Battery Monitoring Circuit for Correcting Cell Voltage Drop
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Solution Overview
Problem
Existing battery monitoring devices face significant measurement errors due to voltage drops across resistor elements in low-pass filters during cell voltage measurement, which are not tolerable in modern vehicle-mounted systems, and accurately measuring these resistor values is challenging.
Innovation Solution
The battery monitoring device incorporates cell selection switches with a first, second, and third switch part, along with a resistor element, allowing for the derivation of resistance values by acquiring specific digital values under controlled switch states, enabling the calculation of accurate cell voltages by removing voltage drop components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filter with a resistor element is connected between the battery monitoring device and each battery cell to remove noise during cell voltage measurement, then noise is removed, but a voltage drop occurs in the resistor element causing significant measurement error
Solution Approach 1:
The patent extracts the harmful voltage drop component from the measurement signal by separately measuring it through the cell selection switch and then removing it from the total measurement value, leaving only the accurate cell voltage
Solution Approach 2:
The patent introduces the cell selection switch as an intermediary component that allows separate measurement of the voltage drop across the resistor element, enabling the distinction between the voltage drop and the actual cell voltage
2Measurement precision
If the resistance value of the resistor element is measured to calculate and remove the voltage drop component, then measurement accuracy is improved, but the complexity of the device increases
Solution Approach 1:
The cell selection switch performs multiple functions: it selects battery cells for voltage measurement and simultaneously enables measurement of the voltage drop across the resistor element, eliminating the need for separate measurement circuits
Solution Approach 2:
The existing cell selection switch and resistor element are utilized for dual purposes - the switch not only selects cells but also enables self-measurement of the voltage drop that affects the measurement accuracy
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 allows for precise measurement of resistance values and subsequent accurate cell voltage determination, effectively mitigating measurement errors and enhancing the reliability of battery monitoring in vehicle applications.
Implementation Method 1
a low-pass filter composed of a resistor element and a capacitor is connected between the battery monitoring device and each battery cell to remove noise that is mixed in during cell voltage measurement
Data Source
AI summary
A battery monitoring device includes an analog-digital converter and a plurality of cell selection switches that selectively connect any of battery cells to the analog-digital converter. Each of the cell selection switches includes a first switch part, a second switch part, a third switch part, and a resistor element. The first switch part is provided on a conduction path leading from one of the battery cells to the analog-digital converter, brings the conduction path into a conductive state in an on-state of the first switch part, and brings the conduction path into a non-conductive state in an off-state of the first switch part. The second switch part switches on and off of the first switch part. The third switch part switches a magnitude of a current flowing into the first switch part when the first switch part is in the on-state. The resistor element is provided on the conduction path.