common mode choke value

4 posts / 0 new

Hi, we have a 25W streetlight driver using LNK 419eg with spec 180-305V input and 50V/500mA output. We plan to switch from the existing  to LYT 4226e. We need your help to design the input EMI filter section with a Common mode choke. Shall we proceed with 47nF/X2 and 8.8mH CMC similar to DER 427? Kindly advice to fix the Choke inductance  value.

Thanks

SDM

 

Yes its a good starting value for the CMC. Since your power is lower than DER427, you can probably reduce the X-cap to 33nF or 22nF for better PF.

Hi,

   with guidance of DER427 we made a 25W street light driver with emi filter  CMC 8.8mH. What should be the correct value for L4 and L5 for 25w application? shall we use 1.5mH just like DER427? can we reduce L5 from the ckt?

Is there any advantage in surge protection when using CMC in the input filter instead of drum core inductors?

Thanks

SDM

Using 1.5 mH is fine since the output power of your application is not that different from DER-427. You may be able to reduce L5 if the conducted EMI results show enough margin.

The CMC is mainly for EMI. I don't see any advantage for surge, but if the DCR of the CMC you used is larger than the drum core, then it could lower the surge current.