Circuit Device High-Frequency Filter Noise Immunity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing temperature detection systems face challenges in enhancing noise immunity of thermistors, leading to erroneous readings due to high-frequency noise, which requires costly external components and lengthy trial-and-error adjustments, affecting manufacturing consistency and increasing costs.
Innovation Solution
A circuit device connected to a temperature detection element via external signal lines and ground lines, incorporating a high-frequency filter inserted into the internal signal and ground lines near the connector, converting common-mode noise to normal-mode noise and reducing high-frequency current influx into the thermistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a noise filter is added proximately to the thermistor element or in the wire harness, then noise immunity is improved, but manufacturing cost increases
Solution Approach 1:
The noise filtering function is extracted from external components (noise filter in wire harness) and integrated into the circuit board's ground line structure. The ground line is designed with specific impedance characteristics (50-150 ohms) to inherently filter high-frequency noise, eliminating the need for additional external filtering components while maintaining noise immunity.
Solution Approach 2:
The ground line serves as an intermediary element that performs dual functions: providing the reference potential for thermistor measurement and simultaneously acting as a noise filter through its controlled impedance characteristics. This mediator approach allows the ground line to protect the measurement circuit from high-frequency noise without requiring separate filtering components.
2Reliability
If the routing of the thermistor harness is changed to adjust antenna characteristics, then noise immunity may be improved, but development time and complexity increase
Solution Approach 1:
Instead of changing the overall routing of the thermistor harness, the invention applies a localized solution at the circuit board connection point. The ground line is designed with specific impedance characteristics in the region where noise filtering is needed, while the rest of the harness routing remains unchanged. This local modification approach simplifies implementation compared to global routing changes.
3Reliability
If ferrite cores are used in the harness to adjust antenna characteristics, then noise immunity is improved, but cost increases significantly
Solution Approach 1:
The invention replaces expensive ferrite cores with a cost-effective ground line design that uses standard PCB trace or wire structures. The ground line's impedance characteristics provide the necessary noise filtering function without requiring costly magnetic materials, making the solution economically viable for mass production while maintaining effective noise immunity.
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 increases noise immunity of temperature detection elements at a lower cost, simplifying the process and reducing the risk of reoccurring failures by suppressing high-frequency noise without affecting direct current or low-frequency components.
Implementation Method 1
a high-frequency filter that is inserted into at least one of a foremost stage of the internal signal line and a foremost stage of the internal signal ground line as viewed from the connector
Implementation Method 2
A thermistor has properties of generating heat when a high-frequency current flows through the thermistor, causing a decrease in the resistance value
Data Source
AI summary
A circuit device that is connected to a temperature detection element that detects a temperature of an object via an external signal line and an external signal ground line includes a connector that is connected to the external signal line and the external signal ground line, an internal signal line that is connected to the external signal line via the connector, an internal signal ground line that is connected to the external signal ground line via the connector, a controlling circuit that is connected to the internal signal line and the internal signal ground line and detects the temperature of the object, and a high-frequency filter that is inserted into at least one of a foremost stage of the internal signal line and a foremost stage of the internal signal ground line as viewed from the connector.