CRM buck-boost converter controlled by segmented constant conduction time

Abstract

The invention discloses a CRM buck-boost converter controlled by segmented constant conduction time. The converter comprises a main power circuit and a control circuit, wherein the control circuit comprises an input voltage feed-forward circuit, a first multiplier, an RS trigger, a comparator, a first gating switch, a switching signal generation circuit, an output voltage feedback circuit, an ANDgate and NOT gate, a switching tube driving circuit and an output voltage sampling circuit; and the control circuit generates a control signal according to input voltage feedforward and output voltagefeedback of the main power circuit; two switching tubes in the main power circuit are driven to work, so that the conduction time of the converter working in the Buck stage and the conduction time ofthe converter working in the Buck / Boost stage in one power frequency period are different, the input current is closer to sine waves with the same phase as the input voltage, and the PF value is increased in the input voltage range. According to the invention, the power factor of the converter is improved, and the converter has the advantages of being small in inductive current peak value, smallin switching tube conduction loss and small in required diode stress.

Description

technical field [0001] The invention relates to the technical field of AC-DC converters of electric energy conversion devices, in particular to a control method for segmental constant conduction time of a CRM step-down-boost-boost converter. Background technique [0002] A power factor correction (Power Factor Correction, PFC) converter can reduce input current harmonics and improve input power factor, and has been widely used. PFC converters are divided into active and passive methods. Compared with passive methods, the active method has the advantages of high input power factor, small size, and low cost. Since its development in the 1980s, scholars from various countries have conducted in-depth research on active power factor correction technology (APFC) from the perspectives of control strategy, circuit topology, and small signal modeling, and have achieved a series of research results. For now, a new research focus of APFC technology is the research on PFC circuit topol...

AI Technical Summary

Problems solved by technology

Although Boost PFC is an effective way to improve power factor and reduce current harmonics, the large loss at low-voltage input is a bottleneck restricting its development, while Buck PFC has the characteristics of step-down of the Buck circuit itself, so that the input and output The voltage is relatively close, so that it can maintain high efficiency in the entire input voltage range. In addition, Buck PFC has the advantages of low output voltage, low common-mode EMI noise, no surge limiter and small main inductance. PFC has gradually become a research hotspot in power factor correction technology

[0003] However, there is an inherent dead zone in the Buck PFC converter, that is, the circuit does not work when the input voltage is lower than the output voltage, which limits the improvement of the PF value. Therefore, the Buck-Buck / Boost PFC converter is proposed. When the input voltage is lower than the output voltage, Buck / Boost works, when the input voltage is higher than the output voltage, Buck works

The conduction time of each switching cycle of the traditional CRM Buck-Buck / BoostPFC converter is the same. Although the control is simple and the diode has no reverse recovery problem, it has a large peak value of the inductor current, poor EMI differential mode characteristics, and large conduction loss of the switch tube. Disadvantages of lower PF value at low pressure

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