Transformer-Based Cell Balancing Circuit for Battery Packs
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Solution Overview
Problem
In multi-cell battery packs, voltage imbalances due to cell aging and temperature differences lead to reduced battery life, and traditional cell balancing methods induce significant thermal energy dissipation, particularly in electric vehicle applications.
Innovation Solution
A cell balancing circuit utilizing a transformer and switching controller to transfer energy from cells with higher voltages to those with lower voltages, maintaining voltage balance while minimizing thermal dissipation through a controlled PWM signal and constant charging current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional cell balancing methods discharge cells with high voltage by connecting external loads, then voltage balance between cells is achieved, but significant thermal energy dissipation occurs
Solution Approach 1:
The patent introduces a transformer as an intermediary device to transfer energy between battery cells. The transformer couples cells with high voltage to cells with low voltage through electromagnetic induction, enabling energy transfer without direct resistive connection. This mediator approach eliminates the need for dissipative external loads while achieving cell balancing.
Solution Approach 2:
The patent replaces the traditional mechanical/electrical resistive balancing system with an electromagnetic field-based transformer system. Instead of using resistors to dissipate energy as heat, the invention uses electromagnetic induction to transfer energy from high-voltage cells to low-voltage cells, substituting a lossy mechanical/electrical system with a more efficient electromagnetic coupling system.
2Duration of action of stationary object
If cell voltage imbalance increases with charging/discharging cycles, then battery life is shortened, but implementing cell balancing increases system complexity
Solution Approach 1:
The transformer-based balancing circuit can serve multiple functions: it can balance cells during charging, during discharging, and can adapt to different cell configurations (series or parallel connections). The same basic transformer topology can be applied to various battery pack arrangements, reducing overall system complexity compared to dedicated balancing circuits for each scenario.
Solution Approach 2:
The patent combines the cell balancing function with the existing battery management system infrastructure. The transformer is integrated into the battery pack's electrical architecture, and the control system uses the same monitoring and control electronics already present for charge/discharge management. This merging approach avoids adding completely separate balancing hardware.
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 effectively balances battery cell voltages, reduces thermal energy dissipation, and extends battery life by actively managing energy distribution within the battery pack.
Implementation Method 1
The transformer has a primary winding and a secondary winding... controls energy from the first cell to the primary winding so as to transfer the energy from the first cell to the second cell
Data Source
AI summary
A cell balancing circuit for balancing battery cells includes a transformer and a switching controller. The transformer has a primary winding and a secondary winding. The switching controller can select a first cell coupled to the primary winding and select a second cell coupled to the secondary winding. The first cell and the second cell are coupled in series. The first cell has a cell voltage that is greater than the second cell. The cell balancing circuit further includes a controller coupled to the primary winding. The controller controls energy from the first cell to the primary winding so as to transfer the energy from the first cell to the second cell to balance the battery cells.