Digital Spread Spectrum EMI Mitigation in Power Converters
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Solution Overview
Problem
Existing solutions for mitigating electromagnetic interference (EMI) in switched mode power supplies (SMPS) are limited to analog feedback controllers and are either costly or increase system size, failing to effectively address EMI in digitally controlled systems.
Innovation Solution
A digital circuit architecture using a pseudo-random pattern generator and a delay-line digital pulse width modulator to create a digital spread spectrum, varying the switching frequency and reducing EMI by spreading noise across a wide range of frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive EMI mitigation techniques (EMI snubbers) are used, then EMI effects are reduced, but system cost and size increase
Solution Approach 1:
The patent changes the switching frequency parameter dynamically using spread spectrum modulation techniques. By varying the switching frequency around a nominal value according to a pseudo-random sequence, the EMI energy is distributed across a wider frequency range, reducing peak emissions without requiring additional passive components like snubbers.
Solution Approach 2:
The patent replaces passive mechanical/electrical EMI mitigation components (snubbers, filters) with an active control system implemented in digital domain. The EMI reduction is achieved through software-controlled frequency modulation rather than physical passive components, reducing both cost and system size.
2Object-affected harmful factors
If switching frequency is varied to reduce EMI, then radiated and conducted EMI is spread across frequency domain, but implementation is limited to analog feedback controllers
Solution Approach 1:
The patent substitutes analog control mechanisms with digital control implementation. The spread spectrum frequency modulation is achieved through digital signal processing techniques including pseudo-random sequence generation and digital modulation of the switching controller, making it compatible with digitally controlled power converters.
Solution Approach 2:
The patent creates a universal EMI mitigation solution that can be applied to both analog and digital feedback controllers. The digital implementation provides flexibility to work with various controller architectures while maintaining the core spread spectrum frequency variation mechanism.
3Volume of moving object
If system size is decreased to improve compactness, then portability is improved, but EMI susceptibility increases
Solution Approach 1:
The patent dynamically changes the switching frequency parameter to spread EMI emissions. This allows compact system design without requiring increased spacing between components, as the frequency modulation reduces peak EMI levels that would otherwise require greater physical separation to mitigate.
Data Source
AI summary
A spread spectrum system having a self-oscillating delay-line digital pulse width modulator and a method for mitigating electromagnetic interference. The spread spectrum system has a pseudo-random pattern generator connected to a digital-to-analog converter, which in turn is connected to a linear regulator. The linear regulator receives a reference voltage from the digital-to-analog converter and creates a frequency varying voltage that serves as an input voltage for delay elements of a delay-line based digital pulse width modulator. In response to frequency varying input signal, the delay-line based digital pulse width modulator generates a frequency varying voltage that is input to a switching network to vary its switching frequency.