Power Factor Correction Stage With Dynamic Switching Timing
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Solution Overview
Problem
Existing power factor correction (PFC) stages require large electromagnetic interference (EMI) filters and have power limitations when used with high-power devices, such as servers, due to fixed switching frequency operations that do not efficiently manage EMI emissions.
Innovation Solution
A power factor correction stage with a controller that operates switches of additional converter stages at varying times corresponding to a proportion of the previous switching cycle, reducing EMI emissions and allowing for dynamic adjustments based on input/output voltage and other parameters, thereby reducing the need for large EMI filters and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If switches of converter stages are operated at equal divisions of switching frequency, then the control is simple and stable, but EMI emissions are high and efficiency is reduced
Solution Approach 1:
The patent applies dynamics by making the switching timing of converter stages variable rather than fixed. The controller dynamically adjusts the switching instants based on the actual switching cycle duration, which varies with load conditions. This dynamic adjustment optimizes EMI performance across different operating points while maintaining manageable control complexity through a systematic approach.
Solution Approach 2:
The patent changes the timing parameter of switch operation from fixed equal divisions to variable proportions of the actual switching cycle. By adjusting the proportion parameter based on measured switching cycle duration, the system achieves reduced EMI emissions without requiring completely new control architecture, thus balancing performance improvement with control simplicity.
2Object-generated harmful factors
If fixed switching frequency operation is used, then the control is simple, but EMI emissions are high and require large EMI filters
Solution Approach 1:
The patent changes the switching timing parameter from fixed to variable based on actual cycle duration. This parameter change reduces EMI emissions across different operating conditions, which directly reduces the required EMI filter size while maintaining simple control architecture.
Solution Approach 2:
The patent converts the potentially harmful effect of variable switching timing into a benefit by using the actual switching cycle measurement to optimize the switching instants. This approach turns what could be a source of EMI complexity into a mechanism for EMI reduction, thereby reducing filter requirements.
3Power
If conventional PFC stages are used, then the design is straightforward, but power limitations occur with high-power devices
Solution Approach 1:
The patent applies segmentation by dividing the power conversion function into multiple parallel converter stages instead of using a single converter. This segmentation allows the system to handle higher power levels by distributing the load across multiple stages, while the coordinated control based on actual switching cycles maintains efficiency and reduces EMI.
Solution Approach 2:
The patent merges multiple converter stages in parallel operation with coordinated switching control. By combining the stages and synchronizing their operation based on actual switching cycle measurements, the system achieves enhanced power handling capability while maintaining control simplicity and reducing overall EMI emissions.
Data Source
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AI summary
A power factor correction stage comprising: an input terminal configured to receive an input signal; an output terminal configured to provide an output signal; a first converter stage and one or more further converter stages, wherein each of the converter stages is connected to the input terminal and the output terminal, and each converter stage comprises a switch; and a controller configured to operate the switches of the converter stages. The controller is configured to operate the switch of the one or more further converter stages at a period of time after operation of the switch of the first converter stage for a current switching cycle, wherein the period of time corresponds to a proportion of the switching frequency for an earlier switching cycle that does not correspond to substantially the period of the earlier switching cycle divided by the number of converter stages.