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Power Integrations Engineer Power Integrations ModeratorTest for EMI
Hello Everyone,
How can we test power supply by using simple equipement e.g, Oscilloscope.
I do not want to go for EMC qualification, but want to ensure that my power supply will not effect the neighbouring circuits and the systems running on the same Input line source.
Is there any tricky way?
Thanks
Peter
2 replies | Created on Apr 6, 2010 07:18 AM by petersmith
petersmith
One way is to buy a LISN and hook the output to a scope to see actual noise signal. Or you can look directly across secondary return to primary retrun with the scope probe reference to the secondary. It's also best to have a 50K resistor across the probe to filter out line frequency. Usually if the peak amplitude of this signal is below 0.5V you might be OK with EMI compliance. These techniques are better for daignostics and relaive assement of various implemented EMI suppression tries.
PI-Surak | 345 posts Thankyou very much for the reply. What is LISN. Can I get some recommendations to select it.
According to my understandings for the second technique you mentioned is:
First of all I should power the oscilloscope ( bandwidth ? ) via isolation transformer. then I should connect the GND of scope to output side GND, then connect the probe tip to primary side GND using 50K resistor in series.
Is it correct?
Peter
petersmith | 14 posts 