Synchronous rectification control circuit and control method thereof

Abstract

The embodiment of the invention discloses a synchronous rectification control circuit and a control method thereof, and the circuit comprises at least one switching tube, a current sampling module, a trigger signal receiving module, a synchronization control protection signal receiving module and a synchronous rectification control module, wherein the synchronous rectification control module is used for performing forced conduction on the switching tube which is currently controlled by a synchronization control protection signal provided by the synchronization control protection signal receiving module under triggering of a trigger signal provided by the trigger signal receiving module, detecting voltage or current acquired by the current sampling module, and turning off the switching tube which is currently controlled by the synchronization control protection signal. The invention further provides the synchronous rectification control method. By adopting the control circuit and the control method, impacts caused by a parasitic parameter in a switch are eliminated, the distortion generated by sampling a small signal on a big signal is avoided, and the control efficiency is improved.

Description

technical field [0001] Embodiments of the present invention relate to switching power supply technology, in particular to a synchronous rectification control circuit and a control method thereof. Background technique [0002] Synchronous rectification technology is currently a very common technology used in the field of switching power supplies. It uses a dedicated power metal oxide semiconductor field effect transistor (Metal Oxide Semiconductor Field Effect Transistor; hereinafter referred to as: MOSFET) with extremely low on-state resistance to replace the rectifier diode. To reduce rectification loss. At present, the traditional pulse width modulation (Pulse Width Modulation; hereinafter referred to as: PWM) control type synchronous rectification control is relatively simple, usually using the primary side drive voltage to perform synchronous rectification control, and if the phase of the secondary side current is inconsistent with the primary side voltage, This makes t...

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Problems solved by technology

[0004] However, the inventor found the following problems in the prior art during the process of implementing the present invention: the synchronous rectification control in the prior art is realized by sampling the voltage across the MOSFET, and the MOSFET itself has many parasitic components such as equivalent inductance and junction capacitance. Parameters, which affect the accuracy of the MOSFET's turn-on or turn-off control, it is difficult to ensure that the circuit works in the best state; and sampling a small signal through a large signal is prone to distortion, which reduces the control efficiency

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