Two ways of interference coupling of switching power supply
Discussion on conduction coupling and radiation coupling of switching power supply in detail
There are two ways of interference coupling of switching power supply: conduction coupling and radiation coupling.
Conductive coupling is one of the main coupling ways between disturbance source and sensitive equipment. Conductive coupling must have a complete circuit connection between the disturbance source and the sensitive equipment, and electromagnetic disturbance transmits electromagnetic disturbance from the disturbance source to the sensitive equipment along this connection circuit, resulting in electromagnetic interference. According to its coupling mode, it can be divided into circuit coupling, capacitive coupling and inductive coupling. In switching power supply, these three coupling modes exist at the same time and are interrelated.
1. Circuit coupling
Circuit coupling is the most common and simple conductive coupling mode. There are the following types:
1) When the direct conductive coupling wire passes through an environment with disturbance, that is, the disturbance energy is picked up and conducted to the circuit along the wire, resulting in interference to the circuit.
2) Common impedance coupling Because more than two circuits have a common impedance, when the current of two circuits flows through a common impedance, the voltage formed by the current of one circuit on the common impedance will affect the other circuit, which is called common impedance coupling. The common impedance coupling disturbance is caused by the output impedance of power supply and the common impedance of ground wire.
2. Capacitive coupling
Capacitive coupling is also called electrical coupling. Because the peak voltage generated by two circuits is a narrow pulse with large amplitude, there is parasitic capacitance between the frequencies, so that the charge of one circuit affects the other branch through the parasitic capacitance.
3. Inductive coupling
Inductive coupling is also called magnetic coupling. When there is mutual inductance between two circuits, when the interference source appears in the form of power supply, the magnetic field generated by this current interferes with the adjacent signals through mutual inductance coupling.
