PWM Dithering Profiles for Multi-Band EMI Reduction
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Solution Overview
Problem
Existing dithering techniques for switched mode power supplies (SMPS) are not optimally effective across multiple frequency ranges, leading to inadequate reduction of peak electromagnetic interference (EMI) energy at both low and high frequencies, which can violate regulatory standards and affect system performance.
Innovation Solution
A dual random spread spectrum (DRSS) dithering technique is implemented, using a combination of analog and digital dithering signals to generate a pulse width modulation (PWM) signal, optimizing EMI reduction across both low and high frequency bands by modulating a first signal with a second signal, such as a pseudorandom spread spectrum (PRSS) signal, to create a dual random spread spectrum signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single dithering technique is used, then the circuit complexity is reduced, but the EMI reduction effectiveness is insufficient across multiple frequency bands
Solution Approach 1:
The patent combines analog dithering and digital dithering techniques into a unified dual random spread spectrum (DRSS) dithering circuit. The analog dithering component spreads EMI energy across a first frequency band while the digital dithering component spreads energy across a second frequency band, and both are merged to achieve comprehensive EMI reduction across multiple frequency bands simultaneously.
Solution Approach 2:
The DRSS dithering circuit is designed to perform multiple functions: it generates both analog and digital dithering signals, applies spread spectrum modulation across different frequency bands, and controls the switching frequency of the SMPS. This multi-functional design allows a single circuit to address EMI issues across the entire frequency spectrum without requiring separate dedicated circuits for each frequency band.
Data Source
AI summary
At least some aspects of the present disclosure provide for a system. In some examples, the system includes a pulse width modulation (PWM) generator configured to generate a PWM signal. The PWM generator generates the PWM signal by generating a first signal having a first dithering profile and a first frequency bandwidth, generating a second signal having a second dithering profile and a second frequency bandwidth greater than the first frequency bandwidth, modulating the second signal with the first signal to generate a dual random spread spectrum signal, and generating the pulse width modulation signal according to the dual random spread spectrum signal.