EMI Filter Parallel Capacitor Frequency Compensation
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Solution Overview
Problem
Conventional EMI low-pass filters struggle to achieve strong rejection band attenuation and high cut-off frequency while maintaining a small footprint, as they face design trade-offs between low insertion loss and broad pass-band requirements, leading to parasitic effects that compromise signal integrity in electronic devices like smartphones.
Innovation Solution
Incorporating at least one parallel capacitor into EMI LPF filter circuits, such as π-type CRC and CLC filters, for frequency compensation, which enhances rejection band attenuation without increasing filter size, and maintains high cut-off frequency by connecting the parallel capacitor in parallel with passive elements between input and output terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional EMI LPF filters are designed with traditional RC or LC configurations, then the filter structure remains simple and compact, but the rejection band attenuation is insufficient and the roll-off curve is not steep enough
Solution Approach 1:
The patent introduces parallel capacitors connected across the inductor in the LC filter configuration, changing the electrical parameters of the filter circuit. This modification creates additional frequency-dependent impedance paths that enhance high-frequency attenuation while maintaining the basic filter structure and compact form factor.
2Object-affected harmful factors
If multiple-stage filters are used to improve rejection band attenuation, then the attenuation performance improves, but the filter size and device complexity increase
Solution Approach 1:
The patent combines multiple filtering functions into a single-stage configuration by introducing parallel capacitors that work together with the existing inductor and series capacitors. This merging of functions achieves multi-stage attenuation performance without requiring physically separate filter stages, thereby reducing overall filter size and device complexity.
3Area of stationary object
If the cut-off frequency is increased to broaden the pass band, then more baseband signals can pass through, but the rejection band attenuation becomes weaker
Solution Approach 1:
The patent applies different impedance characteristics to different frequency ranges by configuring the parallel capacitors with specific capacitance values. The capacitor network provides low impedance paths for high-frequency rejection band signals while maintaining high impedance for low-frequency pass band signals, thereby achieving frequency-selective attenuation that broadens the pass band without compromising rejection 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 proposed solution significantly improves high-frequency rejection band attenuation while maintaining low-frequency insertion loss, achieving a steeper roll-off curve and better signal integrity without increasing the filter size, thus addressing the limitations of conventional single-stage and multiple-stage filters.
Implementation Method 1
Incorporating at least one parallel capacitor into EMI LPF filter circuits, such as π-type CRC and CLC filters, for frequency compensation
Data Source
AI summary
An integrated electromagnetic interference (EMI) filter circuit with electrostatic discharge (ESD) protection and incorporating capacitors is provided. At least one passive element, i.e. resistor or inductor is connected between an input terminal and an output terminal. A first capacitor is connected between ground and the input terminal, and a second capacitor is connected between ground and the output terminal. A first diode and a second diode are connected in parallel to the first capacitor and the second capacitor. One or multiple parallel capacitors are connected in parallel to the passive element and between the input terminal and the output terminal for frequency compensation by employing the novel EMI LPF circuit, it is extraordinarily advantageous of enhancing its rejection band attenuation and meanwhile maintaining high cut-off frequency while implementation.