How to Identify the Quality of Common Mode Inductors in Switching Power Supplies 1

The common-mode inductor in switching power supplies is an inductive component used to filter common-mode noise. The quality of the common-mode inductor significantly impacts the performance and interference resistance of switching power supplies. Below is a detailed introduction covering the fundamental principles of common-mode inductors, criteria for assessing their quality, and common faults.

1. The Basic Principle of Common Mode Inductors

The common-mode inductor refers to the L7915CV inductor component used in switching power supplies to filter out common-mode noise. In switching power supplies, high-frequency noise signals are often generated, which may propagate through the power lines to other devices, causing interference. The function of the common-mode inductor is to filter out these noise signals by utilizing its impedance characteristics against high-frequency noise, ensuring the purity of the power lines. diode

The working principle of a common-mode inductor is based on the self-inductance and mutual inductance characteristics of inductive components. When energized, the inductive component generates a magnetic field, which suppresses common-mode noise signals within the power line through magnetic coupling, preventing their propagation to other devices.

II. Criteria for Judging the Quality of Common Mode Inductors

1. Frequency Characteristics: The frequency characteristics of a common-mode inductor are a crucial indicator of its performance. A high-quality common-mode inductor should exhibit low impedance within the operating frequency range and possess strong common-mode rejection capability at the working frequency. The frequency characteristics can be tested using a network analyzer or an LRC meter.diode

2. Impedance characteristics: A good common-mode inductor should have low impedance, typically less than several dozen ohms. The lower the impedance, the more effectively the common-mode noise signal is filtered.