50uH LISN needed but not for EMC test

[Flyback]

Hi,
We wish to test our 24vin, 12vout 150W out Buck converter with the 50uH LISN in its input circuit so that we can check for input filter oscillations when the LISN is attached.
We wont actually be doing any pre-compliance EMC measurements at this point.

Would you say the attached will be ok for this?

 

[Tony Stewart]

What is the logic of having such a filter when a current sensor would be far more accurate? One never uses a LISN or Conducted Emissions this way for DCDC converters.

 

[Papabravo]

What is the logic of having such a filter when a current sensor would be far more accurate? One never uses a LISN or Conducted Emissions this way for DCDC converters.

I guess some people are hellbent on being innovative and using parts in ways they've never been used before.

 

[Flyback]

Thanks, the LISN is meant to be that impedance that imitates the worst case impedance of the installation....so if we use it, we stop the danger of input filter oscillation ever occurring if we manage to work with it.

ie, we get our DCDC working well with the LISN upstream, then we are good.

if we dont use the LISN, then we could be having storms ahead...input filter oscillation and instability.