Power Factor Correction Converter Phase-Modulated Switching
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Solution Overview
Problem
Conventional PFC converters face challenges in adapting to a wide range of input voltages, leading to significant variations in switching frequency, which results in increased inductor size and switching losses, and fails to effectively disperse EMI noise across a wide frequency range.
Innovation Solution
A PFC converter design that modulates the switching frequency based on the phase of the AC input voltage waveform, using a phase detecting circuit and switching frequency modulating circuit to adjust the frequency within a half cycle, reducing switching losses and preventing inductor saturation, while dispersing EMI noise across a lower frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the switching frequency is increased to reduce inductor size, then the inductor size is reduced, but switching losses increase
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The switching frequency is dynamically adjusted based on the instantaneous value of the input voltage, increasing when voltage is high and decreasing when voltage is low. This dynamic adaptation allows the inductor size to be optimized for high voltage conditions while minimizing switching losses during low voltage operation, resolving the contradiction between inductor size reduction and switching loss minimization.
Solution Approach 2:
The patent changes the parameter of switching frequency based on input voltage conditions. By modulating the switching frequency according to the instantaneous input voltage value, the system optimizes the trade-off between inductor size and switching losses. The inductor size is determined by the maximum switching frequency used, while the actual switching losses depend on the average frequency, which is reduced during low voltage periods.
2Adaptability or versatility
If the switching frequency is significantly varied to adapt to wide input voltage ranges, then adaptability is improved, but inductor size increases to prevent saturation
Solution Approach 1:
The patent uses dynamic switching frequency adjustment adapted to input voltage ranges. Rather than designing for the worst-case scenario across all voltage ranges, the system dynamically adapts the switching frequency to the current voltage condition. This allows the inductor to be sized for the specific operating range rather than the entire possible range, reducing inductor size while maintaining adaptability through frequency modulation.
3Device complexity
If the switching frequency is fixed at a given value, then the control is simple, but EMI noise with high peak value occurs
Solution Approach 1:
The patent applies periodic action by modulating the switching frequency according to the periodic nature of the AC input voltage. The switching frequency follows the rhythm of the input voltage waveform, creating a periodic variation pattern. This periodic modulation disperses EMI noise across a frequency spectrum while maintaining a controlled, predictable pattern that doesn't significantly increase system complexity.
Solution Approach 2:
The patent changes the switching frequency parameter in response to input voltage variations. By modulating the frequency according to the instantaneous voltage value, the system disperses EMI noise across a wider frequency range rather than concentrating it at a single frequency, reducing peak EMI levels while using relatively simple voltage-detecting and frequency-modulating circuits.
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 solution allows for optimal switching frequency operation across a wide range of input voltages, reducing inductor size and weight, minimizing switching losses, and improving efficiency by shifting the modulation range to lower frequencies when input voltage peaks, thus enhancing adaptability and reducing EMI noise.
Implementation Method 1
an inductor (L1) arranged to pass a current interrupted by the switching circuits
Implementation Method 2
a smoothing circuit arranged to smooth an output voltage from the inductor
Data Source
AI summary
A power factor correction converter includes a diode bridge arranged to perform full-wave rectification on an AC input power supply, a switching element arranged to perform switching on an output voltage thereof, an inductor arranged to pass a current interrupted by the switching element and to accumulate and emit excitation energy, a diode, and a smoothing capacitor defining a step-up chopper circuit. A digital signal processing circuit detects a phase of an input voltage, and a switching frequency of the switching element is modulated in accordance with the phase. Accordingly, the switching frequency can be appropriately modulated without depending on an input voltage, so that a wide range of input voltages can be accepted while suppressing EMI noise with a peak generated in the switching frequency and higher-order frequency components thereof.