Battery Pack Voltage Sensing with Flying Capacitor
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Solution Overview
Problem
Conventional battery packs with limited input ports on voltage sensing and balancing circuits cannot accommodate all battery cells, leading to incomplete voltage detection, especially due to temperature-dependent voltage differences across diodes.
Innovation Solution
Incorporating a first diode in a backward direction from a flying capacitor coupled to an analog-to-digital converter, along with a second diode packaged as a single set, to store battery cell voltage values and prevent surge currents, thereby compensating for temperature-dependent voltage differences and allowing detection of all battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a limited number of input ports are used in the voltage sensing and balancing circuit, then the device complexity is reduced, but the measurement precision deteriorates because not all battery cell voltages can be detected
Solution Approach 1:
The battery cells are divided into two groups: those directly connected to the voltage sensing and balancing circuit input ports, and those connected through the flying capacitor. This segmentation allows the limited input ports to be used efficiently while still enabling voltage detection for all battery cells through the capacitor-based indirect measurement path.
Solution Approach 2:
The flying capacitor acts as an intermediary element that transfers voltage information from battery cells that cannot be directly connected to the sensing circuit. The capacitor stores and transfers voltage signals, enabling indirect measurement of battery cell voltages without requiring additional input ports on the voltage sensing and balancing circuit.
2Ease of manufacture
If diodes with different temperature characteristics are used in the voltage input path, then the ease of manufacture is improved, but the measurement precision deteriorates due to temperature-dependent voltage differences
Solution Approach 1:
The diodes are strategically positioned at specific locations within the circuit where they can compensate for temperature-dependent voltage drops. By placing diodes in the voltage input path from the flying capacitor to the A/D converter, the circuit locally compensates for temperature effects, ensuring that voltage measurements remain accurate across varying temperature conditions.
Solution Approach 2:
The circuit utilizes the temperature characteristics of diodes to compensate for temperature-dependent voltage variations. By selecting diodes with specific forward voltage temperature coefficients and positioning them appropriately, the circuit automatically adjusts for temperature changes, maintaining measurement precision without requiring complex temperature compensation circuits.
3Productivity
If the flying capacitor is directly connected to the A/D converter without protection, then the productivity is improved by simplifying the circuit, but the reliability deteriorates due to surge current from voltage supply
Solution Approach 1:
Protective diodes are placed in the voltage input path from the flying capacitor to the A/D converter to prevent surge currents before they can damage the converter. These diodes act as protective elements that clamp voltage spikes and prevent reverse current flow, ensuring the reliability of the A/D converter while maintaining the fast charging and discharging performance of the battery pack.
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
Enables complete voltage detection across all battery cells, including those beyond the limited input ports, by stabilizing voltage measurements and preventing surge currents, thus enhancing the accuracy and efficiency of battery management.
Implementation Method 1
a first diode coupled in a backward direction from a flying capacitor, which is coupled to an analog-to-digital (A/D) converter
Implementation Method 2
a diode formed in a backward direction to correspond to another diode packaged therewith as one single set, the diode preventing surge current from a voltage supply in a voltage input path from a flying capacitor to an A/D converter
Data Source
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AI summary
A battery pack is provided, which can compensate for temperature dependence of voltages measured from a battery cell and applying the same to an analog-to-digital converter. In an embodiment, the battery pack, a diode is formed in a backward direction from a flying capacitor to an A/D converter to correspond to a diode packaged therewith as one single set, the diode positioned in a battery cell voltage input path to store battery cell voltage values in the flying capacitor, thereby suppressing a difference between voltages measured from battery cells.