A single stage pfc llc circuit

Abstract

The invention relates to a single-stage PFC LLC circuit, wherein an input rectifier forms a circuit for charging a capacitor in a Boost converter; the Boost converter also includes a first inductance, a first switching element and a second switching element; an isolated DC-DC The converter includes a bridge arm structure, a resonant inductor, a resonant capacitor, a transformer, and a rectifier filter circuit; one end of the first inductor is connected to the first output end of the input rectifier, and the other end of the first inductor is connected to the middle tap of the primary winding, and connected to The point is connected to the midpoint of the bridge arm structure through a branch including part of the primary winding, resonant inductance and resonant capacitor; or the other end of the first inductance is connected to one end of the primary winding, and the connection point is connected by including a resonant inductance and a resonant capacitor The branch of the circuit is connected with the midpoint of the bridge arm structure, and the other end of the primary winding is connected with the first output end of the input rectifier. In the present invention, the LLC working state of the circuit is not affected, the bandwidth of the output voltage loop can be designed higher, and the power frequency ripple of the output voltage of the secondary side is small.

Description

technical field [0001] The invention relates to the technical field of power circuits, in particular to a single-stage PFC LLC circuit. Background technique [0002] The traditional rectifier bridge electrolytic capacitor circuit will seriously distort the input current waveform, the higher harmonic content is relatively high, and the power factor is very low, which greatly increases the load on the power grid. With the promotion of domestic 3C certification, more and more power supplies need to meet certain harmonic requirements in order to pass the certification in the future. In order to meet this requirement, the traditional method is to adopt a two-stage scheme, that is, PFC+DCDC. Although this scheme can achieve relatively high power factor and low harmonic current, it is very expensive. In order to reduce costs, single-stage PFC technology has been paid more and more attention. [0003] In the prior art, such as figure 1 The common way shown is to realize single-st...

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Problems solved by technology

[0006] In this way, in order to realize the function of single-stage PFC, the output feedback loop needs to be much less than twice the power frequency frequency, and the bandwidth is very low. Generally, it is designed to be 10Hz~20Hz, so the power frequency ripple on the output voltage is very large.

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