Flyback Converter Short-Through Prevention via Pulse Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional flyback power converters face issues with short-through problems due to the secondary winding being conductive while the primary winding is still conductive, leading to potential damage, especially in continuous conduction mode.
Innovation Solution
A flyback power converter design that generates ON and OFF pulse signals at the secondary side of the transformer, which are transmitted to the primary side to determine the start and end conduction time points of the primary winding, utilizing a controller and driver to control the synchronous rectification switch and power switch, preventing short-through by ensuring the primary winding is non-conductive when the secondary winding is conductive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectification is used to improve power conversion efficiency, then power conversion efficiency is improved, but short-through damage may occur when primary and secondary windings are simultaneously conductive
Solution Approach 1:
The patent applies preliminary action by generating the ON pulse signal before the primary winding becomes conductive, and generating the OFF pulse signal before the primary winding becomes non-conductive. This timing arrangement ensures that the synchronous rectification switch is already in the correct state before the primary winding changes state, preventing simultaneous conduction and eliminating the short-through risk while maintaining high power conversion efficiency
Solution Approach 2:
The patent uses feedback by detecting the actual conduction state of the primary winding and using this information to control the timing of the synchronous rectification switch. The controller monitors the primary winding current and adjusts the switch timing accordingly, ensuring the switch is turned off before the primary winding current reaches zero, thus preventing short-through while maximizing efficiency
2Productivity
If continuous conduction mode is used to improve productivity, then productivity is improved, but the risk of short-through increases due to extended conduction overlap
Solution Approach 1:
In continuous conduction mode, the patent applies preliminary action by generating the OFF pulse signal in advance based on predicted primary winding current zero-crossing points. The controller calculates the expected timing of current zero-crossings and提前 generates the OFF pulse signal to ensure the synchronous rectification switch is turned off before the primary winding becomes non-conductive, maintaining high productivity while preventing short-through damage
Solution Approach 2:
The patent applies dynamics by continuously adjusting the timing of the OFF pulse signal based on the actual operating conditions and primary winding current characteristics. The controller dynamically modifies the switch timing to match the real-time conduction state, allowing optimal performance in continuous conduction mode while adaptively preventing short-through conditions
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
This design effectively prevents short-through issues by accurately controlling the conduction times of the primary and secondary windings, enhancing the reliability and efficiency of the flyback power converter.
Implementation Method 1
a transformer, which includes: a primary winding, configured to operably receive an input voltage; and a secondary winding, configured to operably generate an output voltage
Data Source
AI summary
The present invention provides a flyback power converter and a control circuit thereof. The flyback power converter includes a transformer, a power switch, a driver, a synchronous rectification (SR) switch, a controller, and a signal coupler circuit. The transformer has a primary winding and a secondary winding. The power switch controls the conduction time of the primary winding; and the SR switch controls the conduction time of the secondary winding. The controller controls the SR switch and generates an ON pulse signal and an OFF pulse signal in a normal operation mode. When an output voltage reaches a lower limit voltage, the flyback power converter operates in the normal operation mode. The driver generates a switching signal according to the ON pulse signal and the OFF pulse signal in the normal operation mode, to determine a start conduction time point and an end conduction time point of the primary winding.