Spread Spectrum Switching Regulator Noise Reduction
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Solution Overview
Problem
Current switching regulators generate significant noise and electromechanical interference due to fast switching of current through inductive elements, and existing filters are only partially effective, adding cost and size to the system.
Innovation Solution
A spread spectrum switching regulator that modulates the frequency and slope of the ramp signal used in the feedback loop to spread the input power across multiple frequencies, reducing peak conducted noise by adjusting the drive signal to the switching element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast switching of current through inductive element is used in switching regulator, then efficient DC-to-DC power conversion is achieved, but significant noise and electromechanical interference are generated
Solution Approach 1:
The patent applies dynamics by modulating the switching frequency of the regulator around a center frequency rather than operating at a fixed frequency. This frequency modulation spreads the noise spectrum, reducing peak noise levels while maintaining efficient power conversion. The dynamic adjustment of switching timing creates a spread spectrum effect that addresses the noise problem without sacrificing conversion efficiency.
2Object-generated harmful factors
If filters are incorporated to reduce noise, then noise reduction is achieved, but cost and size of the system increase significantly
Solution Approach 1:
The patent converts the harmful concentrated noise into a beneficial spread spectrum signal. By intentionally modulating the switching frequency to spread the noise energy across a broader frequency range, the peak noise levels are reduced without requiring additional filtering components. This approach transforms the noise problem into a solved characteristic of the switching regulator itself.
3Productivity
If switching frequency is increased to improve power conversion, then conversion efficiency improves, but noise and EMI are intensified
Solution Approach 1:
The patent employs periodic modulation of the switching frequency around a center frequency. This periodic variation in switching timing creates a spread spectrum effect where the noise energy is distributed over time and frequency. The periodic nature of the modulation allows efficient power conversion to be maintained while the frequency spreading reduces peak EMI levels.
Data Source
AI summary
A spread spectrum switching regulator generally includes an reactive circuit portion coupled to the input terminal, a switching element coupled to the reactive circuit portion, and a control circuit portion coupled between the switching element and the output terminal. The switching element has a drive signal characterized by a duty cycle, and the reactive circuitry portion is configured to produce an output voltage at the output terminal responsive to the duty cycle of the drive signal. The control circuit portion is configured to spread the input power across multiple frequencies by adjusting the drive signal of the switching element, thereby reducing input current noise through spread spectrum techniques. The drive signal is responsive to a pseudo-randomly generated ramp signal.