Back-to-Back MOSFETs for Battery Overvoltage Protection
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Solution Overview
Problem
Conventional lithium-ion battery systems face issues with low voltage when used in industrial and on-vehicle equipment, requiring multiple cells connected in series, which can lead to circuit destruction due to reverse voltages and overvoltages caused by counter electromotive forces during discharge and charge control interruptions.
Innovation Solution
A storage battery device configuration that includes a battery group with N-channel MOSFETs connected back-to-back at the low potential side, along with a drive controller and snubber circuits for overvoltage protection, stabilizing the operation of charge and discharge control FETs to prevent circuit damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If N-channel MOSFETs are used for charge and discharge control in modularized storage battery devices, then the battery system can achieve higher voltage and power output through series connection of battery groups, but reverse voltage and overvoltage caused by counter electromotive force during MOSFET interruption can destroy the control circuit
Solution Approach 1:
The patent applies beforehand cushioning by introducing snubber circuits (comprising resistors and capacitors) connected in parallel with the MOSFETs before voltage spikes can occur. These circuits pre-establish protective pathways that absorb counter electromotive force and reverse voltage when MOSFETs are interrupted, preventing circuit destruction while maintaining the high power capability of the series-connected battery system
Solution Approach 2:
The patent uses diodes as intermediary protective elements connected in anti-parallel with the MOSFETs. These diodes act as mediators that conduct reverse current when counter electromotive force occurs during MOSFET interruption, diverting harmful reverse voltage away from the MOSFET gate and control circuit while allowing the MOSFETs to continue providing high power output control
2Power
If multiple battery cells are connected in series to increase voltage for industrial and on-vehicle equipment, then higher power output is achieved, but the complexity of battery pack configuration and control increases
Solution Approach 1:
The patent applies segmentation by dividing the battery system into modularized storage battery devices, where each module contains a battery group with integrated charge and discharge control circuits. This modular structure allows higher voltage to be achieved through series connection of standardized modules, reducing overall system complexity compared to custom configurations while maintaining high power output capability
Solution Approach 2:
The patent implements universality by designing modularized storage battery devices that can be universally configured in series to achieve different voltage levels. Each module contains universal control circuits that can operate independently or in combination with other modules, simplifying the battery pack configuration process while enabling flexible high-voltage applications for industrial and on-vehicle equipment
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
The solution effectively stabilizes the operation of MOSFETs and prevents circuit destruction by managing voltage and current resistance, ensuring safe and efficient charging and discharging processes.
Implementation Method 1
an overvoltage caused by a counter electromotive force occurs, which may destroy a MOSFET control circuit
Implementation Method 2
N-channel MOSFETs (a discharge control N-channel MOSFET and a charge control N-channel MOSFET) the drains of which are back-to-back connected (commonly connected) to a low potential side of a battery group
Implementation Method 3
a reverse voltage is applied via a source terminal of the charge control N-channel MOSFET and a resistor for stabilizing the operation of the charge control N-channel MOSFET provided in between the source terminal and a gate terminal to an output terminal of an FET gate driver
Data Source
AI summary
According to one embodiment, a storage battery device includes a battery group, a charge-and-discharge control FET unit, and a drive controller. The battery group includes a plurality of battery cells connected in series. The charge-and-discharge control FET unit is connected to a low potential side of the battery group and includes at least a pair of N-channel MOSFETs source terminals of which are back-to-back connected. The drive controller outputs a drive control signal to a gate terminal of the respective N-channel MOSFETs included in the charge-and-discharge control FET unit. The drive control signal is generated based on a potential level of the source terminals.