Insulation Detection Circuit for Battery Management Systems
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Solution Overview
Problem
Current insulation detection methods for battery packs, such as AC injection and voltage division, cannot effectively detect insulation impedance on the load side when the positive or negative switch modules are not closed, leading to potential damage to the controller and risk of short circuits, which can compromise the safety of electric vehicles.
Innovation Solution
An insulation detection circuit comprising an isolated power module, sampling modules, and a processor that can detect insulation resistance values on both the battery pack and load sides, even when the switch modules are in the OFF state, by forming loops with the isolated power module and equivalent impedance of the load device, allowing for continuous monitoring and early warning of insulation faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC injection method or voltage division method is used for insulation detection, then insulation impedance on battery pack side can be detected, but insulation impedance on load side cannot be detected when switch modules are not closed
Solution Approach 1:
The detection circuit is segmented into two independent detection paths: one for detecting insulation impedance on the battery pack side (when switches are open) and another for detecting insulation impedance on the load side (when switches are closed). Each path uses appropriate detection methods tailored to its specific detection target, enabling comprehensive coverage under different switch states.
Solution Approach 2:
The detection circuit is designed with multi-functionality to handle different detection scenarios. It can detect insulation impedance on both the battery pack side and load side, and can operate effectively whether the switch modules are closed or open, making it universally applicable across all operational states.
2Measurement precision
If insulation detection is only performed when switch modules are closed, then load side insulation can be detected, but battery pack side insulation cannot be detected and controller may be damaged
Solution Approach 1:
The detection circuit performs preliminary detection of insulation impedance on the battery pack side before the switch modules are closed. This preliminary action identifies potential insulation faults early, preventing them from causing controller damage or short circuits when the switches are subsequently closed.
Solution Approach 2:
The detection circuit continuously monitors insulation impedance on both battery pack side and load side, providing real-time feedback about insulation status. This feedback mechanism enables early warning of insulation faults, allowing the system to take preventive actions before faults escalate into dangerous conditions.
3Power
If high voltage is used for large power output, then power output is sufficient, but insulation failure may introduce high voltage into passenger compartment
Solution Approach 1:
The detection circuit provides continuous feedback about insulation impedance on the battery pack side, enabling real-time monitoring of insulation status. When insulation degradation is detected, the system can issue early warnings or take protective actions to prevent high voltage from intruding into the passenger compartment, thus mitigating the harmful effects of high voltage usage.
4Power
If large current is used for large power output, then power output is sufficient, but line loss increases and temperature rises quickly
Solution Approach 1:
The detection circuit performs preliminary detection of insulation impedance before high current operation begins. By identifying insulation faults early, the system can prevent faulty conditions from exacerbating during high current operation, thereby reducing the risk of excessive temperature rise and heat dissipation problems.
Data Source
AI summary
The present disclosure provides an insulation detection circuit, a detection method and a battery management system. The insulation detection circuit includes an isolated power module, first positive and negative sampling modules, second positive and negative sampling modules, and a processor. A first end of the second positive sampling module is connected to a positive electrode of the isolated power module and a second end of the positive switch module, a second end of the second positive sampling module is connected to a second reference voltage terminal; a first end of the second negative sampling module is connected to the second reference voltage terminal, a second end of the second negative sampling module is respectively connected to a negative electrode of the isolated power module and a second end of the negative switch module; and the processor is connected to sampling points.