Bridgeless power factor correction soft switching circuit and control method therefor

Abstract

The invention discloses a bridgeless power factor correction soft switching circuit. The bridgeless power factor correction soft switching circuit comprises a power supply part, a power part and a control part, wherein the power supply part is connected with the power part to supply electric energy to the power part; the power part comprises one or more paths of staggered power factor correction circuits, wherein each staggered power factor correction circuit comprises an inductor, a pair of switching elements, and a first capacitor and at least one second capacitor which are connected with each switching element in parallel; and one end of the inductor is connected with the power supply part while the other end of the inductor is connected to the two ends of each second capacitor through the pair of switching elements. The control part samples the current of an upper bridge arm switching element; when it is detected that the current passing through the upper bridge arm switching element is negative current and achieves a threshold value, the upper bridge arm switching element is turned off; after the upper bridge arm switching element is turned off, the current of each switching element is sampled; and when the current passing through the upper bridge arm switching element or the lower bridge arm switching element achieves zero or is close to zero, the lower bridge arm switching element is turned off.

Description

technical field [0001] The invention relates to the field of electronic circuits, in particular to a bridgeless power factor correction (Power FactorCorrection, PFC) soft switch circuit and a control method thereof. Background technique [0002] At present, the bridgeless PFC circuit has been widely used instead of the traditional bridged PFC circuit. The working principle of the existing bridgeless PFC circuit is briefly introduced here. Such as figure 1 Shown is a schematic structural diagram of an existing two-way interleaved PFC circuit. Two-way interleaved PFC circuit, two bridge arms work interleaved at 180°, switching elements can be MOSFET or IGBT. refer to figure 2 , taking the bridge arm connected to L1 as an example, when the switching element Q2 is closed, the current loop flows through L1 and Q2, at this time, the inductor L1 stores energy, and the current flowing through the inductor L1 rises linearly. During the off time of the switching element Q2, the ...

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Problems solved by technology

However, under other voltage conditions, the previously set threshold voltage U1 is not the lowest voltage at both ends of the capacitor when it resonates. As shown by the solid line in the figure, when the voltage drops to the threshold voltage U1, Q2 is turned on, but at this time the capacitor is two The terminal voltage has not dropped to the minimum value, and the switching loss caused by turning on Q2 at this time is relatively large

It can be seen that this method does not minimize the switching loss in most cases, and there are still large switching losses in some cases

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