PFC Circuit Control for Zero-Voltage Switching Across Phase Angles
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Solution Overview
Problem
Conventional power factor correction circuits face challenges in achieving zero voltage switching and high efficiency due to varying input voltage ratios and frequency changes, leading to harmonic distortion and reduced power factor, especially at phase angles around zero degrees.
Innovation Solution
A power factor correction circuit that includes a rectifier circuit, a series connection of a reactor and control switch, and a synchronous rectification switch, with a control circuit that adjusts reverse excitation amounts to maintain zero voltage switching across all phase angles by controlling the ON time of these switches, using a fixed reverse current proportional to the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse current is calculated using a fixed numerical value proportional to input voltage, then zero voltage switching can be performed, but switching frequency becomes excessively high at phase angles around zero degrees leading to increased switching loss
Solution Approach 1:
The patent applies dynamics by making the reverse current proportional to the instantaneous input voltage rather than using a fixed value. This dynamic adjustment ensures that reverse current scales with voltage, maintaining zero voltage switching capability while preventing excessive switching frequency and loss at low voltage phases.
Solution Approach 2:
The patent changes the parameter of reverse current from a fixed numerical value to a variable value that is proportional to input voltage. This parameter change allows the system to adapt to varying voltage conditions, achieving zero voltage switching when needed while avoiding high switching loss when input voltage is low.
2Reliability
If reverse current is set to a fixed numerical value, then zero voltage switching can be achieved, but input current distortion occurs and power factor correction performance deteriorates
Solution Approach 1:
The patent uses dynamics by making reverse current proportional to instantaneous input voltage. This dynamic relationship ensures that reverse current varies with voltage, enabling zero voltage switching while maintaining smooth input current waveform and preventing distortion that would occur with fixed reverse current values.
Solution Approach 2:
The patent implements feedback by using the instantaneous input voltage as a reference to determine the appropriate reverse current magnitude. This feedback mechanism ensures that reverse current is appropriately scaled to voltage conditions, achieving zero voltage switching without causing input current distortion or poor power factor correction.
3Reliability
If switching frequency increases to maintain zero voltage switching at all phase angles, then zero voltage switching is achieved, but switching loss becomes conspicuous and efficiency decreases
Solution Approach 1:
The patent applies dynamics by making reverse current proportional to instantaneous input voltage rather than using a fixed value. This dynamic adjustment ensures that switching frequency remains appropriate across all phase angles, achieving zero voltage switching when needed while preventing excessively high switching frequency and associated losses at low voltage phases.
Solution Approach 2:
The patent changes the reverse current parameter from fixed to variable (proportional to input voltage), which dynamically adjusts switching frequency based on voltage conditions. This parameter change enables zero voltage switching at all phase angles while avoiding the high switching loss that would result from uniformly high switching frequency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The circuit achieves zero voltage switching at all phase angles with reduced switching loss and harmonic distortion, maintaining high efficiency and improved power factor correction, even with fluctuating loads.
Implementation Method 1
a reactor L and a control switch Q1 are connected in series to both ends of the rectifier circuit 2
Implementation Method 2
a synchronous rectification switch Q2 and an output capacitor C1 are connected in series
Data Source
AI summary
A power factor correction circuit includes a series circuit in which a reactor L and a control switch Q1 are connected in series to both ends of a rectifier circuit 2 that rectifies input voltage of an AC power supply, a series circuit in which a synchronous rectification switch Q2 and an output capacitor C1 are connected to two main terminals of the control switch, and a control circuit 10 that alternately turns on and off the control switch and the synchronous rectification switch so that output voltage of the output capacitor becomes a first predetermined value and controls ON time of the control switch so that a peak value of current flowing through the control switch is proportional to input voltage. The control circuit turns on and off the control switch and the synchronous rectification switch so as to adjust a reverse excitation amount for reverse excitation of the reactor by causing current flowing through the reactor to reversely flow from the output voltage side to the input voltage side, and the reverse excitation amount is adjusted to a second predetermined value regardless of input voltage Vi.