Switch Control Circuit for Power Factor Corrector THD Reduction
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Solution Overview
Problem
Conventional power factor correctors experience ampere total harmony distortion due to input voltage ratio-dependent input current distortion, which is not sinusoidal, leading to increased waveform differences and distortion near zero and peak current regions.
Innovation Solution
A switch control circuit that senses zero crossing voltage and feedback voltage to control the turn-on and turn-off times of a power switch, restricting the switching frequency to a predetermined threshold, thereby reducing ampere total harmony distortion by synchronizing the power switch operations with zero crossing detection signals and sawtooth wave comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the input voltage ratio is increased in a conventional power factor corrector, then the switching frequency increases, but the input current waveform distortion increases and deviates from sinusoidal shape
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable and adaptive rather than fixed. The control circuit dynamically adjusts the switching frequency based on real-time detection of input voltage and current waveforms, allowing the system to optimize performance across varying operating conditions while maintaining sinusoidal current shape and reducing THD.
Solution Approach 2:
The patent implements feedback mechanisms where the control circuit continuously monitors the input current waveform and compares it against the desired sinusoidal shape. Based on this feedback, the controller adjusts the switching frequency to minimize waveform distortion and maintain power factor correction performance.
2Loss of energy
If the duty cycle is adjusted to maintain critical conduction mode, then the power factor corrector operates efficiently, but the input current becomes distorted near zero and peak current regions
Solution Approach 1:
The patent changes the operating parameters by transitioning from a fixed critical conduction mode to a variable conduction mode. The control circuit adjusts the duty cycle and switching frequency dynamically based on the operating point, allowing the system to maintain efficiency while correcting the waveform distortion that occurs in fixed-mode operation, particularly near zero and peak current regions.
3Speed
If the switching frequency is increased to improve response speed, then the power factor correction responds faster to voltage changes, but the ampere total harmony distortion increases
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable and adaptive rather than fixed. The control circuit dynamically adjusts the switching frequency based on real-time detection of input voltage and current waveforms, allowing the system to optimize performance across varying operating conditions while maintaining sinusoidal current shape and reducing THD.
Data Source
AI summary
The present invention relates to a switch control circuit, a power factor corrector including the same, and a driving method thereof. According to an exemplary embodiment of the present invention, a turn-on time of a power switch is controlled according to a zero crossing voltage to sense a voltage of both terminals of the power switch, and a turn-off time of the power switch is controlled according to a feedback voltage corresponding to the output voltage. At this time, the switching frequency of the power switch is sensed by the zero crossing voltage and the switching frequency is restricted by a predetermined threshold frequency.