Variable-Gain AC-DC Converter Control for Wide-Range PFC Output
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Solution Overview
Problem
Existing AC-DC converters struggle to maintain optimal performance over a wide range of input and output voltage variations, leading to inefficiencies in applications like electric vehicle charging.
Innovation Solution
A controller for an AC-DC converter that operates in multiple modes, including high-gain, low-gain, and zero-gain modes, to adjust the rectifier circuit's gain based on input voltage and output voltage requirements, ensuring power factor correction and a wide range of DC output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single operating mode is used for the rectifier circuit, then the circuit design is simple, but the converter cannot maintain optimal performance over a wide voltage variation range
Solution Approach 1:
The rectifier circuit dynamically switches between different operating modes (full-bridge, half-bridge, non-operating) based on the instantaneous AC input voltage level. This dynamic adaptation allows the circuit to maintain optimal performance across a wide voltage range (90V to 264V) while managing complexity through controlled mode transitions rather than designing for all conditions simultaneously
Solution Approach 2:
The invention changes the operating parameters of the rectifier circuit by switching between different bridge configurations (full-bridge, half-bridge) and operating states (operating, non-operating). These parameter changes enable the circuit to adapt its gain characteristics to match the input voltage level, resolving the contradiction between adaptability and complexity
2Adaptability or versatility
If the AC input voltage and DC output voltage have large variations, then the application range is wide, but the efficiency of the converter significantly decreases
Solution Approach 1:
The controller dynamically selects the appropriate operating mode based on real-time monitoring of AC input voltage and DC output voltage levels. This dynamic control ensures the rectifier operates in the most efficient mode for each voltage condition, preventing efficiency degradation across the full application range
Solution Approach 2:
The wide voltage range is segmented into different operating regions, each handled by a specific mode: full-bridge mode for low voltage conditions requiring high gain, half-bridge mode for medium voltage conditions, and non-operating mode for high voltage conditions. This segmentation allows optimal efficiency in each region while maintaining wide overall adaptability
3Reliability
If a boost converter is used for power factor correction, then the output voltage is higher than peak AC voltage, but an additional DC-DC converter is needed for voltage conversion
Solution Approach 1:
The rectifier circuit is designed to perform multiple functions: power factor correction, voltage conversion, and output regulation. By making the rectifier universal and capable of operating in multiple modes with different gain characteristics, the need for a separate dedicated DC-DC converter stage is eliminated, reducing overall system complexity while maintaining reliable power factor correction
Data Source
AI summary
A controller for an AC-DC converter including a rectifier circuit that converts AC input voltage into DC output voltage uses control logic to control the rectifier circuit according to two or more operating modes. Each operating mode determines a gain of the rectifier circuit. The controller selects an operating mode from the two or more operating modes based on at least one of an AC input voltage value and a required DC output voltage value. The AC-DC converter provides a wide range of DC output voltage with power factor correction. The controller may be used with AC-DC converter topologies such as boost converter, isolated boost converter, PWM converter, LLC resonant converter, and LCC resonant converter.