Two ways of switching power supply interference coupling
There are two ways of interference coupling in switch mode power supplies: conduction coupling and radiation coupling.
Conductive coupling is one of the main coupling pathways between disturbance sources and sensitive devices. Conductive coupling must have a complete circuit connection between the disturbance source and the sensitive device, and electromagnetic disturbance is transmitted from the disturbance source to the sensitive device along this connection circuit, generating electromagnetic interference. According to their coupling methods, they can be divided into circuit coupling, capacitive coupling, and inductive coupling. In switch mode power supplies, these three coupling modes coexist and are interrelated.
1. Circuit coupling
Circuit coupling is the most common and simplest form of conductive coupling. There are also the following types:
1) When a direct conductive coupling wire passes through an environment with disturbances, it picks up the disturbance energy and conducts it along the wire to the circuit, causing interference to the circuit.
2) Common impedance coupling refers to the phenomenon where two or more 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 that common impedance will affect the other circuit. This is known as common impedance coupling. The common impedance coupling disturbance is caused by factors such as power output impedance and common impedance of grounding wire.
2. Capacitive coupling
Capacitive coupling, also known as electrical coupling, refers to the phenomenon where the peak voltage generated by two circuits is a narrow pulse with a large amplitude, and parasitic capacitance exists between frequencies, causing the charge of one circuit to affect the other branch through the parasitic capacitance.
3. Inductive coupling
Inductive coupling, also known as magnetic coupling, occurs when there is mutual inductance between two circuits. When the interference source appears in the form of a power supply, the magnetic field generated by this current interferes with adjacent signals through mutual inductance coupling.
