Dual-Mode Coulomb Counter Offset Correction for Accurate SOC
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Solution Overview
Problem
Coulomb counter circuitry in battery management systems faces inaccuracies due to offset errors in analog-to-digital converter (ADC) circuitry, leading to unreliable state of charge (SOC) estimates, and existing calibration methods are time-consuming and costly.
Innovation Solution
The implementation of a dual-mode coulomb counter circuitry with offset correction and calibration capabilities, utilizing higher resolution ADC circuitry and offset correction factors to enhance accuracy and reduce calibration time, includes delta-sigma and successive approximation register (SAR) ADCs, sample and hold circuits, and multiplier circuits to generate and apply offset correction signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ADC circuitry is used in coulomb counter, then device complexity is reduced, but measurement precision deteriorates due to offset errors
Solution Approach 1:
A second ADC circuitry with higher resolution is introduced as an intermediary component to measure offset errors. This additional ADC acts as a mediator that captures the offset error signal, which is then processed through offset correction circuitry to generate correction factors that compensate for errors in the primary ADC, thereby improving SOC estimation accuracy without requiring complete redesign of the main measurement path.
Solution Approach 2:
The ADC measurement function is segmented into two separate ADC circuitries: a first ADC for normal coulomb counting operations and a second ADC specifically for offset error measurement and correction. This segmentation allows each ADC to be optimized for its specific function, with the second ADC providing high-resolution offset measurements that improve overall measurement precision without burdening the primary measurement path.
2Manufacturing precision
If traditional calibration methods are applied, then manufacturing precision is improved, but productivity deteriorates due to time-consuming calibration process
Solution Approach 1:
The system performs self-calibration by automatically measuring its own offset errors using the second ADC and generating correction factors through offset correction circuitry. This self-service calibration approach eliminates the need for external calibration equipment and manual adjustment procedures, significantly reducing calibration time while maintaining high precision through automated error measurement and compensation.
Solution Approach 2:
Offset correction factors are pre-calculated and stored in memory before normal operation begins. The system performs preliminary offset measurement and correction factor generation during initialization or calibration mode, so that during subsequent coulomb counting operations, the pre-computed correction factors are readily available for immediate application, avoiding time-consuming real-time calibration.
3Measurement precision
If higher resolution ADC circuitry is added for offset correction, then measurement precision improves, but device complexity increases
Solution Approach 1:
The second ADC circuitry is specifically optimized for the local function of offset error measurement, utilizing higher resolution only where needed for accurate offset detection. The first ADC maintains its original resolution appropriate for normal coulomb counting. This localized application of high resolution avoids unnecessary complexity in the entire system while achieving precise offset measurements where required.
Data Source
AI summary
Coulomb counter circuitry operable in a first mode of operation and a second mode of operation, the coulomb counter circuitry comprising: first analog to digital converter (ADC) circuitry configured to generate a first ADC output signal indicative of a current through a load coupled to the coulomb counter circuitry; second analog to digital converter (ADC) circuitry; offset correction circuitry; and accumulator circuitry configured to generate a signal indicative of a cumulative amount of charge transferred to the load, wherein in the second mode of operation, the coulomb counter circuitry is operable to enable the second ADC circuitry and to generate an offset correction factor based at least in part on a second ADC output signal output by the second ADC circuitry, and wherein in subsequent operation of the coulomb counter circuitry in the first mode of operation, the offset correction circuitry applies the offset correction factor to the first ADC output signal.