Voltage Detection Device with Lowpass Filter Failure Analysis
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Solution Overview
Problem
Conventional voltage detection devices in battery assemblies, particularly in hybrid and electric vehicles, fail to accurately detect lowpass filter failures, especially gradual leaks, which can lead to inefficiencies and overcharging due to the inability to distinguish between filter degradation and battery degradation.
Innovation Solution
A voltage detection device comprising lowpass filters, first and second voltage detectors, and a failure detector that compares detection values from both paths to identify lowpass filter failures, with a switching unit to input voltage to a single Analog-to-Digital converter, and equalization switches connected to discharge resistors for precise voltage detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lowpass filter is provided between each unit battery and the associated Analog-to-Digital converter to cut high-frequency noise, then voltage detection accuracy is improved, but the ability to detect filter failures (especially gradual leaks) deteriorates
Solution Approach 1:
The voltage detection function is segmented into two separate detection paths: one path includes the lowpass filter for normal voltage detection, while the other path bypasses the filter for failure detection. This segmentation allows each path to serve its specific purpose without interfering with the other, enabling both accurate voltage measurement and reliable filter failure detection.
Solution Approach 2:
A switching unit is introduced as an intermediary component that controls the connection between the unit battery and the Analog-to-Digital converter. The switching unit enables selective connection to either the filtered path or the bypass path, allowing the system to switch between normal operation mode and failure detection mode as needed.
2Device complexity
If a single Analog-to-Digital converter is used with a switching unit to detect both filtered and unfiltered voltages, then device complexity and cost are reduced, but the reliability of failure detection may be compromised
Solution Approach 1:
The single Analog-to-Digital converter is designed to perform multiple functions: it detects voltages through the lowpass filter during normal operation and detects voltages through the bypass path for failure detection. This multi-functionality reduces the need for separate detection circuits while maintaining the reliability of failure detection through the switching mechanism.
Solution Approach 2:
The switching unit serves as an intermediary that protects the reliability of failure detection by ensuring clean separation between the filtered and unfiltered signal paths. It prevents interference between the two detection modes and ensures that the bypass path remains isolated from the filter circuitry, maintaining detection accuracy.
3Difficulty of detecting and measuring
If the output voltage of the lowpass filter is monitored to detect failures, then disconnection failures can be detected, but gradual leak failures of capacitors cannot be distinguished from battery degradation
Solution Approach 1:
The detection system is segmented into two independent measurement channels: one channel measures voltage through the lowpass filter to detect disconnection failures, while the other channel measures voltage through the bypass path to detect gradual leak failures. By comparing results from both channels, the system can accurately distinguish between different failure modes.
Solution Approach 2:
The system uses feedback comparison between the filtered voltage detection results and the unfiltered voltage detection results to identify filter failures. When a discrepancy exceeds a threshold, the system determines that a filter failure has occurred, providing accurate detection of both disconnection and gradual leak failures.
Data Source
AI summary
A voltage detection device for detecting a voltage across both ends of each of plural unit batteries which are connected to each other in series. The voltage detection device includes lowpass filters which are connected to the respective unit batteries, a first voltage detector which detects a voltage across both ends of each of the unit batteries that is supplied via a corresponding lowpass filter, a second voltage detector which detects a voltage across both ends of each of the unit batteries that is supplied without passage through the corresponding lowpass filter, and a failure detector which detects whether the lowpass filter is failing by comparing a voltage detection value detected by the first voltage detector with a voltage detection value detected by the second voltage detector.