PFC Converter Control Using Squared Input Voltage Reference
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Solution Overview
Problem
Existing power factor correction (PFC) converter systems fail to efficiently convert input current to follow input voltage, leading to inefficiencies and harmonic distortions, particularly in active PFC circuits due to switch operations.
Innovation Solution
A reference controller modulates switch conduction based on the square of the input voltage and output current, using a gain adjuster to adjust the error amplifier gain, mitigating zero crossing distortion and improving waveform quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switches are employed in active PFC circuits to change current waveform, then power factor is improved, but switch operations consume power and reduce efficiency
Solution Approach 1:
The patent employs feedback control through a controller that monitors the input voltage and adjusts the switch conduction duty cycle accordingly. The controller generates a duty cycle signal based on the squared input voltage waveform, creating a closed-loop system that maintains optimal power factor correction while minimizing unnecessary switch operations.
Solution Approach 2:
The patent dynamically adjusts the switch conduction duty cycle in real-time based on the instantaneous input voltage. By making the duty cycle variable and adaptive to the input voltage conditions, the system optimizes power factor correction efficiency while reducing redundant switching losses.
2Reliability
If conventional PFC control is used, then basic power factor correction is achieved, but zero crossing distortion occurs and waveform quality deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by pre-distorting the reference waveform to anticipate and compensate for zero crossing distortion. The controller generates a duty cycle signal that proactively counteracts the expected distortion effects before they occur, thereby maintaining waveform quality throughout the voltage cycle including the zero crossing region.
Solution Approach 2:
The patent changes the control parameter from linear voltage following to squared voltage following. By using the square of the input voltage as the basis for duty cycle modulation, the system fundamentally alters the control characteristic to eliminate zero crossing distortion and improve overall waveform quality.
3Reliability
If input current is forced to follow input voltage directly, then power factor improves, but harmonic distortions increase
Solution Approach 1:
The patent transforms the control approach by using the squared input voltage waveform instead of the direct voltage waveform for duty cycle modulation. This parameter transformation fundamentally changes the current waveform characteristics, achieving power factor correction while inherently filtering out harmful harmonics through the mathematical transformation.
Data Source
AI summary
In a described example, a circuit can include a reference controller and a gain adjuster. The reference controller is configured to sample an input voltage from an input stage of the circuit and generate a modulation signal based on a square of the input voltage and an output current of an output stage of the circuit using an error amplifier. The modulation signal is configured to modulate conduction of a switch of a power factor correction (PFC) converter of the circuit to cause an average output current of the output stage of the circuit to follow a reference proportional to the square of the input voltage. The gain adjuster is configured to adjust a gain of the error amplifier based on the input voltage.