DC-DC Converter With Cross-Connected Capacitors for Cell Balancing
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Solution Overview
Problem
Existing DC-DC converters with integrated balancing circuitry face challenges in efficiently performing bi-directional power transfer and cell balancing, particularly in maintaining balanced states of charge across lithium-ion cells with unequal voltages during charging and discharging operations.
Innovation Solution
The system incorporates a DC-DC power conversion circuit with cross-connected capacitors and a balancing circuitry connected between the capacitors, utilizing a transformer with higher excitation impedance to perform bi-directional power transfer and cell balancing, with control circuitry determining the direction of power transfer and aligning the balancing circuitry for balanced or unbalanced operations based on voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DC-DC converter with integrated balancing circuitry is used, then bi-directional power transfer and cell balancing can be conducted, but the device complexity increases
Solution Approach 1:
The patent combines the DC-DC power conversion function and the cell balancing function into a single integrated circuit architecture. The balancing circuitry is merged with the power conversion circuitry, sharing common components such as the transformer, capacitors, and control logic. This integration allows the system to perform both bi-directional power transfer and cell balancing operations without requiring separate dedicated circuits, thereby reducing overall device complexity while maintaining versatility.
Solution Approach 2:
The DC-DC converter circuit is designed with multi-functionality to handle both power conversion and cell balancing operations. The same circuit components (transformer, switches, capacitors) are utilized for both functions depending on the operational mode. The control circuitry can dynamically switch between power transfer mode and balancing mode, making the device universal in its capability to perform multiple functions without requiring separate specialized circuits for each function.
2Productivity
If balancing circuitry is integrated into DC-DC power conversion circuitry, then cell balancing can be performed during charging and discharging, but the difficulty of detecting and measuring voltage differences increases
Solution Approach 1:
The patent employs the transformer as an intermediary element that facilitates both power transfer and voltage comparison for balancing detection. The transformer's isolated winding structure allows the control circuitry to detect voltage differences between cells through the reflected voltages on the primary side during switching operations. This intermediary approach enables voltage difference detection without requiring direct access to each cell's voltage, simplifying the measurement process while maintaining high balancing efficiency during charging and discharging cycles.
3Reliability
If a transformer with higher excitation impedance is used in balancing circuitry, then interference with DC-DC power conversion operations is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by specifying different impedance characteristics for different parts of the transformer structure. The transformer used in the balancing circuitry is designed with locally optimized winding configurations and core materials to achieve higher excitation impedance specifically in the balancing path, while the main power conversion path maintains its standard impedance characteristics. This localized optimization allows the balancing circuitry to operate independently without interfering with DC-DC power conversion, while the manufacturing precision requirements are confined to specific transformer sections rather than the entire device.
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 solution enables efficient bi-directional power transfer and cell balancing, maintaining balanced states of charge across lithium-ion cells, improving the performance and lifetime of battery cells by ensuring voltages remain within allowed limits during charging and discharging.
Implementation Method 1
a first transformer with a first pair of capacitors and a second pair of capacitors cross-connected across the transformer
Implementation Method 2
The second transformer can be activated by an alternating voltage produced between the first pair of capacitors and the second pair of capacitors as power is transferred between a primary side and a secondary side of the DC-DC power conversion circuitry
Data Source
AI summary
A system includes DC-DC power conversion circuitry having a first switch and a second switch on either side of a first transformer with a first pair of capacitors and a second pair of capacitors cross-connected across the transformer. Balancing circuitry includes a primary side of a second transformer connected between the first pair of capacitors and the second pair of capacitors of the DC-DC power conversion circuitry. Control circuitry is configured to determine a direction of power transfer through the DC-DC power conversion circuitry, align a primary side and a secondary side of the DC-DC power conversion circuitry based on the determined direction of power transfer, align the balancing circuitry to perform balanced or unbalanced operations, and control switching of the first switch and the second switch.