Two-Stage AC-DC Converter with Isolated PFC Stage
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Solution Overview
Problem
Conventional AC-DC voltage converters face challenges in reducing circuit power losses, improving transmission efficiency, and minimizing product costs and circuit volume due to high voltage requirements and complex control mechanisms.
Innovation Solution
A two-stage AC-DC voltage converter design is implemented, featuring a first stage with isolated topology for power factor correction and a second stage with non-isolated topology, where the second stage only converts part of the output voltage, using switches with lower withstand voltages and smaller volumes, and employing PWM control for fast regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional AC-DC voltage converters use high voltage switches to convert the entire output voltage, then the voltage conversion is complete, but the circuit power losses increase and the circuit volume increases
Solution Approach 1:
The patent divides the voltage conversion process into two stages: first stage converts AC input voltage to intermediate DC voltage, second stage converts only the excess voltage to the final regulated output. This segmentation allows each stage to operate at lower voltage levels, reducing power losses while achieving complete voltage conversion.
Solution Approach 2:
The second stage voltage converter only converts part of the intermediate voltage (the excess amount) to the final output voltage, rather than converting the entire voltage. This partial action reduces the stress on switches and lowers power losses in the second stage.
2Reliability
If conventional AC-DC voltage converters use high voltage switches, then the voltage conversion is reliable, but the product costs increase and circuit volume increases
Solution Approach 1:
By segmenting the voltage conversion into two stages with different topologies, the patent enables the use of lower voltage-rated switches in the second stage, which have smaller physical dimensions and lower cost, while maintaining overall system reliability through the coordinated operation of both stages.
Solution Approach 2:
The patent changes the voltage parameter requirements for switches by using an isolated topology in the first stage that provides galvanic isolation and voltage transformation, allowing the second stage to operate with lower voltage switches. This parameter change enables cost reduction and volume reduction without sacrificing reliability.
3Loss of energy
If conventional AC-DC voltage converters use full voltage conversion in one stage, then the conversion is simple, but the transmission efficiency decreases
Solution Approach 1:
The two-stage architecture segments the conversion function, allowing the first stage to handle power factor correction and voltage transformation with high efficiency, while the second stage handles only the regulation of the excess voltage. This segmentation improves overall transmission efficiency despite increased structural complexity.
Solution Approach 2:
The first stage isolated topology performs multiple functions: power factor correction, voltage transformation, and galvanic isolation. This multi-functionality allows the second stage to focus solely on voltage regulation, improving overall efficiency while the complexity is managed through functional integration in the first stage.
4Reliability
If conventional AC-DC voltage converters use optical couplers for isolation, then the galvanic isolation is achieved, but the response speed decreases and cost increases
Solution Approach 1:
The patent replaces optical couplers with magnetic coupling through a transformer in the isolated topology. This substitution eliminates the limitations of optical couplers (slow response, higher cost) while maintaining galvanic isolation, as the transformer provides both isolation and fast magnetic coupling for control signal transmission.
Solution Approach 2:
The patent changes the isolation mechanism from optical to magnetic coupling. The transformer-based isolation provides both galvanic isolation and fast response through magnetic field coupling, eliminating the need for optical couplers and their associated response time limitations.
Data Source
AI summary
The present invention discloses circuits and methods for high efficiency and fast response AC-DC voltage converters. In one embodiment, an AC-DC voltage converter can include: (i) a first stage voltage converter having an isolated topology with a power factor correction function, where the first stage voltage converter is configured to convert an AC input voltage to a series-connected N branches of first stage voltages, where N is a positive integer of at least two; (ii) a second stage voltage converter having a non-isolated topology, where the second stage voltage converter is configured to convert one of the N branches of the first stage voltages to a second stage voltage; and (iii) where the second stage voltage and a remaining of the N branches of the first stage voltages are configured to be series-connected and converted to a DC output voltage.