Common mode inductors in switching power supplies?
Common mode choke, also called common mode choke, is a symmetrically wound coil with opposite direction and same number of turns on a closed magnetic ring. The ideal common mode choke has a suppression effect on the common mode interference between L (or N) and E, and has no inductive suppression effect on the differential mode interference between L and N. However, the actual coil winding is not exactly the same as the common mode choke. However, incomplete symmetry of the actual coil winding can lead to differential mode leakage inductance. Signal current or power supply current flows through the two windings in opposite directions, the resulting magnetic fluxes cancel each other out, and the choke coil shows low impedance. Common-mode noise current (including ground loop nuisance current, also known as longitudinal current) flows through the two windings in the same direction, the resulting flux is added in the same direction, the choke presents high impedance, thus playing a role in suppressing common-mode noise.
Common mode inductor is essentially a two-way filter: on the one hand, to filter out common mode electromagnetic interference on the signal line, on the other hand, to inhibit itself from sending out electromagnetic interference, to avoid affecting the normal operation of other electronic equipment in the same electromagnetic environment.
Common mode choke can transmit differential mode signals, DC and very low frequency differential mode signals can be passed, and for high-frequency common-mode noise presents a large impedance, so it can be used to inhibit common-mode current harassment.
What is the application of common mode inductor in switching power supply?
Common mode inductor is sometimes called common mode choke, because it plays a role in inhibiting, more used in switching power supply circuits, constituting a variety of filters for EMI filtering, inhibit a variety of high-speed signals generated by electromagnetic waves emitted to the outside, the following chart, the circuit has a set of parallel lines, the normal signal through the basic unaffected, but when there is a common-mode current flow through, due to the isotropy of the common-mode current, it will generate a homogeneous magnetic field inside the coil, which is the same direction as the common mode current. Coil to produce the same direction of the magnetic field and increase the inductive resistance of the coil, so that the coil shows a high impedance, resulting in a strong damping effect, then the common mode current will be attenuated, to achieve the purpose of suppressing interference.
