USB Port Metal Housing Floating Capacitor PCB Design
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Solution Overview
Problem
USB ports on electronic devices are prone to short circuits due to the accumulation of non-insulation materials like perspiration and dust, which can lead to overheating and safety hazards, and current solutions occupy internal space, interfering with antennas during charging or data transmission.
Innovation Solution
The USB port's metal housing is not connected to the ground of the PCB, instead forming a capacitor with a floating area on the PCB to prevent short circuits and antenna interference, allowing for efficient noise backflow and reduced physical occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metal housing of the USB port is connected to the ground on the PCB, then the USB port is fastened and grounded, but a micro short circuit occurs between the power supply and ground due to non-insulation materials accumulation, causing heat accumulation and burning
Solution Approach 1:
The ground connection function is extracted from the metal housing and relocated to dedicated ground contact pads on the PCB. The metal housing is no longer directly connected to ground, eliminating the micro short circuit path through perspiration and dust accumulation while maintaining proper grounding through the contact pads.
Solution Approach 2:
Dedicated ground contact pads are introduced as intermediary elements between the metal housing and the PCB ground. These contact pads provide a controlled grounding path that avoids the harmful micro short circuit issue while maintaining electrical connectivity and safety.
2Reliability
If an additional protection component is used to prevent micro short circuit, then the USB port is protected from short circuit, but the protection component occupies internal space of the electronic device
Solution Approach 1:
The grounding function and protection function are merged into the PCB structure itself through dedicated ground contact pads. This eliminates the need for separate protection components, achieving both short circuit protection and space savings by integrating multiple functions into the existing PCB architecture.
Solution Approach 2:
The ground contact pads serve multiple functions: they provide mechanical support for the USB port, establish electrical grounding, and prevent micro short circuits. This multi-functionality eliminates the need for additional dedicated protection components, saving internal device space.
3Ease of operation
If the USB port is disposed at the lower part of the electronic device, then the USB port is easily accessible, but the antenna disposed at the lower part is interfered with during charging or data transmission
Solution Approach 1:
The harmful electromagnetic interference effect is extracted and redirected to the ground through the dedicated ground contact pads. By providing a controlled grounding path, the interference generated by the USB port during charging or data transmission is directed away from the antenna, preventing disruption while maintaining the USB port's accessible lower position.
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 solution effectively prevents short circuits and antenna interference, ensuring user safety and maintaining device compactness by using a capacitor configuration on the PCB to manage noise and prevent overheating.
Implementation Method 1
a floating area and a metal area opposite to the floating area are disposed on the PCB, and the metal housing of the USB port of the electronic device is connected to the floating area, so as to form a capacitor
Implementation Method 2
allowing for efficient noise backflow and reduced physical occupancy
Data Source
Figure 1a~1b
Figure 1c
Figure 2~3
AI summary
An electronic device, a USB port, and a printed circuit board are provided. The printed circuit board has at least two cabling layers, a first cabling layer in the at least two cabling layers has a first floating area and a line outside the first floating area, there is an insulation medium between the first floating area and the line outside the first floating area, a second cabling layer in the at least two cabling layers and the first cabling layer are adjacent and isolated by using an insulation material, the second cabling layer has a first metal area, an orthographic projection of the first floating area on the second cabling layer and the first metal area have an overlapping area, and the first floating area is not connected to the first metal area; and a metal housing of the USB port has a plurality of fixed contacts, the plurality of fixed contacts are fastened to the printed circuit board, the plurality of fixed contacts are not connected to a ground of the printed circuit board, the plurality of fixed contacts include a first fixed contact, the first fixed contact is connected to the first floating area, and the first fixed contact is not connected to the first metal area.