Short-circuit protection method for self-excitation push-pull type convertor

Abstract

The invention discloses a short-circuit protection method for a self-excitation push-pull type convertor. The short-circuit protection method mainly comprises the following steps of: shorting out the output end of the self-excitation push-pull type convertor, and adjusting leakage inductance of a main power transformer in the self-excitation push-pull type convertor, so that short-circuit protection current of the self-excitation push-pull type convertor is more than short-circuit protection limited current; increasing an electric capacity of a starting capacitor in the self-excitation push-pull type convertor, so that the self-excitation push-pull type convertor enters an interval type high-frequency oscillatory condition, and the short-circuit protection current is reduced to be lower than the short-circuit protection limited current. With the adoption of the short-circuit protection method, the self-excitation push-pull type convertor can carry a large-capacity load on the premise of not additionally arranging an element. Furthermore, when the circuit is shorted out, the short-circuit protection current is still very low so that the self-excitation push-pull type convertor can work at an output short-circuit state for a long period.

Description

technical field [0001] The invention relates to a short-circuit protection method for a power converter, in particular to a short-circuit protection method for a self-excited push-pull converter. Background technique [0002] The existing self-excited push-pull converter, the circuit structure comes from the self-excited oscillating push-pull transistor single-transformer DC converter invented by G.H.Royer in 1955, which is also the beginning of realizing high-frequency conversion control circuit; some circuits From the self-excited push-pull double transformer circuit invented by Jen Sen in the United States in 1957, it was later called the self-oscillating Jensen circuit; these two circuits are collectively referred to as the self-excited push-pull circuit pull converter. The self-excited push-pull converter is described on pages 67 to 70 of "The Principle and Design of Switching Power Supply" published by Electronics Industry Press, and the book's ISBN number is 7-121-00...

AI Technical Summary

Problems solved by technology

[0009] 1. Poor capacitive load capacity at the output end

by figure 1 For example, when the value of the capacitor C3 is too large, when the power supply of the converter is powered on, since the terminal voltage of the capacitor C3 is 0, the capacitor C3 is equivalent to a short circuit when the power is turned on, and the circuit works under the high-frequency self-excited push-pull oscillation , at this time, the transmission efficiency of transformer B1 is low, and it is impossible to charge the capacitor C3 with a large current, which makes it difficult to start the circuit, and it takes a long time for the output terminal DC out to output the normal voltage. Low voltage output, unable to output normal voltage

For example, the circuit parameters in the above three patent publications are made into a DC converter with an input of 5V and an output of 5V. When the capacitor C3 is increased to 220uF, it cannot be started normally.

[0010] 2. The short-circuit protection function and the capacitive load capacity are not well balanced

[0014] 3. In order to obtain a good short-circuit protection function and a large capacitive load capacity, it is necessary to add a large number of other components, generally including optocouplers and operational amplifiers for voltage detection, which are costly and difficult to make small

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