Self-oscillating flyback converter with function of output short circuit protection

Abstract

The invention discloses a self-oscillating flyback converter with the function of output short circuit protection, which sequentially comprises an input filter circuit, a main power circuit, an output filter circuit and an output short circuit protection circuit, wherein the main power circuit comprises a transformer primary winding, an output winding and a switching tube, so that energy conversion, energy transfer and the isolation of input and output are realized; and the output short circuit protection circuit is arranged in a negative feedback circuit of the main power circuit. The self-oscillating flyback converter can simplify a circuit structure of the output short circuit protection circuit, and is favorable for reducing circuit loss.

Description

technical field [0001] The invention relates to a low-power DC-DC conversion power supply, in particular to a self-oscillating flyback converter with an output short-circuit protection function for the conversion power supply. Background technique [0002] Since the self-oscillating flyback converter requires smaller and smaller volume, higher frequency and higher power density. Therefore, the requirements for output short-circuit protection are getting higher and higher, especially in the case of output short-circuit, the internal loss of the converter is required to be smaller. This requires additional peripheral circuits to realize the output short-circuit protection of the self-oscillating flyback converter. At present, some technical solutions for realizing such functional circuits are relatively mature, but their common disadvantages are that there are many peripheral components, and at the same time, development costs and technical difficulties are increased. [000...

AI Technical Summary

Problems solved by technology

The main disadvantages of this protection circuit are: 1. The circuit structure is complex; 2. Because it is located in the main circuit, the power loss is large when the short circuit continues; will cause the fault to expand

[0006] When the output of the above circuit is short-circuited, due to the existence of the leakage inductance of the primary winding P1 and the feedback winding P3, the moment the MOS transistor TR2 is turned off, the leakage inductance of the primary winding P1 and the leakage inductance of the feedback winding P3 resonate with the capacitors C14 and C11 respectively, and the resonance makes The MOS tube is repeatedly turned off, which makes the energy consumed by the MOS tube and the energy transferred by the primary winding increase instantaneously, which eventually leads to an increase in short-circuit power consumption and even damages the product.

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