Method and device for controlling critical continuous mode unit power factor flyback converter

Abstract

The invention discloses a method and device for controlling a critical continuous mode unit power factor flyback converter. The method and device are used for improving the power factor of the critical continuous mode flyback converter. According to the method, the current peak envelope of a primary side switching tube of the critical continuous mode flyback converter is controlled, so that the current peak envelope of the switching tube changes along with changes of input voltage and output voltage within a power frequency cycle, and turn-off time of the switching tube is decided by the zero-crossing moment of a secondary side current of a transformer. Thus, the unit power factor of the critical continuous mode flyback converter can be obtained within the whole input voltage range.

Description

technical field [0001] The invention relates to power control equipment, in particular to a control method and device for a flyback power factor correction converter. Background technique [0002] In recent years, power electronics technology has developed rapidly, and power supply technology, which is an important part of the power electronics field, has gradually become a hot spot in application and research. Switching power supply has established its mainstream position in the field of power supply due to its high efficiency and high power density, but there is a fatal weakness when it is connected to the power grid through a rectifier: the power factor is low (generally only 0.45 to 0.75 ), and a large number of current harmonics and reactive power will be generated in the grid to pollute the grid. There are two main methods for suppressing harmonics generated by switching power supplies: one is the passive method, that is, using passive filtering or active filtering ci...

AI Technical Summary

Problems solved by technology

The discontinuous mode flyback power factor correction converter can automatically obtain unity power factor, but due to its large peak current, the conduction loss of the switch tube is very large, which affects the efficiency of the converter

The traditional critical continuous mode flyback power factor correction converter, its control method is as follows figure 1 as shown, figure 2 It is the waveform of the primary current, secondary current and input current. The peak envelope of the switching tube current is a standard sine wave. Although the efficiency is higher than that of the discontinuous mode flyback power factor correction converter, the unit power factor cannot be obtained. Both power factor and total harmonic distortion are worse than discontinuous mode flyback power factor correction converters

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