The magnetic loop inductor is an electronic component. The main function is an electromagnetic induction conversion. The simpler inductor can be a wire, which can be used as an antenna. (颐特电阻) converts electrical energy into electromagnetic waves. The more complicated one is the hollow wire diagram, which can be used in frequency selection loop and RF transmission circuit. It is better than the former two inductors and the word inductor, which can be used for filtering and energy storage. . There are also common mode inductors that can be used to resist dryness.
Magnetic loop inductance is a physical quantity that measures the ability of a coil to generate electromagnetic induction. When a current is applied to a coil, a magnetic field is generated around the coil, and the coil has a magnetic flux. The larger the power supply to the coil, the stronger the magnetic field and the greater the magnetic flux through the coil.
Experiments have shown that the magnetic flux through the coil is proportional to the current flowing in, and their ratio is called the self-inductance coefficient, also called inductance. At the point of magnetic loop inductance, small-scale capacitance is better than large-scale capacitance. The principle is that large-scale capacitance heat conduction does not reach the entire capacitor so quickly, so the temperature difference between different points of the capacitor body is large, so the expansion is large. The size is different and the stress occurs.
This is the same as a thin glass that is easier to break than a thin glass when poured into boiling water. Excellent soldering temperature profiles are required for reflow soldering. If wave soldering is not required for reflow soldering, this failure will be greatly increased. But work is always less ambitious. Magnetic ring inductance soldering iron hand soldering sometimes does not prevent it. For example, for electronic manufacturers of PCB out-of-process processing, some products are extremely small, and manufacturers of patch-external manufacturers are not willing to pick up such a single-time, only hand-welded welding; when the sample is produced, it is generally also a hand-crafted welding; special cases are reworked or When repairing the welding, it is necessary to weld the craft; when the repairman repairs the capacitor, it is also the welding of the craft.
The main failure mechanisms of magnetic loop inductance are mechanical stress and thermal stress. As a magnetic ring inductor magnetic material, the magnetic bead magnetic ring has strong brittleness, and the magnetic bead body is prone to crack when subjected to external mechanical stress (such as impact, collision, PCB warpage). Therefore, the use of magnetic ring inductance requires attention to the following:
1. When the magnetic beads are laid out on the PCB, they must not be within the range of 75px of the in-line connector. The flat connector is not subject to this limitation;
2. One of the failure mechanisms of the magnetic beads is thermal failure. The reason for the failure is that a large current flows through the magnetic beads, and the current generates heat loss (Q=I2*Rdc) on the DC resistance Rdc of the magnetic beads, and the heat is large. Can not be dissipated in time, will cause the magnetic beads to be unevenly heated as a whole, resulting in internal stress leading to cracks, the occurrence of cracks, the magnetic permeability of the magnetically permeable material is damaged, so the magnetic field lines of the high-frequency wave signal on the magnetically permeable material The transmission is affected, making the filtering effect worse.
Example: Magnetic loop inductor power supply rated voltage 3.3V, rated current 300mA, remote IC on the circuit board requires a lower power supply voltage of not less than 3.0V, and requires 100mV, 300mVpp noise, can reach 50mVpp after magnetic bead filtering s level,
1. The rated current of the magnetic induction power supply is 300mA, and the derating factor is 0.75, then the magnetic bead with a smaller rated current of not less than 300mA / 0.75 = 400 mA is selected;
2. IC requires that the power supply voltage should be lower than 3.0V, and the larger voltage drop on the DC resistance of the magnetic bead on the magnetic bead must be no more than 0.3V. For example, (Fig.), ie 300mA * Rdc < 0.3="" v,="" get="" rdc="">< 1="">
3. In summary, the magnetic bead index is selected to meet the following requirements: Rac ≥ 250 Ω (at 100 MHz), rated current not less than 400 mA, Rdc < 1="">
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