A digital optimization control method and system for synchronous rectification of llc full-bridge converter

Abstract

A digital optimization control method and system for synchronous rectification of an LLC full-bridge converter, respectively sampling the drain terminal voltages of the synchronous rectifiers on the secondary side of the full-bridge LLC before and after they are turned off, and comparing the two sampling results According to the logic comparison result, the microcontroller adjusts the turn-off time of the full-bridge LLC secondary synchronous rectifier tube and uses the interrupt cooperation of the microcontroller to realize the drain terminal voltage before and after the LLC secondary synchronous rectifier tube is turned off. Accurate sampling, through real-time comparison of the time command that needs to be adjusted given by the microcontroller, the full-bridge LLC secondary side synchronous rectifier is turned off at the best time, and the overall efficiency of the full-bridge LLC circuit 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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