Cosel is one of the world's leading power supply manufacturers offering
high-quality, ultra small size AC-DC power supplies,
DC-DC converters of the state-of-the-art technologies, and effective and
easy-to-use noise filters.

1. Souces
 Some noise will occur from the switching power supply because it operates by controlling the switching high voltage. Their main sources are shown in Fig.1.1

1. Switching transistor ----- (a)
2. Output rectifier ----- (b)
3. Output transformer ----- (c)

2. Pathways
 The noises occurring from power supply are classified into several kinds as shown below based on the pathways. The pathways of noise are shown in Fig.1.1

1. Line conduction: Conducted from input terminal of power supply
• Differential-mode noise: Occurring between the AC input lines ----- j
• Common-mode noise: Occurring between the AC input line and FG ----- k
2. Output noise: Conducted from output terminals of power supply
• Differential-mode noise: Occurring between output lines ----- l
• Common-mode noise: Occurring between the output line and FG ----- m
3. Radiated emission: Radiating from power supply or input/output line directly ----- n
   (Radiation noise)