MOSFET Reverse Battery Protection Circuit for Parallel Batteries
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Solution Overview
Problem
Existing battery-powered devices that use parallel-coupled batteries face issues with reverse battery installation, leading to abnormal operation, damage, and premature battery discharge, as mechanical safeguards are costly and ineffective, and known protection circuits using diodes or MOSFETs result in power losses or ineffectiveness.
Innovation Solution
A reverse battery protection circuit employing P-channel and N-channel MOSFETs, where the gates of the MOSFETs are directly coupled to battery terminal connectors, allowing the MOSFETs to switch into a non-conductive state in case of a reverse connection, isolating the load and preventing premature discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical safeguards such as special battery connectors are used to prevent reverse battery installation, then reverse battery protection is improved, but device cost increases and effectiveness is reduced for certain battery types
Solution Approach 1:
The patent replaces mechanical safeguards (special battery connectors) with an electrical protection circuit using MOSFETs. This substitution eliminates the need for complex mechanical structures while providing effective reverse battery protection through electrical switching action that isolates the load when reverse polarity is detected.
Solution Approach 2:
The patent introduces MOSFETs as intermediary components between the battery terminals and the load. These MOSFETs act as controllable switches that mediate the connection, allowing normal operation when batteries are correctly installed and automatically isolating the load when reverse installation is detected, thus protecting the system without requiring complex mechanical safeguards.
2Reliability
If diode-based protection circuits are used to protect against reverse battery installation, then reverse battery protection is improved, but power losses increase
Solution Approach 1:
The patent changes the operating parameters of the protection circuit by using MOSFETs instead of diodes. MOSFETs have much lower on-resistance compared to diode forward voltage drops, thereby significantly reducing power losses while maintaining reverse battery protection functionality. The MOSFETs operate in their low-resistance conducting state during normal operation.
3Loss of energy
If known MOSFET protection circuits are used, then power losses are reduced, but effectiveness is reduced with parallel-coupled batteries
Solution Approach 1:
The patent segments the protection circuit into separate MOSFET branches for each battery connection. Each MOSFET is independently controlled based on the polarity detection at its respective battery terminal. This segmentation allows the circuit to effectively handle parallel-coupled batteries by independently managing each battery's connection state, preventing the protection circuit from becoming ineffective due to conflicting signals.
Solution Approach 2:
The patent designs a universal protection circuit that works with various battery configurations including parallel-coupled batteries. The circuit uses polarity detection and MOSFET switching to provide multi-functional protection: it protects against reverse installation, works with different battery types (coin cells, lithium cells), and maintains effectiveness regardless of the specific parallel-battery holder or connector configuration used in the 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
The solution effectively protects the load from reverse battery connections by isolating the incorrectly installed battery, preventing premature discharge, and ensuring continued operation with a correctly installed battery, while minimizing power losses.
Implementation Method 1
allowing the MOSFETs to switch into a non-conductive state in case of a reverse connection, isolating the load and preventing premature discharge
Data Source
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AI summary
Reverse battery protection circuits for devices powered by parallel-coupled batteries. Each reverse battery protection circuit includes one first P-channel, one second P-channel and one first N-channel MOSFETs. Each positive battery terminal connector of a battery-powered device is coupled to a drain of the first P-channel and gates of the first N-channel and second P-channel MOSFETs. Each negative battery terminal connector of the battery-powered device is coupled to a source of the first N-channel and, via a resistor, to the gates of the first N-channel and the second P-channel MOSFETs. The battery-powered device is connected between a first node of a common connection of the sources of the first and second P-channel MOSFETs and a second node connected to the negative battery terminal connector. In the event of a reverse battery connection, one or more of the protection circuit's P-channel and N-channel MOSFETS can switch to a non-conductive state to isolate the battery-powered device's load from an incorrectly installed battery and prevent the incorrectly installed battery from prematurely discharging. In some embodiments, the load can be powered by a single correctly-installed battery. Fig. 15