Active clamp flyback circuit and control method thereof

Abstract

The invention relates to the field of switching converters, and particularly relates to a flyback active clamp-type switching converter control circuit and a control method thereof. The active clamp flyback circuit of the invention can realize reduced frequency and ZVS, and comprises a main power circuit, a clamp circuit, and an output rectification filter circuit, wherein a transformer and a main switching tube are connected to form the main power circuit; a clamp switching tube and a clamp capacitor and a clamp diode are connected to form the clamp circuit; and an output rectification diode and an output capacitor are connected to form the output rectification filter circuit. In comparison with the prior art, reduced frequency in light load can be realized, and the control scheme is flexible; switching loss in no load and loss of a transformer winding and switching tube inner resistance caused by a current effective value are little, no-load power consumption is greatly reduced, and the light-load efficiency is improved.

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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