Chip beads principle and its application in switching power supply

- Jan 25, 2018 -

The main raw material for the magnetic beads is ferrite. The ferrite is a ferrimagnetic material with a cubic lattice structure. The ferrite material is iron-magnesium alloy or iron-nickel alloy. Its manufacturing process and mechanical properties are similar to the ceramic Similar, the color is gray-black. One type of core that is commonly used in EMI filters is the ferrite material, and many manufacturers offer ferrite materials that are specifically designed for electromagnetic interference suppression. This material is characterized by a very high frequency loss and a high magnetic permeability that minimizes the capacitance between the coil windings of the inductor at high frequency and high resistance. Ferrite materials are commonly used in high frequency applications because they predominantly exhibit inductance characteristics at low frequencies, resulting in low losses. At high frequencies, they mainly exhibit reactance characteristics and change with frequency. In practice, ferrite materials are used as RF attenuators for RF circuits. In fact, the ferrite can be better equivalent to the resistance and inductance in parallel, low frequency inductance is short-circuited by inductance, inductance inductance becomes high at high frequency, so that the current all through the resistance. Ferrite is a dissipating device where high-frequency energy is converted into heat energy, which is determined by its resistive properties.

The most important performance parameters for ferrite suppression electromagnetic interference are permeability and saturation flux density. Magnetic permeability can be expressed as a complex number, the real part of the inductance, the imaginary part of the loss, with the frequency increases. Therefore, its equivalent circuit is a series circuit consisting of an inductor L and a resistor R, both of which are a function of frequency. When a wire passes through such a ferrite core, the resulting inductance impedance formally increases with increasing frequency, but its mechanism is quite different at different frequencies. In the high frequency band, the impedance is mainly composed of the resistance component. With the increase of the frequency, the magnetic permeability of the magnetic core decreases, causing the inductance of the inductor to decrease and the inductance component to decrease. However, the core loss increases at this moment, As the resistance component increases, the total impedance increases, and as the high-frequency signal passes through the ferrite, the electromagnetic interference is absorbed and converted into heat energy.


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