Switch Mode Power Supply Spread Spectrum Noise Reduction
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Solution Overview
Problem
Switch mode power supplies experience noise issues due to switching, with existing spread spectrum technologies like frequency hopping and frequency ramping either failing to adequately reduce noise or generating additional noise in the time domain, affecting performance.
Innovation Solution
Implementing a 'random frequency walk' by varying the instantaneous switching frequency at a constant slew rate with random direction changes, controlled by a signal generated from integrating a random bit stream, filtered by a low-pass filter to minimize peak spectral noise and maintain current mode control loop regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If frequency hopping is used to change the switching frequency, then the birdie at switching frequency is reduced, but the current mode feedback loop needs to settle to a new peak current after each frequency hop, impairing power supply performance
Solution Approach 1:
The patent applies dynamics by transitioning from static frequency hopping to dynamic frequency sweeping. The switching frequency is continuously varied in a controlled manner rather than hopping between discrete frequencies, creating a dynamic spread spectrum effect that reduces birdies while maintaining loop stability through predictable frequency evolution
Solution Approach 2:
The patent changes the frequency parameter continuously over time using a sweep function rather than discrete hops. This parameter change approach allows the system to explore frequency variations smoothly, reducing peak spectral noise while maintaining adequate loop response time for the feedback mechanism to adapt
Data Source
AI summary
A switch mode power supply may utilize a switching signal to control one or more power switches in the switch mode power supply. A switch mode power supply controller may generate and/or control this switching signal. The controller may reduce the peak spectral noise of the switch mode power supply by varying the instantaneous switching frequency at a constant slew rate magnitude that changes sign at random times. The instantaneous switching frequency may be controlled by a signal that is generated by integrating a random bit stream. The stream may repeat at a sub-audio frequency. The integrator may be lossy, so that the output does not wonder off to an arbitrary value. The frequency modulation signal may be filtered by a low pass filter.