Interleaved Power Converter EMI Reduction via Random PWM
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Solution Overview
Problem
Interleaved power converters experience distortions in output waveforms due to pulse-width modulation (PWM), leading to electromagnetic interference (EMI) noise, which existing technologies have not adequately addressed.
Innovation Solution
A controller for an interleaved power converter system that generates PWM signals by randomly varying the period of a carrier signal from a nominal period, and phase shifting it, to minimize EMI by spreading high-frequency noise components across a wider frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pulse-width modulation (PWM) is used at a fixed switching frequency to convert AC voltage into DC voltage, then the power converter can operate efficiently with a determined switching frequency, but the output waveform becomes distorted and generates electromagnetic interference (EMI) noise
Solution Approach 1:
The patent applies dynamics by randomly varying the switching frequency of the PWM signals instead of using a fixed frequency. The controller randomly selects switching frequencies from a range around a nominal frequency, making the switching behavior dynamic and adaptive. This random frequency variation smears the EMI noise spectrum while maintaining efficient power conversion.
Solution Approach 2:
The patent changes the frequency parameter of the PWM signals by introducing random variations. Instead of operating at a single fixed frequency, the system varies the switching frequency within a defined range, which fundamentally alters the spectral characteristics of the output and reduces peak EMI emissions.
2Stability of the object's composition
If the switching frequency is fixed at a determined value, then the power converter operation is stable and predictable, but the EMI noise concentrates at specific frequencies creating peak amplitudes of distortion
Solution Approach 1:
The system maintains operational stability through controlled randomization. The switching frequency varies randomly but within bounded limits around a nominal value, ensuring stable overall operation while preventing concentrated EMI peaks. The interleaved structure further stabilizes the output by combining multiple phase legs.
Solution Approach 2:
The patent uses periodic interleaved switching patterns across multiple phase legs with random frequency variations. Each phase leg operates periodically but with randomized timing, which distributes EMI energy across frequency bands while maintaining the periodic power conversion function.
3Stability of the object's composition
If multiple phase legs are operated in an interleaved manner, then the output waveform continuity is improved, but the complexity of the control system increases
Solution Approach 1:
The patent segments the power conversion function into multiple interleaved phase legs, each handling a portion of the total power. This segmentation improves waveform continuity by overlapping the switching intervals of different phases, reducing gaps in the output waveform while distributing the control complexity across independent but coordinated modules.
Data Source
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AI summary
A power converter system includes an interleaved power converter 10 having a plurality of parallel-connected phase legs 16 between DC terminals and an AC terminal. A plurality of parallel-connected inductors L1, L2, L3 are each connected to one of the plurality of parallel-connected phase legs to provide a summed output of the parallel-connected phase legs to the AC terminal. A controller 14 generates PWM signals used to control the state of each of the plurality of phase legs by comparing a carrier signal to a reference signal, wherein a period of the carrier signal is randomly varied from a nominal period.