Synchronous rectification external drive proposal

Abstract

The invention discloses a synchronous rectification external drive circuit, which comprises a main transformer (T1) with a primary winding and a secondary winding, a first synchronous rectifier (Q1) and a second synchronous rectifier (Q2), a first output inductance and a first external drive circuit (12); wherein, the drain electrodes of the first synchronous rectifier and the second synchronous rectifier are respectively connected with the secondary winding of the main transformer; one end of the first output inductance is connected with the secondary winding of the main transformer; the first external drive circuit receives external drive signals of the first synchronous rectifier and the output thereof is connected with a grid of the second synchronous rectifier (Q2) and controls the breakover and cutoff of the second synchronous rectifier (Q2). The design proposal of the synchronous rectification external drive provided by the invention solves the problem that the synchronous rectifier of a supply converter in the prior art is not shut off timely or the shutoff time is so long to cause that the output voltage inversely irrigates and the output presents the negative pressure. The circuit is simple, has low cost, wide applicability and high effect.

Description

technical field [0001] The present invention relates to the field of power electronics, and more specifically, relates to an externally driven synchronous rectification design scheme for a power converter. Background technique [0002] Products in communication, communication and other fields widely use isolated power supplies. With the development of technology, the output voltage of isolated power supplies is required to be lower and lower, the output current is larger and the efficiency is higher and higher. Therefore, the traditional Diode rectification has been replaced by MOSFET synchronous rectification, which can output lower voltage, higher current, and provide higher efficiency. At present, synchronous rectification has been widely used in the rectification technology of isolated power converters, and many chip manufacturers have launched PWM controllers with external drive signals for synchronous rectification. [0003] In the isolated power converter rectificati...

AI Technical Summary

Problems solved by technology

The Vout output is fed back, and the Vout output has a large reverse overshoot negative voltage. This situation is very easy to damage the load connected to the output terminal or cause logic errors.

At the same time, the control gates of SQ4 and SQ6 transistors in the drive circuit are directly connected to the secondary winding of the main transformer, and the maximum limit voltage borne by the control gates of SQ4 and SQ6 transistors is only 20V, so when the output voltage of the secondary winding of the main transformer When high, the drive circuit is unusable and has great limitations

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