Synchronous Rectification Pulse Control for Burst Mode Conduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In power conversion apparatuses using synchronous rectification transistors, the transition time from high to low voltage levels during burst mode can cause abnormal conduction states, affecting efficiency.
Innovation Solution
A synchronous rectification circuit that includes control and comparison circuits to automatically determine burst mode entry and adjust pulse width based on drain voltage, preventing abnormal conduction by aligning pulse signal periods with voltage level changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power conversion apparatus enters burst mode to reduce switching times and improve efficiency, then power conversion efficiency is improved, but the transition time of drain voltage becomes longer causing abnormal conduction state
Solution Approach 1:
The pulse width of the control signal is dynamically adjusted based on the detected transition time of the drain voltage. The control circuit extends the pulse width when long transition time is detected, ensuring the synchronous rectification transistor remains properly controlled throughout the extended transition period, thus preventing abnormal conduction while maintaining burst mode efficiency benefits
Solution Approach 2:
The control circuit detects the transition time of the drain voltage from high to low level and uses this feedback information to adjust the pulse width of the control signal. This closed-loop feedback mechanism ensures the control signal duration matches the actual voltage transition characteristics, preventing abnormal conduction states while maintaining optimal efficiency
2Reliability
If the pulse width is extended to cover the longer transition time in burst mode, then abnormal conduction is avoided, but the number of switching times increases reducing efficiency
Solution Approach 1:
The control circuit changes the pulse width parameter of the control signal based on the detected transition time characteristics. By dynamically adjusting this parameter, the circuit ensures proper transistor control during voltage transitions without unnecessarily increasing switching frequency, thus maintaining efficiency while preventing abnormal conduction
Data Source
AI summary
A power conversion apparatus and a synchronous rectification circuit thereof are provided. A control circuit determines whether the power conversion apparatus enters a burst mode based on a time when a drain voltage of a synchronous rectification transistor is lower than a preset voltage, and adjusts a pulse width of a pulse signal generated by a pulse signal generating circuit.