Power Factor Correction Stages Using Segmented Frequency Operation
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Solution Overview
Problem
Conventional power converters face challenges in achieving high efficiency and power density due to the variability in operating conditions and the difficulty in implementing soft-switching at high frequencies, particularly in the switching frequency of the power factor correction stage, which leads to significant losses and large magnetic and capacitive components.
Innovation Solution
The design incorporates a Stacked Multiphase Asymmetrical Half Bridge topology with a multilevel converter stage, flying capacitors, and a dual-ratio bus converter approach to reduce inductor ripple currents, minimize passive component size, and achieve efficient power factor correction, utilizing lower voltage-rated switches for improved performance and reduced losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional power factor correction stages are used, then power factor correction is achieved, but switching losses increase and efficiency decreases at high frequencies
Solution Approach 1:
The power conversion system is divided into multiple independent stages: a first power conversion stage performing power factor correction at line frequency, and a second power conversion stage performing DC-DC conversion at high frequency. This segmentation allows each stage to operate at its optimal frequency, with the PFC stage avoiding high-frequency switching losses while the DC-DC stage achieves high power density through high-frequency operation.
Solution Approach 2:
The power factor correction function is extracted from the high-frequency DC-DC conversion stage and implemented as a separate pre-regulator stage operating at line frequency. This extraction eliminates the conflict between PFC requirements and high-frequency switching efficiency, allowing the main converter to operate continuously at high frequency with minimal switching losses.
2Productivity
If high frequency operation is implemented to increase power density, then power density increases, but switching losses increase and efficiency decreases
Solution Approach 1:
The system segments power conversion functions into two stages with different operating frequencies: the first stage operates at line frequency (50/60 Hz) for PFC, while the second stage operates at high frequency (kHz range) for DC-DC conversion. This allows the high-frequency stage to achieve high power density through miniaturized magnetic components while the PFC stage avoids high-frequency switching losses by operating at lower frequency.
Solution Approach 2:
The operating frequency parameter is changed between stages: the PFC stage uses line frequency to minimize switching losses, while the DC-DC stage uses high frequency to reduce the size of inductors and transformers, thereby achieving high power density without suffering from high-frequency switching losses in the PFC circuit.
3Device complexity
If a single stage performs both isolation and power factor correction, then device complexity is reduced, but operating condition variability increases and efficiency decreases
Solution Approach 1:
The converter is segmented into a first PFC stage without isolation and a second DC-DC stage with isolation transformer. This segmentation allows the PFC stage to focus solely on power factor correction with simplified circuitry, while the isolation stage handles galvanic separation and voltage transformation, with each stage optimized for its specific function to maximize overall efficiency.
Solution Approach 2:
While the patent uses separate stages, it merges the PFC and DC-DC stages into a single integrated power supply unit with coordinated control, achieving both functional separation for efficiency and system-level integration for compactness. The stages share common components such as the output capacitor and control circuitry, reducing overall device complexity while maintaining the efficiency benefits of staged operation.
Data Source
AI summary
The present application relates to switching power supplies and in particular to AC to DC switch mode power supplies, to methods of power factor correction for same and to devices and circuits that may be used generally in same. The application describes a number of multi-level approaches and circuits.