Asymmetric Half-Bridge Flyback Converter for Single-Stage AC/DC Isolation
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Solution Overview
Problem
Existing AC/DC converter systems for medium/low power applications face challenges in reducing size and cost while maintaining functionality, particularly in achieving high power factor rectification and DC/DC isolation, and realizing zero-voltage switch-on or zero-current switch-off (soft switching) in switching power supplies.
Innovation Solution
An asymmetric half-bridge flyback circuit-based converter is introduced, comprising a full-bridge rectifier circuit, a half-bridge circuit, a resonant circuit, a transformer, and a control circuit, which alternately switches the upper and lower bridge switches to convert AC input into DC output, achieving high power factor rectification and DC/DC isolation through the transformer, and implements soft switching by determining the on-duration of the lower bridge switch based on peak current and voltage values and transformer inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-stage circuit scheme is adopted for AC/DC conversion, then high power factor rectification and DC/DC isolation functions are achieved, but system size and cost increase
Solution Approach 1:
The patent merges the high power factor rectification function and DC/DC isolation function into a single integrated circuit stage. The asymmetric half-bridge flyback converter combines the rectifier circuit and isolating converter circuit, eliminating the need for separate BOOST-based PFC circuit and high-frequency resonant half-bridge converter circuit, thereby reducing system size while maintaining both functions
Solution Approach 2:
The asymmetric half-bridge flyback converter is designed to perform multiple functions simultaneously: it acts as both a high power factor rectifier and an isolating DC/DC converter. The circuit can operate in different modes (CCM and DCM) to achieve both power factor correction and voltage isolation in a single stage, making the system more versatile and compact
2Reliability
If a two-stage circuit scheme is adopted for AC/DC conversion, then high power factor rectification and DC/DC isolation functions are achieved, but system cost increases
Solution Approach 1:
The patent merges the rectifier circuit and isolating converter circuit into a single asymmetric half-bridge flyback converter, reducing the total number of circuit components. This integration eliminates redundant elements and reduces bill of materials cost, making the system more cost-effective while maintaining both high power factor rectification and DC/DC isolation functions
Solution Approach 2:
The asymmetric half-bridge flyback converter is designed to perform multiple functions simultaneously: it acts as both a high power factor rectifier and an isolating DC/DC converter. By consolidating multiple functions into one circuit topology, the patent reduces component count and manufacturing complexity, thereby lowering system cost
3Device complexity
If conventional switching is used in switching power supplies, then circuit simplicity is maintained, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent employs periodic resonant action in the asymmetric half-bridge flyback converter. The resonant circuit creates periodic oscillations that enable zero-voltage switching (ZVS) or zero-current switching (ZCS) conditions, allowing switches to turn on or off when voltage or current is naturally zero, thereby minimizing switching losses while maintaining controlled operation
Solution Approach 2:
The patent changes the operating parameters of the switching circuit by introducing resonant elements and operating in specific modes (CCM and DCM). By adjusting the switching frequency and utilizing resonant phenomena, the circuit achieves soft switching conditions that reduce switching losses without significantly increasing circuit complexity
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 converter achieves high power factor rectification and DC/DC isolation in a single-stage configuration, reducing system size and cost, and enables soft switching, improving efficiency by minimizing switching losses.
Implementation Method 1
The transformer is configured to convert the AC on the primary side of the transformer into an AC having a preset voltage value on a secondary side
Implementation Method 2
The resonant circuit is configured to perform auxiliary communication on the primary side of the transformer
Data Source
AI summary
An asymmetric half-bridge flyback circuit-based converter is provided. The converter is configured to convert an alternating current (AC) input at an AC input end into a direct current (DC) within a preset voltage value range. The converter includes a full-bridge rectifier circuit, a half-bridge circuit, a resonant circuit, a transformer, a load output circuit, and a control circuit.