A self-driven synchronous rectification circuit for forward converter

Abstract

The invention discloses a self-driven synchronous rectification circuit of a forward converter. The circuit leads the driving signals of the two auxiliary windings to the rectifier switch tube and the freewheeling switch tube in the main circuit for driving, so that only positive drive voltage exists in the whole switching cycle, ensuring the safe driving range of the drive voltage. ±20V while avoiding additional drive power consumption. In addition, by adding two diodes in the driving circuit of the rectifier switch tube and the freewheel switch tube, the rectifier tube is used to complete the shutdown of the freewheel tube, and the freewheel tube is used to complete the shutdown of the rectifier tube, which improves the rectifier tube and the continuous current switch. Shut-off speed of the flow tube.

Description

technical field [0001] The invention provides a self-driven synchronous rectification circuit, which belongs to the field of drive circuits. In particular, it relates to a drive circuit for a forward converter. Background technique [0002] A synchronous rectification circuit of an existing forward converter such as figure 1 shown. The circuit includes: transformer T1, first MOS transistor S1, second MOS transistor S2, third MOS transistor S3, output inductor L O , output capacitance C O and the input capacitor C in . The connection relationship of each electronic component is as follows figure 1 As shown, the input signal generates a changing current in the primary side winding N1 of the transformer T1 through the turn-on and turn-off of the first MOS transistor S1, and the power is transmitted to the secondary side circuit through the primary side winding N2 of the transformer T1. The third MOS transistor S3 serving as a rectifier and the second MOS transistor S2 se...

AI Technical Summary

Problems solved by technology

[0004] figure 1 Although the circuit is simple and the cost is low, but because the voltage signal of the power winding is directly used to drive the rectifier and the freewheeling tube, in order to avoid breakdown of the rectifier and the freewheeling tube, the output voltage of the power winding should not be too high, which is only suitable for Application environment of low voltage output

figure 2 The scheme drives the rectifier tube and the freewheeling tube respectively through the induced voltage of the two auxiliary windings. Although the restriction on the output voltage of the power winding is lifted, the driving voltage signals of the rectifier tube and the freewheeling tube have both positive voltage and negative voltage. voltage, compared to figure 1 The scheme brings additional driving loss, which weakens the efficiency improvement effect brought by synchronous rectification

It can be seen that the existing technical solutions have the disadvantages that the output voltage of the forward converter is too low or the driving loss is greatly increased

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