Dual-Input BMS ADC Architecture for Redundant Cell Voltage Sensing
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Solution Overview
Problem
The high cost and large die area requirement for providing fully redundant measurements in Battery Management Systems (BMS) to meet the ASIL D standard, particularly when monitoring a large number of battery cells, due to the need for duplicate Analog-to-Digital Converters (ADCs).
Innovation Solution
A dual-input Analog Front-End for BMS with shared digital converter circuit and redundant switched capacitor circuits for primary and secondary cell voltage measurements, along with a diagnostic reference circuit to verify functionality, reducing die area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fully redundant ADCs are provided to meet ASIL D standard, then measurement reliability is improved, but die area and cost increase
Solution Approach 1:
The patent merges two separate ADC functions (primary measurement and secondary balancing measurements) into a single ADC by time-division multiplexing. The ADC alternates between sampling from the primary input terminals during charging/discharging operations and sampling from the secondary input terminals during balancing operations, eliminating the need for duplicate ADC hardware while maintaining ASIL D redundancy requirements.
Solution Approach 2:
The single ADC is designed to perform multiple functions: it can measure primary cell voltages during charging and discharging, measure secondary cell voltages during balancing operations, and interface with both primary and secondary input terminals. This multi-functional design replaces what would traditionally require separate dedicated ADCs for each function.
2Reliability
If fully redundant ADCs are provided to meet ASIL D standard, then measurement reliability is improved, but power consumption increases
Solution Approach 1:
The patent combines the power consumption of what would be two separate ADCs into a single ADC operating in time-division mode. By alternating between primary and secondary measurement functions rather than running parallel ADCs continuously, the system achieves the same reliability with reduced total power consumption.
3Reliability
If duplicate ADCs are provided for each battery cell, then measurement redundancy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple measurement functions into a single ADC with time-division multiplexing, reducing the number of independent ADC circuits from two per cell to one per cell. This simplifies the overall device architecture while maintaining the required measurement redundancy through alternating sampling modes.
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
Meets the ASIL D standard with reduced die area and power consumption by providing fully redundant cell voltage measurements while optimizing semiconductor die area and power usage.
Implementation Method 1
a first switched capacitor circuit comprising first and second primary input terminals for connecting to respective primary measurement pins of a battery cell, wherein the first switched capacitor circuit is configured to sample a primary cell voltage
Data Source
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AI summary
A battery management system comprising: a plurality of analog-to-digital converters, ADCs, each ADC comprising: a first switched capacitor circuit comprising first and second primary input terminals for connecting to respective primary measurement pins of a battery cell, wherein the first switched capacitor circuit is configured to sample a primary cell voltage across the first and second primary input terminals; a second switched capacitor circuit comprising first and second secondary input terminals for connecting to respective cell balancing pins of the battery cell wherein the second switched capacitor circuit is configured to sample a secondary cell voltage across the first and second secondary input terminals; a digital conversion circuit for providing a digital measurement of an input voltage; a diagnostic reference circuit configured to provide a diagnostic reference voltage for testing the function of the digital converter circuit; and a selection circuit configured to selectively connect the digital converter circuit to one or more of: the first switched capacitor circuit, the second switched capacitor circuit and the diagnostic reference circuit.