Circuit Substrate Capacitor Placement for EMI Suppression
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Solution Overview
Problem
Existing methods for reducing electromagnetic interference (EMI) in electronic apparatuses are ineffective in controlling current flow from a circuit substrate to a cabinet, leading to unstable GND potential and increased electromagnetic radiation, especially when multiple substrates are integrated or revised, and they fail to address ESD measures effectively.
Innovation Solution
A circuit substrate with a capacitor connected to the power supply and GND, placed near the connecting part between the substrate and cabinet, reduces cabinet current by decreasing the potential difference across the capacitor, thereby suppressing electromagnetic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a filter is provided in the connecting part between circuit substrate GND and cabinet GND to control current strength, then electromagnetic radiation from cabinet is reduced, but GND potential stability deteriorates and circuit function may be affected
Solution Approach 1:
The invention divides the EMI suppression function into two separate locations: (1) a filter in the connecting part between substrate GND and cabinet GND to control current strength, and (2) additional filters in the connecting parts between power supply and GND near the substrate edges to control potential differences. This segmentation allows each filter to perform its specific function without interfering with the other, resolving the contradiction between EMI reduction and GND stability.
Solution Approach 2:
The invention introduces additional filtering components as intermediaries in the power supply connecting parts. These filters act as mediators that control potential differences between power supply and GND, preventing excessive voltage fluctuations from affecting circuit operation while allowing the main GND filter to continue suppressing electromagnetic radiation.
2Productivity
If multiple circuit substrates are implemented in one cabinet or substrates are repeatedly revised, then EMI optimization of cabinet structure becomes difficult and time-consuming, but electromagnetic radiation control remains necessary
Solution Approach 1:
The invention applies filters to the connecting parts between power supply and GND near the substrate edges as a preliminary measure. This preliminary action ensures that potential differences are controlled at the source before they can cause electromagnetic radiation problems, regardless of how many substrates are later added or how the cabinet configuration changes. This eliminates the need for repeated cabinet structure optimization.
Solution Approach 2:
The invention changes the approach from optimizing cabinet physical structure to controlling electrical parameters (potential differences and current strength) through filter components. By adjusting the filtering parameters in the connecting parts, the system can adapt to different numbers of substrates and configurations without requiring cabinet redesign, thus improving productivity while maintaining EMI control.
3Reliability
If connecting part is positioned near input/output part or 0Ω resistance is used for ESD measures, then ESD protection is improved, but electromagnetic interference problems are not solved
Solution Approach 1:
The invention merges ESD protection and EMI suppression functions into a single integrated filter component in the connecting parts between power supply and GND. The filter provides both ESD protection by handling transient voltage spikes and EMI suppression by controlling potential differences and current strength, eliminating the need for separate ESD measures that fail to address electromagnetic radiation.
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 reduces electromagnetic radiation from the cabinet by minimizing cabinet current through the strategic placement of capacitors, maintaining stable GND potential and improving EMI suppression, even with multiple substrates or revisions.
Implementation Method 1
a capacitor that connects a power supply conductor pattern and a GND conductor pattern
Data Source
AI summary
There is provided a circuit substrate to be mounted in an electronic apparatus, and the circuit substrate has a power supply and a GND. The GND of the circuit substrate is electrically connected to GNDs of other components of the electronic apparatus through connecting parts. The circuit substrate has a part or circuit that implements a low impedance in an intended frequency range between the peripheral conductor of the connecting part opening to be used for the connection and the power supply of the circuit substrate.