Switching Regulator Resonant Circuit Ripple Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching regulators produce a ripple component in their output voltage that can corrupt analog signals, requiring additional filtering which often necessitates multiple stages and intermediate buffering, making it difficult to achieve sufficient attenuation, especially when aligning notch filters with the fundamental frequency of the ripple.
Innovation Solution
An integrated resonant circuit within a switching regulator IC that matches the resonant notch frequency with the fundamental frequency of the ripple component, providing far greater attenuation than traditional low pass filters and allowing for manual or automatic tuning to achieve up to 30 dB of ripple reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional low pass filters are used to attenuate ripple, then filtering is provided, but attenuation is insufficient (only 12 dB/octave) and multiple stages with intermediate buffering are required to achieve 30 dB attenuation
Solution Approach 1:
The patent applies resonant circuit theory to create a notch filter that targets the specific ripple frequency. By tuning the resonant frequency of the LC circuit to match the switching frequency, the system creates a deep notch (theoretical infinite attenuation) at the ripple frequency, achieving 30 dB attenuation with a single stage rather than multiple cascaded low pass filters
Solution Approach 2:
The patent changes the filtering approach from broad-spectrum low pass filtering to frequency-selective notch filtering by adjusting the resonant parameters (L and C values) to match the specific ripple frequency. This parameter optimization allows single-stage filtering to achieve the attenuation level that would otherwise require multiple stages
2Object-affected harmful factors
If cascaded filter stages are used to achieve 30 dB attenuation, then ripple attenuation is improved, but intermediate buffering is required increasing device complexity
Solution Approach 1:
By using resonant oscillation at the specific ripple frequency, the system creates a targeted notch filter that achieves deep attenuation (30 dB) in a single stage. The resonant circuit naturally provides the necessary filtering action without requiring cascaded stages or intermediate buffering amplifiers
3Object-affected harmful factors
If notch-type filter is used to attenuate ripple, then attenuation at fundamental frequency is improved, but aligning resonant notch with ripple frequency is difficult
Solution Approach 1:
The patent incorporates frequency detection and feedback mechanisms that allow the resonant circuit to automatically track and lock onto the switching frequency. This feedback system monitors the ripple frequency and adjusts the resonant parameters accordingly, making frequency alignment automatic rather than manual, thus simplifying manufacturing and ensuring optimal performance
Solution Approach 2:
The resonant circuit is designed to work with the switching regulator's inherent clock signal, making the filtering system adaptive to different operating conditions. The same circuit serves both the switching regulation and frequency-tracking functions, eliminating the need for separate alignment procedures
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 integrated resonant circuit achieves significant ripple attenuation, providing a more effective solution than conventional filtering methods by ensuring the resonant notch aligns with the ripple's fundamental frequency, resulting in a strongly attenuated output voltage with minimal additional components or buffering.
Implementation Method 1
an inductor and a capacitor connected in parallel to form a resonant circuit having an associated notch filter frequency response, the switching regulator circuitry and the resonant circuit housed within a common IC package
Data Source
AI summary
A switching regulator IC contains both switching regulator circuitry and an inductor and a capacitor connected in parallel to form a resonant circuit having an associated notch filter frequency response arranged such that, when connected to receive the regulated output voltage, the resonant circuit attenuates the ripple component. This is accomplished by matching the resonant notch to the ripple's fundamental frequency, either manually or automatically. In addition, the resonant circuit's inductor and capacitor can act in concert with decoupling capacitors coupled to the load to form a low pass filter which attenuates harmonics of the ripple's fundamental frequency.