Synchronous rectification control circuit, isolated power supply conversion circuit and control method

Abstract

The invention discloses a synchronous rectification control circuit, an isolated power supply conversion circuit and a control method, the synchronous rectification control circuit can be coupled witha synchronous rectification transistor and can send a control signal to the synchronous rectification transistor; the synchronous rectification control circuit comprises a comparison circuit, a drivecircuit, a signal adjusting circuit and a conduction voltage drop adjusting circuit. The input end of the comparison circuit is respectively coupled with the synchronous rectification transistor andat least one reference signal, and the output end of the comparison circuit is respectively coupled with the drive circuit and the signal conditioning circuit; the output end of the drive circuit is coupled with the synchronous rectification transistor and used for sending a control signal to the synchronous rectification transistor according to the signal output by the comparison circuit; the output end of the signal adjusting circuit is coupled with the comparison circuit and used for adjusting a set reference signal in the at least one reference signal according to the signal output by thecomparison circuit. According to the invention, accurate turn-off of the synchronous rectification transistor can be realized, the turn-off speed can be improved, and the reliability of the circuit isimproved.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits and relates to a control circuit, in particular to a synchronous rectification control circuit, an isolated power conversion circuit and a control method. Background technique [0002] Synchronous rectification technology (Synchronous Rectification, referred to as SR) is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide-Semiconductor Field-Effect Transistor, referred to as Metal-Oxide Semiconductor Field-Effect Transistor) to replace the rectifier diode to reduce rectification loss At present, it has been widely used in industrial power supply, consumer electronics and other fields. figure 1 It is a Flyback architecture diagram using diodes for secondary side rectification, figure 2 It is a Flyback architecture diagram using SR for secondary side rectification. Replacing rectification diodes with synchronous rectification MOSFETs with very low on-state resista...

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Problems solved by technology

[0004] image 3 It is a schematic diagram of the waveform of the existing predictive SR shutdown method; please refer to image 3 , the predictive SR turn-off method obtains the turn-off point of the SR MOSFET through prediction. The disadvantage is that the dynamic process may be common, that is, the primary side power switch tube and the secondary side rectifier tube will have a common state, so that the work of the flyback circuit Abnormal

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