Flyback Synchronous Rectification Control for Resonance Mis-Triggering
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Solution Overview
Problem
Synchronous rectification in flyback switching power supply systems increases complexity and adversely affects reliability and stability due to mis-triggering during resonance, leading to inefficiencies and operational disorders.
Innovation Solution
A system and method for synchronous rectification that determines if the input voltage becomes lower than a predetermined threshold, distinguishing between demagnetization and resonance processes to prevent unnecessary transistor switching, thereby maintaining accurate control and reducing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectification is implemented in flyback switching power supply systems, then power conversion efficiency is improved and heat generation is reduced, but system complexity increases and reliability deteriorates due to mis-triggering during resonance
Solution Approach 1:
The control circuit performs preliminary detection of the secondary winding voltage before triggering the synchronous rectification transistor. By detecting whether the voltage has dropped to a predetermined threshold level, the circuit determines the appropriate timing for transistor activation, preventing mis-triggering during resonance periods and ensuring reliable operation while maintaining high efficiency
2Difficulty of detecting and measuring
If synchronous rectification control circuits directly detect secondary winding voltage, then detection is simplified, but mis-triggering occurs during resonance causing operational disorders
Solution Approach 1:
The control circuit performs preliminary detection of the secondary winding voltage before triggering the synchronous rectification transistor. By detecting whether the voltage has dropped to a predetermined threshold level, the circuit determines the appropriate timing for transistor activation, preventing mis-triggering during resonance periods and ensuring reliable operation while maintaining high efficiency
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
Enhances the reliability and efficiency of flyback switching power supply systems by preventing mis-triggering during resonance, improving power conversion efficiency and system stability.
Implementation Method 1
a transformer (e.g., T1) including a primary winding (e.g., L1) and a secondary winding (e.g., L2)
Implementation Method 2
a synchronous rectification (SR) switch (e.g., M2)... the second transistor terminal being connected to a secondary winding of the power converter
Data Source
AI summary
System and method for synchronous rectification of a power converter. For example, the system for synchronous rectification includes: a first system terminal configured to receive an input voltage; and a second system terminal configured to output a drive signal to a first transistor terminal of a transistor, the transistor further including a second transistor terminal and a third transistor terminal, the second transistor terminal being connected to a secondary winding of the power converter, the power converter further including a primary winding coupled to the secondary winding; wherein the system is configured to: determine whether the input voltage becomes lower than a predetermined voltage threshold; and if the input voltage becomes lower than the predetermined voltage threshold, determine whether a time when the input voltage becomes lower than the predetermined voltage threshold is during or not during a demagnetization process of the secondary winding.