Switching Circuit Layout for Surge Protection and Insulation
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Solution Overview
Problem
Switching circuits in complex electromagnetic environments are vulnerable to surge voltages, leading to component damage and failure due to insufficient isolation and the need for costly, space-consuming overvoltage protection devices at each contact switch, which compromises insulation and test performance.
Innovation Solution
A switching circuit design with distributed capacitance between the contact switch and coil, combined with overvoltage protection devices at the coil side, reduces surge voltage impact and eliminates the need for protection devices at each contact switch, enhancing voltage withstand capability and test performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overvoltage protection devices are added at each switching interface to defend against surge voltage, then anti-surge capability is improved, but insulation performance deteriorates causing failure in voltage withstand tests
Solution Approach 1:
The patent divides the overvoltage protection function into two segments: a first overvoltage protection device at the coil side and a second overvoltage protection device at the control circuit side. This segmentation allows each protection device to handle only a portion of the surge voltage, preventing any single device from compromising the overall insulation performance while maintaining comprehensive anti-surge capability.
Solution Approach 2:
The patent introduces an intermediary approach by placing the first overvoltage protection device between the switching interface and the coil, and the second protection device between the coil and the control circuit. These intermediary protection devices gradually reduce the surge voltage step-by-step, preventing direct exposure of critical components to full surge voltage while maintaining insulation integrity.
2Reliability
If overvoltage protection devices are added at each contact switch to protect against surge voltage, then anti-surge capability is improved, but device complexity and board area increase
Solution Approach 1:
The patent merges the overvoltage protection function into two strategic locations (coil side and control circuit side) rather than placing separate protection devices at each contact switch. This merging approach reduces the total number of protection devices while maintaining comprehensive protection across all switching interfaces through the shared protection architecture.
Solution Approach 2:
The first overvoltage protection device at the coil side serves a universal function by protecting multiple contact switches simultaneously, as the coil is common to multiple switching circuits. This multi-functional approach reduces the overall number of protection devices needed compared to individual protection at each contact switch.
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 design effectively reduces surge voltage exposure to critical components, improves circuit reliability, and enhances the switching circuit's ability to pass voltage withstand tests while minimizing complexity and cost.
Implementation Method 1
a distributed capacitance is provided between the contact switch and the coil
Implementation Method 2
a first overvoltage protection device is connected in parallel with the coil, a second overvoltage protection device is connected between an output end of the coil and a reference potential
Data Source
Figure 1
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Figure 4~5
AI summary
The embodiment of the present application relates to the technical field of circuits, and provides a switch quantity output circuit, a circuit board assembly and an electronic device, the circuit includes a control circuit, a contact switch, a coil, a first overvoltage protection device, a second overvoltage protection device. A first end of the control circuit is connected to a first end of the coil, a second end of the control circuit is connected to a second end of the coil, and a distributed capacitance is provided between the contact switch and the coil; the control circuit is configured to control the contact switch to turn-on and turn-off by adjusting a magnetic field of the coil; a first end of the first overvoltage protection device is connected between the first end of the control circuit and the first end of the coil, and a second end of the first overvoltage protection device is connected between the second end of the control circuit and the second end of the coil; and a first end of the second overvoltage protection device is connected between the second end of the control circuit and the second end of the coil, and a second end of the second overvoltage protection device is connected to a protective ground.