Electrical Filter Device for Common-Mode Interference
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Solution Overview
Problem
Existing electrical filter devices for common-mode interference in the automotive industry face limitations in achieving steep insertion losses, particularly at low frequencies, due to high-frequency components, and require increased component values or multiple stages, which increase complexity and cost.
Innovation Solution
The electrical filter device incorporates a main inductance with a coil and an auxiliary inductance inductively coupled to it, along with an interference suppression capacitor, to achieve improved insertion losses through series resonance, allowing for lower capacitance values and reduced complexity without additional filter stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the nominal component part values of the filter components are increased or additional filter stages are connected in series to improve insertion loss at low frequencies, then the insertion loss is improved, but the device complexity and component size increase
Solution Approach 1:
The patent changes the electrical parameters of the filter circuit by introducing a resonant frequency ω0 = 1/√(L1*C1) that creates a pole in the transfer function. This parameter change enables the filter to achieve steep insertion loss characteristics without increasing component values or adding stages, as the resonant pole provides the necessary frequency-dependent attenuation.
Solution Approach 2:
The patent utilizes electrical resonance (analogous to mechanical vibration) by designing the LC circuit with specific L1 and C1 values that create a resonant frequency. This resonance effect produces the steep insertion loss characteristic at low frequencies without requiring additional filter stages, thereby reducing device complexity while maintaining reliability.
2Reliability
If the nominal component part values of the filter components are increased or additional filter stages are connected in series to improve insertion loss at low frequencies, then the insertion loss is improved, but the component size increases
Solution Approach 1:
The patent achieves improved insertion loss without increasing component size by changing the circuit topology to include a resonant LC stage. The resonant frequency ω0 = 1/√(L1*C1) creates a pole that provides steep attenuation at low frequencies, eliminating the need for larger component values while maintaining the same physical footprint.
3Reliability
If a plurality of filter stages are used to achieve steeper insertion loss, then the insertion loss is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by concentrating the filtering action in a specific frequency region through the resonant pole at ω0 = 1/√(L1*C1). Instead of using multiple broad-stage filters, the invention creates a localized steep attenuation region that targets low-frequency common-mode interference effectively, reducing overall device complexity.
Solution Approach 2:
The patent uses electrical resonance to create a highly effective single-stage filter that replaces multiple filter stages. The resonant oscillation at frequency ω0 produces a pole in the transfer function that provides steep insertion loss characteristics, achieving the same effect as multiple stages but with simpler circuitry.
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 achieves insertion losses of up to 70 dB per frequency decade, reducing interference effectively across a range of frequencies while minimizing component size and complexity, making it suitable for applications in automotive and industrial sectors.
Implementation Method 1
The first auxiliary inductance is inductively coupled to the first main inductance... achieve improved insertion losses through series resonance
Implementation Method 2
the first auxiliary inductance is inductively coupled to the first main inductance
Data Source
AI summary
The present invention provides an electrical filter device (1) for filtering a common-mode interference between a current source and a load, comprising:—a signal input (E), which comprises at least one first terminal (E1) and can be connected to the current source; —a signal output (A), which can be connected to the load; —a main stage (H0), having a first main inductor (2a), which comprises a coil with a first core (3), the first main inductor (2a) being connected to the first terminal (E1); and—an auxiliary stage (H1), having at least one first anti-interference capacitor (C1) and one first auxiliary inductor (4), the first auxiliary inductor (4) being connected between the first terminal (E1) and the first anti-interference capacitor (C1), the first auxiliary inductor (4) being inductively coupled to the first main inductor (2a).