Extending the Concept of Common Mode Noise: Single Mode - Mechanism of generation of common mode noise in switch mode power supplies

摘要

Electronic switching circuits are used for power conversion, data communication and other applications. According to the theory of Fourier Transform, in these circuits, the periodical change of the current/voltage produces harmonics in a wide frequency spectrum. The resultant currents of these harmonics are called conducted emission (CE), and are categorized classically as differential and common mode (DM, CM) currents - or noises. While the existence of differential/current is trivial, the concept of CM current, which implies that the currents in two different circuits are equal for the whole frequency spectrum, raises some questions about its credibility. CM current, as a reminder, is the current that circulates through the parasitic (capacitance) to the Chassis (Ground).