Switching Regulator Frequency Stepping for Spur Reduction
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Solution Overview
Problem
Switching regulators with fixed switching frequencies generate high spurious noise and harmonics, limiting their performance in applications requiring low noise and high current, such as RF applications.
Innovation Solution
A method and circuit for a switching regulator that adjusts the switching frequency and compensation voltage dynamically to reduce spurious noise by subtracting a delta value from the error amplifier's output, stabilizing the compensation voltage and preventing modulation of the output voltage with the sweep frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed switching frequency is used in the switching regulator, then the regulator can operate stably and efficiently, but high spurious noise and harmonics are generated at the switching frequency and its harmonics
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The control circuit dynamically adjusts the switching frequency around a center frequency, creating a spread spectrum effect that distributes the spurious noise energy across a frequency range instead of concentrating it at a single frequency, thereby reducing peak noise levels while maintaining operational stability
Solution Approach 2:
The patent changes the frequency parameter from a fixed value to a varying value with a specific probability distribution. By modifying the switching frequency parameter according to a controlled distribution centered at a center frequency, the system reduces spurious noise at any single frequency while maintaining overall operational reliability
2Object-generated harmful factors
If the switching frequency is varied to reduce spurious noise, then noise performance improves, but the error amplifier output and compensation voltage become unstable
Solution Approach 1:
The patent implements feedback by using the error amplifier to continuously monitor the output voltage and adjust the compensation voltage accordingly. This feedback mechanism ensures that even when the switching frequency varies, the compensation voltage remains stable by dynamically compensating for any deviations, thus maintaining both noise reduction and voltage stability
Solution Approach 2:
The patent introduces a compensation voltage as an intermediary element between the error amplifier output and the switching control. This intermediary compensation voltage absorbs the variations caused by frequency modulation, preventing them from directly affecting the switching devices and thereby decoupling the frequency variation from the voltage stability requirement
Data Source
AI summary
Described herein is a switching regulator that can provide a high current while operating with low noise and low spur. The switching regulator may operate with a varying switching frequency. Spurs at the varying switching frequency may be reduced by compensating an error amplifier, which controls the switching frequency.