Classification of switching power supply EMI transmission channels
(i) Transmission channels for conducted interference
(1) Capacitive coupling
(2) Inductive coupling
(3) Resistive coupling
a. Resistive conductive coupling generated by the internal resistance of the public power supply
b. Resistive conductive coupling generated by the public ground impedance
c. Resistive conductive coupling generated by the common line impedance
(ii) Transmission channel of radiation interference
(1) In the switching power supply, the components and wires that can constitute a source of radiated interference can be assumed to be antennas, so as to make use of the electric and magnetic dipole theory to carry out analysis; diodes, capacitors, power switching tubes can be assumed to be electric dipoles, and inductive coils can be assumed to be magnetic dipoles;
(2) When there is no shielding body, electric dipole, magnetic dipole, the electromagnetic wave generated by the transmission channel for the air (can be assumed to be free space);
(3) When there is a shielding body, the gaps and holes of the shielding body are considered, and the leakage field is analysed and processed according to the mathematical model of the leakage field.
