Resonant Converter Synchronous Rectification Control
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Solution Overview
Problem
Resonant converters experience increased conduction loss when operating at frequencies higher than the resonant frequency, leading to inefficiencies in power conversion.
Innovation Solution
A resonant converter design that includes a switch control circuit capable of detecting the operation region based on voltage ringing and adjusting the conduction duration of synchronous rectification switches to minimize conduction loss, by extending the on-time of these switches beyond the primary switch off-time in the above resonance region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the resonant converter operates at a frequency higher than the resonant frequency, then the switching speed increases, but the conduction loss increases
Solution Approach 1:
The patent applies dynamics by making the conduction duration of synchronous rectification switches variable rather than fixed. The switch control circuit dynamically adjusts the conduction duration based on the detected operation region (below or above resonance), extending the conduction duration in the above resonance region to minimize conduction loss while maintaining high switching frequency operation.
Solution Approach 2:
The patent changes the parameter of conduction duration based on the operation region. By detecting whether the converter is operating above or below resonance and adjusting the conduction duration accordingly, the system optimizes efficiency across different operating conditions while maintaining high switching frequencies.
2Loss of energy
If the conduction duration of synchronous rectification switches is extended beyond primary switch off-time, then the conduction loss decreases, but the risk of primary-secondary switch overlap increases
Solution Approach 1:
The patent uses feedback by having the switch control circuit detect the operation region based on voltage waveform characteristics and use this information to adjust the conduction duration of synchronous rectification switches. This closed-loop control ensures that extension of conduction duration occurs only when safe, preventing primary-secondary switch overlap while minimizing conduction loss.
Solution Approach 2:
The system dynamically adjusts conduction duration based on real-time detection of operation region, making the rectification process adaptive to operating conditions while maintaining switching safety through controlled extension only when appropriate.
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 approach effectively reduces conduction loss by maintaining the synchronous rectification switches in an on-state longer after the primary switches have turned off, minimizing the duration of body diode conduction and enhancing overall efficiency.
Implementation Method 1
a resonant converter includes: a first switch on a primary side and a second switch coupled to the first switch; a first synchronous rectification switch on a secondary side conducted according to a switching operation of the first switch; a second synchronous rectification switch on the secondary side conducted according to a switching operation of the second switch
Implementation Method 2
A resonant converter is controlled so as to operate in an inductive region in a DC gain characteristic according to an operating frequency. The inductive region is classified based on the resonant frequency, into a below resonance region having a frequency lower than a resonant frequency and an above resonance region having a frequency higher than a resonant frequency
Data Source
AI summary
A resonant converter includes a first switch on a primary side and a second switch coupled to the first switch, a first synchronous rectification switch on a secondary side conducted according to a switching operation of the first switch, a second synchronous rectification switch on the secondary side conducted according to a switching operation of the second switch, and a switch control circuit configured to detect a waveform of one end voltage of at least one of the first synchronous rectification switch and the second synchronous rectification switch, determine one of a below region and an above region, and differently control conduction duration of the first and second synchronous rectification switches according to a determined result.