PFC Control Circuit Ripple Elimination for Transient Response
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Solution Overview
Problem
Conventional power factor correction (PFC) circuits face a trade-off between slow transient response and input current distortion, and require large DC-link capacitance, which increases costs.
Innovation Solution
A control method for a PFC conversion device that includes a rectification circuit, a power factor correction circuit, a ripple calculation circuit, and a pulse width modulation circuit, which eliminates second-order ripple components from feedback signals to enhance response speed and reduce current distortion, thereby increasing the power factor sent to a back-end load and minimizing DC-link capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the bandwidth of the voltage loop is increased to speed up transient response, then the transient response speed is improved, but the input current waveform distortion increases
Solution Approach 1:
The patent segments the feedback signal by separating the second-order ripple component from the main feedback voltage signal using a ripple calculation circuit. This allows independent processing of the ripple component through subtraction, enabling the voltage loop to respond quickly to load changes without allowing ripple-induced current distortion
Solution Approach 2:
The patent extracts the second-order ripple component from the feedback signal using a dedicated ripple calculation circuit that generates a ripple signal based on the input voltage. This extracted ripple signal is then subtracted from the main feedback signal, removing the harmful ripple effects while preserving the essential voltage regulation function
2Stability of the object's composition
If large-capacity capacitors are connected in parallel to reduce DC-link voltage ripple, then the DC-link voltage stability is improved, but the current distortion increases and power factor decreases
Solution Approach 1:
The patent implements a feedback mechanism where the ripple calculation circuit continuously monitors the input voltage and generates a corresponding ripple signal. This ripple signal is subtracted from the feedback voltage in real-time, creating a corrected feedback signal that maintains DC-link voltage stability without requiring large capacitance that would cause current distortion
Solution Approach 2:
The patent changes the parameter of the feedback signal by subtracting the calculated ripple component, transforming the feedback voltage from a signal containing second-order ripple to a clean signal. This parameter modification allows the system to achieve voltage stability through control rather than through large passive capacitance
Data Source
AI summary
A power factor correction conversion device and control method thereof are adapted to send an AC signal to a power factor correction conversion device, convert the AC signal into a DC signal, and perform power factor correction of the DC signal, so as to change a power factor sent to a back-end load, wherein the control method includes a rectification step, a feedback step, a ripple calculating step, a ripple offsetting step, a logical computation step, a pulse width modulation step and a power factor correcting step. Hence, the second-order ripple component in a feedback signal is eliminated to thereby increase the response speed of the power factor correction conversion device and reduce the distortion rate of the current, thus increasing the power factor sent to the back-end load.