In recent years, a small common-mode inductor manufactured in China adopts high-frequency noise suppression strategy, common-mode choke coil structure, signal attenuation, small size, easy to use, has the advantages of good balance, easy to use, high quality and so on. What is the working principle of the patch common-mode inductance coil? The filter circuit of the patch common-mode inductance coil, La and Lb, is the common-mode inductance coil. The two coils are wound on the same core, and the turns and phases are the same (reverse winding). In this way, when the normal current in the circuit flows through the common-mode inductance, the current in the inductance coil wound in the same phase generates a reverse magnetic field and cancels each other. At this time, the normal signal current is mainly affected by the resistance of the coil (and a small amount of damping caused by leakage inductance); when the current of the patch common-mode inductance coil flows through the coil, it is due to the patch. The current of common-mode inductance coil has the same direction magnetic field in the coil, which will increase the inductance of the coil, make the coil show high impedance and produce strong damping effect, so as to attenuate the common-mode current and achieve the purpose of filtering.
In fact, La and C1, Lb and C2 constitute two sets of low-pass filters, which can control the common-mode EMI signal on the circuit at a very low level. The circuit can not only suppress the external EMI signal, but also attenuate the EMI signal generated by the circuit itself, which can effectively reduce the EMI interference intensity.
