Synchronous Rectification Circuit with Current Examination for Resonance Converters
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Solution Overview
Problem
Current resonance converting apparatuses with synchronous rectification circuits face inefficiencies due to conduction losses and shutdown issues caused by parasitic inductance affecting the driving IC's ability to accurately control rectification transistors, leading to reduced power conversion efficiency, especially under light loading conditions.
Innovation Solution
The introduction of a switching signal from the primary side of the transformer to directly examine and drive rectification transistors, using a pair of rectification transistors and driving circuits connected to the transformer windings, allows for precise current sensing and generation of driving signals to improve rectification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If rectification transistors are used to replace rectification diodes in the synchronous rectification circuit, then conduction loss is reduced and rectification efficiency is improved, but parasitic inductance of the winding affects the driving IC's current examination accuracy, causing premature shutdown and reduced overall efficiency
Solution Approach 1:
The patent introduces a current examination circuit as an intermediary component between the rectification transistor and the driving IC. This circuit accurately detects the current flowing through the rectification transistor by examining the voltage across a current examination resistor, providing precise feedback signals to the driving IC without being affected by the parasitic inductance of the winding. This mediator resolves the contradiction by enabling accurate current measurement while maintaining the low conduction loss benefits of using rectification transistors.
2Device complexity
If the driving IC examines current indirectly through drain-source voltage of rectification transistors, then the circuit structure is simplified, but parasitic inductance causes examination errors and premature shutdown, reducing synchronous rectification efficiency
Solution Approach 1:
The current examination circuit serves as an intermediary that provides accurate current information to the driving IC without adding significant complexity. By examining the voltage across a small resistance in series with the rectification transistor, the circuit achieves precise current detection while maintaining a relatively simple structure. This intermediary approach resolves the contradiction between circuit simplicity and rectification efficiency.
Solution Approach 2:
The patent replaces the indirect voltage-based current examination method with a direct current examination approach using a current examination circuit. This substitution eliminates the influence of parasitic inductance on current measurement accuracy, allowing the driving IC to make accurate shutdown decisions based on actual current levels rather than distorted voltage signals.
3Ease of manufacture
If parasitic inductance of the winding is present in the circuit, then the circuit can function with standard components, but it affects the driving signal generation, causing shutdown in advance and reduced power conversion efficiency
Solution Approach 1:
The current examination circuit acts as an intermediary that isolates the driving IC from the effects of parasitic inductance. By providing accurate current feedback through this intermediary circuit, the system maintains standard component assembly while eliminating the harmful effects of parasitic inductance on shutdown timing and power conversion 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
This approach enhances the stability and efficiency of synchronous rectification, particularly under light loading or no loading conditions, by reducing conduction losses and improving the driving ability of the rectification process.
Implementation Method 1
a resonance converting apparatus with function of synchronous rectification... resonant circuit 92 includes a transformer Tr and is formed as an LLC-type resonant circuit... constituted of a resonance inductance Lr, a magnetizing inductance provided by the primary side of the transformer Tr, and a resonance capacitance Cr
Data Source
AI summary
Provided is a resonance converting apparatus. The resonance converting apparatus preferably includes a resonant circuit, a bridge-type converter, and a synchronous rectification circuit. In which the resonant circuit has a transformer. The bridge-type converter connects with a primary side of the transformer, and operates open or close according to a switching signal. The synchronous rectification circuit further includes a pair of rectification transistors and driving circuits. The driving circuits correspondingly connect with channels to the rectification transistors, and respectively examine the current passing through the rectification transistors. A sensing signal is then generated. In accordance with the switching signal and the sensing signal, a driving signal is generated for driving the rectification transistor. Consequently the apparatus can raise the efficiency of the resonance converting apparatus.