Self-test Circuit for Battery Management Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing battery management systems (BMS) in electric and hybrid electric vehicles face challenges in accurately measuring differential voltages from high common mode voltages, particularly in noisy automotive environments, which can affect battery pack longevity and performance, and current solutions for built-in self-test (BIST) are limited in their ability to check the full range of input voltages.
Innovation Solution
A circuit architecture that includes a multiplexer with switchable inputs and a differential voltage level shift stage, coupled with a sigma-delta analog-to-digital converter, allows for the generation of a low-voltage BIST signal and emulation of input differential voltages, enabling high-accuracy voltage conversion and full-range testing of the processing chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Zener-based BIST solutions are used, then circuit area is reduced, but measurement precision and testing capability are limited
Solution Approach 1:
The patent introduces a low-voltage signal generator as an intermediary component that produces test signals independent of the high-voltage battery system. This mediator enables accurate BIST measurements without requiring high-voltage Zener diodes, thus improving measurement precision while avoiding the area and complexity of conventional high-voltage test circuitry.
Solution Approach 2:
The patent replaces the conventional Zener diode-based high-voltage test signal generation with an electronic low-voltage signal generation system. This substitution eliminates the need for high-voltage breakdown mechanisms and replaces them with precision electronic signal synthesis, improving both accuracy and reducing circuit area.
2Measurement precision
If high common mode voltages are measured directly, then battery cell voltage measurement is achieved, but measurement precision deteriorates due to noisy automotive environment
Solution Approach 1:
The patent extracts the differential voltage signal from the high common mode voltage environment by using instrumentation amplifiers that reject common mode signals. This extraction process isolates the small differential voltage component from the large common mode voltage, improving measurement precision while filtering out electromagnetic interference.
Solution Approach 2:
The patent introduces instrumentation amplifiers with high CMRR as intermediary devices between the battery cells and the measurement system. These amplifiers act as mediators that selectively amplify the differential voltage while rejecting the common mode voltage and associated electromagnetic interference, thus improving measurement accuracy in noisy environments.
3Adaptability or versatility
If built-in self-test is implemented with limited input voltage range, then device complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The patent implements a universal low-voltage signal generator that can produce multiple test signal levels and configurations through software control. This multi-functional generator replaces multiple dedicated test circuits, enabling comprehensive BIST coverage across different input voltage ranges while actually reducing overall device complexity through integration.
Solution Approach 2:
The patent employs dynamically configurable test signal generation where the signal characteristics can be adjusted in real-time based on the specific testing requirements. This dynamic adaptability allows the same circuit to handle various input voltage ranges and test scenarios, improving versatility without requiring separate fixed circuits for each case.
Data Source
AI summary
A circuit includes a differential stage configured to provide a differential output signal. An analog-to-digital converter is coupled to first and second output nodes of the differential stage. The analog-to-digital converter is configured to provide an output signal that is a function of the differential output signal from the differential stage. A multiplexer is configured to receive a differential input signal. The multiplexer includes a test switch switchable between a conductive state and a non-conductive state. In the conductive state, the test switch couples the first input node and the second input node of the differential stage. Test signal injection circuitry is activatable to force a differential current through the differential stage. The circuit is selectively switchable between an operational mode and a self-test mode.