How to determine the common-mode inductance of a switching power supply by its resistance value 1

The common-mode inductor is a key component in switching power supplies designed to suppress common-mode noise. Common-mode noise is generated by switching devices within the power supply, which creates interference on the power lines with identical amplitude and phase. This interference may disrupt the normal operation of other electronic devices or propagate through the power lines to affect other equipment.diode

Common-mode inductors typically consist of two or more windings, which are wound around the same magnetic core and connected in series on the power line. Under normal operating conditions, the current through each winding should be equal and opposite in direction, causing the magnetic fields generated in the core to cancel each other out, resulting in minimal impact on differential-mode signals. However, for common-mode signals, since the current direction is the same in both windings, the generated magnetic fields do not cancel, and the common-mode inductor strongly opposes these signals.

The resistance value of a common-mode inductor is not the primary parameter for evaluating its performance, as the inductor primarily functions through mutual inductance via magnetic fields rather than by dissipating energy through resistance. However, the DC resistance (DCR) of a common-mode inductor is a critical parameter, as it determines the power loss generated during operation. A lower DCR value indicates reduced power loss when current flows through the inductor, which is beneficial for improving power supply efficiency.diode