A synchronous rectification circuit and its control method

Abstract

Disclosed are a control circuit and a control method for a synchronous rectification circuit. The synchronous rectification circuit includes an energy storage element having a primary winding and a secondary winding, a primary switch coupled to the primary winding, a synchronous rectification switch coupled to the secondary winding, and a synchronous rectification control circuit. The synchronous rectification control circuit provides a driving signal to control the synchronous rectification switch, and the synchronous rectification control circuit judges whether the synchronous rectification switch is in the off state by judging whether the drain-source voltage is greater than the value of the dynamic threshold signal, and the synchronous rectification switch is in the off state premise Next, the synchronous rectification switch is controlled to turn on according to the drain-source voltage at both ends of the synchronous rectification switch. Wherein the dynamic threshold signal is obtained according to the maximum value of the sample-and-hold drain-source voltage, and the synchronous rectification control circuit further controls the dynamic threshold signal to follow the maximum value of the drain-source voltage through a leakage circuit, so as to timely cope with the drain-source voltage Periodic changes and transient changes of circuit parameters such as input voltage.

Description

Technical field [0001] Embodiments of the present invention relates to an electronic circuit, more particularly, to a synchronous rectifier switch control circuit and a control method thereof. Background [0002] With the development of electronic technology, synchronous rectifier circuits are widely used in notebook power adapters, wireless communication equipment, LCD power management, Ethernet power and other occasions with high conversion efficiency requirements due to their high conversion efficiency. [0003] Synchronous rectification circuits typically receive the input voltage on the primary side of the transformer, while on the secondary side of the transformer use controllable switching tubes (synchronous rectifier switches) instead of diodes to convert the input voltage into the desired output voltage. Typically, its topology includes, for example Figure 1 The flyback converter shown. [0004] Synchronous rectification schemes usually control the opening and shutdown...

AI Technical Summary

Problems solved by technology

In practical applications, the drain-source voltage will change with the change of some circuit parameters (such as input voltage), how to set the detection threshold of the drain-source voltage and accurately control the on-off of the synchronous rectification switch has become a problem

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