Switch mode power supply common mode inductors?
A common mode choke, also known as a common mode choke, is a symmetrically wound coil with opposite directions and the same number of turns on a closed magnetic ring. Ideally, a common mode choke has a suppression effect on common mode interference between L (or N) and E, while it has no inductive suppression effect on differential mode interference between L and N. However, in practice, the coil is not perfectly wound. 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 flux generated cancels each other out, and the choke coil shows low impedance. Common mode noise currents (including ground loop nuisance currents, also known as longitudinal currents) flow through the two windings in the same direction, the flux generated 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, while for high-frequency common-mode noise presents a large impedance, so it can be used to inhibit common-mode current harassment.
Common Mode Inductors in Switching Power Supplies?
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 will be generated inside the coil isotropic magnetic field, which is the same direction. When there is a common mode current flowing through, due to the isotropic nature of the common mode current, it will generate a homogeneous magnetic field in the coil and increase the inductive resistance of the coil, which will make the coil behave as a high impedance and produce a strong damping effect, and then the common mode current will be attenuated, so as to achieve the purpose of suppressing the interference.
