Soft-Switching AC-DC Converter Bridgeless Topology
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Solution Overview
Problem
Existing AC-DC converters face challenges in achieving high power conversion efficiency and power density due to high conduction losses, limited operating frequency, and difficulties in implementing isolation and bidirectional power flow, especially in bridgeless topologies.
Innovation Solution
A soft-switching, high-performance single-phase AC-DC converter using a high-frequency isolation transformer with a bridgeless single-stage power factor correction circuit, which reduces conduction losses and enables galvanic isolation, bidirectional power flow, and multiple DC outputs with a common AC side circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a full-bridge diode rectifier is used in AC-DC converters, then power factor correction is achieved, but conduction loss increases especially at low line voltage
Solution Approach 1:
The patent removes the input diode bridge from the conventional two-stage AC-DC converter topology, extracting the harmful component that causes high conduction loss. The bridgeless SEPIC topology achieves power factor correction without requiring the full-bridge rectifier, thereby eliminating the associated conduction losses while maintaining the essential PFC function.
Solution Approach 2:
The patent combines the rectification function and power factor correction function into a single integrated stage using the bridgeless SEPIC topology. By merging these functions, the converter eliminates the need for separate rectifier and PFC circuitry, reducing the number of semiconductor components in the line current path and thereby reducing conduction loss.
2Loss of energy
If bridgeless boost-type rectifier is used to reduce conduction loss, then number of semiconductor components is reduced, but input-output isolation cannot be easily implemented
Solution Approach 1:
The patent introduces a high-frequency isolation transformer as an intermediary component in the bridgeless SEPIC topology. This transformer provides the necessary galvanic isolation between input and output while maintaining the bridgeless architecture that reduces conduction loss. The isolation transformer acts as a mediator that enables isolation functionality without requiring additional semiconductor components or complex circuitry.
3Loss of energy
If hard-switched non-isolated bridgeless SEPIC PFC rectifier is used, then conduction loss is reduced, but switching frequency is limited to less than 100 kHz due to high switching loss
Solution Approach 1:
The patent implements soft-switching techniques that create periodic zero-voltage switching conditions throughout each switching cycle. By utilizing resonant circuits and auxiliary switches, the converter achieves periodic intervals where switching occurs at zero voltage, significantly reducing switching losses and enabling operation at frequencies above 100 kHz while maintaining low conduction loss.
4Volume of moving object
If high-frequency switching is implemented to increase power density, then size of passive components is reduced, but switching loss increases
Solution Approach 1:
The patent converts the potentially harmful effect of high-frequency switching into a beneficial outcome by implementing soft-switching techniques. The resonant circuits and auxiliary switching mechanisms transform what would normally be high-loss hard switching events into low-loss soft switching events, allowing the converter to operate at high frequencies that reduce passive component size while maintaining low overall switching loss.
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 achieves significant efficiency improvements, reduced electromagnetic interference, and increased power density by enabling soft switching at high frequencies and simplifying the design for a wide range of input and output voltages, while minimizing the size of passive components and reducing ground leakage currents.
Implementation Method 1
a first coil comprising a first terminal coupled to the first AC I/O node and a second terminal; and a second coil magnetically coupled to the first coil
Data Source
AI summary
A soft-switching, high-performance single-phase alternating current (AC)-direct current (DC) converter is provided. The AC-DC converter described herein provides a new circuit topology for single-stage, single-phase or multi-phase AC-DC power conversion with power factor correction (PFC) and galvanic isolation using a high-frequency isolation transformer. The AC-DC converter improves power conversion efficiency and power density—two of the most important metrics for a power converter. It achieves soft switching for high frequency switches in the circuit, leading to higher efficiency and lower electromagnetic interference (EMI).