Digital optimization control method and system for synchronous rectification of LLC full bridge converter

Abstract

The invention provides a digital optimization control method and system for synchronous rectification of an LLC full bridge converter. The drain terminal voltage before and after the shut-off of a synchronous rectification tube at the full bridge LLC secondary side is respectively sampled; the twice sampling results are subjected to logic comparison through a comparator; a microcontroller regulates the shot-off time of the synchronous rectification tube at the full bridge LLC secondary side according to the logic comparison result; the precise sampling of the drain terminal voltage before and after the shut-off of the synchronous rectification tube at the full bridge LLC secondary side is realized by using the interruption matching of the microcontroller; the shut-off of the synchronous rectification tube at the full bridge LLC secondary side at the optimum shot-off time is realized through comparing the time command to be regulated given by the microcontroller in real time; and the whole efficiency of the full bridge LLC is improved.

Description

technical field [0001] The invention relates to an LLC resonant full-bridge switching converter adopting a synchronous rectification mode, in particular to a digital optimization control method and system for synchronous rectification of an LLC full-bridge converter. Background technique [0002] At present, the switching frequency in the LLC power converter is getting higher and higher, and the advantages brought by the increase of the switching frequency are as follows: ① The volume of the energy storage device (inductor, transformer, capacitor, etc.) in the circuit is correspondingly reduced. ②The power density of the whole circuit is further increased. However, the increase of switching frequency also brings about the increase of various switching losses and conduction losses, so synchronous rectification is widely used to replace diode rectification, especially in the case of high output current. [0003] At present, there are three types of synchronous rectification c...

AI Technical Summary

Problems solved by technology

②The power density of the whole circuit is further increased

Among them, the current detection technology is more accurate, but the energy loss of the resistance caused by the current detection is quite large, so it will affect the efficiency of the overall topology.

Detecting the drain terminal voltage of synchronous rectifiers has become the only efficient synchronous rectification control scheme. The analog voltage detection technology based on detecting the drain-source voltage of synchronous rectifiers has a very complicated circuit structure, which cannot meet the requirements of high power density. At the same time, This technique can lead to gate parasitic oscillations

The digital detection technology dominated by microcontrollers or FPGAs is currently a better source-drain voltage detection technology. At present, a relatively common synchronous rectification control scheme is mainly to detect whether the body diode of the synchronous rectifier is turned on. In general, the synchronous rectifiers are quickly and adaptively turned off, but this scheme is mainly affected by the switching between diode conduction and reverse conduction, which will reduce the efficiency of the entire LLC circuit, and the corresponding delay problem is at high frequencies. It will be more serious

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