Battery Cell Balancing Using a DC-DC Converter Input Capacitor
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Solution Overview
Problem
The imbalance in the state of charge between battery cells in a battery pack due to repeated charging and discharging leads to reduced usable capacity and accelerated deterioration, which existing technologies have not effectively addressed.
Innovation Solution
A battery system with a switching circuit that performs cell balancing operations in different modes based on load current, using a DC-DC converter and input capacitor to alternately connect battery cells and adjust their states of charge, thereby maintaining balanced power supply to the system load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery cells are used to increase power capacity, then the power supply capability is improved, but charge imbalance occurs between cells leading to reduced usable capacity and accelerated deterioration
Solution Approach 1:
The battery system performs self-balancing by utilizing the input capacitor of the DC-DC converter to transfer charge between battery cells. The control unit automatically detects charge imbalances and activates the switching circuit to equalize charges without requiring external balancing equipment, enabling the system to self-correct charge distribution issues that arise during repeated charging and discharging cycles.
2Duration of action of stationary object
If cell balancing operation is performed to maintain charge balance, then the lifespan and usable capacity are improved, but additional balancing circuits and increased system complexity are required
Solution Approach 1:
The input capacitor of the DC-DC converter serves dual functions: it acts as the energy storage component for the power conversion circuit and simultaneously serves as the charge transfer medium for cell balancing operations. The switching circuit, already necessary for DC-DC conversion, is configured to perform both power conversion switching and cell balancing switching, eliminating the need for separate balancing circuits and reducing overall system complexity.
3Reliability
If external balancing circuits are added to address charge imbalance, then the charge balance is improved, but the integration and cost-effectiveness are reduced
Solution Approach 1:
The patent merges the cell balancing function with the existing DC-DC power conversion system by utilizing the input capacitor and switching circuit for dual purposes. The control unit integrates charge balance monitoring with power management functions, and the switching circuit handles both power conversion and charge equalization tasks, thereby eliminating the need for separate external balancing circuits and reducing manufacturing costs and system integration 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 extends the lifespan of battery cells by maintaining balanced charge states, increasing usable capacity and reducing deterioration without the need for external balancing circuits, thus enhancing the integration and cost-effectiveness of the battery system.
Implementation Method 1
a direct current (DC)-direct current (DC) converter including an input capacitor connected to the first and second output terminals
Data Source
AI summary
A battery system configured to provide power to a load based on a load current includes a first battery cell selectively connected to a first output terminal and a second output terminal and having a first state of charge, a second battery cell selectively connected to the first output terminal and the second output terminal and having a second state of charge indicating a lower charge level than the first state of charge, a direct current (DC)-direct current (DC) converter including an input capacitor connected to the first and second output terminals, and a switching circuit configured to perform a first cell balancing operation or a second cell balancing operation based on a magnitude of the load current, the first cell balancing operation including alternately connecting the input capacitor to the first battery cell or the second battery cell, and the second cell balancing operation including connecting the input capacitor to the first battery cell, based on a magnitude of the load current.