Multilevel Buck-Boost Bridge Control for Low Common-Mode EMI
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Solution Overview
Problem
Power converters face challenges in minimizing ripple in inductors and reducing common mode electromagnetic interference (EMI) emission while achieving zero voltage switching and efficient power conversion.
Innovation Solution
A power converter system with a multi-level switch bridge, including a plurality of inductors, and a controller generating switching control signals to operate in quadrangular control mode, minimizing inductor ripple and reducing EMI through zero voltage switching and symmetrical modulation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional power converter topologies are used, then power conversion is achieved, but inductor ripple and common mode EMI emission are not minimized
Solution Approach 1:
The patent divides the conventional single-stage power converter into a two-stage architecture: a first power converter stage and a second power converter stage. This segmentation allows each stage to be optimized independently, with the first stage handling bulk power conversion and the second stage providing fine-tuned voltage regulation. The segmentation enables reduced inductor ripple and common mode EMI emission through coordinated control of both stages, while distributing the complexity across modular units rather than requiring a single complex converter design.
Solution Approach 2:
The patent introduces a temporal dimension to the power conversion process by implementing quadrangular control mode with four distinct switching states per cycle. This four-state switching sequence adds a time-based dimension to the conventional two-state switching, enabling the system to minimize inductor ripple and reduce common mode EMI emission through carefully timed voltage transitions. The quadrangular control pattern creates a more distributed switching profile that reduces peak currents and electromagnetic interference.
2Loss of energy
If inductor ripple is minimized, then power conversion efficiency is improved, but achieving zero voltage switching and reducing EMI becomes more challenging
Solution Approach 1:
The patent implements continuous voltage regulation across both converter stages to maintain optimal operating conditions. The first stage continuously adjusts its duty cycle to minimize inductor ripple, while the second stage simultaneously provides continuous fine-tuned regulation. This continuous coordinated control ensures that energy conversion efficiency is maximized throughout the entire operating range while the distributed switching action of both stages working together reduces common mode EMI emission compared to a single-stage system.
Solution Approach 2:
The patent dynamically changes multiple operating parameters including duty cycles of both converter stages, switching frequencies, and voltage levels to simultaneously minimize inductor ripple and reduce common mode EMI emission. The controller adjusts these parameters in real-time based on load conditions and input voltage variations, enabling the system to maintain high efficiency while minimizing electromagnetic interference through optimized switching waveforms and voltage transitions.
3Loss of energy
If zero voltage switching is achieved, then switching losses are reduced, but control complexity and switching sequence requirements increase
Solution Approach 1:
The patent implements preliminary action by using the first power converter stage to pre-condition the voltage and current waveforms before they reach the second stage. The first stage's switching action is timed to establish optimal voltage conditions that enable zero voltage switching in the second stage. This preliminary voltage conditioning reduces the switching losses in the second stage while the distributed control architecture manages the overall complexity by dividing the control functions between two independent but coordinated controllers.
Data Source
AI summary
Power systems including converters that exhibit reduced common mode voltage emissions are described. In one example, a power converter system includes an input and an output, a multi-level switch bridge coupled between the input and the output, an input capacitor branch coupled across the input, an output capacitor branch coupled across the output, and a controller configured to generate switching control signals for the multi-level buck-boost switch bridge. The multi-level switch bridge also includes a plurality of inductors in one example. In one case, a quadrangular or quadrangle control mode can be relied upon to switch the multi-level switch bridge, to minimize the ripple in the inductors, achieve zero voltage switching, reduce common mode electromagnetic interference emission by the converter, and for other benefits.