Battery Voltage Sensing With Digital ADC Error Compensation
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Solution Overview
Problem
Battery management systems face challenges in accurately measuring battery voltages due to voltage drops across external resistances, leading to measurement errors, especially when batteries have varying voltage levels or are bypassed by busbars, which affects the accuracy and safety of battery charging and discharging processes.
Innovation Solution
A digital processor is used to calculate and compensate for error voltages by processing digital signals from ADCs, applying formulas that account for the resistance and capacitance values, and performing calibration routines to determine gain and offset correction voltages, thereby providing accurate measured-voltage output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If external resistances are used for voltage measurement, then current consumption is reduced, but measurement precision deteriorates due to voltage drops
Solution Approach 1:
The patent performs preliminary action by measuring the voltages across adjacent batteries and using these measurements to calculate compensation values before the final voltage measurement. The digital processor calculates error voltages based on adjacent battery voltages and compensates for the voltage drop across external resistances, thereby eliminating the measurement error while maintaining low current consumption.
Solution Approach 2:
The patent implements feedback by using the measured voltages from adjacent batteries to calculate and compensate for the voltage drop in real-time. The digital processor continuously monitors the voltages, calculates the error voltages, and adjusts the measurement results accordingly, creating a closed-loop system that eliminates measurement errors caused by external resistances.
2Measurement precision
If analog compensation circuits are used, then measurement precision is improved, but device complexity and die size increase
Solution Approach 1:
The patent replaces the mechanical/analog compensation circuit with a digital processing system. Instead of using complex analog circuits to compensate for voltage drops, the invention uses a digital processor to calculate error voltages based on digital signals from ADCs and subtract these errors from the measurements. This substitution of digital for analog approaches simplifies the hardware while maintaining measurement precision.
3Measurement precision
If multiple ADCs are used for each battery, then measurement precision is improved, but device complexity and current consumption increase
Solution Approach 1:
The patent merges the measurement functions by using a single ADC per battery and combining the measurements through digital processing. Instead of using multiple ADCs for each battery, the invention measures adjacent batteries with single ADCs and combines these measurements mathematically to achieve the same precision that would require multiple ADCs, thereby reducing current consumption and device complexity.
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
This approach reduces measurement errors to sub-500 μV accuracy, enhancing the reliability and safety of battery management systems by compensating for predictable measurement errors in the digital domain, resulting in lower current consumption and smaller die size, and is scalable across different technologies.
Implementation Method 1
each ADC is configured to convert the difference between the analogue voltages at its first and the second ADC input terminals to a digital signal
Implementation Method 2
a resistance associated with each battery connection terminal
Data Source
AI summary
A battery management system comprising: a sequence of four or more battery connection terminals for connecting to a series of batteries; a resistance associated with each battery connection terminal; and a sequence of three or more ADCs. Each ADC is associated with a pair of the battery connection terminals and is configured to convert the difference between the analogue voltages at its first and the second ADC input terminals to a digital signal, and to provide that digital signal at its ADC output terminal. The battery management system also includes a digital processor that is configured to, for each ADC in the sequence: calculate an error voltage for the ADC based on: i) the digital signal for the preceding ADC in the sequence if there is one; and ii) the digital signal for the next ADC in the sequence if there is one; and provide a measured-voltage output signal by subtracting the error voltage from the digital signal for the ADC.