Asymmetric Power Factor Correction Circuit for EMI Filter Distortion
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Solution Overview
Problem
Power factor correction circuits with switch mode power supplies and EMI filters experience distortion in input current due to phase differences, leading to deteriorated power factor and waveform distortion.
Innovation Solution
A power factor correction circuit that includes a filter capacitor and a power switch, with an adjustment signal generator to control the switching operation of the power switch asymmetrically based on the input voltage peak, and a duty generator to correct filter currents and generate feedback signals for compensating the distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an EMI filter with filter capacitor is added to the power factor correction circuit, then electromagnetic interference is reduced, but the input current waveform becomes distorted and power factor deteriorates
Solution Approach 1:
The patent applies asymmetry by generating an adjustment signal that is asymmetric with respect to the input voltage peak. This asymmetric adjustment signal is added to the PWM signal to compensate for the symmetric distortion caused by the filter capacitor, thereby correcting the input current waveform while maintaining EMI filtering functionality
Solution Approach 2:
The patent uses feedback by detecting the input voltage and generating an adjustment signal based on the detected voltage characteristics. The adjustment signal is fed back to the PWM signal generation stage to dynamically compensate for the filter capacitor's effect on the input current waveform
2Stability of the object's composition
If the filter capacitor is used to smooth the input voltage, then voltage ripple is reduced, but the filter current creates phase difference and distorts the input current
Solution Approach 1:
The patent applies preliminary action by generating the adjustment signal in advance based on the detected input voltage characteristics. This adjustment signal is prepared before being added to the PWM signal, allowing proactive compensation for the filter capacitor's phase-shifting effect rather than reacting to the distortion after it occurs
Data Source
AI summary
A power factor correction circuit corrects a filter current flowing through a filter capacitor asymmetrically based on a peak of an input voltage by controlling a switching operation of a power switch, thereby correcting distortion of an input current.