Switching power supplies have two types of interference coupling
Switching power supply interference coupling has two ways: conduction coupling way, radiation coupling way.
Conducted coupling is one of the main coupling paths between the source and sensitive equipment. Conducted coupling must be in the nuisance source and sensitive equipment between the existence of a complete circuit connection, electromagnetic harassment along the connection circuit from the nuisance source to transmit electromagnetic harassment to sensitive equipment, electromagnetic interference. According to its coupling mode can be divided into circuit coupling, capacitive coupling and inductive coupling. In the switching power supply, these three kinds of coupling mode exists at the same time, interconnected.
1. Circuit coupling
Circuit coupling is the most common, the simplest way of conduction coupling. There are several types:
1) direct conductive coupling wire through the environment of the existence of harassment, that is, pick up the harassment energy and conduct along the wire to the circuit and cause interference to the circuit.
2) common impedance coupling due to more than two circuits have a common impedance, when the current of two circuits flow through a common impedance, a circuit of the current in the common impedance of the voltage formed on the circuit will affect the other circuit, which is the common impedance coupling. Formation of common impedance coupling nuisance of the power supply output impedance, the common impedance of the earth wire, etc..
2. Capacitive coupling
Capacitive coupling is also known as electrical coupling, due to the two circuits of the spike voltage is a large amplitude of the narrow pulse, the presence of parasitic capacitance between the frequencies, so that a circuit charge through the parasitic capacitance affects another branch.
3. Inductive coupling
Inductive coupling is also known as magnetic coupling, there is mutual inductance between two circuits, when the interference source is in the form of power supply, the magnetic field generated by the current through the mutual inductive coupling of the neighbouring signals to form interference.
