Flyback Converter Short-Circuit Shutdown via Auxiliary Winding Sensing
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Solution Overview
Problem
Asymmetrical half-bridge flyback converters face challenges in detecting short-circuits at the output terminal, which can lead to increased resonant current, potential damage to switches, and generation of voltage spikes.
Innovation Solution
Incorporating a short-circuit indicating circuit that samples the auxiliary winding voltage of the transformer and provides a short-circuit indicating signal, which is then processed by a short-circuit processing circuit to control the switches and stop the converter operation when a short-circuit is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional asymmetrical half-bridge flyback converter operation continues during output short-circuit, then the converter maintains power transfer function, but switch damage and voltage spikes occur
Solution Approach 1:
The control circuit proactively monitors the auxiliary winding voltage and detects short-circuit conditions before they can cause damage to the switches. By detecting the abnormal voltage drop across the auxiliary winding and immediately responding by shutting down the converter, the system prevents the harmful effects of continued operation during short-circuit conditions.
Solution Approach 2:
The control circuit continuously monitors the auxiliary winding voltage and uses this feedback to detect short-circuit conditions. When the monitored voltage indicates a short-circuit (abnormal drop or zero voltage during expected operation), the control circuit responds by shutting down the converter, thereby preventing switch damage and voltage spikes.
2Reliability
If short-circuit detection is added to the converter, then switch protection is improved, but circuit complexity increases
Solution Approach 1:
The auxiliary winding of the transformer serves multiple functions: it provides voltage feedback for regulation and now also serves as the sensing element for short-circuit detection. By utilizing the existing auxiliary winding for dual purposes, the invention avoids adding separate detection hardware, thereby maintaining simplicity while achieving comprehensive protection.
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
Effectively prevents damage to switches by promptly stopping the converter operation when a short-circuit is detected, thereby ensuring reliable operation and extending the lifespan of components.
Implementation Method 1
The transformer has a primary winding, a secondary winding and an auxiliary winding. The primary winding is coupled to a switching terminal between the first switch and the second switch.
Data Source
AI summary
A control circuit for an asymmetrical half-bridge flyback converter is provided. The control circuit includes a short-circuit indicating circuit and a short-circuit processing circuit. The short-circuit indicating circuit receives an auxiliary winding voltage of a transformer of the asymmetrical half-bridge flyback converter and provides a short-circuit indicating signal based on the auxiliary winding voltage. The short-circuit processing circuit receives the short-circuit indicating signal and provides at least one short-circuit control signal to control the asymmetrical half-bridge flyback converter based on the short-circuit indicating signal. The short-circuit control signal controls the asymmetrical half-bridge flyback converter to stop operating when the short-circuit indicating signal indicates that an output terminal of the asymmetrical half-bridge flyback converter is short-circuited.