Adaptive synchronous rectification control system and method for llc resonant converter

Abstract

The present invention relates to an adaptive synchronous rectification control system and method of an LLC resonant converter. The system includes: a sampling circuit, the input end of which is connected to the drain of a synchronous rectifier for collecting the drain voltage of the synchronous rectifier; A comparator, the input end of which is connected to the output end of the sampling circuit, is used to compare the input drain voltage with a preset voltage threshold and output a comparison result; the control unit is connected with the comparator and the synchronous rectifier The gate connection is used to control the conduction time of the synchronous rectifier in one working cycle. The present invention can make a direct judgment on the drain terminal voltage of the synchronous rectifier, thereby obtaining whether the synchronous rectifier is in the best shutdown state, and accordingly performs shutdown control on the synchronous rectifier to adjust to a suitable shutdown state. point. The method adopts an adaptive synchronous rectification algorithm, and can realize self-adaptive control of the conduction time of the synchronous rectifier according to the change trend of the switching frequency of the primary switch tube.

Description

technical field [0001] The invention relates to synchronous rectification technology, in particular to an adaptive synchronous rectification control system and method of an LLC resonant converter. Background technique [0002] As an excellent topology, the LLC resonant converter has become a recognized and widely used power topology. Since the LLC resonant converter can realize the zero-voltage turn-on of the power tube on the primary side and the zero-current turn-off of the rectifier diode on the secondary side in a wide load range, it has the characteristics of higher working efficiency and higher switching frequency compared with the hard switching topology. [0003] However, when the LLC resonant converter works under heavy load conditions, due to the conduction voltage drop of the secondary rectifier diode, a large current flows through the rectifier diode, resulting in a large energy loss after passing through the rectifier diode, which reduces the working efficiency ...

AI Technical Summary

Problems solved by technology

When the synchronous rectifier is turned off earlier than the optimum turn-off point, the current will flow through the body diode of the synchronous rectifier, increasing the loss of the synchronous rectifier; when the synchronous rectifier is turned off later than the optimum turn-off point, the secondary side The current will affect the working state of the resonant tank on the primary side of the LLC resonant converter, causing the distortion of the resonant current

In the prior art, there is a lack of a synchronous rectifier control method that can well solve the above problems

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