| In recent years, power electronics technology has achieved rapid development,high power factor, high efficiency, small volume, have become the most urgentrequirements for power supply. With the wide application of power supply, study onhow to obtain excellent AC/DC converter has become a new hot spot. Reducing theswitching loss and pollution to power grid is an important factor to evaluate the powersupply. There’s no doubt that large use of excellent AC/DC converters will ease globalenergy shortage, which makes the research of extraordinary significance. Takingefficiency and power factor into account, this paper adopts two-stage AC/DCconverter. PFC stage and DC/DC stage are studied and analyzed.Firstly, by comparing the effect of passive power factor correction and activepower factor correction, the superiority of active power factor correction stands out.Compared single stage PFC circuit and two stage PFC circuit, their applicationfeatures are distinguished. Comparison and study are made on control method fortwo-stage active power factor correction, current control method is determined to thedesign of PFC circuit. Working principle of main circuit topology and power factorcorrection are analyzed, main circuit parameters are calculated, loss of PFC circuit isestimated. Design PFC inductor by simulation, the correctness of inductor design isverified by simulation.At the same time, PFC circuit is simulated.Then, by comparing advantages and disadvantages of various converters ofdifferent topologies, the unique advantages of the LLC resonant converter stands out.LLC resonant converter is chosen for DC/DC stage. Working principle of differentrelationship between switching frequency and resonant frequency is analyzed.According to FHA theory，value of k and Q are determined by analysis of voltage gaincharacteristics and input impedance characteristics. Different workspace boundariesare calculated, and the implementations of ZVS for the primary switch are obtained.The resonant parameters of the converter are calculated, and transformer is designedwith integrated magnetic structure to reduce the converter volume. Simulation isadopted to verify transformer parameters and design of LLC resonant converter.Finally, based on the theoretical study and simulation verification, experimentalprototype is built, experiments of PFC circuit and LLC circuit are carried out to testthe performance of the prototype. |
