Hi all,

I am designing a simple flyback converter for a led light. I don't know how to design/ select the LC filter, can some one help?

I have attached the schematic for reference.

Thanks.

 

You mean LC filter in the mains side?? In the secondary Your circuit has none.
There the main thing is to compass a standard. For <75W is one standard and for >75W is another one. Separate for computer hardware, separate for housekeeping appliances and separate for factory environment. Thus, if the goal is mass production, those standards must to be examined and observed.
Another story is if that is just innocent homebrew design for own joy. Then there is only one criterion - the neighbours must not write a claims. Thus, put the ANY coil with ANY capacitors looking right and forget it. The only control ought be made is on mains voltage. As the mains inner ESR for 50 Hz is ca nanoOhms but for any non-50 Hz are ca kiloOhms, but for RF even 100K-1MOhm, then even small impact may wane very slowly, thus polluting a whole streetbloke. Just use the oscilloscope, and if the problem is easy to see, add the second cascade. Generally there ought stay as filter for both-wire simultaneous noise as the filter for one-wire only noise. One has two coils in both wires what are separate, other has those both inductively tight coupled. One has capacitors connected between wires to virtual zero, another has connected to real ground. There are plenty of tutorials in the Google about right circuitry, as an example www.researchgate.net/publication/251992627_Design_of_EMI_filters_for_DC-DC_converter
Dont worry about LISN, that is detail only for evaluating measurement needs, simulating the "standard mains network".

 

Hi,

Thanks for the reply. That was helpful.

Yes LC filter in the Mains side. Also can you help designing the LC filter after Bridge rectifier?. On the schematic I attached, Ref. designator is L1 and C2.

 

Can some one help?

 

Your circuit is all wrong, there are too many wasted components, i don't see the point in the Tl431, D5, Zd1 and the resistors, the Vs pin should be used as voltage regulation on the mirror winding Vdd.

Look at the datasheet for better results.

 

What is the intent here? It looks like a passive valley-fill power factor correction "filter" [edit - previous part that has been greyed is probably wrong - see #8] followed by a no-feedback constant current driver.

I also don't understand what the TL431 is supposed to be doing. Everything else looks generally OK but I haven't looked at it in detail.

 

I looked at the datasheet for the controller. It does power factor correction. [Edit - probably erroneous statement removed]

I also wasn't paying attention to the input parts. It would be very unusual to use three MOVs like that.

 

Looked at it again again:
I should have looked more closely the first time. What I glanced at and thought might be a valley-fill passive power factor correction network actually looks like it is probably to facilitate phase angle controlled dimming with standard triac dimmers. This type of dimmer sometimes will not work reliably with LED drivers because the minimum hold current requirement for the triac can't be achieved during the brief trigger pulse from an RC-diac trigger. I'm not adequately familiar with the type of circuit used to be sure, so I need to do some homework.