Integrated Thermal Fuse Resistor with Ceramic Substrate
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Solution Overview
Problem
Current thermal fuse resistors for over-current and over-temperature protection in switching mode power supplies are either too large for automatic plug-in, lack reliable heat transfer, or fail to provide effective axial taping and automatic plug-in capabilities, posing safety risks due to high surface temperatures and potential fires.
Innovation Solution
A compact, integrated thermal fuse resistor design featuring a ceramic substrate, resistor body, temperature sensing body, and lead wires with improved heat conduction through a tubular electrode cap, allowing for axial taping and automatic plug-in, while ensuring quick and accurate over-current and over-temperature protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thermal fuse is externally connected to the wire-wound resistor, then the over-current and over-temperature protection function is improved, but the device occupies more PCB area and requires more pads
Solution Approach 1:
The patent combines the thermal fuse and wire-wound resistor into a single integrated device where the thermal fuse is configured inside the resistor body. The lead wires of the thermal fuse are connected to the end caps of the resistor, forming a series-connected structure that occupies only one PCB area with two pads, thereby resolving the contradiction between protection function and PCB area occupation.
Solution Approach 2:
The thermal fuse is nested inside the wire-wound resistor body, with the fuse lead wires connected to the resistor end caps. This nesting arrangement allows the thermal protection function to be embedded within the resistor structure itself, eliminating the need for separate external mounting and reducing PCB area requirements.
2Volume of moving object
If the thermal fuse resistor is made compact, then the volume is reduced, but the axial taping function cannot be realized
Solution Approach 1:
The patent employs asymmetric design in the arrangement of lead wires and internal components to enable axial taping functionality. The lead wires are positioned and configured asymmetrically within the compact body to allow proper insertion and taping orientation, thus achieving both volume reduction and axial taping capability.
Solution Approach 2:
The patent optimizes the three-dimensional internal layout of the integrated device, arranging components and lead wires in different spatial dimensions to accommodate axial taping requirements within a compact volume. This dimensional optimization allows the small device to maintain proper lead wire orientation for automatic plug-in while minimizing overall size.
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 integrated design provides enhanced heat conduction, faster response to temperature increases, and improved safety by preventing overheating, with the ability to automatically cut off the circuit before damage occurs, and is suitable for various electronic devices and motors.
Implementation Method 1
The temperature sensing body is arranged in an inner cavity of the first electrode cap... ensuring quick and accurate over-current and over-temperature protection
Implementation Method 2
when the power is over ten or more times of the rated power of the resistor, the alloy wire of the wire-wound resistor would be overheated and therefore fused
Implementation Method 3
the current flowing through the wire-wound fuse resistor is often below the fusing current, such that the fusing function of the wire-wound resistor does not work while the surface temperature of the wire-wound resistor reaches 300° C. ̃500° C. or even higher
Data Source
AI summary
A thermal fuse resistor including a ceramic substrate, a resistor body, a temperature sensing body, a first electrode cap, a second electrode cap, a first lead wire, a second lead wire, and a third lead wire. A first end of the ceramic substrate is provided with a first electrode cap, and a second end of the ceramic substrate is provided with a second electrode cap. The first electrode cap includes a main body, an inner end, and an outer end with an opening. The outer end includes an everted edge closely contacting the first end of the ceramic substrate. The main body and the inner end are arranged inside the ceramic substrate. The first lead wire extends outward from an outer end. One end of the third lead wire is electrically connected to the second electrode cap.