Ferrite Bead Noise Suppression in Engine Pressure Detection
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Solution Overview
Problem
The configuration of connecting a controller and a detecting device via electric wires can lead to external radio waves interfering with the processing circuit, causing noise in the signals outputted from the processing circuit.
Innovation Solution
Incorporating ferrite beads with specific static characteristic nominal values and self-resonant frequencies into the power receiving, output, and grounding terminals to reduce noise interference, where the grounding ferrite bead has a smaller nominal value and higher self-resonant frequency compared to the power receiving and output ferrite beads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electric wires are used to connect the controller and the detecting device, then power supply and signal transmission are enabled, but the electric wires function as antennas that receive external radio waves and introduce noise into the processing circuit
Solution Approach 1:
Ferrite beads are introduced as intermediary components inserted into the electric wires at specific positions (power receiving terminal, output terminal, and grounding terminal). These ferrite beads act as mediators that allow normal signal transmission while blocking external radio wave interference, thus resolving the contradiction between maintaining electrical connection and preventing noise entry.
Solution Approach 2:
The patent specifies particular parameters for the ferrite beads including static characteristic nominal values (100Ω for power receiving and output ferrite beads, 50Ω for grounding ferrite bead) and self-resonant frequencies (greater than 500MHz). By carefully selecting these parameters, the ferrite beads effectively suppress noise across the relevant frequency range while maintaining proper circuit operation.
2Object-affected harmful factors
If ferrite beads are added to reduce noise, then noise resistance is improved, but the device complexity and number of components increase
Solution Approach 1:
The noise suppression function is segmented into three distinct locations: power receiving terminal, output terminal, and grounding terminal. Each location receives a specifically configured ferrite bead tailored to its function, allowing targeted noise suppression at each interface point rather than requiring a single complex solution throughout the entire circuit.
Solution Approach 2:
Different ferrite bead specifications are assigned to different terminals based on their specific requirements. The grounding ferrite bead has different parameters (50Ω, higher self-resonant frequency) compared to the power receiving and output ferrite beads (100Ω). This local optimization achieves effective noise suppression with appropriately sized components at each location.
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 noise entering the processing circuit from external sources, stabilizing the ground potential and minimizing noise superimposed on the output signals.
Implementation Method 1
power receiving ferrite bead connected to the power receiving terminal and a power receiving end in the processing circuit; an output ferrite bead connected to the output terminal and an output end in the processing circuit; and a grounding ferrite bead connected to the grounding terminal and a grounding end in the processing circuit
Data Source
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AI summary
A pressure detecting device that detects the combustion pressure in an internal combustion engine includes: a piezoelectric element 10 that outputs a charge signal corresponding to the pressure in a combustion chamber; and a mounting board 210 on which are mounted an integrating circuit 212 that integrates the charge signal outputted by the piezoelectric element 10 and an amplifier circuit 213 that amplifies a voltage signal obtained by integration. On the mounting board 210 are provided: a power receiving terminal 211a that receives a power-supply voltage from a controller; an output terminal 211b that outputs an output signal after amplification to the controller; and a grounding terminal 211c for making the ground of the controller and the mounting board 210 common. Furthermore, in the mounting board 210, the grounding terminal 211c and grounding ends of the integrating circuit 212 and the amplifier circuit 213 are connected by way of grounding ferrite beads 216.