Control method for auxiliary switching tube of active clamp flyback converter

Abstract

The invention relates to a control method for an auxiliary switching tube of an active clamp flyback converter. In the flyback converter, severe energy loss and voltage spike of a main switching tube are caused due to leakage inductance of a transformer and leakage inductance of circuits. The conventional solution mainly comprises methods for solving the problems by using residual current device (RCD) clamp, liquid crystal display (LCD) clamp and active clamp, wherein an active clamp circuit can effectively recover leakage inductance energy and obviously improve the efficiency. The invention provides a novel control method on the basis of the conventional active clamp flyback converter topology. In the conventional control method, a primary side switching tube is in complementary conduction with an auxiliary switching tube in each period; and in the control method, the primary side switching tube is switched on in each period, the auxiliary switching tube is controlled by setting voltage of a clamp capacitor in the clamp circuit, and when the voltage of the clamp capacitor reaches the set value, the auxiliary switching tube is switched on. Compared with the prior art, the method has the advantages that: the switching loss of the auxiliary switching tube can be reduced; and more importantly, the efficiency of the circuit can be greatly improved under a light load, and the no-load loss is reduced.

Description

technical field [0001] The invention relates to a control method for an auxiliary switching tube of an active clamp flyback converter, which belongs to a power electronic converter. Background technique [0002] There are three traditional control methods for flyback converter leakage inductance recovery as follows: [0003] 1: RCD clamp circuit [0004] The RCD clamping circuit has the simplest structure, the lowest cost, and is easy to implement, but all the energy in the leakage inductance is consumed in the snubber resistor, which reduces the efficiency of the converter. It is suitable for occasions that do not require high efficiency and strictly control costs. [0005] 2: LCD clamp circuit [0006] The LCD clamping circuit can realize passive and lossless leakage inductance energy feedback, but it needs an external inductance, and the parameter setting is difficult, but the large LC resonant current at high frequency increases the conduction loss of the power switch,...

AI Technical Summary

Problems solved by technology

Although the traditional active clamp flyback control circuit is very efficient at full load, it is still inefficient at light load

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