Load Control Device Current Limiting Fuse Protection
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Solution Overview
Problem
Conventional load control circuits with fuses connected between power sources and power supply terminals face challenges in managing varying load currents, leading to potential fuse melting and increased costs due to larger fuse capacities and wire diameters, without effective protection for the power supply terminal.
Innovation Solution
A load control device with a current detector and controller that calculates total current through the fuse and limits load currents when a physical quantity related to the connecting member exceeds a reference value, reducing the need for increased fuse capacity and wire diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuse capacity and wire diameter are increased to handle varying load currents, then overcurrent protection reliability is improved, but device cost and complexity increase
Solution Approach 1:
The controller calculates the total current through the fuse before it can cause damage, and preemptively limits the load current when the physical quantity (heat quantity or temperature) approaches dangerous levels. This preliminary detection and control action prevents fuse melting without requiring oversized fuses or wires.
Solution Approach 2:
The system continuously monitors the physical quantity related to the connecting member (heat quantity or temperature) and feeds this information back to the controller, which adjusts the load current accordingly. This closed-loop feedback mechanism enables dynamic current management that protects the fuse while allowing maximum safe current flow.
2Reliability
If fuse capacity is increased to prevent melting under high load currents, then protection reliability is improved, but cost increases
Solution Approach 1:
The controller performs preliminary calculation of total current and monitoring of physical quantity (heat quantity or temperature) to detect approaching dangerous conditions before fuse melting occurs. This allows the use of smaller, more cost-effective fuses by preventing overload conditions through active control.
Solution Approach 2:
The load control device itself provides the protection function through active current monitoring and limiting, rather than relying on passive oversized fuse protection. The system monitors its own operating conditions and self-regulates to prevent damage, eliminating the need for excessive fuse capacity.
3Reliability
If wire diameter is increased to handle high currents without deformation, then current carrying capacity is improved, but device complexity and cost increase
Solution Approach 1:
The controller calculates and monitors the physical quantity (heat quantity or temperature) of the connecting member before wire deformation occurs, and preemptively limits the load current to safe levels. This prevents thermal damage to wires without requiring oversized wire diameters.
Solution Approach 2:
The system continuously monitors the physical quantity of the connecting member and feeds this information back to control the load current. This real-time feedback enables the use of thinner, more cost-effective wires by dynamically managing current to prevent thermal overload.
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 configuration prevents fuse melting and wire deformation by limiting load currents, allowing for reduced fuse capacity and wire size while maintaining effective overcurrent protection, thus reducing costs and expanding the usable current range.
Implementation Method 1
calculate a physical quantity correlating with the total current and related to a connecting member that connects between the fuse and the power supply terminal
Data Source
AI summary
A load control device includes a power supply terminal connected to a power source via a fuse, a load driver configured to drive loads by electric power supplied from the power source via the fuse and the power supply terminal, a current detector configured to detect load currents that flow through the loads, respectively, and a controller. The controller is configured to calculate a total current that flows through the fuse based on the load currents detected by the current detector, calculate a physical quantity correlating with the total current and related to a connecting member that connects between the fuse and the power supply terminal in response to that the total current is equal to or higher than a predetermined current value, and limit at least one of the load currents in response to that the physical quantity is equal to or greater than a reference value.