Battery Cell Balancing Circuit Using Parallel MOSFET Segmentation
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Solution Overview
Problem
Conventional lithium ion battery balancing circuits require a large number of high-voltage MOSFETs to manage parasitic diodes, leading to inefficiencies and increased manufacturing costs due to high internal voltage requirements and power wastage.
Innovation Solution
A switching circuit design using parallel pairs of MOSFETs with parasitic diodes, reducing the internal voltage applied to switching elements and minimizing the number of MOSFETs needed, allowing for the use of lower-voltage switches that are more efficient and cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MOSFETs with high internal voltage are used to manage parasitic diodes in battery balancing circuits, then the circuit can properly interrupt bi-directional current flow, but the number of MOSFETs required increases significantly and manufacturing cost increases
Solution Approach 1:
The patent divides the battery cell into multiple voltage segments (first voltage node and second voltage node) and uses separate switching circuits for each segment. This segmentation allows each MOSFET to handle only a portion of the total voltage, reducing the internal voltage requirement and enabling the use of lower-voltage, more efficient MOSFETs while maintaining reliable current interruption capability.
Solution Approach 2:
The patent introduces a voltage division dimension by creating multiple voltage nodes (first and second voltage nodes) within the switching circuit. This dimensional change in voltage handling allows the system to manage high total battery voltage using multiple lower-voltage switching stages, thereby reducing MOSFET internal voltage requirements and overall circuit complexity.
2Reliability
If MOSFETs with high internal voltage tolerance are used, then they can withstand the total battery voltage, but power loss and heat generation increase
Solution Approach 1:
The patent segments the voltage handling across multiple MOSFETs and voltage nodes, so each MOSFET operates at a lower voltage level. This segmentation reduces the power loss in each individual MOSFET (since power loss is proportional to the square of the voltage), thereby reducing total energy loss and heat generation while maintaining the ability to withstand the total battery voltage through the series arrangement.
3Ease of operation
If a large number of MOSFETs are used to properly switch battery cells, then current control is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses segmentation to reduce the number of MOSFETs needed by having each MOSFET handle a specific voltage segment rather than requiring all MOSFETs to handle the full battery voltage. This reduces component count and manufacturing cost while maintaining precise current control capability through the segmented switching architecture.
Solution Approach 2:
The patent changes the voltage parameter distribution across the switching circuit by introducing multiple voltage nodes with different voltage levels. This parameter change allows the use of lower-voltage MOSFETs that are more cost-effective and easier to manufacture, while still achieving proper current control through the modified voltage distribution scheme.
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 power loss, heat generation, and manufacturing costs while improving balancing efficiency by using fewer and lower-voltage switching elements, effectively miniaturizing the battery balancing system.
Implementation Method 1
plural pairs of switching means, each pair of which are connected to each other in parallel and interrupt a flow of electric current in a bi-direction
Implementation Method 2
The switching means includes a Metal Oxide Silicon Field Effect Transistor (MOSFET) having a parasitic diode
Data Source
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AI summary
Disclosed is a switching circuit for balancing battery cells. The switching circuit includes plural pairs of switching means, each pair of which are connected to each other in parallel and interrupt a flow of electric current in a bi-direction in order to reduce the internal voltage applied to the switching means. According to the present invention, since the switching elements of low internal voltage can be used for the switching circuit, it is possible to constitute the switching circuit for cell balancing without use of switching elements of high internal voltage and to reduce the number of MOSFETs, thereby making it possible to design the switching circuit effectively. Since the MOSFETs having the low internal voltage and low resistance are used for the switching circuit, it is possible to reduce a loss of the electric current due to the resistance during the cell balancing, thereby improving the balancing efficiency and reducing heat generation.