Interleaved Multi-Level Converter EMI Reduction
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Solution Overview
Problem
Multi-level switching converters face challenges in regulating flying capacitor voltage and exhibit tone for input current conducted electromagnetic interference (EMI) at half the switching frequency, leading to increased radiated EMI and design complexities.
Innovation Solution
An interleaved multi-level converter architecture with two parallel multi-level switching circuits, sharing an input voltage node, a switch node, and an inductor, driven by the same set of switching signals, which eliminates the half switching frequency tone for input current conducted EMI and reduces current density and radiated EMI by halving the maximum voltage swing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multi-level switching converters are used to reduce switching loss and increase effective switching frequency, then power device ratings can be reduced and individual devices can operate at lower frequencies, but tone for input current conducted EMI at half the switching frequency is generated and flying capacitor voltage regulation becomes difficult
Solution Approach 1:
The patent divides the single multi-level switching converter into two parallel multi-level switching circuits, each operating at a slightly offset frequency. This segmentation eliminates the half-switching-frequency tone by distributing the switching events across different time instances, thereby reducing conducted EMI while maintaining the benefits of reduced switching loss and lower individual device stress.
Solution Approach 2:
The patent employs periodic switching actions with deliberately introduced frequency offsets between the two parallel circuits. By operating each circuit at a periodic frequency that is slightly different from the other, the system maintains continuous power conversion while avoiding the resonant buildup of EMI at half the switching frequency that occurs in single-circuit designs.
2Productivity
If multi-level switching converters are used to achieve higher effective switching frequency, then lower rated power devices can be used, but flying capacitor voltage regulation becomes complex and design challenges increase
Solution Approach 1:
The patent segments the flying capacitor voltage regulation task across two parallel circuits, where each circuit handles a portion of the regulation burden. This segmentation simplifies the control complexity for each individual circuit while maintaining the high effective switching frequency benefits, as each circuit operates independently with its own simplified regulation scheme.
Solution Approach 2:
The patent changes the operating parameters of the two parallel circuits by introducing frequency offsets and phase differences. This parameter modification allows the system to achieve high effective switching frequency while simplifying flying capacitor voltage regulation, as the offset frequencies prevent synchronized switching events that would complicate voltage management.
3Object-generated harmful factors
If parallel multi-level switching circuits are used to eliminate half switching frequency tone, then current density and radiated EMI are reduced, but circuit complexity increases
Solution Approach 1:
The patent merges two multi-level switching circuits in parallel configuration, sharing common components such as the input voltage node, switch node, and inductor. This merging approach reduces radiated EMI by distributing current paths and reducing voltage swings, while the shared components minimize the overall circuit complexity increase compared to fully separate designs.
Solution Approach 2:
The patent implements universal components that serve multiple functions: the shared inductor handles current smoothing for both circuits, the common switch node facilitates voltage regulation for both paths, and the parallel configuration simultaneously achieves EMI reduction and high effective switching frequency. This multi-functionality offsets the added circuit complexity.
Data Source
AI summary
Described systems, methods, and circuitries use an interleaved multi-level converter to convert an input signal received at an input node into an output signal at an output node. In one example, a power conversion system includes a first multi-level switching circuit, a second multi-level switching circuit, and a control circuit. The first multi-level switching circuit and the second multi-level switching circuit are coupled to a switching node, the input node, and a reference node. The control circuit is configured to generate, based on the output signal, switching control signals as pulse width modulated signals having a duty cycle to control the output signal and provide the switching control signals to the first multi-level switching circuit and the second multi-level switching circuit.