Devboard and app note open straightforward route to mains EMC filtering


The user and their spectrum analyser are walked though a six step iterative process that should lead to a cost-effective filter that gets the job done.

Schurter-typical-mains-emc-filterAccording to the firm, the universal design allows the construction of a classic LC filter circuit allowing two X-capacitors of various sizes to be installed before and after the choke and a total of four Y-capacitors. The diagram shows one possible configuration.

Schurter-DKIH-1-emc-chokeThe choke in this case is always one from the 16 available in the firm’s single-phase DKIH-1 family.

Leakage resistors are provided to protect against electric shock.

Connection is made via two 6.3 x 0.8mm tabs, a 4mm hole or direct soldering of the cables to the large-surface pads. “It is recommended to make the earth connection as flat as possible using copper tape or wide copper strands,” warns Schurter, “The effect of the Y capacitors is considerably influenced by the connection.”


The app notes includes real-world considerations, like making sure you have measured the un-filtered equipment firts, and ends with a handy list of things to think about when transferring the hoprfully-now-complete filter design into a the final deisgn.