Self-drive circuit for switch power supply

Abstract

This invention relates to an automatic drive circuit for power switch, whose changer circuit comprises main horsepower MOSFET, synchronous rectifying tube, and the said automatic drive circuit comprises a time-delay drive circuit with its two ends separately attached to PWM signal and main power tube, a cut-out circuit including a PNP transistor, a NPN transistor and two electric resistance, a drive sustaining circuit including two diodes, three electric resistances, two capacitors and a PNP transistor. The invention makes the high power density and low cost design easier in the case of low power application.

Description

technical field [0001] The invention relates to a switching power supply, in particular to a novel self-driving circuit of an active clamp tube or a synchronous rectifier tube of a switching power supply. Background technique [0002] High efficiency is always an important indicator of switching power supply design. In order to achieve high efficiency, active clamping and synchronous rectification techniques are widely used. However, the driving of the clamp tube in the active clamp circuit or the synchronous rectification tube in the converter using synchronous rectification technology has become a difficult problem for designers. The present invention introduces a self-driving circuit by taking an active clamp forward converter as an example. [0003] Figure 1(a) shows the drive circuit of an active clamp tube in a commonly used active clamp forward converter. The main circuit of the converter includes a primary power circuit and a secondary circuit, and the primary pow...

AI Technical Summary

Problems solved by technology

This solution solves the drive of the active clamp tube, but this drive circuit transmits the entire PWM signal from the primary side of the isolation drive transformer to the secondary side to realize the shutdown and opening of the active clamp tube S2. The isolation drive transformer needs transfer power, therefore, the volume of the isolation drive transformer is difficult to make small

In small to medium power applications, this makes high power density difficult to achieve, and the cost of the isolation drive transformer makes low cost designs difficult

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