Synchronous rectification driving circuit of flyback circuit

Abstract

The invention discloses a synchronous rectification driving circuit of a flyback circuit, which has simple structure, easy realization, high efficiency and small volume. The gate-level driving circuitof the secondary edge synchronous rectifying tube Q2 comprises a capacitor C2, resistors R2, R3 and R4, diodes D1 and D2, and a PNP triode VT1, and a driving transformer Tr1 realizes the isolation and transmission of primary side PWM driving signals. The invention uses few discrete elements for forming the driving circuit, thus realizing that the driving voltage is kept to be relatively stable within the wide input voltage range, and avoiding the common-pass phenomenon of a main switching tube Q1 and a synchronous rectifying tube Q2. The invention improves the efficiency of a converter and enhances the reliability of the circuit.

Description

technical field

[0001] The invention relates to a DC / DC power supply circuit, in particular to a synchronous rectification drive circuit used in a flyback circuit. Background technique

[0002] The flyback converter circuit is widely used in low-power isolated power supplies because of its simple circuit structure, fewer components, and low cost. At present, the power supply used in the communication field is more and more widely used to output low voltage and high current. If the traditional diode rectification is still used, the loss on the rectifier diode will be very large. To maintain the high efficiency of power conversion, mainly use Secondary side synchronous rectification technology, because the conduction loss of MOSFET is very small. The most critical aspect of synchronous rectification technology is the drive mode. At present, there are generally two modes: self-drive or external drive.

[0003] Although the structure of the self-driven driving method is simple...

Images