Switch Box Breaker Circuit Prevents Reverse Current in Parallel Batteries
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Solution Overview
Problem
In-vehicle power supply systems face the challenge of preventing reverse connection current flow when batteries are connected with reversed polarities, which can lead to battery deterioration and increased costs due to the use of less durable lead storage batteries in combination with lithium-ion batteries.
Innovation Solution
A switch box incorporating a relay transistor circuit with N-channel MOSFETs and a breaker circuit that short-circuits the source and gate terminals of the MOSFETs when a potential difference reversal is detected, ensuring the batteries are not connected with reversed polarities, thereby preventing reverse current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a pair of batteries are connected in parallel to satisfy power supply demand, then the power supply capacity is improved, but the risk of reverse connection current flow increases when battery polarity is reversed
Solution Approach 1:
The breaker circuit performs preliminary detection of battery polarity before the relay transistor circuit establishes parallel connection. By detecting the sign of potential difference between batteries and comparing it with the reference potential beforehand, the system prevents reverse connection current from flowing, thus resolving the contradiction between enabling parallel power supply and preventing reverse connection damage
Solution Approach 2:
The relay transistor circuit acts as an intermediary between the batteries and the parallel connection. It controls the connection state based on signals from the breaker circuit, allowing safe parallel operation when polarity is correct and blocking connection when reverse connection is detected, thus enabling both power supply capability and reverse connection protection
2Ease of manufacture
If lead storage battery is used for backup power supply to reduce cost, then the system cost is reduced, but the battery deteriorates quickly due to frequent charging/discharging
Solution Approach 1:
The breaker circuit provides feedback control by continuously monitoring the potential difference sign between batteries. This feedback mechanism ensures that the lead storage battery is only connected in parallel when polarity is correct, preventing damage from reverse connection and enabling long-term reliable operation for backup power supply applications
Solution Approach 2:
The system uses the inexpensive lead storage battery for backup power supply where long-term stationary storage is required. The breaker circuit protects this cost-effective battery from reverse connection damage, allowing the system to benefit from lower cost while maintaining acceptable lifetime for backup applications
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 switch box effectively prevents reverse connection current flow, ensuring the longevity of batteries and reducing costs by maintaining the appropriate state of charge for both lead storage and lithium-ion batteries, thus enhancing the reliability of the in-vehicle power supply system.
Implementation Method 1
a relay transistor circuit configured to connect a pair of batteries in parallel; a pair of N-channel MOSFETs having source terminals connected back to back
Implementation Method 2
the breaker circuit may include a short-circuiting circuit that short-circuits the source terminal and a gate terminal of each of the N-channel MOSFETs
Data Source
AI summary
A switch box includes a relay transistor circuit connecting a pair of batteries in parallel, and an breaker circuit that breaks the relay transistor circuit when a sign of a potential difference between a potential of at least one of the pair of batteries connected to the relay transistor circuit and a predetermined reference potential is reversed with respect to the sign of the potential difference in which the batteries are correctly connected.