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CMC choke and differential mode choke doubt

Posted by: george08 on Fri, 09/04/2020

1. I would like to know how to calculate CMC filter and DMC filter for LED drivers,?
2. I read in one article that CMC choke leakage inductance can act as differential mode choke, Can I avoid differential mode choke by considering this theory?

3. Will lead the circuit get damage, if we didn't use the exact CMC filter & differential filter?, What happens if there is no CMC and Differetial mode choke in the LED driver?


Submitted by PI-Zek on Mon, 09/07/2020

1. The values usually depend on the application and overall parameters of your LED driver. You can check the application note of the product for the initial values or recommended design of the input filters (CMC, DMC, etc.). There are also layout recommendations in this app note for effective filtering together with the EMI filter capacitors.

You can also check references or design examples of the product you consider for your project to have a guide on the initial values of the filters.

2. You may eliminate the differential mode with CMC only but this may increase the EMI noise of your design.

3. Without these filters, as mentioned in #2, this may lead to increased in EMI noise. You may check other references about EMI in switching mode power supply.