| In recent years, wireless charging technology has become the hot spots, already existing and having relatively conventional market wireless charging device, are based on electromagnetic induction and electromagnetic resonance technology, the main application frequency band of the former is 100 ~ 205KHz(refer to the Qi standard),and the main application frequency band of the latter is about 10 MHz. But the wireless charging equipment is universal, mainly because that its technology still has many problems, the main problem is how to improve the charging efficiency, so as to make it can be compared with the charging cable, or even replace the cable charging. Qi standard notes that the ferrite can be used as shielding materials. The performance parameters of shielding materials for charging efficiency has a great impact.First, in view of the application in the low frequency(100 ~ 205 KHz) ferrite is studied, the goal is to prepare the material with high initial permeability, high saturation magnetic induction intensity and low power consumption. Which focuses on that the changes in the formula and preparation of ferrite how influence its magnetic properties.Conclusion: ZnO content ranges from 26.78mol% to 29.87mol%, material μi rises, Bs,Br, Hc and Pcv gradually decrease, considering all aspects; ZnO content is controlled between 28.84mol% ~ 29.87mol% that is appropriate. CuO can help sintering, and with CuO content increasing, μi increases first and then decreases, its content is set at about6.695mol% ~ 8.24mol% can better balance the magnetic properties.When Fe2O3 content is 48.5mol%, μi value reaches a maximum, Fe2O3 content is controlled between47.5mol% ~ 48.5mol% that is most conducive to the goal. V2O5 can promote grain size increased and more uniform, so initial permeability increases, but excessive doping,magnetic materials can be deteriorated. Suitable calcining temperature can optimize NiCuZn ferrite properties, calcining temperature is set at between 800 ℃ ~ 850 ℃ for the best. Appropriate to extend the secondary milling time is good to broke pre-powder thoroughly, thus promotes the sintering and make it more complete crystallization,increase the degree of crystallinity, the second milling time is set 4 to 5 hours can achieve the best results.Second, choosing used in high frequency(10~13.56MHz) ferrite shielding material for the study, its goal is to improve the value of the real part of the complexpermeability(higher than 210 at 13.56MHz), lower false permeability unit value, i.e.loss( less than 10 at 13.56MHz). This process analyzes the impact of adjustment process, and the Co2O3 and Co2O3-V2O5 on the material properties. The reaction mechanism is introduced by Co ions will increase the cutoff frequency, thereby reducing losses. The results show, using0.97321.030.370.130.50(ZnNiCu)O(FeO) as the main composition and calcining temperature at 900℃,the second milling with 0.4wt% Co2O3 for 3 hours, the sintering temperature at 1000℃, the samples obtained basically reach the requirements of objective.Finally, the receiving coil which applied in the low-frequency joined the ferrite as an example, the impact of ferrite material on the efficiency of wireless charging is analyzed by the simulation. Learned: ? ? value remains unchanged, in the same frequency, increasing ?? that can make the charging efficiency increase; the role of material loss ? ? to the charging efficiency is small; while the ferrite material has anti-metal properties. |
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