Battery Protecting Circuit Disconnection Detection
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Solution Overview
Problem
Existing battery protecting circuits fail to accurately monitor cell voltages when the line between a lithium-ion secondary battery and a monitoring terminal is disconnected, leading to potential undetected abnormal states such as overcharge or overdischarge.
Innovation Solution
A battery protecting circuit with a disconnection detecting circuit that shifts the electric potential of monitoring terminals and uses a latching circuit to retain detection results, ensuring accurate disconnection detection even with unstable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current circuit is used to pull up or down the monitoring terminal to detect disconnection, then the disconnection detection function is provided, but the electric potential of the monitoring terminal becomes unstable when disconnection occurs, leading to potential false operations
Solution Approach 1:
The patent applies preliminary action by pre-charging a capacitor through a current limiting resistor before disconnection detection. When disconnection occurs, the capacitor maintains the electric potential of the monitoring terminal at a stable level, preventing false operations. The capacitor is charged in advance through the resistor, and upon disconnection, it holds the potential stable for a predetermined period, allowing accurate detection without potential fluctuations.
Solution Approach 2:
The patent implements beforehand cushioning by using a capacitor to cushion the electric potential changes at the monitoring terminal when disconnection occurs. The capacitor absorbs the sudden potential changes that would otherwise cause instability, providing a缓冲 (buffering) effect that maintains stable potential during the detection period.
2Reliability
If the monitoring terminal electric potential is shifted using a constant current circuit, then disconnection can be detected, but the detection circuit becomes more complex
Solution Approach 1:
The patent uses a simple RC circuit (resistor-capacitor) to replicate the effect of complex constant current circuits for potential shifting. Instead of using dedicated constant current sources, the invention uses the natural charging and discharging characteristics of the RC circuit to achieve the same disconnection detection functionality with fewer and simpler components.
Solution Approach 2:
The monitoring terminal's capacitor serves itself by automatically maintaining the electric potential after being charged through the current limiting resistor. The capacitor inherently performs the potential stabilization function without requiring additional active control circuits, making the system self-regulating and simpler.
Data Source
AI summary
A disclosed battery protecting circuit for protecting a secondary battery including at least first and second cells connected in series includes a first terminal connected on a high potential side of the first cell; a second terminal connected on a low potential side of the first cell and a high potential side of the second cell; a third terminal connected on a low potential side of the second cell; a charge abnormality detecting circuit detecting abnormality of the charged state of the secondary battery; a shifting circuit shifting electric potential of the second terminal on a side of the first terminal or a third terminal when a disconnection occurs between the secondary battery and the second terminal; a disconnection detecting circuit detecting the disconnection based on the electric potential of the second terminal; and a latching circuit retaining a result detected by the disconnection detecting circuit.