Transformer Cell Balancing Circuit for Higher Current at Lower Cost
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Solution Overview
Problem
Existing cell balancing circuits face challenges in reducing the number of components and unit costs due to the complexity and cost associated with active cell balancing circuits, and passive circuits are limited by balancing current constraints.
Innovation Solution
A cell balancing circuit design that includes a first and second switch, a first and second winding wire forming a transformer, and additional switches and diodes to control current flow between central and outer battery cells during charging and discharging, reducing the number of components and optimizing energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive cell balancing circuit is used, then the circuit structure is simple, but the balancing current is limited due to heat through a resistor
Solution Approach 1:
The patent replaces the passive resistor-based current limiting mechanism with an active switching circuit controlled by a microcontroller. The MOSFETs (Q1-Q4) and control logic substitute for the thermal limitations of passive resistance, enabling precise digital control of balancing current without heat-induced current reduction.
Solution Approach 2:
The patent dynamically changes the balancing current parameter based on cell voltage differences. The microcontroller adjusts the duty cycle of PWM signals to MOSFET gates, varying the effective resistance and thus the balancing current in real-time based on the measured voltage deviation between cells, allowing current to scale with the needed balancing amount.
2Productivity
If an active cell balancing circuit is used, then the balancing current can be increased, but many elements are required which increases the cost
Solution Approach 1:
The microcontroller serves multiple functions: it measures cell voltages, determines voltage deviations, generates PWM control signals for all four MOSFETs, and monitors balancing progress. This single component replaces what would otherwise require multiple dedicated control circuits, reducing overall system complexity while maintaining high balancing current capability.
Solution Approach 2:
The patent combines the balancing control function with the existing battery management system's microcontroller. The same processor that monitors battery status is used to control the balancing operation, merging multiple functions into a single integrated control unit rather than adding separate dedicated balancing control hardware.
3Productivity
If an active cell balancing circuit is used, then the balancing current can be increased, but the cost of the cell balancing circuit is increased
Solution Approach 1:
The microcontroller performs multiple functions including voltage measurement, balancing control, and MOSFET drive signaling. By making the control unit multi-functional rather than dedicated solely to balancing, the per-function cost is reduced while still achieving high balancing current capability through software-controlled PWM modulation.
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 design reduces the number of components and costs while effectively balancing cell voltages by controlling current flow and energy transfer between central and outer battery cells, thereby extending battery life and improving charging and discharging efficiency.
Implementation Method 1
The first winding wire and the second winding wire may form a transformer
Data Source
AI summary
A cell balancing circuit connected to a plurality of cells connected in series includes a first switch, a first winding wire, and a second switch coupled in series between both terminals of a central battery cell among the plurality of cells; and a third switch, a second winding wire, and a fourth switch coupled in series between a positive electrode of one and a negative electrode of an outer battery cells except the central battery cell among the plurality of cells. During the charge or discharge, in a condition that the cell voltage difference between the central battery cell and the outer battery cell is greater than or equal to a predetermined threshold value, during the ON period of the first switch and the second switch, a first side current flows through the first switch, the first winding wire, and the second switch.