Switching Regulator Frequency Modulation Circuit

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Solution Overview

Problem

Existing spread spectrum frequency modulation techniques for switching regulators fail to effectively reduce the tilt of the spectral noise envelope and the 'horns' at frequency extremes, leading to high noise amplitudes at the output.

Innovation Solution

The development of frequency modulation circuits that generate a clock signal with a varying frequency modulated according to a waveform coordinated with the peak noise amplitude, reducing the tilt and 'horns' by compensating for the correlation between noise amplitude and operating frequency, and allowing for optional disablement of spread spectrum frequency modulation in favor of fixed frequency operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If sinusoidal frequency modulation is used to reduce spectral noise, then the noise is distributed across frequencies, but peaks or horns appear at frequency extremes reducing efficiency

Engineering Contradiction:

Improvespectral noiseVSAvoidnoise reduction efficiency

Core Design Contradiction:

Object-generated harmful factorsVSProductivity

Solution Approach 1:

The patent modifies the frequency modulation waveform parameters by using a linear ramp waveform instead of sinusoidal modulation, and coordinates the modulation depth and sweep rate with the peak noise amplitude waveform to eliminate horns at frequency extremes while maintaining noise distribution

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent dynamically adjusts the switching frequency continuously across the frequency range rather than using fixed sinusoidal modulation, allowing the frequency to sweep linearly from minimum to maximum and back, adapting to the noise characteristics at different frequencies

Inventive Principle:

Principle #15Dynamics

2Object-generated harmful factors

If filtering is used to reduce differential-mode noise, then noise attenuation is achieved, but additional components are required that are physically large

Engineering Contradiction:

Improvedifferential-mode noiseVSAvoidadditional components

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/filtering approach with an electrical/frequency-domain approach by using spread spectrum frequency modulation to reduce noise, eliminating the need for additional physical filtering components

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating frequency parameter dynamically over time to distribute noise energy, replacing the static filtering approach with dynamic frequency variation that achieves noise reduction without additional components

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7362191B2Methods and circuits for frequency modulation that reduce the spectral noise of switching regulators

Publication Date: 2008.04.22 ANALOG DEVICES INT UNLTD CO

AI summary

The present invention comprises methods and circuits for spread spectrum frequency modulation that reduce peak spectral noise at the outputs or inputs of switching regulators. More specifically, the present invention modulates the operating frequency of the switching regulator in accordance with a frequency modulation waveform having a shape coordinated to a peak noise amplitude waveform that describes the correlation between the operating frequency of a switching regulator and the peak noise amplitude at the regulator's input or output absent spread spectrum frequency modulation.