Ratio-Metric Signal Path Fault Detection for NTC Wiring Diagnostics
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Solution Overview
Problem
Existing battery management systems (BMS) are unreliable due to electrical faults in the wiring of NTC thermistors and cabling, leading to inaccurate temperature measurements and faulty diagnostics, which can result in undetected battery failures.
Innovation Solution
A fault detection system using a fault detection and auxiliary GPIO multiplexor on semiconductor die within the BMS, which performs sequential test modes to detect faults in the NTC thermistor array, cabling, and BMS by applying fixed currents and measuring voltage deviations to identify shorts or opens in the signal paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NTC thermistor and cabling are used for temperature monitoring, then temperature measurement capability is provided, but electrical faults in wiring cause unreliable monitoring
Solution Approach 1:
The system performs preliminary diagnostic tests by applying test currents through the NTC thermistor circuit before normal operation. The BMS checks for faults such as open circuits, short circuits, and wiring defects by measuring voltage responses during these preliminary tests, ensuring the monitoring system is functional before relying on temperature data
Solution Approach 2:
The patent introduces an intermediary diagnostic circuit that includes test current sources, voltage measurement circuits, and reference resistors. This intermediary system acts as a mediator between the NTC thermistor and the BMS, enabling fault detection by comparing actual voltage readings against expected values calculated from known circuit parameters
2Measurement precision
If fault detection tests are performed on each AUX channel, then accurate fault diagnosis is achieved, but measurement time increases
Solution Approach 1:
The diagnostic system segments the fault detection process into individual channel tests, where each AUX channel is tested separately through dedicated test current sources and measurement circuits. This segmentation allows precise identification of which specific channel has a fault, improving diagnostic accuracy while enabling parallel processing potential
Solution Approach 2:
The system performs diagnostic tests periodically or on-demand rather than continuously. The BMS can initiate diagnostic acquisition modes at scheduled intervals or when triggered by specific conditions, reducing overall measurement time while maintaining adequate monitoring coverage through periodic verification of each channel
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 system effectively detects and diagnoses electrical faults in the NTC thermistor array and cabling, ensuring accurate temperature measurements and reliable battery health monitoring, thereby preventing potential battery failures.
Implementation Method 1
A negative temperature coefficient (NTC) thermistor is typically located in proximity to or in contact with the battery to provide an accurate temperature measurement
Implementation Method 2
The required pull-up test current (AUXnTST) is applied to the AUXn port under test. An ADC measurement of the voltage on AUXn port under test is performed
Data Source
AI summary
A fault detection circuit has multiple inputs adapted for a resistance network, and a current source circuit selectively coupled to the inputs to detect a fault condition. The current source circuit has a first current source, a first switching circuit between the first current source and a first node, a first resistor between the first node and a first input, a second switching circuit between the first input and a power supply conductor, and a third switching circuit between the first node and a second node. The current source circuit further has a second current source, a fourth switching circuit between the second current source and a third node, a second resistor between the third node and a second input, a fifth switching circuit between the second input and the power supply conductor, and a sixth switching circuit between the third node and the second node.