Electronic Control Device Guard Pattern Resonance Shielding
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Solution Overview
Problem
Existing electronic control devices for automobiles face challenges in reducing unnecessary electromagnetic radiation and external noise without increasing the number of connection portions between the housing and the printed circuit board, as described in PTL 1.
Innovation Solution
The electronic control device incorporates a guard pattern on the printed circuit board, connected to the ground pattern via a resistor or capacitor at intermediate points where the housing is fixed, to create opposite electric field distributions and reduce resonance-induced electromagnetic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metal housing or shield is used to cover the printed circuit board, then electromagnetic radiation is prevented, but resonance occurs in the space between the housing and the board generating unnecessary electromagnetic radiation
Solution Approach 1:
The patent changes the electrical parameters by introducing a guard pattern with specific impedance characteristics (connected to ground via resistor or capacitor) to alter the resonance behavior of the housing-board space, transforming the harmful resonance into a controlled electrical parameter adjustment that suppresses electromagnetic radiation
Solution Approach 2:
The guard pattern acts as an intermediary element between the signal lines and the metal housing, providing a controlled electrical path that prevents the buildup of resonant electromagnetic fields while maintaining the shielding function of the housing
2Object-affected harmful factors
If multiple connection portions are added between the housing and the printed circuit board, then noise reduction is achieved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the grounding function by distributing ground connections through the guard pattern along the board periphery, replacing the need for multiple discrete connection portions while achieving comprehensive noise reduction across different areas of the board
Solution Approach 2:
The guard pattern serves multiple functions simultaneously: it provides electromagnetic shielding, reduces noise influence, and maintains proper grounding, eliminating the need for separate connection portions that would otherwise be required for each function
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 effectively reduces the influence of unnecessary electromagnetic radiation and external noise without increasing the number of connection portions, thereby improving noise immunity and radiation shielding.
Implementation Method 1
since a space formed between the metal housing and the printed circuit board acts as a resonator in a certain frequency range, the unnecessary electromagnetic radiation is generated in the frequency range
Implementation Method 2
the guard pattern and a ground pattern of a circuit in the board are connected to each other such that an electric field distribution of resonance generated by a side length of the board and an electric field distribution of resonance generated by a side length of the housing form opposite electric field distributions
Data Source
AI summary
An electronic control device includes: a housing accommodating a board on which an electronic component is mounted; and a guard pattern formed on an outer peripheral portion of the board. The guard pattern and a ground pattern of a circuit in the circuit board are connected to each other in a vicinity of an intermediate point of fixed positions where an upper portion of the housing and a lower portion of the housing are fixed to each other.