Common-Mode Choke
In the Electromagnetic Compatibility (EMC) design of electronic equipment, common-mode interference is one of the most prevalent and challenging issues. Whether it’s surge interference from the power grid, signal coupling within internal circuits, or radiation from the external RF environment, most interference ultimately invades equipment in the form of common-mode signals, leading to signal distortion, false circuit triggering, or even equipment failure. Consequently, the common-mode choke, specifically designed to suppress common-mode interference, becomes a core weapon in solving electromagnetic interference problems. It is widely used in various electronic devices such as switching power supplies, frequency converters, communication equipment, and industrial controllers.
The common-mode choke is, in essence, a high-precision component for suppressing common-mode interference. Its core structural design revolves around “precisely distinguishing between common-mode and differential-mode signals”: Using a toroidal ferrite core with high permeability as the base, two coils with identical specifications (same wire gauge, material) and an exact, equal number of turns are wound symmetrically and in opposite directions on the core, forming a standard four-terminal device (two input terminals, two output terminals).
This precise filtering characteristic—”passing the desired signal while blocking the interference”—makes the common-mode choke an indispensable core component in EMC design. It can both suppress external common-mode interference from entering the equipment and block internally generated common-mode noise from radiating outward, thereby fortifying the anti-interference defense line for the stable operation of electronic equipment.
