Bridgeless buck-boost AC-to-DC converter

Abstract

The invention relates to a bridgeless buck-boost AC-to-DC converter. The converter is used for converting an AC input power source so as to provide a DC output power source with a positive electrode end and a negative electrode end on an output capacitor. The converter is characterized in that the first end of a first circuit is coupled with the first end of the AC input power source; the second end of the first circuit is coupled with a grounding end; the third end of the first circuit is coupled with the positive electrode end or the negative electrode end of the DC output power source; thefirst end of a second circuit is coupled with the second end of the AC input power source; the second end of the second circuit is coupled with the grounding end; the third end of the second circuit is coupled with the positive electrode end or the negative electrode end of the DC output power source; a third diode is coupled between the first end of the second circuit and the grounding end; and afourth diode is coupled between the first end of the first circuit and the grounding end. According to the bridgeless buck-boost AC-to-DC converter of the invention, conversion efficiency can be improved; a capacitor with low withstand voltage can be selected as the output end of the direct current output power source, a surge current limiter for starting up does not need to be added. The converter can be operated under a discontinuous conduction mode, a continuous conduction mode and a critical conduction mode.

Description

technical field [0001] The invention relates to an AC-to-DC converter, in particular to a bridgeless step-down AC-to-DC converter. Background technique [0002] The traditional boost power factor correction converter (BoostPFC) is still widely used in the industry because of its simple circuit structure. Its typical circuit structure is as follows: figure 1 shown. However, the step-up power factor correction converter has three disadvantages: First, the input must use a bridge rectifier diode, which makes the diode conduction loss account for a higher proportion of the total loss, and the lower the AC input voltage, it will bring more loss of efficiency. Second, since the output voltage of the step-up power factor correction converter must be higher than the peak value of the input AC power voltage, a 400-volt or even 450-volt electrolytic capacitor must be used, and the price of the electrolytic capacitor will also increase as the withstand voltage increases . Third, be...

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Problems solved by technology

[0005] In order to solve the problems of bridge rectification loss, switching surge current, high output voltage, excessive n

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