary between the battery and the battery management system. This circuit directly monitors charging voltage and generates interrupt signals when voltage thresholds are exceeded, providing reliable protection without requiring the BMS to remain in a high-power active state continuously. The hardware circuit acts as a mediator that handles critical voltage protection independently.
Solution Approach 2:
The protection circuit is designed to autonomously detect voltage conditions and trigger appropriate protection actions without requiring continuous intervention from the battery management system. The hardware circuit self-monitors the charging voltage and automatically generates interrupt signals to the BMS only when threshold violations occur, allowing the BMS to enter low-power sleep modes during normal operation.
2Speed
If the battery management system remains active to monitor charging voltage continuously, then it can respond quickly to overcharging conditions, but the system consumes more power and may cause self-discharge during undervoltage conditions
Solution Approach 1:
The hardware voltage detection circuit performs preliminary voltage monitoring and threshold comparison before the battery management system needs to take action. By pre-detecting voltage conditions and preparing interrupt signals in advance, the system ensures rapid response to overcharging while allowing the BMS to remain in low-power states during normal voltage conditions.
Solution Approach 2:
The patent replaces continuous software-based voltage monitoring with a hardware-based electrical circuit that automatically detects voltage thresholds. This substitution eliminates the need for the BMS to continuously sample and process voltage data, significantly reducing power consumption while maintaining fast response capability through direct electrical threshold detection.
3Reliability
If hardware-based voltage detection is implemented to prevent overcharging, then the system can provide reliable protection, but additional hardware components increase device complexity
Solution Approach 1:
The voltage detection function is merged with the existing battery management system interrupt controller. The hardware detection circuit shares the interrupt controller resource with the BMS, eliminating the need for separate dedicated hardware for each function. This integration approach provides reliable voltage protection while minimizing additional hardware complexity through resource sharing.
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 protects lithium ion batteries by ensuring the charging voltage is within a safe range, preventing damage and ensuring the battery management system only wakes up when the voltage is suitable for charging, thus preventing self-discharge and ensuring safe operation.
Implementation Method 1
a Zener diode connected between the first node and the negative terminal of the charger
Implementation Method 2
a first field effect transistor electrically connected between the battery and the positive terminal of the charger
Data Source
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AI summary
A battery protection circuit (100) device includes: a first voltage distribution circuit (110) that connects to positive (C+) and negative charger terminals (C-), and configured to distribute a charging voltage of the charger; a first FET (130) that connects between a battery (200) and the positive terminal (C+) to receive a charging current from the charger and supply the charging current to the battery (200), the first FET (130) being connected to a first node (n1) of the first voltage distribution circuit (110), and controlled based on a magnitude of the charging voltage; a second voltage distribution circuit (150) that connects to the positive (C+) and negative terminals (C-), and configured to distribute the charging voltage; and a second FET (170) that connects to the positive terminal (C+), the second FET (170) being connected to the first node (n1) and a second node (n2) of the second voltage distribution circuit (150), and turned on or off based on the magnitude of the charging voltage.