Overcurrent Protection Circuit Dynamic Resistor Switching
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Solution Overview
Problem
Conventional overcurrent protection circuits for rechargeable batteries suffer from high leakage currents, which reduce the battery's service life due to the large resistance of the overcurrent return resistor, and increasing this resistance further complicates the detection of discharge overcurrent states.
Innovation Solution
The overcurrent protection circuit employs a dual overcurrent return resistor configuration with different resistances that adjust based on the voltage level at the current detection terminal, using a NAND gate and switching elements to selectively connect either a low or high resistance path, thereby minimizing leakage current during overcurrent detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single high resistance overcurrent return resistor is used, then leakage current is reduced, but discharge overcurrent detection accuracy deteriorates
Solution Approach 1:
The patent applies the dynamics principle by making the overcurrent return resistance dynamically adjustable based on the detected voltage level. When voltage exceeds a first threshold, a first resistance value is applied; when voltage exceeds a second threshold, a second resistance value is applied. This dynamic adjustment allows the system to optimize between leakage current reduction and detection accuracy under different operating conditions.
Solution Approach 2:
The patent implements parameter changes by varying the resistance value of the overcurrent return resistor based on the detected voltage level. The resistance parameter is changed from a first resistance value to a second resistance value depending on whether the voltage exceeds the first or second threshold, enabling adaptive optimization of system performance.
2Measurement precision
If a single low resistance overcurrent return resistor is used, then discharge overcurrent detection accuracy is improved, but leakage current increases
Solution Approach 1:
The system dynamically switches between different resistance values based on the detected voltage level. During normal operation with lower voltage, a higher resistance value is used to minimize leakage current. When overcurrent conditions cause voltage to exceed thresholds, appropriate resistance values are selected to maintain detection accuracy while managing leakage.
Solution Approach 2:
The resistance parameter of the overcurrent return resistor is changed based on operating conditions. By switching between first and second resistance values according to voltage thresholds, the system adapts to different operational states, optimizing the balance between detection accuracy and energy loss.
3Measurement precision
If multiple overcurrent return resistors with different resistances are used, then both leakage current reduction and detection accuracy are improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the overcurrent return path into multiple segments with different resistance values. Instead of using a single resistor, the system employs first and second overcurrent return resistors with different resistance values, each optimized for specific operating conditions, thereby improving overall system performance.
Solution Approach 2:
The multiple overcurrent return resistors serve different functions under different operating conditions. The first resistor optimizes for normal operation with minimal leakage, while the second resistor optimizes for overcurrent detection accuracy. This multi-functionality allows a single resistor network to handle multiple operational requirements.
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 approach significantly reduces leakage current, extending the service life of the rechargeable battery by dynamically adjusting the overcurrent return resistor resistance according to the detected voltage level, ensuring accurate overcurrent detection and protection.
Implementation Method 1
when a load RL is connected to the battery pack 300 and a discharge current Id flows, a potential Vd at the current detection terminal V− is acquired as Vd=Id×Ron
Implementation Method 2
an overcurrent return resistance RS5 having a resistance of about several tens [kΩ] to several hundreds of [kΩ]
Data Source
AI summary
An overcurrent protection circuit of a rechargeable battery includes a current detection terminal and an overcurrent return resistor connecting part. A voltage converted from a discharge current of the rechargeable battery is detected at the current detection terminal. The overcurrent return resistor connecting part connects the current detection terminal to overcurrent detection resistors having different resistances in accordance with a level of the voltage detected at the current detection terminal when the voltage detected at the current detection terminal is equal to or greater than a discharge overcurrent detection voltage and a discharge overcurrent state in which an overcurrent flows from the rechargeable battery is detected.