Battery Bypass Circuit Control for Parasitic Diode Heating
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Solution Overview
Problem
Existing battery protection systems using a bypass circuit with back-to-back FETs face issues with FET breakdown due to heat generation by parasitic diodes during overcharge or over-discharge, as current exceeding permissible values can lead to FET failure.
Innovation Solution
A management device controls a relay and back-to-back connected FETs to manage discharge or charge paths through parasitic diodes, closing the FETs or relay based on current, time, and temperature conditions to prevent overheating and breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bypass circuit with back-to-back FETs is used to control charge and discharge paths, then the ability to restrict charge or discharge is improved, but the risk of FET breakdown due to heat generation from parasitic diodes increases
Solution Approach 1:
The management device performs preliminary assessment of current, time, and temperature conditions before allowing current to flow through the parasitic diode. By predicting whether the accumulated heat will cause breakdown, the system proactively prevents FET failure while maintaining charge/discharge control functionality.
Solution Approach 2:
The management device continuously monitors current, time, and temperature conditions and uses this feedback to dynamically control the FETs. When conditions approach dangerous thresholds, the management device adjusts FET states to prevent overheating, creating a closed-loop control system that balances adaptability with reliability.
2Duration of action of moving object
If current flows through the parasitic diode for extended periods, then charge or discharge can be maintained through the bypass circuit, but heat generation increases causing FET breakdown
Solution Approach 1:
The management device implements periodic monitoring and control of the FETs based on accumulated time and current conditions. By assessing whether the product of current and time exceeds thresholds, the system periodically adjusts FET operation to prevent excessive heat buildup, enabling sustained charge/discharge while controlling temperature.
Solution Approach 2:
The management device applies beforehand cushioning by monitoring the cumulative effect of current over time and taking preventive action before temperature reaches dangerous levels. This proactive approach allows the system to maintain charge/discharge operations while preventing FET breakdown through early intervention.
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 suppresses FET breakdown by managing current flow, reducing heat generation, and minimizing operational noise, particularly in energy storage systems like automobile batteries.
Implementation Method 1
energization causes the parasitic diode to generate heat
Data Source
AI summary
An energy storage apparatus includes a cell, a relay which cuts off a current of the cell, a bypass circuit connected in parallel with the relay, and a management device. The bypass circuit includes two back-to-back connected FETs. When an abnormality of the cell is detected by the management device, the management device opens the relay, closes one FET of the two FETs, and opens the other FET, and permits a discharge or a charge of the cell through a path passing through a parasitic diode of the FET. When the discharge or the charge is being performed through the path passing through the parasitic diode, if a current I and an energization time T of the FET(s) reach a predetermined condition or the temperature of the FET(s) reaches a predetermined condition, the management device 150 closes the relay 53 and the other FET(s) that is open.