Conducted EMI measurements with EMIfix LISN
When testing conducted EMI on a power supply including a PFC boost converter, an auxiliary Flyback converter, a galvanic isolated LLC converter and a motor inverter it sometimes get complicated to identify the different noise sources.
The old trick is just to add an excessive large X capacitor on the output of the LISN network.
This reduces and helps to identify the differential mode part of the noise.
Another solution could be to use an EMIfix LISN network.
EMIfix is the perfect LISN network for splitting and measuring common mode and difference mode noise individually.
For more information about the EMIfix LISN network visit the web side of the EMIfix inventor Runo Nielsen on www.runonielsen.dk
Total EMI
The total EMI is a combination of both Common mode and differential mode noise.When looking at the complete noise spectrum it is sometimes difficult to identify the individual noise sources.With…
Common mode
Common mode noise is generated between Chassis and Primary.This is typically noise coupled in the transformer between the primary and secondary winding.It may also be noise coupled from the drain…
Differential mode
Differential noise is typically generated by the fast switch transients.In an AC/DC switch mode power supply the primary source for the differential noise is typically the PFC switch components.Capacitors must…