Battery Cell Voltage Sensing With Multiplexed ADC Fault Swapping
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Solution Overview
Problem
Existing battery management systems face challenges in accurately measuring battery cell voltages due to electromagnetic interference from vehicle components, which can lead to inaccurate measurements and potential safety issues, particularly in automotive applications.
Innovation Solution
A secondary processing path is implemented using a single ADC multiplexed over cells, combined with a built-in self-test (BIST) to detect faults and enable cell swapping, ensuring accurate UV/OV detection and voltage measurement even in the presence of faults, while minimizing circuit complexity and semiconductor area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single ADC is multiplexed over cells with a secondary processing path, then semiconductor area is reduced and circuit complexity is minimized, but measurement precision and reliability may be compromised due to potential faults
Solution Approach 1:
The system performs built-in self-tests (BIST) before normal measurement operations to detect potential faults in advance. This preliminary action ensures that the ADC and signal processing chains are functioning correctly before being used for actual voltage measurements, thereby maintaining measurement precision while using a single multiplexed ADC
Solution Approach 2:
The system implements redundant signal processing paths and fault detection mechanisms that are prepared in advance. When a fault is detected in the primary path, the system can switch to alternative processing routes or compensation methods, cushioning against the potential loss of measurement precision that would otherwise occur with a single ADC
2Measurement precision
If differential voltage amplifiers with high CMRR are placed at each cell, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple measurement functions into a single ADC through multiplexing. Instead of placing separate amplifiers and ADCs at each cell, the system uses one ADC that sequentially measures multiple cells, reducing the number of components while maintaining measurement precision through careful signal conditioning and switching design
Solution Approach 2:
The single ADC is designed to perform multiple measurement functions across different cells and potentially different measurement modes. This universal component replaces what would traditionally require multiple dedicated ADCs and amplifiers, reducing device complexity while maintaining the precision needed for battery management
3Reliability
If built-in self-test is implemented to detect faults, then reliability is improved, but device complexity increases
Solution Approach 1:
The system implements self-diagnostic capabilities where the ADC and signal processing chains test themselves automatically through built-in self-test (BIST) circuits. These circuits generate test signals and monitor the response to detect faults without requiring external testing equipment, improving reliability while adding minimal complexity compared to external test systems
Solution Approach 2:
The fault detection and self-test circuits are integrated within the existing ADC and signal processing structure. Rather than adding separate external monitoring systems, the BIST functionality is nested within the operational circuits, allowing fault detection capabilities to be embedded without significantly increasing overall device complexity
Data Source
AI summary
A method can be used to control a battery management system. A first voltage drop is sensed between a first terminal of a first battery cell and a second terminal of the first battery cell and a second voltage drop is sensed between a first terminal of a second battery cell and a second terminal of the second battery cell. A faulty condition is detected in the first battery cell or the second battery cell based on the first voltage drop or the second voltage drop. The first voltage drop is swapped for a first swapped voltage drop between a common terminal and the second terminal of the second battery cell.