Wide Temperature Low Power Mnzn Ferrite Materials And Transformer Simulation

In this thesis, low loss MnZn power ferrites were prepared by conventional oxide ceramic process. To seek the effective way of preparing high permeability (μi), high saturation magnetic induction (Bs), high Curie temperature (Tc) and low losses MnZn ferrites, the influences of main compositions, calcination temperature and additives on the microstructure and magnetic properties of MnZn ferrite were investigated. Then the design and simulation were carried out on the switching mode power supply using the developed ferrite core.First, for low losses MnZn power ferrites within wide temperature ranging, the optimal molar ratio of three oxide compositions is Zn0.23Mn0.68Fe2.09O4. Second, the effects of calination temperature on the microstructure and magnetic properties in MnZn ferrite were studied. The results show that: owing to its influence on the activity of powders, proper calination temperature could make grains grow homogeneous, reduce abnormal large grains formed during sintering, decrease porosity, and enhance density and magnetic properties. Either too high or too low calination temperature would damp the microstructure and magnetic properties. When calination temperature is 860℃, MnZn power ferrites have the highest initial permeability and the lowest power losses. Thirdly, the effects of Ta₂O₅ and SnO₂ additives on the microstructure and magnetic properties in MnZn ferrite were studied. The results show that: with the increase of Ta₂O₅ additive, the average grain size of MnZn ferrite increases monotonously, the initial permeability and saturation magnetic induction increase initially and then decrease, while the total losses (Pcv), hysteresis loss (Ph) and eddy current loss (Pe) decrease first and increase subsequently. When doped with 0.06wt% Ta₂O₅, MnZn power ferrites possess the highest initial permeability and saturation magnetic induction, and the lowest power losses. Proper addition of SnO₂ can increase the density, makes the grain grow uniform, and decreases the power losses. With the increase of SnO₂ additive, the second peak of permeability moves to lower temperature. And the proper addition of SnO₂ is 0.04wt%. Finally,the production of transformer with the core developed independently of this project has been simulated based on the MCT (Magnetic Component Tool) software, accordingly, the main parameters of the transformer model were obtained at different temperatures. Through the model of transformer with the material at different temperatures has been leaded into the RCD forward converter topology, the efficiency of switching power supply at different temperatures have been supplied. The results showed: with the width of temperature at 25¹00℃, the efficiency of switching power supply used low losses core over a wide temperature range, which can meet the requirements of various types of electronic equipment to small, highly efficient and highly reliable switching power supply, were better than the PC40 core transformer.