What is the relationship between high frequency transformers and cell phone mask technology? Now it's up to the manufacturers of mobile masks.
It is well known that the interference effects of electromagnetic fields can be minimized or eliminated by the effects of magnetic masks, magnetic isolation and transfer elements. Magnetic fields can be transferred more easily through magnetic materials than through air or other media materials. Therefore, magnetic materials with high magnetic permeability are often used to make annular or sealed mask elements.
Type of mask material
The mask effect is measured by the extent to which the magnetic field strength of the device or component is attenuated after the device or component is covered. The attenuation rate or attenuation of magnetic field strength after the mask is a function of the magnetic conductivity, thickness and size of the mask. High permeability material than low permeability is expensive, but if use monolayer mask effect of high magnetic permeability material and multilayer mask effect of low permeability materials are the same, may choose the thickness of the thin, high permeability material more economy.
2. Selection of mask materials
As mentioned above, the magnetic permeability of the mask material, the geometric shape of the mask and the thickness of the material all influence the effect of the mask. Therefore, the principle of choosing the mask material is:
A. For the maximum attenuation of the external magnetic field, the material with high magnetic conductivity (ROI) should be used.
B. The effect of the magnetic mask is also a function of the ratio (t/D) of the material wall thickness of the mask to the diameter (which is its diagonal when the rectangular mask is used) of the mask.
C. If the external interference magnetic field is too high, the attenuation effect of the mask will be reduced. This is because when the external magnetic field is too high, the magnetic material will be close to magnetic saturation.
D. In normal circumstances, it is not practical to make a mask out of thick metal materials. Because it's expensive. Instead of a mask, thin foil can be simply wrapped around a device affected by a magnetic field.
3. Design of mask
A. The following information is required for mask design:
Data must be measured or estimated on how much the shielding material can attenuate.
In order to achieve a good effect on the magnet cover, the most suitable shape of the canopy must be chosen. Typical or relatively optional geometric shapes include long cylinders and rectangular shells. Other spheres, flat plates or cones will also be used.
B. when designing the mask, the magnetic flux density value (gauss) must be determined first, and the thickness of the mask material should be selected accordingly. Because of the mask material mu value with the beta distribution is nonlinear relationship, acting on the mask cover of magnetic flux density, the material must be made to reach its peak magnetic permeability, such as permalloy and mumetal magnetic flux density should be around 3600 gauss.
The thickness of the mask material can be calculated and determined by the following formula:
T = 1.25DH/B (in.)
Where, D is the attenuation rate, which is obtained from the magnetic field intensity before the mask except the magnetic field intensity after the mask. For a magnetic material with a high content of nickel, the value of density can be as low as 80000.
C. when designing the mask, the following matters shall be noted:
(1) for a high magnetic field intensity, can use multilayer material mask mask, closest to the strong magnetic field that a layer of material should be able to weaken the bigger flux of alloy materials, such as alloy, 48 magnesill; The second layer should be made of materials with high magnetic conductivity, such as permo alloy. If possible, the gap between the magnetic field emitter and the shielding material closest to it should be allowed to be minimal (about 1/2 "). In design and manufacturing practice, polyester film is used to separate each layer of multilayer shielding materials.
Parliamentary plates are often used to plug into the objects of the enclosures if they fail to achieve the goal of closing the stray magnetic field of the field emitter. If the height and width of the plate are much larger than the size of the magnetic field emitter and the required mask, the stray magnetic field can be closed.
When metal plates with a thickness of less than 0.006 "are used as shielding materials, they are generally used on the prototype because the thickness is easy to be molded by hand. If the mask is made mechanically in batch production, thicker materials should be used. But no more powerful machinery operation should be paid attention to, such as bending, stamping, welding material can produce stress, so that the material performance degradation, this needs to improve by appropriate temperature annealing.
Generally, at low frequencies (around 600Hz), when the ratio of the length of the mask to the diameter is greater than 3, the thickness of the mask material is increased from 0.014 to 0.050, so that the mask effect is enhanced. If the ratio is lower than 3 and the material thickness is increased to 0.025, the degree of magnetic field attenuation will be small.
Anyway, so that's the relationship between mask technology and high frequency transformers, do you know that? It's the high frequency transformer that USES the cell phone mask technology.