Common Mode Choke Coil Circuit for Noise Reduction
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Solution Overview
Problem
In in-vehicle electronic circuits, the isolation of signal ground and frame ground creates a large noise loop, leading to common mode noise generation, and existing solutions like common mode choke coils require larger component sizes for necessary inductance, making size reduction difficult.
Innovation Solution
An electronic circuit design featuring a shield line with a pair of signal lines and a shield, a common mode choke coil with three magnetically coupled coils, and a capacitor connected in parallel with one of the coils, which reduces noise effectively while allowing for size reduction by varying the capacitance value to match the frequency of common mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal ground and frame ground are isolated from each other, then damage from external noise such as ESD can be prevented, but a large loop is formed and common mode noise is generated
Solution Approach 1:
The patent introduces a common mode choke coil as an intermediary component between the signal ground and frame ground. This choke coil provides a controlled impedance path that prevents direct coupling of noise while maintaining isolation for ESD protection, thereby resolving the contradiction between protection and noise generation.
Solution Approach 2:
The patent modifies the electrical parameters of the ground connection by introducing inductance through the common mode choke coil. This parameter change transforms the ground connection from a direct low-impedance path to a controlled high-impedance path at noise frequencies, reducing common mode noise while maintaining ESD protection capability.
2Object-affected harmful factors
If a common mode choke coil including three lines is used to obtain necessary inductance, then noise filtering is improved, but component size increases
Solution Approach 1:
The patent combines multiple functions into a single common mode choke coil component. The coil provides both the necessary inductance for noise filtering and the magnetic coupling for common mode rejection, eliminating the need for separate components and reducing overall size while maintaining effective noise filtering.
Solution Approach 2:
The patent optimizes the inductance value and magnetic coupling coefficient of the common mode choke coil to achieve effective noise filtering with minimal component size. By carefully selecting these parameters, the patent reduces the physical dimensions required while maintaining the necessary filtering performance.
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 design achieves size reduction and effective noise reduction by securing a return path for signals and enhancing the common mode choke coil's filtering capabilities, improving noise attenuation across a wide frequency range.
Implementation Method 1
a common mode choke coil including a first coil, a second coil, and a third coil which are magnetically coupled to one another
Implementation Method 2
a capacitor which is connected in parallel with the third coil
Implementation Method 3
in order to obtain a necessary inductance, the size of components needs to be increased
Data Source
AI summary
An electronic circuit includes a shield line including first and second signal lines and a shield. The first and second signal lines are connected to a signal source, and the shield coating is around the first and second signal lines. The electronic circuit further includes a signal ground near the signal source; a frame ground that is isolated from the signal ground and connected to the shield; a common mode choke coil that includes first, second and third coils magnetically coupled to one another; and a capacitor that is connected in parallel with the third coil. The first coil is connected in series between the signal source and the first signal line. The second coil is connected in series between the signal source and the second signal line. The third coil and the capacitor that are connected in parallel are connected between the signal ground and the frame ground.