Common mode Choke inductor

author: Magtop
09/10/2024
Power filter design involves both common mode and differential mode. The key component of a common mode filter is the common mode choke, which offers high inductance in a small size compared to differential mode chokes. A critical factor in designing common mode chokes is managing leakage inductance, typically around 0.5% to 4% of the common mode inductance. This error should be considered when optimizing choke performance.
  1. The Role of Leakage
    Leakage occurs when the coil windings are not tightly packed, allowing magnetic flux to escape. In common mode chokes, two opposing windings create a magnetic field close to zero. However, if the windings aren’t perfectly aligned, flux leakage occurs, introducing differential mode inductance. This leakage, if excessive, can lead to magnetic saturation of the core, reducing the effectiveness of the common mode inductance.
  2. Common Mode Chokes and Filter Design

In filter design, common mode and differential mode are not fully independent, as common mode chokes also offer differential mode inductance. Therefore, it’s important to address each mode sequentially when designing filters. Common mode noise should be filtered first, and then differential mode components can be managed using the leakage inductance. In low-power systems, the differential mode inductance of a common mode choke is often enough to reduce differential mode radiation without risking magnetic saturation from excessive inductance.

Back to list