Active Clamp Flyback Circuit and Its Control Method

Abstract

The invention relates to the field of switching converters, in particular to a control circuit and a control method of a flyback active clamp switching converter. The invention provides an active clamping flyback circuit capable of realizing frequency reduction and ZVS. The flyback circuit includes a main power loop, a clamping loop, and an output rectifying and filtering loop. The main power circuit is formed by connecting a transformer and a main switching tube, the clamping circuit is formed by connecting a clamping switch tube, a clamping capacitor and a clamping diode, and the output rectifying and filtering module is composed of an output rectifying diode connected to the output capacitor. Compared with the prior art, the present invention can achieve frequency reduction under light load, and the control scheme is flexible; and the loss of the transformer winding and the internal resistance of the switch tube caused by the switching loss and the effective value of the current under no-load are very small, which greatly improves the Reduced no-load power consumption and improved light-load efficiency.

Description

technical field [0001] The invention relates to the field of switching converters, in particular to a control circuit and a control method of a flyback active clamp switching converter. Background technique [0002] With the rapid development of the field of power electronics, switching converters are used more and more widely, especially people put forward more requirements for switching converters with high power density, high reliability and small size. Generally, the traditional low-power AC / DC conversion is realized by the flyback topology, which has the advantages of simple structure and low cost; however, the ordinary flyback topology is a hard switch, and cannot recover leakage inductance energy, thus limiting the efficiency and efficiency of small and medium power products. In order to meet the development trend of miniaturization, light weight and modularization of power converters, soft switching technology has become one of the hot spots in power electronics tech...

AI Technical Summary

Problems solved by technology

[0005] However, the duty ratio of the clamping circuit of the traditional flyback active clamping converter is constant from no-load to full-load, so the peak current IS1 is still very high under no-load, so the clamping circuit has a large cycle energy. Under normal circumstances, the efficiency can be effectively improved, but the light load efficiency is very low, and the no-load power consumption is very large

In addition, because the duty cycle is almost constant, it can only be used in fixed frequency control, which means that it is difficult to optimize the light-load efficiency, which is almost unacceptable for commercialization, which means that it is difficult to promote. So no matter how high the full load efficiency is, it doesn't make sense.

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