Switching Power Converter Feedback Averaging for Power Factor Correction
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Solution Overview
Problem
Conventional single-stage AC-DC switching power converters experience a lowered power factor due to distortion in the peak input current profile caused by low-frequency ripple in the feedback control signal, leading to an out-of-phase relationship with the rectified input voltage.
Innovation Solution
A feedback loop controller that averages the feedback signal over each cycle of the rectified input voltage to prevent low-frequency ripple in the control signal, ensuring the peak input current remains in-phase with the rectified input voltage, thereby improving power factor correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback loop control is used to regulate output voltage, then output voltage regulation is achieved, but low-frequency ripple in the feedback control signal causes distortion in the peak input current profile, lowering power factor
Solution Approach 1:
The feedback signal is segmented and processed cycle-by-cycle with respect to the rectified input voltage. By detecting zero-crossing times and processing feedback signals in discrete cycles, the system isolates low-frequency ripple while maintaining regulation, thereby resolving the contradiction between reliable voltage regulation and power factor degradation.
Solution Approach 2:
The patent implements periodic action by averaging the feedback signal over complete cycles of the rectified input voltage. This periodic processing synchronizes with the input voltage frequency, eliminating low-frequency ripple that causes current distortion while preserving the essential regulation function, thus improving power factor without sacrificing voltage regulation reliability.
2Object-generated harmful factors
If peak current control methodology is used to shape input current in-phase with rectified input voltage, then power factor is improved, but low-frequency ripple in feedback signal still causes distortion in current profile
Solution Approach 1:
The patent applies feedback by continuously monitoring the output voltage and comparing it with a reference, then using this information to adjust the power switch cycling. The feedback signal is processed through cycle-by-cycle averaging to eliminate ripple, ensuring that the peak current control maintains both high power factor and accurate current profile without distortion.
Solution Approach 2:
The patent changes the parameter processing method by transforming the feedback signal from raw instantaneous values to averaged cycle-by-cycle values. This parameter transformation filters out low-frequency ripple while preserving the regulatory function, allowing the peak current control to maintain both high power factor and accurate current profiling.
3Reliability
If feedback loop responds to low-frequency ripple in control voltage signal, then output voltage regulation is maintained, but peak input current profile becomes distorted and out-of-phase with rectified input voltage
Solution Approach 1:
The patent applies preliminary action by pre-processing the feedback signal through cycle-by-cycle averaging before it reaches the control voltage generation stage. This preliminary filtering removes low-frequency ripple that would otherwise cause phase misalignment, allowing the system to maintain both voltage regulation and proper current-voltage phase alignment.
Solution Approach 2:
The patent introduces an intermediary processing stage between the feedback signal and the control voltage generation. This intermediary averages the feedback signal over complete input voltage cycles, acting as a mediator that preserves voltage regulation while eliminating the harmful ripple that causes phase misalignment between current and voltage.
Data Source
AI summary
The feedback loop of a switching power converter controller is provided with an averaging circuit that averages either an output voltage, an error signal, or a control voltage. Regardless of which feedback signal is averaged, the averaging occurs over a first cycle of a rectified input voltage to form an averaged signal that is used by the feedback loop in a subsequent cycle of the rectified input voltage.