Drive circuit and method for driving synchronous rectifier and switching power supply for synchronous rectifier

Abstract

The invention discloses a drive circuit and method for driving a synchronous rectifier. The synchronous rectifier comprises a drain terminal, a source terminal and a gate terminal, wherein drain-source detection voltage is formed between the drain terminal and the source terminal of the synchronous rectifier; and gate voltage is formed on the gate terminal. When the drain-source detection voltagereaches set reference voltage, the gate voltage is reduced to keep the drain-source detection voltage at lower reference voltage. By using the drive circuit and method, the actual shutdown time of thesynchronous rectifier is closer to the ideal shutdown time, so that the synchronous rectifier can be more effectively prevented from being shut down by mistake; and furthermore, the drain-source detection voltage can be adjusted when being relatively high, and adjustment of the synchronous rectifier is easier to implement by using the same adjusting circuit.

Description

technical field [0001] This invention relates to electronic circuits and, more particularly, to synchronous rectification. Background technique [0002] In the synchronous rectification resonant converter, it is necessary to sample the drain-source voltage of the synchronous rectification MOS tube, and adjust the drain-source voltage through the regulating circuit to maintain it at a preset threshold, so as to ensure that the output voltage of the synchronous rectification resonant converter is as desired reach the target voltage. In addition, it is necessary to compare the drain-source voltage of the synchronous rectification MOS transistor with the reverse threshold voltage. When the drain-source voltage of the synchronous rectification MOS transistor reaches the reverse threshold voltage, the synchronous rectification MOS transistor needs to be turned off to prevent current reversal. Towards. [0003] The method of sampling the drain-source voltage of the MOS transistor...

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Problems solved by technology

[0006] However, although the above method can reduce false triggering operations, the effect is still not obvious, and a method that can effectively prevent false triggering is needed

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